FI60698C - OIL ALKYLERING AV ISOBUTAN MED EN PROPEN / BUTENBLANDNING - Google Patents

Description

M (11) MOON, LUTUSJATKA, SU /: n /: Q a

Ma l J '' UTLÄGGN I NGSSKRIFT OU 0 7 O

C ^ jjPatent granted 10 03 1982 Patent acddelat ^ T ^ (51) Kv.lk.3 / lnt.CI.3 C 0? C 2/62 FINLAND —FINLAND (21) FWmlh.k.mui-FWttn.dknln * 21 + 26 / 7¾ (22) Htkamitpllvi - Aittöfcnlnftdtg 15.08.7¾ (23) Alkupllvt — GHtlghuttdag 15.08.7¾ (41) Translators offantllg 16.02.76

Patent and Registration Board .............. . .

_ '(44) Date of letter and letter. -

Patents and Registration Authorities »Utlagd och utl. * Krift # n publkarad 30.11.8l (32) (33) (31) Pyydetty« uolkou »- Bagtrd prloritat (71) & Mt. Prospect Roads, Des Plaines, Illinois 600l6, USA (US) 1 (72) Robert Francis Anderson, La Grange Park, Illinois, USA (US) (7¾) Berggren Oy Ab (5¾) Method for alkylation of isobutane with a propylene / butene mixture - Förfarande för alkylering This invention relates to a process for the alkylation of isobutane with a propylene-butene mixture using a hydrogen fluoroalkylation catalyst. Thus, there is also an improved alkylation process for obtaining hydrocarbon motor fuel components.

Alkylation of isoparaffinic hydrocarbons such as isobutane, isopentane and the like with olefinic hydrocarbons such as propylene, butylenes, amylenes and olefinically active compounds such as C 1 -C 4 alkyl halides using hydrogen fluoride as a catalyst is well known as a commercially important process for The C 1 -C 6 hydrocarbons normally produced by the olefin alkylation reaction of isoparaffins are termed "alkylate". Alkylate is particularly useful as a motor fuel blender due to its high engine and research octane number. It can be used to improve the total octane number of gasoline sources to meet the requirements of modern car engines. High octane alkylate fuel components are particularly relevant in the manufacture of a motor fuel of sufficient quality of 2,60698 when it is not desired to use alkyl lead compounds in the motor fuel to meet octane requirements. A continuing goal in the alkylation industry is to make the hydrogen fluoride catalyzed alkylation process more economical than conventional alkylation processes and to be able to provide an alkylate product with higher engine and research octane numbers than is possible using conventional processes.

In general, commercial olefin alkylation processes for isoparaffins use isobutane as the isoparaffin reagent and propylene, butylenes, amylenes, or mixtures thereof as the olefinically active agent. Isobutane and olefin are typically contacted with a fluorocarbon catalyst in an alkylation reactor and mixed to form an emulsion or alkylation reaction mixture. When the alkylation reaction between isobutane and olefin is substantially complete, the reaction mixture of hydrocarbons and catalyst is removed from the reactor and allowed to deposit to separate the immiscible hydrocarbon and catalyst phases. The hydrofluorocarbon phase thus separated is returned to the reactor for new catalytic use. The hydrocarbon phase produced by the precipitation process is further treated, normally by fractional distillation to recover the α] chylate product and to separate the unchanged isobutane for later use in the alkylation reactor, recovering it from the fractionation step.

It has been found necessary to maintain reactor temperature, relative amounts of catalyst and charged hydrocarbons, catalyst strength, and other treatment conditions in narrow areas to provide a high quality alkylate product. A molar ratio of isobutane to olefin of about 10: 1 or more in the hydrocarbon feed to the alkylation reactor is a prerequisite for the formation of a high octane alkylate in hydrogen fluoride catalyzed alkylation. The molar ratio of isobutane to olefin in the hydrocarbon feed to the alkylation reactor is commonly known as the "external" molar ratio of isobutane / olefin. The external isobutane / olefin molar ratio must be distinguished from the molar ratio of isobutane to olefin in the alkylation reaction mixture formed in the alkylation reactor, which ratio is commonly referred to as the "internal" isoparaffin / olefin molar ratio. In alkylation processes using a hydrogen fluoride catalyst, the quality of the alkylate product is substantially improved by increasing the external isobutane / olefin molar ratio, but not by increasing the internal isobutane / olefin molar ratio.

3 60698

That is, only the ratio of isobutane to olefin in the hydrocarbon feed to the alkylation reactor is relevant to the production of the high octane product in hydrofluorocarbon processes, and not the concentration of isobutane in the reaction mixture in the alkylation reactor. The opposite is true for sulfuric acid alkylation, where the quality of the alkylate product is improved by increasing the internal isobutane / define molar ratio, i. with a higher concentration of isobutane in the reaction mixture in the alkylation reactor. In hydrogen fluoride catalyzed alkylation processes, it has been found desirable to use as high an isobutane / olefin molar ratio as is economically feasible in the hydrocarbon feed to the reactor, as this will improve the quality of the alkylate product. An example of this improvement is the improved octane number of the alkylate product when a higher external isobutane / olefin molar ratio is used. Thus, in conventional processes, a very substantial portion of the isobutane must be passed unreacted through the reactor and must be returned to the reactor after fractionation of the hydrocarbon phase produced in the deposition apparatus. This fractional distillation of the layered hydrocarbon phase is performed to separate excess unreacted isobutane from the higher boiling alkylate product. Thus, large amounts of isobutane must be passed unreacted through the alkylation reactor and layer and separated from the alkylate product by fractional distillation in a conventional fluorohydrogen alkylation process. This required fractional distillation step makes it necessary to use a high-capacity fractional distillation apparatus with high energy consumption to evaporate the isobutane and separate it from the heavier alkylate.

In the past, attempts have been made in the art to reduce the problem of the high isobutane requirement, for example by continuously circulating an emulsion of hydrogen fluoride catalyst, isobutane and reaction products (alkylation reaction mixture) through the alkylation reactor in an attempt to partially utilize the isobutane in the reaction mixture. This method of increased isobutane / olefin molar ratio was found to be useful in sulfuric acid catalyzed alkylation processes, as the quality of the alkylate product is improved in sulfuric acid processes when the internal isobutane / olefin molar ratio is increased by increasing the concentration of isoparaffin in the alkylation reactor. At this early stage of the hydrogen fluoride alkylation process, the emulsion was removed from the alkylation reactor and charged back to the reactor along with fresh olefin and fresh and recycled isoparaffin. A variation of the emulsion recycling system was accomplished by passing a reaction mixture emulsion of hydrogen fluoride catalyst, isoparaffin, and reaction products from the first alkylation zone to the second alkylation zone, where the emulsion was contacted with a fresh olefin feed and further alkylation occurred. These early attempts to achieve a high internal isoparaffin / olefin molar ratio in the alkylation reactor with process schemes analogous to those used in sulfuric acid alkylation failed to achieve any improvement in alkylate product quality in hydrogen fluoride catalyzed processes and have generally been discarded in commercial processes. It has been found that the quality of the alkylate product in hydrogen fluoride catalyzed alkylation is improved only when the external isobutane / olefin molar ratio is increased and that the quality of the product is not improved by increasing the internal isobutane / olefin molar ratio. Thus, the conditions required for the successful use of a hydrogen fluoride catalyzed alkylation process have not been found to be analogous in this respect to those required for the successful use of a sulfuric acid alkylation process. Significant costs and difficulties are therefore still encountered in commercial hydrofluorocatalyzed processes in an attempt to achieve the required external isobutane / olefin molar ratio in the hydrocarbon feed to the alkylation reactor. The required high external isobutane / olefin molar ratio used in conventional processes necessitates the passage, separation and recycling of excessive amounts of isobutane in a conventional alkylation system. This problem is substantially reduced by the process of the present invention.

There have been previous attempts in the art to use multiple alkylation reactors for a variety of reasons, but never to obtain a higher isoparaffin / olefin molar ratio to the feed to the alkylation reactor as presented in this invention. For example, U.S. Patent 2,256,880 discloses the use of multiple reactors and layers in a sulfuric acid catalyzed alkylation process of isoparaffin with olefins. The coarse hydrocarbon phases recovered from the layer system of each reactor are subjected to equilibrium distillation between successive steps to separate the isoparaffin vapor from the higher boiling alkylation reaction product which remains a liquid in equilibrium separation. The vaporized iso-paraffin is cooled and then returned. A portion of the liquid alkylation reaction product may be passed to the next step, but at least a portion of the liquid remaining after equilibrium distillation between steps is passed directly to fractional distillation to recover the product. The avoidance of accumulation of alkylation reaction products in reactors and the use of extremely low isoparaffin / olefin molar ratios in the alkylation reaction zone are also disclosed in the above patent, in contrast to the processes used in the process of this invention using a hydrogen fluoride catalyst. U.S. Patent 2,820,073 also discloses the use of multiple alkylation reactors and builders in the olefin alkylation of isoparaffins, but uses fractional distillation equipment between each successive step to separate unreacted isoparaffin from the alkylation reaction product in a layered hydrocarbon phase. The isoparaffin thus separated is recovered as steam, cooled and passed to the next step. The reaction product is recovered. U.S. Patent 3,007,983 discloses the use of two reactors and a layer for the olefin alkylation of isoparaffins. The layered hydrocarbon phase recovered from each step is subjected to equilibrium distillation to separate the isoparaffin as a vapor from the higher boiling alkylation reaction product, which remains a liquid. The isoparaffin vapor is cooled and passed to the next step. The alkylation reaction product is recovered as a liquid. The teachings of the latter patent focus primarily on self-cooling in sulfuric acid alkylation. U.S. Patent 3,236,912 discloses the alkylation of isobutane with propylene and butylene in one reactor and layer system to prepare one alkylation reaction product and the alkylation of ethylene with isobutane in another reactor layer system to produce another alkylation reaction product. The ethylene reagent is passed through a first reactor-bed system mixed with propylene, butylenes and isobutane, but is not allowed to react in the first system. When it is desired to recover the first and second alkylation reaction products as a mixture, the layered hydrocarbon phase containing unreacted ethylene is recovered from the first reactor-layer system and passed directly to the second reactor-layer system where the ethylene in the layered hydrocarbon phase is reacted with isobutane. It may be possible to pass ethylene through the first reactor-bed system without an alkylation reaction of ethylene, since ethylene is not reacted with isoparaffin to form an alkylation reaction product using a hydrofluoric or sulfuric acid catalyst. It is clear that if ethylene could react to form a 6 6 0 6 9 8 alkylate under conventional propylene or butylene alkylation conditions, ethylene would react in the first reactor-bed system. When ethylene is contacted with a hydrogen fluoride catalyst under propylene and butylene alkylation conditions, it forms a stable ethyl fluoride which is inert to the alkylation reaction.

It is an object of the present invention to provide a process for the alkylation of isobutane with a propylene-butene mixture using a hydrogen fluoroalkylation catalyst.

Another object of the present invention is to provide a hydrogen fluoride catalyzed alkylation process for producing an alkylate product of excellent quality and utility as a blending component for motor fuel.

It is a further object of the present invention to provide an economical process for increasing the external isoparaffin / olefin molar ratio in a hydrogen fluoride catalyzed olefin alkylation process of isoparaffins.

It is a further object of the present invention to provide a hydrogen fluoride catalyzed olefin alkylation process for isoparaffins with a reduced need for fractional distillation to separate the alkylate product from the unreacted isoparaffin to be returned to the alkylation reactor.

Thus, the present invention relates to a process for producing an alkylation reaction product from isoparaffin and a monoolefin selected from propylene and butylenes, which process comprises the steps of: (a) mixing a portion of a propylene / butene mixture with isobutane and contacting the resulting hydrocarbon mixture with a first hydrogenation alkylation; in an alkylation reaction zone under hydrogen fluoroalkylation conditions to form an alkylation reaction mixture; (b) removing the alkylation reaction mixture from the first alkylation reaction zone, depositing the reaction mixture to provide a layered hydrocarbon phase and a hydrofluorocatalyst phase, and returning the catalyst phase to the first alkylation reaction zone; (c) mixing a second portion of the propylene / butene mixture in an amount of about 10-1000 mole- $ of the first propylene / butene portion to at least a portion of the layered hydrocarbon phase obtained in (b) and contacting the second hydrocarbon mixture thus obtained in the second step (a). ) with said identical hydrofluorocatalyst phase in the second alkylation reaction zone under substantially the same alkylation conditions as in (a) to form a second alkylation reaction mixture; (d) removing the second alkylation reaction mixture from the second alkylation reaction zone, depositing the second reaction mixture to provide a second deposited hydrocarbon phase and a second hydrofluorocatalyst phase, and returning the second catalyst phase to the second α] alkylation reaction zone; and (e) fractionally distilling the second layered hydrocarbon phase to provide a higher boiling product stream and a lower boiling isobutane stream, returning the isobutane stream to the first alkylation reaction zone, and recovering the alkylation reaction product from the product stream.

The more important advantages of the process of this invention over previous alkylation processes in the art are those resulting from a substantial reduction in the total amount of isobutane required compared to the amount of olefin reagent used in the process. By introducing all but only part of the isobutane as a mixture into the first alkylation reactor, a substantially smaller amount of isobutane is required in the first hydrogen fluoride catalyzed alkylation reaction to provide a sufficient external molar excess of isobutane relative to the amount of olefin used. The layered hydrocarbon phase recovered from the first layer is then mixed with the second olefin feed to form a second hydrocarbon reactor feed which is fed to the second alkylation reactor and contacted with the second fluorocarbon catalyst phase. The layered hydrocarbon phase recovered from the second layer is then fractionally distilled to separate and react the unreacted isobutane to the first reactor and recover the desired alkylation reaction product. The amount of isobutane thus separated by fractional distillation and recovered is substantially less than that found in conventional hydrogen fluoride catalyzed isobutane olefin alkylation processes using the same external isobutane / olefin molar ratio. Alternatively, a conventional amount of isobutane can be used in the feed to the first alkylation reactor to give a higher octane alkylate product than in conventional alkylation processes. In the process of this invention, the unreacted isoparaffin contained in the entire layered hydrocarbon phase recovered from the first reactor bed system is mixed with the second batch of isobutane / olefin molar ratio of the olefinic feedstock to provide a second hydrocarbon feed to the second alkylation reactor. This second hydrocarbon feed is then contacted with the second fluorocarbon catalyst phase in the second reactor. When the second batch of olefin feed is mixed with the first layered hydrocarbon phase outside the second reactor and the resulting mixture of olefin feedstock and layered hydrocarbon phase is then fed to the second reactor, the effective external isoparaffin / olefin molar ratio increases substantially to provide quality from the second reactor. In contrast, prior art processes in which isobutane mixed with a hydrofluorocarbon catalyst is used to feed multiple alkylation zones fail to provide isobutane that operates to produce a high external isoparaffin / olefin molar ratio to the reactor feed, resulting in a poor quality alkylate product.

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

The accompanying drawing 1 is a schematic description of a preferred embodiment of the process of the present invention. Thus, in the embodiment shown, the hydrocarbon to be alkylated is isobutane and the olefinic feedstock is a mixture of propylene and butylenes.

Referring to the drawing, a conventional olefin alkylation feedstock is continuously fed through line 1 at a rate of about 300 mol / h propylene and 300 mol / h butylenes along with smaller amounts of other hydrocarbons normally present in the commercial olefin feedstock but not required for the process. comprising 120 mol / h isobutane, 35 mol / h n-butane and 70 mol / h propane. The continuously fed olefinic feedstock in pipe 1 is divided into two equal volumes of streams which are fed to pipes 2 and 3. Two batches of olefinic feedstock are fed to pipes 2 and 3, each at 150 mol / h propylene, 150 mol / h butylenes, 60 mol / h isobutane, 17.5 mol / h 9 60698 n-butane and 35 mol / h propane. Conventional replenishment butane from elsewhere is introduced into the process via line 4, fed to line 2 and mixed with the batch of olefin feedstock therein. The make-up isobutane stream is passed through line 4 at a rate of 500 mol / h isobutane together with conventional unnecessary amounts of unreacted hydrocarbons comprising about 15 mol / h n-butane and about 10 mol / h propane. The mixed supplemented butane and part of the olefin feed continue through the pipe 2. The recovered isobutane from tube 24 is passed to tube 2 and mixed with its contents. The recovered isobutane is introduced into tube 2 at a rate of 3550 mol / h isobutane together with a certain amount of other unreacted hydrocarbon feedback resulting from inaccurate fractional distillation and comprising 525 mol / h n-butane and 225 mol / h propane. The total hydrocarbon feed to reactor 5 thus contains 150 mol / h propylene, 150 mol / h butylenes, 4110 mol / h isobutane and non-reactive hydrocarbons comprising 270 mol / h propane and 557.5 mol / h n-butane. The external isobutane / olefin molar ratio in the feed to reactor 5 is thus 13.7. The combined feed is passed through line 2 to reactor 5 and mixed with a conventional fluoro-hydrogen alkylation catalyst to form a reaction mixture. The fluoro-hydrogen alkylation catalyst is fed to the reactor 5 via line 10. The catalyst contains about 85% by weight of acid, less than 1% by weight of water, the remainder being formed from a conventional organic diluent. The fluorocarbon alkylation conditions maintained in reactor 5 include a temperature of about 32-37 ° C and a pressure sufficient to keep the hydrocarbons and catalyst in the liquid phase. A catalyst / hydrocarbon volume ratio of about 1: 1-2: 1 is used. The heat generated in the alkylation reaction is removed by using indirect heat exchange in the reactor 5. Cooling water is fed through line 6 to reactor 5 and passed to indirect heat exchange with the reaction mixture. Spent cooling water is removed via pipe 7. After a contact time of about 0.1-5 minutes, the reaction mixture in reactor 5 is removed and passed through line 8 to bed 9. The reaction mixture is allowed to stand without stirring in layer 9, whereby the fluorocarbon catalyst forms a heavier phase and the hydrocarbon components of the reaction form a lighter layer. The catalyst phase is removed from the bottom of the layer 9 via a pipe 10 and returned to the reactor 5 for new catalytic use. Regeneration of the catalyst used in the reactor 5 can be carried out by directing the catalytic side stream from the pipe 10 to a conventional regeneration device. Referring again to the layer 9, the first layered hydrocarbon phase formed therein is removed from the upper end of the layer 9 via a pipe 11, led to a pipe 3 and mixed with the second part of the olefin feed therein. The first layered hydrocarbon phase passed through line 11 contains about 3800 mol / h isobutane, essentially no olefins, 557-5 mol / h n-butane, 280 mol / h propane and 300 mol / h alkylate. The combined hydrocarbon feed from line 3 to reactor 12 contains about 3860 mol / h isobutane, 150 mol / h propylene, 150 mol / h butylene, 575 mol / h n-butane, 315 mol / h propane and 300 mol / h alkylate. The external isobutane / olefin molar ratio of the hydrocarbon feed to reactor 12 is thus about 13: 1. The reaction conditions used in reactor 12 are similar to those used in reactor 5, i. a temperature of about 32-37 ° C »an acid / hydrocarbon volume ratio of about 1: 1-2: 1 and a pressure sufficient to keep the components of the reaction mixture in the liquid phase. The fluorocarbon catalyst, containing about 85 wt% acid, less than about 1 wt% water, with the remainder being formed from the organic diluent, is fed to reactor 12 via line 19 and thoroughly mixed with the hydrocarbon feed from line 3 to form a second reaction mixture. Cooling water is fed through line 13 and is passed to indirect heat exchange with the reaction mixture in reactor 12. Spent cooling water is removed via pipe 19. After a contact time of about 0.1-5 minutes, the reaction mixture is removed from the reactor 12 and passed through line 15 to the reaction liquor 16. The reaction mixture of catalyst, reagents and reaction products is maintained in the reactor 16 for approximately 10 minutes at substantially the same temperature and pressure as in reactor 12. The reaction mixture is then removed and passed through line 17 to layer 18. The reaction mixture is allowed to stand without stirring in layer 18 to facilitate separation of the catalyst and hydrocarbons into separate phases. The heavier catalyst phase is removed from the bottom of the stratifier 18 via line 19 and returned to reactor 12 for the new catalytic use described. A portion of the catalyst in tube 19 may be subjected to a conventional regeneration process if desired. The second layered hydrocarbon phase is removed from the layer 18 and passed through line 20 to the isobutane stripper 21 at a rate of about 325 mol / h propane, 3550 mol / h isobutane, 575 mol / h n-butane and 600 mol / h alkylate (C 1-4 hydrocarbons). In the isobutane stripper 21, the second layered hydrocarbon phase is fractionally distilled to separate the lighter isobutane feed stream and the heavier alkylate product stream. In the conventional fractionation process 11,60698 performed in the isobutane stripper 21, conventional auxiliary equipment not visible, such as intermediate bottoms, bottom boilers, reflux condensers, etc., all known in the art, can be used. The alkylate product is removed as a bottom product from the isobutane stripper 21 via line 22, discharged from the process and recovered as motor fuel or for other desired uses at a rate of 600 mol / h. Normal butane, a by-product of the process of the embodiment shown, is removed as a side stream through line 23 at a rate of 50 mol / h. Conventional isobutane feedback is removed as a side stream from the higher bottom of the isobutane stripper 21 through pipe 24. The isobutane feedback stream is passed from the isobutane stripper 21 through line 24 at a rate of 3320 mol / h isobutane, 500 mol / h n-butane and 225 mol / h propane. The isobutane feedback stream in line 24 is fed to line 2 as described above. The upstream is removed from the isobutane stripper 21 and passed through line 25 to a conventional propane removal device 26. The upstream is led from the isosulfurizer 21 at a rate of 100 mol / h propane, 230 mol / h isobutane and 25 mol / h n-butane. In the propane removal device 26, the feed from line 25 is fractionally distilled to separate propane from isobutane and n-butane. Isobutane and n-butane are removed at a rate of 230 mol / h of isobutane and 25 mol / h of n-butane as a by-product and passed through line 27 to line 24 for use in the isobutane feedback stream. Propane mixed with some hydrogen fluoride is removed upstream through line 28 at a rate of 100 mol / h of propane and passed through line 28 to line 29 mixed with hydrogen fluoride from line 36. The mixture of propane and hydrogen fluoride in tube 29 is passed to condenser 30 and cooled to liquefy propane and acid. The liquefied propane and hydrogen fluoride are then passed through line 31 to layer 32. Most of the hydrogen fluoride passed to layer 32 separates as a relatively pure acid heavy phase and is removed through line 33. This relatively concentrated acid can be returned to the catalyst feedback streams in tubes 10 and 19 by conventional equipment not shown. The liquefied propane phase in the layer 32 is removed and passed through line 34 to a hydrogen fluoride stripper 35, where the propane is fractionally distilled to separate any remaining acid therefrom. The acid is removed upstream through line 36, returned to line 29 and treated as described above. Propane is removed as a by-product from the bottom of the hydrogen fluoride stripper 35 through line 37 at a rate of 100 mol / h. Certain conventional devices and procedures necessary for the operation of the above-described embodiment have been omitted from the drawing and its description, such as pumps, valves, intermediate floor cookers, etc. The use and placement of such conventional headings will be apparent to those skilled in the art. The foregoing description describes some of the advantages of the present invention as implemented in a hydrogen fluoride catalyzed isoparaffin olefin alkylation process. For example, hydrocarbons are fed to reactors 5 and 12 at high external isobutane / olefin molar ratios of about 13: 1, which are necessary to produce a sufficiently good quality alkylate. However, the fractionation requirements in the isobutane stripper 21 need only be sufficient to separate the isobutane in an amount corresponding to a total isobutane / olefin molar ratio of less than 7: 1. The quality of the alkylate produced is as good or better than that of the alkylate produced by conventional alkylation processes using a conventional external isobutane / olefin molar ratio of 12: 1, while substantially reducing fractional distillation requirements, which means savings in capital and operating costs. In contrast, an alkylate produced by a conventional hydrogen fluoride catalyzed alkylation process using a 7: 1 total isobutane / olefin molar ratio would be of poor quality and would not be suitable as a blending feedstock for refining low gasoline source components to the desired octane level.

Conventional isobutyl alkylation feedstocks are suitable for use in this process. Such conventional complementary isobutane feedstocks may contain some unreacted hydrocarbons such as normal paraffins. For example, a conventional commercial isobutylalkylation feedstock generally contains about 95% by weight isobutane, 4% by weight n-butane and 1% by weight propane.

The conventional propylene / butene feedstock, which is particularly preferred for use in this process, may be derived from petroleum refining operations such as catalytic cracking and may therefore contain significant amounts of saturated hydrocarbons, lighter and heavier olefins, etc.

1360698 The hydrogen fluoride catalysts used in this process are well known in the art. In general, the hydrogen fluoroalkylation catalyst contains n.

75 wt.% Or more of titratable acid, about 5 wt.% Or less of water with the remainder being an organic diluent. Such an alkylation catalyst is suitable for use in both the first and second alkylation steps in this process. A particularly preferred catalyst for use in both alkylation steps contains about 85% by weight of acid and less than 1% by weight of water, the remainder being an organic diluent.

Several alkylation reaction zones suitable for use in the process of this invention are known in the art. For example, but not limited to, alkylation reactors of the type described in U.S. Patents 3,456,033, 3,469,949, and 3,501,536 may be suitably used as both alkylation reactors for this process. The alkylation conditions specifically associated with the alkylation reactors or other suitable conventional alkylation reactors described in the patents listed above may be used in connection with the embodiments of this invention described herein.

In one embodiment of this process, suitable fluorocarbon alkylation conditions include a temperature of about 18-93 ° C, a pressure sufficient to keep the reagents and the hydrogen fluoride catalyst in the liquid phase, and a contact time between the hydrocarbons and the catalyst of about 0.1-30 minutes. In a preferred embodiment using a hydrogen sulfide alkylation catalyst containing about 85% by weight of acid, a catalyst / hydrocarbon volume ratio of about 1: 1 to 5: 1 is recommended, and a temperature of about 10 to 65 ° C is preferred in the alkylation reaction zones.

In a particularly preferred embodiment, the mixture of hydrogen fluoride catalyst, reagents and reaction products formed in the alkylation reactor is passed through a reaction soaking device. In the description of the preferred embodiments presented herein, it is intended that both the 60698 m alkylation reactor and the reaction soak apparatus, if used, be included within the scope of the phrase "alkylation reaction zone". Suitable reaction leaching devices are well known in the art. For example, the reaction soaking devices described in U.S. Patents 3,586,387 and 3,607,970 can be suitably used in this process. Such reaction soaking devices are typically vessels equipped with perforated bottoms, spacer zones, etc. to maintain the alkylation reaction mixture in the form of a fairly homogeneous mixture or emulsion for a predetermined length of time. The alkylation reaction mixture of catalyst and hydrocarbons is maintained in the reaction solubilizer for a time depending on the composition of the reaction mixture. A residence time of about 1-30 minutes in the reaction dissolution apparatus is recommended. The temperature and pressure maintained in the reaction leaching apparatus are the same as the temperature and pressure maintained in the associated alkylation reactor.

Devices for stopping the reaction mixture effluent from the alkylation reaction zone to separate the quenched hydrocarbon phase and the hydrofluorocatalyst phase are well known in the alkylation art. Generally, the effluent alkylation reaction mixture recovered from the alkylation reactor or soaking apparatus consists of a mixture of unreacted isoparaffin, alkylation reaction products, hydrofluorocarbon catalyst, and catalyst-soluble organics, optionally with small amounts of light hydrocarbons, etc. When mixed with light hydrocarbons, etc. when layered, the alkylation reaction products, isoparaffins, and light hydrocarbons form a lighter layered hydrocarbon phase. The hydrofluorocatalyst and the hydrocarbons soluble in the catalyst form a separate phase. The layered hydrocarbon phase is then simply mechanically separated from the catalyst phase. The temperature and pressure maintained during such a deposition operation are substantially the same as those described above in connection with the fluorohydrogen alkylation conditions used in the reactor. The hydrocarbons and catalyst are maintained in the liquid phase during the deposition separation operation.

Some kind of equipment for removing heat from the alkylation zone is necessary due to the optimum process control. Several different devices for implementing a heat poetetto are well known. For example, in one embodiment, the heat generated in the alkylation reaction can be removed directly from the alkylation reactor by indirect heat exchange between the cooling water and the reaction mixture in the reactor.

15 6069Θ

The layered hydrocarbon phase recovered from the first deposition operation is combined with the second portion of the olefin feed to provide a hydrocarbon feed to the second alkylation reactor. Thus, the first layered hydrocarbon phase is used to provide a high external isobutane / olefin molar ratio in the feed to the second alkylation reactor. The hydrocarbon feed formed from the first layered hydrocarbon phase and the second portion of the olefin reagent is then fed to the second alkylation reactor and contacted with the second fluorocarbon alkylation catalyst therein. It is intended that sufficient isobutane be fed to the first alkylation reactor so that no other externally derived isobutane needs to be added to the mixed second portion of the olefin feed and the first layered hydrocarbon phase prior to feeding this hydrocarbon mixture to the second alkylation reactor. The same general alkylation conditions are used in the second alkylation step as in the first alkylation step. Although the reaction soaking device can be used in connection with both the first and second alkylation reactors, in the preferred embodiment the reaction soaking device is used only in connection with the second alkylation reactor. The temperature and pressure used in the reaction soaking apparatus are the same as those used in the reactor associated with the sieve. Upon completion of the reaction of all olefins fed to the second alkylation reaction zone, the resulting reaction mixture is deposited by any suitable, conventional method to provide a second layered hydrocarbon phase and recover the second fluorocarbon catalyst phase for return to the second alkylation reaction zone. The second layered hydrocarbon phase is recovered from the second layering operation and passed to conventional isobutane stripping fractionation, where the heavier alkylate product is separated from the lower boiling, unreacted isobutane and any hydrogen fluoride that may be present in the second layered hydrocarbon phase. Any suitable method used to partition the recovered, deposited hydrocarbon phase from the separator can be used to separate the higher boiling alkylate product from the lower boiling isobutane feed stream.

The alkylation reaction product produced in a preferred embodiment of this process generally consists of saturated C 1 -C 6 hydrocarbons resulting from alkylation reactions of isobutane with olefins in both the first and second alkylation zones. The main components of the product are, for example, dimethylpentanes and tri-1660698 methylpentanes. It is well known that more branched hydrocarbons generally have excellent properties as a motor fuel. This invention is directed, in part, to providing a motor fuel catalyst containing a higher proportion of more branched hydrocarbons, such as trimethylpentanes, than less branched hydrocarbons, such as dimethylhexanes. This advantage is achieved by using in this process high external isobutane / olefin molar ratios in both alkylation reactions, which ratios were not achievable in a prior art process on a general economic or operational basis. Thus, it is clear that the present invention provides a novel process for producing an excellent motor fuel alkylate product by a process that is more economical and easier to use than has been available in prior hydrofluorocatalyzed alkylation processes in the art.

Example To demonstrate the benefits and advantages of the present invention over prior art alkylation methods, two runs were performed, one using the method of the present invention and the other using a conventional alkylation procedure. The olefin feedstock used in both times contained 48% by weight? propylene, 10.4 weight? butene-1, 26 wt. butene-2 and 15.6 wt. isobutylene. Isobutane was used as the isoparaffin feedstock. Run 1 used the method of this invention and two-step alkylation, and run 2 used the conventional one-step method. Both run 1 and run 2 used the same temperature, pressure, and catalysts. The hydrogen fluoride catalyst used contained 89% by weight of? hydrogen fluoride, 10 weight? organic diluent and 1 weight? of water. The temperature used for the alkylation reactions was about 37 ° C. The pressure used was sufficient to keep the reagents and catalyst liquids. At both times, the hydrocarbon feed and catalyst were continuously fed to a conventional bench-scale alkylation reactor at a catalyst / hydrocarbon weight ratio of about 1.5: 1 and a residence time of 10 minutes was maintained in the alkylation reactor at both 17,60698 times. In Run 1, using the method of the present invention, the olefin feedstock was divided into two parts. The entire isoparaffin feedstock and the first portion of the olefin feedstock were mixed together and the resulting hydrocarbon feed was fed to a conventional alkylation reactor and contacted with the fluorocarbon catalyst therein under the conditions described above to form a first reaction mixture. After a defined residence time, the first reaction mixture was removed and layered in a conventional manner to separate the first layered hydrocarbon phase from the layered catalyst phase. The resulting first layered hydrocarbon phase and the second portion of the olefin feedstock were continuously fed to a conventional alkylation reactor and contacted with the hydrofluorocarbon catalyst therein under the alkylation conditions described above to form a second reaction mixture. No additional isobutane was added to the second reaction mixture, with the isobutane contained in the first layered hydrocarbon phase being the only source of isobutane in the second reaction mixture. After a defined residence time, the second reaction mixture was removed and layered in a conventional manner to separate the second layered hydrocarbon phase from the layered catalyst phase. The second layered hydrocarbon phase was recovered, partitioned by distillation to separate the C 1-4 and heavier hydrocarbons, and the C 1-4 hydrocarbons were recovered as the alkylate product of Run 1. The alkylate product of Run 1 was analyzed and the results are shown in the table. In Run 2, which used a conventional one-step alkylation procedure, the entire olefin feedstock was continuously fed to the conventional alkylation reactor at a rate corresponding to the combined feed rate of the first and second portions of the olefin feedstock in Run 1. In Run 2, all of the isobutane feedstock was continuously fed to the reactor at the same rate as used in Run 1. The olefin feedstock and the isobutane feedstock were mixed together and the resulting hydrocarbon mixture was fed to an alkylation reactor and contacted therewith with a hydrogen fluoride catalyst under the alkylation conditions described above to form a reaction mixture. After a residence time of 10 minutes, the reaction mixture was removed from the reactor and deposited in a conventional manner to separate the deposited catalyst phase from the deposited hydrocarbon phase. The precipitated hydrocarbon phase was recovered, fractionated to separate the C The alkylate product of Run 2 was analyzed and the results are shown in the table.

18 60698

Table

Alkylate product analysis

Run 1 Run 2 C0 hydrocarbons, weight # 61.5 56.1

Cg + hydrocarbons, weight # 6.1 9.6

Trimethylpentanes, wt. # 56.3 50.4

Dimethylhexanes, weight # 5.15 5.8

Research octane number (clear) 95.2 94.5

Engine octane number (clear)

Referring to the table, it appears that the process of this invention (Run 1) provided a better alkylate product compared to conventional alkylation procedures (Run 2). However, no additional isobutane was used in Run 1 and the fractional distillation required to separate the C 1-6 alkylate hydrocarbons was similar in Run 1 and Run 2. The figures in the table show that the process of this invention provides an alkylate product with higher octane numbers and less unwanted heavy fractions ( C ^ + - hydrocarbons).

Claims (1)

A process for preparing an alkylation reaction product from isobutane and a propylene / butene mixture, characterized in that it comprises the steps of: (a) mixing a portion of the propylene / butene mixture with isobutane and contacting the resulting hydrocarbon mixture with a fluorocarbon alkylation catalyst to form an alkylation reaction mixture; (b) removing the alkylation reaction mixture from the first alkylation reaction zone, depositing the reaction mixture to provide a layered hydrocarbon phase and a hydrogen fluoride catalyst phase, and returning the catalyst phase to the first alkylation reaction zone; (c) mixing a second portion of the propylene / butene mixture in an amount of about 10 to 1000 moles of the first propylene / butene portion with at least a portion of the layered hydrocarbon phase obtained in (b) and contacting the second hydrocarbon mixture thus obtained with the second, (a) with said identical fluorocarbon catalyst phase in the second alkylation reaction zone under substantially the same alkylation conditions as in (a) to form a second alkylation reaction mixture; (d) removing the second alkylation reaction mixture from the second alkylation reaction zone, depositing the second reaction mixture to provide a second deposited hydrocarbon phase and a second hydrofluorocatalyst phase, and returning the second catalyst phase to the second alkylation reaction zone; and (e) fractionally distilling the second layered hydrocarbon phase to provide a higher boiling product stream and a lower boiling isobutane stream, returning the isobutane stream to the first alkylation reaction zone, and recovering the alkylation reaction product from the product stream.