US3686354A

US3686354A - High octane paraffinic motor fuel production

Info

Publication number: US3686354A
Application number: US112645A
Authority: US
Inventors: George L Hervert
Original assignee: Universal Oil Products Co
Current assignee: Honeywell UOP LLC; Universal Oil Products Co
Priority date: 1971-02-04
Filing date: 1971-02-04
Publication date: 1972-08-22
Anticipated expiration: 1989-08-22

Abstract

High octane paraffinic motor fuel is produced by a combination of alkylating isobutane and a C4 mono-olefin, separating the alkylate into distinct high octane and low octane fractions, and disproportionating the low octane fraction with isobutane and alkylation catalyst to increase its octane number.

Description

United States Patent Hervert [4 1 Aug. 22, 1972 HIGH OCTANE PARAFFINIC MOTOR FUEL PRODUCTION George L. I-lervert, Woodstock, Ill.

Universal Oil Products Company, Des Plaines, lll.

Filed: Feb. 4, 1971 Appl. No.: 112,645

Inventor:

Assignee:

US. Cl ..260/683.43, 260/676 R, 260/683.48, 260/683.62

Int. Cl. ..C07c 3/52, C07c 3/54, C07c 9/ 14 Field of Search ..260/683.46, 683.48, 683.58, 260/683.59, 683.43, 683.45, 683.53, 683.49, 683.1, 676 R, 683.62

References Cited UNITED STATES PATENTS Stahly et al. ..260/683.46

2,368,063 l/ l 945 Elliott ..260/683.46 2,404,934 7/1946 Thompson ..260/ 683.48 2,684,325 7/ 1954 Deanesly ..260/683. l 3,211,803 10/ 1965 Chapman ..260/683.49

Primary Examiner-Delbert E. Gantz Assistant Examiner-G. .l. Crasanakis Attorney-James R. Hoatson, Jr. and Edward W. Remus [57] ABSTRACT High octane parafi'mic motor fuel is produced by a combination of alkylating isobutane and a C, monoolefin, separating the alkylate into distinct high octane and low octane fractions, and disproportionating the low octane fraction with isobutane and alkylation catalyst to increase its octane number.

13 Claims, 1 Drawing Figure PATENTED M22 1912 INVENTOR: George L. Herve/l A 7' TORNEYS HIGH OCTANE PARAFFINIC MOTOR FUEL PRODUCTION FIELD OF THE INVENTION This invention pertains to the production of high octane number motor fuel and involves a combination of alkylation, separation and disproportionation and/or transalkylation. In particular, this invention pertains to the alkylation of isobutane with a C mono-olefin to form an alkylate readily separable into a high octane number fraction and a low octane number fraction and the treatment of the low octane number fraction with isobutane and an alkylation catalyst at reaction conditions suflicient to upgrade the octane number of the low octane number alkylate fraction.

DESCRIPTION OF THE PRIOR ART Production of C to C highly branched parafiins having high octane numbers and anti-knock properties suitable for use in internal combustion engines is of considerable importance to the refinery industry. This is a result of the introduction of high-compression, high-performance automotive engines, aviation engines and the necessity for high octane motor fuels to develop maximum power therefrom. As engine manufacturers develop internal combustion engines with increased performance characteristics, higher octane number motor fuels are required as fuels therein with slight variances in octane numbers becoming a critical parameter in an engine s performance. For example, an octane rating increase in a motor fuel of as little as two or three octane numbers can be the diflerence between a quiet or a knocking engine. In addition, the demand for clear, unpolluted air has placed an emphasis on developing motor fuels for the internal combustion engine which have superior anti-knock properties without the need for lead anti-knock additives, particularly tetraethyl lead, which contribute to the ever-increasing air pollution problem of the world.

A common source of high octane number motor fuels is the catalytic alkylation of low boiling isoparaffins, such as isobutane, with mono-olefins such as propylene, the butylenes, the amylenes, and mixtures thereof. The typical commercial alkylation processes of today usually involve the alkylation of isobutane with butylenes and/or propylene. These commercial processes typically produce a motor fuel alkylate having a research clear octane rating of about 93 to 95.

It is well recognized in the prior art that the components present in a typical motor fuel alkylate constitute a diverse mixture of both high octane and low octane C to C isomers. The prior art also recognizes that the only portion of the alkylate product having a low octane number which can be readily separated from the total alkylate product is the high boiling portion of the alkylate commonly referred to in the art as alkylate bottoms. In the typical alkylate produced by the catalytic alkylation of isobutane and isopentane with a typical olefin mixture of propylene, butylenes and amylenes, the alkylate has a 50 percent volumetric distillation temperature at atmospheric pressure of about 200 to about 240 F., and a 95 percent temperature of about 300 F. to about 350 F. and, not too uncommonly, often extends up to about 400 F. The exact initial boiling point varies by the amount of light ends, such as butane, present in the fuel and is determined by the particular use of the fuel and season of the year in which it is produced. The art recognizes that the very high boiling portion of the alkylate mentioned above is of a lower octane number than the rest of the alkylate produced, namely that portion of the alkylate boiling over about 270 to about 400 F. has a lower octane number than the rest of the total alkylate produced. Thus, Leffer, in U. S. Pat. No. 2,401,649 alkylates isobutane and butylenes in a conventional alkylation reaction zone to produce an alkylate gasoline rich in isooctane. This gasoline is obtained by separating from the alkylate product a fraction having an end boiling point of about 350 F. and an octane number of about 92. The higher boiling constituents present are removed and passed to a reforming zone for further conversion to lower boiling, higher octane constituents. Further, Hervert in U. S. Pat. No. 3,502,569, produces a high octane motor fuel by alkylating isobutane and a C mono-olefin to produce an alkylate separable into distinct low octane and high octane fractions and reforming the low octane fraction for blending with the higher octane number alkylate fraction. Deanesly, U. 8. Pat. No. 2,684,325 separates a polymerization-alkylation reactor effluent to recover a fraction boiling up to about 400 F. which is utilized as a gasoline blending component. The distillation residue boiling over 400 F. and representing about 10 percent by volume of the alkylation product, is recycled for upgrading to lowerboiling stocks. Findlay, U. S. Pat. No. 2,890,995, separates a light deolefinized gasoline fraction having an end boiling point (EBP) of about F. and an octane number of about 60.4 from a conventional HF isobutane alkylation unit, reforms this light fraction and blends the resulting refonnate with the higher boiling alkylate product to produce an upgraded gasoline. More particularly, Chapman in U. S. Pat. No. 3,211,803 separates a heavy alkylate produced in a conventional I-IF alkylation unit, and defined as having an initial boiling point (18?) of about 260 F. from the total alkylate produced in such unit and recycles this fraction to another alkylation unit for treatment with HF and isobutane to produce a higher octane number motor fuel.

Thus, it is seen that the prior art recognizes that a portion of either the light alkylate, and more particularly a portion of the heavier alkylate, as produced in typical commercial motor fuel alkylation processes, contain undesirable constituents which possess lower octane numbers than the rest of the motor fuel alkylate.

SUMMARY OF THE INVENTION As used herein, a substantially higher dimethylhexane content typically means that the dirnethylhexane content of the lower octane number fraction is at least twice the dimethylhexane content in the higher octane number fraction.

Accordingly, it is an object of this invention to provide a process of producing high octane number paraff'mic motor fuels. It is a further object of this invention to produce high octane number parafiinic motor fuels by a combination of alkylation, separation and disproportionation and/or transalkylation.

In a broad embodiment, this invention relates to a process for the production of a high octane number paraffinic motor fuel which comprises alkylating isobutane with a C mono-olefin by contacting the olefin and isobutane with an alkylation catalyst at alkylation conditions in an alkylation zone to produce an alkylate product containing dimethylhexanes. The thus produced alkylate is then separated into a low boiling, high octane motor fuel fraction and a high boiling, low octane fraction containing low octane hydrocarbons. This low octane fraction is further characterized by a dimethylhexane content substantially higher than the high octane fraction and has an initial boiling point of about 200 to about 230 F. This low octane, high boiling fraction is then contacted with an alkylation catalyst, preferably of the same type as used in the initial alkylation step, and isobutane at reaction conditions to produce a treated product wherein at least a portion of the low octane hydrocarbons are upgraded to a higher octane number, lower boiling hydrocarbon. Preferably, this treated product is passed to the initial alkylation zone and the upgraded hydrocarbons are thereafter recovered in admixture with the alkylate product and commingled with the low boiling high alkylate fractions to produce a high octane number paraffinic motor fuel. Further, the reaction conditions utilized in the treating step of the low octane high boiling alkylate fraction are correlated to induce a disproportionation and/or transalkylation reaction between the hydrocarbons present in the reaction.

In a further, more limited embodiment, the present invention relates to a process for the production of high octane number paraffinic motor fuel which comprises alkylating isobutane with C, mono-olefin by contacting olefin and isobutane with an HF alkylation catalyst at alkylation conditions in an alkylation zone comprising both an alkylation reaction zone and a settling zone so as to produce an alkylate product containing dimethylhexanes. This alkylate product is separated, in admixture with a hereinafter described recycle stream, into a low boiling, high octane motor fuel fraction and a high boiling, low octane fraction containing low octane hydrocarbons. This low octane fraction is characterized by a dimethylhexane content substantially higher than the high octane fraction and has an initial boiling point of about 200 to about 230 F. This low octane fraction is then contacted with an HF alkylation catalyst and isobutane at reaction conditions to produce a treated product wherein at least a portion of the low octane hydrocarbons are upgraded to a higher octane number and a lower boiling point. From this treatment step is recovered a recycle stream, hereinbefore mentioned, comprising HF catalyst, isobutane and upgraded hydrocarbons. This recycle stream is then passed to the previously described alkylation zone as indicated. Preferably, the recycle stream is not passed directly to the alkylation reaction zone but is passed to the settling zone for recovery of the treated hydrocarbons and HF catalyst.

Alternative embodiments and a more detailed description of the alkylation and treating zones mentioned, as well as the hydrocarbons utilized therein, Will be found in the following description of the preferred embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alkylation step of the process of the present invention for the production of a high octane number paraffinic motor fuel, preferably comprises alkylating isobutane and a butylene, inasmuch as the ideal alkylation product of these two reactants is a branched C paraffin. As utilized herein the term butylene refers to a C mono-olefin and thus includes l-butene, 2-butene and isobutylene which, when alkylated with isobutane, all produce a branched C parafl'in but which C paraffins, depending on the particular butylene reacting, have differing octane values. Further, it is within the scope of the present invention to include, in addition to isobutane and butylenes, a mixed hydrocarbon feedstock containing olefinic hydrocarbons such as propylene, amylenes, etc., as well as C to C parafiins including isopentane. If such mixed hydrocarbon streams are utilized, it is preferred that the C monoolefins (butylenes) and isobutane are the predominant species therein, to insure a more eflicient operation of the process of the present invention.

The alkylation step of the process of the present invention may comprise any alkylation process known to the art for alkylating isobutane and a C mono-olefin. Preferably, this alkylation between isobutane and the C mono-olefin is effected by contacting the olefin and isobutane with an alkylation catalyst maintained in alkylation zone at alkylation conditions so as to produce an alkylate product containing dimethylhexanes. The isobutane and butylene maybe introduced into the alkylation zone either as separate feedstrearns or in admixture with each other. Any alkylation catalyst known to the art of an acid-acting nature is suitable for use in the alkylation step of this invention. Thus, strong acid catalysts such as hydrofluoric acid, sulfuric acid, sulfuric acid and phosphoric acid mixtures, boron trifluoride promoted hydrofluoric acid, aluminum chloride-sulfuric acid complexes, HCL promoted aluminum chloride, boron trifluoride promoted phosphoric acid, aluminum chloride-hydrocarbon complexes, aluminum chloride-ether complexes, etc., are included. Preferred alkylation catalysts are liquid acids of a strong nature such as hydrofluoric acid and sulfuric acid, particularly hydrofluoric acid. Solid alkylation catalysts such as the highly acidic refractory inorganic oxides are also included within the scope of the present invention. When utilizing a strong liquid acid as a catalyst, the contacting between the olefin and isobutane reactants is preferably effected by intimately mixing the hydrocarbons with the catalyst in an alkylation reaction zone and thereafter separating the immiscible hydrocarbon products from the resultant alkylation zone effluent in a settling zone, thereby recovering the catalyst for recycle to the alkylation reaction zone.

To prevent polymerization of the olefin in the alkylation zone, the catalyst and hydrocarbons are maintained in intimate physical admixture with a large mole excess of isobutane to olefin being used. The isobutane to olefin mole ratio can vary from about 2:1 to about 20:1 and preferably from about 6:1 to about 16:1. The excess isobutane is readily separated from the alkylation product produced and is to be recycled to the alkylation zone. When a liquid acid such as hydrofluoric or sulfuric acid is utilized to catalyze the alkylation reaction, a catalyst to hydrocarbon volume ratio of about 0.25:1 to about :1, and more particularly about 0.5:] to about 5:1 is employed. The temperature at which the alkylation reaction is effected is often a function of the particular alkylation catalyst utiized and in general temperatures of about 0 to about 200 F. are utilized. However, when sulfuric acid is utilized as a catalyst in the alkylation step, temperatures in the range of about 40 are utilized and require refrigeration equipment, whereas if HF is utilized as a catalyst alkylation, temperatures in the neighborhood of 70 to 100 F. are sufficient. Residence times or contact times of about two seconds to about 1,200 seconds, and preferably from about 60 to 1,000 seconds, are suitable. The pressure maintained on the alkylation reaction can vary from about atmospheric to about 50 atmospheres; however, it is particularly preferred to maintain a reaction pressure sufficient to maintain both the catalyst and the hydrocarbon reactants in a liquid state at all times during the alkylation reaction period. After the termination of the desired residence time, the resultant alkylation effluent is separated into a hydrocarbon phase and an acid phase. From the hydrocarbon phase, unreacted isobutane and other light hydrocarbons such as propane and butane are recovered, often leaving a desired amount of butane within the alkylate to control the vapor pressure of the alkylate. Further, as used herein, the term alkylate refers to the desired high molecular weight reaction products from the alkylation reaction. The higher molecular weight tars, etc., formed within the reaction are also removed by appropriate, conventional distillation techniques. The resultant alkylate is then separated into a high octane, low boiling fraction, characterized in having an EBP of about 200 to about 230 F. and a lower octane, high boiling fraction, characterized in having an IBP of about 200 to about 230 F. Preferably, this boiling point is about 215 to about 220 F. This lower octane fraction is further characterized in that the dimethylhexanes formed by the isobutane-butylene alkylation reaction, are predominantly in this fraction; namely, the dimethylhexane content of this low octane fraction is at least twice that of the higher octane fraction. In a typical commercial HF catalyzed alkylation unit, this lower octane fraction typically consists of about 30 to 50 volume percent of the total alkylate product. The exact value is a function of the amount of propylene in the alkylation zone feedstock and the C isoparaffins produced as a result. This separation of the alkylate into respective high octane and low octane fractions is readily accomplished by conventional fractional distillation techniques well known to those trained in the art.

The high boiling, low octane fraction is contacted with an alkylation catalyst and isobutane at reaction conditions correlated to produce a treated product wherein at least a portion of the low octane hydrocarbons are upgraded to a higher octane number, lower boiling hydrocarbons. The reaction conditions to be utilized are those sufficient to induce a disproportionation reaction and, to a lesser extent, a transalkylation reaction to occur, thus upgrading the octane number of the fraction. No novelty is asserted as to the method of effecting this particular individual reaction and any method or system known to the art is applicable. Thus the A1C1 system of U. S. Pat. No. 2,404,934, the BE,- phosphoric acid system of U. S. Pat. No. 3,136,825 or the HF system of U. S. Pat. No. 3,211,803 are applicable.

in general, the alkylation catalysts applicable are the same as those capable of utilization in the hereinbefore described alkylation zone and, typically, it is often preferred to utilize the same catalyst in both steps of the process of the present invention.

The reaction conditions to be utilized to effect this desired conversion are broadly within the same range of conditions as utilized in an alkylation reaction utilizing the same catalyst. However, generally speaking, the preferred conditions for this conversion are generally more severe than the preferred conditions utilized in an alkylation reaction, i.e., an alkylation reaction will generally use lower temperatures and contact times. For example, when utilizing sulfuric acid in the alkylation reaction, the preferred temperature is about 35 to about 55 F., with a contact time of about 1 minute to about 10 minutes, whereas in the disproportionation reaction more severe conditions are required such as a temperature of about 40 to about 100 F. and a reaction time of about 2-20 minutes is preferred. Likewise, when utilizing HF as the catalyst, preferred alkylation temperatures are about to about F. with a reaction time of about 5 seconds to about 10 minutes, whereas in the disproportionation reaction a temperature of about 80 to about F. and a reaction time of about 5 seconds to about 15 minutes is preferred.

Whatever catalyst system is utilized, it is preferred to utilize a catalyst to hydrocarbon volume ratio of about 0.121 to about 10:1 and an isobutane to low octane fraction mole ratio of about 0.1:1 to about 10:1. By proper manipulation of these operating variables, at least 50 percent, and often at least 75 percent of the low octane alkylate fraction can be converted to lower boiling, high-octane paraffin hydrocarbons.

The thus produced upgraded hydrocarbon fraction may be readily recovered in the same manner as the product from an alkylation reaction and may be commingled directly with the high octane number alkylate fraction or it may be first separated with only the lowboiling, high octane constituents being admixed with the high octane alkylate fraction. In a particularly preferred embodiment, however, the upgraded alkylate fraction is separated, in admixture with the total alkylate product produced in the alkylation zone, and the upgraded hydrocarbons are then recovered directly commingled with the high octane alkylate fraction with the unconverted portion recovered in admixture with the low octane alkylate fraction.

A particularly preferred method of effecting the process of the present invention, involves the utilization of HF as both the alkylation and disproportionation reaction catalyst. The isobutane-butylene alkylation is performed in an alkylation zone comprising alkylation in an alkylation reaction zone and separation of the hydrocarbons from the HF in a settling zone. The alkylate produced is separated into a high octane fraction and a low octane fraction by fractional distillation, as previously described, and the low octane fraction upgraded, as indicated, by disproportionation with HF catalysis. Recovered from this disproportionation step is a recycle stream comprising HF, isobutane and upgraded hydrocarbons, which is passed to the alkylation zone and preferably to the settling zone contained in the alkylation zone. Thus the treated alkylate fraction and the alkylate product are separated together. This enables essentially lOO percent conversion of the high boiling, low octane alkylate constituents to lower boiling, higher octane products, thus producing a single high octane paraffinic motor fuel stream.

Further, by utilizing fresher HF catalyst in the disproportionation step and the used HF from the disproportionation step in the alkylation step, an efficient mode of effecting the overall process will be obtained.

ILLUSTRATTVE EMBODIMENT The following illustrative embodiment is presented to further illustrate the particular embodiments of the process of the present invention and is not intended to be an undue limitation on the broad scope and spirit of the appended claims.

An olefin mixture containing propylene, butylenes and amylenes, the majority of which are butylenes, was alkylated with isobutane in a conventional commercial HF alkylation system. This HF system was maintained at alkylation conditions including a 12:1 isobutane to olefin mole ratio, an operating temperature of about 85 F., a reaction residence time of about 420 seconds, a hydrogen fluoride to hydrocarbon volume ratio of about 1.521, and an operating pressure of about 175 psig. The alkylate produced, after separation of the excess isobutane, HF catalyst, and tars produced during the course of the reaction, had a 94.2 research clear tane number.

A sample of this motor fuel alkylate was then subjected to an intensive analysis including octane number evaluation and component analysis by dividing the sample into ten equal volume portions by fractional distillation, with each portion being analyzed to determine its composition and research octane number. The complete evaluation obtained is presented in the following table:

An examination of the data presented in the foregoing table, yields unexpected results. It is seen that the alkylate, in addition to the lower octane alkylate bottoms fraction, i.e., 260+ F. known to the art as having a lower octane number than the rest of the alkylate, there exists a sharp difference in the octane numbers attained for the first five 10% volumetric cuts than for the last five 10% cuts. This sharp, unexpected difference of about 10 octane numbers between these alkylate fractions appears to be the result of the presence of low octane number dimethylhexanes within each fraction. The presence of these compounds, despite the presence of appreciable amounts of high octane number trimethylpentanes, yields a marked octane number difference in comparison to the first five 10% volumetric cuts when these dimethylhexanes are not appreciably present. This difference is also observed in other alkylates produced within operating commercial units and laboratory units.

The foregoing alkylate is then fractionated to produce a high octane low boiling fraction which represents about percent of the total alkylate and has an IBP 216 F. boiling range. The remaining alkylate having an IBP of about 216 F. and having an octane number of about 86, is then contacted with hydrogen fluoride and isobutane in a disproportionation reaction zone. The isobutane is present at a mole ratio of isobutane to the low boiling fraction in a mole ratio of about 2:1 to about 5: l. The HF is present at an HF to hydrocarbon volume ratio about 0.5:1 to about 2:1. This isobutane, low octane alkylate and HF mixture is then intimately admixed for a reaction time of about 300 seconds and at a reaction temperature of about F.- After completion of the reaction time, the mixture is allowed to separate and the hydrocarbon phase removed therefrom and caustic washed to remove any entrained amounts of HF. After removal of any excess unconverted isobutane, this former low boiling alkylate fraction exhibited an initial boiling point 21 1392299515 @513? P522 number rating OCTANE NUMBER EVALUATION AND COMPONENT ANALYSIS OF ALKYLATE Fraction number 1 2 3 4 5 6 7 8 9 Botts 10 10 10 10 10 10 10 z 10 ll) 10 Alkylate component, weight percent Research octane number Type i-Butane n-B utane i-Pentane 5 u 2,3,-dimethylbutane 2-rnethylpentane 2,3-dimethylpentane 3-methylhexane 2,2,44rim ethylpentane. 2,5-dlmuthyll1cxane. 2,4-(llmethylhexnne.

Research clear octane number 10% fraction 1Cuttemp., F. 1 Volume, percent.

'nAn

9 greater than 90. This treated alkylate fraction when commingled with the low boiling, high octane fraction thus yields a high octane paraffinic motor fuel having an octane number rating higher than that presently obtair able in a single stage HF alkylation unit. 7 V W W 7 DESCRIPTION OF THE DRAWING those possessing expertise in the art of isoparaffm olefin alkylation being included in the generally broad scope of the present invention.

Referring now to the attached schematic diagram, a C mono-olefin feedstock containing lesser amounts of propylene and amylenes enters the process of this invention via line I and is commingled with isobutane entering via line 21 obtained from fresh make-up isobutane entering via line 20, and hereinafter described recycle isobutane stream 19. This isobutane and olefin are admixed in an isobutane to olefin mole ratio of about 12:1, and are passed to alkylation reactor 2 which is a conventional HF alkylation reactor. The hydrocarbon feedstock enters reactor 2 by a plurality of inlet lines indicated as lines la, 1b and to insure efficient temperature control within the HF alkylation unit. The HF catalyst necessary for the reaction enters reactor 2 by line 3 and is intimately admixed within the reactor, by means not shown, to insure a uniform reaction time of about 9 minutes and a uniform reaction temperature of about 85 F.

The effluent from HF alkylation reactor 2 is continuously removed via line 4 and comprises an emulsion of HF, isobutane and alkylate product which is passed via line 4 to mixer-settler 5. In addition, the reactor 2 effluent passing via line 4 is admixed with hereinafter described disproportionation reactor effluent entering via line 28 and passed to and separated in the common mixer-settler 5. Within mixer-settler 5 the alkylation reaction is allowed to go to completion and the hydrocarbon and HF components separated therein. The separated HF is withdrawn via line 6 with a portion thereof recycled to alkylation reactor 2 via line 3 and another portion thereof removed via line 7 and passed to hereinafter described disproportionation reactor 27. Further, a portion of the HF in line 7 may be continuously withdrawn by means not shown and passed to an HP acid regenerator to continuously upgrade the degraded alkylation catalyst.

The hydrocarbons separated in mixer-settler 5 are removed via line 9 and passed to fractionator l0. Fractionator 10 is a distillation column of conventional design wherein any butane produced in the alkylation reaction and/or passed to the reaction system in admixture with the isobutane feedstrearn, is removed via column 10 sidestream 11 and the alkylate product is removed as bottoms via line 22 and passed to distillation column 23. Removed as overhead from distillation column 10 via line 12 is an isobutane recycle fraction containing various amounts of entrained HF and propane. This overhead stream 12 is passed to condenser-receiver 13 wherein there is removed as bottoms therefrom, via line 15, isobutane for recycle, either to the alkylation step (via line 19) or the disproportionation step (via line 26) of the process of the present invention. A vaporous fraction is removed from receiver 13 'via line 14 and passed to depropanizer column 16 where any entrained propane, either as produced in the alkylation reaction or initially passed to the reaction in admixture with the isobutane feedstream, is removed overhead via line 17 and passed to HF stripper, not shown, to remove therefrom any entrained HF. Removed as bottoms from depropanizer 16 via line 18 are additional amounts of isobutane for recycle. Thus, isobutane for recycle is recovered via lines 15 and 18 and passed via line 19 to the alkylation reaction of the present invention, with a portion thereof removed via line 26 and passed to the r te sis-seabed sl srzrqizsrtiovat on tsas The alkylate product, removed from fractionator 10 via line 22 in admixture with the disproportionator product is passed to fractionator 23 and is separated into a low boiling, high octane fraction having an end boiling point of about 220F. which is removed overhead via line 24. A low octane, high boiling fraction is removed via line 25 and passed to disproportionation reaction 27 wherein this low octane alkylate bottoms is admixed with isobutane entering via line 26, HF catalyst entering via line 7 commingled with fresh HF catalyst entering via line 8. The resulting mixture is maintained at disproportionation reaction conditions, within reaction zone 27, including an isobutane to alkylate bottoms mole ratio of about 5:1, an HF to hydrocarbon mole ratio of about 1:1, a reaction temperature of about 100F and a reaction time of about 300 seconds. After the completion of the desired reaction time in disproportionation reaction zone 27, the product therefrom is removed via line 28 and which comprises isobutane, treated alkylate fraction and HF. This product is passed via line 28 and commingled with alkylation zone 2 effluent, flowing in line 4 and passed to mixer-settler 5 as previously described. By utilizing this flow arrangement each reaction zone, specifically alkylation reaction zone 2 and disproportionation zone 27, utilizes the same common recovery train for a more efficient utilization of not only the reactants, but also insures almost 100 percent conversion of any high boiling, low octane alkylate produced in alkylation zone 2 to be converted to lower boiling, higher octane constituents so as to produce a single alkylate product stream 24 suitable as a high octane paraffinic motor fuel. However, conversions of about are more typical. v

I claim as my invention:

1. A process for the production of a high octane number paraflinic motor fuel which comprises the steps of: W

a. alkylating isobutane with a C mono-olefin by contacting the olefin and isobutane with an alkylation catalyst at alkylation conditions in an alkylation zone to produce an alkylate product containing dimethylhexanes;

separating said alkylate into a low boiling, high octane motor fuel fraction and a high boiling, low octane fraction containing low octane hydrocarbons, said low octane fraction characterized by a dimethylhexane content substantially higher than said high octane fraction and having an initial boiling point of about 200 to about 230 F.; and,

c. contacting at least a portion of said low octane fraction with an alkylation catalyst and isobutane at disproportionation reaction conditions to produce a treated product wherein at least a portion of the low octane hydrocarbons are upgraded to higher octane number hydrocarbons having a lower boiling point.

2. The process of claim 1 wherein said low octane, high boiling fraction comprises about 30 to about 60 volume percent of said alkylate product.

3. The process of claim 1 wherein said alkylation catalyst of step (a) and (c) is sulfuric acid, said reaction conditions of step (c) comprise a temperature of about 40 to about 100 F., a contact time of about 60 seconds to about 600 seconds, a catalyst to hydrocarbon volume ratio of about 0.1:1 to about 10:1 and an isobutane to low octane fraction mole ratio of about 0.1:1 to about 10:1.

4. The process of claim 1 wherein said alkylation catalyst of step (a) and (c) is hydrogen fluoride, said reaction conditions of step (c) comprise a temperature of about 80 to about 100F., a contact time of about 5 seconds to about 900 seconds, a catalyst to hydrocarbon volume ratio of about 0.121 to about :1 and an isobutane to low octane fraction mole ratio of about 0.1:1 to about 10:1.

5. The process of claim 1 wherein the treated product of step (c) is separated, in admixture with the alkylate product of step (a) and the upgraded hydrocarbons are recovered with the low boiling, high octane alkylate fraction.

6. The process of claim 1 wherein the treated product of step (c) is separated to recover the upgraded high octane number hydrocarbons for blending with the high octane number, low boiling fraction of tion catalyst at alkylation conditions in an alkylation zone comprising an alkylation reaction zone and a settling zone to produce an alkylate product containing dimethylhexanes.

b. separating said alkylate and a hereinafter described recycle stream into a low boiling, high octane motor fuel fraction and a high boiling, low octane fraction containing low octane hydrocarbons, said low octane fraction characterized by a dimethylhexane content substantially higher than said high octane fraction and having an initial boiling point of about 200 to about 230 F;

.contacting at least a portion of said low octane fraction with an HF alkylation catalyst and isobutane at disproportionation reaction conditions to produce a reaction product wherein at least a portion of the low octane hydrocarbons are upgraded to higher octane number hydrocarbons having lower bqilin point' d. recovering rom step (c) a reaction stream comprising HF, isobutane and said higher octane number hydrocarbons; and,

(e) passing said reaction stream to the settling zone of step (a).

10. The process of claim 9 wherein said alkylation conditions comprise a temperature of about 0 to about 200 F., a contact time of about 2 seconds to about 1,200 seconds, a catalyst to hydrocarbon volume ratio of about 0.5 :1 to about 5:1, an isobutane to an olefin mole ratio of about 2:1 to about 20:1 and a pressure of about atmospheric to about 50 atmospheres.

11. The process of claim 9 wherein said conditions of step (c) comprise a temperature of about to about F., a contact time of about 5 seconds to about 900 seconds, a catalyst to hydrocarbon volume ratio of about 0.1:1 to about 10:1, an isobutane to high boiling fraction mole ratio of about 0.1:1 to about 10:1 and a pressure of about atmospheric to about 50 atmospheres.

12. The process of claim 9 further characterized in that said low octane, high boiling fraction comprises about 30 to about 60 volume per cent of said alkylate product.

13. The process of claim 9 wherein said low octane fraction has a boiling point of about 215 to about 220 F.

Claims

2. The process of claim 1 wherein said low octane, high boiling fraction comprises about 30 to about 60 volume percent of said alkylate product.
3. The process of claim 1 wherein said alkylation catalyst of step (a) and (c) is sulfuric acid, said reaction conditions of step (c) comprise a temperature of about 40* to about 100* F., a contact time of about 60 seconds to about 600 seconds, a catalyst to hydrocarbon volume ratio of about 0.1:1 to about 10:1 and an isobutane to low octane fraction mole ratio of about 0.1:1 to about 10:1.
4. The process of claim 1 wherein said alkylation catalyst of step (a) and (c) is hydrogen fluoride, said reaction conditions of step (c) comprise a temperature of about 80* to about 100*F., a contact time of about 5 seconds to about 900 seconds, a catalyst to hydrocarbon volume ratio of about 0.1:1 to about 10:1 and an isobutane to low octane fraction mole ratio of about 0.1:1 to about 10:1.
5. The process of claim 1 wherein the treated product of step (c) is separated, in admixture with the alkylate product of step (a) and the upgraded hydrocarbons are recovered with the low boiling, high octane alkylate fraction.
6. The process of claim 1 wherein the treated product of step (c) is separated to recover the upgraded high octane number hydrocarbons for blending with the high octane number, low boiling fraction of step (b).
7. The process of claim 1 wherein the treated product of step (c) is commingled with the low boiling, high octane fraction of step (b).
8. The process of claim 1 wherein said low octane fraction has a boiling point of about 215* to about 220* F.
9. A process for the production of high octane number paraffinic motor fuel which comprises the steps of: a. alkylating isobutane with a C4 mono-olefin by contacting the olefin and isobutane with an HF alkylation catalyst at alkylation conditions in an alkylation zone comprising an alkylation reaction zone and a settling zone to produce an alkylate product containing dimethylhexanes. b. separating said alkylate and a hereinafter described recycle stream into a low boiling, high octane motor fuel fraction and a high boiling, low octane fraction containing low octane hydrocarbons, said low octane fraction characterized by a dimethylhexane content substantially higher than said high octane fraction and having an initial boiling point of about 200* to about 230* F; c. contacting at least a portion of said low octane fraction with an HF alkylation catalyst and isobutane at disproportionation reaction conditions to produce a reaction product wherein at least a portion of the low octane hydrocarbons are upgraded to higher octane number hydrocarbons having lower boiling point; d. recovering from step (c) a reaction stream comprising HF, isobutane and said higher octane number hydrocarbons; and, (e) passing said reaction stream to the settling zone of step (a).
10. The process of claim 9 wherein said alkylation conditions comprise a temperature of about 0* to about 200* F., a contact time of about 2 seconds to about 1,200 seconds, a catalyst to hydrocarbon volume ratio of about 0.5:1 to about 5:1, an isobutane to an olefin mole ratio of about 2:1 to about 20:1 and a pressure of about atmospheric to about 50 atmospheres.
11. The process of claim 9 wherein said conditions of step (c) comprise a temperature of about 80* to about 150* F., a contact time of about 5 seconds to about 900 seconds, a catalyst to hydrocarbon volume ratio of about 0.1:1 to about 10:1, an isobutane to high boiling fraction mole ratio of about 0.1:1 to about 10:1 and a pressure of about atmospheric to about 50 atmospheres.
12. The process of claim 9 further characterized in that said low octane, high boiling fraction comprises about 30 to about 60 volume per cent of said alkylate product.
13. The process of claim 9 wherein said low octane fraction has a boiling point of about 215* to about 220* F.