US 20120070575A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2012/0070575 A1 Hagerty et al. (43) Pub. Date: Mar. 22, 2012

(54) METHODS FOR APPLYING SOLUTION Related U.S. Application Data CATALYSTS TO REACTOR SURFACES (62) Division of application No. 12/529,580, ?led on Mar. (75) Inventors: Robert O. Hagerty, Wyckoff, NJ 4, 2010, noW Pat. No. 8,088,870, ?led as application No. PCT/US2008/002317 on Feb. 21, 2008. (US); Kevin B. Stavens, Seabrook, TX (US); Randall B. Laird, (60) Provisional application No. 60/905,274, ?led on Mar. Pasadena, TX (US); Zerong Lin, 6, 2007, provisional application No. 61/002,159, ?led KingWood, TX (US); Michael E. on Nov. 7, 2007. Muhle, KingWood, TX (US); Agapios K. Agapiou, Humble, TX Publication Classi?cation (US); David M. GloWczWski, (51) Int. Cl. BaytoWn, TX (US); Fathi D. B05D 7/22 (2006.01) Hussein, Cross Lanes, WV (US); B05D 3/10 (2006.01) Gary D. Mohr, Houston, TX (US); B05D 3/04 (2006.01) Ted A. Powell, La Porte, TX (US); B05D 1/02 (2006.01) Michael E. Sieloff, Houston, TX (52) U.S. Cl...... 427/236; 427/230 (US); Edward F. Smith, KingWood, TX (US); Keith W. (57) ABSTRACT Trapp, Baton Rouge, LA (US) A method for treating at least one interior surface (for example, a bed Wall) of a ?uidized bed polymerization reactor (73) Assignee: UNIVATION TECHNOLOGIES, system, including by applying a solution catalyst (preferably LLC, Houston, TX (US) at least substantially uniformly and in liquid form) to each surface, and optionally (Where a catalyst component of the (21) Appl. No.: 13/302,633 solution catalyst comprises at least one chromium containing compound) oxidizing at least some of the applied chromium (22) Filed: Nov. 22, 2011 containing compound in a controlled manner.

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Chromocene Cycle Gas Solution Feed Flow Patent Application Publication Mar. 22, 2012 Sheet 1 0f 4 US 2012/0070575 A1

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Chromocene Solution Feed

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METHODS FOR APPLYING SOLUTION covered With granular resin that has fused to the core. The CATALYSTS TO REACTOR SURFACES edges of the sheets often have a hairy appearance from strands of fused polymer. Sheeting rapidly plugs product discharge CROSS REFERENCE TO RELATED systems and/or disrupts ?uidization, leading to the need for APPLICATIONS costly and time-consuming shutdoWns. [0001] The application is a divisional application of US. [0008] Gas phase processes have been found to be particu application Ser. No. 12/529,580, Which is a National Stage larly prone to sheeting When producing polymers using Zie application under 35 U.S.C. §371 of International Applica gler-Natta catalysts, particularly Type III and Type IV Zie tion No. PCT/US2008/002317, ?led Feb. 21, 2008, that gler-Natta catalysts, certain bimodal catalyst systems, and claims the bene?t of US. Provisional Application No. catalyst systems containing metallocene catalyst compounds. 60/905,274, ?led on Mar. 6, 2007, and US. Provisional While metallocene catalysts yield polymers With unique Application No. 61/002,159, ?led on Nov. 7, 2007, the dis characteristics, they also present neW challenges relative to closures of Which are incorporated by reference in their traditional polymerization systems, in particular, the control entirety. of reactor sheeting. [0009] A correlation exists betWeen reactor sheeting and FIELD OF THE INVENTION the presence of excess static charges, either positive or nega tive, in the reactor during polymerization (see, for example, [0002] The invention generally relates to methods and US. Pat. Nos. 4,803,251 and 5,391,657). This is evidenced by apparatuses for treating surfaces (e.g., bed Walls) of gas phase sudden changes in static levels folloWed closely by deviation polymerization reactors by applying solution catalysts in temperature at the reactor Wall. When the static charge thereto to prepare the surfaces for subsequent formation of a levels on the catalyst and resin particles exceed critical levels, polymer coating thereon. In typical embodiments, the reac electrostatic forces drive the particles to the grounded metal tors are gas phase polymerization reactors for use in polymer Walls of the reactor. The residency of these particles on the izing at least one ole?n in the presence of at least one catalyst reactor Wall facilitates melting due to elevated temperatures or catalyst system. and particle fusion. FolloWing this, disruption in ?uidization patterns is generally evident, such as, for example, catalyst BACKGROUND feed interruption, plugging of the product discharge system, [0003] The expression “interior surface” of a ?uidized bed and the occurrence of fused agglomerates (sheets) in the polymerization reactor system (or reactor) herein denotes a product. surface of the reactor system (or reactor) that is exposed to a [0010] It has been found that the presence of polymer coat reactant, recycle gas, and/ or polymerization product during ing on the bed Wall of a gas phase (?uidized bed) polymer performance of a polymerization reaction in the reactor sys ization reactor is desirable for reducing the tendency of the tem (or reactor). reactor to form sheets. Without being bound by theory, it is [0004] The expression “bed Wall” is used herein to denote believed that the presence of certain reactor Wall coatings the portion or portions of the interior surfaces of a ?uidized (e.g., polymer coatings) inhibits the triboelectric charge bed gas phase polymerization reactor system (or reactor) that transfer that Would otherWise occur as the resin in the ?uid is or are in contact With the ?uidized bed during normal ized bed rubs against the metal reactor Walls. Without being polymerization operation of the reactor system (or reactor). bound by theory, it is further believed that inhibiting the For example, typical embodiments of the invention pertain to triboelectric of charge transfer has the effect of minimizing treating the bed Wall of a ?uidized bed polymerization reactor (or reducing) the accumulation of electrostatic charge on the preliminary to forming a polymer coating on the treated bed resin. It is Well knoWn the accumulation of electrostatic Wall. The treatment applies a catalyst (in solution) to the bed charge on the resin can contribute to the formation of sheets in Wall so that the polymer coating can be formed by a special the reactor. polymerization reaction in the presence of the applied cata [0011] Fluidized bed polymerization reactors are often lyst. The special polymerization reaction is not the normal constructed of carbon steel, typically rated for operation at polymerization reaction to be performed in the reactor after pressures up to about 30 bars (about 3.1 megapascals), and the polymer coating has been formed. have interior surfaces composed of carbon steel. The normal [0005] The expression “solution catalyst” is used herein to appearance of the interior surfaces is that of plain, uncoated denote a solution of at least one catalyst in at least one solvent. metal. HoWever, a thin coating of polymer alWays (or almost For example, chromocene (or another polymerization cata alWays) forms on the bed Wall of a ?uidized bed polymeriza lyst) dissolved in an aromatic solvent, such as, toluene (or tion reactor that has been in service. The coating is usually another solvent) is a solution catalyst. thin and relatively clear so that its presence is dif?cult to [0006] The term “comprises” is used herein to denote “is or detect visually, but its presence can be detected With an Eddy includes.” current-type meter. The coating is normally composed of [0007] Gas phase polymerization of monomers, for relatively loW MW (molecular Weight) polymer and has a example, ole?n monomers, may be prone to forming “sheets” thickness of 1 to 20 mils (25 to 500 microns). Even though it on the Walls of the reactor vessel, particularly on certain is very thin, the coating has a signi?cant effect on the oper catalyst types. Sheeting refers to the adherence of fused resin ability of the reactor through its effect on the static charging and resin particles to the Walls or the dome of a reactor. The characteristics of the ?uid bed. sheets vary Widely in size. Sheets may be 1A to 1/2 inch thick [0012] It is generally recognized that during ?uid bed poly and may be from a feW inches to several feet long. They may merization, ?uid beds of polymer and other materials become have a Width of 3 inches to more than 18 inches. The sheets charged by frictional contact With the reactor Wall through a may have a core composed of fused polymer, Which is ori process knoWn as the triboelectric effect. The charging ented in the long direction of the sheets, and their surfaces are mechanism depends on tWo factors: the nature of the materi US 2012/0070575 A1 Mar. 22, 2012

als involved, and the degree of contact. The basic driving it is hypothesized that the deterioration in bed Wall coatings force for transfer of charge is the difference in electrical may involve an oxidation of the polymer coating. characteristics of the tWo materials that contact each other. If [0018] Although, in most cases, it is not certain What is the there Were no difference betWeen the materials involved (e. g., exact mechanism or mechanisms that cause the deterioration, if the tWo materials contacting each other Were identical, for it is Well knoWn a polymer coating on the bed Wall can be example, if both Were carbon steel) no (or minimal) charge deteriorated or contaminated over time, and this can have a transfer Would take place. In general, larger amounts of major effect on operability of the reactor. charge are transferred When the tWo materials in frictional [0019] In practice, the reactor static baseline does not contact are more different in their electrical characteristics change suddenly. Rather, coating contamination or deterio (i.e., When they are far apart on the triboelectric series). ration usually occurs over a period of time. As this happens, static activity and sheeting problems gradually develop and [0013] In gas phase polymerization reactors, the ?uid bed appear ?rst during the production of certain resin products. can become highly charged through the frictional contact of These products, usually characterized as having higher tWo dissimilar materials, typically frictional contact betWeen molecular Weights and higher densities, are referred to as the the polymer resin in the bed and the carbon steel of the bed sensitive reactor grades. With a relatively mild degree of Wall. It is knoWn that a good quality polymer coating on the reactor Wall contamination, static and sheeting problems are bed Wall acts to reduce the charging substantially, and thereby initially seen With the highest MW products and some of the reduces the tendency for sheets to form on the bed Wall. Some higher density grades. As the static baseline deteriorates fur believe that the polymer coating is more similar in nature to ther (e.g., as the Wall coating becomes more contaminated) the polymer in the ?uid bed (compared to the carbon steel), static and sheeting problems begin to occur With more and thus reducing the driving force for charge transfer in the more products. The sensitivity of sheeting risk to different triboelectric process. Whatever the reason, it is clear that the resin grades appears only With a contaminated or deteriorated coating on the bed Wall (and possibly also other interior bed Wall coating. If the coating is in good condition, static surfaces of the reactor system) has a signi?cant effect on the remains near zero for all products. static charging characteristics of the ?uid bed. [0020] TWo types of reactor system retreatments, for [0014] When the polymer coating on the bed Wall is in removal of a bad (deteriorated or contaminated) bed Wall “good” condition, as indicated by its charge decay character coating and replacement With a neW polymer coating, have istics, a ?uidized bed reactor system can be operated for been used commercially. Both retreatment methods involve extended periods of time (months or years) Without excessive preparation of the bed Wall (typically by removal of an exist static and Without operational problems due to sheeting. A ing bad polymer coating) and the in situ creation of a neW reactor in this state is said to have a good static baseline, is polymer coating on the Wall. These conventional techniques relatively insensitive to the type of product being produced have proven effective to some degree and With some catalyst (e. g., its molecular Weight “MW” and density), and can typi systems. cally be operated to produce the full range of polyethylene [0021] One type of conventional retreatment method is (PE) resin grades Without generating excessive levels of static knoWn as chromocene treatment. To perform such retreat charge or sheeting. ment, the bad (e. g., contaminated) polymer coating is [0015] HoWever, When the bed Wall coating is in “poor” removed from the bed Wall by grit blasting. The reactor is then condition, a considerable amount of static activity can sealed and purged With nitrogen to remove oxygen and mois develop in the ?uid bed, Which often leads to sheeting. A ture. A solution catalyst (chromocene in solution) is then reactor in this state is said to be “sensitive” because the static introduced into the reactor and the catalyst deposits on the charging characteristics become highly sensitive to the MW reactor Wall. The catalyst on reactor Wall is then activated by and density of the product being produced. controlled oxidation, purging, and then introducing ethylene [0016] The factors that cause the polymer coating on a bed and an alkyl such as tri-ethyl aluminum to form a neW poly Wall to change from good to bad have been investigated from mer resin coating (preferably a high molecular Weight poly several different aspects. For example, it is knoWn that the mer coating) on the bed Wall that may be effective in reducing coating can deteriorate during normal polymerization opera charge buildup on the reactor bed Wall and impeding sheet tion and maintenance by exposure to aluminum alkyls com formation. The solution catalyst may include any of various pounds folloWed by repeated or prolonged exposure to Water chromium compounds (e. g., bis-cyclopentadienyl chromium and air When the reactor is opened for maintenance. Alumi and other chromocenes). U.S. Pat. Nos. 4,532,311, 4,792, num alkyl compounds that are knoWn to cause deterioration 592, and 4,876,320, for example, disclose methods of reduc include methyl and ethyl alumoxane, triethyl aluminum and ing sheeting in a ?uidized bed reactor by introducing a chro trimethyl aluminum. The alumoxanes are commonly used in mium-containing compound into the reactor prior to a special metallocene polymerization and include bound trimethyl alu polymerization reaction (catalyzed by the chromium) to form minum. Trimethyl and triethyl aluminum are commonly the high molecular Weight coating on the bed Wall of the employed as cocatalyst in Ziegler-Natta polymerization. reactor. Water reactions With organoaluminum are the origin of the [0022] Another type of conventional reactor retreatment deterioration. It has been experimentally con?rmed that (for restoring a previously formed polymer coating) is knoWn u-oxo compounds are formed Which quickly deactivate to as hydroblasting. In this method, a contaminated or damaged form a particular hydrated species of alumina calledboehmite polymer coating is removed from the bed Wall With a high and represented chemically by Al(O)OH. pressure Water jet. The reactor is then dried and purged With [0017] It is also suspected that prolonged exposure to impu nitrogen and restarted in the normal fashion, but With a rela rities can lead to Wall ?lm degradation. These impurities tively high concentration of hydrogen so as to produce (by include C6 oxides such as hexanol, and 1,2 hexanediol, both polymerization) a high melt index material (the melt index or of Which are reaction products of l -hexene and oxygen. Thus, “MI” is typically 10 or more as measured by the 12 method). US 2012/0070575 A1 Mar. 22, 2012

The high melt index, loW MW resin produced readily deposits sity, high molecular Weight (very loW melt index) polymer. on the reactor bed Wall, producing a neW polymer coating Such a coating having high density, high molecular Weight, Which reduces the risk of sheeting during subsequent normal and loW melt index, is typically highly resistant to abrasion by polymerization operation of the reactor. the softer polymer typically present in the ?uid bed during [0023] We next describe typical conventional chromocene normal polymerization operation. retreatment methods in more detail. After the bed Wall is [0027] The polymer coating formed on the bed Wall of a cleaned (e.g., by grit blasting) and the reactor is sealed and ?uidized bed polymerization reactor by conventional chro purged, such methods include the step of injecting a chro mocene retreatment typically does not have uniform thick mium-containing compound in solution (e.g., chromocene ness throughout the bed Wall. Without being bound by theory, dissolved in toluene) into the reactor and circulating the the inventors believe that the conventional methods do not injected compound so that some of the catalyst is deposited on provide a uniform polymer coating on the bed Wall because the reactor’s bed Wall. The deposited catalyst is then oxidized, the chromium containing compound is not deposited uni and the reactor is then opened for cleaning. The next step in formly on the bed Wall. this retreatment method is to purge the reactor With nitrogen [0028] Although conventional chromocene retreatment and then activate the deposited catalyst by introducing ethyl methods can form effective and reliable polymer coatings on ene and an alkyl to the reactor. The chromium-containing the bed Walls of ?uidized bed polymerization reactors, they compound (e.g., chromocene) acts as a catalyst to polymerize do not reliably form such effective and reliable coatings. the ethylene in the presence of alkyl to form the coating. Often, such conventional methods fail to form effective and [0024] In conventional chromocene treatment methods, it reliable polymer coatings and instead form little or no poly is desired that the chromocene-containing solution (e.g., mer on a bed Wall (or on portions of a bed Wall). Without an chromocene dissolved in toluene) Will contact the reactor’s effective polymer coating, a reactor that has undergone such bed Wall to deposit the chromocene on the bed wall. It is failed treatment is sensitive to static charging and sheeting, generally believed that the concentration of chromocene in particularly during polymerization reactions using metal the solvent is not critical to the process, and this concentration locene catalysts. is typically selected to assure that the chromocene is com [0029] The inventors have recognized that conventional pletely dissolved in the solvent. A solution containing about 5 application of chromocene solution (or other solution cata to 8 percent by Weight of chromocene in toluene is commonly lyst) during conventional retreatment methods alloWs the used. solution catalyst to evaporate (or undergo sublimation) before [0025] Referring to FIG. 1, conventional deposition of contacting the bed Wall, so that the catalyst is not applied to the bed Wall in the form of liquid droplets. This prevents the chromocene on the interior surfaces of a gas phase polymer ization reactor 4 is typically done by injecting a chromocene conventional methods from reliably forming effective, reli able polymer coatings on the bed Wall. containing solution through a feed tube at each one of a set of catalyst injection points 2. One such feed tube is shoWn at [0030] What is needed is a more reliable method for form point 2 in FIG. 1. At each injection point, the solution may be ing effective and reliable polymer coatings on the bed Walls injected through a single straight tube or through a tube With and other interior surfaces of ?uidized bed polymerization a spray nozzle at its end. An inert gas, such as nitrogen, is reactors. circulated through reactor 4 by cycle compressor 6 While the [0031] Fouling problems often result from the performance solution is sloWly injected over a period of time (typically at of methods that include steps of applying solution catalyst to interior surfaces of a polymerization reactor system and then least one to three hours, and sometimes as long as eight performing a polymerization reaction (catalyzed by the hours). The reactor system then circulates the mixture for a relatively long time (e.g., about tWenty hours). It has been applied catalyst) to form a polymer coating on each surface. found that the level of chromium deposited on the bed Wall by Speci?cally, excessive amounts of the polymer coating mate such a conventional method is typically signi?cantly loWer rial can foul components of the system. Some reactor system than the level of chromium deposited in the bottom head and components (e.g., distributor plates and compressor bases) are particularly vulnerable to this type of fouling. It Would be on the bottom of the reactor’s distributor plate 1 0. The method preferentially deposits the chromium on distributor plate 10 desirable if such methods could be modi?ed to reduce or and in various parts of the reactor system other than the bed eliminate such fouling of reactor system components With Wall, such as in cycle compressor 6 and cycle cooler 12. The polymer coating material. chromium deposited on distributor plate 1 0 (and other parts of the reactor system other than the bed Wall) by the prior art SUMMARY method typically must be cleaned off before reacting the [0032] In a class of embodiments, the invention is a method chromium to form the desired polymer coating. for treating at least one interior surface (e.g., a bed Wall) of a [0026] The polymer coating formed on the bed Wall of a ?uidized bed polymerization reactor system, including a step ?uidized bed polymerization reactor after chromocene treat of applying a solution catalyst at least substantially uniformly ment is intended to function as an insulating layer that reduces and in liquid form (e.g., in the form of liquid droplets of the static charging in the reactor system, thereby reducing the solution catalyst) to each said surface. Typically, the applied potential for sheeting during subsequent normal polymeriza solution catalyst is dried (or alloWed to dry) to leave a dry tion reactions. Although typically thin (e.g., about 1 to about coating of catalyst on each surface and a polymerization 20 mils, or 0.025 to 0.50 millimeters, Where one “mil” reaction (catalyzed by the catalyst) is then performed to form denotes 0.001 inches), such a polymer coating can be effec on each surface a polymer coating that reliably functions as an tive in reducing static charging and is typically also durable. insulating layer that reduces static charging in the reactor Often, a typically thin polymer coating of this type has a system (and thereby reduces the potential for sheeting) during service life of at least four years before another retreatment is subsequent polymerization reactions in the reactor system. required, if (as is typical) the coating consists of a high den The best drying temperature and other best parameters for US 2012/0070575 A1 Mar. 22, 2012

drying the solvent component of the solution catalyst (e.g., applied conventionally (as a vapor). This smaller crystal may toluene) after applying the solution catalyst in liquid form in be one of several factors contributing to the observed result accordance With the invention Will depend on the particular that catalyst applied in accordance With the invention is more situation. Any of a broad range of drying parameters (e.g., effective in catalyzing subsequent polymer coating-forming drying temperature) may be best depending on the particular polymerization reactions than if applied conventionally. situation. [0037] TWo classes of embodiments of the inventive [0033] In some embodiments, the interior surface to be method are improved versions of conventional solution cata treated is the bed Wall of the reactor system. Typically, the lyst application methods. Each includes the step of applying reactor includes a distributor plate and a recycle line, and the solution catalyst in liquid form to the bed Wall of a polymer at least one interior surface to be treated is or includes at least ization reactor system (and optionally also at least one other one of the distributor plate, the recycle line, and the bed Wall interior surface of the reactor system, e.g., a distributor plate of the reactor system. In preferred embodiments, liquid drop and/or recycle line). In both classes, the applied solution lets of the solution catalyst are applied to each interior surface catalyst may be a solution of chromocene in an aromatic (on Which the polymer coating is to be formed) to coat each solvent, such as, toluene (e.g., a 5 to 8 Wt. solution of chro such surface at least substantially uniformly With liquid solu mocene in toluene). In the conventional methods, the intro tion catalyst before the applied solution catalyst evaporates or duced solution catalyst vaporizes prior to contact With most undergoes sublimation. sections of the bed Wall. Thus, the conventional methods [0034] In a class of embodiments, the catalyst component apply the catalyst to the bed Wall by vapor deposition in of the solution catalyst is or includes a chromium containing contrast to liquid deposition in accordance With the noted compound (“CCC”). In some such embodiments, the CCC is embodiments of the invention. chromocene. In some embodiments (including some in Which [0038] In one of the noted classes of embodiments, the the solution catalyst includes chromocene), the solvent com solution catalyst (e.g., chromocene solution) is injected ponent of the solution catalyst is toluene. In other embodi through an inlet in the side of a reactor that includes inert gas ments, the solvent component is benzene, isopentane, hex and is preferably empty of polymer. In some preferred ane, or another solvent suitable for the particular application embodiments in this class, the reactor contains only nitrogen (including the particular catalyst to be applied and method of and the solution catalyst is injected through a feed tube that dispersion to be employed). A polar solvent (e.g., Water) is extends through the side of the reactor (e. g., tube 2 of FIG. 1). unacceptable for use as the solvent When the catalyst is chro In other preferred embodiments, liquid solution catalyst is mocene. In a class of preferred embodiments in Which the introduced into the reactor system by being injected into the catalyst component is a CCC, the polymer coating formed (by reactor’s gas recycle line (e. g., tubing 5 of FIG. 3). Due to the a polymerization reaction catalyzed by the catalyst) is poly small cross-sectional area of the recycle line (relative to the ethylene. In general, the solvent should be inert and the solu cross-sectional area of the reactor vessel), injection of the tion catalyst should be introduced into an inert gaseous envi solution catalyst directly into the recycle line (While the ronment in the reactor system so that the catalyst does not recycle gas stream ?oWs through the recycle line) typically react until after it has been applied to each relevant surface results in more effective distribution and more uniform coat and the desired polymer coating-forming polymerization has ing of the solution catalyst on each surface of the reactor commenced. Typically, the solvent functions merely to carry system to be treated (including the bed Wall, and typically the catalyst and to aid in the catalyst’s dispersal Within the also the distributor plate and recycle line) than if the liquid reactor and application (in liquid form) to the bed Wall. solution catalyst Were injected directly into the reactor vessel [0035] Application of solution catalyst in liquid form to an at a location aWay from the recycle line’s outlet (from Which interior surface of a reactor system in accordance With the the recycle gas stream ?oWs into the reactor vessel). In con invention can result in formation of a thicker coating of poly ventional methods in Which solution catalyst is injected mer on the surface (during a subsequent polymerization reac directly into a reactor vessel through a feed tube in the side of tion catalyzed by the applied catalyst) than if the solution the vessel, the solution catalyst runs doWn the side of the catalyst Were alloWed to evaporate or sublimate before appli reactor Wall and onto the distributor plate Where it vaporizes cation. Increased thickness of the polymer coating is expected (by liquid evaporation and/or sublimation) before reaching to make the coating more effective in minimizing static charg most sections of the reactor Wall, and thus the catalyst con ing of the system during polymerization operation after for tacts most sections of the bed Wall as a vapor rather than a mation of the coating (“normal” polymerization operation). liquid. In accordance With the invention, solution catalyst is More importantly, application of the catalyst in liquid form in injected under conditions such that at least a substantial accordance With preferred embodiments of the invention amount of the solution neither vaporizes nor sublimates increases the applied catalyst’s reactivity during the subse before contacting the bed Wall (and optionally also before quent process of forming a polymer coating on each surface to contacting at least one other interior surface of the reactor be coated, thus reducing the risk that a polymer coating of system to be coated With a polymer coating, e.g., a distributor insuf?cient thickness Will be formed on at least some areas of plate surface and/ or recycle line surface), and such that liquid each surface to be coated. Application of solution catalyst in solution catalyst contacts the bed Wall at least substantially liquid form to reactor surfaces in accordance With preferred uniformly over the entire bed Wall (and optionally also at least embodiments of the invention is expected to alloW more reli substantially uniformly contacts each other surface to be able formation of effective and reliable polymer coatings on coated With a polymer coating). Preferably, after liquid solu the surfaces and to reduce the likelihood of failed attempts to tion catalyst has contacted the bed Wall suf?ciently uni form effective and reliable polymer coatings. formly, the reactor is vented to remove at least some (e.g., [0036] It is suspected that chromocene catalyst applied in most or all) of the solvent component (typically toluene) of liquid form to a reactor surface in accordance With the inven the solution catalyst that remains (e.g., remains in liquid tion has smaller crystal structure than if the catalyst Were form) in the system. The best parameters (including reactor US 2012/0070575 A1 Mar. 22, 2012

temperature) for removing (Which may include drying) the least substantially uniformly in liquid form on the bed Wall solvent after the application of liquid solution catalyst Will (and optionally also each other surface to be coated With a depend on the particular situation. polymer coating, e. g., the recycle line and distributor plate). [0039] In some embodiments of the inventive method (e.g., In conventional methods in Which solution catalyst is sprayed in some embodiments in Which the catalyst component of the into a reactor in the form of small droplets, the solvent (e. g., applied solution catalyst is chromocene or another CCC), toluene) evaporates quickly (typically Within a feW seconds) after application of solution catalyst and subsequent removal in the reactor to produce a dry poWder of catalyst (e.g., chro of a su?icient amount of the solvent, oxygen is introduced mocene crystals). This catalyst poWder is believed to deposit into the system to oxidiZe the catalyst that has been deposited on metal surfaces of the reactor by a tWo-step process of on the bed Wall and optionally on each other surface to receive sublimation (from the solid state to a vapor) and subsequent a polymer coating, and excess oxygen is then purged from the adsorption on the metal Walls. In accordance With the inven system (e.g., With high purity nitrogen). Typically, purging of tion, solution catalyst is sprayed into a reactor system under excess oxygen from the system (e. g., With high purity nitro conditions such that at least a substantial quantity of the gen) is necessary after an oxidation step in Which applied solution droplets do not vaporiZe before contacting the bed chromocene (or another applied CCC) is oxidiZed in a con Wall (and optionally also the distributor plate and recycle trolled manner. line), and so that liquid droplets of the solution catalyst con [0040] In some embodiments in Which a solution catalyst tact (and thus a substantial amount of solution catalyst con Whose catalyst component is chromocene (or another CCC) is tacts) the bed Wall and optionally also the distributor plate and applied to at least one interior surface of a reactor system, recycle line in liquid form. Preferably, a uniform or substan each such surface is cleaned and roughened (e.g., by grit tially uniform distribution of liquid droplets of solution cata blasting), and then undergoes oxidiZation (e.g., by opening lyst is deposited on the bed Wall (over its entire surface) and the reactor system to expose each surface to ambient air optionally also on the distributor plate and recycle line. Pref during and/ or after the grit blasting, for example, for a 48 hour erably, after the droplets of solution catalyst have contacted interval folloWing the grit blasting), and then solution catalyst each relevant surface suf?ciently uniformly, the reactor is is applied to each cleaned, roughened, and oxidiZed surface. vented to dry and remove mo st of the solvent (Which may be After application of the solution catalyst (preferably in accor toluene). The best parameters (e.g., drying temperature) for dance With any preferred embodiment of the invention) to drying and removing the solvent after application of liquid each surface, a protective polymer coating is typically formed droplets of solution catalyst in accordance With the invention on each surface (preferably after the applied CCC undergoes Will depend on the particular situation. In some embodiments, a controlled oxidation step typically folloWed by purging of after removal of a suf?cient amount of the solvent, oxygen is excess oxygen from the system). In general, the desired poly introduced into the system to oxidiZe the catalyst (e.g., chro mer coating is formed on each surface (typically the bed Wall mocene) that has been deposited on the bed Wall and option and optionally also at least one other surface) by polymeriza ally on each other surface to receive a polymer coating. After tion catalyZed by the deposited catalyst (Where the desired purging excess oxygen (e.g., With high purity nitrogen) from polymer coating is polyethylene and the deposited catalyst is the system (if such purging is necessary), or after removal of a CCC, the polymeriZation is typically performed after con excess solvent (e.g., if an oxidation step is not performed), the trolled oxidiZation of the deposited CCC folloWed by purging desired polymer coating is then formed on the bed Wall (and of excess oxygen from the system). To initiate formation of optionally also each other surface) by polymeriZation cata the polymer coating, ethylene and a poison scavenger/cocata lyZed by the deposited catalyst. To initiate formation of the lyst (e.g., tri-ethylaluminum (TEAl) or another aluminum polymer coating, ethylene and a poison scavenger/cocatalyst alkyl) are typically added to the system. Chromocene and (e. g., tri -ethylaluminum (TEAl) or another aluminum alkyl) other CCC catalysts are typically used to polymerize ethylene are typically added to the system. but not other monomers. An oxidation step, folloWing solu [0042] In some embodiments of the inventive method, tion catalyst application, is typically required Where the chromocene solution (or other solution catalyst) is injected applied catalyst is chromocene, but such an oxidation step into a reactor (e.g., in the form of liquid droplets) in such a may not be required for other CCC catalysts (e.g., silyl chro manner as to cause the solution catalyst in liquid form to Wet mate). NeW single site CCC catalysts may be used to poly the reactor’s bed Wall (and optionally also the distributorplate merize monomers other than ethylene, but it is unlikely that and recycle line) at least substantially uniformly. The injec such single site CCC catalysts Would need to undergo post tion occurs under conditions such that the liquid solution application oxidation. catalyst’s drying rate is suf?ciently loW so as not to prevent [0041] In the other noted class of embodiments, solution the at least substantially uniform Wetting of the bed Wall (and catalyst (e.g., chromocene solution) is sprayed into a reactor optionally also of the distributor plate and recycle line). Typi that includes inert gas (e.g., nitrogen) and is at least substan cally, a suf?ciently loW drying rate is provided by maintaining tially empty of polymer. In some such embodiments, the a suf?ciently loW temperature in the reactor during the Wet solution catalyst is sprayed by one or more atomiZing noZZles ting step and/or maintaining conditions in the reactor during that produce small droplets (typically having diameter of the Wetting step that are suf?cient to raise the deW point about 20 microns) of the solution that become entrained in gas temperature of the reactor system contents (including the ?oWing throughout the reactor system. Typically, the solution solution catalyst) to (or to a temperature beloW but su?i catalyst droplets become entrained in a ?oWing gas stream ciently near to) the reactor temperature during the Wetting comprising substantially pure nitrogen and the same solvent step. in Which the injected catalyst is dissolved (e.g., toluene) and [0043] During application of the solution catalyst, the reac are carried throughout the reactor system. The droplets even tor bed Wall may (and typically does) have a loWer tempera tually contact the bed Wall, recycle line, and distributor plate ture than the average temperature throughout the reactor. of the reactor system, and solution catalyst is deposited at Thus, during application of solution catalyst in liquid form to US 2012/0070575 Al Mar. 22, 2012

the reactor bed Wall in accordance With some embodiments of fed conventionally. Preferably, enough additional solvent is the invention, it may suf?ce that there be reactor conditions at fed to raise the deW point temperature to Within 5 to 30° C. of the bed Wall that keep the liquid solution catalyst’s drying rate the gas temperature at the coolest point in the reactor system at the bed Wall suf?ciently loW to alloW uniform (or substan (typically the compressor inlet) during the Wetting step. A tially uniform) Wetting of the entire bed Wall, although such suf?ciently high deW point temperature Will provide the reactor conditions do not exist aWay from the bed Wall (e.g., required sloW drying of solution catalyst droplets While pre although the deW point temperature of the reactor contents is venting condensation of liquid on sections of the reactor Wall. substantially beloW, or even far beloW, the average tempera Such condensation Would otherWise produce excessive con ture throughout the reactor). In some embodiments, condi centrations of catalyst on tho se sections of the reactor Wall. To tions at the bed Wall (but not necessarily throughout the minimiZe the amount of additional solvent required to per reactor system) are actively maintained during application of form these embodiments, the reactor gas temperature is main solution catalyst in liquid form to the bed Wall to keep the tained at a relatively loW (e.g., loWer than conventional) liquid solution catalyst’s drying rate at the bed Wall su?i value. When the solution catalyst is chromocene dissolved in ciently loW to alloW uniform (or substantially uniform) Wet toluene, the preferred gas temperature range is 10 to 400 C. at ting of the entire bed Wall. In other embodiments, conditions throughout the reactor system are actively maintained during the compressor inlet. application of solution catalyst in liquid form to the bed Wall, [0046] In accordance With some embodiments of the inven and/ or each other interior surface to Which liquid solution tion, liquid Wetting of a reactor bed Wall (and/or distributor catalyst is to be applied, to keep the liquid solution catalyst’s plate and/or recycle line or other surface of the reactor sys drying rate at each such surface suf?ciently loW to alloW to tem) With solution catalyst is accomplished by forming liquid alloW uniform (or substantially uniform) Wetting of each such droplets of the solution catalyst in the reactor system. The surface (e. g., the deW point temperature of the reactor system droplets are then entrained through the reactor system in a contents, including the solution catalyst, is maintained above relatively sloW-drying environment. The inventors have rec (or beloW but suf?ciently near to) the temperature at the bed ogniZed (in part, as a result of tests) that catalyst deposited on Wall during the Wetting step). In some embodiments, condi a bed Wall (or distributor plate or recycle line) as a liquid tions at the bed Wall are not actively maintained during appli solution is much more effective for forming effective and cation of solution catalyst in liquid form to the bed Wall, and reliable polymer coatings on each relevant surface than cata instead the temperature at the bed Wall is (and is passively lyst deposited from the vapor phase or as a dry poWder as in relied upon to be) suf?ciently loW to keep the liquid solution conventional processes. catalyst’s drying rate at the bed Wall loW enough to achieve uniform (or substantially uniform) Wetting of the entire bed [0047] In some embodiments, the solution catalyst is pref Wall (in this case, the solution catalyst is applied, e. g., injected erentially deposited on the bed Wall rather than on other through multiple noZZles, in such a manner as to adequately interior surfaces. In some embodiments, the solution catalyst Wet the entire bed Wall). is introduced into the reactor system at a plurality of locations [0044] To provide adequate liquid Wetting of the reactor in proximity to a loWer section of the bed Wall. For example, bed Wall (and optionally also the distributor plate and recycle the solution catalyst may be introduced through a plurality of line) With solution catalyst droplets, it is important to prevent upWard-oriented injection devices (e.g., injection devices ori rapid drying of the droplets. If signi?cant drying Were to ented at an angle in the range from about 40 to about 50 occur in the reactor system before adequate liquid Wetting, degrees above a horiZontal plane). The plurality of injection too many of the liquid droplets Would become dry poWder devices may alternatively be oriented in a horiZontal plane before contacting the bed Wall or other relevant surface. Dry around a cylindrical (or generally cylindrical) bed Wall, each poWder on the bed Wall (or distributor plate or recycle line) at an angle in the range from about 40 to about 50 degrees Would be less reliable and effective than liquid droplets in inWard from a tangent to the bed Wall. The injection devices forming the desired polymer coating. In some embodiments may be positioned about 0.15 to about 1.0 meters (or about in Which the solution catalyst is chromocene dissolved in 0.40 to about 0.60 meters) above the distributor plate, option toluene, suf?ciently sloW drying of the solution catalyst drop ally With the outlet of each device positioned about 0.10 to lets is accomplished by maintaining the half-life for droplet about 0.50 meters (or about 0.10 to about 0.20 meters) aWay drying at a minimum of at least tWice the recycle gas turnover from the bed Wall, and optionally With each injection device time in the system (Where “gas turnover time” is the total oriented to emit a generally conical spray of solution catalyst volume of the reactor system, including the reactor and having a cone angle of about 100 to about 120 degrees. In recycle system, divided by the volumetric ?oW rate of gas some embodiments, the solution catalyst is sprayed from one through the recycle system). or more injection devices so as to directly deliver it to the bed [0045] In some embodiments, a suf?ciently sloW drying Wall by droplets actually contacting the bed Wall. In some rate for the solution catalyst is obtained by feeding into the embodiments, multiple injection devices that point in tangen reactor system (With the solution catalyst) additional solvent tial directions to the reactor Wall and are placed to assure that to raise the deW point temperature of the contents of the the loWer portion of the bed Wall is directly impacted With reactor system (including the solution catalyst) to (or to a sprayed solution catalyst at least substantially all the Way temperature beloW but suf?ciently near to) the reactor tem around the circumference of the reactor (and preferably so perature during the Wetting step. The additional solvent can that any overlap of spray patterns from the injection devices is be the same solvent in Which the catalyst is dissolved (e.g., minimiZed). In some embodiments, good ?rst pass contact of toluene, in typical embodiments). Preferably the additional solution catalyst on the bed Wall is achieved by introducing solvent is pre-charged into the reactor before injection of the the solution catalyst at multiple locations around the bed Wall solution catalyst. Alternatively, the additional solvent is pro so as to create a sWirling, solution catalyst-containing cloud vided by feeding a more dilute solution catalyst than Would be that moves up the reactor Wall as it ?oWs With recycle gas. US 2012/0070575 A1 Mar. 22, 2012

[0048] Another aspect of the invention is a method for [0053] After a ?uidized bed polymerization reactor system forming a polymer coating on a bed Wall of a ?uidized bed is fabricated but before it undergoes a chromocene treatment polymerization reactor, including the steps of: (or another treatment preparatory to formation of a polymer [0049] applying solution catalyst to the bed Wall in liquid coating on at least one interior surface thereof), surfaces of the form (e.g., in the form of liquid droplets) at least substantially system are sometimes painted With a zinc based paint to uniformly over the bed Wall, and preferably then drying the prevent formation of rust on the painted surfaces before the applied solution catalyst (or alloWing the applied solution treatment. Such a zinc coating may be applied When the catalyst to dry) so that dry catalyst remains on the bed Wall; system is expected to be stored for a signi?cant time before and undergoing the treatment and then entering into service. The [0050] after step (a), performing a polymer-coat-forming inventors have recognized that When a chromocene treatment polymerization reaction in the reactor, catalyzed by the is performed on a zinc-coated surface of a ?uidized bed polymerization reactor system, the chromocene treatment is applied catalyst, thereby forming the polymer coating on the surprisingly less effective as a preliminary to polymer forma bed Wall. tion than if the surface Were bare (not zinc-coated). The [0051] Preferably, the polymer coating formed in step (b) is inventors have recognized that less polymer is typically suf?ciently thick to reduce substantially the tendency of resin formed on the zinc-coated surface than Wouldbe if the surface sheets to form in the reactor during subsequent polymeriza Were bare, that polymer formed on the zinc-coated surface tion operations (sometimes referred to herein as normal poly may be less effective to prevent generation of undesirable merization operations) performed in the reactor after the levels of static charge and sheeting during operation of the polymer-coat-forming polymerization reaction. In some treated reactor to produce PE resin With metallocene based embodiments, the solution catalyst is chromocene (or other catalysts, and that the system’s static charging characteristics chromium containing compound) dissolved in toluene. Pref may be more sensitive to characteristics of the product being erably, step (a) also includes the step of cleaning solvent from produced than if the surface Were bare at the start of chro the reactor after application of the solution catalyst to the bed mocene treatment. Though less polymer ?lm may be formed Wall. In some embodiments, the reactor has a distributor plate folloWing chromocene retreatment of zinc-coated reactor and a recycle line and step (a) includes the step of applying the Walls, the ?lm characteristics may be adequate for operation solution catalyst in liquid form to at least one of the distributor With less sensitive catalyst systems such Ziegler-Natta based plate and recycle line as Well as to the bed Wall of the reactor, catalysts. at least substantially uniformly over said at least one of the [0054] In a class of embodiments, the present invention is a distributor plate and recycle line. Optionally, betWeen perfor method for treating interior surfaces of a ?uidized bed poly mance of steps (a) and (b), the applied solution catalyst is merization reactor system, said system including at least one oxidized and the reactor is then opened and cleaned. Typi element (e.g., a component or part) subject to fouling if an cally, no ?uidized bed is present in the reactor during perfor excessive amount of polymer coating material is formed on at mance of step (b). Optionally, the method also includes the least one surface of the system (an interior surface of the step of polishing the polymer coating on the bed Wall after system to be referred to as a “sensitive” surface) during per performing step (b). formance of the method (or during a polymerization step [0052] Another aspect of the invention is a method of pro folloWing performance of the method), Where the system also ducing a polymer product (e.g., a polyole?n product pro has at least one other interior surface (to be referred to as a duced using a metallocene based catalyst) in a polymerization “nonsensitive” surface) that does not cause fouling of any reactor system Whose bed Wall (and optionally also at least element of the system if excess polymer is formed thereon. one other interior surface of the system, e. g., a distributor Thus, the system is less subject to fouling by polymer coating plate and/or recycle line surface) has been coated With a material formed on any said “nonsensitive” surface (during polymer (e.g., a high molecular Weight polymer) in accor performance of the method or during a polymerization step dance With the invention. The polymer coating has been folloWing performance of the method) than by polymer coat formed in accordance With the invention by a method includ ing material formed on any said “sensitive” surface in the ing a step of applying solution catalyst in liquid form at least folloWing sense: during “post-coating” operation of the reac substantially uniformly to the bed Wall and each other interior tor system (i.e., operation after formation of the polymer surface of the reactor system to be coated by the polymer. coating on each sensitive and nonsensitive surface) the sys Typically, the polymerizing method produces a polyole?n by tem can operate acceptably if a polymer coating of a ?rst polymerizing a monomer and optionally also a comonomer in thickness (or ?rst average thickness) has been formed on the the presence of a catalyst or catalyst system in a ?uidized bed nonsensitive surface, but the system cannot operate accept reactor system. Some embodiments are methods forpolymer ably With a polymer coating of the ?rst thickness (or the ?rst izing an alpha-ole?n in a ?uidized bed reactor in the presence average thickness) has been formed on at least one said sen of a catalyst (or catalyst system) prone to cause sheeting sitive surface. In other Words, the system is subject to fouling during the polymerization, by maintaining the static electric (of a type that prevents acceptable post-coating operation of charge in the reactor at least one site of possible sheet forma the system) if a polymer coating of the ?rst thickness or tion beloW static charge levels Which Would otherWise cause average thickness has been formed on at least one sensitive sheet formation, Where the bed Wall (and optionally also at surface, Whereas the system is not subject to such fouling if a least one other interior surface) of the reactor system have polymer coating of the same thickness or average thickness been pretreated by forming a polymer coating thereon includ has been formed on each nonsensitive surface. In typical ing by applying solution catalyst (typically including a chro ?uidized bed polymerization reactor systems, surfaces of dis mium-containing compound) at least substantially uniformly tributor plates, coolers, recycle gas lines, and compressor and in liquid form to the bed Wall (and optionally also the at bases are likely to be “sensitive” surfaces, and reactor bed least one other interior surface). Walls are likely to be “nonsensitive” surfaces (in such sys US 2012/0070575 A1 Mar. 22, 2012

tems, distributor plates, coolers, recycle gas lines, and com trolled oxidation of at least some of the CCC that has been pressor bases are more vulnerable to fouling by excessive applied (i.e., to oxidize in a controlled manner at least some of polymer material than are reactor bed Walls). the applied CCC). In some embodiments, the CCC comprises [0055] In the embodiments noted in the previous para chromocene. In preferred embodiments in this class, the con graph, the invention is a method for treating interior surfaces centration of oxygen in the system during the oxidation step of a ?uidized bed polymerization reactor system, said sur is limited so as not to exceed 200 parts per million by volume faces including at least one sensitive surface (e. g., a distribu (ppm), and more preferably so as not to exceed 100 ppm. In tor plate surface, cooler surface, compressor surface, and/ or a some embodiments, the oxidation step has a controlled dura recycle line surface) and at least one nonsensitive surface tion, preferably so that the oxidation step is completed in less (e.g., a reactor bed Wall or portion thereof), said method than about tWo hours (less than about one hour in some including the steps of: (a) applying a zinc coating (e.g., a embodiments). Typically, a polymerization reaction (cata coating of zinc-based paint) to at least one said sensitive lyzed by the catalyst) is then performed to form on each surface (e.g., to each said sensitive surface) but not to at least surface a polymer coating. Preferably the so-formed coating one said nonsensitive surface (e.g., not to any said nonsensi reliably functions as an insulating layer that reduces static tive surface); and (b) after step (a), applying a solution cata charging in the reactor system (and thereby reduces the poten lyst at least substantially uniformly and in liquid form (e. g., in tial for sheeting) during subsequent polymerization reactions the form of liquid droplets of the solution catalyst) to each in the reactor system. Preferably, the solution catalyst is said sensitive surface and each said nonsensitive surface. In applied at least substantially uniformly and in liquid form some such embodiments, the catalyst component of the solu (e.g., in the form of liquid droplets of the solution catalyst) to tion catalyst is or includes a CCC. For example, the catalyst each surface. Typically, the applied solution catalyst is dried component of the solution catalyst is or includes chromocene (or alloWed to dry) to leave a dry coating of catalyst on each in some preferred embodiments. Typically, the applied solu surface before the oxidation step. tion catalyst is dried (or alloWed to dry) to leave a dry coating of catalyst on each said nonsensitive surface (and typically BRIEF SUMMARY OF THE DRAWINGS also each said sensitive surface) and a polymerization reac tion (catalyzed by the catalyst) is then performed to form on [0057] FIG. 1 is schematic diagram of a conventional gas each said nonsensitive surface (and optionally also each said phase polymerization reactor system of the prior art including sensitive surface) a polymer coating that reliably functions as a tube 2 for injecting solution catalyst into reactor 4. an insulating layer that reduces static charging in the reactor [0058] FIG. 2 is a schematic diagram of a portion of a gas system (and thereby reduces the potential for sheeting) during phase polymerization reactor system including an atomizing subsequent polymerization reactions in the reactor system. nozzle 3 for injecting solution catalyst into reactor 4. Preferably, the steps are performed such that the polymer [0059] FIG. 3 is a schematic diagram of a portion of a gas coating formed on each nonsensitive surface reliably func phase polymerization reactor system including an injection tions as an insulating layer that reduces static charging in the tube 5 for injecting solution catalyst into recycles line 11. reactor system (and thereby reduces the potential for sheet [0060] FIG. 4 is a schematic diagram of a portion of a ing) during subsequent polymerization reactions in the reac ?uidized bed polymerization reactor system in Which solu tor system, Without forming an undesirable amount of poly tion catalyst is introduced into the reactor through injection mer on any sensitive surface (i.e., Without fouling any devices 300. sensitive surface). This can eliminate the need to clean (or [0061] FIG. 5 is a top vieW of another portion of the system open for cleaning) the reactor system after the polymer coat partially shoWn in FIG. 4, shoWing the position and orienta ing-forming polymerization reaction (and before subsequent tion of a plurality of injection devices 300 located inside a operation of the system to perform a post-coating polymer ?uidized bed reactor. ization reaction), and/or the need to clean (or open for clean ing) the reactor system after the step of applying the solution [0062] FIG. 6 is a graph ofthe mass (in grams) ofpolymer catalyst (and optionally also subsequent oxidization of the formed on test coupons in experiments in Which each coupon applied catalyst) and before the polymer coating-forming has been pretreated by depositing an indicated amount (in polymerization reaction. For example, the zinc coating may grams) of chromocene catalyst thereon, either by liquid depo be applied so as to prevent formation of more than an accept sition (as indicated by the diamond-shaped symbols plotted) able amount of polymer on each sensitive surface (e.g., to or vapor deposition (as indicated by the square-shaped sym prevent fouling of the distributor plate and/or compressor bols plotted). With polymer). The zinc coating may be applied (and the other [0063] FIG. 7 is a plot ofmeasured ?lm thicknesses on a set method steps performed) so as to form less polymer on each of metal coupons. sensitive surface than on each nonsensitive surface (e. g., the polymer coating formed on each sensitive surface is thinner DETAILED DESCRIPTION or has smaller average thickness than that formed on each nonsensitive surface). [0064] Before the present compounds, components, com [0056] In another class of embodiments, the invention is a positions, and/or methods are disclosed and described, it is to method for treating at least one interior surface (e.g., a bed be understood that unless otherWise indicated this invention is Wall) of a ?uidized bed polymerization reactor system, not limited to speci?c compounds, components, composi including the steps of applying a solution catalyst to each said tions, reactants, reaction conditions, ligands, metallocene surface, Where the catalyst component of the solution catalyst structures, or the like, as such may vary, unless otherWise is or includes at least one chromium containing compound speci?ed. It is also to be understood that the terminology used (“CCC”), and then (optionally after removal of any excess herein is for the purpose of describing particular embodi solvent) introducing oxygen into the system to cause con ments only and is not intended to be limiting. US 2012/0070575 A1 Mar. 22, 2012

[0065] It must also be noted that, as used in the speci?cation during application of the solution catalyst in liquid form to the and the appended claims, the singular forms “a,” “an” and bed Wall and each other relevant interior surface of the sys “the” include plural referents unless otherwise speci?ed. tem. Tube 2 has an inner diameter in the range from about 1/s" [0066] As used herein, all reference to the Periodic Table of to 1A" in typical implementations, and can be the same cata the Elements and groups thereof is to the NEW NOTATION lyst injection tube also used in normal polymerization opera published in HAWLEY’S CONDENSED CHEMICAL DIC tion of the reactor system. During both conventional solution TIONARY, Thirteenth Edition, John Wiley & Sons, Inc., catalyst injection and solution catalyst injection in accor (1997) (reproduced there With permission from IUPAC), dance With the invention, solution catalyst is injected through unless otherWise noted, for example, With Roman numerals tube 2 into reactor 4 While reactor 4 is empty of polymer and referring to the Previous IUPAC form also contained therein. recycle gas compressor 6 causes gas to ?oW upWard through [0067] For the sake of brevity, de?nitions provided in the reactor 4 from the outlet of recycle line 11, through holes in BACKGROUND Will not be repeated but are hereby incor distributor plate 10, and to the inlet of line 11. In one imple porated by reference into this section Where relevant. mentation in Which the solution catalyst is chromocene dis [0068] A class of embodiments is an improved method for solved in toluene, the atmosphere in reactor 4 during injection polymerizing an alpha-ole?n (or other monomer and/or of the solution catalyst is nitrogen at a pressure of 5-8 bars, comonomer) in the presence of a catalyst or catalyst system in and recycle gas heat exchanger 12 (Which normally functions a ?uidized bed reactor having a bed Wall (and optionally also to remove heat during normal polymerization operation of the at least one other interior surface of the reactor system) that has been pre-coated With a polymer. The polymer coating has reactor system) regulates the temperature in the reactor been formed in accordance With the invention by a method Within the range 80-90° C. during injection of the chro including the step of applying solution catalyst in liquid form mocene solution by providing a ?oW of heat into the system. at least substantially uniformly to the bed Wall and each other In some implementations, at least tWo injection tubes 2 interior surface of the reactor system on Which the coating is extend through the side Wall of reactor 4 (e. g., in the positions formed. The polymer coating reduces static charging in the and orientations of injection devices 300 in FIG. 5). reactor system and thus reduces the potential for sheeting [0072] In other embodiments, solution catalyst is delivered during the polymerization reaction. In some embodiments, into a reactor system via one or more injection devices (e. g., the polymer coating is a high molecular Weight polymer tubes) each having an atomizing nozzle at its outlet. An coating Which may have thickness greater than about 10 mils example of such a system is the system partially shoWn in (0.25 mm) on the bed Wall of the reactor. Herein, the phrase FIG. 2, Which is identical to the FIG. 1 system except in that “high molecular Weight polymer coating” denotes a coating an injection device (e.g., tube) having an atomizing nozzle 3 comprising at least 25 Wt % of an insoluble polymer fraction at its outlet replaces each simple injection tube 2 of the FIG. and a soluble polymer fraction having at least 10 Wt % poly 1 system. To treat each interior surface of the FIG. 2 system mers (based upon the total Weight of the high molecular that is to be coated With a polymer, pressurized solution Weight polymer coating) exhibiting a molecular Weight as catalyst is sprayed into reactor 4 by means of atomizing measured by high temperature GPC (using a trichloro ben nozzle 3 to produce small droplets 7 (typically having diam zene solvent at 150° C., sample prepped at 160° C. for 2 hr, eter of about 20 microns) of the solution catalyst that become microWaved at 175° C. for 2 hr) of at least one million Daltons entrained in the gas ?oW through the reactor system. The or greater. droplets eventually contact the bed Wall (ie the portions of [0069] We shall describe several embodiments of the inven the interior surfaces of the reactor system that are in contact tive method With reference to FIGS. 1-5. With the ?uidized bed during normal polymerization opera [0070] FIG. 1 is a simpli?ed diagram of a conventional tion of the reactor system), recycle line 11, and distributor polymerization reactor system including reactor 4 and at least plate 10 of the reactor system. In accordance With preferred one simple injection tube 2 extending through the side Wall of embodiments, the solution catalyst is deposited at least sub reactor 4. During normal polymerization operation of the stantially uniformly in liquid form on the bed Wall and option system, a ?uidized bed is maintained in reactor 4. The interior ally also at least substantially uniformly in liquid form on surfaces of reactor 4 that are in contact With the ?uidized bed each other surface to be coated With a polymer coating (e. g., during normal polymerization operation are referred to as the recycle line 11 and distributor plate 10). “bed Wall.” Prior to normal polymerization, it is desirable to [0073] In other embodiments, solution catalyst is intro perform an embodiment of the inventive method to pre-coat duced into a gas recycle line (e.g., recycle line 11 of FIG. 3) the bed Wall (and optionally also other interior surfaces of the of a polymerization reactor system by an injection device reactor system) With a polymer coating. During the pre-coat (e.g., a simple tube) in ?uid communication With the recycle ing method, a solution catalyst is introduced through tube 2 line. An example of such a system is the system partially and applied in liquid form to the bed Wall and each other shoWn in FIG. 3. The FIG. 3 system is identical to the FIG. 1 interior surface of the system to be pre-coated With polymer, system except in that it includes an injection device compris and a special polymerization reaction is then performed in the ing simple tubing 5 (shoWn in FIG. 3) having an outlet that presence of the applied catalyst to form the polymer coating. extends into recycle line 11. Tubing 5 may have an inner This special polymerization reaction is not the normal poly diameter in the range 1 mm to 10 mm) Optionally, an atom merization reaction normally performed in the reactor after izing nozzle is ?tted at the outlet end of tubing 5 but this is formation of the polymer coating. typically not required because a suf?ciently high speed (e. g., [0071] With reference to FIG. 1, tube 2 is positioned for 15-25 msec) gas ?oW can be maintained through recycle line injecting solution catalyst (e.g., chromocene solution) into a 11 to eliminate the need for an atomizing nozzle. Gas ?oWing stream of ?oWing gas Within reactor 4. In a class of embodi With su?iciently high speed and turbulence Will induce for ments of the inventive method, such a gas stream ?oWs mation of small droplets of the introduced solution catalyst in upWard through reactor 4 from the outlet of recycle line 11 line 11 even Without an atomizing nozzle, and such solution US 2012/0070575 A1 Mar. 22, 2012

catalyst droplets Will become entrained in the gas ?oW [0078] Any injection device may be employed that facili throughout the system and reach each surface to be treated. tates dispersion of a solution catalyst (e.g., a chromium [0074] Other embodiments employ other means for inject containing compound in an inert solvent) suitable for per ing solution catalyst into a polymerization reactor system. To forming the inventive method. Tests to simulate reactor maximize deposition of the solution catalyst (typically a conditions during injection may be conducted to help facili chromium-containing compound in solution) in liquid form tate the selection of injection devices. In any of the embodi on the bed Wall on the ?rst pass up the reactor, the injection ments described herein, the injection devices may have spray facilities preferably introduce the solution catalyst at a plu nozzles at their outlets, for example, 1100 V-jet Nozzles rality of locations. In any of the embodiments described (model H1/4VV11006 supplied by Spraying Systems Com herein, solution catalyst may be injected into the reactor pany). A 2.75 BAR nozzle differential pressure (DP) may be system through a plurality of injection devices. In order to used to achieve a desired 2 kg/min ?oW rate through the 1 10° achieve good ?rst pass deposition of solution catalyst along V-jet Nozzles. the bed Wall, the solution catalyst may be introduced at a [0079] Referring again to FIG. 5, spacing of the plurality of plurality of locations in such a manner as to create a sWirling, locations for introducing the solution catalyst depends on the catalyst solution-containing cloud that moves up the reactor diameter of the ?uidized bed reactor being treated, the place Wall. In any of the embodiments described herein in Which ment of the injection devices, and the orientation and spray injection devices (e.g., spray nozzles) introduce solution cata pattern 310 of each injection device. In some embodiments, lyst into a generally cylindrical reactor, the spacing betWeen the injection devices are placed to assure that the loWer por the injection devices may be at least substantially equidistant tion of bed Wall 302 is directly impacted With liquid spray around the reactor circumference. Referring to FIG. 4, inj ec from the injection devices substantially all the Way around the tion devices 300 (Which are simple tubes in some implemen circumference of the reactor. In some embodiments, the tations and tubes With atomizing nozzles at their outlet ends in injection devices are placed so as to minimize signi?cant other implementations) may be attached to tubing 202 that overlap of their spray patterns. In any of the embodiments travels through bulkhead ?ttings 204 to individual cylinders described herein, the injection devices may be spray devices, 206a-206e containing solution catalyst (e.g., chromium-con for example, spray nozzles each having a spray pattern 310 taining catalyst in solution). The injection system may be spanning about 100 to 1200 C., and may be placed such that a constructed inside the reactor after the reactor is cleaned, for chord length 308 betWeen each of the injection devices is example, by grit blasting, in preparation for the treatment. about 1.5 to about 1.9 meters. [0075] Still referring to FIG. 4, the solution catalyst may be [0080] In any of the embodiments described herein, solu introduced at a plurality of locations in proximity to a loWer tion catalyst may be introduced via a plurality of injection section of bed Wall 208 of a ?uidized bed reactor. For the devices, each having a spray angle 310 of about 100 to 120° purposes of this speci?cation, the locations are considered in C., each located about 0.10 to 0.20 meters (dimension “A” proximity to the bed Wall 208 if they are close enough such 312) from the bed Wall 302, each placed such that a chord that the particular injection device selected and ?oW rate used length 308 betWeen adjacent injection devices is about 1.5 to effectively deliver the solution catalyst directly to the bed about 1.9 meters, each angled 40-50° (angle 0306) inWard Wall by droplets actually contacting the bed Wall. In any of the from Wall tangent 304, and each angled 40-50° up from embodiments described herein, the solution catalyst may be horizontal. In other embodiments, the injection devices may introduced, for example, by spray nozzle, at a location that is be located about 0.4 to 0.6 meters above the distributor plate. located at a distance “A” 210 from the Wall, Wherein “A” 210 [0081] Prior to introducing a solution catalyst into a reactor may be about 0.1 to about 0.5 meters. In other embodiments, system in accordance With the invention, the system may be “A” 210 may be in the range from about 0.1 to 0.2 meters, or prepared for treatment. The preparations may include: may be about 0.12 meters. removing ?xed tee-pees (resin back-?oW preventors above [0076] As used herein, the loWer section of the bed Wall 208 the holes in the distributor plate); cleaning (for example, by refers to the ?rst 2.5 meters of the ?uidized bed reactor Where grit blasting) the expanded section, dome, reactor Walls, dis the ?uidized bed contacts the reactor Wall(s). In the gas phase tributor plate, and bottom head; cleaning (for example, by reactorpartially shoWn in FIG. 4 (Which contains a distributor hydroblasting) the cycle gas piping to remove polymer crust; plate 212), this is the 2.5 meters above distributorplate 212. In installing injection equipment; and any other requirements any of the embodiments described herein, solution catalyst necessary to protect speci?c components (e.g., expansion may be introduced about 0.15 to about 2.0 meters above the belloWs, valves, and ?oW venturis). distributor plate, about 0.15 to about 1.0 meters above the [0082] In any of the embodiments described herein, the distributor plate, about 0.4 to 0.6 meters above the distributor solution catalyst is introduced into the ?uidized bed reactor plate, or about 0.5 meters above the distributor plate. by injecting the ?uid during a time interval Whose duration [0077] Referring to FIG. 5, in any of the embodiments, a depends on factors including the injection device(s) plurality of inj ection devices 3 00 may be used to introduce the employed, the placement of the injection device(s), and the solution catalyst into a reactor having Wall 302. Each injec composition of the solution catalyst. An optimal period of tion device 300 may be oriented relative to the reactor Wall time for solution catalyst injection may be determined. The 302 at an angle 0306 in from Wall tangent 304, and angled spray characteristics of the injection devices may require a 40-50° upWard (out of the plane of FIG. 5) from horizontal to speci?c ?oW rate to each injection device to provide an opti facilitate a sWirling, solution catalyst-containing cloud that mal ?oW pattern. The duration of the injection interval moves up the reactor Wall. In any of the embodiments depends on the ?oW rate required for the injection device described herein, the angle 0306 may be betWeen about 40 to selected, the amount of solution catalyst to be injected, the about 50°. In other embodiments, the angle 0306 may be in number of injection devices selected, and the number of the range 45-50° and each injection device 300 may be angled injection devices used at one time. In some embodiments, the about 450 up from horizontal. solution catalyst is introduced through one injection device at US 2012/0070575 A1 Mar. 22, 2012

a time; in others it is injected through at least tWo injection venting any non-reacting gas from the reaction system to devices at a time. In some embodiments, solution catalyst is prevent releasing un-oxidized chromium from the reaction introduced into a ?uidized bed reactor for a time interval of system. duration less than one hour (e. g., of duration in the range from [0087] In some embodiments, 1.0 kg of air is introducedper about 15 to about 30 minutes). kg of CCC injected. The air may be supplied from pressurized [0083] During and after introduction of solution catalyst breathing air cylinders (one such cylinder typically contains into the ?uidized bed reactor system, a non-reacting gas is approximately 10 kgs of air). In other embodiments, an initial preferably circulated through the system. The gas may circu amount of air is added to the reactor, a conventional analyzer late for a ?rst period of time before the solution catalyst is measures the level of oxygen in the reactor, and then addi tional air may be added incrementally until an analyzer read introduced, and may continue to circulate for a second period ing of approximately 100 ppmv is achieved. In some embodi of time after the solution catalyst is introduced While the ments, the oxidizing step may be conducted While circulating solution catalyst is dispersed and deposited in liquid form at the non-reacting gas at a CGV of about 0.35 to about 0.45 least substantially uniformly on the bed Wall. Preferably, the meters/ sec and a temperature of about 80 to about 900 C. second period of time is less than about 5 hours (and more [0088] In a class of embodiments, the method includes the preferably is less than about 1 hour). In some embodiments, step of reacting a CCC or other solution catalyst that has been the gas circulates at a temperature of about 80 to 90° C. With deposited in liquid form in accordance With the invention and a cycle gas velocity (“CGV”, or super?cial gas velocity or oxidized, to form a high molecular Weight polymer coating on “SGV”) in the range from about 0.35 to about 0.45 meters/ the bed Wall (and optionally on at least one other interior sec. Herein, CGV denotes the volumetric ?oW of the cycle gas surface) of a ?uidized bed reactor system Without opening the ?uidization stream divided by the cross sectional area of the system for cleaning after the oxidation step and before the ?uid bed section of the reactor. polymer coating-forming polymerization reaction. In con [0084] In some embodiments, solution catalyst is deposited trast, in some conventional methods, the reactor system is on the bed Wall of the ?uidized bed reactor rather than on cleaned to remove excess CCC deposited on surfaces of the other surfaces in the reaction loop, such as the cycle gas cycle piping, cycle compressor, cycle cooler, and/or distribu piping, cycle compressor, cycle cooler, and bottom of the tor plate before the CCC is reacted to form a polymer coating. distributor plate. Without being bound by theory, it is believed that such clean [0085] In some embodiments, after solution catalyst has ing is required because the conventional method circulates been deposited in liquid form at least substantially uniformly and deposits a signi?cant amount of CCC throughout the on the bed Wall (and each other interior surface to receive a reactor system, rather than depositing it preferentially on the polymer coating), the deposited catalyst is “oxidized” by bed Wall. In some embodiments in Which it is desired to form injecting oxygen into the reaction system before forming the the polymer coating only on the bed Wall, the polymer coating polymer coating and While the non-reacting gas continues to can be formed Without ?rst cleaning the reactor system circulate. Typically, the oxidizing step is completed in less because the solution catalyst is deposited preferentially on the than about 2 hours (and less than about one hour in some bed Wall; not on other interior surfaces of the system. Thus, in embodiments). In some cases in Which the deposited catalyst one class of embodiments, the deposited catalyst is reacted is a CCC, the CCC reacts With oxygen during the oxidizing With a monomer (e.g., ethylene) to form a polymer coating step such that one of the cyclopentadienes is replaced and the (e.g., a high molecular Weight polymer coating) on the bed chromium is oxidized. During the subsequent coating-form Wall after the catalyst has been oxidized and before opening ing polymerization reaction, a cocatalyst (e.g., tri-ethylalu the reactor system for cleaning. minum (TEAl)) reduces the chromium back to the desired [0089] In any of the embodiments described herein, the valence state, for example, a valence state of plus 2 to 3. By level of oxygen and inert solvent (the solvent component of minimizing both the level and duration of oxygen exposure, the deposited solution catalyst) may be reduced by purging the activity of the chromium is maintained at higher levels and the reactor system before the deposited catalyst is reacted the time to purge out the inert solvent is reduced. The higher With a monomer to form a polymer coating. For example, the chromium activity can result in formation of a thicker poly ?uidized bed reactor system may be purged to less than about mer coating (e.g., a thicker high molecular Weight polymer 1 ppmv oxygen and less than about 100 ppmv of inert solvent coating) over a shorter period of time When the catalyst is before the deposited catalyst is reacted With the monomer. reacted With a monomer. [0090] In any of the embodiments described herein, cata [0086] In any of the embodiments described herein, the lyst that has been deposited on the bed Wall (and optionally on amount of oxygen added to the reactor during the oxidation at least one other interior surface) of a reactor system and step may be limited by limiting the amount of oxygen added oxidized may catalyze a polymerization reaction in Which a to a substantially stoichiometric amount relative to the monomer (e. g., ethylene) is polymerized to form a high amount of chromium introduced into the ?uidized bed reac molecular Weight polymer coating on the bed Wall (and each tor. In other embodiments, the amount of oxygen may be other interior surface). Optionally, the polymerization is per greater than a substantially stoichiometric amount relative to formed in the presence of a cocatalyst to form the high the chromium introduced into the ?uidized bed reactor. In molecular Weight polymer coating. During the polymeriza other embodiments, the amount of oxygen added to the reac tion step, the reactor system may be ?rst heated to about 80 to tor may be limited by limiting the concentration of oxygen in 900 C. and the pressure of non-reactive gas in the reactor may the reactor to less than about 200 parts per million by volume be established at about 5 BARG after purging is complete. (ppmv), or less than about 100 ppmv. In other embodiments, Next, the monomer may be fed to establish about 4 BARA of the oxygen added may be less than about 100 ppmv, and the monomer partial pressure. In some embodiments, there may time of the oxidizing step is less than about 1 hour. In further be greater than about 4 BARA of monomer in the reactor embodiments, the oxidizing step may be completed Without before introducing a cocatalyst, to prevent the cocatalyst from US 2012/0070575 A1 Mar. 22, 2012

reacting With the deposited catalyst the absence of monomer, reacting. In other embodiments, substantially all of the Which is thought to reduce the effectiveness of the polymer cocatalyst, for example TEA1, is depleted after about 50 ization. The cocatalyst may be an organometal compound, hours of reacting. e.g., tri-ethylaluminum (TEA1), and may be fed in at a uni [0094] After the cocatalyst feed is complete, the polymer form rate over about a 60 minute period. Reactor pressure and coating-forming polymerization reaction may further com monomer partial pressure typically rise during the cocatalyst prise a soaking step, Wherein the non-reactive gas and the injection and reacting period due to various system purges monomer are circulated for greater than about 40 (or 60) routinely fed to the reactor system. In any of the embodiments hours. During the soaking step, the deposited catalyst (e.g., described herein, the feeding period may be completed With CCC) continues to react With the monomer in the presence of out performing a reactor vent. In some embodiments, the the cocatalyst to form the polymer coating. During the soak partial pressure of monomer (e.g. ethylene) may be about 5 to ing step, reactor venting to control pressure may be required. about 20 BARA during the polymerization reaction. In other FloWs into the reaction system and all equipment in the reac embodiments, feed ?oWs into the reaction system (monomer tor system may be minimized to minimize the required vent and inert purges) are balanced such that 100% of the cocata ing and thus the loss of cocatalyst from the ?uidized bed lyst is charged before the reactor total pressure reaches a reactor. In any of the embodiments described herein, the maximum alloWable level (Which may require venting), and reaction system may be held at about 80 to 900 C. at a pressure before the monomer partial pres sure reaches about 10 BARA. of about 15 to about 25 BARG While the non-reactive gas and [0091] The amount of cocatalyst (e.g., TEA1) fed may (op monomer are circulated at a CGV of about 0.6 to about 0.70 tionally, in order of priority): provide su?icient cocatalyst to meters/ second. activate at least about 75% of the deposited catalyst; be lim [0095] In any of the embodiments described herein, the ited to ensure any liquid cocatalyst ?lm on reactor Walls soaking step may be folloWed by deactivating the cocatalyst. vaporizes by the midpoint (on a time basis) of the reacting The cocatalyst may be deactivated by feeding carbon dioxide step; provide that cocatalyst starvation Will not occur before (CO2) to the ?uidized bed reactor. The CO2 may be fed to about 5 to about 15 hours, or about 10 hours, before the end of achieve a concentration of greater than about 0.5 mol % in the the reacting step (depends on cocatalyst charge, vent rate, and ?uidized bed reactor. Furthermore, the CO2 may be circulated impurity levels); and provide minimal residual cocatalyst at for at least about 1 hour. the end of the reacting step. In some embodiments, the [0096] In other embodiments, the cocatalyst may be hydro amount of cocatalyst fed in may be about 0.5 to about 4.0 lyzed prior to opening the ?uidized bed reactor for inspection kilograms per kilogram (or about 1.0 to about 2.0 kilograms) and cleaning. In any of the embodiments described herein, the of deposited catalyst. ?uidized bed reactor may be hydrolyzed by adding Water or steam to achieve a concentration of greater than about 300 [0092] Excessive reactor venting, and the levels of impuri ppmv, or greater than about 450 ppmv, of Water in the ?uid ties in the reaction system and system feeds, may change the ized bed reactor and circulating for at least about 1 hour. effective cocatalyst/catalyst (e. g., TEA1/ CCC) ratio. For a [0097] After reacting deposited solution catalyst (e.g., ?xed amount of cocatalyst fed, cocatalyst is effectively CCC) to form a polymer coating on the bed Wall (and option removed from the system by venting and by reacting With ally at least one other interior surface), the ?uidized bed poisons. For example, venting results in a loss of cocatalyst reactor may be opened for inspection and cleaning. The With the vented gas, and thus less active cocatalyst available cocatalyst may be deactivated as discussed above before to react With the deposited chromium. The effective cocata opening the reactor and exposing it to the air. While the lyst/ chromium ratio is loWered by the loss of cocatalyst, and reactor is open, the injection equipment may be removed, the the catalyst activity may drop. Thus, in any of the embodi internals may be inspected and cleaned as required, and mea ments described herein, the amount of cocatalyst introduced surements may be taken to assure the surfaces of the bed Wall into the ?uidized bed reactor may be adjusted for either high Were properly treated. Measurements that may be taken feed impurities and/ or high venting rates. For the purposes of include charge decay measurements, chromium level mea this application, a level of impurities of 4 ppmv or higher is surements, or coating thickness measurements. The bed Wall, considered a high impurity level. A high venting rate Will expanded section, cycle piping, cycle cooler, and cycle com depend on the size of the reaction system. In one embodiment, pressor may be inspected and cleaned as required. Rough Wherein the reaction system is a 4.9 meter diameter reactor surfaces may be scraped or polished to provide a smooth vessel, a venting rate above about 1,500 kgs/hour is a high surface. In any of the embodiments described herein, the bed venting rate. Wall may be polished, for example by hand scraping, to pro [0093] Another method of determining the cocatalyst feed vide a smooth bed Wall. In other embodiments, the distributor amount is to ?x the level of cocatalyst feed based on experi plate may be cleaned, for example, by drilling and/or grit ence or after some experimentation. Thus, in some embodi blasting, to remove most or substantially all of the chromium ments, about 1.7 to about 2.3 kgs of TEA1 per kg of active and high molecular Weight polymer from the surfaces. In chromocene may charge to the reactor. In other embodiments, other embodiments, the ?xed tee-pees removed before intro all feeds to the reactor comprise less than 2.0 ppm poisons. In ducing the solution catalyst may be replaced With neW tee other embodiments, a vent rate of about 10% of the reaction pees or removable deck plate-type ?oW de?ectors during the system contained gas mass at about 80 to 900 C. and about 16 cleaning step. to 20 BARG may be established While forming the high [0098] In any of the embodiments described herein, a scrub molecular Weight polymer coating. Furthermore, in any of the bed may be charged to the ?uidized bed reactor, ?uidized, and embodiments described herein, the amount of TEA1 fed may dumped folloWing the cleaning step to remove any grit or be controlled such that there may be no substantial liquid other loose material contaminants left in the reactor system TEA1 present on any reactor surface after about 30 hours of during the cleaning step. US 2012/0070575 A1 Mar. 22, 2012

[0099] After a polymer coating has been formed on the bed labeled “Chromocene Treat-No Zinc” are measured thick Wall (and optionally at least one other interior surface) of a nesses of polymer coatings formed on a third set of four metal ?uidized bed reactor that has been pre-treated in accordance coupons by performing chromocene treatment on the cou With the invention, and after the reactor has been cleaned, the pons (Without ?rst applying a zinc coating thereto) and then reactor may be placed in or returned to routine commercial performing a polymerization reaction (catalyzed by the service. Typically, any of a broad range of commercial poly applied catalyst) on the treated coupons; and the four values mer products may be produced in the treated reactor system labeled “Chromocene Treat-Zinc” are measured thicknesses immediately after the coating formation and cleaning, by a of polymer coatings formed on a fourth set of four zinc-coated polymerization reaction catalyzed With any of a Wide variety metal coupons by performing the same chromocene treat of catalyst systems (e.g., a Phillips-type chromium catalyst ment on the coupons and then performing the same polymer system, a Ziegler-Natta catalyst system, or a metallocene ization reaction (catalyzed by the applied catalyst) on the catalyst system). treated surfaces. Before forming the polymer coating on the [0100] After a ?uidized bed polymerization reactor system coupons in the fourth set, the coupons in the fourth set Were is fabricated but before it undergoes a chromocene treatment painted With the same zinc-based paint and in the same man (or another treatment preparatory to formation of a polymer ner as the coupons in the second set Were painted. As apparent coating on one or more interior surfaces thereof), surfaces of from FIG. 7, the applied zinc coating (coating of zinc-based the system are sometimes painted With a zinc based paint to paint) had an average thickness of about 3 mils, and the prevent rust from forming on the painted surfaces before they average thickness of the polymer coating formed on the cou are treated. Such a zinc coating may be applied When the pons in the third set Was much greater than the average thick system is expected to be stored for a signi?cant time before ness of the polymer coating (excluding the zinc-coating undergoing the treatment and then entering into service. As a thickness) formed on the coupons in the fourth set. result of observations of polymerization reactor systems and [0102] It also became apparent from the tests on coupons tests on metal foil coupons (some painted With zinc-base also that the polymer formed on a zinc-coated, chromocene paint, and others unpainted), the inventors have come to treated reactor system surface is typically less effective to appreciate that When a chromocene treatment is performed on prevent generation of undesirable levels of static charge and a zinc-coated surface of a polymerization reactor system, the sheeting during operation of the reactor system to produce PE treatment surprisingly is less effective as a preliminary to resin than if the surfaces Were bare at the start of treatment, polymer formation than if the surface Were bare (not zinc and that the system’s static charging characteristics is likely coated). During the tests, the coupons Were subjected to a be more sensitive to characteristics of the product being pro standard chromocene treatment. Then, a polymerization reac duced if the coated surfaces Were zinc-coated at the start of tion Was performed to produce a polymer coating on the chromocene treatment than if the surfaces Were bare at the treated coupons. Molecular Weight, elemental composition, start of chromocene treatment. ?lm thickness, and electrical properties of the polymer coat [0103] By studying coupons that Were zinc-coated before ings Were then measured. The electrical properties Were mea chromocene treatment, it Was also observed that the zinc sured using a charge decay technique in Which a corona coating on each coupon had a dense bottom layer and a more voltage Was applied to each coated coupon and voltage reten porous upper layer, the chromocene treatment resulted in tion as a function of time Was then determined. incorporation of a signi?cant amount of chromocene catalyst [0101] The tests on coupons (and observations on reactor in the zinc coating’s upper layer, and the catalyst incorporated systems) suggested that the molecular Weight and Weight in the zinc coating’s upper layer did not participate in forma distribution of the polymer coated on surfaces of a reactor tion of a polymer coating on any coupon during a post system (as a result of chromocene treatment folloWed by chromocene-treatment polymerization operation. coating-forming polymerization) does not depend on [0104] Often, a polymer coating-forming polymerization Whether the surfaces are zinc-coated before the treatment. operation on a non-zinc-coated polymerization reactor sys This result Was con?rmed by measurements of scrapings of tem (preliminary to normal operation of the system) causes polymer coatings formed on actual reactor surfaces, some of fouling of components of the system. The inventors have Which had received zinc coatings prior to chromocene treat come to appreciate that such fouling is caused by excessive ment and some of Which had not received zinc coatings prior polymer formation on some interior surfaces of the system to chromocene treatment. HoWever, the coupon tests sug during the polymer coating-forming polymerization opera gested that in typical cases less polymer is formed on a zinc tion. In particular, distributor plates, coolers, recycle gas coated (and then treated) surface than Would be if the surface lines, and compressor bases are likely to be fouled by forma Were bare before chromocene treatment (the amount of poly tion of excess polymer on surfaces thereof. Often, the system mer formed on the coupons having zinc-coated surfaces prior must be opened and cleaned to remove the excess polymer to chromocene treatment averaged about 80% less than on the material before it can be placed into service. coupons that had not received a zinc coating before chro [0105] In a class of embodiments, the present invention is mocene treatment). The latter result is apparent from FIG. 7, an improved method for treating interior surfaces of a ?uid a set of bar graphs indicative of measurements obtained dur ized bed polymerization reactor system preliminary to (or as ing the above-mentioned tests of ?lm thicknesses (in units of a step of) a polymer coating-forming polymerization opera mils) on various coupons. In FIG. 7, the four values labeled tion on the system, to reduce substantially (and preferably “Control-No Zinc” are measured ?lm thicknesses on a ?rst prevent) fouling of the system by excess polymer produced set of four bare metal coupons; the tWo values labeled “Con during the polymer coating-forming polymerization opera trol-Zinc” are measured zinc coating thicknesses on a second tion. The system includes at least one element (e.g., a com set of tWo metal coupons painted With zinc-based paint (nei ponent or part) subject to fouling if an excessive amount of ther of Which had received chromocene treatment or Were polymer coating material is formed on at least one surface of present during a polymerization reaction); the four values the system (an interior surface of the system to be referred to US 2012/0070575 A1 Mar. 22, 2012

as a “sensitive” surface) during performance of the method reactor system (and thereby reduces the potential for sheet (or during a polymerization operation following performance ing) during subsequent polymerization reactions in the reac of the method), and the system also has at least one other tor system, Without forming an undesirable amount of poly interior surface (to be referred to as a “nonsensitive” surface) mer on any sensitive surface (i.e., Without fouling any that does not cause fouling of any element of the system if sensitive surface). This can eliminate the need to clean (or excess polymer is formed thereon. Thus, the system is less open for cleaning) the reactor system after the polymer coat subject to fouling by polymer coating material formed on any ing-forming polymerization reaction (and before subsequent said “nonsensitive” surface (during performance of the operation of the system to perform a post-coating polymer method or during a polymerization step folloWing perfor ization reaction), and/or the need to clean (or open for clean mance of the method) than by polymer coating material ing) the reactor system after the step of applying the solution formed on any said “sensitive” surface in the folloWing sense: catalyst (and optionally also subsequent oxidization of the during post-coating operation of the reactor system (i.e., applied catalyst) and before the polymer coating-forming operation after formation of the polymer coating on each polymerization reaction. For example, the zinc coating may sensitive and nonsensitive surface) the system can operate be applied so as to prevent formation of more than an accept acceptably if a polymer coating of a ?rst thickness (or ?rst able amount of polymer on each sensitive surface (e.g., to average thickness) has been formed on the nonsensitive sur prevent fouling of the distributor plate and/or compressor face, but the system cannot operate acceptably With a polymer With polymer). The zinc coating may be applied (and the other coating of the ?rst thickness (or the ?rst average thickness) method steps performed) so as to form less polymer on each has been formed on at least one said sensitive surface. In other sensitive surface than on each nonsensitive surface (e. g., the Words, the system is subject to fouling (of a type that prevents polymer coating formed on each sensitive surface is thinner acceptable post-coating operation of the system) if a polymer or has smaller average thickness than that formed on each coating of the ?rst thickness or average thickness has been nonsensitive surface). formed on at least one sensitive surface, Whereas the system is [0107] The inventors have performed tests using iron foil not subject to such fouling if a polymer coating of the same coupons to simulate the effects of different methods of chro thickness or average thickness has been formed on each non mocene deposition on the coupons and subsequent formation sensitive surface. In typical ?uidized bed polymerization of polymer coatings on the coupons by exposing the coupons reactor systems, surfaces of distributor plates, coolers, on Which catalyst has been deposited (“treated” coupons) to recycle gas lines, and compressor bases are likely to be “sen ethylene and a poison scavenger/cocatalyst (e.g., tri-ethyla sitive” surfaces, and reactor bed Walls are likely to be “non luminum (TEAL) or another aluminum alkyl) and perform sensitive” surfaces (in such systems, distributor plates, cool ing a polymerization reaction catalyzed by the deposited ers, recycle gas lines, and compressor bases are more chromocene and the poison scavenger/cocatalyst. Test results vulnerable to fouling by excessive polymer material than are are shoWn in FIG. 6 and Table 1 below. reactor bed Walls). [0108] The metal foil coupons Were coated With chro [0106] In the embodiments noted in the previous para mocene by one of tWo methods described beloW: vapor or graph, the invention is a method for treating interior surfaces liquid deposition. The coupons Were rectangular in shape, of a ?uidized bed polymerization reactor system, said sur measuring 1x1 .5 inches (2.2><3.3 cm), and Were composed of faces including at least one sensitive surface (e. g., a distribu 99.5 pure iron (Fe). tor plate surface, cooler surface, compressor surface, and/ or a [0109] Vapor deposition of the solution catalyst on the cou recycle line surface) and at least one nonsensitive surface pons Was performed as folloWs. A solution of chromocene in (e.g., a reactor bed Wall or portion thereof), said method toluene Was prepared in a dry box by dissolving 80 mg of including the steps of: (a) applying a zinc coating (e.g., a solid, poWdered chromocene in 2 milliliters of toluene. This coating of zinc-based paint) to at least one said sensitive solution Was then transferred to a crystallization dish, Which surface (e.g., to each said sensitive surface) but not to at least measured approximately 10 cm in diameter and 5 cm in one said nonsensitive surface (e.g., not to any said nonsensi depth. The toluene Was removed With a nitrogen purge to tive surface); and (b) after step (a), applying a solution cata produce a thin, dry coating of chromocene at the bottom of the lyst at least substantially uniformly and in liquid form (e. g., in crystallization dish. After recording their tare Weights, six foil the form of liquid droplets of the solution catalyst) to each coupons Were taped to an aluminum foil, Which Was then said sensitive surface and each said nonsensitive surface. In placed over the top of the dish, exposing the bottom surfaces some such embodiments, the catalyst component of the solu of the coupons to the chromocene in the dish. The chro tion catalyst is or includes a CCC. For example, the catalyst mocene Was sublimed from the crystallization dish by heating component of the solution catalyst is or includes chromocene the dish on a hot plate at 100° C. for 30 minutes. The coupons in some preferred embodiments. Typically, the applied solu Were then removed from the crystallization dish and Weighed tion catalyst is dried (or alloWed to dry) to leave a dry coating again to determine the amounts of chromocene that had been of catalyst on each said nonsensitive surface (and typically deposited (or adsorbed) on the surface. Measured chro also each said sensitive surface) and a polymerization reac mocene content on several coupons prepared by this method tion (catalyzed by the catalyst) is then performed to form on ranged from approximately 1 to 7 milligrams, as shoWn by the each said nonsensitive surface (and optionally also each said diamond-shaped symbols plotted in FIG. 6. sensitive surface) a polymer coating that reliably functions as [0110] Liquid deposition of the solution catalyst on the an insulating layer that reduces static charging in the reactor coupons Was performed as folloWs. An 8 Wt. solution of system (and thereby reduces the potential for sheeting) during chromocene in toluene Was prepared in a nitrogen purged dry subsequent polymerization reactions in the reactor system. box by adding 1.88 grams of solid, poWdered chromocene to Preferably, the steps are performed such that the polymer 25 milliliters of toluene. For each coupon sample prepared by coating formed on each nonsensitive surface reliably func this method, 0.1 milliliters of this solution (containing tions as an insulating layer that reduces static charging in the approximately 7.5 mg of dissolved chromocene) Was With US 2012/0070575 A1 Mar. 22, 2012

draWn by a syringe. The solution Was then added drop Wise to the amount of polymer coated Was increased from 0.110 to the upper surface of a coupon sample (after recording its tare 0.60 grams When the reaction time Was increased from 6 to 38 Weight) to produce an evenly distributed solution coating. hours. The toluene Was then removed With a nitrogen purge. The coupon Was then heated in a beaker at 70° C. for 20 minutes. TABLE 1 The coupon Was then Weighed again to determine the amount Average amount of polymer (in grams) coated on coupons in coupon tests of chromocene that had been deposited on the surface. The measured chromocene content on several coupons prepared Polymerization Liquid Deposition Vapor Deposition by this method ranged from approximately 2 to 11 milli Reaction Time (hrs) of Solution Catalyst of Solution Catalyst grams, as shoWn by the square-shaped symbols plotted in 6 0.110 g NA FIG. 6. 16 0.067 g 0.012 g 38 0.260 g 0.028 g. [0111] Prior to each polymerization experiment, a different one of the chromocene coated coupons (prepared by either the vapor or liquid deposition method) Was exposed to ambi [0116] In some of the embodiments described herein, the ent air for 30 minutes to oxidize the chromocene. The coupon solution catalyst is a chromium-containing compound in Was then placed in an autoclave reactor, Which Was then solution. In some such embodiments, the chromium may be purged With substantially pure ethylene to remove atmo present in the reactor at a valence of plus 2 or 3 (the chromium spheric air and moisture, and heated to 90° C. The ethylene may be fed in a 2 to 3 valence or converted to a 2 to 3 valence pressure in the reactor Was then raised to 100 psig (790 kPa), after being introduced). Chromium-containing compounds and the reactor Was then charged With 1.0 mmol of TEA1 to may include, but are not limited to bis(cyclopentadienyl) initiate reaction. The ethylene pres sure Was then immediately chromium (II) compounds having the folloWing formula: raised to 150 psig (1,130 kPa), and maintained for 16 hours (or in some cases 8 or 38 hours as indicated in FIG. 6) to alloW polymer to groW (i.e., polymerize) on the surface of the iron (Run, (RN) foil coupons. The reactor Was then vented, and the coupon 1 C, K\ Was removed and Weighed to determine the amount of poly J L mer that had been produced. [0112] FIG. 6 shoWs a comparison of the polymer produced on the chromocene treated coupons, as prepared by the tWo Wherein R' and R" may be the same or different C1 to C20 deposition methods. The samples produced by vapor deposi inclusive, hydrocarbon radicals, and n' and n" may be the tion are shoWn as the diamond-shaped symbols in FIG. 6. The same or different integers of 0 to 5, inclusive. samples produced by liquid deposition are shoWn as the [0117] The R' and R" hydrocarbon radicals may be satu square-shaped symbols. It is clear from FIG. 6 that, on aver rated or unsaturated, and may include aliphatic, alicyclic and age, much more polymer Was produced by the solution depo aromatic radicals such as methyl, ethyl, propyl, butyl, pentyl, sition method. At equivalent polymerization conditions (16 cyclopentyl, cyclohexyl, allyl, phenyl and naphthyl radicals. hours of reaction), the coupons treated by solution deposition Other speci?c compounds that may be suitable include chro produced an average of 0.067 grams of polymer, Whereas the mic acetyl acetonate, chromic nitrate, chromous or chromic coupons treated by vapor deposition produced an average of acetate, chromous or chromic chloride, chromous or chromic approximately 0.012 grams of polymer. The amount of poly bromide, chromous or chromic ?uoride, chromous or chro mer coated using liquid deposition of solution catalyst Was mic sulfate, and polymerization catalysts produced from thus increased (on the average) by a large factor relative to the chromium compounds Where the chromium may be present amount produced using vapor deposition of the catalyst. in the plus 2 or 3 valence state. [0113] The increased amount of polymer coated on the [0118] Some of the embodiments described herein include coupons using liquid deposition of solution catalyst Was not the steps of introducing into a reactor system a solution cata simply the result of higher concentrations of chromocene lyst including about 1 to about 8 Weight percent (Wt %) deposited on the surface of the coupons. As can be seen in chromium-containing compound dissolved in an inert sol FIG. 6, increased amounts of polymer Were produced by the vent, based upon total Weight, and applying the solution cata solution deposition method over the full range of chromium lyst at least substantially uniformly and in liquid form to the concentrations tested. This may be because the chromocene bed Wall (and optionally also at least one other interior sur deposited by liquid deposition has (for some reason) more face) of the reactor system. In some embodiments, the solu catalytic activity than chromocene deposited by vapor depo tion catalyst may contain less than about 6 Wt %, or less than sition. about 5 Wt % chromium-containing compound in an inert [0114] It is apparent from FIG. 6 that the amount of poly solvent, based upon the total Weight. One inert solvent that mer produced (using catalyst deposition by either method) may be used is toluene. Was independent of the amount of the chromocene deposited [0119] The amount of chromium compound utilized in the on the coupons (i.e., the chromocene loading). In other Words, process should be su?icient to effect the desired result, and the catalytic activity appears to depend on the method of the amount can be determined Without undue experimenta deposition, and not on the chromocene loading. tion. In any of the embodiments described herein, the amount [0115] The amount of polymer coated on the coupons of chromium compound introduced into the ?uidized bed appears to depend on the time that the coupons Were exposed reactor may be greater than about 0.0031 lbs of chromium to TEA1 and ethylene, as shoWn in Table 1 beloW. For containing compound per square foot (0.015 kgs/m2) of sur example, in the case of liquid deposition of solution catalyst, face area to be treated. In other embodiments, greater than