US3846505A

US3846505A - Hf alkylation including recycle and further alkylation of the alkylate-containing hydrocarbon

Info

Publication number: US3846505A
Application number: US00298708A
Authority: US
Inventors: R Anderson
Original assignee: Universal Oil Products Co
Current assignee: Honeywell UOP LLC; Universal Oil Products Co
Priority date: 1972-03-20
Filing date: 1972-10-18
Publication date: 1974-11-05
Anticipated expiration: 1991-11-05

Abstract

A process for alkylating an isoparaffin with an olefin-acting reactant by contacting the isoparaffin with a first portion of the olefin-acting reactant and with a first alkylation catalyst in a first HF alkylation zone; contacting the hydrocarbons recovered from the first alkylation zone with a second portion of the olefin-acting reactant and with a second HF alkylation catalyst in a second alkylation zone; recovering the product of the process from the second alkylation zone; and recycling a portion of the hydrocarbon effluent from the first alkylation zone back into the first alkylation zone to provide optimum alkylation conditions.

Description

United States Patent 11 1 1 1 ,846,505 Anderson Nov. 5, 1974 [54] HF ALKYLATION INCLUDING RECYCLE 2,427,293 9/1947 Matuszak 260/68345 AND FURTHER ALKYLATION OF THE 3,204,011 8/1965 Hettick et a1. 260/683.48 3,236,912 2/1966 Phillips 260/683.49 ALKYLATE'CONTAINING HYDROCARBON R22,l46 7/1942 Goldsby et a1... 260/683.46 [75] Inventor: Robert F. Anderson, La Grange R22,51O 7/1944 Goldsby et a1... 260/683.46

Park, 111. g [73] Assignee: Universal Oil Products Company, Primary Examiner Delben Assistant Examiner-G. J. Crasanakis Des Plaines, 111. A A F J R H J ttomey, gent, 0r zrmames oatson, r.; [22] Wed: 1972 Robert W. Erickson; William 1-1. Page, 11 [21] Appl. No.: 298,708

, Related US. Application Data [57] ABSTRACT [63] Continuation-impart of Ser. No. 236,049, March 20, A process f alkylating an isoparaffin with an 0]efin 1972 acting reactant by contacting the isoparaffin with a first portion of the olefin-acting reactant and with'a t t u a l] Fllt. contacting the hydrocarbons recovered from the first [58] 0 260/ 68348 alkylation zone with a second portion of the olefin- 260/683'58 68.349 acting reactant and with a second HF alkylation cata-f lyst in a second alkylation zone; recovering the prod- [56] References and uct of the process from the second alkylation zone; UN E STATES PATENTS and recycling a portion of the hydrocarbon effluent 2,256,615 9/1941 Hederhorst 2 60/683.46 from the first alkylation zone back into the first alkyla- 2,305,026 12/1942 Munday 260/683.46 tion zone to provide optimum alkylation conditions. 2,312,539 3/1943 Frey 260/683.45 2,417,251 3/1947 Hemminger 260/683.46 7 Claims, 1 Drawing Figure HF ALKYLATION INCLUDING RECYCLE AND FURTHER ALKYLATION OF THE ALKYLATE-CONTAINING HYDROCARBON CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my copending application Ser. No. 236,049, filed on Mar. 20, 1972 now US. Pat. No. 3,787,518.

BACKGROUND OF INVENTION This invention relates to a process for producing an alkylation reaction product from an isoparaffin and an olefin-acting compound. More specifically, this invention relates to a process for alkylating an isoparaffinic reactant with an olefin-acting reactant, utilizing hydrogen fluoride catalyst, to provide valuable motor fuel components. In one aspect, the present invention relates to a hydrogen fluoride catalyzed isoparaffin-olefin alkylation process in which a particular method for utilization of reactants and reaction products is employed to provide optimum alkylation conditions and a high quality product, while the size of isoparaffin recycle and the associated utilities and equipment utilized are substantially reduced.

Alkylation of isoparaffinic hydrocarbons, such as isobutane, isopentane and the like,'with olefinic hydrocarbons such as propylene, butylene, and amylenes, and olefin-acting compounds such as C -C alkyl halides, sulfates, etc., is well known as a commercially important method for producing gasoline boiling range hydrocarbons. The-C -C hydrocarbons generally produced by the isoparaffin-olefin alkylation reaction are termed alkylate? Alkylate is particularly valuable as a motor fuel blending stock because of its high motor and research octane ratings. Alkylate is generally used to improve the overall octane ratings of available gasoline pools to comply with the requirements of modern automobile motors. High octane alkylate fuel components are particularly important in providing motor fuels of sufficiently high quality when it is desired not to employ alkyl lead compounds in the fuel to meet octane requirements. A continuing goal of the art is to provide an alkylation process which produces an alkylate product having higher motor and research octane ratings than is possible using conventional processes and to reduce the cost and difficulty of producing the alkylate.

In general, commercial isoparaffin-olefin alkylation processes employ isobutane and sometimes isopentane as the isoparaffinic reactant and propylene, butylenes and amylenes, or a mixture thereof, as the olefin-acting reactant. Catalysts utilized include hydrogen fluoride, sulfuric acid, zeolites, and other like acidic or acidacting materials. In alkylation operations using hydrogen fluoride catalyst, the isoparaffin, olefin-acting agent and hydrogen fluoride are typically contacted in an alkylation reactor, forming a reaction mixture. After the alkylation reaction is substantially complete, the reaction mixture is'withdrawn from the reactor and is settled into hydrocarbon and catalyst phases in a separation zone such as a settling vessel, and the catalyst thus separated is recycled to the reactor for further use. The hydrocarbon phase produced by settling operation is further processed, typically by fractionation, to recover the alkylate product and to separate unconsumed LII 2 isoparaffin for further use by recycle to the alkylation reactor.

It has been found necessary to perform commercial isoparaffin-olefin alkylation operations at fairly specific reaction conditions, such as temperature, pressure, and concentrations of catalyst and reactants in the alkylation reactor, in order to produce an acceptable yield of the desired high quality alkylate product. One of the conditions required to provide a product having the desired utility as a high octane blending stock has been a large excess of isoparaffin relative to the amount of olefin employed, e.g., an isoparaffin/olefin mole ratio of about 8:1 to about 30:1. The primary limitations on the amount of excess isoparaffin utilized are the capital and utilities costs of the equipment needed to separate the excess isoparaffin from the product subsequent to the alkylation step. The quality of the alkylate isfound to improve when the isoparaffin/olefin mole ratio in the alkylation reactor is raised, even when it is raised to levels found uneconomical in the prior art. Commercial alkylation operations are thus limited in producing high quality alkylate by the amount of excess isoparaffin which must be recovered and recycled to the alkylation reactor after fractionation of the hydrocarbon phase of the reactor effluent. The large amount of isoparaffin which must be passed, unreacted, through the alkylation reactor and settler, and subsequently separated from the alkylate product by fractionation, necessitates the use of fractionation equipment of large capacity in order to provide an adequate separation of, for example, C alkylate from isobutane reactant which is to be recycled to the reactor. The expense and difficulty of providing a large isoparaffin throughput, fractionation and recycle in order to produce alkylate of adequate quality may be obviated, in part, through the use of the process of this invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a process for alkylating an isoparaffin with an olefin-acting compound to produce an alkylation reaction product possessing superior qualities as a motor fuel component.

A further object of the present invention is to provide a process for alkylating an isoparaffinic reactant with an olefin-acting reactant wherein a smaller scale of isoparaffin fractionation and recycle is required in order to obtain a high quality motor fuel alkylate product.

In a broad embodiment, the present invention relates to a process for producing an alkylation reaction product from an isoparaffinic reactant and an olefin-acting reactant which comprises the steps of: (a) contacting the isoparaffinic reactant with a first portion ofthe olefin-acting reactant and with a first alkylation catalyst in a first alkylation zone at alkylation conditions; (b) removing the resultant hydrocarbons from contact with the first alkylation zone and the first alkylation catalyst to form a first hydrocarbon effluent stream; (c) dividing the first hydrocarbon effluent stream into at least two portions and forming an effluent recycle stream from a first portion; (d) introducing at least a portion of the effluent recycle stream into the first alkylation zone; (e) contacting a second portion of the olefinacting reactant with a second portion of the first hydrocarbon effluent stream formed in step (c) and with a second alkylation catalyst in a second alkylation zone at alkylation conditions; (f) removing the resultant hyv zone and the second alkylation catalyst to form a second hydrocarbon effluent stream; and, (g) forming a reaction product stream from at least a portion of the second hydrocarbon effluent stream and recovering the alkylation reaction product from the reaction product stream.

Among the important advantages included in the process of this invention, relative to prior art processes, are those which derive from a substantial decrease in the overall molar excess amount of isoparaffin required per mole of olefin utilized. By passing only a portion of the olefin reactant to the first alkylation reactor, a significantly smaller amount of the isoparaffin is required in the first reactor to provide the required molar excess of isoparaffin in relation to the moles of olefin reactant utilized in the first reactor. The hydrocarbon effluent from the first reactor is then contacted with a second portion of the olefin reactant in a second reactor, whereby the same relatively small molar amount of isoparaffin is utilized to provide the required molar excess of isoparaffin in both the first and the second reaction systems.

The overall isoparaffin fractionation requirement in the process of the present invention is further substantially reduced by recycling a portion of the hydrocarbon effluent from thefirst alkylation zone back into the first alkylation reactor. Thus, the hydrocarbon effluent from the first alkylation zone, in one embodiment, is divided into two portions. One portion of the hydrocarbon effluent from the first alkylation zone is passed directly to the second alkylation zone. The remainder of the hydrocarbon effluent from the first alkylation zone is passed, as an effluent recycle stream, back into the first alkylation reactor, in order to provide a part of the molar excess of isoparaffinrequired in the first reactor. By employing the foregoing, a very high mole ratio .of isoparaffin to olefin-acting reactant can be obtained in both the first alkylation zone and the second alkylation zone. The alkylate-product of the process will thereby be produced witha substantially superior octane rating and generally superior quality compared to alkylate produced by a conventional commercial operation. At the same time, the amount of isoparaffin which must be separated from the alkylate product, e.g.,'by fractionation in an isobutane stripper, is maintained at a very low level.

Further objects, embodiments and advantages of the present process will be apparent to those skilled in the art from the following description of the drawing and detailed description of the invention.

DESCRIPTION OF THE DRAWING The attached'drawing is a schematic illustration of one embodiment of the process of the present invention. In the particular embodiment set forth, the isopar-' affin is isobutane'and the olefin-acting reactant comprises propylene and butylenes. The scope of the present invention is not intended to be limited to the embodiment shown, and various other suitable reactants and embodiments will be obvious to those skilled in the art from the description hereinafter provided.

Referring to the drawing, a conventional olefin feed to an isobutane-olefin alkylation process is charged continuously through conduit 1. The olefins are charged at a rate of about 300 moles/hour propylene and 300 moles per hour butylenes. In addition, smaller amounts of other hydrocarbons which are conventionally present in a commercial olefin feedstock, including 120 moles/hour isobutane, 35 moles/hour n-butane and moles/hour propane, are charged through conduit 1 in admixture with the olefins. The continuously charged hydrocarbons in conduit 1 are divided into two streams of equal volume and passed into conduits 2 and 3. The olefinic feedstocks passed into conduits 2 and 3 thus both comprise 150 moles/hour propylene, 150 moles/hour butylenes, 60 moles/hour isobutane, 17.5 moles/hour n-butane and 35 moles/hour propane. Make-up isobutane is charged via conduit 4 into conduit 2 and admixed in conduit 2 with the portion of the olefin feedstock therein. The make-up isobutane stream is passed through conduit 4 at a rate of 500 moles/hour of isobutane, with conventional amounts of non-reactive contaminants including about 15 moles/- hour n-butane and about 10 moles/hour propane. The admixed make-up isobutane and olefin feed continues through conduit 2, and recycled isobutane from conduit 28 is passed into conduit 2 and admixed with the contents thereof. The recycle isobutane is passed into conduit 2 at the rate of 2,400 moles/hour isobutane, with some other non-reactive hydrocarbon recycle resulting from imprecise fractionation, including 240 moles/hour n-butane and 140 moles/hour propane. Hydrocarbon effluent recycle from reactor 5 and settler 11,

hereinafter more fully described, is passed through conduit 13 into conduit 2 and admixed with the abovedescribed fresh and recycle hydrocarbons therein. The effluent recycle stream in conduit 13 is charged into conduit 2 at the rate of 2,660 moles/hour isobutane, 272.5 moles/hour n-butane, 185 moles/hour propane and 300 moles/hour C hydrocarbons. The total hydrocarbons charge to reactor 5 thus comprise 150 moles/hour propylene, 150 moles/hour butylenes, 5,620 moles/hour isobutane, with non-reactive hydrocarbons including 3' Q moles/hour propane, 545 moles/hour nbutane and 300 moles/hour C 4 hydrocarbons. The isobutane/olefin mole ratio of the feed to reactor 5 is thus about 18:1, substantially higher than is economically available in prior art commercial operations. The combined feed is passed through conduit 2 into reactor 5 and admixed with hydrogen fluoride alkylation catalyst to form a reaction mixture. The hydrogen fluoride alkylation catalyst is charged to reactor 5 through conduit 15. The catalyst contains about wt. percent acid and less than about 1 wt. percent water, with the remainder being conventional organic diluent. Alkylation conditions maintained in reactor 5 include a temperature of about l00F. and a pressure sufficient to maintain the reactants and catalyst in the liquid phase. An acid/hydrocarbon volume ratio of about 1 to about 2 is also maintained. Heat generated in the alkylation reaction is withdrawn using indirect heat-exchange. Cooling water is charged through conduit 6 into reactor 5, and passed in indirect heat-exchange with the reaction mixture. Used cooling water is withdrawn via conduit 7. After a contact time of about 0.1 minute to about 5 minutes, the reaction mixture in reactor 5 is withdrawn and passed through conduit 8 into reaction soaker 9. The reaction mixture of catalyst, reactants and reaction products is maintained in reaction soaker 9 for about 1 minute to about 10 minutes at a temperature and pressure about the same as employed in reactor 5. The reaction mixture is then withdrawn and passed through conduit 10 into settler 11. The reaction mixture is allowed to stand without agitation in settler 11, whereby the hydrogen fluoride catalyst forms a heavier phase and the hydrocarbon components of the reaction mixture form a lighter phase. The lower, catalyst phase is withdrawn from the bottom of settler 11 through conduit l5 and passed back to reactor 5 for further catalytic use. It may be necessary to treat a portion of the recycle catalyst to maintain the desired acid strength, etc. This can be done by passing a slip stream of catalyst from conduit 15 to conventional regeneration means. Such a regeneration operation being conventional and not essential to an understanding of the present invention, the mode of performance thereof will be obvious to those skilled in the art, and this operation is not included in the drawing and description thereof. Referring again to settler 11, the hydrocarbon phase formed therein, which includes the total hydrocarbon effluent from reactor 5 and reaction soaker 9, is withdrawn from the top of settler 1 1 via conduit 12. The hydrocarbon effluent from settler 11 is charged into conduit 12 at the rate of 5,320 moles/hour isobutane, 370 moles/hour propane, 545 moles/hour n-butane, and 600 moles/hour C hydrocarbons. The hydrocarbon effluent from settler 11 passed into conduit 12 is divided into two portions. One portion is passed as an effluent recycle stream through conduit 13 and conduit 2 back into reactor 5 as described above. A second portion of the hydrocarbon effluent is passed from conduit 12 into conduit 14 at the rate of 2,660 moles/hour isobutane, 185 moles/hour propane, 272.5 moles/hour nbutane, and 300 moles/hour C hydrocarbons. The hydrocarbons in conduit 14 are passed into conduit 3 and commingled with the fresh olefine feed therein. The total combined hydrocarbon feed to reactor 16 through conduit 3 is thus charged at the rate of 2,720

moles/hour isobutane, 150'moles/hour butylenes, 150 moles/hour propylene, 290 moles/hour n-butane, 220 moles/hour propane and 300 moles/hour C hydrocarbons. The isobutane/olefin mole ratio of the hydrocarbon charge to reactor 16 is thus about 9:1, within the adequate range of operation. The other alkylation conditions in reactor 16 are similar to those employed in reactor 5, i.e., a temperature of about 90-100F., acid/hydrocarbon volume ratio of about 1 to about 2 and a pressure sufficient to maintain the reaction mixture components in the liquid phase. Hydrogen fluoride catalyst containing about 80 wt. percent acid, less than about 1 wt. percent water, with the remainder made up of organic diluent, is charged to reactor 16 through conduit 23 and intimately admixed with the hydrocarbon feed from conduit 3 to form the reaction mixture. Cooling water is charged through conduit 17 and passed in indirect heat-exchange with the reaction mixture in reactor 16. Used cooling water is withdrawn through conduit 18. After a contact time of about 0.1 minute to about 5 minutes, the reaction mixture is withdrawn from reactor 16 and passed through conduit 19 into reaction soaker 20. The reaction mixture of catalyst, reactants and reaction products is maintained in reaction soaker 20 for a contact time of about 1 minute to about minutes at a temperature and pressure substantially the same as employedin reactor 16. The reaction mixture is then withdrawn and passed through conduit 21 into settler 22. The reaction mixture is allowed to stand without agitation in settler 22, in order to facilitate separation of the catalyst and hydrocarbons into separate phases. The heavier, catalyst phase is withdrawn from the bottom of settler 22 through conduit 23 and recycled to reactor 16 for furthercatalytic use as described. A portion of the catalyst in conduit 23 may be passed to a conventional regenerationoperation if desired. The upper, hydrocarbon phase in settler 22 is withdrawn through conduit 24. The hydrocarbon effluent from settler 22 is passed into conduit 24 at the rate of about 220 moles/hour propane, 2,420 moles/hour isobutane, 290 moles/hour n-butane and 600 moles/hour C hydrocarbons. The hydrocarbon effluent stream in conduit 24 is charged into isobutane stripper 25. In isobutane stripper 25, the hydrocarbon effluent from settler 22 passed through conduit 24 is fractionated to separate a recycle isobutane stream and a product alkylate stream. The vessel employed contains conventional trays, reboiling means, refluxing means, etc. Alkylate product (C hydrocarbons) is removed as a bottoms product from isobutane stripper 25 through conduit 26, passed out of the operation, and recovered for motor fuel or other desired uses at the rate of 600 moles/hour. Normal butane, a by-product of the process in the embodiment described, is withdrawn as a side cut through conduit 27 at the rate of 50 moles/hour plus 10 moles/hour isobutane impurity; Recycle isobutane is withdrawn as a side cut on a higher tray in isobutane stripper 25 through conduit 28. The recycle isobutane stream is passed out of isobutane stripper 25 through conduit 28 at the rate of 2160 moles/hour isobutane, 215 moles/hour n-butane and 140 moles/hour propane. The recycle isobutane stream in conduit 28 is passed into conduit 2 as described above. An overhead stream is withdrawn from isobutane stripper 25 and passed through conduit 29 into depropan izer 30. The overhead stream is passed from the isostripper at the rate of moles/hour propane, 250 moles/hour isobutane and 25 moles/hour n-butane. In depropanizer 30 the feed from conduit 29 is fractionated to separate propane from isobutane and n-butane. The isobutane and n-butane are withdrawn, at the rate of 240 moles/hour isobutane and 25 moles/hour n-butane, as a bottoms product and passed through conduit ,31 into conduit 28 for use in the recycle isobutane stream. Propane, admixed with some hydrogen fluoride and isobutane, is withdrawn overhead through conduit 32 r at the rate of 80 moles/hour propane and 10 moles/- hour isobutane, and passed through conduit 32 into conduit 33 in admixture with hydrogen fluoride from conduit 41. The mixture of propane, isobutane and hydrogen fluoride in conduit 33 is passed into condenser 34 and condensed to liquefy the propane, isobutane and acid. The liquefied propane, isobutane and hydrogen fluoride are then passed through conduit 35 into settler 36. Most of the hydrogen fluoride passed into settler 36 settles out as a heavy phase of relatively pure acid and is withdrawn through conduit 37. This relatively concentrated acid may, if desired, be passed back into the recycle catalyst streams in conduit 15 and conduit 23, by means not shown. The liquefied propane phase in settler 36 is withdrawn and passed through conduit 38 into hydrogen fluoride stripper 39, wherein the propane is fractionated to separate out any remaining acid. The acid is withdrawn overhead through conduit 41, passed back into conduit 33, and treated as described above. The propane is withdrawn as a byproduct from the bottom of hydrogen fluoride stripper 39 through conduit 40 at the rate of 80 moles/hour propane and 10 moles/hour isobutane. Certain conventional equipment and operations necessary for the operation of the embodiment described in the foregoing have been omitted from the drawing and description thereof, e.g., pumps, valves, reboilers, etc. The use and placement of such conventional items will be obvious to those skilled in the art.

The foregoing description illustrates some of the advantages of the present invention over prior art, when embodied in an isobutane-C Q, olefin alkylation process. For example, reaction conditions in reactor and reactor 16 include a high isobutane/olefin mole ratio of about 18:1 and 9:1 respectively, as high as can be economically employed in conventional alkylation processes. Yet fractionation requirements in isobutane stripper 29 need only be sufficient to separate isobutane equivalent to an overall isobutane-olefin mole ratio of about 4:1. The alkylate produced is of equal or superior quality-to that produced in conventional alkylation processes in which'a 13:1 isobutane/olefin mole ratio is employed, while the fractionation requirements are substantially reduced, with the attendant savings in capital and utilities costs. In one obvious modification, the amount of isobutane utilized overall can be increased, whereby the alkylation reaction conditions in the present process will include an isobutane/olefin mole ratio higher thandescribed, resulting in an even more valuable product. The amount of isobutane to be recycled in such a modification is less than or equal to that in a conventional operation, while the product is significantly improved.

DETAILED DESCRIPTION OF INVENTION The alkylation process of the present invention may be applied, in general, to the alkylation of C -C isoparaffins. The preferred isoparaffins are isobutane and isopentane, particularly isobutane. A mixture of two or more isoparaffins may also be employed, if desired. A suitable isoparaffin feedstock for use in the present process may contain some non-reactive contaminants such as normal paraffins. For example, a conventional commercial isobutane alkylation feedstock generally contains about 95 wt. percent isobutane, 4 wt. percent n-butane and 1 wt. percent propane.

Olefin-acting compounds suitable for use in the process of the present invention as an olefin-acting reactant include C C olefins, alkyl halides, alkyl sulfates,

alkyl phosphates, alcohols, etc., and mixtures thereof. C -C olefins and alkyl halides are preferred, particularly propylene, butylenes and amylenes. It is to be understood that the process of the present invention may be applied to the alkylation of mixtures of two or more olefin-acting compounds, with the same benefits and improvements resulting as would be obtained using a single olefin-acting compound. For example, many conventional olefin feedstocks in commercial isoparaffin-olefin alkylation operations contain mixtures of propylene and butylenes, butylenes and amylenes, or propylene, butylene and amylenes. Application of the present process to such mixtures results in improvements in the quality of the product equal to those obtained from a single olefin. Similarly, a mixture of C -C alkyl halides and olefins in any proportion is also suitable in many cases, e.g., when the halide is fluoride. The particularly preferred C -C olefin feedstocks are conventionally derived from petroleum refining processes such as catalytic cracking and may contain substantial amounts of saturates, lighter and heavier olefins, etc. Such conventional sources of olefin feedstocks are suitable for use to provide the olefin-acting reactant in the present process.

The alkylation catalyst employed in the present process is hydrogen fluoride. Generally, hydrogen fluoride alkylation catalyst contains about wt. percent or more of titratable acid, about 5 wt. percent or less water, with the remainder being organic diluent. Such a hydrogen fluoride alkylation catalyst is suitable for use in both the first and second alkylation reactors and zones in the present process. A particularly preferred catalyst contains about wt. percent acid, less than 1 wt. percent water, the remainder being organic diluent.

.of the present invention. The scope of the present invention is intended to include, for example, embodiments of the present process in which reactants and hydrogen fluoride catalyst are contacted in the alkylation reactors to form alkylation reaction mixtures and the hydrocarbons and catalyst are subsequently separated by settling for further processing. Particular alkylation zones and optimum alkylation conditions in specific embodiments of the present process depend upon the composition of the particular-olefin-acting reactant and the particular isoparaffin.

In general, alkylation conditions suitable for use in an embodiment of the present process in which the isoparaffin is preferably isobutane include a temperature of about 0F. to about 200F., a pressure sufficient to maintain the reactants and the hydrogen fluoride catalyst in the liquid phase, and a contact time between the hydrocarbons and catalyst of about 0.1 minute to about 30 minutes. In a preferred embodiment, a catalyst/hydrocarbon volume ratio of about 0.1 to about 10 is preferred, and a temperature of about 50F. to about F. is preferably employed.

In a particularly preferred embodiment, the reaction mixtures of catalyst, reactants and reaction products formed in the alkylation reactors are passed through reaction soakers. In the description of the preferred embodiments herein provided, it is intended that both an alkylation reactor and a reaction soaker, if one is utilized are includedwithin the scope of the term alkylation zone., Suitable reaction soakers are well known in the art. For example, the reaction soakers described in US. Pat. No. 3,560,587 and No. 3,607,970 may suitably be employed in the present process. Such reaction soakers are typically vessels equipped with perforated trays, baffle sections, or the like, to maintain the reaction mixture of catalyst and hydrocarbons charged from the alkylation reactor as a fairly homogeneous mixture, or emulsion, for a predetermined length of time. The mixture 'of catalyst and hydrocarbons is maintained in the reaction soaker for a time which depends on the composition of the reaction mixture. A reaction soaker residence time of about 1 minute to about 30 minutes is preferred. The temperature and pressure maintained in the reaction soaker are the same as the temperature and pressure maintained in the alkylation reactor.

Means for separating the reaction mixture into a hydrocarbon phase and catalyst phase, is necessary to separate the hydrogen fluoride catalyst from the hydrocarbons. The effluent from an alkylation reactor or reaction soaker is conventionally settled to provide the hydrocarbon effluent from the alkylation zone, which contains alkylation reaction products and isoparaffin. When utilizing hydrogen fluoride catalyst, the effluent from an alkylation reactor or soaker comprises a mixture of isoparaffin, reaction products, catalyst and catalyst-soluble organic materials, possibly with small amounts of olefin-acting compounds, light hydrocarbon gases, etc. When this mixture is allowed to stand unstirred, i.e., settled, the reaction products, isoparaffin and light hydrocarbon gases form a hydrocarbon phase. The hydrogen fluoride and catalyst-soluble organic materials form a separate phase. The hydrocarbon phase is then easily mechanically separated from the catalyst phase to provide the hydrocarbon effluent streams, which are, in turn employed, to provide effluent recycle and reaction product recovery streams. The temperature and pressure employed in.such a settling operation are substantially the same as those described above in connection with alkylation reaction conditions. The hydrocarbons and the catalyst are preferably maintained in the liquid phase during the separation operation.

Some means for withdrawing heat from the alkylation zones is necessary for operation of the process. A variety of means for accomplishing the heat withdrawal are, well known. For example, in a preferred embodiment the heat generated in the alkylation reaction may be withdrawn directly from the alkylation reactor by indirect heat exchange between cooling water and the reaction mixture in the reactor.

One portion of the hydrocarbon effluent stream recovered from the first alkylation zone, by settling the reaction mixture to separate the catalyst, is combined with a second portion of the olefin-acting compound and charged to the second alkylation reactor, wherein the combined olefin and hydrocarbon effluent are contacted with a second alkylation catalyst. It is contemplated that sufficient isoparaffin is charged to the first alkylation zone so that no further make-up isoparaffin, or isoparaffin recovered from fractionation, need be added to the hydrocarbons charged to the second reactor. Under some conditions, it may be advantageous to charge some further fresh isoparaffin to the second alkylation reactor, and such a modification is within the scope of the present process.

In general, the benefits andadvantages of the present process are provided when the isoparaffinic reactant is charged into a series of at least two separate alkylation zones and contacted with at'least two different portions of the olefin-acting reactant therein. One obvious modification of the present process is to divide the olefinacting reactant into a plurality of portions, e.g., three or more. The isoparaffin and a first portion of the olefin-acting reactant are contacted in a first alkylation zone and the hydrocarbons are separated from the'first catalyst to form a hydrocarbon effluent stream. The hydrocarbon effluent from the, first alkylation zone is then divided into an effluent recycle stream and a charge stream to the second reactor. The effluent recythe second alkylation zone is contacted with a third portion of the olefin-acting reactant in a third alkylation zone, etc. The hydrocarbon effluent from the last alkylation zone in the series provides a reaction product stream, which is fractionated to recover the alkylation reaction product and separate the isoparaffin con-' tained therein for recycle to the first alkylation zone.

Where it is desired to employ two alkylation zones and to divide the olefin-acting reactant into two portions, as in the preferred embodiment, it is preferred that the portions of olefin-acting reactant be such that neither portion contains less than about 10 'vol. percent of the olefin-acting reactant. For example, in a continuous operation, the first portion of olefin may be fed to the first alkylation zone at a rate of 10 moles/hour along with a suitable corresponding amount of isoparaffin sufficient to provide the desired molar excess thereof in the first reactor. The second portion of olefin is, in this case, preferably fed into the second alkylation zone at a rate of at least about 1 mole/hour and not more than about moles/hour. Preferably the two portions of olefin-acting compound do not vary in the amount 'of olefin-acting compound they contain by more than about 1:5 to about 5:1. Best results are achieved in a two-reactor system, as described in the preferred embodiment, when the two portions of olefin-acting reactant contain roughly equal molar amounts of the olefin-acting reactant. In this way, the amount of isoparaffin required in order to provide an optimum molar excess in each alkylation zone is kept to a minimum, while the highest quality product possible can thereby be obtained from both the first and second reactors.

In a preferred embodiment of the present invention, wherein two alkylation zones are employed, the hydrocarbon effluent from the first alkylation zone is dividedinto at least two portions. The term hydrocarbon effluent stream is intended to include all hydrocarbons recovered from an alkylation reactor when separated from the catalyst. For example, in an operation utilizing hydrogen fluoride in an alkylation reactor, the catalyst is separated from the resultant hydrocarbons after the reaction. The settled hydrocarbon phase removed from the settler is the hydrocarbon effluent stream in such an operation. As stated, in one preferred embodiment, the hydrocarbon effluent stream from the first alkylation zone is divided into at least two portions. The term divided is intended to mean that the volumetric concentration of each and every compound and component, in each and every portion formed when the hydrocarbon effluent stream is divided is substantially the same. Thus, the division is intended to include physical partition of the hydrocarbon effluent stream and to exclude flashing and fractionation-type separations. One portion formed bydivision of the hydrocarbon effluent stream from the first alkylation zone is recycled to the first alkylation zone. This stream is therefore termed an effluent recycle stream. The term effluent recycle stream is intended to include that portion of a hydrocarbon effluent stream from an alkylation zone which is divided from the hydrocarbon effluent stream and passed back into the reactor of the alkylation zone.

The amount of a hydrocarbon effluent stream which is separated for use as an effluent recycle stream may be from about 1 vol. percent of the hydrocarbon effluent stream to about 75 vol. percent. In an embodiment employing two alkylation zones, wherein the hydrocarbon effluent stream from the first alkylation zone is divided to form at least two portions, one of which is charged to the second alkylation reactor and the other recycled to the reactor of the first alkylation zone as an effluent recycle stream, it is preferred that the effluent recycle stream contain about 25 vol. percent to about 60 vol. percent of the hydrocarbon effluent stream from the first alkylation zone.

In any event, the hydrocarbon effluent stream from i the second alkylation zone, where two alkylation zones are employed, or a portion of the hydrocarbon effluent stream from the last alkylation zone in the series, is passed to a conventional separation operation, such as fractionation in an isobutane stripper, in order to recover the alkylate product. The hydrocarbon effluent from the last alkylation zone in the series which is charged to the separation operation to recover the alkylate product is herein termed the reaction product stream." I v The alkylation reaction product produced in the preferred embodiment of the present process, when isobutane is employed as the isoparaffin, and propylene and butylenes are utilized as the olefin-acting reactant, includes C C saturated hydrocarbons resulting from the alkylation reactions of the isoparaffin with the olefin-acting reactant in both the first and second alkylation zones. The primary products include, for example, dimethylpentanes and trimethylpentanes. It is known that more highly branched hydrocarbons possess superior properties as motor fuel components, and the present invention is directed, in part, to providing an alkylation reaction product containing a higher ratio of more highly branched hydrocarbons, such as trimethylpentanes, to less branched hydrocarbons, such as dimethylhexanes. The foregoing is accomplished through the use of the series flow of isoparaffin and through recycle of a portion of the hydrocarbon effluent from the first alkylation zone to provide optimum alkylation conditions, including an extremely high mole ratio of isoparaffin to olefin in the alkylation reactors. It is thus apparent that the present invention provides a process for Y producing a superior motor fuel alkylate product by a method moreeconomical and convenient than has been available in the prior art.

I claim as my invention:

1. A process for producing an alkylation reaction product from an isoparaffinic reactant and an olefinacting reactant which comprises the steps of:

a. contacting said isoparaffinic reactant with a first portion of said olefin-acting reactant and with a first hydrogen fluoride alkylation catalyst in a first alkylation zone at alkylation conditions;

b. removing the resultant reaction mixture from said first zone and separating the same into a catalyst phase and a hydrocarbon phase containing alkylate and unreacted isoparaffinic reactant;

c. recycling a first portion of said hydrocarbon phase to said first zone;

d. commingling a second portion of said hydrocarbon phase with-a second portion of said olefin-acting reactant and with a second hydrogen fluoride alkylation catalyst, said first and second portions of the hydrocarbon phase being of the same composition and both containing alkylate and unreacted isoparaffinic reactant;

e. subjecting the mixture formed in step (d) to alkylation conditions in a second alkylation zone; and

f. recovering said alkylation reactionproduct from the effluent of said second zone.

2. The process of claim 1 wherein said isoparaffinic reactant is selected from isobutane and isopentane.

3. The process of claim 1 wherein said olefin-acting reactant is selected from propylene, butylenes and amylenes.

4. The process of claim 1 wherein said olefin-acting reactant is a C -C alkyl fluoride.

5. The process of claim 1 wherein at least a portion of said effluent from said second zone is fractionated to recover said alkylation reaction product and form an isoparaffin recycle stream and at least a portion of the isoparaffin recycle stream is introduced into said first alkylation zone.

6. The process of claim 1 wherein from about 20 volume percent to about volume percent of said olefinacting reactant is supplied to said first alkylation zone.

carbon phase is recycled to said first alkylation zone.

Claims

1. A PROCESS FOR PRODUCING AN ALKYLATION REACTION PRODUCT FROM AN ISOPARAFFINIC REACTANT AND AN OLEFIN-ACTING REACTANT WHICH COMPRISES THE STEPS OF: A. CONTACTING SAID ISOPARAFFINIC REACTANT WITH A FIRST PORTION OF SAID OLEFIN-ACTING REACTANT AND WITH A FIRST HYDROGEN FLUORIDE ALKYLATION CATALYST IN A FIRST ALKYLATION ZONE AT ALKYLATION CONDITIONS; b. REMOVING THE RESULTANT REACTION MIXTURE FROM SAID FIRST ZONE AND SEPARATING THE SAME INTO A CATALYST PHASE AND A HYDROCARBON PHASE CONTAINING ALKYLATE AND UNREACTED ISOPARAFFINIC REACTANT; C. RECYCLING A FIRST PORTION OF SAID HYDROCARBON PHASE TO SAID FIRST ZONE; D. COMMINGLING A SECOND PORTION OF SAID OLEFIN-ACTING REACTANT A WITH A SECOND PORTION OF SAID OLEFIN-ACTING REACTANT AND WITH A SECOND HYDROGEN FLUORIDE ALKYLATION CATALYST, SAID FIRST AND SECOND PORTIONS OF THE HYDROCARBON PHASE BEING OF THE SAME COMPOSITION AND BOTH CONTAINING ALLYLATE AND UNREACTED ISOPARAFFINIC REACTANT; E. SUBJECTING THE MIXTURE FORMED IN STEP (D) TO ALKYLATION CONDITIONS IN A SECOND ALKYLATION ZONE; AND F. RECOVERING SAID ALKYLATION REACTION PRODUCT FROM THE EFFLUENT OF SAID SECOND ZONE.

4. The process of claim 1 wherein said olefin-acting reactant is a C3-C5 alkyl fluoride.

6. The process of claim 1 wherein from about 20 volume percent to about 80 volume percent of said olefin-acting reactant is supplied to said first alkylation zone.

7. The process of claim 1 wherein from about 25 volume percent to about 60 volume percent of said hydrocarbon phase is recycled to said first alkylation zone.