US2286504A - Process for the alkylation of isoparaffins - Google Patents

Description

June 16, 1942.

F. D. PARKER PROCESS FOR THE ALKYLATION OF ISOPARAFFINS Filed Jam. :50, 1939 @wu Y uw REBS NS@ QN mw e INVENTUR. Farrandl). Parker A TTURNEY wm ,NU N ow mm. n

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Patented June l 16, 1942 PROCESS FOR THE ALKYLATION F ISQPARAFFIN S arrand Parker, Los Angeles, Calif., assigner to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application January 30, 1939, Serial No. 253,502

6 Claims. (Cl. 196-10) This invention relates to the treatment of hydrocarbon oils, and refers more particularly to the production of valuable gasolines by synthetically reacting the lighter and vless valuable portions of crude petroleum products and similar hydrocarbon mixtures.- In a more specic sensa' the invention has reference to a process which may be employed to supplement known crude oil treating processes to increase the obtainable yield of high anti-knock fractions suitable for use as fuel in internal combustion engines, or as con- The comparatively recent adoption of high compression ratios in automobile and aviation er1- gines to increase their thermodynamic efficiency placed ademand on .the 'petroleum refining and similar industries to furnish hydrocarbon motor fuels of high anti-knock or slow burning charac' teristics. As a partial attempt to satisfy this requirement the petroleum industry has resorted to the use of cracking operations in which the relatively higher boiling hydrocarbon fractions are fraction, it also contains other petroleum hydrocarbons, including appreciable quantities of olens ranging from ethylene into the normally liquid oleiinic hydrocarbons which have been carried out of the cracking zone by the released gases. `frenerally, in modern renery operations, these hydrocarbon fractions are subjected to a 'treatment With an absorbing medium to recover most if .not all of the entrained normally liquid hydrocarbons. The remaining gaseous fraction contains varying proportions of oleflns of the type of propylene and butylenes, as well as some'saturated hydrocarbons such as methane,

subjected to elevated temperatures and frequently super-atmospheric pressures to cause the decomposition of these hydrocarbons and to produce fractions within the motor fuel boiling range.

However, these cracking operations are not entirely satisfactory both from the'standpoint of yields and the quality of the produced motor fuels. Thus, among other objections, the motor fuels derived from such cracking of petroleum oils or their fractions do not possess the desired high anti-knock characteristics. Nor are these fuels sufficiently susceptibleto the action of substances of the type of tetraethyl lead. -In other words, such lead compounds, when added in quantities within the permissible range, are incapable of raising sufficiently the knock-rating characteristics of the motor fuel fraction thus treated. Furthermore, all cracking processes produce more or less appreciable quantities of normally gaseous hydrocarbons of varying compositions which, if

not utilized, represent Wastednatural resources.

These normallyv gaseous fractions, resulting as a by-prcduct from the cracking of petroleum o ils, contain considerable proportions of oleflns, particularly of the type of propylene and butylenes. In connection with the operations of most modern petroleum refineries, there are several sources of such olefin-containing normally gaseous fractions. One of these is the gaseous fraction produced as the result of releasing the pressure on the petroleum oils which are beingjsubjected to a cracking treatment. Although relatively large percentages of methane are usually present in this ethane, propane and butanes. Another source of -therenery gases is the overhead or reflux fraction obtained from the stabilization of pressure distillate resulting from cracking petroleum oils under pressure. These fractions generally predominate in oleiines of the type of propylene and butylenes, usually containing only very small percentages of methane.' Obviously, the composition of the different. gases will vary considerably depending on the stock subjected to cracking, as well as on the specific cracking and recovery processes employed.

Recently, it has been proposed to produce synthetic motor fuel fractions by contacting isoparaflinic or aromatic hydrocarbons with olens in the presence of a suitable catalyst adapted to produce a chemical combining of these hydrocarbons. The resulting product may be termed a product of alkylation, and may be generally described as consisting of saturated or cyclic hydrocarbon'molecules with hydrocarbon chains or branches attached thereto. The above nomenclature was employed to distinguish this branched chain molecule from a polymer which is a product resulting from the interaction of two or more oleiinic molecules to produce an unsatup rated hydrocarbon molecule having a correspondingly higher molecular weight. i As an exn ample of an alkylation reaction and of the resulting product, reference may be made to the chemical combining of propylene or butylene with isobutane to produce seven or eight carbon atom.

branched chain saturated molecules, respectively.

It has been recently discovered that optimum treatment of isopentane with butylene or propylene may cause the production of excessive quantities of polymers. For this reason it has been generally considered advisable to produce relatively narrow cuts or fractions predominating in a given isoparaffln, and to catalytically alkylate these individual isoparafiinic fractions with the olens to produce optimum yields of products of alkylation. Furthermore, since normal paramns do not react with oleiins unless subjected to decomposing temperatures and pressures, it is adof the isoparaiiin-containing drocarbon fractions.

visable to fractionate the paraiiinic hydrocarbons so as to isolate the particular isoparailin even from its corresponding normal parafiinic hydrocarbon before the isoparainic hydrocarbon fraction is employed in the alkylation reaction. Obviously such procedure necessitates the use of specialequipment for the narrow fractionation of the saturated hydrocarbons, thus greatly increasing the initial and operating costs of an alkylation plant.

As previously stated, products of alkylation are formed by the catalytic interaction of isoparaiiins and olens. Generally, this alkylation is conducted -in a liquid phase, the liquefied isoparailns such as isobutane or isopentane being iirst intimately commingled with the liquefled olefin-containing fraction before the mixture is brought into contact with the alkylating catalyst such as sulfuric acid, a mixture of sulfuric and phosphoric acids or a metal halide catalyst such as aluminum chloride. Since the oleiins are re1- atively highly reactive and tend to form polymers or isoparafnic hy- A further object of the invention is4 to provide an alkylation process for the production of high anti-knock motor vfuel fractions in which process the separate fractionation of the isoparaiiinic hydrocarbon is eliminated.

, A still further object of the'present invention is to conduct the alkylation of isoparailinic hydrocarbons, and preferably the isobutane, isopentane and/or isohexane fractions with normally gaseous oleiins and olefin-containing gases, in a liquid state and in the presence of a catalyst of the type described above, without the necessity of providing means for the expensive compression and liquefaction of the olefin-containing by contacting this liquid medium, and the olens in preference toA their alkylation of the isoparaffins, it is desirable, if not essential,` to maintain an excess of the isoparalnic hydrocarbon fraction, or of the products of alkylation. Although y the isoparaflinic hydrocarbon employed for the production of high anti-knock motor fuels may be obtained from other sources, these isoparaffins, and ,particularly isobutane, isopentane and isohexane, are mainly derived from the stabilization of gasolines extracted from natural gases. Thus, although the fractions employed as reflux for such natural gasoline stabilization are in a liqueed state and predominate. in propane, these fractions may in turn be fractionated to produce an isobutane predominating cut. A comparable material may be produced as a side-cut during stabilization of the natural gasoline. The isopentane and isohexane fractions may be recovered from the fractionation of stabilized natural gasoline. On the other hand, the oleiinic fractions obtained as a by-product from cracking operations are often in a gaseous state so that if the alkylation reaction is to be realized in a liquid state, these olefin-containing gases must be liqueed, thus further adding to the cost of the operations.

It is, therefore, the main object of the present invention to avoid the above diiiiculties and to provide la novel process for obtainingfincrea'sed yields of high anti-knock motor fuel fractions by means of new and, novel cooperation of certain steps to be described more fully hereinbelow. A

l further object of the present invention is to obtain a motor fuel fraction having a high antiknock value and substantially free from products of polymerization by processing a mixture of normally gaseous olefin-containing hydrocarbons derived from petroleum oil conversmn or cracking thus liquefied, with the liquid isoparaiiinic hydrocarbons, at optimum temperatures and in the presence of an alkylating catalyst, such as strong sulfuric acid. The resulting product of alkylation, or some portion or fraction thereof may be used as the absorbing medium. By such operation, the liquid product of alkylation is thus emprocesses, and liquefied saturated normally gase-` ons hydrocarbonstcontaining isoparaiiinic fractions without the necessity of providing special or ,girate equipment for the narrow fractionation -ployed both for thepurpose of absorbing (and thus liquefying) the oleiins, and to dilute, and thus lower the concentration of oleflns in the reaction zone, thereby promoting the alkylation of the introduced isoparamns, with the concurrent inhibition of polymer formation.

It has also been discovered that a considerable saving in initial and operating expenses may be realized by eliminating any special fractionating structures for the recovery of the substantially pure isoparainic fraction, such as isobutane, iso'- pentane or isohexane, vfrom the hydrocarbons containing the same, and by fractionally treating these isoparafiin-containing hydrocarbons `together with the crude products of alkylation revcovered from the catalytic treatment of isoparaflins with oleflns.

It is to be noted that the crude liquid fraction produced as a result of the interaction of an isoparafllnic fraction (such as a hydrocarbon fraction predominating in isobutane) with an olefin-containing hydrocarbon4 fraction, comprises a heterogeneous liq'uid mixture which contains true products of alkylation, relatively large percentages of the isopara'iilnic hydrocarbon being alkylated, and relatively j smaller quantities of other gaseous hydrocarbons which havebeen dissolved inthe liquid product. Furthermore, even the true products of alkylation themselvesrcomprise ar mixture 4of hydrocarbons having different boiling -points resulting from the chemical combining of the isoparailins with the different oleiins entering thereaction zone. In view of this heterogeneous character of the crude product, the separation and recoveryof the desired hydrocarbon fraction boiling within the gasoline range, necessitates a fractionation of the crude reaction product. According to petroleum cracking operations.

' from the specific isoparaiiin, such as isobutane,

in a substantially pure state, this isoparaftinic fraction being recovered as a liquid and utilized asthe feed or starting material for the formation of additional quantities of products of alkylation.

The invention further includes processes in which the above outlined stepsrare 'employed' in combination withother steps such as: the recycling of a portion of the crude products of alkylation to maintain suitable ratios of products of alkylation, isoparalns and oleflns in the reaction zone; recycling of the acid and/or hydrocarbon acid mixture or emulsion to alkylate new quantities of isoparafllns and olens; dehydration of the hydrocarbons prior to their introduction into the reaction zone and into contact with the catalyst such as strong sulfuric acid; and the desulfurization of the olefinic hydrocarbons. The invention further includes an alkylation process of the class describedin which a portion of the products of alkylation, and particularly the heavy fraction boiling above the gasoline boiling range.' may be efliciently em# ployed as the medium for the heating of the various fractionating towers, thus furnishing the heat necessary for the fractionation of the'crude alkylation reaction product and of the isoparanim-containing hydrocarbons.

The invention will be further understood from the following description of an -embodiment of the invention, this description being made with reference to the accompanying drawing which forms a part of the specification and which represents a diagrammatic elevational view of an apparatus suitable for carrying out the ,pres-l ent process.

Referring to the drawing, the olefin-containing normal1y` gaseous hydrocarbon fraction is Since in thefpresent process the alkylation reaction described more fully hereinbelow is conducted in a liquid phase, the oleflnic fraction introduced through line I may be a portion of the condensed reflux fraction obtained during the stabilization of pressure distillate resulting from `In the alternative, the overhead gaseous 'fraction derived during such stabilization of cracked pressure distillate may also be used as the' charging stock. Obviously, such gaseous fractions should bepreliminarily condensed by any suitable and known methods and means. Both the overhead gaseous fraction and the reflux portion thereof contain relatively large quantities of oleiins, the propylene-butylene content of such fractions 'usually exceeding 20%, and in most cases being above 30% or even 35%.

The so-called lean gases resulting from the ordinary absorption treatment of gaseous fractions produced during the release of pressure on the crackedpetroleum product, are also a suitable source for the obtaining of olens which may be employed in the alkylation process. ous fraction, although containing relatively large quantities of methane and ethane, also contains appreciable proportions of olefins of the type of propylene and butylenes which are suitable for use in the process to be described. Thus, these lean gases contain -as much as to 15% of propylene and butylenes. These lean gases may be introduced into the system through line I2,

This gase-,

. charged into the system through conduit I0.-

wherein they are rst cooled as by passage through a chiller I3. This chiller may be eliminated if the gases are available at a suitably low temperature. In order to obtain a liquid olefin-containing fraction, as well as for the purpose of selective extraction of the desirable olefins, these cooled lean gases are then passed into an absorber I4 in which they are brought into contact with a fraction of the products of alkylation. As will be described more fully hereinbelow, the lean oil used vin the present process as the absorbing medium in absorber I4 is the heaviest fraction resulting from the fractiona tionof the products of alkylation.` It is to be understood, however, that other fractions of the products of alkylation, as well as other absorbing media, may be used to extract the desired olefins from the lean gases.

The lean oil to be used in the above described absorption is first cooled in a heat exchanger I6 and-is then'continuously fed through line I1 into absorber I4. The rich oil thus formed (comprising the products of alkylation and the olefincontaining gases absorbed thereby) is Withdrawn through line I8, and, after further cooling in heat exchanger I9, is conveyed through line 20 and into line I0 to be commingled with the first mentioned liquefied olefin-containing gaseous fraction. 'The gases which are not absorbed by the lean oil are removed from the system through line 22 leading from the upper part of absorber I4.

The liquid fraction thus entering the system through line I0 is rst subjected to a desulfurization operation for the removal of the hydrogen sulfide usuallypresent in the olefin-containing normally gaseous hydrocarbons. Although the hydrogen sulde content of such hydrocarbons is relatively small, being in the neighborhood of 0.25%, it has been found that the removal of this sulfide is beneficial and results in better yields of products of alkylation, as well as in greater economy. To effect the removal of the hydrogen sulfide the olefin-containing liquid fraction is conveyed into a vessel 25 wherein it is vbroughtl into contact with an aqueous solution of an alkaline compound having an` ainity for hydrogen sulfide. As an example, vessel 25 may be filled with an aqueous solution of sodium carbonate. The desulfurized hydrocarbons then leave the vessel 25 through line 26, while the sodium carbonate solution containing the absorbed sulfur compound is withdrawn through line 21 and conveyed into the top of a regenerating vessel 28 in'which the foul sodium carbonate is brought in contact with an upward draft of aair introduced through line 3|. The rejuvenated sodium carbonate solution is then withdrawn from the bottom of tank 28 and is returned through line 29, either continuously or intermittently, back into vessel 25 for further desulfurization of the olen-4 containing hydrocarbon fractions. The air contact with such strong sulfuric acid catalyst. A

paraiiins of the 4type of isobutane, isopentane and` isohexane is best realized in the presence of a relatively strong sulfuric acid, for example'sulfuric acid having approximately a 98% H2804 content.- Since any water present will naturally dilute the sulfuric acid catalyst, it is desirable to dehydrate the hydrocarbons prior to their con- Therefore, for the purpose of removing any Water which may be present in the olefin-containing liquid hydrocarbon fraction, the desulfurized fraction leaving vessel through line 26 is conveyed through a drier 34 which may contain any known drying material such as sodium sulfate. Although only one such drying tank is shown in the drawing, it is obvious that a plurality of such tanks may be placed parallel so that any one of the tanks may be isolated for the purpose of regenerating the sodium sulfate or for the purpose through line 55. Obviously, when necessary the neutralized alkali may be withdrawn from the system through line 53, whilev fresh alkali may be introduced into the system through the same or another pipe.

The neutralized hydrocarbon mixture, comprising products of reaction and unreacted isotroduced through line 4I and with used catalyst between the isoparafiins and the oleiins, it isv desirable, if not essential, to maintain an excess of the isoparaftns and of the crude products of alkyation. Obviously, the presence of excess isoparains (such as isobutane) in the hydrocarbon mixture passing through mixer 44 results in the presence of unreacted isoparailins` in the stream being conveyed therefrom through line 46. After passage through cooler 45, this hydrocarbon stream (while in ya state of emulsication or commingled with the sulfuric acid or other catalyst) is divided into two p ortions. One of these is conveyed through lines- 48 and 36 for purposes of recycling while the other is conveyed through line 49 into settler 50. The sulfuric acid settlesl to the bottom of this Vsettler 50 and is withdrawn through line 52. As stated, this acid may be recycled by conveying it through line 42 which leads this acid catalyst to line 4I) wherein it is continuously commingled with fresh'quantities of hydrocarbons to be alkylated. The acid when incapable or uneconomical for alkylation of further quantities of isoparaflins and olens, may be withdrawn through line 53, while, as stated, fresh acid or the like may be introduced into the system throughline 4I.

The supernatant layer, comprising the prodtator 51, and is then passed through line 58 into` another settler 59. Here', the sodium hydroxide deposits itself to -the bottom and may be withdrawn from the bottom through line 60. This vneutralizing agent may then be recycled through lines 62 and 56 for the washing of further quantities of the hydrocarbons being conveyed parains, is continuously withdrawn as the supernatant layer, 'from settler 59, and is conveyed through line 66 to a fractionating system to be described more fully hereinbelow.

' In view of the fact that the alkymtion re- 66 are .first conveyed through heat exchanger 68 in which they are brought into indirect contact with the isoparailinic fraction (such as isobutane) passing through line 84 to dehydrating tank 31 from which the liqueiied cold isoparailins are then conveyed to the alkylating zone` described above.

After passing through heat exchanger 68, the

slightly warmed hydrocarbon mixture is then conveyed through line 69 to a surge tank 10, from which the mixture is conveyed through line 1I, heat exchanger I9, line 12, and heat 'exchanger I6. In the rst of these,- heat exchangers, the hydrocarbon mixture precools the olefin-containing labsorbing medium passing through lines I8 and 20, while in lheat exchanger I6, the products of reaction are heated by the lean absorbing medium fed into absorber I4 through line I1. 'The mixture of preheated reaction products leaving preheater or heat exchanger I6 is conveyed through line 14 into the rst of a series of fractionatingcolumns. However, prior to such introduction into the fractionating system, the crude products of alkalation are rst commingled with an isoparaiiin-containing fraction introduced into the system through line 15. As previously stated, this isoparafn-containing fraction may be a hydrocarbon mixture containing both normal and isomericparailins (such as normal butane, isobutane, etc.), this hydrocarbon mixture being derived either as a side-cut or fraction, or as a reux fraction in the stabilization of natural. or straight run gasolines.

The fractionation of the lsoparafn-containing hydrocarbons and of the products resulting from the alkylation reaction is realized according to the present invention in a plurality of fractionating columns. As shown in the drawing,.the mixture passing through line 14 iirstV enters fractionator 11 which maintained at optimum temperatures and pressures to cause the vaporization of thelightest hydrocarbons of the type of methane, ethane, and propane. The heating of fractionator 11, as well as of the succeeding fractionator, is realized by method and means to be described more fully hereinbelow. The hydrocarbon vapors in fractionator 11 are withdrawn therefrom through line 18. A portion of this overhead fraction is cooled at 19 and the condensate thus formed is returned as reiiux through line 83 back into the upper portion of fractionator 11. The remaining portion of the gaseous overhead fraction may be withdrawn from the system through line 82, while any noncondensed gasesy from cooler 19 may be withdrawn through line 83. The hydrocarbons remaining in the liquid. state in fraction- 'ator 11 are withdrawn from the bottom thereof through line 85 and are conveyed therethrough, to the second fractionator 86. A portion of the bottom fraction thus withdrawn through line 85 is by-passed through 81 and is conveyed through these products of alkylation, the hydrocarbons in fractionator -tionation so as to obtain three cuts. By mainwhich may comprise a hydrocarbon fraction suita heater or reboiler 88 and then returned through line 89 back into fractionator 11 -to provide the above described heat necessary for the vaporiza-l tion of the propane or the lighter gaseous hydrocarbons. The heat for the reboiler 88, as stated nating in or substantially consisting of isobutane.v

For this purpose fractionator 86 is maintained at a desired or optimum temperature or pressure.`

The overhead fraction formed is withdrawn from the top of this fractionator through line 9|, condensed in cooler 92, and a portion returned through line 93 back` into fractionator 86, this liquefied hydrocarbon fraction acting as a refluxing medium. The remaining isobutane fraction condensed at 92 is conveyed through line 94 for use as the isoparaiiinic hydrocarbon fraction to be alkylated. For this purpose, this isobutane fraction is first partially precooled by passingit through the heat exchanger 68 and through tank or drier .31 in which the hydrocarbon fraction is dehydrated as by means ofsodium sulfate or a similar desiccating medium. The dried isobutane, as described above, thus passes through line 39 to lines 36 and 40 wherein it is commingled with crude products of alkylationfolens and the acid catalyst.

The hydrocarbon mixture remaining as a liquid in fractionator 86 is withdrawn from the' bottaining fractionator 98. at optimum temperatures and pressures an overhead fraction is' produced,

able as a fuel for aviationengines. Thus by suitable operation of the fractionator 98 it is possible to obtain an overhead fraction having an end point of about 325 F. which is the end boiling point of aviation gasoline. This overhead fraction is removed from the top of fractom thereof through line 91 and is conveyed to.

the last fractionator 98.. As` in the case of the first fractionator 11, a portion of the bottom fraction withdrawn by 91 from fractionator 86 is by-passed through line 99 and is conveyed ator through line |0I. Instead of by-passing only aportion of the bottom fractions withdrawn from fractionators 11 and 86 through lines 81 and 99 respectively, it is also. possible to convey the whole bottom fractions through their respective reboilers or heaters 88 and |00. In such a case the vaporized portions therefrom in these reboilers may be returned through lines 89 Y and |0I to their respective fractionators for the purpose of providing the necessary heat for fractionation therein. Unvaporized hydrocarbon fractions may then be withdrawn from the reboilers and conveyed -to the succeeding frac-v rtionator 98 through line |05 and ls condensed v A portion of liquefied gasoline. fractions is returned through line |01 back into in cooler |06.

the fractionator and is used therein as a `reflux medium, 'while the remaining aviation gasoline fraction is withdrawn from the system through v line |08. The heavier synthetic gasoline fraction is withdrawn as a middle or side-cut through line |09 and may be condensed in I0. This synthetic productv of alkylation, although having a higher end point than the overhead fraction withdrawn through line |08, also possesses-good anti-knock characteristics and is particularly suitable as a motor fuel for automobiles or as a 'constituent thereof.A 'Ihe residual fraction remaining unvaporized is withdrawn from the bottom of the fractionator 98 through line i2. A portion of this fraction is by-passed through line ||3, precooled in heat exchanger |6 and is used as the'absorbing medium in absorber I4. Of the remaining residual fraction withdrawn from fractionator 98, a portionis by-passed through line H4 for use as the heating medium for the fractionating system. For this purpose it is conveyed through said line III to a heater ||5 wherein it is raised to anoptimum or desired temperature. This heated hydrocarbon fraction is then conveyed through line ||6 and is employed for heating reboilers 88 and |00 and to provide heat in fractionator 98. For this purpose line ||6 communicates with branch lines spectively, the balancevof the heated hydrocarthrough heater |00 and back into the fractioninto the bottom portion of fractionator 98. After passingthrough reboilers 98 and |00 the heating medium is returned through lines |22 and |23 respectively back into line H4 leading to heater H5.' The net excess heavy products of alkylation withdrawn through line ||2 are removed from .the system through line |24, provided with a valve |25. X

As indicated above. the description of the lprocess is simply illustrative o1' the invention and is subject to many modifications by those skilled in the art. Thus, although the use oi lysts.

tem to be used for various purposessuch as i stabilization of pressure Adistillate or natural gasoline, or it may be subjected to isomerization to form additional quantities of isobutane, thus .in-

creasing the potential yield of products of alkylation. The liquid hydrocarbon fraction introduced through line 91 into the last fractionator 98 predominates in products of alkylation. However, in viewy of the relatively wide boiling range oi 98% and strong sulfuric acid is above indicated it is obvious that the process may be realized while employing other'alkylating catatween about 94% and 100% H2804 content may be employed. Also the catalyst vmayconsist of a mixture of sulfuric and phosphoric acids or may compriseor. include chlorosulfonic acid or certain metallic halide-complexes such as aluminum chloride or boron triuoride or catalysts consisting of the above acids in combination with certain metallic salts such as phosphates, -sulfates, chlorides, nitrates and acetates ofthe type of cadmium, zinc, silver, mercury, copper and barium may be used. Thesesalts act as vactivators to promote the alkylation reaction in preference tol the polymerization of the oleflns.

98 may be subjected to a frac- Generally speaking,'sulfuric acid of be-y ploying 'said alkylation products tion with the recycling ofaportion ofthe hydro-f carbon acid mixture through lines and 48, it is possible to recycle a portion of the crude prod-y uctsof alkylation fromline-il back intoline Il,"

' lutejthe'olefins and maintain alproper ratio between the products lof alkylation,"isoparailins and liquid mixture containing the absorbedl oleilns,

oleilns. Such a `procedure would eliminate any extensive contact between the crude products o! alkylation andthe acid. Furthermore, instead oi' employing both the oleiln-containing fractionv lyst, thereby forming reaction products compris-A ing said 'branched chain saturated hydrocarbons, l

derived from the stabilization of pressure distillate and' that obtained from the reduction ofi pressure inthe cracking stills, it is possible to use either of these fractions or any other olencontaining fraction, vespeciallyuif it is lrichin the desirable propylene and butylenes. Furthermore,

accesos. Although the process isdescribed' in connecgasoline range wherein" 'isoparamnic hydrocarbons arek reacted with normally gaseous oleiinic hydrocarbons inlfthe presence oan alkyiating catalyst, theysteps o! v contacting the gaseous oleiins "with a 'hydrocarbon liquid absorbing medium oriorto ooniaot with said isoparamnf and alkylating catalyst, thereby -producing a 'commingling said mixture withliqueiied iso' oaramnsio be alkyiotedfand the aikylaung oatsseparating the alkylation'products from the alkylating catalyst, fractionally distilling the -said tion anda fraction containing hydrocarbons boil-'f v ing above the gasoline boiling range and,1 employ-l 1 ing said fraction'containing. hydrocarbons boilthe absorption oi' the olens li'rom the 'gases en- "1 tering through I2 'may be realized by any other absorbing medium or by a portion of the products i of alkylation as formed according to of the present invention.'

The. heating of the reboilers may be realized the process byv employing hydrocarbon fractions other 'than the heavy reaction products removed from the parafllns are caused to react in the presence oi bottoni of ,fractionatorv ll. Furthermore, other'v heating media such as steamV may 4be employed for this-purpose. Still further incarryingvout the invention the conditions oi! operation chosen with respect to temperature, proportion of reacting-l constituents, choiceso'i' catalysts, and temperatures andv pressuresl inthe fractionating system Vmay be varied within a relatively large Vrange to suit the individual case. Therefore, the above disclosure is merely illustrative and 'is not to be taken as limiting since many variations may be possible within the'scope oi the pending claims.- q a i I claim:

l. In a process for the production' 'of branched" chain saturated hydrocarbons'boiling within :thel

gasoline range wherein isoparamnic hydrocarbons are reacted with'normally gaseous oleflnic hydrocarbons in the presence of an alkylatirxg u catalyst, the steps o! contacting the gaseous oletlnswith a hydrocarbon liquid absorbing medium i' prior to contact with said isoparaillnand 'alkyling above the gasoline boiling range as said hydrocarbon liquid absorbing medium.

v4. In a process for the production of branched chain hydrocarbons wherein oleilns and isoa sulphuric acid catalyst, the steps of continuously recycling a mixture oi isoparailins, products oi' reaction and the acid in a closed system, con- -V tinuously contacting gaseous oleilns with a liquid absorbing medium, continuously introducing into said system gaseous oleilns dissolved in said liquid absorbing medium and isoparaiilns to be reacted,

i. continuously withdrawing from said system Ia ating catalyst thereby producing a liquid mixture said mixture with liquefied. iscp'arailns to 'be al, kylated and withthe alkylating catalyst thereby forming alkylation products, comprising said branched chain saturated hydrocarbons and emabsorbing medium.- l 2. In a process for the production of'branched chain saturated hydrocarbons boiling within the gasoline range wherein isoparailinic hydrocarbons are reacted with normally gaseousjolenic w' hydrocarbons in the presence o! an alkylating catalyst, the steps' oi' contacting the gaseousl `oleilns with a hydrocarbon` liquid absorbing ing said branched chain saturated hydrocarbons, 70

separating said reaction products into fractions and employing one of said` fractions as the said absorbing medium.y f

. 3. In a process for the production of branchedv chain saturated hydrocarbons boiling within the l oontainmg. the absorbed olenos. oommmgung .o

as said liquid 55 portion of Ithe hydrocarbon-acid mixture, vcontinuously settling,l said .withdrawn mixture thereby obtaining al hydrocarbon phase containing the products of alkylaaomreeotioo and an acid phase, 7 separatingy said phases, returning the acid phase A intorthe closed reaction system for the alkylation oi lfresh quantities of isoparaillns and oleilns introduced .thereinand employing a portion oi the products o! alkylation as, said liquid absorb# ing medium. 5. A continuous process for the alkylation of isoparailinic hydrocarbons having less than seven carbon atomspermolecule with normally gaseous oleilns to producebranched chain saturated hy-v dro'carbons boiling within the gasoline range,

v having highanti-detonating characteristics and substantially free from products of polymerization, which'comprises'continuously contacting the normally gaseous oleilns with a liquid hydrocarbon absorbing medium to produce a liquid mixture containing the absorbed oleflns, continuously introducing said liquid mixture and a substantially pure isoparaillnic hydrocarbon fraction boiling within a relatively narrow boiling range and maintained in a liquid state into a reaction zone, continuously introducing strong sulphuric acidinto said zone to cause the interaction between th'e isoparaiilns and the oleilns to form products of alkylation, .continuously recyclinglsaid hydrocarbon-acid mixture through said re,-

action zone, continuously withdrawing a portion oi' said mixture from the reaction zone, continu'- ously separating said withdrawn mixture into an acid phase and a hydrocarbon phase containing the products oi' reaction and the unreacted isoparaillns, separately withdrawing said phases; commingling the hydrocarbon phase with aniso# paraiiin-containinghydrocarbon fraction, continuously conveying said mixture through av fractionating zone to recover therefrom the desired branched chain hydrocarbon fraction and a liqueed, substantially pure isoparainnic hydrocarbon fraction having a relatively narrow boiling range, returning said last mentioned hydrocara1ky1ation products mtoasynthouo gasoline fraoo bon fraction as the feed stock for the production of new quantities .of branched chain hydrocarbons, wherein a fraction of the products of reaction comprises the absorbing medium for the gaseous oleflns.

6. A continuous process for the alkylation of isoparaflinic hydrocarbons having less than seven carbon atoms per molecule lwith normally gaseous olens to produce branched chain saturated hydrocarbons boiling within the gasoline range, having high anti-detonating characteristics and substantially free from products of polymerization, which comprises continuously contacting the normally gaseous'olens with'aliquid hydrocarbon absorbing medium to produce a liquid mixture containing the absorbed oleflns, continuously introducing said liquid mixture. and a substantially pure isoparaiilnic hydrocarbon fracvv tion boiling Within a relatively narrow boiling range and maintained in a liquid state into a reaction zone, continuously introducing strong :r-ulphuric acid into said zone to cause the interaction between theisoparallins and the olens A:o form products of alkylation, continuously recycling said hydrocarbon-acid mixture through said reaction zone, continuously withdrawing a portion of said mixture fromthe reaction zone,

continuously separating saidv withdrawn mixture intoan acid phase and a hydrocarbon phase tion boiling above the gasoline boiling point range l and a substantially pure isoparailinic hydrocarbon fraction having a relatively narrow vboiling range, returning the said isoparailinic fraction having the relatively narrow boiling point range as the feed stock for the production` of newquantitiesV of branched chain hydrocarbons and employing said heavy -alkylated 'hydrocarbon fraction as the said liquid absorbing medium.

FARRAND D. PARKER-

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