US2256615A

US2256615A - Alkylation process

Info

Publication number: US2256615A
Application number: US358204A
Authority: US
Inventors: Hederhorst Fred
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1940-09-25
Filing date: 1940-09-25
Publication date: 1941-09-23
Anticipated expiration: 1958-09-23

Description

Sept. 23, 1941.

ALKYLATION PROCESS Filed Sept. 25, 1940 F. HEDERHoRsT 2,256,615

Patented Sept. 23, 1941 2,256,615 ALKYLATION PRocEss Fred Hederhorst, Baytown, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application September 25, 1940, Serial No. 358,204

' s claims. vv(ol. 19e-1o) "The present invention relates to a method for producing high octane number isoparaiinic hydrocarbons, particularly those boiling within the motor fuel boiling range, by the catalytic alkylation of isoparaiiins with oleflns. The process is an improvement in the production of such motor fuels by alkylation in connection with the use A of concentrated sulfuric acid as the catalyst.

It has been previously known that saturated high octane number isoparafiins such as, for ex-` at temperatures between about 0 F. and about 100 F. It has heretofore been considered essential in conducting such reactions to maintain the titratable acidity of the ysulfuric acid between about 90% and about 100.6% by weight of sulfuric acid in order to obtain optimum results. By following this procedure it is possible to obtain high yields of iso-octanes when reacting.

isobutane with butenes. Ordinarily, the catalyst concentration is maintained between about 90 and 95 weight per cent of sulfuric acid while carrying out such reactions by the addition of suflicient amounts of strong makeup acid or by the addition of sulfur-containing dehydrating agents such as, for example, sulfur trioxide, fuming sulfuric acid and similar compounds. cessity for maintaining the above-specified catalyst concentrations has been thought heretofore to be universally applicable to the aliphatic alkylation process regardless of the reactants employed. No different acid concentrations were considered to be useful for alkylating isopentane in contrast to the alkylation of isobutane. Likewise, in the case of the olefinic reactants the required catalyst concentration was considered to be the same whether the olefin employed was propene, the butenes, the pentenes or the normally liquidmonoolenic hydrocarbons.

It is an object of the present invention to secure hitherto unexpected high yields of substantially completely saturated branched chain,

normally liquid hydrocarbons boiling within the motor fuel range and having high octane numbers by employing acid of varying concentrations within said ranges and correlating the various concentrations of acid with respect to the particular olens fed to the reaction zone so that the quality and yields of product are not impaired yet 'the acid has a longer useful life with respect to its alkylating activity.

It is a further object of the invention to produce high yields of substantially completely saturated, branched chain. normally liquid hydrocarbons rst from normally gaseous isoparafllns and olens followed by the production of substantially the same quality material in high yields by the use of the spent catalyst from said reaction as an alkylation catalyst for the reaction of normally gaseous or liquid isoparaiiins with normally liquid monoolens. It is a further object of the invention to substantially increase the effective alkylation activity life of concentrateds'ulfuric acid while obtaining high yields of desired saturated hydrocarbon products.

To accomplish the aforementioned objects as well as others which will be apparent upon a full understanding of the herein disclosed invention, it has been found advantageous to employ a sulfuric acid catalyst that is no longer sufficiently strong to produce optimum yields and quality of alkylate from isobutane reacted with-butenes or from isobutane reacted with propane for alkylating isoparans such as, for example, isobutane or isopentane and higher isoparaiiins, with pentenes and higher monooleflnic hydrocarbons even to the point where the lacid strength or titratable acidity falls to as low as between about 82 and about 89%. In the alkylation of isoparains and olens, after a period of time the sulfuric acid catalyst becomes contaminated with organic material which accordingly decreases its titratable acidity. Below about titratable acidity the acid catalyst is no longer economically effective for alkylating isobutane with normally gaseous monoolei'lns. This catalyst has unexpectedly, however, been found to be effective in catalyz'ing the reaction of isoparaflins including isobutane with normally liquid monoolens such as, for example, the pentenes and higher homologues.

In general, the reactionmay be described as follows, although the specific reactants, temperatures and the like are illustrative only and not considered limitative of the invention: Isobutane admixed with butenes may be introduced into an alkylation reactor with a sulfuric acid catalyst having a titratable acidity between about 90% and about Vigorous agitation of the reaction mixture is maintained and the heat of reaction is removed by evaporation of a. portion of the hydrocarbons, thus maintaining the temperature by means of pressure regulation between 55 about 20 F. and about 80 F., preferably 35 F.

Any vapors which arev removed from the reactor may be caustic washed, compressed, cooled and returned to the reactor. The product is withdrawn from the reactor in the form of an emul- -sion of light hydrocarbons, product and acid 1 catalyst. A portion of the emulsion may be returned to the `reactor-. to maintain a high ratio oi' isoparains lto olefins in the reaction mixture.

The remainder of the withdrawn emulsion is' settled in a settler. The acid is separated and a portion or all of Athe saine may be returned to the/'alkylation reactor together withan amount of/strong fresh makeup acid if desired sufficient to maintain the titratable acidity of the catalyst at thedesired level. The normally liluid .product removed from the acid settler is caustic washed and fractionated. The lighter fractions which may contain considerable amounts of unreacted reactants may then be recycled to the reactor and the desired alkylation product re,-

covered as a high octane number motor fuel. In

a second reactor a feed stock containing isobutane, isopentane, or some suitable isoparaiiin or mixture of isoparaiiins, together'with one or more normally liquid monooleins such as,'for example, the pentenes either asv pure hydrocarbons or as commercial mixtures (a suitable feed stock being a C5 cut containing isopentane and pentenes or the utility of the sulfuric acid-composition for catalytic alkylation activity.. Titratable acidities of the sulfuric acid catalysts are really measures A of the percentage of free'sulfuric acid in the acid isobutane with pentenes) is introduced with an i the first alkylation zone, the lighter hydrocarbons p may be caustic washed, compressed, cooled and returned to the reactor. Vigorous agitation is maintained and the emulsionis withdrawn from the reactor,'settled, and the recycling as described .above for the first alkylation stage is carried out acid is returned tothe reactor and the strength .is maintained at the desired level by the addition of further quantities .of acid previously withdrawn 3 from the isobutane-butenes alkylation zone heretoifore described. If desired. all of the acid employed in the second alkylation stage may be obtained from the first alkylation stage once 4'5 y substantially as therein described. The settled that acid has substantially Vlost its optimum catalytic eil'ect for the rst stage reactants. The

normally liquid product withdrawn from the second'a'cid settler is then treated as described in i 'connection with the rst alkylation stage. Acid which has become so spent in the second alkylation stage as to be practically `of no utility in i `that stage may either be employed in a' third alkylation stage employing still more reactive oleflns or it may be. withdrawn and discarded as unfit for utilization in further alkylation reactions but may be used in other petroleum treating operations or itmay be reconcentrated for 3 use in the alkylation described in connection with l the ilrst alkylation stage, and so on.

In describing the process oi' the present invention, the sulfuric acid concentration has been described with reference t'o the weight per centv of 'sulfuric acid in the composition. It is important, however, to understand that the weight 1 per cent of sulfuric acidin the composition is l not entirely an accurate method of measuring composition. Thetlowered titratable acidity of the alkylation catalyst after continued use in an isoparaiilnolen condensation process is due to the build-up or increase in amount of organicl material contained in that catalyst composition.

The lowered titratable acidity is not, however, due to any substantial increase in the amount of water present inythat composition. If the titratable acidity of sulfuric acid is lowered to approximately v83--89% by dilution with water, it will not effectively catalyze either the butenes or pentenes type of alkylation reaction. catalysts employed in the reaction even though spent with respect to the-ilrst stage 'of alkylation seldom contain more than about 5% or 6% by weight of water and usually less, the remainder of the titratable acidity loss being accounted for by the build-up of organic impurities in the composition. y

EXAMPLE 1 In order to illustrate the relatively poor catalytic elects of sulfuric acid in which the'titratable acidity has been reduced by dilution with feed stock being added to the intimately mixed acid-isoparafn composition.

Isobutane-pentene treats employingsulfuric acid diluted with water as catalyst Run No.

A B C Initial acid strength, percent 84. 2 89. 5 97. 3 Vol. amd/vol. oleiin 12.0 12.1 8.9 Composition oi total feed stock. vol. f

percent:

Butenes 0. 3 0. 3 0.1 Isobutane- 74. 5 74. 5 74. 4 n-Butane.. l0. 7 10.`7 10. 3 Pentenes. 4. l 4. l 5. 6 n-Pentane 5. l 5. 1 6. 6 Iso ntane 4. 5 4. 5 2. 6 Ratio: oparaflin/olefln 18. 0 18. 0 13. 3 Vol. .percent yield Cl-free product,

based on olefin charge 106 i 148 169 Distribution of product, liq. vol. perccn Initial boiling point-110 FA 56.6 51. 6 45. 6 11B-265 F l1. 8 34. 8 46. 1 265 IEX-.final boiling point 3l. 6 i3. 6 8. 3

Inspections on product:

A. S. T. M. octane number 80.7 82.5 82.4 Bromine number 29 0. 6 0. 7 Initial boiling point, F 86 92 106 Final boiling point, F 92% oil at 406 440 358 by the addition of water. In .Run A, wherein the catalyst had 84.2% concentration comprising water and acid, a largegpercentage of the nal product was `olen polymer` rather than allqrla-i In general, the

tion product as evidenced by a bromine number of 29.

In another run, a feed stock comprising isobutane and pentenes was alkylated at about 55 F. in a jet type continuous unit with no acid replacement. 'I'he emulsion recycle ratio, that is, the volumes of acid-hydrocarbon per volume of fresh acid, was about 11.2 with no product recycled. The ratio of fresh feed in volumes per unit volume of the reactor per hour was about 0.68, the fresh feed containing about 11.4% unsaturates and having an isobutane to pentenes ratio by volume of about 4:1. This particular apparatus was a continuous unit which operated for a total of 45 hours. At the end of 27 hours of operation the yield of Cs-free alkylate by volume based upon the total olefines added up to that time was about 165% and the titratable acidity of the acid in the reaction mixture was about 87.4. However, the acid composition was substantially anhydrous in character. After a total of 43 hours of continuous operation, the titratable acidity of that same acid was about 82.7% and the yield of Cs-free alkylate by volume was about 175% based on the olefins added. Of this product approximately 77.2% constituted a Cs-free fraction boiling between 105 F. and 310 F. and it had an octane number of about 87.7 and a bromine number of about 0.86. These results show that although the titratable acidity was in the same range as in the case of Run A, but wherein the reduction in titratable acidity was caused by a build-up of organic material rather than by dilution with water, the alkylating activity of that catalyst was better than one having a titratable acidity of 89.5 (Run B) but wherein the remainder of the composition was substantially Water as shown in the preceding table. Note also that the bromine numbers of the products as between a titratable acidity of 84.2 in Run A and 82.7 in the present run were 29 and 0.86 respectively. The acid catalyst in the present run decreased in titratable acidity from an initial concentration of 96.5 to a titratable acidity of 88.2 in the rst hours of operation, and this was almost solely due to a build-up of organic material from the reaction .of isobutane with pentenes. The percentage decrease in titratable acidity due to the formation of water in the catalyst composition is almost negligible.

EXAMPLE 2 'I'he following data show the permissible limits of titratable acidity for the alkylation reactions involving the use of butenes and for the alkylation reactions involving the use of pentenes. The alkylation of isobutane with butenes in the presence of 90 to 95% sulfuric acid will produce optimum yields and quality of product. vWhen this acid is no longer an eiiicient catalyst for this reaction, it is then possible to utilize the acid withoutpurication directly as an effective catalyst for the alkylation of isoparamns with pentenes, This makes the present invention advantageous in that a more economical operation is obtained in an alkylation unit by reason of the fact that the necessity i'or a dual acid catalyst system is eliminated and the alkylation of butenes occurs separately yet simultaneously with the alkylation of pentenes.

An isobutane-butenes alkylation reaction was catalyzed lin a jet type alkylation unit with sulfuric acidhaving an initial acidity of approxid mately 92.0%; the acid in the system had been used for alkylating butenes and its strength had been maintained at approximately 92.0% by discarding a. portion of the acid in the system and replacing with fresh 96.5% acid. The reactor was maintained at a temperature of about 57 F. and the fresh-feed rate amounted to about 1.07 volumes of fresh feed per unit volume of the reactor per hour with an average recycle ratio, that is, recycle of volumes of acid-oil emulsion to volumes of fresh feed, of about 9.9:1. The fresh feed contained about 9.1% of olei'lns, chiefly butenes, with an isoparaiiin to olefin ratio of about 5:1. At the end of 24 hours of continuous operation after discontinuing fresh-acid replacement the titratable acidity of the acid dropped to about 89.3, the yield of C4-free alkylate based on the olens was about 159% by volume, and the octane number of the product was about 92.5. Continued usage of the acid catalyst composition eventually lowered the titratable acidity to 87.0% with an alkylate yield of 142% which had an octane number of 91.7. When the catalyst composition after long usage had reached a titratable acidity of about 82%, theyield amounted toj about 109%, of which 30% of the product boiled above the Cs fraction. It is clearly evident from this that decreased yield, unfavorable product distribution, and lowered octane number of thefalkylate occur when the titratable acidity of the catalyst falls much below 88 or 89% in cases where butenes are being alkylated. As in all alkylation reactions of the type herein specified, the decrease in the titratable acidity is largely due to the increase in the organic material present in the catalyst composition, the percentage of water in any given catalyst composition remaining substantially constant, that is, it does not varymuch more than 1/% to 1% from the original water content of the present catalyst. As previously pointed out, acid strengths of aslow as 83% titratable acidity are capable of successfully catalyzing the isoparaffin-pentenes alkylation, yet in the case of butenes alkylation an acid strength of 89.3% by weight of sulfuric acid after 24 hours of operation without replacement of spent catalyst resulted in just about the lowest permissible titratable acidity limit forthis reaction. In another run carried out while employing isobutane and pentenes in a similar unit maintained under substantially the same reaction conditions and carried out in substantially the same manner, wherein the initial acid concentration was about 96.5% and wherein the .fresh feed contained about 7.7% by volume of olens, largely pentenes with a 7.5:1 isoparaiiin to olefin ratio, the fresh feed was charged at a rate of about 4 litres per hour and the product continuously withdrawn over a total period of about 116 hours of operation of the original catalyst composition; For the first 68 hours of operation the titratable acidity very ,gradually dropped from the original percentage to a total of about 84.9%, at which time the total alkyl-ate yield dropped only from about 183% to 180% by volume. 'I'he octane number of the 105- 265 F. fraction dropped in this same period from about 91.1 to` about 90.7. vHowever, as the titratable acidity dropped below 84.9% (to around 82.1%) the yield of total alkylate immediately dropped' to around 164% by volume .and the octane number of the ,105-265 F. fraction dropped to around 89.1. At the end of 116 hours thetitratable acidity was around 59.7, the alkylate yield had dropped to 51% by volume based on the oletlns, and the octane number of the 265 F. fraction was below 87. With the exception of about of water, the remaining ma- 1. parafiins with olefins and treating operations involving the use of sulfuric acid.

The accompanying drawing isa more or less diagrammatic representation of one simple type of apparatus which may be employed for carrying out the present invention. 'I'he drawing will be described in order to present a better Aunderstanding of the invention. A feed stock' containing on or more monooleflns having four or less carbon atoms per molecule together with suitable isoparailin components is introduced into the reactor 5 bymeans-of lines 2 and 4' controlled by valve 3. Simultaneously with the introduction of the feed stock, the sulfuric acid catalyst of the desired concentration, forex-A ample, from 90% to about 100.6%, is introduced intol the reactor 5 by means of lines 26, I6 and 4 controlled by valves 2| and I9. The mixture of feed stock and catalyst is adequately mixed upon being introduced into reactor 5 by any suitable means, for example, jets, turbo mixers, centrifugal arrangements, porous thimbles, or any other suitable type of mixing device. The emulsion which is formed is allowed to accumulate in reactory 5 until it overflows through lines 6 and 1 controlled by valve 8. The emulsion may then berecycled by means of circulating pump9 back to reactor 5 through lines I0 and 4' controlled by valve II, valve I3 in line I2 being closed. After the Aemulsion has been agitated and recycled a sufficient number of times, all or a portion of it may `be withdrawn from the circulating system by opening valve I3. Any of the unreacted gases or the lighter products which may be contained in reactor 5 may be drawn off through line 24, controlled by valve 25 to maintain lthe desired temperature, and sent to a suitable recovery plant. The reacted emulsion upon entering settler I4 is separated into an upper hydrocarbon layer of alkylate and a lower acid layer which lmay be either returned to the reactor 5 for further use, providing its titratable acidity has not decreased below its point of usefulness, by'means of lines I5, I6,-I8 and 4 controlled byvalves I1 and I9. In the event that the acid has lost its sbstantial utility in the reaction, it may be passed on to a second alkylation unit by means of line 46 controlled by valve 41. The alkylate from settler I4 is withdrawn through line 22 controlled by valve 23, caustic washed, and fractionated to give the desired fractions. Any of 'the undesired product or unreacted reactants contained in feed products which are separated by fractional distillation treatment may be either recycled to reactor 5' in the desired proportions or they may be employedin another alkylat'in unit or in some conventional manner.

- Into the second alkylation unit there is introduc'ed'v by means of

lines

26 and 23 controlled by valve 21, valve remaining closed, a feed stock containing isoparamns'and at least one monoolen containingl at least 5 carbon atoms per molecule; The actual-arrangement of the appaously described in connection with the koleiln having 4 carbon atoms or lower per molecule. The reactor 29, which contains mixing devices previously described with reference to reactor 5,' is a time'tank having an overow pipe 30 controlled by valve 32 and a recycle emulsion line 3| equipped with circulating pump 33 for the return of the emulsion to the reactor 29 by means of

lines

34 and 28 controlled by valve 35. The acid catalyst employed in this reactor comes from the previous alkylation unit by meansl of

lines

46, 44 and 28 controlled by valves 41 and 45. As in the previous reactor the emulsion is recycled through line 3| to the reactor 29 untilsuch' time as a substantial equilibrium has been reached, at which time a portion or all of the unreacted emulsion is -withdrawn through line.

38 controlled by valve 39 into settler 40. Any gaseous products of the reaction or unreacted gaseous constituents of the feed stock are withdrawn from the reactor 29 through line 36 con-'1 trolled by valve 31 and, as has been described in connection with the effluents through lline 24 controlled by valve 25, an economical use of the eiiluents may be made. 'I'he reacted mixture is allowed to settle in settler 40. The acid catalyst, if of suiilcient activity to permit its reusein the reactor 29, is returned -to said reactor by means of

lines

4I, 42, 44 and 28 controlled by valves 43 and 45, valve 5I remaining closed. On the other hand, if the catalyst composition has become sufilciently spent as to lose its substantial utilityv in the present reaction, it may be discarded or it may be in turn introduced into a third alkylation system similar to the two herein described fractions. The motor fuel fractions may be used as such, blended with desired fractions processed from line 22, blended with extraneous naphtha,v etc. Heavier fractions may be recycled to either

reactors

5 or 29 or to `both reactors.

Although` it is preferred to employ isobutane' and mixtures containing isobutane as the parafllnic reactants, it is distinctly understood that isopentane and similar higher homologues containing at least one tertiary carbon atom per molecule may be employed. These higher homologues are especially desirable as reactants where it is desired to produce safety fuels, aviation naphthas, blending agents for motor fuels, and the like. The olelnic reactants may comprise ethylene, propylene, normal butylenes, isobutylene, trimethyl ethylene, the isomeric pentenes i and similar higher monoolenic hydrocarbons of eithera straight chain or branched chain structure as well as their corresponding normally liquid polymers, interpolymers, copolymers, such as diisobutylene, triisobutylenathe codimer's `oi normal butylenes and isobutylene, and the like. Mixtures of two or more of the oleflns and of the paraflins aswell are also particularly adapted for use in the reaction withV certain reservations' hereinafter to be described. Thus it is possible 5 to employ Cz, C3, C4 and/orCs cuts from thermal ratus is substantially identical with that previ: 76

and/or catalytic cracking units, eld butanes which have been subjected to prior isornerizationV lWith regard to the manner of feeding the olefins to the various reactions, it may be stated that the process can be operated so that ethylene and propylene are introduced into the first reactor, that is, the reactor containing the strongest sulfuric acid, the butylenes into the second reactor, and the pentenes and higher olefins into the third reactor, or the C2, C3 and C4 oleflns may all be introduced into a first reactor while the C5 and heavier olefins are introduced into a second reactor. For economic reasons it may be preferred to employ the isoparafn corresponding to the olen introduced into any particular alkylation stage, that is, isobutane is ordinarily contemplated as being introduced with the butenes, isopentane with the pentenes, and so on. The reason for this is that in the ordinary refinery, as it is at present constructed, it is found to be quite expensive to separate C5 parafns from C5 olefins, C4 parafns from C4 oleflns, etc., hence for economical reasons the olen-parain cuts containing the same number of carbon atoms per molecule are usually desirable as such for feeding to the alkylation stages. However, it is within the scope of this invention to alkylate C5 isoparains with C4 olens and C4 isoparaflins with C5 oleflns.

The temperature maintained in the alkylation reactors in the various stages may either be uniform with regard to the various stages or there may be a temperature gradient maintained between the Various stages. Thus, for example, the reactors may be maintained at between about 30 F. and about 85 or 90 F., or the first reactor involving the alkylation of propylene may be maintained at between about 55 F. and about '75 F., with the butene alkylation stage being maintained between about 35 F. and about 45 F., and the pentenes and heavier alkylation stages being maintained between about 50 F. and about 60 F. Stronger acids, of course, are in general employed in connection with the lower molecular weight olefins, whereas the reactivity of the higher olefns appears to be catalyzed sufliciently by the use of vacid of reduced titratable acidity. The temperature may be controlled by means of pressure where the reaction mixture contains readily Volatilizable hydrocarbons, or the reactors may be jacketed and cooled with brine or in any other suitable conventional manner.

'I'he length of contact of the catalyst with the hydrocarbon reactants of course depends to a considerable extent upon the temperature of the reaction and the titratable acidity of the acid as well as the intensiveness of the agitation of the reactants with the catalyst mass. In general, the contact time is maintained between about 0.10 and about 1.50 hours. The reactions may be carried out in either thev liquid or vapor phase, although for commercial operations liquid phases appear to be the more feasible.

Especially in the alkylation of isobutane with C4 olefins the use of excess isobutane is desirable not only because of the fact that excess isoparaffins in general are beneficial to the production of high yields of the desired alkylates but also by employing such excesses of isobutane the pressures can be controlled so that with the vaporization of the excess isobutane the reaction mixture is maintained at the desired temper-l ature. The lower excesses may range'from between 1 to 10 or evenas high as 30 mols per mol of monoolen reactant. Equalmolar quantities of isoparain to monoolefln are, however, contemplated, although it is preferred to employ from 8 to 14 mols of isoparaflin per mol of monoolefin inthe reaction mixture.

EXAMPLE 3 The following data illustrate the results obtained in a commercial scale unit where the spent acid catalyst discarded from the buteneisobutane reaction zone was used to replace spent similar results obtained when the pentene re-4 actor catalyst Was lowered and maintained at about 84% titratable acidity.

In this unit, a refinery C4 stream containing about 12 volume per cent of butenes and about 17 volume per cent of isobutane was divided and charged to each of two jet-type reactors, A and B; a renery C5 stream containing about 38 volume per cent of pentenes was also charged to a third jet-type reactor, C. All of the reactors were refrigerated to control the reaction temperature by evaporating part ofthe light components and withdrawing them from the tops of the reactor towers. After compressing, cooling and liquefying these evaporated light components, they were mixed into astream of eld butanes which had been separated from natural gasoline by fractional distillation. The resultant mixture, which now contained 60 to 65 volume per cent of isoparaiiins but substantially no olefns, was divided and added to the refinery C4 and C5 streams entering the jets near the bottoms of reactors A and C, respectively, in order to maintain a high mol ratio of isoparafllns-to olefins in these reaction zones. To achieve asimilar object in reactor B, the total product and the unevaporated, unreacted hydrocarbon components recovered from the settler adjoining reaction zone A were combined with the olefin bearing feed to this reactor. An emulsion, consisting of sulfuric acid catalyst, unreacted paraflin hydrocarbons and alkylation product, was withdrawn near Vthe top of each reactor tower. One part of this emulsion from each reactor was recycled "back to its respective reaction zone while the and replaced with fresh 96.5% sulfuric acid. The

acid discarded from these two settlers, however, Was still useful in catalyzing alkylation of isoparaii'ins with pentenes. 1

During one operation indicated in the followin table, the entire quantity of butene-spent catalyst discarded from settlers A and B was used to replace pentene-spent catalyst continuously discarded from settler C. (Run No. II.) other operation reported in the table, only about half of the spent catalyst discarded from settlers A and B was utilized to continuously replace a substantially equal volume of catalyst in settler C. (Run No.1.)

In the 'Patent is:

Run N o.

I II

Reactor unit A. B C A B C Total olefin bearing charge: v

Barrels per da 4, 663 4, 135 l, 700 4, 093 3,113 1, 112 Oletlns, rcent volume. 11. 6 11.6 39. 1 13. 6 13.6 37.8 .O artels per day. 541 480 665 555 424 420 Field butane and recycle, barretlsger day 8, 517 9, 610 10,812 2,043 6, 766 Vol. f leed/vol. reactor 0. 57 0. 50 0. 31 0. 50 0. 38 0. 2l Average temperature in reactor, 39 39 5l 39 39 50 Titratable acidity. percentv wel 93.7 93.8 84 2 93.6 93 7 90.4 Water in acid, percent wt. 2. 2. 2 3 3 2. 8 2 2 3. 1

Acid replacement, gal. per

ay 17, 544 2 18, 261 Mol ratio isobutane/olens (net ov 6. 7 7. 6 Total yield of depentanize product:

Barrels per day 2500 2335 Volume percent based on oietins charged. 148 167 Weight percent based on olens charged-- 171 192 Yield of aviation alkylate,

vollilpercent: 4 68. 0 68. 0 tial boiling point,F 182 182 50%03 at F.. 220 222 Final boiling point 268 270 ASTM octane number. 92. 5 92. 7

. 96.5% sulfuric acid introduced into both reactors A and B to maintain operating level of 93-94%; part ol' acid discarded from reacufir8s2A85a7i'id B introduced into reactor Cto maintain operating level o I 96.15%;z sulfuric acid introduced into both reactors A and B to maintain operatinglevel of {i3-94%' all of acid discarded from reactors A and B introduced into reactor 'C to maintain an operating level of at lating the olefin activity and acid concentrationl zones at least one monooleiin having a diierent degree of alkylation activity from the oleflns in-v troduced in the other alkylation zones, correso that the olefin having the greatest degree of alkylating activity is in contact with the acid of lowest alkylating concentration, and using the at least partially spent sulfuric acid from one zone l in another zone utilizing acid of a lower titratable acidity. i

2. The process as in claim 1 wherein butenes are introduced into the nrst alkylation zone and pentenes are introduced into the second alkylation' zone, wherein the titratable acidity of -the sulfuric acid in the first alkylation zone lies between about 90% and 100.6% sulfuric acid and the titratable acidity inthe second zone lies between about 82% and about 89.9% sulfuricacid, and wherein the spent acid from the rst zone is employed as the alkylating acid in the second zone.

3. A process which .comprises reacting isoparailns with nionooleiins containing at least 5 carbon atoms per molecule under alkylating reaction p conditions in the presence of a sulfuric acid alkylation catalyst composition which has previously lbeen employed as an alkylation catalyst in the alkylation of isoparaiilns'with monooleilns isoparains with Ca-C4 monoolens.

Having thus fully described the invention, what is desired to be secured and claimed by Letters 1. In a process for .the production of normally liquid, branched chain paraiiinic hydrocarbons 100% in each zone, introducing into one of said ployed.

having fewer than 5 carbon atoms per molecule and whose catalytic activity has become substan.. tially decreased for promoting the alkylation of the isoparains withthe said olens having less than 5 carbon atoms per molecule.

4. The process as in claim 3 wherein the mono- I oleflns reacted are pentenes.

5. The process as in claim 3 wherein the catalyst used has been previously used in alkylating 6. A process which comprises reacting isobutane with butenes under alkylation reaction conditions in the presence of between about and about 100.6% sulfuric acid and alkylating isopentane with pentenes under alkylation reaction conditions in the presence of substantially anhydrous, ai; least partially spent, sulfuric acid alkylation catalyst previously employed in promoting the first-mentioned alkylation reaction.

the titratable acidity of the pentenes alkylation acid being between about 82% and about 89.9%.

'7. The process as in claim 6 wherein the iso- Y paraflin is present in each alkylation reaction'in substantial molar excess over the olerlns employed.

8. The process as in claim 6 wherein the isoparamn is isobutane lin both alkylation reactions and wherein the-isobutane is present in substantial molar excess over the respective oleilns ern- FRED HEDERHORST.