US2987561A - Method for producing isoparaffins - Google Patents

Description

June 6, 1961 ISOPARAFFINS NAPHTHA L. SPENADEL 2,987,561 METHOD FOR PRODUCING ISOPARAFFINS Filed March 4. 1959 0 ISO- 4 Al RECOVERY ZONE LIGHTER PRODUCT 0; PRODUCT |4- PRODUCT} EFFLUENT [REACTOR IO CATALYST Lawrence Spenudel Inventor United States Patent 2,987,561 METHOD FOR PRODUCING ISOPARAFFINS Lawrence Spenadel, Elizabeth, NJ., assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Mar. 4, 1959, Ser. No. 797,145 1 Claim. (Cl. 260-68353) The present invention is concerned with an improved method of upgrading paraflins to isoparaflins. More particularly, it deals with converting paraflins to isoparaifins to give good yields of desired products in the presence of substantial portions of aromatics.

The desire for obtaining high octane fuels has constantly increased with the development of engines of higher compression ratios. Thus the lowest grade gasolines of the present have a higher octane than the premium fuel of only a few short years ago. Among the ways advanced for securing requisite high octane constituents have been conversion processes designed to convert parafiin hydrocarbon, e.g. normal C to C fractions, into isoparaflinic and branched chain molecules. It is well known that isoparaffins have substantially better octane characteristics than their normal parafiin counterparts. Additionally, the art recognizes that aromatics, such as benzene and toluene, also exhibit good octane qualities.

Among the processes heretofore advanced for the conversion of parafins into more desirable isoparafiins is paraflin alkylation, sometimes termed parafiin disproportionation. Basically, this process involves contacting a normal paraflin hydrocarbon, preferably of from 6 to 18 carbon atoms, with an excess of isobutane and/or isopentane in the presenceof a Friedel-Crafts' catalyst, e.g. aluminum bromide. Among the products of the reaction will be a substantial portion of isoparafiin mole cules having a number of carbon atoms intermediate to that of the normal paraflin and isobutane and/or isopentane feed. For example, reaction of normal heptane with isobutane will give isopentane'and isohexane. H

Normally, one of the most readily available feed materials for parafiin alkylation is a naphtha hydrocarbon fraction obtained by primary crude distillation of the parafiins left after removal of the aromatics from cata1ytically reformed or cracked naphtha. However, in addition to containing paraflins suitable for reaction, naphthas also contain substantial quantities, e.g. 1.0 to 40%, of aromatics. The aromatics are mostly benzene, toluene and xylene. In addition to naphthas, other feedssuch as kerosenes and higher boiling hydrocarbons also con tain aromatics.

Patented June 6, 1961 In accordance with the present invention, high concentrations of aromatics are readily tolerated in the reaction zone while obtaining exceedingly good yields of highly valued branched chain parafiins, such as isopentanes and isohexanes. More particularly, parafiin hydrocarbons are converted in the presence of a catalyst of aluminum chloride on a support containing iron chloride, silica and alumina.. It has been found that aluminum chloride on this specific support shows exceptionally good catalytic properties in the presence of aromatics. In addition to the advantages indicated previously, by allowing reactionto take place in the presence of aromatics, the product stream will be a particularly good high octane material since aromatics as well as'isoparaflins exhibit good octane properties. As will be shown later by way of experimental examples, the catalyst of the present invention is substantially superior to aluminum chloride alone or on alumina alone; aluminum chloride on'silica-alumina alone; or simply ferric chloride on a base of silica-alumina. It is generally well known that FeCl alone gives negligible activity in the presence of aromatics. r

The paraflin-alkylation' reaction may be conducted in the liquid or vapor state. Reaction temperatures of 200 to 300 F. are preferred. AlCl," rather than AlBr is employed since it is less acidic and has less tendency to react with thebasic aromatic constituents.

In order to clarify nomenclature, the term parafiin feedstream denotes the overall mixture. of hydrocarbons (paraflins, isoparaflins and aromatic constituents) fed to the reaction'zone regardlesswi whether the individual components be individually introduced or fed as a single Heretofore it had been found to be necessary to reduce the aromatic concentration in the feed stream to no more than 0.1 wt. percent -It was found that higher- "stituents areprimarily- .benzene and toluene. A relaconcentrations of aromatics tended to destroy the catalytic" sludge and polymers. Thus conventional paraifin alkyl ation systems could notfbe operated to give desirable; yields of aflched chain Products in the P G 0f ployed, i.e. 1.1 to 10 moles per mole of normal heptane 'x in the feed.

ation system capable of giving good yields of desiredill stream. ,1. n--." nw The various aspects and modifications of the present invention will-be madev more clearly apparent by reference to the following description, specific embodiment and accompanying drawing.

Turning to the drawing, reactor 10 may be any one of a number of well known iparafiini alkylation zones containing the catalyst of the present invention, i.e. aluminum chloride on a support of iron chloride, silica and alumina. It may operate in the liquid or vapor phase and under a wide range of pressures. The catalyst may be in the form of a fluid or moving fixed bed, fixed bed, liquid or gaseous suspension, etc. Numerous means for promoting good contact between reactant and catalyst, e.g. distribution gn'ds, bafiles, etc., may be employed. In the specific embodiment presently described, reactor 10 serves principally to convert the normal heptane constituents of a naphtha fraction boiling in the range of 200 to'22l) F. The naphtha contains about 15 wt. perlively low molecular weight isoparaflin (as compared to jfthenormal parafiin feed materials) is fed through line 11. In the present'einbodiment, the isoparaflin is isobu- 'tane. Generally; aw-molar excess of isobutane is em- Reactor 10 is maintained at 200 F. and a pressure of 500 p.s.i.g.,reaction' taking place in the liquid phase. The catalyst comprises 40 wt. percent AlCl (based on 5 support). The support contains 4 wt. percent FeCl and wt. percent alumina-silica. 'Ihe alumina/silica weight ratios are preferably'about 10/90 to 30/70, e.g. 20/80.

products in the presence of substantial quantities of aro V 7 u matics, e.g. 1 wt. percent or greater based on the total]? the may P P P takes iced.

The reactants are introduced at an overall rate of 0.1-10 v./-v./hr. based on total catalyst.

. place in the,l preseri e of large quantities of aromatics.

Product efiluent is withdrawn through outlet 14 and consists primarily of isopentane and isohexane as well as unreacted feed materials. The product stream is passed to recovery zone 15 which may be any conventional re- The unique nature of the present invention is illustrated by the experimental results described below.

It was desired to react a relatively high molecular weight paraffin, i.e. normal decane, and a relatively low covery means such as a distillation or scrubbing Zone. 5 molecular weight isoparafiin, i.e. isobutane, in the pres- Generally unreacted isob-utane is recovered through line ene of high concentrations of aromatics (12.4% on 16 and may be recycled for further conversion. Typiealtotal feed or 37 wt. percent toluene based on feed). ly, a C product may be recovered through line 18 and a In the comparative runs, the hydrocarbons were reacted lighter product fraction withdrawn by outlet 17. Means, under identical temperature and pressure conditions, renot shown, may also be provided for recovery or any action being carried out in the liquid phase to substantial catalyst entrained in the product completion (4 hour period in each case). The experi- Catalyst may be periodically or continuously fed to, mental runs illustrate the use of catalyst systems employand/or withdrawn from, the reaetioii zone by line 13 ing (1) AlCl alone, (2) AlCl on a support consisting in order to maintain the desired level of catalytic activity. of silica and alumina without iron chloride, (3) iron If desired, a catalyst promoter such as a hydrogen halide chloride and silica-alumina wthout aluminum chloride may be introduced into the reaction zone although this and (4) the catalyst of the present invention, i.e. alumiwill normally not be necessary.- num chloride on a support of iron chloride, silica and In its broadest aspects, the present invention is applialumina. Additionally, the present catalyst is compared cable to isomerization reactions as well as paraffin alkylawith AlCl on gamma A1 0 heretofore one of the few @1011 y Isomefization reactions Comer? Pflfflffill catalysts shown to have fair activity in the presence of feed material into isomeric molecules of substantially the aromatics m carbon number e m e P The support for the present catalytic system was prethe P N 9f e f We 9Pe fi 1s pared by conventional techniques. A mixture of 6.7 reqmreli as a g i g t g z fl l f i fi parts by weight of silica to one part alumina (in this case aroinauqs 1 0 9 no 9 Secunng a standard catalytic cracking catalyst sold under the trade desired isomerlzation yields. Thus, use of the present 7 a name of DA-l) was calcined at 1200 F. for three hours. invention will greatly reduce or eliminate the problem of when cool am of th 1 d removing aromatics from the feed Oil stream to the 2 P e In an isomepizafion 201m 7 V ether solution containing 1 part by welght of anhydrous The following table presents a compilation of data P6616111 ppr xnnately 10 volumes of dry th r, After illustratingthe presmt catalyst 15 mlnutes of mixing, the ether was decanted and the b I catalyst support dried under vacuum. It was then heated comWmw" under N at 610 F. for 1 hour andat 1000" F. for 1 hour using a quartz dish covered with asbestos board. gggf z Pef lggg The support was then cooled and impregnated with Alt-31 by mixing. w Pefqflt Mimi-am 'cm a g The finished catalyst was wt. percent AlCl (based on Total s pp 25-90 40450 on total support), the support being 10 percent Support;

m. lpercenl oilliOllqgnn'd; 5.50- kg 40 FeCl and a 90 wt. percent mixture of 511162. and alumina a... 5-30 Wt. Psr e iit snic re s itmtn m the welgm ratlo alumina 25-90 -90 The reaction conditions as well as product distribution are set forth in Table 2.

Table 2 I A101 on 10 wt. percent Buns A101; with support of FeCla and A1013 on 10% A101; on

no support Silicawt. Silica- R61 and 90% 7A1z03 Alumina 1 Alumina Silica-Alumina F 6, gram 104. s

. no". Toluen Oonditlons: i

. .Temperatme, F

Time, Hr PreSSu're,psl2 Analasisof0;+1roduet-Wt.percentz p v 1 2.6 1.1 17.7 6.8 0.5 0.2 1.6 0.5 3.1 1. 3 19.3 7.3 2,3 Dimethyl utane 0.2 0.1 0.3 0.3 2 methylpentane, 2,3,dimethylbu- 1. 1 0. 4 7. 5 5.3

time and cyclopentane. r 3 methylpentane, cyclohexanenn V 0. 5 0.1 3. 5 2.3 Del. 0.1 0 0.8 0.'5 05H 9.7 1.0 9.4 6.5 u 11.6 1.6 22.0 14.9 I 14. 7 2. 9 41. 3 22. 2 2,2 Dimethylpentane, as methyl- 0. 3 0 0. 2 0. 2 pentane methylcyclopentane. 2,3 Dimethylpehtane. 3,3 0.1 0 ---.do. 0.6 1.1

methylp'entan'e.

0 0 0.1 0 21.7 37.2 -.--do I 18.0 18.4 22.0 37.2 do 18.9 19.7 63.3 59.9 100. 39.8 58.1

The weight percentage of C and C products, particularly the branched materials, is the true index of the yields of desired products since they are the principal high octane components desired from the paraflin alkylation reaction. Additionally, the rest of the product stream is principally unreacted feed constituents. Comparing the present catalyst (Run 4) with Runs 1, 2 and 3 (AlCl alone or on a support consisting of silica-alumina, or iron chloride on silica-alumina), it is seen that aluminum chloride on a support of iron chloride, silica and alumina gives many fold higher yields of desired C and C products in the presence of aromatics. Even when compared to the catalyst of Run 5, which heretofore was considered to be a fairly good catalyst for efiecting reaction in the presence of large quantities of aromatics, the present invention gives yields twice as large.

It is to be further noted that it is the combination of constituents found in the present invention, rather than any individual component, which is responsible for the greatly increased yields.

The above experiments are set forth by way of illustration, rather than limitation, of the present invention.

summarily, by operating in accordance with the present invention, paraflins can now be successively converted to good yields of isoparaflins without requiring aromatics removal from the parafiin feedstock. Both operational and investment costs of the overall system are thereby greatly reduced.

Having described the present invention, that which is sought to be protected is set forth in the appended claim.

What is claimed is:

A process for converting parafiins into isopar-afiins which comprises passing a feed stream containing relatively high molecular weight normal parafiins and relatively low molecular weight isoparaflins into a reaction zone maintained at reaction temperature, there being present in said feed stream about 15 to 37 wt. percent aromatics based on C feed constituents, and contacting said feed stream in said reaction zone with a catalyst comprising aluminum chloride on a support, the amount of said aluminum chloride being in the range of about 25 to 90 wt. percent based on total support and said support consisting essentially of iron chloride, silica and alumina, said iron chloride representing from about 5 to wt. percent of said support.

References Cited in the file of this patent UNITED STATES PATENTS 2,349,458 Owen et al. May 23, 1944 2,393,104 Crosse et al Jan. 15, 1946 2,476,416 Ipaticfi et al. July 19, 1949 2,695,325 Stoops Nov. 23, 1954 OTHER REFERENCES Thorpe: Dictionary of Applied Chemistry, vol. I, pp. 560-561, and vol. IV, p. 392, Longmans, Green and Co., 1921.

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