US2443694A - Alkylation of hydrocarbons - Google Patents

Description

S'nn

V'Nl'lVv EzNEsT F. viveza j; Loma ALLAzzE @c0265 B uATcu I VENTORS E. F. PEVEREv ETAL ALKYLA'IoN 0F HYDRocARBoNs June 22, 1948.

Patented June 22, 1948 ALKYLATION 0F HYDROCARBONS Ernest F. Pevere, Beacon, Louis A, Clarke, Fish,- lrill, and George B. Hatch, Beacon, N. Y., assignors, by mesne assignments, to The Texas Company, New York,

l Delaware Y., a corporation of ApplicationMay 7, 1941, Serial No. 392,396

1 Claim. (Cl. 2,60-6834) This invention relates to the alkylation of hydrocarbons and has to do with a process for the reaction of certain paran hydrocarbons with olens to produce saturated hydrocarbons of high anti-knock value, suitable for the manufacture of motor fuel.

This is a continuation-impart of copending application, Serial No. 214,488, iiled June 18, 1938.

Moreparticularly, th'e present invention is an improvement in the method for the alkylation of isoparailns with olefins in the presence of sul furic acid as the catalyst. The invention is particularly applicable to the alkylation of lower boiling isoparafns, such as isobutane and isopentane, with normally gaseous olens, including mal butenes; isobutylene, orpolymers thereof, for f' example, di-isobutylene and tri-isobutylene; or co-polyiners resulting from the polymerization of one molecule of normal butene with' one molecule of isobutylene.

In the alkylation of isoparainns with olens 'L-f using sulfuric acid as a catalyst, it is customary to contact the mixture of olefin andisoparaiiin with the acid under such conditions that alkylation of the isoparaiiin with the olen occurs to produce branch chain saturated hydrocarbons.

One of the conditions found conducive to the said alkylation reaction is the maintenance of a high'molar ratio of isoparaiin to olefin in the alkylation reaction zone. In accordance with the present invention, the oleiin feed is mixed with previously formed alkylate containing a high proportion of isoparaiiln hydrocarbons prior to contacting the olefin with the acid catalyst.

As applied to a countercurrent type of operation using a multiple injection of the olens between stages in a multi-stage operation, the oleiins according to the invention may be injected into the hydrocarbon layer of the settlers, whereby the ollns are mixed with the reaction products containing a high proportion of isopara'in to effect dilution of the olefins before contacting the mixture with the acid catalyst in a subsequent mixer.

The invention will be more fully understood from the following description read in connec tion with the accompanying drawing, which' shows diagrammatically a sketch of one form of apparatus for carrying out the process of the invention. In the drawing, there is shown a fivestage countercurrent system but the number of stages'may vary and it is to be understood that the invention is applicable to other systems, either single stage or multi-stage, for carrying out the herein described type of alkylation.

. Referring to the drawing, the isoparafiin charging stock is introduced by the line I and pump 2 into a mixer 3 which is provided with a stirring mechanism 5. The charging stock may be mixed with additional isoparaflin, recycled in the system through the line 6, as explained more fully hereinafter. In the mixer 3, the isoparafn is intimately contacted with used acid, which' maybe spent or partially spent, introduced through the line The acid may contain a substantial amount of absorbed olelns and it is intended that the acid be stripped of these oleflns by contact with the isoparaflin in the mixer 3. Due to the high ratio of isoparain, favorable conditions are provided for the alkylation of the isoparaln by the olens. The acid and hydrocarbon mixture is transferred from the mixer 3 through the line 8 vto a settler I0, wherein the stripped acid separates from the hydrocarbons and collects in the lower portion of the settler and may be withdrawn through the valve controlled line I2. The mixer 3 and settler Il! comprise the acid stripping stage, wherein only isoparains are contacted with' the used acid. While only one stage of acid stripping is shown, it is to be understood that any number may be used.

The hydrocarbons collect in the upper portion of the settler I0 and into this hydrocarbon layer is introduced a portion of the olefin charge by line I4 which communicates `with the olen cli'arging line I5 containing a, pump I6. By suitable adjustment of the valve I8 in the line I 4, any portion of the olen charge may be introduced into the hydrocarbon layer in the upper portion ofthe settler Ill.r The olens introduced through the line I4 commingle with the hydrocarbons in the settler and are diluted thereby to produce a mixture contaim'ng a high proportion of isoparailin to oleilns, which is favorable for obtaining the alkylation reaction. Ordinarily, the proportions of olen introduced through the line I5 and the isoparafn introduced through the line I, are such as to give an overall ratio of isoparaiiin 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 theolen charge. is split between three stages, approximately one-third should be introduced through the line I4 into the settler l0.

The hydrocarbon mixture is transferred from the upper portion of the settler I8 through the line I9 to a mixer 26, provided with a stirring mechanism 2I.- linv the mixer.v 20, the mixture of isoparafn and olens is intimately contacted with partially spent acid introduced into the lower portion of the mixer through the line 22. The reaction products are withdrawn from the mixer 20 through the line 24 and introduced into a settler 25. In this settler, the acid vand hydrocarbons stratify and the lower acid layer is con-` ducted from the settler through the valve controlled line 8 to the mixer 3, referred to heretofore. Into the upper hydrocarbon layer of the settler 25 is introduced additional olefinthrough th'e line 26 which communicates with the olen charging line I5. By suitable regulation fof the valve 28 in the line 26, any proportion of the oleiincharge may be commingled with the hydrocarbon .layer'in the settler 25.

The hydrocarbon mixture is transferred from the settler -25` through the line 29 toa mixer 30 provided with a stirring mechanism 3|. In the mixer 38, the hydrocarbons are contactedwith 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 toa settler 35 wherein the separation'of acidy and hydrocarbon is .allowed to takeplace. The. acid layer collecting in the bottom is allowedto flow through the valve controlled line 22 to themixer 20, referred to'heretofore. Additional olefin is injected into the hydrocarbonlayer of settler 35, by means of the line 31 which communicates'with the olefin charging linel, wherebya portionof olefin may be introduced into settler'35 byvregulation of the Valve 38 in the line 31.

The hydrocarbon mixtureis transferred from thesettler 35 throughthe vlinev 39 to` a mixer 40 provided with a stirrer 4l which -intimately mixes the hydrocarbon with the partially spent acid ntroduced into the mixer through' the line 42, The reaction mixture from the mixer -40'is passed through the line 44 to a settler 45 wherein the ac idfseparates as a, lower layer from the hydrocarbons and is withdrawn through the valve controlled line 33 to the mixer 30, referred to heretofore. The hydrocarbony layer vcollected. in the upper portion of the settler 45 is transferred throughthe 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 4 be'used if desired. Thelnal mixer 48 provides an opportunity for effecting reaction of substantially all the remaining cleiin with theisoparain.

The acid introduced into the mixer 48. is fresh or new acid, which `should be about 93 to 100% or more: concentration, orapreferablyf'about 94 to 98%. This acid, which may be new-"or restored acid, is introduced through the-line 50- by pump 5|.- The amount of acid introduced is sucient to make the overall ratio of acid to olefin charge about 1:1 or less, and preferably about .5 to .8121. 'lhefreaction` mixture is transferred from the mixer 48 through the, line 53' to alsettler 54, and the acid collectingin the lower layer ofthe settler is conducted through the valve controlled line 42 4to the mixer 48, referred to heretofore. Thehydrocarbons are passed fromthe upper Aportion-ofithe settler 54 through-the line 56 to a mixer y58 provided with 11a s tirrer '58.

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 8l. The mixture of neutralizing reagent andhydrocarbonis passed .through the line 63 to a vsettler `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 Iportion thereof recycled to the mixer 58 through the branch line 66, which communicates with the line B0. The neutralized hydrocarbons are transferred from the settler 64 through the valve controlled line 61 to fractionator 68. The 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 vaporizedand removed overhead through the vapor line 18, The bottoms of .higher boiling point than the desired motor fuel may be withdrawn from the lower portion ofthe fractionator through the line 12.

The overhead vapors removed through the vapor line 10 are intro'ducedinto the secondary fractionator or stabilizer 15, wherein a separation is made between the desired motor fuel and lighter hydrocarbons, such as the normally gaseous hydrocarbons. The motor fuel fraction is withdrawn from the lower portion of the fractionator 1.5 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 antiknock value, suitable for blending with gasoline.

The operation in the `fractionatorv 15 may vary considerably, but it is intended to make a separation ofv a fraction relatively rich in isobutane for recycling to the system. If a portionor 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 ther valve controlled line 80. 'I'he nature of the products discharged throughthe line llwill, of course, depend somewhat Von `the character of the charging stock. For example, if

the ycharging stock is a cracked fraction containing C4 hydrocarbons and lighter, the gases discharged through the line 88 may comprise C3 hydrocarbons andlighter. If the charging stock is essentially C4 hydrocarbons, then the overhead product from the fractionator 15 may comprise essentially isobutane, which may be taken overhead through the line 8| Ainstead of the line 18.

Inlease a portion or all of the normal butane 1s separated from the gasoline fraction withdrawn from.`I the lower portion of the fractionator 15 through the line 16, then itmay bedesirableA to separate a C4 fraction from the fractionator `15 and subject this fraction to further fractionation inanother fractionator, not shown, to separate the isobutane from the normal butane.` ln'either case, the isobutane from the line 18 or 8l is passed through a condenser coil 82 whereinitisconden-sed and the condensate passed throughwthe run-down line 83110 receiver 85. Any portion of the isobutane collecting in the receiver -85 may 'bel passed through the line 6 containing: a pump 86'v to the mixer 3, referred to heretofore.y

They reaction takingplace inthe system described is ordinarily in the liquid phase. Sunicient pressure is maintained on the hydrocarbons to maintain them in the liquid phase and this pressure will vary from atmospheric to substantial superai'mospheric pressure, depending on the temperatures 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 25 to 50 pounds. Sufficient time is provided to obtain substantially complete reaction of the olefins in the alkylation or" the isoparaffins. Ordinarily, the time would be about 30 to 9() minutes, and preferably 40 to 6() minutes.

As an example of the operation of the invention, the following data were obtained on a nvtstage counterfiow apparatus, using as the isoparaffin charging stock a fraction containing about 98% isobutane, and as the olefin charging stock plant gas which was a topped stabilizer reflux containing about 45% C4 olefins, and about 24% isobutane. The isobutane was contacted with the used acid in the first stage, and the plant gas was split and injected into the second and third stages.

Charge to stage No. 1 Isobutarie Charge to stage No. 2 Plant gas Charge to stage No. 3 Plant gas Concentration of sulfuric acid percent 98 Acid/ olen ratio 1.18 Isobutane/olein ratio 3.75 Temperature F 60.8 Contact time minutes 90 Percent sulfuric acid in recovered acid 94.4

311 F. fraction:

Percent yield by weight basis of olefin 146.2 Octane number CFRM 91.6 Bromine number 1 E11-400 F. fraction:

ercent yield by weight basis of olefln 19.1 Bromine number 1 It will be observed from the above 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 approximately 146%. Also, the recovered acid was of good quality and had a concentration of 94.4%.

The treatment of the used acid with isoparaffm may be used advantageously in connection with any suitable system, including countercurrent or concurrent operation, in which the acid is recycled. In such a case, the recycle acid and isoparafn may be contacted in a separate re actor, for example, the initial reactor, and the olefin charged to one or more successive reactors.

The feature of stripping absorbed olen from sulfuric acid by a low-boiling substantially olenfree isoparafn, such as isobutane, and then alkylating the isoparain and stripped olen product in the presence of an alkylation catalyst in a zene maintained under allylating conditions, is disclosed and claimed in the copendiiig parent application, Serial No. 214,488, filed June 18, 1938, now Patent No. 2,256,450.

While strong sulfuric acid has been described above as the allrylatiori catalyst, it is to be understood that this invention is applicable to the use of any other suitable alkyiation catalyst, such `a boron fluoride-Water complex, and aluminum halide with a hydrogen halide promoter, and an aluminum halide-hydrocarbon complex, and preferably such a complex containing suspended aluminum halide.

Obviously many modiiications and variation-s of the invention, as hereinbefore set forth, may be nia-de without departing from the spirit and scope thereof, and therefore only such. limitations should be imposer as are indicated in ""ie pended claim.

We claim:

1n a multi-stage process for the alkylation of an isoparar'iin with an olefin in tlie presence of an alkylaticn catalyst, the method which comprises continuously introducing isoparaflin and olenn with the isoparairln in substantial molar excess of the olefin into a first stage reaction zone, agitating the mixture therein in the presence of an alkylation catalyst under alkylating conditions, continuously passing a portion of the resulting mixture from the first stage reaction zone to a iirst stage settling Zone, allowing the mixture to settle therein to separate into a lower settled acid layer and an upper separated hydrocarbon layer free from catalyst and containing alkylate and excess isoparain, introducing additional oleiin into said separated hydrocarbon layer in the first stage settling zone whereby the said additional olefin is diluted by the allrylate con taining excess isoparaffm in the absence of cata lyst, continuously passing said upper hydrocarn bon layer containing diluted olen into a second stage agitated reaction zone where the mixture is brought into contact with additional alkylation catalyst under alkylating conditions, and passing the resulting mixture from the second stage reaction zone to a second stage settling zone, whereby all the alkylate flows serially through the system and the entire quantity of alkylate from the first stage reaction zone is used to dilute the olefin feed to the said second stage reaction Zone.

ERNEST F. PEVERE. LOUIS A. CLARKE. GEORGE B. HATCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,211,747 Goldsby et al Aug. 13, 1940

Images