US2978524A - Paraffin alkylation process promoted with silica gel and aluminum bromide - Google Patents

Description

W 1961 G. R. GILBERT ETAL 2,978,524

PARAF'FIN ALKYLATION PROCESS PROMOTED WITH SILICA GEL AND ALUMINUM BROMIDE Filed Dec. 1, 1958 2 82 or- 042 Z 0:0: 0 mac .1; N N S 1 N m :12 5 3 o N m N F! I 5 r 5% N O O 10 m E %w :12 m i (59 2 mg do o um: 3 mm H: 5 um: 42 34: 9 J r mo 0: IE 0 a :1:

George R. Gilbe n Alon Schneshenn Inventors John E. McCormick By Q M Attorney PARAFFIN ALKYLATION PROCESS PROMOTED WITH SILICA GEL AND ALUNHNUM BROMIDE George R. Gilbert, Elizabeth, Alan Schriesheim, Fords, and John E. McCormick, Roselle Park, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Dec. 1, 1958, Ser. No. 777,282

9 Claims. (Cl. 260-68353) This invention relates to a process wherein butanes and/or pentanes are alkylated with higher paraflin hydrocarbons to produce branched chain parafiin hydrocarbons boiling in the motor fuel range. In particular the invention concerns a process wherein a butane or a pentane is reacted with a parafiin hydrocarbon of from 6 to 18 carbon atoms in the presence of aluminum bromide and a promoter under conditions that favor the production of high yields of branched chain paraffin hydrocarbons of from to 7 carbon atoms.

With the increased use of modern high compression engines in the automotive industry the petroleum refiners have encountered a major problem in supplying a sufficient quantity of motor fuels of high octane rating to satisfy the requirements of those engines. Heretofore the supply of gasoline components has been augmented by using C and C petroleum fractions as starting ma:

Patented Apr. 4, .1961

2 able source. A portion of the stream is conducted via line 11a through an aluminum bromide pick-up vessel 12 to dissolve aluminum bromide in a portion of the stream that is conducted to the reaction zone. The remainder of the feed stream is combined with the effluent leaving the pick-up vessel via line 13 and is conducted into a reaction zone 15. The latter zone contains one or more beds of silica gel saturated with aluminum bromide.

A stream of a higher paratfin hydrocarbon, as for. ex-

ample heptane, octane, dodecane or cetane, or of mix tures containing the higher paraflins, is conducted into the reaction zone by means of line 16. Preferably the stream enters the reaction zone at a plurality of spaced points, 16a, 16b, etc., so as to insure as high a ratio as possible of isobutane to higher paraflin at any particular point in the reaction zone. a

The reaction product leaves the reaction zone through line 18 and is conducted into an initial separation zone terials for making higher hydrocarbons principally by if polymerization and alkylation processes. Thus for example isobutane can be reacted with butylene in the presence of sulfuric acid to give a branched chain 8- carbon-atom alkylate. Also butylene can be polymerized to a C unsaturated hydrocarbon which upon hydrogenation will give isooctane. These processes have some disadvantages in that they require a number of separate operations and in that they necessitate the use of olefins which are usually in relatively limited supply.

It has now been found that, by the use of a promoted aluminum bromide catalyst, butanes and/or pentanes can be reacted directly with higher paratfin hydrocarbons to give good yields of C to C branched chain hydrocarbons of high octane rating, provided certain specific conditions are employed. to conduct reactions'of this type but yields have been low, reaction rates have been uneconomic and satisfactory product distribution has not been obtained.

In accordance with the present invention, a paraffin It has previously been proposed 1 hydrocarbon-of from 6 to 18 carbon atoms is reacted with a large excess of a butane or a pentane, preferably isobutane, employing as a catalyst A1Br supported on or associated with silica gel, at temperatures in the range of schematic flowlplan of one ,process for practicing. the invention.

The process will be described with'particular reference tothe use of isobutane as the lighter component. Referring to the drawing in detail, a suitable butane feed stream containing at least initially a major proportion of isobutane is obtained by means of line 11 from. a-suiti 20 wherein light materials including unreacted isobutane and normal butane, are removed overhead and recycled to the reaction zone by means of line 21. Hydro,- gen bromide, which is preferably present, will also be recycled via line 21. The heavier material, including C hydrocarbons and higher, is conducted by means of line 22 into a product separation zone 24 wherein C to C hydrocarbons are removed overhead by means of line 25 while heavier material comprising C hydrocarbons and higher as well as any aluminum bromide that has been removed from the reaction zone is recycled to the reaction zone by means of line 26. If desired, conditions can be adjusted in separation zone 24. to include normal heptane in the heavier material recycled through line 26, while including the C branched chain isomers in overhead line 25.

In place of isobutane the feed in line 11 may comprise normal butane, in which case no higher hydrocarbon feed stock will be sent initially to the reaction zone but 7 able cracking occurs and the principal products'are pro- 7 pane and lighter materials. Also it has been established that aluminum bromide alone or even in'the presence of conventional hydrogen halide promoters such as hydrogen bromide, in the absence of the support, is very.

much less active than the catalyst system of the present invention. Furthermore in order for the reaction to proceed satisfactorily it is necessary that suflicient alumi 1 if num bromide be present not only to saturate the support I under the reaction conditions employed but also to leave at least a small amount dissolved in the reacting hydrocarbons.

A mixed catalyst in which a portion of the aluminum bromide is replaced with aluminum chloride may be used provided that at least some aluminum bromideis present in the reacting hydrocarbons over and above that which is adsorbed on the support.

Although the reaction may proceed in the absence of hydrogen bromide promoter it is preferred that it be used as an auxiliary promoter in addition to the silica gel A range of from about 0.1 to 8% or more of HBr by weight based on total feed may be used, while from about 2% to about 5% is preferred. The hydrogen bromide is introduced into the reaction zone by means of line. 17 and is recycled to the reaction zone along with unreacted butanes by means of line 21.

Although the process as described in conjunction with the drawing contemplates downflow of the stream through the catalyst bed, which is preferred, upflow can also be used. Also in place of a fixed bed process, a moving bed of catalyst could be used. Alternatively, a slurry type of operation could be employed wherein a suspension of catalyst is maintained in the reacting hydrocarbons, the slurry being stirred in the reactor with suitable mechanical stirring means or recirculated through the reactor by pumping means. Where slurry operation is used, the slurry is removed from the reactor at the end of the reaction period, in the case oi batch operation, or as a fraction of the circulating stream in the case of; continuous operation, and sent to suitable separation equipment to separate the catalyst from the hydrocarbons. The separation equipment may comprise a simple settling tank, a centrifuge, or a filter, for example, or suitable combinations of such means.

It is preferred that the minimum mol ratio of isobutane and/or isopentane to higher parainn be about 3 to 1 but should preferably be no higher than about 12 to 1. If sufficient iso-C is not present in the reaction zone to efiect alkylation of the materials obtained when a higher parafiin or other higher product of the reaction is cracked by the catalyst, catalyst sludging will result. The feed stock must be essentially free of aromatic hydrocarbons and not more than about 0.02% of such material should be present. An added advantage of the catalysts of the present invention is that naphthene hydrocarbons may be tolerated in the feed stock up to about 20 volume percent. With increased naphthene content the reaction severity must be increased somewhat as compared to a reaction in the absence of naphthenes. This may be accomplished by raising the temperature and/or lowering the feed rate, for example.

Feed rates may vary from about 0.3 to about 2 v./hr./v. (liquid volume of total feed per hour per volume of total catalyst plus support) the higher feed rates being preferred when little or no naph-thenes are present.

To remove aromatics from the feed stock conventional techniques may be employed such as solvent extraction, hydrogenation, acid treating and the like, as well as treatment with selective absorbents such as molecular sieve zeolites. It is not necessary that the higher hydrocarbons used be individual hydrocarbons such as heptane or octane or cetane, for example, but mixtures may be used, such as a petroleum fraction containing paraifinic hydrocarbons in the range of 6 to 18 carbon atoms. Although, as stated, hexane is one of the higher hydrocarbons that may be used, it is preferred to employ heptane or higher. Essentially the same product distribution is obtained with hexane as with heptane but the reaction rate is lower by a factor of about 3. Other sources of the higher parafiin hydrocarbons for the reaction include light virgin naphthas, and paraffin raflinates from the extraction of hydroformed petroleum fractions.

At the start of the process the silica gel may be saturated with aluminum bromide and then placed in the reaction zone, or, alternatively, the silica gel alone may be placed in the reaction zone and then saturated with aluminum bromide carried in with a portion of the feed. Another method of preparation is to mix the aluminum halide with the support and to heat the mixture to effect impregnation. If desired, loosely held aluminum halide may be removed from the catalyst mass by heating the mass and passing through it a gas such as carbon di oxide, methane, hydrogen or nitrogen.

Alternatively the support may be impregnated by dissolving the aluminum halide in a suitable solvent such as ethylene dichloride or dioxane, for example, and the porous carrier impregnated with this solution, followed by heating to remove the solvent and loosely held aluminum halide. Still another alternative is to employ a powdered support or promoter, mix the aluminum halide with it, and compress the mixture into pellets.

The following examples serve to illustrate the practice of the present invention.

Example 1 Comparative tests were made in which in each instance a mixture of 160 cc. of isobutane and 40 cc. of a normal heptane feed (containing n-C and 5% of methylcyclohexane) was stirred for 3 hours at 72 F. with one of the catalyst systems identified in Table I. At the end of each run the yield of products was determined. the results also being presented in Table I.

Table 1 Test 1 Test 2 Test 3 Test 4 Catalyst, grams:

AlBr; 23. 6 23. 6 23. G 23. t Silica gel 47. 2 47. 2 HBr 24. 0 .l. 1

Analysis of (Id-Product, Weight percent:

iso-Os 0. 4 0. 5 12.3 31!. 0 n-Cs 0.3 3. 6 1.0 3.7

0. 5 0. 3 14. 9 l) 7 0 0 U. 6 l l 46. 2 48. 3 (i5. 6 38. (l 52. 6 47. 3 l l. t

Total C7 Q8. 8 95 6 68. 7 39. .5

C's-l- I. 0 l 2 It will be seen from the results of these comparative tests that aluminum bromide alone, or even in the presence of hydrogen bromide, was not eifective in producing the desired reaction. In both of these instances the major proportion of the reaction products comprised C hydrocarbons. The aluminum bromide merely served as an isomerization catalyst. On the other hand, in the tests in which aluminum bromide and silica gel either alone or in conjunction with hydrogen bromide were employed as the catalyst, considerable yields of C and Cs isomers were obtained. Since the total weight of the reacting hydrocarbons was about 118 grams, the 2.4 grams of HBr in Test 4 equalled about 2 weight percent, based on total feed. It will be seen that the catalyst activity was greatly enhanced by that amount of hydrogen bromide.

EXAMPLE 2 In a manner similar to that employed in Example 1 comparative tests were made with a number of other supports instead of silica gel. These included pumice, sand, powdered quartz and Fe O The same catalystto-support ratios were used, as well as the same reaction temperature and time, and the same hydrocarbon feed as in Example 1. None of the supports other than silica gel was found to be efiective in promoting the desired reaction. In each case from about 96.5 to about 99% of the product comprised C hydrocarbons althrough some isomerization of the normal heptane had taken place.

E AM L 3 Two forms of silica gel were compared for their activity in promoting aluminum bromide in the reaction of isobutane and. normal heptane. One of these was a granular silica gel and the other was a spray dried silica gel. The physical properties of these two forms of silieage a e com ar d in Tab e .II-

Table I] Table IV Surface Pore Pore RunA RunB Area, Vol. Radius, mJ/g. cc./g. A. r

5 Wt. Percent AlBr in Feed.. 0. 2 0.06 704 21 151 riluolilggrswgurzgfii o-50 50-80 80-100 20-70 145-185 1i eii s? "di iIzoe 63 C5 -1 -1. so a0 6 36 r1 i2 i8 s3 12 it Using the same hydrocarbon-feed and the same reaction conditions as in Example 1 the two forms of EXAMPLE 5 silica gel were compared using equal weights of silica H gel and aluminum bromide. The results obtained at .Usmg the same P110t eq EX P 4 the end of a 3 hour reaction period are shown in Table l fs a catalyst mllfitllfe conslfitmg 0 equal III. It will be seen that the'spray dried silica gel was Q of gel and alumlnum m i Pulls were a more active promoter 'for the desired reaction than 15 made In Whlch the amount o Y P b o added the granular sill-ca geL to the feed and the amount o f a1um1num bromide added 7 were vaned. Reactron conditions were the same as in Table III Example 4. -When employing 2 percent hydrogen bromide and 1 percent aluminum bromide it was found that Granular spray the catalyst activity remained relatively constant; With Silica Dried 2 percent aluminum bromide and 2 percent hydrogen Gel ag bromide the catalyst activity remained relatively constant and at a' somewhat higher level than with 1 percatalystz cent aluminum bromide (roughly 20 percent more AiB grams 47-2 47-2 active). When only 1 percent hydrogen bromide was f 3352 5 -w y g z g employed along with 2 percent aluminum bromide the catalyst activity dropped to $4; of its original value in 5969' 2:? i; about 60 hours.

d Other studies have established that in order to obtain the desired reaction it is necessary to have present in 0 '0 the reaction zone sufficient aluminum bromide so that 08 aluminum bromide will be present in solution in. the hydrocarbons over and above the quantity required to i504}, 58.9 40.1 satisfy the total adsorption capacity of the silica gel. -01 i To ensure such a condition incontinuous operation it Totalc, 6M 4L5 is preferred that sufiicient aluminum bromide be dissolved in at least one of the entering streams of reacting hydrocarbons so that a minimum of 0.1 weight percent of aluminum bromidebased on feed is sent to'the EXAMPLE 4 40 reaction zone. As brought out in Example 5 it is also A catalyst composition comprising silica gel and alugig g gi g igg gj i g rgf g 55322 5 3X gggg g gig fi ig g g yg g g g g ggg ii gg tain catalyst activity in continuous operation. Preferpilot unit consisting of a jacketed reactor provided with i g 2 to 5 weight percent of hydrogen bromlde 23 5 2 33 lfgg gg ggg g gifi gif sg 6%: Although in the illustrative examples given, the higher P and 150 p g pressure- A feed mixture of normal para ifin hydrocarbon reactant comprised heptane, other hptane and which gave about 70 volume studies have shown that with hydrocarbons of greater 7 percent of isobutane in the reactor was passed through molecular Sue-h as. Octaneicetane or octadecape the reactor at a space velocity of about 0.05 volume of gg ggg distnbunon ls essentially the Same as wlth trier 5:51:32?atzziztezaifla narrate :33: ore Wl occur 0 1 r u :rithateagerness? 20232? 242a; g g ously added to the reaction zone as a solution inisobug g p f 1 i L d 5 tane in sufiicient quantity to furnish a 2 wt. percent rocar 15 afger m Proporlon o y focal.- solution based on total feed. Hydrogen bromide was bons than is desired. the Product may be i to added at the rate of 2 wt. percent based on the feed. i a F whlch P than be used a The total liquid product from the reactor was scrubbed tlonal aliylatlon step with an .olefin such as ethylepe with 20% caustic to remove aluminum bromide and propylene or a butfineaempioymg the u sual hydrogen bromide, then dried, debutanized and analyzed. catalysts as Sulfur: aFId! acid y After 50 hours of operation the addition of aluminum gen fiuonde, or an alummum Alternatlvelyw bromide to the feed was discontinued. At the end of the 5 can befall 0 8 Second reaction zone of the an additional 50 hours of operation the activity f the type herein described for reaction with higher normal catalyst for the desired reaction was less than 10% of P hydrocarbonsits initial activity as shown in Table It lS tO be understood that this invention is not to A Second run was made in the pilot i using a be l mited to the specific embodiments and examples catalyst composition comprising equal weights of silica herein desfmbed and Presented P that Its scope 15 to gel and aluminum bromide and continuously adding alube deteTI n1ned b y the clalms pp heretominum bromide in sufficient quantity to furnish 0.2 wt. What IS clalmed percent based on total feed for the first 50 hours and A Process for the Preparation of high Octane subsequently to furnish 0.06 wt. percent based on feed. naphtha components consisting largely of branched chain The product was treated and analyzed in the same paraffin hydrocarbons of 5 to 7 carbon atoms which manner as in the first run and the results obtained are comprises reacting a minor proportion of a straight chain also shown in Table IV. paraffin hydrocarbon of from 6 to 18 carbon atoms with a major proportion of a lighter hydrocarbon selected from the group consisting of butanes and pentanes, at temperatures no higher than about 140 F., in a reaction zone in the presence of a catalyst comprising aluminum bromide and silica gel and maintaining in the reaction zone at least 0.06 weight percent aluminum bromide in solution in the reacting hydrocarbons in addition to the quantity required to satisfy the total adsorption capacity of the silica gel.

2. Process as defined by claim 1 wherein from about 0.1 to about 8 percent of hydrogen bromide, based on the reacting hydrocarbons, is present in the reaction zone.

3. Process as defined by claim 1 wherein the mol, ratio of said lighter hydrocarbon selected from the group consisting of butanes and pentanes to said hydrocarbon of from 6 to 18 carbon atoms in the reaction zone is in the range of from about 3 to 1 to about 12 to l.

4. Process as defined by claim 1 wherein naphthenic hydrocarbons are present in said reaction zone.

5. Process as defined by claim 1 wherein the temperature of the reaction is in the range of about 50 to about 120 F.

6. Process as defined by claim 1 wherein said silica gel is in the form of spray dried microspheres.

7. A process for the preparation of high octane naphtha components consisting largely of branched chain paraflin hydrocarbons of from 5 to 7 carbon atoms which comprises reacting a minor proportion of a straight chain paraflin hydrocarbon of from 6 to 18 carbon atoms with a major proportion of a lighter hydrocarbon selected from the class consisting of butanes and pentanes, at temperatures no higher than about 140 F., in the presence of a catalyst comprising silica gel saturated with aluminum bromide, continuously conducting reacting hydrocarbons into said reaction zone at a rate such that the mol ratio of said lighter hydrocarbon selected from the group consisting of butanes and pentanes to said hydrocarbon of from 6 to 18. carbon atoms in the reaction zone is in the range of from about 3 to 1 to about 12 to 1, continuously adding to at least one of the entering streams of reacting hydrocarbons at least 0.1 weight percent of aluminum bromide based on the total hydrocarbon feed, and continuously removing reaction products from said reaction zone.

8. Process as defined by claim 7 wherein from 2 to 5 weight percent of hydrogen bromide, based on total hydrocarbon feed is added to at least one of said entering streams of reacting hydrocarbons.

9. A process for the preparation of high octanenaphtha components consisting largely of branched chain parafiin hydrocarbons of from 5 to 7 carbon atoms which comprises reacting a minor proportion of a straight chain paratfin hydrocarbon of from 6 to 18 carbon atoms with a major proportion of a lighter hydrocarbon selected from the group consisting of butanes and pentanes, at temperatures no higher than about F., in the presence of a catalyst comprising silica gel saturated with aluminum bromide, continuously conducting said reacting hydrocarbons into said reaction zone, continuously adding at least 0.06 weight percent aluminum bromide based on reacting hydrocarbons to said reaction zone, and continuously removing reaction products from said reaction zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,349,458 Owen et a1. May 23, 1944 2,370,144 Burk Feb. 27, 1945 2,401,925 Gorin June 11, 1946

Claims (1)

1. A PROCESS FOR THE PREPARATION OF HIGH OCTANE NAPHTHA COMPONENTS CONSISTING LARGELY OF BRANCHED CHAIN PARAFFIN HYDROCARBONS OF 5 TO 7 CARBON ATOMS WHICH COMPRISES REACTING A MINOR PROPORTION OF A STRAIGHT CHAIN PARAFFIN HYDROCARBON OF FROM 6 TO 18 CARBON ATOMS WITH A MAJOR PROPORTION OF A LIGHTER HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BUTANES AND PENTANES, AT TEMPERATURES NO HIGHER THAN ABOUT 140*F., IN A REACTION ZONE IN THE PRESENCE OF A CATALYST COMPRISING ALUMINUM BROMIDE AND SILICA GEL AND MAINTAINING IN THE REACTION ZONE AT LEAST 0.06 WEIGHT PERCENT ALUMINUM BROMIDE IN SOLUTION IN THE REACTING HYDROCARBONS IN ADDITION TO THE QUANTITY REQUIRED TO SATISFY THE TOTAL ADSORPTION CAPACITY OF THE SILICA GEL.

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