Extraction of alkyl fluoride from an alkylate hydrocarbon with a leanhf acid

Abstract

IN THE ALKYLATION OF AN ISOPARAFFIN WITH AN OLEFIN IN THE PRESENCE OF HYDROFLUORIC ACID AS CATALYST WHEREIN THE TOTAL FEED STREAM IS CONVERTED IN PART TO ALKYL FLUORIDE, THE ALKYLATION REACTION EFFLUENT STREAM CONTAINING ALKYL FLUORIDE IS CONTACTED WITH LIQUID HYDROGEN FLUORIDE WHICH HAS BEEN TREATED BY COUNTERCURRENT EXTRACTION WITH A STREAM COMPRISING ISOBUTANE, SAID TREATED HYDROGEN FLUORIDE IS USED TO EXTRACT THE ALKYL FLUORIDE FROM THE ALKYLATION REACTION EFFLUENT STREAM AND BOTH THE ALKYL FLUORIDE ENRICHED BUTANE STREAM AND THE ALKYL FLUORIDE ENRICHED HYDROGEN FLUORIDE STREAM ARE RECYCLED TO THE ALKYLATION REACTION ZONE.

Claims

Oct. 23, 1973 T, HUTSON, |R ET AL 3,767,726 EXTRACTION 0F ALKYL FLUORIDE FROM AN ALKYLATE HYDROCARBON WITH A LEAN HF ACID Filed NOV. l1. 1971 Wwf/W ATTORNEYS United States Patent O 3,767,726 EXTRACTION OF ALKYL FLUORIDE FROM AN ALKYLATE HYDROCARBON WITH A LEAN HF ACID Thomas Hutson, Jr., and Cecil O. Carter, Bartlesville, Okla., assignors to Phillips Petroleum Company Filed Nov. 11, 1971, Ser. No. 197,835 Int. Cl. C07c 3/54 U.S. Cl. 260--683A2 8 Claims ABSTRACT OF THE DISCLOSURE In the alkylation of an isoparaflin with an olefin in the presence of hydrofluoric acid as catalyst wherein the total feed stream is converted in part to alkyl fluoride, the alkylation reaction eflluent stream containing alkyl fluoride is contacted with liquid hydrogen fluoride which has been treated by countercurrent extraction with a stream comprising isobutane, said treated hydrogen fluoride is used to extract the alkyl fluoride from the alkylation reaction eflluent stream and both the alkyl fluoride enriched butane stream and the alkyl fluoride enriched hydrogen fluoride stream are recycled to the alkylation reaction zone. BACKGROUND OF THE INVENTION This invention relates to alkylation. In one of its aspects, it relates to the production of an alkylate by alkylation of an isoparaflin with an olefin employing hydrogen fluoride 'as the catalyst. In another of its aspects, the invention relates to an alkylation operation in which the total alkylation feed stream contains alkyl fluoride, e.g., ethyl fluoride, or in which operation alkyl fluoride is produced. According to a concept of this invention, hydrofluoric acid supplied as the extraction medium for removal of alkyl fluoride, for example, ethyl fluoride or alkylate range fluorides, from an alkylation reactor eflluent is subjected to a prior countercurrent extraction with a predominantly isobutane stream to increase the efficiency of the hydrofluoric acid as extracting agent for the alkyl fluoride. In another of its concepts, the invention provides alkyl fluoride free feedstock to the main fractionator of an alkylation reaction-recovery system by extracting alkylation reaction eluent with an extracting agent, eg., stripped hydrofluoric acid, of improved efhciency for removing alkyl fluoride. The invention will be described in connection with an operation in which isobutane is alkylated with ethylene in which there may or may not be present an alkylation promoter such as BF3 or higher olefins such as propylene, isobutylene, or mixtures thereof. In such an alkylation it is possible that from about to about 2O weight percent or more of the ethylene will react to form ethyl fluoride. It is known that higher concentrations of ethyl fluoride in the reaction mixture decrease the selectivity in the reaction for producing ethyl fluoride. The amount of ethyl fluoride produced is, however, sufficient to cause a substantial loss of feed and catalyst if the ethyl fluoride is not recovered. We have now conceived that the ethyl fluoride can be recovered more efliciently by extraction of the alkylation reaction eflluent with hydrofluoric acid which has been treated by countercurrent contact with a predominantly isobutane stream which produces a hydrofluoric acid which can efliciently remove all of the ethyl fluoride from the reaction eflluent before the reaction effluent is subjected to fractionation for recovery of isobutanes, n-butane, alkylate product, propane, ethane, and residual hydrofluoric acid. We have further conceived that recycle of both the ethyl fluoride enriched hydrofluoric acid from the extraction of the alkylation reactor eflluent and recycle of the ethyl fluorideenriched isobutane contact stream for reuse as 3,767,726 Patented Oct. 23, 1973 ICC reaction system feedstock results in elimination of ethyl fluoride from the product stream, thus increasing the overall efliciency of the reaction system for desired alkylate product. It is an object of this invention to provide a process for the alkylation of isoparaffin with an olefin. Further, it is an object of this invention to provide an economical alkylation of an isoparaffln with ethylene in the presence of an alkylation promoter such as a higher olefin in a process in which there is formed unavoidably an alkyl fluoride. It is a still further object of this invention to provide an alkylation process in which the alkyl fluoride is removed from the product stream with facility and returned to the reactor feed streams. Another object of the invention is to provide a process as described wherein internal recycle streams are used to increase the efficiency of the process in producing the desired alkylate product. It is a still further object of the invention to provide a process as described wherein internal recycle streams are used to increase the efficiency of removal of alkyl fluoride from the alkylation reaction eflluent prior to fractionation of the reactor effluent. Other aspects, concepts, objects, and the several advantages of this invention are apparent from this disclosure, the drawing, and the appended claims. SUMMARY OF THE INVENTION According to the present invention, in the alkylation of an isoparaflin with an olefin, eg., isobutane with ethylene, a higher olefin, eg., propylene, isobutylene, and mixtures thereof, wherein there is formed unavoidably an alkyl uoride, eg., ethyl fluoride, there is provided a process which comprises treating the effluent from the alkylation reaction to separate the eflluent into an alkylate containing hydrocarbon phase and a hydrogen fluoride phase, recovering a stream free of alkyl fluoride from the alkylate containing hydrocarbon phase by countercurrent extraction with a hydrofluoric acid stream, producing a recycle isobutane stream by fractionation of the alkyl fluoride free hydrocarbon stream, extracting at least part of the hydrofluoric acid phase separated from the reactor eflluent usingat least a portion of the recycle isobutane stream as extracting agent to produce the hydrofluoric acid stream used for extraction of th'e hydrocarbon phase, and recycling the alkyl fluoride containing extractants to the reaction zone. The drawing is a diagrammatic representation of an alkylation operation according to this invention. Referring now to the drawing, there are fed to the reaction zone, respectively, by 1, 2, and 3, ethylene, a heavier olefin used as an alkylation promoter, and make-up isobutane. As later described, these feeds, together with recycle butane, are fed by line 4 to alkylation riser reactor 5. The reaction mass is passed to settler 16. A hydrofluoric acid phase is removed from settler 6 by 7. The stream is split with a portion returning through 8 and cooler 9 to the riser reactor 5. The remaining portion 10 is fed into alkyl fluoride removal tower 11 where it is brought into countercurrent contact with a predominantly preferably liquid isobutane recycle stream which removes reaction products, particularly ethyl fluoride and alkylate range iluorides, from the hydrofluoric acid. Hydrofluoric acid of high purity is removed through 12, cooler 13, and line 14 to be mixed up with make-up hydrofluoric acid of high purity and fed as extraction agent to extractor 1S. Here the hydrofluoric acid is brought into liquid-liquid countercurrent contact with the hydrocarbon phase containing alkylate which has been removed from settler 6 by 16 and passed to the extractor 15. Hydrofluoric acid now rich with ethyl fluoride and any alkylate range fluorides is removed through 17 and returned to the riser reactor 5. The hydrocarbon phase containing alkylate from which ethyl fluoride has been removed exits extractor 15 through 18 and is fed to the main fractionation column 19. From the fractionator 19 are removed an alkylate kettle product stream 20, a normal butane vapor side product stream 5 from below the feed point 21, a recycle liquid lsobutane side product stream from above the feed point via 22, and an Overhead stream 23 containing propane, ethane and hydroluoric acid. The overhead product stream 23 is further processed to remove hydroduoric acid for return to 10 the reactor via line 29 and to produce ethane 30 and propane 31 product streams, using HF stripper 35 as shown. The liquid recycle isobutane stream 22 is split -With a portion returning through 24 to conduit 4 and to the riser reactor 5. Another portion is returned through 24 and 15 exchange 25 (optional in some operations) as extracting agent for alkyl fluoride removal tower 11. After countercurrent contact with the hydrouoric acid stream in tower 11, the extract rich isohutane 1s returned through 26, cooler 27, and 28 to riser reactor 5. ln some operations of 20 tower 11, the isobutane 24 can be at least partly vaporized. EXAMPLE Tons] Wt. Bbls./ day percent day 23 Fresh feed (4): as 0. 30 59 0 0 5.7 0.45 64 77s. 2 01. 15 7, 90s 30 n-Butane 32. 7 2. 57 320 Butenes. 76. 7 6. 02 731 Total 1,272.7 100.00 9,082 Hydrogen tuoride. 59. 11 192, 164 Water 140.1 0. 2 800 40 Acid soluble oils 23. 4 0. 04 139 Total 56,330.0 100.00 .526,228 Settler (6) bottoms (7): Hydrogen uoride 33, 294. 2 71. 28 192, 164 Ethyl fluoride 10,570.3 22.63 201,333 4. rsobutane 2,681.1 5. 74 27,245 i Water 140.1 0. 30 800 Acid soluble oils 23. 4 0.05 139 Total 46, 709.1 100.00 421,686 Settler bottoms (8) to reactor (5): Hydrogen nuonde 31,656.7 71.28 182, 715 o Ethy1 fluoride 10,050.4 22. 63 191,429 sobutane 2, 549. 2 5.74 25, 827 Water 133.2 0.30 761 Acid soluble oils 22. 2 0. 05 132 Total 44, 411.7 100.00 400,864 HF (10) to tower (11): 55 Hydrogen fluoride 1, 637. 6 7l. 28 9, 452 Ethylnuoride 519.9 22. 63 9, 903 Isobutane 131.9 5.74 1,340 Acid soluble oils 1. 1 0. O5 Total 2,297. 4 100.00 20,740 60 Tower (11) bottoms (12): Hydrogen tiuoride 1, 636 94. 2 9, 442 Ethyl uorde 40 2. 3 762 Isobutane 54 3. 1 549 Water 7 0.1 40 Acid soluble oils 0 0. 1 0 65 Total 1,737 100.0 10,793 HF acid (14) to extractor (l5) 1,737 10, 793 Reactor eiduent (16): Ethylene 7. 7 0. 08 Ethane. 7. 7 O. 08 117 70 Ethyl duende-- 4. 85 8, 889 Propane 1. 14 1, 236 Isobutane. 74. 53 72, 868 n-Butane- 6. 53 6, 148 Alkyiate- 1, 230.4 12.79 10,322 T0tal- 9, 620. 9 Main fractionator (19) charge (18): Ethyle 0 0 Ethane... 0. 08 115 0 0 1. l() I, 203 79. 84 78, 678 6. 30 5. 982 12. 68 10, 320 Total 9, 598. 1 100. 00 96, 298 Product alkylate (20) lsopentane 10. 70 0. 87 98. 1 n-Pentane (l. 62 0. 05 5. 6 2,2-dimethylbutane 4. 43 0. 36 38. 8 2,3-d1methylbutane 597. 88 48. 61 5, 136. 4 16. 61 l. 35 143.9 8. 24 0. 67 70. 5 0. 0 0. O0 0 0. 0 0. 00 0 2,4-dirnethylpentane..- 1. 35 0. 11 11. 4 Triptane 0. 0 0. 00 0 3,3-dimethylpentane 0. 0 U. O0 0 2-methylhexane 0. 25 0. 02 2. 1 2,3-dimethylpentane 0. 74 0. 06 6. 1 -rnethyihexane 0. 37 G. 03 3. 1 2,2,4-trimethy1pentane 396. 77 32. 26 3, 262. 9 2,5-dimethylhexa.ne 8. 36 0. 68 68. 5 2,4-din1ethylhexane 13. 28 1. O8 107. 9 2,2,3-trimethylpentane... 6. 52 0. 53 51. 8 2,3,4-trirnethylpentane... 77. 99 34 617. 0 2,3,3-trirnethylpentane... 52. 16 4. 24 408. 8 2,3-dimethylhexane 15. 01 l. 22 119. 9 2-methylheptene 0. 0 0. 00 0 3,4-dirnethylhexane 2. 09 0. 17 16. 5 3rnethylheptane 0. 0 0. 00 0 2,2,rtrirnethylhexane 0. 0. 02 2. 0 Residue 16. 48 1. 34 148. 7 Total 1,230.10 100. U0 10, 320. 9 dBm-ane side draw (21).' Isobutane 4. 9 13. 00 50 n-Butane. 32. 7 86. 7 4 320 Alkylate 0. 1 0. 26 1 Total 37. 7 100. 00 371 Recycle isobutane (22): thylene. 0. 0 0 0 Ethane.. 3. 8 O. 04 58 Ethyl iiluorr e- O. 0 0 0 Propane 10 9 1. 20 1,139 Isobutane- 7, 737. 7 91. 70 78, 630 :u-Butane 595. 4 7. 0G 5, 828 T0tal 8, 437. 8 100. 00 85. 655 Contact isobutane (24): Eth l 0 G 0 Ethane. 1. 6 0. 04 24 Ethyl uori e. 0 U 0 Propane 47. 1 1. 20 532 Isobutane 3, 596 91. 70 36, 542 n-Butane 276 9 7. 06 2, 710 Total 3, 921. 6 100.00 39, 80S Overhead (26) of tower (11): Ethylene. f e 0 0 o Ethane 1. 3 D. 03 2() Ethyl uorlde- 479. 9 10. 73 9, 141 Propane. 39. 4 0. 88 445 Isobutane 3, 673 9 82. 14 37, 333 n-Butane 276. 9 6. 19 2, 710 Hydrogen fluoride 1. 6 0. 03 9 Total 4,473.0 100. 00 49, 658 Ethane product (30) 3.8 59 HF stripper bottoms (31); Propane 5. 7 64 Alkylate propert1es: API gravity 76 Liquid density, lbs. bbl. 238.4 ASTM dist. end point, lF. 317 RON +0 100.9 MON +0 94.8 Reactor conditions: Catalyst/hydrocarbon vol. ratio 4:1 Isobutane to olefin mole ratio :1 Temperature, F 90 Pressure, p.s.i.g 190 Residence time, sec. 60 Ethylene conversion (single pass), percent 98 Alkylate yield: Lbs/lb. olefin 2.72 Bb1./100 lbs. olefin 1.141 It has been observed, as stated before, that an increased amount of ethyl fluoride in the reactor retards the formation of more ethyl fluoride and that recycle of the ethyl iluoride to the reactor also increases the conversion of ethyl iluoride to alkylate so that an additional amount of high quality alkylate is formed. The isoparains which can be used in our process include isobutane and/or isopentane. The oleiins, in addition to the required ethylene, can include propylene, butylenes, amylenes, and hexenes, either alone or in combination. The ranges of isoparaflins to olens in mole ratios can be about 1.5:1 up to about 20:1 or higher. The catalyst to hydrocarbon volume ratios can be about 1:1 to about 10:1. The hydrofluoric acid catalyst used can be about 80 percent by weight up to about 100 percent by weight hydrogen uoride, other components being water, usually less than about 5 percent, and acid soluble oils. Reactor temperatures can be about 40 F. to about 175 F. with pressures being suicient to maintain the now preferred liquid phase system. The weight ratio of liquid hydrofluoric acid solvent to ethyl fluoride to be absorbed can range from about 1:1 up to about 5: 1. Fractionation conditions are well known in the prior art. Although the invention has been described as being primarily applicable and the now contemplated best mode is as production of diisopropyl from isobutane and ethylene reacted in the presence of a hydrouoric acid catalyst, it is known that an amount of a heavier oleiin will promote an increased conversion of ethylene to alkylate. It will be obvious to one skilled in the art in possession of this disclosure having studied the same that the invention and its concepts can have other applications. Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawing and the appended claims to the invention the essence of which is that alkyl fluoride can be effectively removed from an alkylation reactor euent stream before fractionation of the alkylate containing hydrocarbon portion of the reactor euent by the extraction of the hydrocarbon stream using a high purity hydrouoric acid produced by stripping reaction product from the hydrouoric acid phase of the reactor product euent. We claim: 1. A process for the alkylation of an isoparafn with olen in the presence of a hydrouoric acid catalyst which comprises: (l) conducting said alkylation in an alkylation zone to produce an alkylate reaction mixture which contains alkyl uoride, (2) separating said mixture into an alkylate-containing hydrocarbon phase and a hydrofluoric acid phase, (3) extracting said alkylate-containing hydrocarbon phase with a treated hydrofluoric acid stream, said treated hydrofluoric acid stream having been substantially reduced in alkyl fluoride content as hereinafter delineated, thereby transferring alkyl fluoride from said alkylate-containing hydrocarbon phase to form a hydroiluoric acid stream `containing alkyl uoride, (4) fractionating said alkylate-containing hydrocarbon stream from which alkyl fluoride has been transferred to separate a recycle isoparain stream, (5) contacting at least a portion of said recycle isoparain stream with at least part of the hydrouoric acid phase separated from the reaction mixture thereby transferring alkyl fluoride from said hydrofluoric acid phase to said isoparain stream to obtain the treated hydrolluoric acid stream used in step (3), and (6) recycling said hydrouoric acid stream containing alkyl fluoride and the isoparain stream containing alkyl fluoride to the reaction zone. 2. A process according to claim 1 wherein olefin is ethylene. 3. A process according to claim 2 wherein the isoparain is isobutane which is passed as extraction agent in contact with at least part of the hydrouoric acid phase separated from the reactor effluent thereby transferring alkyl uoride from the hydrouoric acid phase to the isobutane to obtain the trted hydrouoric acid stream used for extraction of the hydrocarbon phase and the isobutane containing extracted alkyl uoride is recycled to the reaction zone. 4. The process according to claim 1 wherein the fractionation producing said recycle isoparaftin stream also produces a normal butane stream, an alkylate product stream, and a stream containing ethane and propane. 5. The process according to claim 4 wherein the stream containing ethane and propane is further treated to remove residual hydrofluoric acid, said hydrofluoric acid being recycled to the reaction zone. 6. The process according to claim 1 wherein at least one higher olefin is present in the alkylation feed mixture as an alkylation promoter. 7. A process according to claim 7 wherein the isoparain is isobutane. 8. The process according to claim 6 wherein the higher oleins are chosen from the group consisting of propylene and isobutylene. References Cited UNITED STATES PATENTS 3,073,878 1/1963 Johnson 260-683.48 3,204,010 8/1965 Van P001 260-683.42 3,410,759 11/1968 Fontenot et al. 260-683.48 DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner U.S. Cl. X.R. 260-683.48

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Cited By (11)

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    US-3864423-AFebruary 04, 1975Phillips Petroleum CoAlkylation of hydrocarbons
    US-3879488-AApril 22, 1975Universal Oil Prod CoSeparate recycle of regenerated acid and of isoparaffin from HF catalyst regeneration zone
    US-3894111-AJuly 08, 1975Universal Oil Prod CoHydrogen fluoride alkylation utilizing a rectification zone
    US-3903194-ASeptember 02, 1975Phillips Petroleum CoHF Alkylation of isoparaffin with olefin heavier than ethylene with ethyl fluoride as reaction improver
    US-3911044-AOctober 07, 1975Phillips Petroleum CoRemoval of propane from alkylation effluent without loss of ethyl fluoride
    US-3929924-ADecember 30, 1975Phillips Petroleum CoFractionation of effluent from HF catalyzed alkylation
    US-3929925-ADecember 30, 1975Phillips Petroleum CoRecovery of a propane-ethane product and recycle of propane in HF alkylation
    US-3972956-AAugust 03, 1976Phillips Petroleum CompanyAvoiding pollution by HF catalyst residues in alkylation
    US-4038332-AJuly 26, 1977Phillips Petroleum CompanySeparation of ethyl fluoride
    US-4373110-AFebruary 08, 1983Phillips Petroleum CompanyHF Alkylation process and apparatus
    US-RE29084-EDecember 21, 1976Universal Oil Products CompanySeparate recycle of regenerated acid and of isoparaffin from HF catalyst regeneration zone