US2495648A

US2495648A - Hydrocarbon treating process

Info

Publication number: US2495648A
Application number: US692882A
Authority: US
Inventors: Hervey H Voge; George M Good; Bernard S Greensfelder
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1946-08-24
Filing date: 1946-08-24
Publication date: 1950-01-24
Anticipated expiration: 1967-01-24

Description

Jan. 24, 1950 H. H. \IOGE ET AL HYDROCARBON TREATING PROCESS Filed Aug. 24, 1946 4 Sheets-Sheet l o m xm lso Paraffin N Buiglene Hea'rer lr wen'lors Her-veg H. Voge George M. Good Bernard 3. 6r el r I By iheir A++orneg= g?:

J" 24, 1950 H. H. VOGE ETAL HYDROCARBON TREATING .PROCESS 4 Sheets-Sheet 3 Filed Aug. 24, 1946 .aopeay .aopnag .xowuo 1 .09.15

.aopeaa lnveniors Herve-g H. \loge .aqwaedag George M. Good 5 ihe'n" A1+orneg Patented Jan. 24, 1950 HYDROCARBON TREATING PROCESS l-lervey H. Voge, Berkeley, George M. Good, Al-

bany, and Bernard S. Greensfelder, Oakland, Calif., asslgnors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application August 24. 1946, Serial No. 692,882

8 (Ha. i

This invention relatesto the separation and/ or production of useful products from lower boiling olefins, especially olefins having from 4 to 6 carbon atoms and hydrocarbon mixtures containing sub stantial quantities of such olefins. In one embodiment of the invention, normal olefins are separated from hydrocarbon mixtures containing them as well as their branched chain isomers through selective conversion of the branched chain isomers into saturated hydrocarbons which may be separated from the normal olefins by conventional separation processes. In other embodiments of the invention this selective conversion of branched chain olefins to saturated hydrocarbons is utilized to produce an iso-paraffin and/or gasoline.

An object of the invention is to provide a new and improved method for the separation of normal olefins from a hydrocarbon mixture containing the same in admixture with an isomeric branched chain olefin. Thus, an object is to provide a method for the separation of normal butylenes from refinery butylene fractions.

Another object of the invention is to provide a method for the production of iso-parafiins. Thus, an object of the invention is to provide a method for the production of isobutane from butylene or refinery butylene fractions and the production of isopentane from amylene fractions.

A further object of the invention is to provide a method for the production of improved yields of alkylate gasoline having improved volatility from refinery butylene fractions.

These and other objects which will be apparent in the description of the invention and its uses are attained through the catalytic treatment of suitable olefinic fractions under conditions to more or less selectively convert the olefins having a branched chain into the corresponding isoparamns. Thus, the process of the invention in its more general aspect involves reacting an olefinic hydrocarbon fraction containing substantial amounts of a normal olefin and an isomeric branched chain olefin in the vapor phase in the presence of a cracking catalyst at a temperature below that affording cracking of the hydrocarbon mixture but above that at which substantial polymerization to higher boiling olefins takes place and for a time adjusted to selectively convert branched chain olefins to saturated products consisting largely of the corresponding branched chain paramn.

The process is generally applicable to the treatment of lower boiling hydrocarbon fractions such operations. Preferred fractions are those having from 4 to about 6 carbon atoms, i. e. boiling below about 70 C. Particularly suitable materials are the so-called refinery butylene and amylene fractions. In general, separation of one or more of the components of such fractions is possible by the application of conventional methods. However, a complete separation is too difiicult to be feasible except on a small scale for special purposes. The usual refinery butylene fraction represents the simplest case because of the fewer possible isomers. In this simplest case, certain separations can be made quite readily. However, the separation of butene-l from isobutylene is difficult. These two isomeric olefins boil within 1 of one another and are generally quite similar in properties. However, a practical means for this separation is desirable, since these two olefins are desired separately for different purposes. The normal olefin is desired, for example, as a starting material for the production of butadiene, whereas the isobutylene is desired separately as a starting material in various syntheses.

The catalyst used in the process of the present invention is a cracking catalyst. The term cracking catalyst is meant to designate that group of catalysts which is active in catalyzing the scission of 0-0 bonds, but which has no appreciable ability to catalyze the addition of hydrogen to an olefinic bond. Examples of such catalysts are the complex silica-alumina, silica-magnesia, silicaas are commonly encountered in various refinery lid zirconia-alumina, and alumina-boria cracking catalysts and the activated clay cracking catalysts. Any of the vrious known cracking catalysts of this general type (frequently referred to as clay-type cracking catalysts) may be used. The usual cracking catalysts rarely contain a hydrogenating component. However, occasionally a hydrogenating component (e. g. Mo, W, Co) is incorporated in a small amount to aid in the catalyst regeneration or for other reasons. Such catalysts may be used in the process of the present invention, in the usual case where there is no appreciable free hydrogen present in the reaction zone. Ordinary hydrogenation with free hydrogen is avoided. Such hydrogenation, it is found, gives a totally different result.

The conditions of treating in the process of the present invention are important and critical. At high temperatures the cracking catalyst causes cracking of the olefinic feed. At low temperatures the cracking catalyst causes polymerization of the olefins to high boiling polymers. The applicable temperatures constitute that range which lies between these two extremes. The limits of acaaeae temperature, although critical, cannot be stated to lie within definite limits for the general case since the limits depend upon the space velocity, upon the particular olefin fraction treated, upon the particular catalyst used, and to some extent upon the purpose of the treatment. The governing factors are analogous to those in catalytic cracking, which factors are well known and understood. The conditions are adjusted in the known manner and according to known principles such that the temperature is below that afiording cracking of the hydrocarbon mixture, but above that at which substantial polymerization to higher boiling olefins takes place. The contact time is adjusted to decrease the bromine number to a value corresponding approximately to the content of normal olefin in the product. While the critical limits of the applicable ranges of conditions cannot be defined in absolute values for the general case, the following conditions are generally within the critical range and may be considered as approximations of the applicable range:

Cd Fraction C5 Fraction Minimum temperature, O.. 325 308 Maximum tern erature, O 460 425 Minimum LH V 0.3 0.3 Maximum LHSV- 3.0 3.0

(Liquid hourly space velocity--LHSV-is defined terial fed to the reaction zone in this case is still lit) hill

higher depending upon the amount of hydrogen donor material included. The operation is preferably carried out at pressures from atmospheric pressure up to about atmospheres. The indicated liquid hourly space velocities are for substantially atmospheric pressure operation. As the pressure is increased, the liquid hourly space velocity should be adjusted in the known manner to afiord an approximately equivalent contact time.

The contact time (LHSV) is adjusted such that the branched chain olefin or olefins in the feed are substantially completely converted. In practice some isomerization of the olefins usually takes place and as a consequence it is not possible to produce a product completely free of branched chain olefins. However, when the branched chain olefins in the feed have been substantially completely converted only a minor amount of branched chain olefins will be found in the product. The adjustment and control of the contact time (LHSV) may 'be made through correlation with the bromine number. The bromine number, which is easily determined by the lmown methods, is a function of the total olefin content of the sample. Thus, the liquid hourly space velocity may be adjusted such that the bromine number of the product corresponds approximately to the content of normal olefin therein. When this condition pertains, the branched chain olefins (except for the minor residue produced by isomerization as explained above) will have 'been substantially completely reacted; a decrease in the liquid hourly space velocity will cause reaction of the normal olefins; an increase in the liquid hourly space velocity will give an incompletely converted product containing considerable amounts of branched chain olefins, from which product the desired normal olefins cannot be easily separated. When the conditions are properly adjusted the product contains only the above-mentioned minor amount of residual branched chain olefins and the desired normal olefins may be readily separated from the reaction mixture by conventional methods.

The separation of the residual normal olefins from the isoparaflin produced may be effected by any one of a number of methods. In some cases a sharp fractionation may suffice. The preferred method is, however, through extraction of the normal olefins. Any one of the large number of known solvents may be used for this purpose. Examples of a few suitable solvents are sulfur dioxide, furfural, acetone-water, and suliolane. Also, combination processes such as extractive distillation may be applied.

In some cases it will not be desired to recover the normal olefins per se. Thus, the normal olefins in the reaction product may be reacted or converted into a desired product instead of beingseparated. This allows the process of the invention to be advantageously applied for the production of gasoline. For example, the normal olefins may be polymerized or alkylated in situ. Such applications of the process of the invention are described in more detail later in connection with the drawings.

In the present process the branched chain olefin is selectively reacted and the primary reaction product is the corresponding branched chain paraffin. Thus, the process of the invention may, if desired, be considered from the standpoint of this reaction product, i.e. it may be utilized as a means of producing branched chain parafiins. For example, in combination with a dehydrogenation step, it may be utilized to produce (separate) normal butylenes and isobutane from refinery butane-butylene fractions, or, in combination with an olefin isomerization step, the entire normal butylenes may be utilized in the production of isobutane. Details of such applications are explained below in connection with the drawings.

The formation of isoparafiin from the corresponding branched chain olefin in the present process takes place through a self-saturation reaction. In the simple case the necessary hydrogen comes from the conversion of part of the reactant to a carbonaceous residue. This car bonaceous residue is removed from the catalyst by burningin the known manner. As a consequence of this reaction, the yields of product are always less than The yield may be improved, however, by the application of a material which under the conditions will donate hydrogen more readily than the olefinic fraction treated. Cyclohexane, cyclohexene and related hydrocarbons, although known to be good sources of hydrogen, are of no particular value for this purpose. It is found, however, that their polycyclic counterparts such as decahydronaphthalene, tetrahydronaphthalene and related polycyclic hydroaromatic compounds may be advantageously used. Thus, if such material or a fraction containing substantial amounts of such material is available, it may be mixed with the olefinic feed to the reaction zone. In view of the high boiling point of such materials, they may be easily separated from the reaction product and cause no diificulty in the separation of the desired normal olefin. If a large supply of such d material is not available, the recovered material may be hydrogenated in a separate step using a conventional hydrogenation catalyst and free hydrogen and then reused.

Various features of the process of the inven tion and its modes of application will perhaps be better understood upon consideration of the following description of more specific applications. In the description, reference is had to the attacher' drawings wherein process fiows are shown by means of conventional diagrams, and wherein:

Figure it illustrates an application of the process for the separation of a monoolefin from an olefinic hydrocarbon fraction containing the normal olefin in admixture with an isomeric branched chain olefin;

Figure II illustrates an application of the proccan for the production of allrylate gasoline from an olefinic fraction;

Figure Hit illustrates a modified process for the production of normal pentenes and isopentape from refinery pentane-amylene fractions; and

Figure 1V illustrates a modified process for the production of an isoparafidn from a corresponding olefin.

These figures are schematic and do not show all details, as, for instance, provision for removal of the light gases always formed in small amounts in such processes.

Referring to the drawing, Figure l, the oleflnic feed. for instance a refinery butane-butylen iii-action having the following analysis:

Mole

per cent lsobutylene 23 Normal butylenes dill lsobutane 20 lil'orrnal butane 1d entering via line i, is forced by pump 2 through coll. it of heater ll wherein it is heated to the desired reaction temperature, for instance 400 C. The pre-heated charge then passes via line to one or two of the reactors t, l and El. ftlthough only one or two reactors may be used. it is preferable to employ at least three reactors since this allows two reactors to be used continuously while the third is undergoing regeneration. Air or other oxidizing gas for regeneration enters via manifold line it. The spent regeneration gas is removed through manifold line it. Reactors t, l and it are filled with a suitable cracking catalyst such, for example, as pellets oi the synthetic silica-alumina composite cracking catalyst or the treated clay cracking catalyst now in common use. An excellent catalyst can be simply and cheaply prepared by impregnating activated bauxite with silica or boric oxide. The reaction is carried out at a temperature between about 325 C. and 45b" G. and at a pressure of about 30 p. s. i. g. The liquid hourly space velocity is adjusted at about it such that the olefin content of the product in manifold line 9 is about d095, as determined by the bromine number.

The product withdrawn from the reactor via line i? is passed to extractor it. Cooled solvent, for example, sulfolane, is introduced into the top of extractor it via line it] and passes countercurrent to the feed. A substantially saturated product consisting predominantly of isobutane is withdrawn from the top of extractor it via line it. The fat solvent is withdrawn from the bottom of extractor it and passed via pump ill into stripper it. Heat for stripping may be supplied to the stripper or to the feed as by heater ii. The stripped solvent is withdrawn from the bottom of stripper it and recirculated after cooling to the extractor. The stripped fraction consisting essentially of normal butylenes is recovered from the overhead product of stripper it via line it).

In the embodiment illustrated in Figure 11, the process is utilized to produce superior yields of allrylate gasoline having improved volatility. The usual refinery butane-butylene fraction, for instance having the analysis shown above, is suitable for alkylatlon only if a large supply of isobutane is available. In most refineries, however, there is not enough isobutane to balance the olefine. In many cases the excess olefin is therefore polymerized. In the process illustrated, excellent yields of alkylate may be produced from the refinery butane-butylene fractions without resort to extraneous sources of material. Thus. the necessary balance between the olefin and isobutane is established in the feed by the present process. Also, since in the present process the isobutane is produced by selective reaction of the lsobutylene, the alkylate is produced essentially from normal butylenes. This gives a su perior alkylate product. Also, the conditions in the present process may be easilyadjusted to give a minor amount of intermediate boiling isoparaffins which enhance the volatility of the alkylate.

Referring to Figure II, the feed, for example, a refinery butane-butylene fraction such as mentioned above, entering via line M, is commlngled with a hydrogenated fraction rich in hydrogenated polycyclic aromatic hydrocarbons in line it. The mixture is forced by pump it through preheater coil 26 in furnace 25. The feed preheated to about 400 C. passes via line it to one or more of the catalytic reactors 2i, tfi and it. Reactors 2?, 2t and 2d are filled with granules of a solid cracking catalyst, for example, on alumina which is activated and impregmated with 15% by weight B203. The conditions are regulated as described in connection with the operation in Figure I. The product withdrawn via line 30 and containing normal butylenes, isobutylene, a. small amount of gasoline and heavy oil is passed to fractionator 3i wherein the heavy oil is separated as a bottom product which is withdrawn via line (it. This heavy oil is charged to reactor at wherein it is hydrogenated with hydrogen introduced via line 3%. Fresh polycyclic aromatic or hydroaromatic hydrocarbons may also be introduced via line it. Reactor 333 is filled with any one of the many known applicable hydrogenation catalysts. A suitable catalyst by way of example is a pelleted mixture of sulfides of tungsten and nickel. With this catalyst typical conditions by way of example are as follows: temperature-350 C.; pressure- 700 p. s. i. g.; LHSV-l; and an excess of hydrogen. The product passes via line 35 to separator it wherein dissolved hydrogen is separated and withdrawn via line ill. The hydrogenated prodnot is then commingled with the feed and passed to the heater via line 22 and pump 23 as described.

The overhead product from fractionator 3i is passed via line 38 to a fractionator 39 wherein the C4 fraction is separated overhead from a light gasoline fraction which is withdrawn from the bottom via line ill. The overhead C4 fraction is passed via. line M to fractionator t8. Normal butane is removed as a product of the process aseaete via line Alli. Isobutane is removed via line- Bil, cooler lil, surge tank 52, and is passed by pump I53 and line 54 to the alkylation unit. In the alkylation unit 42 normal butylenes and isobutane are caused to react through the agency of a suitable alkylation catalyst. The alkylation .step may be carried out through any of the conventional processes.

passed via line 33 to fractionator M wherein it The alkylated product .is

approximate analysis:

Mole

per cent Isoa nylenes 37 Normal amylenes 28 Isopentane 17 Normal pentane 13 enters via line 6|. This feed is commingled with a mixture of hydrogenated heavy oil and amylenes introduced via line 62. The mixture is passed through coils of heater E i wherein it is preheated to about 350 C. The preheated mixture passes via line 65 to one or more of reactors 65, 6'! and t8. Reactors 66, ill and I58 are filled with granules of a cracking catalyst, for example, the treated clay catalyst produced by the Filtrol Corporation. The temperature may be, for example, 400 C. The liquid hourly space velocity with respect to the olefinic feed may be about 3.9, and the liquid hourly space velocity with respect to the total feed to the reaction zone may be about 8. Under these conditions the branched chain amylenes are not only converted selectively to the corresponding saturated compounds, but

an appreciable amount of isomerization of the normal amylenes to branched chain amylenes takes place. The product leaving the reactors via manifold line 69 passes to a fractionator Ill wherein a heavy fraction containing polycyclic aromatic hydrocarbons is separated. This heavy fraction is removed by line II and passes to reactor 72 wherein it is hydrogenated with hydrogen introduced via line I3. The product passes via line M to a separator I5. Recovered hydrogen is removed by line I6 and recycled or withdrawn as desired. The hydrogenated product containing substantial amounts of hydrogenated polycyclic aromatic hydrocarbons is passed via lines TI and 62 to the feed line wherein it commingles with the feed entering the preheater. If desired, fresh hydrogenated polycyclic aromatics may be introduced with the feed via line 6|.

The overhead fraction from fractionator III is passed to fractionator I8. In fractionator 18 gasoline components produced in the process by a minor amount of cracking and destructive hydrogenation of the heavy recycled stock are separated as a bottom fraction which is withdrawn via line I9. The remainder consisting essentially of C hydrocarbon is passed via line Ill) to extractor BI, wherein it is contacted with a solvent which is selective for olefins, for example, dimethylsulfol-ane. A rafiinate passes overhead via line 82 to a fractionator w. The extract phase is passed via line at tea strippertfi,

d The fraction consisting of extracted olefins (mostly normal amylenes) is recovered overhead via line 86 as a product of the process. The fraction fed to fractionator 83 consists largely of normal and isopentane. The isopentane is removed overhead via line 81 as a product of the process. The normal pentane is removed from fractionator 83 via line 88 and passed through coil 89 of heater 90 wherein it is preheated to a dehydrogenation temperature, for example, 550 C. The preheated fraction in the vapor phase is passed via line QI to one or more of reactors 92 and 93. These reactors are filled with granules of the dehydrogenation catalyst such, for example, as alumina which is activated and impregnated with chromium oxide and/or molybdenum oxide. Manifold lines 96 and 95' are for the introduction and withdrawal of regeneration gas. The product withdrawn from reactor 92 and/or 93 via line 96 contains hydrogen, amylenes and pentanes. This product is passed through a separator 91, separated hydrogen. is passed to the hydrogenation reactor I2 via

lines

98 and 12. The pentane,

amylene product is withdrawn via line E39 and. commingled with the hydrogenated cycled oil in line I52.

In an alternative process where it is desired to produce more normal amylene and less branched chain pentanes, all or a part of the material in line 99 is passed via valved branch line I00 into the feed line to the extractor Ill.

In the modification illustrated in Figure IV, the entire feed, except for the unavoidable losses to coke, etc., is converted into the desired isoparaflln.

Referring to Figure IV, the feed, for example, a refinery pentane-amylene fraction, is charged via line III] and pump III to coil H2 in a heater H3, wherein it is preheated to, for example, 400 C. The preheated feed in line II l is commingled with a fraction from line H5 and the mixture is passed to one or more of reactors Ilii, I II and I I8. These reactors are filled with crack-'- ing catalyst and are operated as described in connection with the other figures to aiford reaction of the branched chain olefins without appreciable cracking or polymerization. The reaction product. passes via line M9 to extractor I22. Extractor I20 and stripper I2I are operated as described in connection with Figure I. The raffinate (paraffinic compounds of the product containing the isoparafdns produced in the reactors .I It, I II and/or H8) is withdrawn as an overhead product of extractor I20 via line I22. The olefinic components of the product (extract) consisting essentially of normal olefins are separated from the fat solvent in stripper II and are removed overhead via line I23, cooler I24 and surge tank I25. This fraction is carried by line I26 and pump I2'I to heating coil I 28 in heater I29 wherein it is preheated to an isomerization temperature, for example, 475 C., and then passed via line I32 to reactor Ii-lI. Reactor I3I is filled with a catalyst efiective for the isomerization of normal olefins to the isoolefins. Any of the known catalysts suitable for this purpose may be used. One suitable catalyst by Way of example is alumina which is activated and has been acidified by a thorough washing with aqueous hydrochloric acid. The reaction product consisting essentially of branched chain olefins and unconverted normal olefins is commingled with the feed in line I I I as described and serves to enrich the feed with isoolefins,

26 thereby increasing the efllciency in reactors Ht,

aceacae iii and lit. The cracking catalyst used in reactors lit, iii and lit generally has an appreciable isomerization ability. Therefore, the entire amount of olefin may be converted by repeated recycling of the normal olefin to these reactors. However, the conditions in reactors I it, i it and i it are not necessarily optimum for olefin isomerization and consequently the application of the separate isomerization reactor iii allows a more eficient process.

The invention claimed is:

i. Process for the production of useful products from C4 fractions containing normal butylenes and isobutylene which comprises treating the C4 fraction in the presence of an added fraction rich in polycyclic hydroaromatic hydrocarbons in the vapor phase with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 325 C. and loll" C. and at a pressure between 1 and atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing the treatment when the bromine number of the resulting product corresponds to the content of normal butylenes in the mixture whereby the said isobutylene is selectively converted to isobutane, separating the product into a heavy oil containing polycyclic aromatic hydrocarbons, normally gaseous products and a gasoline fraction, hydrogenating said separated heavy oil and cycling it to the C4 iced as the added fraction rich in polycyclic hydroaromatic hydrocarbons, subjecting the normally gaseous fraction to an alkylation treatment to product an alkylated product boiling within the gasoline range, and blending the product of alkylation with said separated gasoline fraction to produce a substantially saturated low density stable gasoline having good anti-knock rating and a greater volatility than that of the product oi alkylation alone.

2. Process for the production of useful roducts from hydrocarbon mixtures containing normal and branched chain olefins having from i to about 6 carbon atoms which comprises treating the hydrocarbon mixture enriched in branched chain clef-ins in the vapor phase with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 3%" C. and 450 C. and at a pressure between 1 and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said treatment when the bromine number of the resulting product corresponds to the content of normal olefins in the mixture whereby the said branched chain olefins are selectively converted to the corresponding isoparaiiins, separating the product by solvent extraction into a saturated fraction consisting largely of branched chain paraihns and an unsaturated traction consisting largely of unchanged normal olefins, subjecting said fraction consisting largely oi" normal olefins to a catalytic isomerization treatment to produce a mixture of normal and branched chain olefins rich in branched chain oleilns, and utilizing said isomerized mixture to enrich the above said hydrocarbon mixture with branched chain olefins as above specified.

3. Process for the production of useful products from hydrocarbon mixtures containing normal to i and branched chain olefins having from 4 to about 6 carbon atoms which comprises treating such olefinic feed in the presence of an added higher boiling fraction rich in polycyclic hydroaromatic hydrocarbons and in the presence of added branched chain olefin produced as hereinafter set forth in the vapor phase with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 300 C. and 450 C. and at a pressure between l and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said oleilns, discontinuing said treatment when the bromine number of the resulting product corresponds to the content of said normal olefins in the mixture whereby the said branched chain oleflns are selectively converted to the corresponding branched chain parafilns, separating the product by solvent extraction into a saturated fraction consisting largely of branched chain parafiins and an unsaturated fraction consisting largely oi unchanged normal olefins, subjecting said fraction consisting largely of normal oleflns to a catalytic isomerization treatment to produce a mixture of normal and branched chain olefins rich in branched chain olefins, and treating said mixture in admixture with the olefinic feed as described above.

4. Process for the production of useful products from butane-butylene fractions which comprises treating a butane-butylene fraction in the presence of an added butane-butylene fraction produced as hereinafter specified in the vapor phase with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconiaalumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 325 C. and 450 C. and at a pressure between i and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said treatment when the bromine number of the resulting product corresponds to the content or normal butylenes in the mixture whereby the isobutylene in the mixture is selectively converted to isobutane, separating the product by solvent extraction into a saturated fraction consisting largely of isobutane and unconverted normal butane and an unsaturated fraction consisting largely of unchanged normal butylenes, separating said saturated fraction by fractional distillation into an isobutane fraction and a normal butane fraction, subjecting said normal butane fraction to a catalytic dehydrogenation, and commingling the product of said dehydrogenation with said butane-butylene fraction specified above.

5. The process which comprises contacting a mixture of a straight chain olefin and an isomeric branched chain olefin having from 4 to 6 carbon atoms with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 300 C. and 450 C. and at a pressure between 1 and 10 atmospheres, said 0 conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said contact when the bromine number of the resulting product corresponds to the content of said straight chain ole- 11a in the mixture whereby the said branched ll chain olefin is selectively converted to the corresponding isoparafin, and recovering the said straight chain olefin in concentrated form from the isoparafiln so produced.

6. The process which comprises contacting a mixture of a straight chain olefin and an isomeric branched chain olefin having from 4 to 6 carbon atoms in the presence of an added polycyclic hydroaromatic hydrocarbon with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 300 C. and 450 C. and at a pressure between 1 and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said contact when the bromine number of the resulting product corresponds to the content of said straight chain olefin in the mix ture whereby the said branched chain olefin is selectively converted to the corresponding isoparamn, and recovering the said straight chain olefin in concentrated form from the isoparafiin so produced.

7. A process which comprises contacting a C4 fraction containing substantial amounts of normal butylenes and isobutylene with a cracking catalyst of the group consisting of silica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 325 C. and 450 C. and at a pressure between 1 and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said contact when the bromine number of the resulting product corresponds to the content of said normal butylenes in the mixture whereby said isobutylene is selectively converted l to isobutane, and recovering the said normal butylenes in concentrated form from the isobutane so produced.

8. The process which comprises treating a Ca fraction containing substantial amounts of normal amylenes and branched chain amylenes with a cracking catalyst of the group consisting of sliica-alumina, silica-magnesia, silica-zirconia-alumina and alumina-boria cracking catalysts and the activated clay cracking catalysts at a temperature between 300 C. and 425 C. at a pressure between 1 and 10 atmospheres, said conditions being correlated in the known manner within said ranges to avoid substantial cracking of said olefins, discontinuing said contact when the bromine number of the resulting product corresponds to the content of said straight chain amylenes in the mixture whereby said branched chain olefins are selectively converted to isopentane, and recovering the said straight chain olefins in concentrated form from the isopentane so produced.

HERVEY H. VOGE. GEORGE M. GOOD. BERNARD S. GREEIISF'ELDER.

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

UNITED STATES PATENTS 846,480 France Sept. 18, 1939

Claims

5. THE PROCESS WHICH COMPRISES CONTACTING A MIXTURE OF A STRAIGHT CHAIN OLEFIN AND AN ISOMERIC BRANCHED CHAIN OLEFIN HAVING FROM 4 TO 6 CARBON ATOMS WITH A CRACKING CATALYST OF THE GROUP CONSISTING OF SILICA-ALUMINA, SILICA-MAGNESIA, SILICA-ZIRCONIA-ALUMINA AND ALUMINA-BORIA CRACKING CATALYSTS AND THE ACTIVATED CLAY CRACKING CATALYSTS AT A TEMPERATURE BETWEEN 300*C. AND 450*C. AND AT A PRESSURE BETWEEN 1 AND 10 ATMOSPHERES, SAID CONDITIONS BEING CORRELATED IN THE KNOWN MANNER