US 2826620 A
Description (OCR text may contain errors)
'March Il, 1958 MP. MATUszAK POLYMERIZATION AND ALKYLATION OF HYDROCARBONS Filed July 5o, 195e INVENTOR. NLP. MATUSZAK United ttes Patent O POLYMERIZATIGN AND ALKYLATIDN OF HYDROCARBONS Maryan P. Matuszak, Bartlesville, Ghia., assigner to Phillips Petroleum Company, a corporation of Deiaware Application July 30, 1956, Serial No. 600,973
Claims. (Cl. 260677) This invention relates to the production of motor fuels. In one aspect it relates to the prepartion of a feed stock for use in the production of high octane-number motor fuels. In another aspect it relates to the production of high octane number motor fuels or blending stocks therefor, in high yields.
One specific embodiment of my invention involves treatment of a feed stock containing one or more 1- olelins, one or more 2-oleiins and one or more isoparaffins for removal of the l-olelins and exposing the resulting hydrocarbon mixture to alkylation conditions in the presence of, for example, hydrofluoric acid, to produce a high yield `of alkylate based on the olefin content of the alkylation feed. The process is especially applicable to olelins and isopara'ns of 3 to S carbon atoms per molecule. Specifically, my invention involves treatment of petroleum refinery streams containing predominantly low molecular weight l-olefins, 2-olens 'and isoparains, for example those of 3 to 5 carbon atoms, for removal of the l-oletins and producing alkylate from the boletin depleted material.
One object of my invention is to provide a process for producing high anti-knock motor fuel or blending stocks therefor.
Another object of my invention is to provide a process for producing high anti-knock alkylate in high yield based on the olelin content of the feed stock to `the alkyl'ation reaction.
Still another object of my invention is to provide a process for producing high anti-knock alkylate suitable for blending in motor fuels from available plant streams containing olefin and isoparafiin hydrocarbons and too volatile for automotive fuel use.
Yet another object is to provide a process for removing l-olens from such feed streams prior to the alkylation step and in such a form as to be commercially useful.
Other objects and advantages of my process will be realized upon reading the following disclosure.
The drawing illustrates diagrammatically one arrangement of apparatus for practicing the method of my invention.
One specific embodiment of the present invention comprises selective polymerization of l-olefins in a mixture of oleiins including, for example, propylene, l-butene and l-pentene and thereafter catalytically alkylating a lowboiling isoparaiiin such as isobutane and/or isopentane with the remaining 2-olein and/or isoolelin, preferably in the presence of a catalyst comprising hydrogen iiuoride. By this operation, parafiins for use in motor fuels are obtained which are superior in quality to those obtainable by alltylation of the isoparans with an original l-olen and 2oleiin containing feed stock. As is well known, high-octane motor fuel can be produced by the alkylation of low-boiling isoparains with low-boiling olens in the presence of suitable catalysts whereby the isoparaiiins condense with the oletins to form saturated compounds within the gasoline boiling range. While and sealing compounds, as adhesives for the manufacture various isoparalins :and olelins can be employed for this alkylation reaction, those containing 4 carbon atoms to the molecule are especially desirable not only because they produce alkylation products having highly desirable octane ratings but also because they are readily available in large quantities. Charge stocks for the production of alkylate motor fuel comprising butane-butene mixtures are obtained for example, by dehydrogenation of butane fractions separated from natural gas, by fractionation of cracking-still gases, or from other reinery streams. 'Ihese charge stocks may contain all the butane and butene isomers, especially isobutane, normal butane, isobutene, butene-l and butene-2 in varying, although significant proportions. The nature of the butene isomer subjected to the alkylation reaction affects the yield and quality of the product. Isobutene and butene-2 give alkylate products superior in yield and quality to alkylates from isobutene and butene-l mixtures.
It has been found that certain chromium oxide catalysts (subsequently described herein) selectively catalyze the polymerization of l-oletins to high polymers. By high polymers, I mean polymers having a molecular weight of the order of 500 or higher, usually 1000 andl higher, e. g. in the range 1000 to 200,000 and greater. The 1-oleiins ordinarily involved here are those having from 3 to 8 carbon atoms per molecule and include propylene, l-butene, l-pentene, l-hexene, Z-methyl-lpentene, l-heptene, and l-octene. The l-oleiin must have no branching nearer the double bond than the 4 position unless it is a conjugated d-iolefin, in which case branching at the 3-position is permissible. The catalyst promotes the polymerization of other oleiins, such as 2- butene, 2-pentene, isobutene, Z-hexene, 3-hexene, and the like, but the products are ordinarily relatively low-boiling liquids, such as the dimer, the trimer, and the like. Also the yield of polymer from the 1oleiins is generally much greater than from the unbranched oleiins which have no terminal double bond.
The chromium oxide catalyst utilized for the l-olefin polymerization comprises chromium oxide associated with at least one additional oxide selected from the group consisting of silica, alumina, zirconia, and thoria. The additional oxide is often used in a highly porous form, such as a gel. It is desirable, in order to obtain maximum activity, that an appreciable portion of the chromium in the chromium oxide be present in the hexavalent state and that the catalyst be activated by heating at an elevated temperature, preferably under non-reducing conditions or in a nonreducing atmosphere. The total chromium content of the catalyst can range from 0.1 to 50 Weight percent or higher, but is most frequently in the range 0.1 to 30 weight percent, e. g. from l to 5 weight percent. The hexavalent chromium content of the catalyst, as determined by leaching with water and determining the chromium content of the leachings, is at least 0.1 Weight percent. Although the catalyst can be prepared by a variety of methods, a highly suitable method comprises impregnating at least one of said additional oxides with an aqueous solution of a chromium salt ignitable to chromium oxide, draining away excess solution, drying, and heating or lcalcining at a temperature in the range 450 to 1500 F., preferably 750 to l100 F. The calcination or heating is preferably conducted in a nonreducing atmosphere, preferably in the presence of oxyf tain fractions which are useful as adhesives for surgicaland pressure sensitive tapes, as constituents of calking of laminated paper, as hydraulic fluids, as coatings for tracing paper and for electrical capacitators, other surface coatings and rubber extenders. Some of the polymer products can be used as lubricating oils orY additives prepared from the chloride and sulfate are partially converted to oxide during activation. The concentration of lchromium in the catalyst can range from 0.1 to 30 weight percent, but is usually in the range of l to 25 weight percent and often in the range 0.1 to 10 weight percent. The catalyst support may be alumina and/or silica. A composite catalyst support containing a major portion of silica and a minor portion of alumina is highly satisfactory. A commercial 90 weight percent silica-10 weight percent alumina coprecipitated gel often used as a crackingcatalyst has been used as a support for chromium oxide, the resulting catalyst being highly active for the l-olefn polymerization. This silica-alumina, having been treated with steam-air mixture at elevated temperatures (500-lOO E), is macroporous. This property is believed important in the removal of the heavy polymer from the chromium oxide-silica alumina catalyst surface. A chromium oxide-silica catalyst tends to become Ydeactivated more readily than a chromium oxide-silica-alumina catalyst. A chromium oxide-alumina catalyst usually has a lower activity than a chromium oxide-silica-alumina catalyst. The reaction can be carried out by iixed-bed or mobileY catalyst technics.
Although the selective polymerization according to this invention can be conducted over a broad range of conditions, theV preferred conditions for the polymerization using chromium oxide-silica-alumina catalyst include a temperature in the range of 150 to 250 F., more preferably 170-225 F., a pressure sufficient to maintain the hydrocarbon mixture substantially in the liquidphase, and a reaction time from 15' minutes to 20 hours.
A reiinery (3a-C4 stream can be charged at polymerization conditions using chromium oxide-silica-alumina catalyst to produce tacky polymer and an .improved alkylation feed stock in accordance with this invention. Propyl-V ene and. l-butene are converted to tacky polymer. 2- butene does not'react appreciably,` and isobutene is con'- verted to dimer and trimer which still react to give high quality alkylate. Alkylate quality is thus improved while thew l-butene isselectively removed and converted to a more valuable product. The invention includes a combination of steps which comprises selectively polymerizing one or more straight-chain 1oleiins in a mixture of one or more lother olens, as by contacting under suitable polymerization conditions with a catalyst like chromium oxide-silica-alumina that selectively polymerizes the unbranched l-olefins, removing the resulting polymer, and utilizing the resulting l-olen-depleted mixture for alkylation', as in hydroiiuoric acid alkylation of an isoparaflin. The alkylation reaction of the process is the known alkylation reaction carried out in the presence of hydrouoric acid catalyst, such as is described and exempled in my Patent 2,502,015A (1950)'.
Individual olens were polymerized in runs utilizing a xed bed of chromium oxide-silica-alumina catalyst (Crv content 4 Weight percent),v at a pressure of. 600 pounds' persquar'e'inch at 190 F. and 2 liquid' hourly spacevelocity of feed containing 20 mol percent'ofV thev olefin and mol percent isobutane. The duration of the runs was 4 to 6 hours; resulting conversions and the qualitative nature of the polymers were as follows:
Average- Monoiner Conver- Type of polymer, etc.
sion, percent Normal 1oletlns:
Propyleno 91 tacky, semi-solid. l-Butene.-. 75 tacky, elastic semi-solid.
I-Pentene 82 taekier than polypropylene;
semi-solid. Normal 2-olens' 2-butene. 5` liquid (dimerand trimer). Z-pentene- 5 liquid. Branched 1-oleiins:
Isobutylene 87 liquid (dimer and trimer).
2-methyl-1-butene 6 liquid The catalyst was'prepared by impregnating 90 weight percentl silica-l0 weight percent alumina coprecipated gel compositer with a l-molar 'aqueousv solution of chromiumtrioxide,-dryin,gV the impregnated solid and heat; Ying in dry air at 930 F. for 5 hours.
These'l results illustrate the nature ofV the polymerizatin and show that lol'eiinsV form tacky, semi-solid polymer'with the chromium oxide-silica-alumina catalyst,` and can thereby be removed from the other oleiins. The 2-oleiins`react to a relatively slight degree, while the branched olefms such as isobutylene are converted tor'dimer and trimer which still react to give high quality' alkylate.' Alkylate quality is thus'improved while the l-olens are selectively removed and converted to a more-valuable product.
The improvement in alkylate quality Vand yield is illustrated'by the following data:
In the operation of my process, as illustrated in thel accompanying drawing, catalyst chambers 2 and 3` are charged wtih the above described chromium oxide-silicaalumina catalyst. The 1-olefin, 2-olen and isoparain charge stock is passed through line 1 from a source, not shown, into for example, reactor 2. The catalyst is maintained at a temperature between about and 225.vu F. The 1'olen hydrocarbon or hydrocarbons polymer-ize in thepresence of the catalyst. to a tacky semisolid material which is retained on the catalyst. TheV 1'-oleiin hydrocarbon depleted stock leaves the bottom of vesselv Z and is transferred via line 4 to an alkylation Vessel 5.` In this vessel the charge stock containing mainly 2-oleiin and isoparaflin hydrocarbons is` contacted with, for example, hydrogen fluoride under alkylating conditions. The reaction products .arek passed through line 8y into a separation zone 9 ini which hydrocarbon and acidlayers'are allowed to separate,V the hydrocarbonlayer being above the acid layer. The separated hydrocarbon layer is withdrawn via line 10 and introduced into a fractional distillation column 11 for separation of accompanying hydrogen iiuoride catalyst and unalkylated` Aisoparaiin hydrocarbons. These lattermaterials pass overheadV from this still via lines 12 and 21 and are recycled' into the alkylationl zone" 5., Bottoms' fractionator 14 in which high antiknock motor fuel is separated from high boiling material. 'Ihe motor fuel is`passed through line 16 to storage or such disposal as desired. Bottoms from column 14, usually small in quantity, are removed via line for such disposal as desired.
Since the alkylate contains organically combined iiuorine, usually about 0.01 weight percent, it is preferably passed through line 24 into a purifier zone 25 containing a metal impregnated contact material or bauxite at a temperature of about 200 to 500 F. These materials effect the removal of organic iiuorine compounds. Alkylate substantially free from organic iiuorine is then passed from the purifier 25 through line 26 into the line 13 for passage into the alkylate still in which the alkylate is fractionated as above stated.
The acid layer in the separation zone 9 is withdrawn therefrom through a conduit 17 and introduced into a hydrouoric acid regeneration zone 18. When hydrofluoric acid is used as the alkylation catalyst zone 18 can be a still in which the acid, together with any unreacted isoparatiin hydrocarbon is removed overhead via line 19. From this line the catalyst is passed on through lines 21 and 7 into the alkylation zone 5. An organic residue, which is usually small in volume, is withdrawn through line for such disposal as desired. Makeup catalyst, as needed, can be added to the system through line 7.
When suicient tacky polymer accumulates in reactor 2 to restrict hydrocarbon ow therethrough, the charge stock can be switched from reactor 2 to reactor 3. The polymer is then removed from reactor 2 by backwashing with such a hydrocarbon solvent as propane, isobutane, n-pentane, isopentane, n-heptane, isooctane, cyclopentane, cyclohexane, benzene, toluene, or xylene. The higher molecular weight paraiiinic solvents are better solvents for the polymer than are those of lower molecular weight, and the cyclic hydrocarbons have higher solvent power for the polymers than do the paralins. After the catalyst has been backwashed suiiiciently to remove polymer mechanically and in solution, the flow of the backwashing liquid is terminated, and the vessel is then ready for use in the 1oleiin polymerizing operation. The backwash liquid enters the system through line 22, from a source, not shown, and leaves the system through a line 23 for such disposal as desired. The solvent is preferably heated to a temperature in the range 250 to 500 F., in means not shown, prior to entry into reactor 2 or 3.
When it is desired to recover the 1olefin polymer, it can be recovered by distilling olf the solvent. The solvent can then be reused.
In a modication of my invention, the eiiiuent from the l-oletin polymerization in reactor 2 or 3 can be vaporized to separate any accompanying polymer as residue, and recondensed prior to passage to alkylation zone 5.
In my process, in general, any known alkylation catalyst, such as sulfuric acid, phosphoric acid, fluid complexes of polyvalent metal halides such as aluminum chloride or aluminum bromide with hydrocarbons, hydroiluoric acid, boron iiuoride andY mixtures of hydroiluoric acid and boron lluoride can be used. Substantially anhydrous hydrouoric acid is preferred because of the relative ease with which it can be used and re-used and because of the superior quality of the alkylate that is produced. Known alkylation conditions are employed in the alkylation vessel 5, such as thorough agitation, a temperature in the range of about 30 to 250 F., suicientr pressure to maintain liquid phase conditions, a stoichiometric excess of isoparain with respect to the 2-olen, a reaction time in the range of about 1 to 90 minutes, and the like. catalyst, preferred alkylation conditions comprise agitation of the quality produced by an eicient turbomixer, and overall feed isoparatiin-to-oletin mol ratio in the When hydrofluoric acid is the` to olens of 5:1.
range of about 3:1 to 10:1, a temperature in the range. of about to 125 F., and an average residence time in the alkylation zone of about 5 to 30 minutes. After a suitable residence time, the alkylation mixture is passed to the separation zone 9 which may be a centrifuge or a gravity settler. To maintain a` proper isoparain-toolefin ratio for optimum alkylate output it is sometimes desirable to add additional isoparaiiin over that contained in the original oleiin-isoparatiin feed stock. Such isoparain can originate from any suitable source, and is passed through line 27 into the alkylator 5.
Such auxiliary apparatus as pumps, valves, regulators, iiow controllers, temperature and pressure recording and controlling apparatus have not been shown on the drawing nor described in this specification for reasons of brevity and simplicity. The need for such apparatus, its' installation and operation are well understood by those skilled in the art.
Equipment and materials of construction should be selected from those commercially available bearing in mind any corrosive properties of materials and reagents under treatment.
According to a specific embodiment of this invention, a C4 hydrocarbon fraction is contacted with a chromium oxide catalyst under polymerization conditions and an alkylation feed is subsequently recovered and subjected to alkylation conditions. The C4 fraction has the following composition:
Weight percent The catalyst is a chromium-oxide-silica eatalystprepared as previously described herein (impregnation of silica-alumina gel composite, drying, and heating in anhydrous air at 930 F. for 5 hours) and has a total chromium content of 4 weight percent and a hexavalent chromium content of approximately 3 weight` percent. The silica:alumina ratio in the catalyst is 9:1 on a weight basis.
The above described C., fraction is contacted with a fixed bed of the chromium oxide catalyst at a temperature of 190 F., a pressure of 600 p. s. i. and a liquid hourly space velocity of 2. The efduent from the contacting with the chromium oxides catalyst is ashed at 300 F. and atmospheric pressure and the vaporized to provide a mixture having a molar ratio of isobutane This mixture is pumped into an alkylation reactor provided with a motor-driven turbomixer. Liquid anhydrous hydrogen uoride is simultaneously supplied to the alkylation reactor. The alkylation reactor is maintained at a temperature of F. and a pressure of p. s. i., the reactants thus being maintained substantially completely in the liquid phase. The residence time of the hydrocarbons in the alkylation reactor is maintained at approximately l5 minutes. TheV drocarbon phase is washed in sodium hydroxide solution` to remove .dissolvedl hydrogen 'iluoride The neutralized hydrocarbon product is fractionated to recover a butane fraction, an'alkylate fraction having a boiling range of approximately 100 to approximately 365 F., and a higher boiling or residual fraction. The alkylate fraction is contacted with .calcined bauxite at approximately 150 F. and a liquid hourly space velocity of 2, the alkylate being maintained in the liquid phase during the contacting. Thus deuorinated alkylate is recovered as a product of the process and has an ASTM octane number of approximately 90.
After a period of time on stream, the contacting of the butane fraction with the chromium oxide catalyst is discontinued and normal heptane in the liquid phase at altemperature of approximately 300 F. ispassed through thev chromium oxide catalyst bed to remove accumulated polymer therefrom. VTheheptane eluent and the accompanying polymer are then subjected to heptane reiluxing conditions at atmospheric pressure, a portion of the boiling liquid and accompanying suspended material being continuously Withdrawn and subjected to filtration under pressure. The solid removed by filtration is a highly crystalline solid polymer of l-butene and is useful for the production of molded articles, extruded pipe and tubingand insulation. The ltrate is ilashed to remove heptane. The residual material from the hashing is a tacky or semisolid material which isuseful as a viscosity index improver for lubricating oils. This material can be improved as a lubricating oil additive by distillation invacuum toremove materialsboiling V'belowv 900 ll?.
While certain process steps, structures, compositions,` and examples have been described for purposesv ofv illustration,it is clear that the Vinvention visnot limited thereto, and that-variation and modification arepossible Within the scope of the disclosureand the claims.
`This application is a continuation-in-part of my application Serial No. 306,343, liled August 26, 1952,y now abandoned.
1.A process vfor the vselective removal of a l-olen from a mixture of hydrocarbons comprising a l-Qleiin having from 3 to 8 carbon atoms per molecule andno branching nearer the double bond than the 4-position in admixture with a dilferent olefin, which-process comprises contacting said Imixture with a chromium oxide catalyst comprising chromium oxide .associated with at least one member of the group consisting of silica, alumina, zirconia and thoria, -said catalyst-having `.been treated to impart polymerization activity thereto, selectively polymerizing said l-olen to high polymer, and` recovering a resulting mixture substantially depleted ivith respect to l-ole'lin.V
`2. A process for Vthe selective removal of a l-olein from a mixtureof hydrocarbons havingfrom 3 to5v carbon atoms per molecule and including a l-oletin, a 2- oletin and anisoparail'in which process comprises Contacting said mixture ata temperature inthe range 150 to 250 F. with a catalystrcomprising from 0.1 to 30 weight percent chromium in the form of chromium oxide, at least part of the chromium being in thev hexavalent state, associated with' at least one member of the group consisting of silica, alumina, zirconia, and Vthoria, said catalyst having been activated"V by heating at an elevated temperature, effecting a selective conversion of l-olefm to high polymer, and recovering a resulting mixture substantially depleted v/ith"respect` to l-olen.
3. An alkylation processwhich comprises contacting a mixture comprising a l-olefin, a .2A-olefin, and an isoparaihn and being composed'ot lhydrocarbons having from 3 to 5 carbon-atoms permolecule, at a temperature in the range of 150 t0" 250 F. with a catalyst consisting-essentiallyfof frorn10.ly to 30 WeightY percent chromium in the form' of chromiuml oxide of which atleast a part=ofthe chromiumis in the hexavalent state,.associated with at least one member ofthe group consisting of silica,
alumina, zirconia and thoria, effecting a selective conversion of said l-olen to high polymer, recovering said high polymer, recovering a hydrocarbon mixture substantially depleted with respect to said l-olen, and subjecting ,the depleted mixture to alkylation conditions of temperature, pressure and contacttime in the presence of a stoichiometric excess of alkylatable isoparatn with respect to olefins and in the presence of an -alkylation catalyst, and recovering a resulting alkylate.
4. A process for the selective removal of a 1olein from a mixture of hydrocarbons having from 3 to 5 carbon atoms per molecule and including a l-olelin, a 2- olefin and an iSOparan'in, which process comprises contacting said mixture, at a temperature in the range to 225 F. and a pressure sufficient to maintain the hydrocarbon mixture substantially in the liquid phase, with a catalyst comprising from 0.1 to 10 weight percent chromium as oxide, of which at least part of the chromium isV in the hexavalent state, associated With a silicaalumina composite, thus eifecting a selective conversion of l-olelin toV tacky polymer, a substantial proportion of which remains in contact with the catalyst, and recovering a resultingr mixture substantially depleted with respect to l-olen.
5. An alkylation process which comprises contactingY a mixturecomprising l-butene, Z-butene and isobutane, at a temperature in the range 170 to 225 F. and a pressure sufficient to maintainV the hydrocarbon mixture substantiallyin the liquid phase, with a catalyst consisting essentially of from l to 5 weight percent of chromium as oxide, of which at least part of the chromium is in the hexavalent state, the remainder of said catalyst being a silica-alumina composite, thus effecting a selective c011-V version of the l-butene to tacky polymer, recovering said polymer, recovering a hydrocarbon mixture substantially depleted with respect to l-butene, and subjecting the, depleted mixture to alkylation conditions of temperature, pressure, and contact time in the presence of a stoichiometric excess of isobutane With respect to olefins and in the presence of an alkylation catalyst, and recovering a resulting alkylate.
6. An alkylation process which comprises contacting a mixture comprising propylene, l-butene, 2-butene and isobutane, at a temperature in the range 170 to 225 F. and a pressure sutlicient to maintain the hydrocarbon mixture substantially in the liquid phase, With a catalyst consisting essentially of from l to 5 weight percent of chromium as oxide, of which at leastV part of the chromium is in the hexavalent state, said chromium oxide being supported upon a macroporous silica-alumina composite, thus selectively converting propylene and l-butene to tacky polymer which remains associated with said catalyst, recovering said polymer, passing a resulting hydrocarbon mixture substantially depleted with respect to propylene and l-butene to an alkylation zone and therein contacting thedepleted mixture With a hydrofluoric acid alkylation catalyst in the presence of a substantial stoichiometric excess of isobutane with respect to olens at temperature and pressure. conditions suitable for the alkylation of said isobutane, and recovering a resulting alkylate.
7. A process according to claim 6 wherein .said polymer is recovered by contacting the lchromium oxide catalyst with a solvent for said polymer and recovering said polymer from admixture with said solvent.
8. A process for the polymerization and alkylation yof a mixture of hydrocarbons having from 3 to 5 carbon atoms per molecule and yincluding a l-olen, a 2olen, and an isoparan, which process comprises contacting said mixture, at a temperature in the range 170 to 225 F. and a pressure sullicient to maintain the hydrocarbon mixture substantially in the liquid phase, with a catalyst comprisingfrom 0.1 to l0 Weight percent chromium as oxide, of which at least part of the chromium is in the hexavalent state, associated with a silica-alumina composite, thus effecting a selective conversion of 1o1en to tacky polymer, recovering said polymer, recovering a hydrocarbon mixture substantially depleted with respect to 1olef1n, and subjecting the depleted mixture to alkylation conditions of temperature, pressure, and Contact time in the presence of a stoichiometric excess of isoparain with respect to olens and in the presence of an alkylation catalyst, and recovering a resulting alkylate.
9. An alkylation process which comprises contacting a mixture of hydrocarbons having from 3 to 5v carbon atoms per molecule and including a 1oleiin, a 2-oleiin and an isoparain, at a temperature in the range 170 to 225 F. and a pressure suicient to maintain the hydrocarbon mixture substantially in the liquid phase, with a catalyst comprising, as an essential ingredient, from 0.1 to 10 weight percent of chromium as oxide, of which at least part of the chromium is in the hexavalent state, the remainder of the catalyst being at least one oxide selected from the group consisting of silica, alumina, zirconia, and thoria, thus eiecting a selective conversion of 1-olefn to tacky polymer, recovering a hydrocarbon mixture substantially depleted with respect to l-olen, subjecting the depleted mixture to alkylation conditions of temperature and pressure in the presence of a stoichio- 10 metric excess of isoparan with respect to olens, and recovering a resulting alkylate.
10. A process for the selective removal of a l-olen from a mixture of hydrocarbons comprising a l-oletin having from 3 to 8 carbon atoms per molecule and no branching nearer the double bond than the 4-positi0n in admixture with a different olefin, which process comprises contacting said mixture, under polymerization conditions of temperature, pressure, and contact time, with a chromium oxide catalyst comprising chromium oxide, in which at least part of the chromium is hexavalent, associated with at least one member of the group consisting of silica, alumina, zirconia, and thoria, selectively polymerizing said l-olen to high polymer, and recovering a resulting mixture substantially depleted with respect to 1-olen.
References Cited in the le of this patent UNITED STATES PATENTS 2,332,376 Stahly Oct. 19, 1943 2,427,293 Matuszak Sept. 9, 1947 2,502,015 Matuszak Mar. 28, 1950 2,591,367 McAllister Apr. 1, 1952