US2435028A

US2435028A - Alkylation process

Info

Publication number: US2435028A
Application number: US218772A
Authority: US
Inventors: William E Bradley
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1938-07-12
Filing date: 1938-07-12
Publication date: 1948-01-27
Anticipated expiration: 1965-01-27

Description

Jan. 27, 194. W. E. BRADLEY 435m ALKYLATION PROCESS y Filed July l2, 1938 `SETTLE/Q.

SEEE@ l u 23T /soum/VE OLEF/A/ 0mm/5r ALM/LATE@ l L? 3 HYDRO CA E50/V lsopAeAFf/N 5026: TAN/fl ,66

S11/ESEn A TANK /39 l' INVENTOR WzIZzam E. Bra dley Y. M l

50'; U ATTORNEY.

Patented Jan. 27, 1948 UNITED STATES PATENT oFFlcE ALKYLATION PROCESS William E. Bradley, Los Angeles, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application July 12, 1938, Serial No. 218,772

14 Claims. 1

The present invention relates to the synthesis of hydrocarbons, and more particularly pertains to the manufacture of hydrocarbons having branched chain structures and which are especially suitable as automobile and aviation engine fuels or constituents thereof.

More specifically, the invention covers a process for reacting certain isoparafnic hydrocarbons witholens to produce branched chain parailnic hydrocarbons boiling within the gasoline range, possessing high -anti-detonating characteristics, and substantially free from products of polymerization boiling within such gasoline range. In one of its embodiments, the present invention includes a continuous process for the combining of isoparainic hydrocarbons of relatively low molecular weights with olefins, which may be normally gaseous or normally liquid, or both, to produce the above described branched chain parainic hydrocarbons.

Owing to the adoption of high compression ratio in automobile and aviation engines, an insistent demand has been made upon the petroleum refining and similar industries to furnish motor fuels which have high anti-knock values. Thus in the aviation industry many specications require the gasoline to have a knock rating of about 100 iso-octane, as determined by the A. S. T. M. method, this gasoline to contain not more than 3 millimeters of tetraethyl lead per gallon. Also, in the case of aviation fuels, it has been considered advisable to. limit the percentages of oleflnic and aromatic bodies which may be present, consequently and indirectly requiring fuels consisting essentially of branched chain paraflins, it being known that the normal or straight chain parainic hydrocarbons boiling within the gasoline range have low octane ratings.

As a result of this requirement for gasolines of the branched chain type having high antiknock values, it has been recently discovered that the relatively low molecular weight isoparafns, such as isobutane and isopentane, may be Chemcally combined with olefins to produce the desired branched chain hydrocarbons boiling within the gasoline range and possessing the required high anti-detonating characteristics. Such reactions are termed alkylation in order to distinguish them from polymerization reactions, which consist in the combining of two or more olelinic molecules to form an olefin of proportionately higher molecular weight. It has also been previously discovered that such alkylation reactions between isoparafns and olefins may be effected catalyticallyandat atmospheric or elevated pressures and at atmospheric or even subatmospheric temperatures. It has been further discovered that substances of the type of sulfuric acid, mixtures of sulfuric and phosphoric acids, chlorosulfonic acid and certain complexes of aluminum chloride and boron trifluoride may be eiectively employed as the catalyst for such chemical combining of isoparaiiins with olens to produce the described branched chain paramnic hydrocarbons boiling within the gasoline range and having high anti-detonating characteristics and being substantially free from products of polymerization boiling within the gasoline range.

In carrying out these catalytic alkylation processes, the reactions usually have been eected by commingling the oleflns with a small excess of isoparaflins and subsequently contacting the mixture with the catalytic material. Although this method of operation resulted in the formation of alkylate, i. c. products resulting from the interaction of isopara'ins with olefins, it has heretofore been impossible to prevent a certain amount amount of polymerization of the olens which usually occurred simultaneously with the alkylation reaction since the catalysts for the alkylation reaction are likewise catalysts for the polymerization of olens.

y It is, therefore, the main object of the present invention to provide a process for the alkylation of isoparains with olefins to produce branched chain parainic hydrocarbons of the class described, these products 0f reaction being substantially free from products of polymerization of the olens. It is a further object of the invention to provide a process for reacting isoparains with olefins insubstantially the liquid phase, at ordinary or elevated pressures and at atmospheric or sub-atmospheric temperatures, in the presence of an alkylating catalyst under conditions whereby the products of reaction comprise branched chain paraffinic hydrocarbons boiling within the gasoline range and substantially free from products of polymerization.

It has now been discovered that the above and other objects may be attained by dissolving the olei'lns in an inert diluent in order to form a relatively dilute solution of the olens thus introduced, and subsequently causing the alkylation of isoparains by the thus prediluted olens. It has been further discovered that the reaction product formed by the chemical combination of olefins and isoparailins, and therefore consisting essentially of branched chain hydrocarbons, may be employed as the above mentioned diluent for the olefns .to be used in the alkylation reaction.

chain hydrocarbons is so slow in comparison with 5 the rate of alkylation of the low molecular weight isoparafiins, particularly if the latter arein excess, that the former reaction does not occur to any measurable extent.

It has been still further discovered that theY l0 above and other objects may be attained by providing a continuous or semi-continuous process" l in which at least a portion. of the lproducts of alkylation is continuously or otherwise. withdrawn from the reaction zone and commingled with new steps of pre-diluting the olens with the prod- 1 ufcts which have previously passed through the quantities of the olens or isoparalns prior to the introduction of these hydrocarbons into the reaction zone. As will be brought out `more fully hereinbelow, the portion of the alkylate used as the diluent may be commingled with new quantities of isoparafns and olenns'before 'the mixture is contacted with the catalyst. In'the alternative, this alkylate fraction may Vrst be commingled with the olens (for purposes of their dilution) and the mixture thus produced may then be contacted and thoroughly mixed with the isoparaihns and the catalyst. i

As previously stated, both polymerization and alkylation are competing reactions; In other words, catalysts employed in alkylation reactions also aid the polymerization of olens. Therefore, the mere dilution of olens in the complete absence of isoparains would not decrease the polymerization reaction when such diluted lefns are brought in contact with catalysts of the type V3`5 of sulfuric acid, mixtures of sulfuric acid and phosphoric acid and chlorosulfonic acid, etc. It has been still further discovered that the alkylation of the relatively low Ymolecular weight isoparaiiinic hydrocarbons with normally gaseous 40 or normally liquid oleiins to produce high yields of branched chain hydrocarbons boiling within the gasoline boiling range and having highV antidetonating characteristics may be realized by recycling the products leaving4 the sphere of reac- 5 tion and simultaneously introducing the isoparans in excess of the quantity theoretically necessary for the combining with the olefns being added. VSuch. continuous dilution of the oleflns with the products of alkylation and the simultaneous introduction of the excess quantities of isoparanns into the sphere of reaction greatly decreases any possibility of polymerization of the olens and simultaneously increases the chances of the olefins coming in contact with the isoparan molecules tobe alkylated. Therefore, the products resulting from such procedure comprises alkylate which are substantially free from any products of polymerization, these alkylate having high anti-'detonatting characteris- 60 tics and boiling substantially within the gasoline range. 4

The invention may, therefore, be stated to reside broadly in a process of interacting relatively low molecular weight isoparafns with normally liquid or normally gaseous olens or with both types of olens to produce branched chain parailinic hydrocarbons boiling within the gasoline range possessing high anti-detonating characteristics and substantially free from products sequent commingling `of said mixture wil-,h the 75 alkylation catalyst. The invention further resides in the process of reacting isoparaiins with olens to produce motor fuel fractions which comprises continuously withdrawing a portion of the products of alkylation with olens being introduced into the sphere of reaction, continuously introducing isoparaflins in excess of the quantity theoretically necessary for the combining of the olens introduced and contacting said mixture at optimum temperatures and pressures with the alkylating catalyst.

In its most specific embodiment, the invention resides in a continuous process of alkylating low molecular weight isoparafns with the above described olens. A This process comprising the alkylation reaction zone, and bringing this mixture in intimate contact with isoparanins and the alkylating catalyst, the isoparains being employed in quantities in excess of those theoretically necessary for the combining with the introduced oleiins. v

More specifically stated, the process includes the steps of continuously commingling excess quantities of isoparalins with olens and a portion of the alkylate fraction removed from the sphere of reaction, commingling said mixture with the alkylating catalyst, introducing the hydrocarbon-catalyst mixture into a settling Zone thereby effecting at least a partialseparation between the catalyst and the hydrocarbons, withdrawing the catalyst for further commingling with new quantities Aof hydrocarbons to be treated, simultaneously withdrawing the products of reaction from said settling chamber and :employing a portion of said products for commingling with and dilution of new quantities of olens introduced into the reaction zone. The invention also includes the maintenance of optimum pressures and temperatures, these conditions of operation varying with the hydrocarbon treated, the catalyst employed, etc.

As an alternative, the process includes the separate dilutionV of the olens with the alkylate withdrawnrfrom -the Vsettling chamber rand the commingling of this mixture with another mixture comprising the catalyst and isoparafns to be alkylated, these lsoparaiins, as stated before, being employed in quantities inV excess of those theoretically necessary'for chemical combination with the olens introduced.'V

For a better understanding' of the various phases of the present invention, reference is made to the vaccompanying drawings in which:

Figure 1 is a diagrammatic 'elevational view of an embodiment rin which the recycled portion of the alkylate is commingled vwith the hydrocarbons to be 'treated prior lto the contact of this mixture with the alkylating catalyst; and

Figurer2 shows in diagrammatic elevation a modied sketchof an apparatus in which the recycled alkylate are continuously commingled with fresh quantities of olens, followed by the commingling of this mixture with another mixture containing the catalyst and the isoparafns to be alkylated. Y

Referring now to the drawing, and particularly tc Figure 1 thereof, there is shown a reaction chamber lo which consists of' two superimposed sections I l and l2. The upper section Il may be termed the settling chamber, while the lower section I2, whichisshown to have a relatively smaller diameter, is'the acid or catalyst chamber. The upper end of chamber II is provided with a discharge pipe I3, a branch line I4 extending from this pipe I3 to a pump I6. The discharge end of the pump opens into a line I'I which is provided with inlet lines I8 and I9 for the introduction of fresh quantities of isoparafnc and olenic hydrocarbons, respectively. Line II may also be provided with a cooler 2 I, the purpose of which will be discussed more fully hereinbelow. A mixer or similar commingling device 23 is attached to the discharge end of line I1, line 24 leading from the lower end of catalyst chamber I2 also opening into this mixer 23. A pipe 23 communicates the discharge end of mixer 23 with the lower portion of settling Chamb-er II. For purposes of discharging the contents of reaction chamber IU as well as for the purpose of adding fresh quantities of catalyst, pipe 24 may be provided with a branch line 21 equipped with a valve 28.

The operation of the above described structure is as follows, it being assumed that sulfuric acid is employed as the alkylating catalyst and that an isoparafn fraction predominating in isobutane is to be alkylated. Before initiating the alkylation, reaction chamber I2 is filled with the sulfuric acid catalyst, which is preferably of a concentration between about 96 and 100% sulfuric acid. The space above the acid is then filled with alkylate from a previous run or, preferably, with the isoparain fraction to be alkylated. Thereafter, pump I6 is caused to operate and simultaneously fresh quantities of isoparafns and olefins are introduced into the system through lines I8 and I9, respectively. The mixture passes through cooler 2l wherein it is brought to the optimum temperature which in this case is in the neighborhood of 40 F.'to 70 F., it being understood that specific temperature limitations presented herein are given only as an illustration and not for the purpose of limiting the invention. The isoparaffin-olen mixture is thus conveyed through mixer 23 wherein it is caused to be thoroughly and intimately commingled with the acid withdrawn from chamber l2 through line 28. The hydrocarbon-acid mixture is then conveyed through line 26 to settling chamber II in which the separation of the acid from the hydrocarbon rst occurs, the acid dropping down into chamber I2 while the hydrocarbon phase passes upwardly in chamber II. The alkylation reaction occurs in mixer 23, line 26 and in the reaction chamber I0. Since the reaction chamber is completely filled with the hydrocarbon-acid mixture, and since both the isoparafns and the olens are maintained in a liquid phase in the system, the hydrocarbon phase passes continuously out of reaction chamber I0 into line I 3. The rate of this discharge is proportional to the rate of introduction of fresh quantities of isoparaiins and olens through lines I8 and I8, respectively. A portion of the hydrocarbon phase, equivalent to the olen and isoparaiiin added through lines I'8 and I9, is withdrawn from the system through line I3, the balance being recycled through line I 4, pump I6 and line I'I for further commingling with new quantities of isoparains and olens.

It is thus seen that the operations according to the invention described above permit a constant dilution of the olens introduced, this dilution being caused by the commingling of the oleiins with the products of reaction continuously removed from settling chamber II through lines I3 and I4. Although it is possible to introduce the isoparains through line I8 in quantities only 6. suflicient vto react with ythe olens continuously introduced through line I9, it is preferable to employ a relatively large excess of isoparaiiins thus further aiding in preventing the polymerization of the olens. Obviously, the constant presence of isoparains (which in the instant case comprises a fraction predominating in isobutane) causes a presence of such isoparaiiins in the hydrocarbons removed through line I3. Therefore, the fraction thus withdrawn out of the system through line I3 comprises alkylate and unreacted isoparafns. The latter may be easily separated from the alkylate as by fractionation and may be returned into the system through line Although the alkylation reaction between the isoparafns of the type of isobutane, isopentane and isohexane and the normally gaseous or normally liquid olefins is not sufficiently exothermic to cause any marked temperature rise in the system, nevertheless, the operations of the above system cause a gradual heating of the hydrocarbons being treated. This heating may be either due to the mechanical energy introduced into the pumps or may be caused by heat evolved by the oxidation of some of the hydrocarbons by the sulfuric acid. Obviously, this heating may be due to other causes which are unknown at the present time. Whatever may be the cause of such heating, the alkylation of the above isoparains by the olens in the liquid phase and in the presence of the sulfuric acid catalyst should preferably be realized at relatively low temperatures of the order of 40 F. to 70 F. It is for this purpose that line I1 is provided with cooler 2l'.

The assembly shown in Figure 2 is somewhat similar to that described hereinabove. Thus, reaction chamber I consists of the superimposed settling chamber Il and acid chamber l2, the acid being withdrawn from the bottom through line 24 while the products of reaction leave at the top through line I3. As in the previous case, a portion of the hydrocarbon phase thus withdrawn is recycled through pump I3 and through lines i4 and I'I. The main difference resides in the fact that only the olefins are commingled with the alkylate fraction thus circulated, this olefin fraction being introduced through line I9. The fresh quantities of isoparaiiins (which, as described, may be employed in quantities in excess of those theoretically necessary to combine with the oleiins) are commingled with the acid catalyst, this mixture being then conveyed to mixer 23 wherein it is intimately commingled with the olefin-alkylate mixture coming through line II. The mass thus produced then passes through line 26 into the reaction chamber I0 wherein it separates as described in connection with the operations of the process shown in Figure 1. Thus, the main difference between the two process and assemblies resides in the fact that whereas in the first process both the isoparafns and olens are commingled with the alkylate fraction before coming in contact with the catalyst, in the second process the isoparaflins are activated by the catalyst before the diluted olefins are introduced into the mixture.

Figure 3 shows a diagrammatic flow sheet of a multi-stage alkylation system according to the process of the present invention. In this case the isoparaflinic fraction, such as isobutane, is stored in tank 30, the isobutane being preferably maintained under pressure and in a liquid state. This liqueed fraction is continuously fed through line 3| into a mixing device 32, such as a centrifugal 7 mixing pump. Thek catalyst, .-such'as sulfuric acid, is introduced .into line 3l through line y34.V catalyst is withdrawn from thexnext succeeding reaction stage'as will be :more fully .explained hereinbelow. The com-mingled isoparailin-cata- -lyst mixture then .passes continuously through line 36 into which the olenic fraction is fed from tank .3'1 through

lines

38 and 39. This oleilnic `fraction is diluted with the product .of alkylation rintroduced through line lll) Vinto line '39 from the surge back f4l. The mixture of the diluted .olehns and isoparaiinsand catalyst is then conveyed .continuously `through line 43 into a mixer 44 wherein it is .actively commingled. The fmass'is then passed through line 45 into a settling chamber 46 wherein the hydrocarbon irst Aseparates as the supernatant layer, the catalyst settling in the bottom being withdrawn through line 41. 'If desired a portion of this catalyst may be re.- -turned via 49 to be commingled with fresh quantities of isoparainic fraction conveyed through line 3l into mixer 32. The residual spent catalyst may be withdrawn from the system through line 50. The hydrocarbon phase from chamber 46 passes through line l into the aforementioned surge tank 4l. As stated, a fraction of this al kylated hydrocarbon is continuously withdrawn through line 40 lfor the purpose of diluting the olens passing Vthrough line 39 into the reaction zone. The remaining fraction which .contains the branched chain alkylated hydrocarbons, the unreacted isoparafflns and the paralnic hydrocarbons, which will be contained in the isoparaflinic and olefinic fractions thus treated, is removed from this rst reaction stage through line 52 to be conveyed through the second reaction stage. This hydrocarbon fraction is commingled with optimum quantities of fresh catalyst withdrawn from tank 53 through line 55, the mixture passing through line 55 and through the mixer 56, similar to the above described mixing device 32. Simultaneously and coincidentally a portion of the oleiinic fraction is withdrawn from line 38 through line 59 and diluted with the alkylate fraction contained in surge vtank 60, this alkylate fraction being withdrawn from said tank 60 through line 6I. The thus diluted olens then pass through line 62 into line 6d wherein it meets the isoparaiin-catalyst mixture from mixer 56. The mass then passes through a second mixing device 65 for the purpose of additional and intimate commingling. As inthe Viirst stage the mixture thus produced is then conveyed through line 66 into settling chamber 68. The catalyst settling to the bottom of this chamber is Withdrawn through line 69. If desired, a portionof this catalyst may be recycled by conveying it through line into line 55. The remainder of the partially .spent catalyst passing through line 34 for the alkylation of new quantities of isoparafns conveyed into the system through line 3|. The alkylate fraction is removed from the top of settler B8 through line 12. 'This hydrocarbon fraction is then conveyed into the above described surge tank 60 from which a portion of the a1.- kylate fraction may bewithdrawn from the system through line 'i3 for .purposes of further treatment if found necessary,

It is thus seen that the multi-stage system described hereinabove is of the type shown in 'Figure 2. That is, a system in which the olens are diluted with alkylate and then commingle'd'with the isoparaliin-catalyst mixture. Itis, however, obvious that it is possible to Ymodify this system so that the isopara'ins and olehs are 'diluted 8. with the fallrylate fraction before they comeyiin contact with thecatalyst. In :other words. the Process shown :in Figure 1 and described hereinabove, may( be :similarly employed for multi,- stage alkylation.

The term isoparaiiins nr isoparainic hydrocarbons as employed -i-n the present specication and4 claims relates- -to the lower members of the series. and particularly to isobutane, isopentane and isohex-ane.V It has been discovered that the rates `of--alkylation Yof these isoparan-ic hydrocarbons maintaining `other' conditions equal are not the same. Thus, the rate alkylate formation when Visopentane `is used is considerably slower than vthe alkylaton'rate of iSObutane, while the rate of alkylation'of isohexane Ais even -still lower. As `to the -terms olens and olenic hydrocarbons, -they relate herein to 'both :the normally gaseous olens and the normally liquid olens. It is to be understood that although some .catalysts may not cause the alkylationof Visoparaflins with ethylenes, the process described and claimed herein includes the use of catalysts .and of conditions of operation which favor alkylation with this olen. It is also to be noted that it is not desirable to employ very high boiling olens since the alkylation reactions become .unfavorable when such olens are used. Thus, it is preferable, although not Yabsolutely essential, to employ olenic fractions having not more than vabout 12 carbon atoms vper molecule.

`It is to be understood that the reference to .isoparanic and olenic hydrocarbons includes the use of these hydrocarbons individually or in mixtures with other hydrocarbons of the same class, as well as mixturesthereof with other hydrocarbons. Therefore, the reference to olenic hydrocarbons includes hydrocarbon fractions, such as hydrocarbon gases derived from cracking operations and which contain the reactive oleins. Y Y

Although the invention is described herein in connection with two preferred embodiments, it is obvious that a number of modications and rearrangements may be made without departing from the scope of the invention. For example, in some cases and under some circumstances, it may be desirable to eliminate the recirculation of .the catalyst, In such acase, the catalyst may be .continuously withdrawn from chamber I2 through line 27, and new Vcatalyst introduced into mixer 23 through line 24. VOr it may be advantageous .to introduce and commingle the catalyst with `the hydrocarbons immediately before the introduction of the mixture into the reaction cham- Vber IU. Also, gravity separation of the acid and hydrocarbon phases in chamber IB may not be found, to be suiciently rapid, in which case, it maybe desirable to employ separators, such as centrifugal separators, in conjunction with or in lieu of chambers H and l2.

Although the `above description was made in `connection with'the alkylation of the isoparains with olens in the presence of a sulfuric .acid catalyst, it is obvious that the process is not limited to Va particular catalyst and that other catalysts which favor -alkylation of isoparafns may be employed. Thus, the catalyst may consist of a mixture of sulfuric and phosphoric acids, or may comprise chlorosulfonic acid or .certain complexes -of aluminum chloride or boron trifluoride. Again, the Vcatalyst may consist of the above acids in :combination with certain metallic salts, such as phosphates sulfatos, chlorides. nitrates, and ace- Atetes of metals of thetype of cadmium, zinc, silver, mercury, copper, barium, etc, Similarly, it may be advisable to employ certain agents which will remove any water present or formed in situ, it being understood that the presence of water is undesirable, particularly when the acid catalysts are employed.

It is to be understood that the process is not limited to the chemical union of oleflns and isoparaiiins, but includes the alkylation of other hydrocarbons, such as aromatics. Also, the invention covers the cracking alkylation of aromatics and isoparaiins, this reaction including the step of reacting olenic molecules with isoparafnic or aromatic molecules to produce branched chain molecules having a molecular weight less than that which would be obtained if the reaction were of the simple addition type.

Although the invention has been described in connection with the description of certain preferred embodiments, it is to be understood that there is no intention to be limited thereby, the invention being co-extensive with the scope of the appended claims.

I claim:

1. In a process for the alkylation of an lsoparafn with an olefin in the presence of an alkylation catalyst, wherein the isoparaiiln and the olen are continuously fed to the alkylation system and contacted therein with the catalyst under alkylating conditions to produce alkylation reaction products, and the reaction products are settled to separate a catalyst phase from an alkylate phase containing a high proportion of isoparan, the improvement which comprises prediluting the olen feed to the alkylation system with separated alkylate containing a high proportion of isoparaiiin prior to contacting the said olefin with the catalyst and precontacting the isoparaiin feed with alkylation catalyst prior to contacting the prediluted olen with the resulting isoparailincatalyst mixture.

2. A process according to claim 1 in which the isoparaiin is isobutane.

3. A process according to claim 1 in which the catalyst is sulfuric acid.

4. A process according to claim 1 in which the isoparafn comprises isobutane, the olen comprises butylenes and the catalyst comprises sulfuric acid.

5. In a process for the alkylation of an isoparafn with an olen, wherein the isoparain and an alkylation catalyst are passed serially through a multiple stage reaction system, each stage comprising a mixing zone and a cooperating settling zone, and wherein the oleiin is introduced in portions into a plurality of said stages to react with the isoparafn in the presence of the catalyst in the mixing zones to produce alkylation reaction products which separate in the cooperating settling Zones into catalyst layers and alkylate layers containing a high proportion of isoparains, the improvement which comprises introducing at least one of said portions of olen into a portion of an alkylate layer from one of the settling zones of said plurality of stages to predilute the olen with alkyate containing a high proportion of isol0 paralns prior to bringing the olen into contact with catalyst,

6. A process according to claim 5 in which the isoparafn is isobutane.

'7. A process according to claim 5 in which the catalyst is sulfuric acid.

8. A process according to claim 5 in which the isoparafiin comprises isobutane, the olen comprises butylenes and the catalyst comprises sulfuric acid.

9. A process according to claim 5 in which a portion of the catalyst layer separated in the settling zone of each stage is recirculated to the mixing zone of the same stage.

10. In a process for the alkylation of an isoparaiiin with an olen, wherein the isoparaiiin and an alkylation catalyst are passed serially through a multiple stage reaction system, each stage comprising a mixing zone and a cooperating settling zone, and wherein the olefin is introduced in portions into a plurality of said stages to react with the isoparaiiin in the presence of the catalyst in the mixing zones to produce alkylation reaction products which separate in the cooperating settling zones into catalyst layers and alkylate layers containing a high proportion of isoparains, the improvement which comprises introducing the olen into a portion of the alkylate layer removed from the settling zone of each of said plurality of stages to predilute the olefin with alkyl; ate containing a high proportion of isoparains prior to bringing the olefin into contact with catalyst in the mixing zone of the same stage.

11. A process according to claim 10 in which the isoparafn is isobutane.

12. A process according to claim 10 in which the catalyst is strong sulfuric acid of alkylating strength,

13. A process according to claim 10, in which the flow of catalyst and isoparafiins through said multiple stage reaction system is countercurrent.

14. A process according to claim l0, in which another portion of the alkylate layer from one of the settling zones is contacted with catalyst from the next succeeding zone prior to contacting the prediluted oleiin being fed to the next succeeding stage with the resulting alkyate-catalyst mixture.

' WILLIAM E. BRADLEY.

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

UNITED STATES PATENTS Certificate of Correction Patent No. 2,435,028; January 27, 1948.

WILLIAME. BRADLEY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 2, line 23, strike out the Word amount second occurrence; column 3, line 60, for anti-detonatting read anti-dctonatng; column 4, line 5, after the Word alkylation insert from the reaction zone, commingling said products of alici/lation; column 5, line 69, for permit read permits; column 7, line 11, for surge back 41 read surge tank 41 column 8, line 13, after the Word rate insert of and that the said Letters Patent should be read with glese mgl-lotions therein that the same may conform to the record of the case in the atent ce.

Signed and sealed this 20th day of April, A. D.I 1948.

THOMAS F. MURPHY,

Assistant ommz'asz'oner of Patents.