United States Patent (19 11 Patent Number: 4,914,257 Cohen et al. (45) Date of Patent: Apr. 3, 1990

54 METHOD AND APPARATUS FOR Primary Examiner-Glenn Caldarola RECOVERING HIGH PURITY , Attorney, Agent, or Firm-Robert G. Ladd; William H. HEXANE, TETRACHLORIDE Magidson; Ralph C. Medhurst AND FROM MIXTURES 57 ABSTRACT

75 Inventors: Steven A. Cohen, Naperville; James The- method for separatinga from a mother liquor- - con- 75 H. Lee, Aurora, ,both Nap of Ill.; David B. taining at least two liquids, one of the two liquids in Manley, Rolla, Mo. cluding the steps of: (a) forming a precipitatable complex from one of the 73) Assignee: Amoco Corporation, Chicago, Ill. liquids and a complexing agent; 21 Appl. No.: 197,217 (b) precipitating the precipitatable complex from the method liquor; and 22 Filed: May 23, 1988 (c) recovering the second liquid from the remaining 51 Int. Cl." ...... C08F 4/64 mother liquor. Typically, the two liquid substances 52 U.S. C...... 585/814; 585/817; are tetrahydrofuran and toluene and the complexing 502/104 A agent is titanium tetrachloride. The precipitatable 58 Field of Search ...... 585/702, 703, 814, 817, complex is TiCl4.2C4H8O or TiCl4.C4H8O. Prefera 585/833, 834, 835, 836, 837,855 bly, a cooling step is included in the method to en 56 References Cited St. the removal f the precipitatabe E. uperfractionation of the remaining liquor in distilla U.S. PATENT DOCUMENTS tion columns enables one to recover toluene, hexane, 2,378,733 6/1945 Sensel ...... 585/702 titanium tetrachloride and tetrahydrofuran. An appa 2,732,413 1/1956 Jones et al...... 585/817 ratus for carrying out the method of recovering sol 2,849,511 8/1958 Schaeffer et al. .585/814 o 2,888,496 5/1959 Scott ...... 585/817 X vents in also disclosed. 4,588,704 5/1986 Drake et al...... 502/134 X 4,683,215 7/1987 Bilhou et al...... 502/104 X 12 Claims, 1 Drawing Sheet

EPARATIONSTASE o CATALYST PRODUCING SYSEM COOLMC unt

--2 Tcl. 2THF

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UNIT ric THF

s WI Recovered RECOVER RECOVERED TiCl FE85 HEXANE U.S. Patent Apr. 3, 1990 4.914,257 GEHBAOOBH +H]

ENGÍTIOI

4,914,257 1. 2 H3O, which are then precipitated from the mother li METHOD AND APPARATUS FOR RECOVERNG quor. Also, it has been determined that such precipita HIGH PURITY TOLUENE, HEXANE, TITANIUM tion is enhanced by cooling the mother liquor.contain TETRACHLORIDE AND TETRAHYDROFURAN ing the precipitatable complexes. If required, complex FROM MXTURES ing agent can be added to the mother liquor to promote formation of precipitatable complexes. FIELD OF THE INVENTION The present invention relates to a method and appara SUMMARY OF THE INVENTION tus for recovering toluene, titanium tetrachloride, hex According to the present invention there is provided ane and tetrahydrofuran from mixtures containing these 10 a method for recovering from a mother liquor having materials and higher materials. first and second liquids with close boiling points, one of In carrying out the method, tetrahydrofuran is com the two liquids. The method comprises the steps of: plexed by titanium tetrachloride and the resulting com (a) forming a precipitatable complex from the first plex is removed by precipitation. Relatively high purity liquid and a complexing agent; toluene, hexane, titanium tetrachloride and tetrahydro 15 (b) precipitating the precipitatable complex from the furan are then recovered by superfractionation in distill mother liquor; and lation columns. (c) recovering the other liquid substance from the remaining mother liquor. BACKGROUND OF THE INVENTION The complexing agent can be present in the mother such as hexane and toluene and components 20 liquor or it can be added to the mother liquor; such as tetrahydrofuran and titanium tetrachloride are Typically, for a mother liquor derived from an olefin utilized in a number of chemical processes such as pro polymerization catalyst preparation process, the two cesses for producing the catalysts utilized in the poly liquid substances are tetrahydrofuran and toluene and merization of olefins. the complexing agent is titanium tetrachloride. Then, a It has been found that without recovery and 25 precipitatable complex of TiCl4.xTHF, where x = 1 or recycle the process for producing the catalyst may not 2, is formed. A method for recovering toluene and at be economically feasible or environmentally viable. least one compound selected from the group consisting Heretofore, a batch fractionation process was suggested for recovering the solvents and other components. of tetrahydrofuran and titanium tetrachloride from a However, the interaction between tetrahydrofuran 30 mixture comprising toluene, tetrahydrofuran and tita (THF) and titanium tetrachloride (TiCl4) in a batch nium tetrachloride comprises the steps of: fractionator was unknown. Moreover, it has been deter (a) supplying a mother liquor comprising toluene, mined that recovered toluene must be virtually free of tetrahydrofuran and titanium tetrachloride, said THF in order to be reusable in a process for the produc mother liquor being capable of forming selected tion of an olefin polymerization catalyst. 35 complexes of titanium tetrachloride and tetrahy Furthermore, studies have shown that it is difficult, if drofuran; not impossible, to completely separate THF and hexane (b) cooling the mother liquor to precipitate the se by straight in view of the similar boiling lected complexes of titanium tetrachloride and points of THF and hexane. However, it has been ob tetrahydrofuran from the mother liquor; served (and incorporated into the process of the present 40 (c) removing the precipitate of the selected com invention) that complexes of TiCl4 and THF are insolu plexes from the mother liquor; and ble in hexane even at room temperature. Accordingly, (d) distilling the remaining mother liquor at least once any buildup of THF in the hexane can be treated by to recover toluene and at least one compound se adding TiCl4 and then filtering the liquid to remove the lected from the group consisting of tetrahydrofu resulting solid precipitatable complex. 45 ran and titanium tetrachloride. U.S. Pat. No. 4,588,704 describes a method of com As described by P. M. Hamilton, et al., Journal of the bining suitable portions of organic solvent or diluent American Chemical Society, Volume 75, June 20, 1953, which has been contacted with organoaluminum halide pp. 2881-2883, the compound TiCl4.C4H8O is formed and titanium halide and washed at least once with water when THF is added to an excess of TiCl4 and the con without adverse reactions or the excessive production 50 pound TiCl4.2C4HsO is formed when THF is present in of precipitation or gels and the organic phase of the excess with TiCl4. diluent can subsequently be separated from the water Preferably, cooling is included in the step of precipi phase for further purification and recycle into the pro tating the complex from the mother liquor wherein the cess for production of polymerization catalyst. mother liquor is cooled to about O' C. to enhance the U.S. Pat. No. 4,683,215 describes a process for re 55 removal of the precipitatable complexes. moving one or more contaminants of the formula TiCl Superfractionation of the remaining mother liquor in 3OR, in which R is an or aryl group, from a liquid distillation columns enables one to recover toluene, phase comprising TiCl4, wherein the contaminants are hexane, TiCl4 and/or THF for recycle to a chemical reacted with an organic halide R'COCl in which R" is process such as the production of olefin polymerization an aryl or alkyl group, to precipitate an addition com 60 catalysts. plex of the formula nTiCl4.R'COOR in which n is a Also, according to the present invention there is pro number of from 0.3 to 3.0 and the precipitated complex vided a method for recovering a solvent from a mother is separated from the liquid phase. liquor containing at least tetrahydrofuran and the sol As will be described in greater detail hereinafter, the vent, said method comprising the steps of: method and apparatus of the present invention utilize 65 (a) adding TiCl4 to the mother liquor thereby to form the presence of a complexing or precipitating agent, complexes of TiCl4 tetrahydrofuran; such as TiCl4, in a mother liquor to create precipitatable (b) precipitating the complexes of TiCl4 and tetrahy complexes of THF, such as TiCl4.C4H8O or TiCl4.2C4. drofuran from the mother liquor; and 4,914,257 3 4. (c) recovering the solvent from the remaining mother The resulting distillate is then supplied to a second liquor. Typically, the solvent is hexane. distillation column 50 where TiCl4 is recovered in an Also, according to the present invention there is pro outlet stream 51 and the overhead is then supplied to a vided an apparatus for carrying out the method to re third distillation column 52 where lights, components cover solvents such as toluene and hexane and compo with lower boiling points than toluene, are distilled nents such as THF and/or TiCl4. from the liquid in outlet stream 53 and toluene is recov ered in an outlet stream 54. BRIEF DESCRIPTION OF THE DRAWING The hexane wash in stream or line 24 from the third The drawing, FIG. 1, is a process flow chart of one separation stage 22 is supplied to a third recovery sec embodiment of a process constructed according to the O tion 55 of process 10 and to a distillation column 56 teachings of the present invention for recovering rela therein. The bottoms from the distillation column 56 are tively high purity toluene, hexane and tetrahydrofuran supplied to the first distillation column 48 in the second and TiCl4 from mixtures containing these materials and recovery section 41 of process 10 and hexane is recov other higher boiling point materials from a mother li ered in an distillate outlet stream 57 of distillation col quor derived from an olefin polymerization catalyst 15 umn 56. The hexane wash in stream 24 may optionally preparation process. contain a means for the addition of TiCl4, a means for cooling, and a means for precipitating complexes of DESCRIPTION OF THE PREFERRED TiCl4 and THF. The optional means described above EMBODIMENT can be used when THF is present in the hexane wash In FIG. 1 there is shown, in block form, a process 10 stream. The hexane wash feed stream detailed in Table for recovering toluene, titanium tetrachloride, hexane 1 does not contain THF so that the optional means are and THF from a mother liquor in stream or line 12. not required. X Such mother liquor can be a by-product of a catalyst The method or process 10 of the present invention producing system 14 as shown. utilizes both precipitation and distillation to recover the As shown, the output from the catalyst producing 25 various solvents from complex mixtures in sufficient system 14 is supplied to a first separation stage 16 from purity for reuse in the catalyst producing system 14. which the mother liquor in stream or line 12 is obtained. Moreover, the method of process 10 can be utilized in The mother liquor has a relatively high concentration other environments to economically recover materials. of THF, with toluene, TiCl4 and heavies also present. Valuable materials such as solvents are conserved and The effluent from the first separation stage 16 is sup 30 recycled and noxious waste products are reduced. plied to a second separation stage 18 where a liquid It will be apparent from the foregoing description containing primarily toluene and TiCl4 is separated that the method or process 10 of the present invention from the catalyst into a stream of line 20. The effluent first of all utilizes a complexing agent, namely TiCl4 for from the second separation stage 18 is then supplied to the purpose of forming precipitatable complexes, a third separation stage 22 where a liquid containing 35 namely Ticla THF or TiCl4.2THF, with THF. TiCl4 as primarily hexane is separated into a stream or line 24 to a complexing agent may be present in the mother liquor yield substantially pure catalyst 26 at the outlet from the or TiCl4 may be added to the mother liquor to promote third separation stage 22. the formation of the TiCl4.THF or TiCl4.2THF com The mother liquor in stream or line 12 is fed to a first plex. recovery section 28 of process 10 and to a cooling unit 40 THF cannot be completely removed from mixtures 30 therein where the mother liquor is cooled, preferably of toluene and TiCl4 by distillation because TiCl4 and to a temperature of about 0° C. and this cooled mother THF form complexes which slowly decompose at dis liquor is then supplied to a precipitator 32 where a tillation temperatures. However, the concentration of precipitate of the TiCl4.2THF complex is separated THF in solvent recycle streams can be reduced to ac from the mother liquor in outlet stream 33. 45 ceptably low levels by forming the TiCl4.THF complex By using this technique, almost all of the TiCl4 pres and precipitating this TiCl4.THF complex before distill ent is separated by precipitation as a TiCl4.2THF com lation. plex from the mother liquor. In solvent recovery streams containing THF, TiCl4, The remaining mother liquor is then supplied to a toluene and higher boiling point components referred to preheater 34, heated and then supplied to a first distilla 50 as “heavies” in which THF is present in excess, TiCl4 is tion column 36. In the first distillation column 36, heav removed by the formation and precipitation of a TiCl4 ies, components with higher boiling points than THF and THF complex having the , and toluene, are separated in outlet stream 37 and the TiCl4.2C4H8O, before the removal of the heavies by distilled liquor is then supplied to a second distillation distillation and the separation of THF and toluene by column 38 where toluene is recovered in outlet stream 55 distillation. 39 and THF is recovered in distillate outlet stream 40. In solvent recovery streams containing THF, TiCl4, The liquid containing primarily toluene and TiCl4 toluene and heavy components in which TiCl4 is pres and a minor amount of THF in stream or line 20 ob ent in excess, THF is removed by the formation and tained from the second separation stage 18 is supplied to precipitation of a TiCl4 and THF complex having the a second recovery section 41 of process, 10 and to a 60 chemical formula, TiCl4.C4H8O, before recovery of cooling unit 42 therein where the liquid is cooled to TiCl4 and toluene by distiilation. approximately 0° C. and then supplied to a precipitator The production of the precipitate is enhanced by 44 where a complex of TiCl4.THF forms and is precipi cooling the liquid mixtures containing the complexes to tated out of the liquid in an outlet stream 45. The re approximately 0° C. Some recovery of the precipitate maining liquid is supplied to a preheater 46, heated and 65 can be achieved at higher temperatures, however, then supplied to a first distillation column 48 in the greater efficiency is achieved at approximately 0° C. second section 41 where heavies are removed in stream Furthermore, precipitators 32 and 44 are provided 49. which separate titanium tetrachloride from mother li 4,914,257 5 quor solutions containing THF in excess and THF from TABLE II-continued a solution containing TiCl4 in excess, respectively. Be cause of the similar boiling points of THF and hexane, RECYCLE STREAMS distillation is not a viable alternative for separating THF (g/1000 g of solvent recovery feed) 5 Hexane - - 4.3 from hexane. However, the TiCl4.THF complex is in Toluene 0.9 1924 229.7 soluble in hexane, even at room temperature, such that TiCl4 - 0.2 10.6 any buildup of THF in the hexane is reduced by adding Isopar G - 1.4 - TiCl4 to the liquid mixture and then filtering the result Heavies - 0.5 - ing precipitate from the hexane recovery stream. TOTALS: 18.8 194.6 244.6 A typical catalyst that can be produced by catalyst 10 Recovered Recovered producing system 14 is described in European Pub TiCl4 Hexane from from lished Application No. 0250230, incorporated herein by Distillation Distillation reference. Column 50 Column 56 The process disclosed may be useful for the separa Stream 51 Stream 57 Totals 15 tion of many materials. Examples of materials that could THF - - 18.0 be removed or recovered from the desired recycle Hexane - 37.3 141.6 streams instead of or in addition to THF include: diox Toluene 2.1 t 425.1 ane, furan, tetrahydropyran, methyl-substituted tetrahy TiCl4 254.1 tr 264.9 drofurans, dihydrofurans, and other cyclic ; diiso Isopar G - --- 1.4 propyl , methyl t-butyl ether, diamyl ether, di 20 Heavies - - 0.5 methoxyethane, diglyme, triglyme, and other acyclic TOTALS: 256.2 137.3 851.5 ethers; ketones; nitriles; ; amides; and esters. Sol tr = trace amount present vents, in addition to or in place of toluene and hexane, include but are not limited to: alkanes, such as , TABLE III heptane, octane, par (TM) G, kerosene, etc; cycloal 25 WASTE STREAMS kanes, such as decahydronaphthalene, cyclopentane, (g/1000 g of solvent recovery feed) cyclohexane etc; aromatics such as benzene, ethylben Heavies Heavies in the Zene, xylenes, tetrahydronaphthalene, cumene, isocu from Lights from Outlet from mene, indane, indene, etc; chloroaromatics, such as Distillation Distillation Distillation 30 Column 36 Column 52 Column 48 chlorobenzene, chlorotoluene, dichlorobenzene, etc; Stream 37 Stream 53 Stream 49 and halocarbons such as tetrachloride, trichloro THF - t - ethane, etc. Other complexing agents include ZrCl4, Hexane - 7.2 - HfCl4, VCl4, MgCl2, AlH3, TiCl3, etc. Toluene 7.0 2.3 tr As set forth below, Table 1 details the solvent recov TiCl4 0.1 t 2.7 ery feed streams and the substances therein in 35 Isopar G 19.0 - -- grams/1000 grams of solvent recovery feed. The sub Heavies 36.3 - 1.4 stances present in the solvent recovery streams are TOTALS 62.4 9.5 4.1 Precipitate Precipitate THF, hexane toluene, TiCl4, Isopar G and heavies. from from IsoparTM G is a distillation cut including isoparaffinic 40 Precipitator Precipitator hydrocarbons. Heavies include organic compounds 32 44 with boiling points higher than toluene, hexane, THF or Stream 33 Stream 45 Totals TiCl4 and solids. THF 10.5 3.9 14.4 Hexane -- 0.2 7.4 TABLE I Toluene 15.4 6.7 31.4 SOLVENT RECOVERY FEED STREAMS 45 TiCl4 2.0 17.4 32.2 (g/1,000 g of solvent recovery feed) Isopar G 1.6 - 20.6 Mother TiCl4/ Hexane Heavies 4.8 - 42.5 Liquor Toluene Wash TOTALS 44.3 28.2 48.5 Stream 12 Stream 20 Stream 24 Totals tr = trace amount present THF 28.5 3.9 - 32.4 50 Hexane - 4.4 144.6 149.0 Toluene 215.6 240.3 0.6 456.5 We claim: TiCl4 12.3 269.5 15.2 297.0 1. A method for recovering toluene and at least one Isopar G 22.1 - - 22.1 compound selected from the group consisting of tetra Heavies 41.5 1.5 - 43.0 hydrofuran and titanium tetrachloride from a mixture TOTALS: 320.0 59.6 160.4 1000.0 55 derived from an olefin polymerization catalyst prepara tion process comprising the steps of: Tables II and III below detail the recycle streams and (a) supplying a mother liquor having the capability of waste streams, respectively, based on 1,000 g of solvent forming selected complexes of titanium tetrachlo recovery feed. ride and tetrahydrofuran; 60 (b) cooling the mother liquor to precipitate the se TABLE II lected complexes of titanium tetrachloride and RECYCLE STREAMS tetrahydrofuran from the mother liquor; (g/1000 g of solvent recovery feed) (c) removing the precipitate of the selected com Recovered Recovered Recovered THF from Touene from Toluene from plexes from the mother liquor; and Distillation Distillation Distillation 65 (d) distilling the remaining mother liquor at least once Column 38 Column 38 Column 52 to recover the toluene and at least one compound Stream 40 Stream 39 Stream 54 selected from the group consisting of tetrahydrofu THF 7.9 0.1 t ran and titanium tetrachloride. 4,914,257 7 8 2. The method of claim 1 wherein said cooling step 10. The method of claim 7 wherein said recovery step includes cooling the mother liquor to approximately 0 includes distilling the mother liquor to recover the sol Went. s C. 11. An apparatus for recovering toluene and at least 3. The method of claim 1 wherein the selected com one compound selected from the group consisting of plex has a chemical formula of TiCl4.2C4H8O. tetrahydrofuran and titanium tetrachloride from a mix 4. The method of claim 3 wherein the compound ture derived from an olefin polymerization catalyst recovered in the distillation step is tetrahydrofuran. preparation process, said apparatus comprising: 5. The method of claim 1 wherein the selected com (a) means for supplying a mother liquor having the 10 capability of forming selected complexes of tita plex has a chemical formula of TiCl4.C4H8O. nium tetrachloride and tetrahydrofuran; 6. The method of claim 5 wherein the compound (b) means for cooling the mother liquor to precipitate recovered in the distillation step is titanium tetrachlo the selected complexes of titanium tetrachloride ride. and tetrahydrofuran from the mother liquor; 15 (c) means for removing the precipitate of the selected 7. A method for separating a solvent, from a mother complexes from the mother liquor; and liquor containing at least tetrahydrofuran and the sol (d) means for distilling the remaining mother liquor at vent, said method comprising the steps of: least once to recover the toluene and at least one (a) adding TiCl4 to the mother liquor thereby to form compound selected from the group consisting of complexes of TiCl4 and tetrahydrofuran; tetrahydrofuran and titanium tetrachloride. 12. An apparatus for separating a solvent, from a (b) precipitating the complexes TiCl4 and tetrahydro mother liquor containing at least tetrahydrofuran and furan from the mother liquor; and the solvent, said apparatus comprising: (c) recovering the solvent from the remaining mother (a) means for adding TiCl4 to the mother liquor liquor. 25 thereby to form complexes of TiCl4 and tetrahy 8. The method of claim 7 wherein said solvent is drofuran; (b) means for precipitating the complexes TiCl4 and hexane. tetrahydrofuran from the mother liquor; and 9. The method of claim 7 wherein said precipitating for recovering the solvent from the remaining mother step includes cooling the mother liquor to approxi 30 liquor. mately 0° C. s : : sk ck

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