US2348467A - Alkylation of hydrocarbons - Google Patents

Description

May 9, 1944. A R; GoLDsBY lEr AL ALKYVLATION OF HYDROCARBONS Filed May 1o, 1941 HVZTV' ARTHUR EGOLDSBY A EENEIT F PEVEZE LOUIS A-.CLAZKE GEOZGEHATCH INVENTOR Am fl A7 Patented-,May 9, 1944l a ALKYLATION OF HYDROCARBONS Arthur n. Grimsby and Ernest F. revers, Beacon, Louis A. Clarke, Fishkill, and George B. Hatch, Beacon, N. Y., assignors, by mesne assignments;

to The Texas Company, New

poration of Delaware AYork, NKY., a cor- Application May 1o, 1941, serial No. 392,314

' 4 claims. (cl. 26o-683.4)

This invention relates to the alkylation of hydrocarbons and has to do with a process for the lreaction'of certain paramn hydrocarbons with oleflns to produce saturated hydrocarbons of lhigh anti-knock value, suitable for the 'manufacture oi motor fuel.

This is a continuation-in-part of our cepending application, Serial No. 214,488, led June` 18, 1938.

I More particularly the present invention is an improvement in the method for the alkylation of isoparains with oleiin's in the presence of sulfuric acid as the catalyst. 'I'he invention is particularly applicable to the allq'lation of lower boiling isoparaiilns, such as isobutane and isopentane, with normally 'gaseous oleilns, including cracking still gases or a fraction thereof such Vas a fraction containing predominantly C4 hydrocarbons'or C: hydrocarbons or a mixture of C3 and C4 hydrocarbons; propylene; isomeric normal butenes; isobutylene, or polymers thereoi', for example, diisobutylene and tri-isobutylene; or co-polymers resulting from the polymerization of one molecule of normal butene with one molecule of isobutylene.

In the alkylation pf'isoparamns with olens `using sulfuric acid as a catalyst, it is customary to contact the mixture of olen and isoparailin I V.'with the acid under such conditions .that alkylation of the isoparafns with the olen occurs to produce branch chain, saturated hydrocarbons. In a continuous type of operation, wherein a stream of hydrocarbons is charged to the' system and a stream of spent or partially spent sulfuric acid iswithdrawn, there may be a substantial amount of oleiins absorbed by the acid and lost or removed from the system .with the withdrawn' used acid. The loss of oleilns in the used acid is particularly observed when the reaction'is carried out in 'a preferred type of continuous multi-stage ccuntercurrent operation, wherein the used acid immediately before withdrawal from the system is ordinarily contacted with the fresh hydrocarbon charge and tends to absorb olei'lns therefrom. .Y

The used acid, before withdrawal from the alkylation system, is treated with the isoparaiiinto strip-the acid of its olen content. Although not restricting the invention to any particular theory of reaction, it -is believed that the oleilns absorbed by the acid alkylate the isoparaiiln, which is in relativelyfhigh ratio to the olens. during the stripplnt operation. As applied to a countercuri'ent flow type of operation, the stripplngoftheusedacidmaytakeplaceinoneor more additional stages "wherein only the isoparaihn, which may be the stream of isoparaffin charging stock, is contacted with the used acid. The invention will be more fully understood from the following description read in' connection with the accompanying drawing, which K shows diagrammatically a sketch of one form of:

apparatus for carrying out the process of the invention. In 'the drawing, there is shown a ve-stage countercurrent system, but the number of stages may vary, and it is to be understood that that part of the invention, insofar as it relates broadly to the isoparamn stripping of the used acid, is ap'plicable-'to other systems for carrying out the, herein described type of alkyla-.

` tion operation.

Referring to the drawing, the isoparaiiin charging stock is introduced by the une ll and Y pump 2 into a mixer 3 which is provided with a stirring mechanism 5. The charging stock may be mixed with additional isoparaiiin, recycled in the system through the line 6, as explained more fully hereinafter. f In the mixer 3, the isoparafiin is intimately contacted with used acid, which may be spent or partially spent. introduced through the line 8. The acid may ,contain a substantial amount of absorbed oleilns and it is intended that the acid be stripped of these oleiins by contact with the isoparain in the mixer 3. Due to the high ratio of isoparamn, favorable conditions are provided for the alkylation of the isoparafn by the oleilns. The acid and hydrocarbon mixture is transferred from the mixer 3 throughthe line 9 to a settler lll, wherein the The hydrocarbons collect in the upper portion of the settlerv l0 and into this hydrocarbon layer is introduced a portion of the oleiin charge by line Il which communicates with the Voleiin charging line II containing a pump li. By suitable adiustment of the valve It in the line I4.

any portion of theoleiin charge may be introduced into the hydrocarbon layer in the upper portion of the settler l0. The oleiins introduced through the line Il commlngle with the hydrofcarbons in-thesettler and are diluted thereby to produce a mixture containing a high proporduced through the line I, are s'uch as to give an overall ratio of isoparafiin to olefin of at least 1:1, and preferably from about 3:1 to 5:1. The olefin charge is ordinarily split between a number of stages, and one'skilled in the art will be able to split the olefin charge to introduce the desired amount into each stage. Ordinarily, the proportions introduced in the various stages are about equal and in case the olefin charge is split between three stages, approximately onethird should beintroduced through the line I4 into the settler I0.

The hydrocarbon mixture is transferred from Y the upper portion of the settler I0 through the,

line I9 to a mixer 20, provided with a stirring mechanism 2|. In the mixer 20, the mixture of isoparaflin and oleiins is intimately contacted with partially spent acid introduced into the lower portion of the mixer through the line 22. 'I'he reaction products are withdrawn from the mixer 20 through the line 24 and introduced into a settler 25. In this settler, the acid and hydrocarbons stratify and the lower acid layer is conducted from the settler through the valve controlled line 8 to the mixer 3, referred to heretofore. Into the upper hydrocarbon layer of the settler is introduced additional olefin through the line 26l which communicates with the olefin charging line I5. By suitable regulation of the valve 28 in the -line 26, any proportion of the olefin charge may be commingled with the hydrocarbon layer in the settler 25.

The hydrocarbon mixture is transferred from the settler 25 through the line 29 to a mixer 38 provided with a stirring mechanism 3|. In the mixer 30, the hydrocarbons are contacted with sulfuric acid catalyst, comprising partially spent sulfuric acid introduced through the line 33. The reaction mixture is conducted from the mixer 30 through the line 34 to a settler 35Wherein the separation of acid and hydrocarbon is allowed to take place. The acid layer collecting in the bottom is allowedto fiow through the valve controlled line 22 to the mixer 20, referred to heretofore. Additional olen is injected into the hydrocarbon layer of settler 35, by means of the line 31 which communicates with the olefin charging line I5, whereby a portion of olefin may be introduced into settler 35 by regulation of the valve 38 in the line 31.

The hydrocarbon mixture is transferred from 'the settler as through the une 3s to a mixer 4u v`provided with a stirrer 4I which intimately mixes the hydrocarbon with the partially spent acid introduced into the mixer through the line ft2. The reaction mixture from the mixer til is passed through the line 46 to a settler i5 wherein the acid separates as a lower layer from the hydrocarbons and is withdrawn through the valve controlled line 33 to the mixer 30, referred to heretofore. The hydrocarbon layer collected in the upper portion of the settler 45 is transferred through the line 41 to a mixer 48, provided with stirrer 49. While there is shown no injection of olefin into'the hydrocarbon layer in the-settler 45, it is to be understood that such injection may be used if desired. The final mixer 48 provides an opportunity for eii'ecting reaction of substantially all the remaining olefin with the isoparafdn.

The acid introduced into the mixer 48 is fresh or new acid, which should be yabout 93 to 100% or more concentration, or preferably about 94 to 98%. This acid. which may be new or restored acid, is introduced through the line 50 by pump 5I. The Aamount of acid introduced is sufficient to make the overall ratio of acidto olefin charge about 1:1 or less, and preferably about .5 to .8:1.

The reaction mixture is transferred from the mixer 48 through the line 53 to a settler 54. The acid and hydrocarbon separate in the settler 54 and the acid collecting in the lower layer of the settler is conducted through the valve controlled line` 42 to the mixer 48, referred toheretofore. The hydrocarbons are passed from the upper portion of the settler 54 through the line 56 to a mixer 58 provided with a stirrer 59.

In the mixer 58 the hydrocarbons are intimately contacted with a neutralizing reagent, such as an aqueous alkaline solution, for example, dilute caustic solution, introduced through the line 60 by the pump 5 I. The mixture of neutralizing reagent and hydrocarbon is passed throughthe line 63 to a settler 64 wherein the neutralizing reagent settles out and may be withdrawn from the lower portion of the settler through the valve controlled line 65 or any portion thereof recycled to the mixer 58 through the branch line 65, which communicates with the line 60. The neutralized hydrocarbons are transferred from the settler 84 through the valve controlled line 81 to fractionator 88. 'I'he fractionator 68 is provided with suitable heating means, such as heating coil 69, whereby substantially all hydrocarbons within the motor fuel boiling range and lower are vaporized and removed overhead through the vapor line 10. The bottoms of higher boiling point than the desired motor fuel may be Withdrawn from the lower portion of the fractionator through the line 12. .i

'I'he -overhead vapors removed through the va- Y por line 10 are introduced into the secondary fractionator or stabilizer 15, wherein a separation is made between the desired motor fuel and lighter hydrocarbons, such as the normally gas-e eous hydrocarbons. The motor fuel fraction is withdrawn from the lower portion of the fractionator 15 through the valve controlled line 16. This motor fuel may be a `stable or unstable product falling within the boiling range of gasoline or a normally liquid hydrocarbon fraction of high anti-knock value, suitable for blending with gasoline.

The operation in the fractionator 15 may vary considerably, but it is intended-to make a separation of a fraction relatively rich in isobutane for recycling to the system. If a portion or all of the normal butane is retained in the gasoline which is drawn from the lower portion of the fractionator, the remaining products may be fractionated to obtain an isobutane cut which may be Withdrawn as a side stream through the valve controlled line 18, and the lighter hydrocarbons released from the upper portion of the fractionator through the valve controlled line 80. The nature of the products discharged through the line 88 will, of course, depend somewhat on the character of the charging stock. For example, if the charging stock is a cracked fraction containing C4 hydrocarbons and lighter, the gases discharged through the line may comprise C:

assess? i hydrocarbons and lighter. If the charging stock is essentially C4 hydrocarbons, then the .overhead product from the fractionator 'Il may comprise essentially isobutane. which may-be taken overhead through the line Il instead of the line 1l.

In case a portion or all of the normal butane isseparated from the gasoline fraction withdrawn from the lower portion of the fractionator l 'I9 through the line 18, then it may be desirable to separate a Cifraction from the fractionator 1l and subject this fraction toffurther fractionation in another fractionator, lnot shown, to separate the isobutane from the normal butane. In either case. `the isobutane from the line 19 or Il is passed through a condenser coil l2 wherein it is condensed and the condensate passed through the run-down line 93 to receiver Il; Any portion of the isobutane collecting in the receiver 95 may be passed through the line I containing a pump 99 tothe mixer 3, referred to heretofore.

'me treatment or mensen scia with nepal-sinn may be used advantageously in connection with any suitable system, including coimtercurrent or concurrent operation. in which the acid is recycled. In such a case, the recycle acid and isoparaiiin may be contacted in a separate reactor, for example the initial reactor, and the olenn charged to one or more successive reactors. Moreover, this invention is applicable to a process, either with single stage or multi-stage rc -l actors, of the type wherein the olefin' charge is treated in the tlrst step with sulfuric acid from any source, either fresh or partially spent, imder The reaction taking place in the system described is Ordinarily il the liquid Phase. Bum' cient pressure ismaintained on the hydrocar bons to maintain them in the liquid phase, and

this pressure will vary from atmospheric to sub..

stantial lsuperatmcspheric pressure, depending on the temperature employed. The temperature may vary from to 125 F. or higher, and preferably about`60 to 90 F.' At these temperatures the pressures may vary from 0 to about 100 pounds or more, and preferably about to '50 pounds. Sufiicient time is provided to obtain substantially complete reaction of the olenns in the alkylation of the iso. the time would be about to 90 minutes, and

'y preferably 40 to"`60` minutes.

As an example of the operation of the inveni tion; the following data were obtained on a fivestage counternow apparatus, using as the isoparafiin charging stock a fraction containing about 98% isobutane, and as the olenn charging stock plant gas which was a topped stabiliser reflux containing about 45% C4 oleilns, and about 24% isobutane.' 'I'he isobutane was contacted with the used acid in the rst stage and the plant gas was split and injected into the second and third stages. charge to stage No. i nobutsne Charge tostage No. 2 Plant gas Charge to stage No. 3 Plant gas Concentration-of sulfuric acid l It will be observed from thetabove results that using an isobutane stripping stage in which the spent acid prior to withdrawal from the system was contacted with the isobutane charge only,

the yield of 311 end point product was approxis,

mately 146%. Also,- the recovered acid was of good qualitylzand had aconcentration of 94.4%.

Ordinarily,

v pended claims. l

conditions to absorb oleiins in the acid; and the absorbed olenns or` olefin-acid reaction products are subsequently alkylated with isoparai'lin in a second step in the presence of a suitable alkylation catalyst. TheA strippingof the absorbed olei'ins or olefin-acid reaction products, such as alkyl esters, by means of substantially olefin-freel isoparafiin such as isobutane, removes these products from the absorption acid in a concentrated or purified condition. This isoparamn solution of the olen product, when separatedfrom the absorption acid, constitutes a satisfactory charge for catalytic alkylation operation. Moreover, while strong sulfuric acid has been described above as a preferred alkylation catalyst,

it is to be understood that this invention is applicable to the use of any other suitable alkylation catalyst, such as a boronnuoride-water com..

plex, an aluminum halide with hydrogen halide promoter. and an aluminum halide-hydrocarbon complex, and preferably such a complex containing suspended aluminum halide, for the alkylation of the isoparailin and stripped olenn product. The present invention has the advantage of producing increased yields of the desired products and increased acid concentration which permits the use of a smaller fresh acid dosage and longer use of the acid.

The species of treating used alkylation acid, such as recycle acid. with sin isoparafiln to re'- cover olefin and produce additional alkylate therefrom is disclosed and specifically claimed in a reissue application, Serial No. 412,166, filed Beptember 24, 1941, of Patent No. 2,256,450,y granted September 16, 194i. upon an application, Serial No. 214,488, filed June 18, 1938. The additional species of a plural stepoperaticn inA which olefin is absorbed in acid in a Vfirst step, the resulting acidy containingabsorbed olen is stripped with isoparailln to recover the absorbed olefin, and the isoparailin with stripped olefin product is then .treated in a second-step in an alkylaticn vlame where isoparamn is alkylated with the olenn product in the presence of an alkylation catalyst, is disclosedl and generically claimed herein.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap- We claim: l. The process which comprises forming a so lution .of olen in sulfuric acid, subjecting said solution to contact with substantially olen-free low-boiling isoparailinto strip absorbed olen product from the acid, and passing the resulting mixture of low-boiling isoparanln and stripped olefin product to a reaction zone containing an alkylation catalyst maintained under alkyl'ating conditions such that the isoparaiiln is alkylated by the olefin product with the formation uof saturated hydrocrabons vboiling within the gasoline range.

2. The process which comprises forming a so? lution ot normally gaseous olen in sulfuric acid, subjecting said solution to contact withisoparaifin consisting essentially of isobutane to strip the absorbed olein product from the acid, and passing the resulting mixture of isoparamn and stripped olen product to a reaction zone containing strong sulfuric acid maintainedv under alkylating conditions such that the isoparafiln is alkylated by the olen product with the formamaintained under alkylating conditions to Produce saturated hydrocarbons boiling within the gasoline range.

4. The process which comprises passing an olefinic hydrocarbon fraction into contact with sulfurie acid under conditions such that at least a part of the olen is absorbed by the acid, treatr ing the acid containing resultant absorbed olen with a low-boiling isoparafn under conditions to strip absorbed olen from the acid, separating the isoparamn containing the stripped olefin product from the acid, and reacting the separated isoparafilncontaining the stripped olen ptoduct in a reaction zone containing an alkylation catalyst maintained under alkylating conditions such that isoparain is alkylated lWith the olen product to produce saturated hydrocarbons boiling within the gasoline range.

ARTHUR R. GOLDSBY. ERNEST F. PEVERE. LOUIS A. CLARKE. GEORGE B. HATCH.

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