Alkylation of Aromatic Substrates and Transalkylation Process - DocsLib

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(19) &

(11) EP 2 110 368 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 21.10.2009 Bulletin 2009/43 C07C 2/66 (2006.01) C07C 6/12 (2006.01) C07C 15/073 (2006.01) C07C 15/02 (2006.01) (21) Application number: 08290392.3

(22) Date of filing: 18.04.2008

(84) Designated Contracting States: (72) Inventor: Cary, Jean-Bernard AT BE BG CH CY CZ DE DK EE ES FI FR GB GR 76600 Le Havre (FR) HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT RO SE SI SK TR (74) Representative: Neel, Henry et al Designated Extension States: Total Petrochemicals Research Feluy AL BA MK RS Zone Industrielle C 7181 Seneffe (Feluy) (BE) (71) Applicant: Total Petrochemicals France 92047 Paris La Défense Cedex (FR)

(54) Alkylation of aromatic substrates and transalkylation process

(57) The present invention relates to a process for embodiment of the alkylation process the aromatic sub- the alkylation of an aromatic substrate and to a process strate is benzene and the alkylating agent in ethylene. In for the transalkylation of polyalkylated aromatic compo- an advantageous embodiment of the transalkylation nents, wherein the nitrogen containing compounds im- process the aromatic substrate is benzene and the poly- purities in the aromatic substrate feedstock and/or the alkylated aromatic component is diethylbenzene. alkylating agent feedstock are monitored in a range 15 wppb-35 wppm by dry colorimetry. In an advantageous EP 368 2 110 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 110 368 A1 2

Description verting essentially all olefinic compounds contained therein by hydrogenation; [Field of the invention] (c) contacting the thus treated aromatic-rich stream from (b) with an olefin-containing stream comprising [0001] The present invention relates to the alkylation 5 at least one olefin selected from the group consisting of aromatic substrates and related transalkylation proc- of ethylene, propylene, and butylene, wherein the ess. The alkylation of aromatic substrates such as ben- molar ratio of the olefin(s) to said aromatic hydrocar- zene to produce alkylated aromatics such as ethylben- bon is not less than 1 in the presence of a catalyst zene and diethylbenzene are known in the art. More pre- comprising zeolite beta, under alkylation conditions, cisely the invention relates to the monitoring of the nitro- 10 whereby mono and polyalkylated aromatics are gen containing compounds impurities in the aromatic formed; and substrate feedstock and/or in the alkylating agent feed- (d) separating said mono and polyalkylated aromat- stock. The transalkylation of polyalkylated aromatics ics formed in (c) from the remaining hydrocarbons. such as diethylbenzene with an aromatic substrate such as benzene to produce alkylated aromatics such as ethyl- 15 [0004] At col 6 lines 48-53 is mentioned that the olefins benzene is known in the art. The present invention also may be present in admixture with hydrogen, methane, relates to the monitoring of the nitrogen containing com- C2 to C4 paraffins, but it is usually preferable to remove pounds impurities in the aromatic substrate feedstock of dienes, acetylenes, sulfur compounds or basic nitrogen said transalkylation process. compounds (NH3 or amines) which may be present in 20 the olefin feedstock stream, to prevent rapid catalyst de- [Background of the invention] activation. [0005] US 6 617 482 describes a process for removing [0002] Alkylation and transalkylation processes using polar compounds from an aromatic feedstock which con- catalysts are often subject to catalyst regeneration and tains polar compounds and which is then used in an replacement requirements resulting from poisoning of 25 alkylation process. The process comprises contacting the catalyst by one or more impurities contained in the the feedstock in an adsorption zone at a temperature of hydrocarbon feedstock. In many cases, catalyst devel- less than or equal to 130°C with an adsorbent selective opments, e.g. to reduce coke-forming and other by-prod- for the adsorption of said polar compounds and compris- uct reactions, have progressed to the stage where poi- ing a molecular sieve having pores and/or surface cavi- soning by feedstock impurities is the primary reason that 30 ties with cross-sectional dimensions greater than 5.6 catalyst performance deteriorates which forces the cat- Angstroms. A treated feedstock substantially free of said alyst to be replaced or regenerated. Aromatics alkylation polar compounds is withdrawn from the adsorption zone processes employing molecular sieve catalysts can be and fed to an alkylation zone for contact under liquid conducted in either the vapor phase or the liquid phase. phase alkylation conditions with an alkylating agent in However, in view of the improved selectivity and de- 35 the presence of an alkylation catalyst. More particularly, creased capital and operating costs associated with liq- this prior art relates to a liquid phase aromatics alkylation uid phase operation, most commercial alkylation proc- process which includes subjecting the aromatic feed- esses now operate under at least partial liquid phase stock to a pretreatement step for the selective removal conditions. Unfortunately, one disadvantage of operating of polar contaminants that poison aromatic alkylation cat- under liquid phase conditions is that the molecular sieve 40 alysts. Such contaminants include nitrogen, sulfur, and catalysts tend to be more sensitive to the presence of oxygen containing compounds, particularly those that impurities in the feedstocks, particularly polar com- boil in the same ranges as benzene, toluene or xylenes. pounds such as nitrogen compounds. Such impurities [0006] US 2005 0143612 describes a process for the reduce the acid activity of the catalyst and hence de- production of alkyl aromatic compounds wherein aromat- crease the cycle time between required regenerations of 45 ic compounds which may be treated for removal of del- the catalyst. Various processes have been developed for eterious substances are reacted with olefin compounds, removal of such impurities prior to contact with the cat- which may also be treated for contaminant removal, in alyst. In the following prior arts there are description of the presence of acidic zeolite catalyst(s) to produce the said impurities as well as processes to remove these desired alkyl aromatic compound(s). The aromatic and impurities. 50 preferably also the olefin feeds are treated substantially [0003] US 6 002 057 describes a process for the alkyla- to remove contaminants, particularly the nitrogen com- tion of an aromatic hydrocarbon contained in a hydrocar- pounds contained therein, before they are brought to- bon stream comprising: gether for reaction in the presence of the zeolite catalyst (s). The feed pretreatment for removal of nitrogen com- (a) separating essentially all aromatics other than 55 pounds significantly improves the run length and life of said aromatic hydrocarbon from said hydrocarbon the acidic zeolite catalyst(s). A specific object of this prior stream, thereby forming an aromatic-rich stream; art is to provide methods and apparatus for treating an (b) treating said aromatic-rich stream of (a) by con- olefin or aromatic feedstock for removal of organic or

2 3 EP 2 110 368 A1 4 inorganic nitrogen compounds in preparation for a cata- sponse in time, many such apparatus can be used in lytic alkylation or transalkylation process. In accordance parallel and a measurement is launched e.g. every with said prior art, it has been found that nitrogen-con- minute or every ten seconds. Should the impurities are taining impurities in one or both feedstocks may neutral- found to be higher than a requested level the reactor ize the acidic active sites on the acidic zeolite catalyst 5 containing the catalyst can be temporarily by-passed. and thereby reduce catalyst activity and its ability to effect the desired reaction. Long-term accumulation of these [Brief summary of the invention] nitrogen-containing impurities on the catalyst gradually reduces catalyst activity to the point where plant perform- [0010] The present invention is a process for the ance becomes unacceptable, requiring that the plant be 10 alkylation of an aromatic substrate comprising: shutdown to reactivate, regenerate, or replace the catalyst. (a) providing an alkylation reaction zone containing [0007] US 7199275 relates to a process for alkylation an alkylation catalyst; of an aromatic hydrocarbon stream comprising impurities (b) introducing a feedstock comprising an aromatic in which said impurities are removed in a pretreatment 15 substrate and an alkylating agent into the inlet of said system having a first stage, a second stage located down- alkylation reaction zone and into contact with said stream of said first stage and a cycle length, said process alkylation catalyst; comprising the steps of: (c) operating said alkylation reaction zone at temperature and pressure conditions to cause alkylation (a) contacting the aromatic hydrocarbon stream with 20 of said aromatic substrate in the presence of said a first molecular sieve which is 13X in said first stage alkylation catalyst to produce an alkylation product of said pretreatment system, to remove at least a comprising a mixture of said aromatic substrate and portion of said impurities, to produce a partially treat- monoalkylated and polyalkylated aromatic compo- ed aromatic hydrocarbon stream; nents; (b) contacting said partially treated aromatic hydro- 25 (d) withdrawing the alkylation product from said carbon stream with a second molecular sieve which alkylation reaction zone; wherein is 4A in a second stage of said pretreatment system to remove substantially all of the remaining portion the nitrogen containing compounds impurities in the ar- of said impurities, and to produce a fully treated aromatic substrate or in the alkylating agent or both in the omatic hydrocarbon stream; and 30 aromatic substrate and in the alkylating agent are mon- (c) contacting said fully treated aromatic hydrocar- itored in a range 15 wppb-35 wppm by dry colorimetry. bon stream with an alkylating agent in the presence [0011] In an advantageous embodiment the alkylation of an alkylation catalyst and under alkylation condi- reaction zone is operated in the liquid phase. tions, to produce an alkylated aromatic hydrocarbon [0012] In another embodiment the aromatic substrate stream; and wherein said cycle length of said pre- 35 is benzene and the alkylating agent is ethylene. treatment system is greater than said cycle length [0013] The present invention also relates to a process using said first stage of said pretreatment system for the transalkylation of polyalkylated aromatic compo- alone or said second stage of said pretreatment sys- nents comprising : tem alone. 40 (a) providing a transalkylation reaction zone contain- [0008] In a preferred embodiment the process further ing a transalkylation catalyst; comprises the step of contacting said alkylating agent of (b) introducing a feedstock comprising at least a step (c) with a third molecular sieve, to produce a treated polyalkylated aromatic component deriving from an alkylating agent, and contacting said treated alkylating aromatic substrate into the inlet of said transalkyla- agent with said treated aromatic hydrocarbon stream of 45 tion reaction zone and into contact with said step (b), to produce said alkylated aromatic hydrocarbon transalkylation catalyst; stream of step (c). (c) supplying an aromatic substrate to said [0009] However the above prior arts are silent on how transalkylation zone, said aromatic substrate being to check these impurities in an industrial process. It has the same as the one of step (b); now been discovered that by dry colorimetry it was pos- 50 (d) operating said transalkylation zone at tempera- sible to get in less than 5 minutes the amount of the ni- ture and pressure conditions to cause disproportion- trogen containing compounds impurities in the aromatic ation of said polyalkylated aromatic components to substrate or in the alkylating agent. A sample of the feed- produce a disproportionation product having a re- stock to be analyzed is vaporized, unless it is available duced polyalkylated aromatic content and an en- under gasous phase, and is sent through a porous sub- 55 hanced monoalkylated aromatic content; strate carrying a reagent which changes color in propor- (e) withdrawing the disproportionation product from tion with the impurities. An electronic device converts the said transalkylation zone; color to the amount of impurities. To improve the re-

3 5 EP 2 110 368 A1 6 wherein 5,569, 805 (Beck), each of which is incorporated herein the nitrogen containing compounds impurities in the ar- by reference. MCM-68 and its use for the production of omatic substrate are monitored in a range 15 wppb-35 alkyl aromatics are described in U.S. Pat. No. 6,049,018 wppm by dry colorimetry. (Calabro), which is incorporated herein by reference. [0014] In an advantageous embodiment the aromatic 5 [0019] The use of tungstate modified zirconia to cata- substrate is benzene and the polyalkylated aromatic lyze the synthesis of alkyl aromatics is described in U.S. component is diethylbenzene. Pat. No. 5,563,311 (Chang), which is incorporated herein by reference. U.S. Pat. No. 5,081, 323 (Innes), which is [Detailed description of the invention] incorporated herein by reference, teaches a liquid phase 10 alkylation or transalkylation process using zeolite beta. [0015] As regards the catalysts that can be used for Production of cumene over zeolite Y is described in U.S. alkylation of benzene with propylene and also for Pat. No. 5,160, 497 (Juguin) and U.S. Pat. No. 5,240,889 transalkylation of benzene and polyisopropylbenzenes (West), which are incorporated herein by reference. U.S. in liquid phase include zeolite beta, zeolite Y, zeolite ome- Pat. No. 5,030,786 (Shamshoum) and U.S. Pat. No. ga, ZSM-5, ZSM-12, ITQ-1, ITQ-2, ERB-3, SSZ-25, 15 5,980,859 (Gajda), and European patent 0,467,007 (But- MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, MCM- ler), which are incorporated herein by reference, describe 68, faujasite, mordenite, porous crystalline magnesium the production of alkyl aromatic compounds with zeolite silicates, and tungstate modified zirconia, all of which are Beta, zeolite Y, and zeolite Omega U.S. Pat. No. known in the art. 5,522,984 (Gajda), U.S. Pat. No. 5,672,799 (Perego), [0016] Catalysts that can be used for alkylation of ben- 20 U.S. Pat. No. 5,980,859 (Gajda), and U.S. Pat. No. zene with ethylene and transalkylation of benzene and 6,162,416 (Gajda), which are incorporated herein by ref- polyethylbenzenes in liquid phase processes include ze- erence, teach the production of cumene with zeolite beta. olite beta, zeolite Y, zeolite omega, ZSM-5, ZSM-12, ITQ- Use of zeolite Mordenite in production of monoalkylated 1, ITQ-2, ERB-3, SSZ-25, MCM-22, MCM-36, MCM-49, benzene such as cumene and ethylbenzene is described MCM-56, MCM-58, MCM-68, faujasite, mordenite, po- 25 in U.S. Pat. No. 5, 198,595 (Lee), which is incorporated rous crystalline magnesium silicates, and tungstate mod- herein by reference. Production of ethylbenzene with ex ified zirconia. situ selectivated zeolite catalyst is described in U. S. Pat. [0017] Most of these catalysts are described in the fol- No. 5,689,025 (Abichandani), which is incorporated lowing patents : WO 2007/081923, EP 0485683, EP herein by reference. Production of ethylbenzene with 0467007, EP 0507761, EP 1 691 923, EP 0 826 653, EP 30 ZSM-5 is described in U.S. Pat. No. 5,157,185 (Chu), 0 733 608, EP 0 726 242, EP 0 844 023, EP 0 879 809, which is incorporated herein by reference. EP 943594, EP 1043296, EP 1059277, EP 1002778, EP [0020] Production of ethylbenzene over intermediate 1031549, US 6268305, EP 1188734, EP 1211233, EP pore size zeolites is described in U.S. Pat. No. 3,751,504 1208907, EP 1556318, EP 1546071, EP 1727860, EP (Keown), U.S. Pat. No. 4, 547,605 (Kresge), and U.S. 1581466, EP 1807201, EP1851184, the content of each 35 Pat. No. 4,016,218 (Haag), which are incorporated herein is incorporated by reference in the present application. by reference. U.S. Pat. No. 4,169,111 (Wight) and U.S. [0018] MCM-22 and its use to catalyze the synthesis Pat. No. 4,459,426 (Inwood), which are incorporated of alkyl aromatics are described, for example, in U.S. Pat. herein by reference, disclose production of ethylbenzene No. 4,954,325 (Rubin), U.S. Pat. No. 4,992,606 (Kush- over large pore size zeolites such as zeolite Y. Synthesis nerick), U.S. Pat. No. 5,077,445 (Le), U.S. Pat. No. 40 of zeolite ZSM-12 is described in U.S. Pat. No. 5, 021,141 5,334,795 (Chu), and U.S. Pat. No. 5,900,520 (Maz- (Rubin), which is incorporated herein by reference. A zone), each of which is incorporated herein by reference. process for ethylbenzene production over zeolite ZSM- MCM-36 and its use in the synthesis of alkyl aromatics 12 is described in U.S. Pat. No. 5,907,073 (Kumar), which are described in U.S. Pat. No. 5,250,277 (Kresge), U.S. is incorporated herein by reference. Production of ethyl- Pat. No. 5,292,698 (Chu), and U.S. Pat. No. 5,258,565 45 benzene over zeolite Mordenite is described in U.S. Pat. (Kresge), each of which is incorporated herein by refer- No. 5, 430,211 (Pogue), which is incorporated herein by ence. MCM-49 and its use in the synthesis of alkyl aro- reference. Liquid phase synthesis of ethylbenzene with matics are described in U.S. Pat. No. 5,236,575 (Ben- zeolite Beta is described in U.S. Pat. No. 4,891,458 nett), U.S. Pat. No. 5,493,065 (Cheng) and U.S. Pat. No. (Innes) and U.S. Pat. No. 6,060,632 (Takamatsu), which 5, 371,310 (Bennett), each of which is incorporated here- 50 are incorporated herein by reference. U.S. Pat. No. in by reference. MCM-56 and its use to catalyze the syn- 4,849,569 (Smith), U.S. Pat. No. 4,950,834 (Argan- thesis of alkyl aromatics are described in U.S. Pat. No. bright), U.S. Pat. No. 5,086,193 (Sy), U.S. Pat. No. 5,362,697 (Fung), U.S. Pat. No. 5,453,554 (Cheng), U.S. 5,113,031 (Sy), and U.S. Pat. No. 5,215,725 (Sy), which Pat. No. 5,536,894 (Degnan), U.S. Pat. No. 5,557,024 are incorporated herein by reference, teach various sys- (Cheng), and U.S. Pat. No. 6,051,521 (Cheng), each of 55 tems for the catalytic distillation production of alkylated which is incorporated herein by reference. MCM-58 and aromatic compounds, including ethylbenzene and its use for the production of alkyl aromatics are described cumene. in U.S. Pat. No. 5,437,855 (Valyocsik) and U.S. Pat. No. [0021] The term "aromatic" in reference to the alkylat-

4 7 EP 2 110 368 A1 8 able compounds which are useful herein is to be under- butanols, and the pentanols; aldehydes such as formal- stood in accordance with its art-recognized scope which dehyde, acetaldehyde, propionaldehyde, butyraldehyde, includes alkyl substituted and unsubstituted mono-and and n-valeraldehyde; and alkyl halides such as methyl polynuclear compounds. Compounds of an aromatic chloride, ethyl chloride, the propyl chlorides, the butyl character which possess a heteroatom (e.g., N or S) are 5 chlorides, and the pentyl chlorides, and so forth. also useful provided they do not act as catalyst poisons [0024] Mixtures of light olefins can also be useful as under the reaction conditions selected. Substituted aro- alkylating agents in the alkylation process of this inven- matic compounds which can be alkylated herein must tion. Accordingly, mixtures of ethylene, propylene, possess at least one hydrogen atom directly bonded to butenes, and/or pentenes which are major constituents the aromatic nucleus. The aromatic rings can be substi- 10 of a variety of refinery streams, e.g., fuel gas, gas plant tuted with one or more alkyl, aryl, alkaryl, alkoxy, aryloxy, off-gas containing ethylene, propylene, etc., naphtha cycloalkyl, halide, and/or other groups which do not in- cracker off-gas containing light olefins, refinery FCC pro- terfere with the alkylation reaction. Suitable aromatic hy- pane/propylene streams, etc., are useful alkylating drocarbons include benzene, naphthalene, anthracene, agents herein. naphthacene, perylene, coronene, and phenanthrene. 15 [0025] Typical aromatic alkylation reactions which may [0022] Generally the alkyl groups which can be present be improved by the present invention include obtaining as substituents on the aromatic compound contain from ethylbenzene from the reaction of benzene with ethylene, 1 to about 22 carbon atoms and preferably from about 1 cumene from the reaction of benzene with propylene, to 8 carbon atoms, and most preferably from about 1 to ethyltoluene from the reaction of toluene with ethylene, 4 carbon atoms. Suitable alkyl substituted aromatic com- 20 and cymenes from the reaction of toluene with propylene. pounds include toluene; xylene; isopropylbenzene; nor- [0026] The alkylation process of this invention is con- mal propylbenzene; alpha-methylnaphthalene; ethyl- ducted such that the organic reactants, i.e., the alkylat- benzene; cumene; mesitylene; durene; p-cymene; butyl- able aromatic compound and the alkylating agent, are benzene; pseudocumene; o-diethylbenzene; m-diethyl- brought into contact with an alkylation catalyst in a suit- benzene; p-diethylbenzene; isoamylbenzene; isohexyl- 25 able reaction zone such as, for example, in a flow reactor benzene; pentaethylbenzene; pentamethylbenzene; containing a fixed bed of the catalyst composition, under 1,2,3,4-tetraethylbenzene; 1,2,3,5-tetramethylbenzene; effective alkylation conditions. Such conditions include a 1,2,4-triethylbenzene; 1,2,3-trimethylbenzene, m-butyl- temperature of from about 0°C to about 500°C, and pref- toluene; p-butyltoluene; 3,5-diethyltoluene; o-ethyltolu- erably between about 50°C and about 250°C; a pressure ene; p-ethyltoluene; m-propyltoluene; 4-ethyl-m-xylene; 30 of from about 0.2 to about 250 atmospheres; and pref- dimethylnaphthalenes; ethylnaphthalene; 2,3-dimethyl- erably from about 5 to about 100 atmospheres, a molar anthracene; 9-ethylanthracene; 2-methylanthracene; o- ratio of alkylatable aromatic compound to alkylating methylanthracene; 9,10-dimethylphenanthrene; and 3- agent of from about 0.1:1 to about 50:1, and preferably methyl-phenanthrene. Higher molecular weight alkylar- can be from about 0.5:1 to about 10:1; and a feed weight omatic hydrocarbons can also be used as starting mate- 35 hourly space velocity (WHSV) of between about 0.1 and rials and include aromatic hydrocarbons such as are pro- 500 hr-1, preferably between 0.5 and 100 hr-1. duced by the alkylation of aromatic hydrocarbons with [0027] The reactants can be in either the vapor phase olefin oligomers. Such products are frequently referred or the liquid phase and can be neat, i.e., free from inten- to in the art as alkylate and include hexylbenzene, non- tional admixture or dilution with other material, or they ylbenzene, dodecylbenzene, pentadecylbenzene, hexy- 40 can be brought into contact with the zeolite catalyst com- ltoluene, nonyltoluene, dodecyltoluene, pentadecytolu- position with the aid of carrier gases or diluents such as, ene, etc. Very often alkylate is obtained as a high boiling for example, hydrogen or nitrogen. When benzene is fraction in which the alkyl group attached to the aromatic alkylated with ethylene to produce ethylbenzene, the nucleus varies in size from about C6 to about C12. Refor- alkylation reaction may be carried out in the liquid phase. mate, especially reformate containing substantial quan- 45 Suitable liquid phase conditions include a temperature tities of benzene, toluene, and/or xylene, would also con- between 150°C and 316°C, preferably between 205°C stitute a useful feed for the alkylation process of this in- and 260°C; a pressure up to about 3000 psig (20875 vention. kPa); preferably between 400 and 800 psig (2860 and [0023] The alkylating agents which are useful in the 5600 kPa), a space velocity between about 0.1 h-1 and process of this invention generally include any aliphatic 50 20 h-1 WHSV, preferably between 1 and 6 h-1 WHSV, or aromatic organic compound having one or more avail- based on the ethylene feed; and a ratio of the benzene able alkylating aliphatic groups capable of reaction with to the ethylene in the alkylation reactor from 1:1 to 30:1 the alkylatable aromatic compound, preferably with the molar, preferably from about 1:1 to 10:1 molar. alkylating group possessing from 1 to 5 carbon atoms. [0028] As regards the dry colorimetry analysis the prin- Examples of suitable alkylating agents are olefins such 55 ciple has been explained above. A sample of the feed- as ethylene, propylene, the butenes, and the pentenes; stock to be analyzed is vaporized, unless it is available alcohols (inclusive of monoalcohols, dialcohols, trialco- under gasous phase, and is sent through a porous sub- hols, etc.) such as methanol, ethanol, the propanols, the strate carrying a reagent which changes color in propor-

5 9 EP 2 110 368 A1 10 tion with the impurities. The liquid sample, if any, can be contact with said alkylation catalyst; vaporized by any means. The porous substrate can be (c) operating said alkylation reaction zone at paper like filter paper. The porous substrate carries a temperature and pressure conditions to cause chemical reagent specific to the nitrogen containing com- alkylation of said aromatic substrate in the pres- pounds impurities and advantageously responds to am- 5 ence of said alkylation catalyst to produce an monia (NH3 or NH4OH), methylamine, dimethylamine, alkylation product comprising a mixture of said ethylamine and trimethylamine. This chemical reagent aromatic substrate and monoalkylated and poly- also reacts positively to H2S but normaly H2S is not alkylated aromatic components; present in the aromatic substrate feed and in the alkylat- (d) withdrawing the alkylation product from said ing agent feed. The color is compared with standart colors 10 alkylation reaction zone; wherein obtained with samples containing known amounts of nitrogen containing compounds (the calibration). Any the nitrogen containing compounds impurities in the means can be used for the comparison. Advantageously aromatic substrate or in the alkylating agent or both an electronic device such as a photo optical system reads in the aromatic substrate and in the alkylating agent the color and by comparison with the standart colors con- 15 are monitored in a range 15 wppb-35 wppm by dry verts the color to the amount of impurities. Advanta- colorimetry. geously the range is 30 wppb-25 wppm. The gas sample to be analyzed flows through the porous substrate car- 2. Process according to claim 1 wherein the alkylation rying the reagent during about 1 to 5 minutes in accord- reaction zone is operated in the liquid phase. ance with the calibration. 20 [0029] To improve the response in time, many such 3. Process according to any one of the preceding apparatus can be used in parallel and a measurement is claims wherein the aromatic substrate is benzene launched e.g. every minute or every ten seconds. Should and the alkylating agent is ethylene. the impurities are found to be higher than a requested level the reactor containing the catalyst can be tempo- 25 4. Process for the transalkylation of polyalkylated aro- rarly by-passed. matic components comprising : By way of example the above analysis can be made by an automatic device supplied by C.I. Analytics in Canada (a) providing a transalkylation reaction zone under the reference Sensi-tape® 7510. containing a transalkylation catalyst; [0030] During operation, the Sensi-Tape® is incre- 30 (b) introducing a feedstock comprising at least mented through a sampling "window" where it is exposed a polyalkylated aromatic component deriving to a metered sample stream. If the target gas is present, from an aromatic substrate into the inlet of said a stain proportional to the concentration develops. Simul- transalkylation reaction zone and into contact taneously, a beam of light is reflected off the exposed with said transalkylation catalyst; portion of the tape and the intensity is measured contin- 35 (c) supplying an aromatic substrate to said uously. As the amount of reflected light decreases due transalkylation zone, said aromatic substrate to stain development, the reduction is sensed by a pho- being the same as the one of step (b); tocell detector as an analog signal. This signal is con- (d) operating said transalkylation zone at tem- verted to a digital format, matched to the gas response perature and pressure conditions to cause dis- curve stored in the analyzer’s permanent memory, and 40 proportionation of said polyalkylated aromatic displayed/ documented as the actual concentration val- components to produce a disproportionation ue. All of these functions are microprocessor controlled. product having a reduced polyalkylated aromat- The use of this spectrophotometric technique, in combi- ic content and an enhanced monoalkylated ar- nation with microprocessor control, provides excellent omatic content; accuracy, repeatability, and detectability of low ppb 45 (e) withdrawing the disproportionation product (parts-per-billion) concentrations. from said transalkylation zone;

wherein Claims the nitrogen containing compounds impurities in the 50 aromatic substrate are monitored in a range 15 1. Process for the alkylation of an aromatic substrate wppb-35 wppm by dry colorimetry. comprising: 5. Process according to claim 4 wherein the aromatic (a) providing an alkylation reaction zone con- substrate is benzene and the polyalkylated aromatic taining an alkylation catalyst; 55 component is diethylbenzene. (b) introducing a feedstock comprising an aromatic substrate and an alkylating agent into the 6. Process according to any one of the preceding inlet of said alkylation reaction zone and into claims wherein the nitrogen containing compounds

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 6002057 A [0003] • US 5371310 A, Bennett [0018] • US 6617482 B [0005] • US 5362697 A, Fung [0018] • US 20050143612 A [0006] • US 5453554 A, Cheng [0018] • US 7199275 B [0007] • US 5536894 A, Degnan [0018] • WO 2007081923 A [0017] • US 5557024 A, Cheng [0018] • EP 0485683 A [0017] • US 6051521 A, Cheng [0018] • EP 0467007 A [0017] [0019] • US 5437855 A, Valyocsik [0018] • EP 0507761 A [0017] • US 5569 A [0018] • EP 1691923 A [0017] • US 805 A, Beck [0018] • EP 0826653 A [0017] • US 6049018 A, Calabro [0018] • EP 0733608 A [0017] • US 5563311 A, Chang [0019] • EP 0726242 A [0017] • US 5081 A [0019] • EP 0844023 A [0017] • US 323 A, Innes [0019] • EP 0879809 A [0017] • US 5160497 A, Juguin [0019] • EP 943594 A [0017] • US 5240889 A, West [0019] • EP 1043296 A [0017] • US 5030786 A, Shamshoum [0019] • EP 1059277 A [0017] • US 5980859 A, Gajda [0019] [0019] • EP 1002778 A [0017] • US 5522984 A, Gajda [0019] • EP 1031549 A [0017] • US 5672799 A, Perego [0019] • US 6268305 B [0017] • US 6162416 A, Gajda [0019] • EP 1188734 A [0017] • US 5198595 A, Lee [0019] • EP 1211233 A [0017] • US 5689025 A, Abichandani [0019] • EP 1208907 A [0017] • US 5157185 A, Chu [0019] • EP 1556318 A [0017] • US 3751504 A, Keown [0020] • EP 1546071 A [0017] • US 4547605 A, Kresge [0020] • EP 1727860 A [0017] • US 4016218 A, Haag [0020] • EP 1581466 A [0017] • US 4169111 A, Wight [0020] • EP 1807201 A [0017] • US 4459426 A, Inwood [0020] • EP 1851184 A [0017] • US 5021141 A, Rubin [0020] • US 4954325 A, Rubin [0018] • US 5907073 A, Kumar [0020] • US 4992606 A, Kushnerick [0018] • US 5430211 A, Pogue [0020] • US 5077445 A, Le [0018] • US 4891458 A, Innes [0020] • US 5334795 A, Chu [0018] • US 6060632 A, Takamatsu [0020] • US 5900520 A, Mazzone [0018] • US 4849569 A, Smith [0020] • US 5250277 A, Kresge [0018] • US 4950834 A, Arganbright [0020] • US 5292698 A, Chu [0018] • US 5086193 A, Sy [0020] • US 5258565 A, Kresge [0018] • US 5113031 A, Sy [0020] • US 5236575 A, Bennett [0018] • US 5215725 A, Sy [0020] • US 5493065 A, Cheng [0018]

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