US2417251A

US2417251A - Alkylation process

Info

Publication number: US2417251A
Application number: US462899A
Authority: US
Inventors: Charles E Hemminger
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1942-10-22
Filing date: 1942-10-22
Publication date: 1947-03-11
Anticipated expiration: 1964-03-11

Description

March l1, 947..

C. E. HEMMINGER ALKYLATION PROCESS Filed bot. 22, 1942 .VBS ma.

Patented Mar. 11, 1947 diaries. ,Hemmingen weitet, @einer to StandardvOil Development Company; a corporation of Delaware ppli-cation ctober 22, 1942, Serial o.42,8

The present inyention relates to improvements inthe ait of th a1ky1ation of oiens with isoparains and, more particularly, it relates to improvements in 'the process o f producing an alkylate boiling within the gasoline 'range from an olefin and isobutane employing weaker sulfurie acid and higher temperatures than have heretofore been employed.

Asis generallyl known, branch chain hydrocarbons boiling within the gasoline range and haring an octainenurhber of 1 00 or higher may be produced Aby reacting together an isoparafn, such as isobutane, with an olefin, such as butylene in the presence ofstrong sulfuric acid, say lacid or 9e- 100% strength, at temperatures o f the order ff vabout F. It has been found that the alkylation process previously indicated carriedoutcontinuously that improvement in both quality rand yield risY maintained by maintainingn'in the reaction Zone a relatively large i'riole'cular 'ecess of isobutane over the olefin. For'exanple, where 'fat least 50 mois of the isoparaffnare present for eachniol of the olefin in thealkylation Vzone good results are obtained in that ythe yields are improved and the quality of the product is 'improved over processes in which the molecular excess of the isoparain is substantially less. v Y I` have lnov) follnd that by employing C3 and Cato C7 oIens, aswell 'as C4'o1ens and by operyating yat higher temperatures during the alkyla- 'tion of theCa and C's t C7 lens, than customaruyf'eiiiployed during C4 folen'n aikyianon; 1 may employ sulfuric acid of 'l5-85 weight per cent l'and thereby eect considerable economy of operation, as regards acid consumption. For example, inthe usual process of preparing an alkyllatedfrom isobutane and butylene employing strong sulfuricacid of say 98%, and withdrawing acid at 92% strength, the acid consumption is of the order of 1.2 lbs. of acid per gallon of allg'ylate 1:ro'd1 .1.ced--v I have found that I may re- -duce this acid y consumption to 0.8 lb. of acid of 35% strength perfgallon of valkylate produced. AI 1have ils'o-fcuii1d that by decreasing the externalrat'io 'of isopar'afn to olen to within the 'range of from y2-4 mols of vis'op'arailin `per molof volen, I may'also increase the production of the alkylate per volume of isobutane which Ais usually the critical material for alkylation. Thus, I vmay "reduce the isobutane requirement from 1.125Iv gallons of isobutane to about 1 gallon of isobutane by my improved process.

I Ihave further found 'that the most desirable 4 claims. (c1. tsaii) ploy as' a 'feed stock a cnt or 'fraction say from a catalyticcracliiing operation containing C3, C4, C5, C, and Ci hydrocarbons. According to my preferred procedure, the C4 hydrocarbons are alkyl'ated under the usual alkylatingconditions, that is, employing strong acid (over 92%). The C3 hydrocarbons and the lower boiling 'portionof the C5 hydrocarbons, are then alkylated with the spent butene alkylation acid until its concentranon is reduce'dt about 8o to 90%, a5 %v preferred weight per cent. The balance of therCs, C, and C1 hydrocarbons are thenalkylated with an 'acid vof about 75% strength. This series of operation reduced the 'acid con'sur'nptionper unit of hal alkylate to about 'one-half of vthe amount previously employed, and also gives a greater yield of alkylates, since saturated products are obtained Yfro'rri the C, C, andC'v Olens Withthe corrsumptiori of lower amounts of isobutan'e than usual, the remainder being available for alkylation of the C and C4 olens. The spent acid from the 75% strength alkylatioh 0f the heavy olens may be used to pretreat theheavier olefins to remove the dienes so as to reduce the acid consumption in the alkylation step. This pretreating is preferably accomplished with' acid :d'iluted to iiD-% strength.

The main object of my present `invention, therefore, is to devise a process Yfor alkyl'ating a relatively Wide range of olenic hydrocarbons, that is from C3 to C7 olens, in stages, 'employing the spent acid from one vstage vas the alkylat'- ving catalyst in another stage, thus reducing v"substantially the acid consumption and effecting appreciable economy.

Another object offthis invention is to provide alkylation technique adapted to obtain the maximum amount of alkylate from a given amount of isobutane.`

Other and further objects of my invention 'will appear fromthe following more detailed description and claims. o

In the accompanying drawing', I have shown a Vflow plan which indicates 'diagrammatically fa preferred method of earryingmy invention Yinto practical effect.

I shall no wsetoforth a specific example or my inventionhan'd referto the drawing. It willrbe understood that the following details are 'purely for purposes of illustration and not not impose `any limitation on my invention. o

In reference to the drawing, the lighter ends of 'a cracked pe'troleu'rn'gas oil vwere introduced into the present Is'y'slter'n through line yI `4andthfen'ce dschard into a ra'ct'nathg rcol'ifnn"'3 "'yvhere the cracked stock was fractionated as below indicated. The feed stock in line I contained Cs, C4, C5, Cs and C'z hydrocarbons and in the fractionating column the C4 hydrocarbons containing butenes were taken off as aside stream through line 4 and then discharged along with isobutane present in the C4 hydrocarbons and 4recycled isobutane fedthrough line 5 to line 4 into an alkylation reactor vI 'where they were treated n with sulfuric acid of from 92% to 95% at a temperature of 35-85 F. for a sui'licient period of time to effect the desired conversion. The alkylationV of the C4 hydrocarbons was carried out in known manner with the usual recycling of unreacted isoparaihn to the reaction Yzone from a distillation zone, and the process was otherwise operated according to known methods. It will be understood that if there is insufficient isobutane in the feed Vin line I, additional isobutane may be fed from some outside source to the system through line 6. I have shownv a settling drum 8 and a raw alkylate draw-off pipe I0, as well as an acid draw-off line I2. The raw alkylate in line IIIk was delivered to a fractionator I5 where it Ywas freed from isobutane, removed through line I8 and recycled through lines 5 and I I to reactor 'Land thence discharged'into a second fractionator` 25 from which normal butane was removed through line 2l. The raw alkylate was withdrawn through line 29. It will be understood that the produ :t withdrawn'through line 29 was delivered to conventional neutralizing, washing and distillation' equipment to produce a finished alkylate in apparatus not'shown. The spent acid in line I2 was in part'recycled to the alkylation zone l, but another portion of the spent acid was withdrawn through line I4. As is conventional, fresh acid was discharged from linel I6 into line I2 to fortify the acidre-entering alkylation zone intoV the alkylation zone 30 as shown. In alkylation zone 30 the temperature was maintained in the range of'frcm about 45"v F. to 100 F. Here, the ratio of acid to total 'hydrocarbon was from 100 to 500, and the external ratio of isoparafn to olen'was from'3 to 6 isoparaflin per mol of olefin. The isoparafiln in this case wasV supplied from extraneous sources and was introduced into line 20 throughline-2|. However,

4some of the isobutane in line 5 may bei'withdrawn through line I9 and discharged into line 25 entering the reaction zone 30; I'he alkylation product was withdrawn through line32 and dischargedinto asettling drum 34. The raw alkylate was-withdrawn through line'35 and delivered to fractionators l5 and 25 through line 3'I'to r cover isobutane for recycling to the system. The y acid, on the other hand, was withdrawn through 4line 38 and recycled in part to line I4 entering alkylation zone 30.' However, a major portion of this acid, which has a concentration of about- V85% by weight, was withdrawn through lineJlIl and mixed with bottoms withdrawn from column 3 through line 4Z in a manner which will be vpres-V .The acid inline I4 had' aV strength of about 'y ing of gases.

ently described more fully. The bottoms from line 42 contained that portion of the C5 cut not withdrawn through line 22, together with the Cs and C7 hydrocarbons and these were discharged into an alkylation zone 43 along with extraneous isobutane through line 44 and/or isobutane withdrawn from line 5 through line 9 where they were admixed with the acid discharged therein throughline 40. The temperature conditions prevailing in alkylation zone 43 were from 507 to 110 F.; the ratio of hydrocarbon to acid was about 2-5 parts by weight ofV hydrocarbon (total) per part of acid; and under these conditions an alkylation product was formed which was withdrawn eventually through line 50 and discharged into a settling Vzone 52 from which the separated raw alkylate was Withdrawn through line 55 and delivered, rst toV fractionators I5 and 25 and then delivered to finishing equipment to recover the desired product. The spent acid, on the other hand, which` had a strength of about '75% by weight, was withdrawn from settling Zone 52'through line B0. V'This `acid may be employed after dilution to about 65% `to treat the heavier olens in line 42 to remove diolens therefrom.

In reaction zone 43 and valso in reaction zone 30, the ratio of isobutane toolen entering the said reaction zones was preferably from 2-5 mols of isobutane per mol of olefin and not more than 6 mols of isobutane per mol of olefin. In both zones some parans were'form'ed by olefin polymerization, accompanied by carbon schismand hydrogen transfer.

It will be understood that the specific example which I have set forth above is Vpurely illustrative and numerous modifications of the invention may be madewithout departing from-the'spirit thereof. For example, I may employ some other Y alkylation catalyst than sulfuric acid, such as Vthe oxides of phosphoric acid, or sulfuric acid containing boron fluoride, nickel sulfate or hydrochloric acid. Also, thefeed stock mayv be a `different ycomposition than that previously' indicated' or vfrom other sources such zas' thermal cracking or reforming petroleum cuts or crack- To recapitulate, my invention resides inobtaining a greater amount of alkylate vfrom a given amount of isobutane and involves converting at least some'of the 'olens available in a renery, into saturated branched chain paraflinsV by Vpolymerization and inter-polymerization `of said olens, accompanied by some alkylation-with isobutane. The possibility of obtaining Darafiins from oleiins` by polymerization accompanied.I by

hydrogen transfer underA the conditions ,describedy vto increase yields. .Inall stages, 'ItV employ lower isobutane to olefin ratios than normally employed in alkylating C4 hydrccarbons I iamrjen'abled thus, to increase the .overall yield of desired product over thatobtainable fromalkylating merely the C4 or Cs olenic Yhydrocarbonsjaccording to known procedure. f Y i c Y 'Io illustrate thewadvantage ofrmyjinventlon:

When gallons/of a mixtureofolefins Ccontaining 20 gallons of C3 olefins, 'gallons'Crolens, 30 gallons Csjolyensw and15jgallonsCsand Cn olens areralkvletedungeri theionventinal operating conditions for alkylating butylene, where 90% or stronger sulfuric acid is used, with 6:1 isobutane to olefin molal ratio (external) and temperatures f 35 F., about 120 gallons of isobutane are consumed. However, following the process steps described above, only about 90 gallons of isobutane are required. Of course, the yield oi aviation alkylate is less, namely about 14() gallons of compound to 160 gallons when the larger amounts of isobutane are required. However, this yield is greater than if only the proportional part of olens were alkylated under usual conditions, namely about 120 gallons. On the other hand, if the same quantity of isobutane were used, 125 gallons, and excess olefins were available, the usual case in refinery balances, the alkylate yield would be 185 gallons. Thus, with the same size alkylate plant 185 gallons rather than 160 gallons are produced from the same amount of isobutane by this invention. The quality of the alkylate I produce in blends of high quality aviation gasoline containing tetraethyl lead is oi' the same quality as where only the C4 olens are employed.

Many modifications of my invention will occur to those familiar with the art. I am aware that I may not claim alkylation broadly, but I claim:

1. A combined method of converting a hydro-- carbon fraction containing Cs to C1 oleiins into substantially saturated hydrocarbons boiling in the gasoline range comprising alkylating the C4 oleiins from the C3 to C7 fraction with isobutane in the presence of concentrated sulfuric acid of alkylation strength in a first stage and alkylating the C3 and C5 to C1 olens from this fraction with isobutane in the presence oi sulfuric acid of alkylation strength less concentrated than said concentrated sulfuric acid at a temperature above 35 F. in a second stage and maintaining the external isoparaliin t0 olefin ratio lower in the second stage than in the iirst stage.

2. A continuous method for producing branch chain parain hydrocarbons which comprises fractionating a feedstock containing Cs to C7 olefinic hydrocarbons and isoparafns into an overhead fraction containing C3 hydrocarbons, a rst side stream containing the C4 hydrocarbons, a second side stream containing the C5 hydrocarbons, and a bottoms fraction, combining the overhead fraction with the second side stream fraction, alkylating the C4 hydrocarbons in the presence of strong sulfuric acid, alkylating the combined overhead and second side stream fraction with the spent acid from the alkylation of the C4 hydrocarbons and alkylating the bottoms fraction with the spent acid from the alkylation oi the combined overhead and second side stream fraction, and maintaining the external isoparafn to oleiin ratio lower in each succeeding Zone in the direction of flow of the acid than in the preceding zone.

3. A continuous method for producing branch chain paraffin hydrocarbons which comprises iractionating a feedstock containing C3 to C7 olenic hydrocarbons and isoparains into an overhead fraction containing C3 hydrocarbons, a irst side stream containing the C4 hydrocarbons, a second side stream containing C5 hydrocarbons and a bottoms fraction, combining the overhead fraction with the second side stream fraction, alkylating the C4 hydrocarbons in the presence of 92 to 95% sulfuric acid at a. temperature between 35 and 85 F. with an external isoparaiiin to olefin ratio of 6 to 1, and alkylating the combined overhead and second side stream fractions with sulfuric acid having a concentration between 80 and 90 at a temperature between 45 and 100 F., using an external isonaraiiin to olen ratio of between 3 and 6 to l and alkylating the bottoms fraction with a suluric acid having a concentration of about at a temperature between 50 and 110 F., and using an external isoparain to olen ratio between 2 and 4 to 1.

4. The method set forth in claim 2 in which the temperature in the several zones is progressively increased in accordance with the molecular weight of the olens undergoing alkylation.

CHARLES E. I-IEMMINGER.

REFERENCES CTTED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,267,457 Goldsby Dec. 23, 1941 2,256,615 Hederhorst Sept. 23, 1941 FOREIGN PATENTS Number Country Date 515,367 British Dec. 4, 1939