US2255275A - Polymerization of refinery unsaturates and preparation of improved motor fuels - Google Patents

Description

Pnemed sepa 9, 1941 y roLyMEmzA'rioN oF REFINERY uusa'ru-` Barns AND PREPARATION or nuPnovEn MOTOR FUELS Eldon E. Stahly, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware Application October 1, 1937, Serial No. 166,752

6 Claims.

The present invention resides in a method for producing gasoline hydrocarbons from normally gaseous hydrocarbons by acid'polymerization of the latter. It is particularly directed to a process for converting mixtures of Cs and C4 oleflns, with or without C5 olens, by the action of sulfuric' acid of suitable strength into liquid motor fuel.

More particularly, it resides in a process in which normally gaseous mixed oleiins of said type are converted into liquid fuel in a single operation.

It has already been proposed to subject hydrocarbon fractions containing mixtures of isoand normal butylene with or withoutv other unsaturated hydrocarbons to the 'action of sulfuric acid of a particular concentration at a temperature between about 150 F. and 300 F. to form Cs hydrocarbons composed of a mixture of di-isobutylene and copolymer of normal and isobutylene. This mixture, eitheras such or preferably after hydrogenation, is a highly desirable constituent of a motor fuel.

A mixture of hydrocarbon polymers, mainly of branched chain structure ranging from Cs to Cio hydrocarbons and isopropyl ether 'and/or isopropyl alcohol, can be obtained by the method described above if the hydrocarbon fraction subjected to the acid .treatment 1contains a mixture of C3, C4, and Cs olefins. Such mixed polymens are preferably obtained in a single operatiorf by subjecting a mixture of Ca, C4, and C5 olefins to the action of sulfuric acid of a concentration ranging from about 55% to about 80% at a temperature ranging from about 175 Ffto about 300 F., and preferably under a pressure suilicient to maintain the normally gaseous hy ,drocarbons inthe liquid state. When the feed stock is free from Cs hydrocarbons, the product will contain-hydrocarbons ranging from Ca to 012+. v

.The process may also be carried out inthe gaseous phase. Due to the fact that the degree of dispersion of these hydrocarbons when in the gaseousphase in sulfuric acid is not as complete' as when they are in the liquid phase, it is preferablewhen carrying-out the reaction in the I 10 knocking characteristics.

(Cl. id-9) gaseous phase, to introduce the normallygaseous hydrocarbons into the reaction zonein the liquid state, the temperature in this'zone being so correlated to the pressure that the hydrocar- 5 bons, upon being dispersed in the sulfuric acid,

are converted to the gaseous phase. vThe hydrocarbon above described methods are suitable for use as motor fuels, and have very However, these polymers are unsaturated, and in many instances it is desirable to hydrogenate them in order to saturate the oleiln double bong; .before ,their use in gasoline. It has been f und that this hy- 15 drogenation also reduces the alcohols and ethers present to the corresponding hydrocarbons, thereby causing a loss in the anti-knocking characteristics of such oxygenated compounds. An

actual loss in yield of product suitable for use in 20 gasoline also results, as isopropyl alcohol and ether are reduced to propane.

. It has now been found that. these losses can be prevented, and improved yields of improved motor fuels may be obtained by carrying out the .process of the present invention. In one speciflc embodiment of the process the isopropyl ether formed is separated from the olefin polymer produced, the latter is hydrogenated wholly or in part, and the isopropyl ether is then reblended with the hydro-polymer and any residual olefin polymer. Other and further objects of this invention and illustrative embodiments thereof will be presented in the following description and in the attached drawing.

-As previously stated, it is preferred, according to the present invention, to operate under a pressure such that the mixture of Cs, C4, and/or C5 hydrocarbons is maintained in the liquid state.

o At the preferred operating temperature of 200 to 225 F., a suitable pressure will be between 400 lbs/sq. in. and 600 lbs/sq. in. It isof course evident that the only upper limit on the pressure which may be employed is that dictated by eccnomcal operation. Under these preferred oper-l poiymers obtained by. the.

pronounced anti-` between 55% and 757 they will vary vidual case.

ating conditions the acidstrength is preferably The effect of propylene on the product is noticeable when the feed stock contains even as little as mole per cent of propylene based on a total feed containing 48.5 mole per cent of olens. Generally a feed having a higher percentage of propylene. Preferably, it should be present in an amount at least equal to the amount of butylenes where these are the only olens in the feed stock. An increase in the ratio of propylene to normal butylene over one to one favors the formation of isopropyl ether. In generaL, it vmay be stated that any feed stock which contains a substantial amount of propylene,together with C4 and/or C5 oleins, is suitable for the process of the present invention.

The feed stock most commonly employed for the process of the present invention is a refinery gas obtained from crude'distillation', cracking, destructive hydrogenation, or other thermal process. These gases may contain as high as 50% of olens composed mainly of propylene, isoand normal butylene with small amounts of the' amylenes. 'I'he remainder of such refinery gases consists of C1 to C5 paraillns and hydrogen. The capacity of the polymerization chamber may be increased by isolating the oleinic constituents from the renery gas by any suitable method, such as by liquefaction of the-Cs to C5 constituents of such gases and the extraction of the olefins from said liquefied fraction by any common selective solvent such as sulfur dioxide. Or, if desired, the C3 to C5 hydrocarbons may be segregated from the lighter constituents.

When the only available feed stock is one mainly composed of C3 and C4 paraillns with or without C5 it to the parailins to olens. This conversion may be either cracking or catalytic dehydrogenation, preferably the latter. A particularly suitable feed stock is one obtained by the cracking or catalytic dehydrogenation of a mixture of propane and isobutane or a naturally occurring mixture of isoand normal butane with propane. 'Ihe former, when thermally decomposed, produces an oleflnlc mixture mainly composed of propylene and isobutylene which, when subjected to the process of the present invention, yields a mixture of olens of particularly highly branched nature, together with isopropyl ether. This mixture, especially when the oleilnic constituents thereof are hydrogenated, is an exceptionally good blending agent for motor fuels.

The reaction time best suited for the process of the present invention may be most readily understood when expressed in liters of liquid hydrocarbon feed perhour per foot of acid height in the polymerization zone. This feed rate may vary between about 1%g liters per hour Per footof acidheight and about I liters per Ahour per foot of acid height with an acid column having a cross sectional area of about 0.05 sq. ft. These specific values are only exemplary, since with acid columns of different cross-sectional area. -They are, however, -indicative of the order offeed rate to be employed and can be readily ascertained for each indi- The-liquid hydrocarbon feed may be introduced into the acid in the polymerization zone` alundum thimble, or thru Jets which impart a it will be desirable to employ paraflins, it ,is necessary to subject a thermal treatment for the conversion of` thru a porous thimble, such as an of course, apparent that the size of the jet suit different total feed 'feed and product is discharged into a y which4 the acid settles to the bottom isfactory results have been obtained with Jets having openings of 0.018" and 0.023". It is,

opening may be chosento rates.

After the separation of the normally liquid constituents from the product issuing from the polymerization zone, a residual gas mixture, which still contains a substantial percentage of C: to Cs olens. may be obtained. This residual gas mixture may be recycled to the fresh feed,

or may be sent thru a second polymerization unit y `of the same type.

When recycling is employed, saturated normally gaseous hydrocarbons build up in the feed. For this reason, it is advantageousfrom time to time to divert therecycled stock to a cracking or catalytic dehydrogenation chamber wherein the saturates are converted to corresponding olens. gas may be diverted to a thermal polymerization unit for the'conversion of normally gaseous paramns intoI hydrocarbons boiling within the'gasoline range. Whencatalytic dehydrogenation is employed, the dehydrogenation chamber is maintained at a temperature ranging from about 950 to 1100 F. and under atmospheric or only slightly elevated pressure. A suitable catalyst for this conversion is one containing, as itsessential catalytic constituent, an oxide or a sulfide, or other compound, of a metal of group VI of the periodic system which is preferably associated with a carrier; such as bauxite, kaolin, alundum,` active carbon, etc., or with a diflicultlyreducible oxide, such as alumina, thoria, silica, etc. When a thermal polymerization unit is employed for processing the recycle gas, it is maintained under a pressure of at least 500 lbs/Sq. in. and under la temperature' between about 900 F. and 1200 F., depending upon the composition of the recycle gas.

Ordinarily the acid in the polymerization zone passes therethru concurrent with the hydrocarbon feed and the mixture of acid, unconverted separator in from which it is drawn off and returned to the reaction chamber. During the process a content of alkyl lhighdegree of dispersion to the liquid feed. Sat- 7 5 sulfates, mainly isopropyl sulfate, is built up in the acid. Up to acertain extent the presence of these sulfates in the acid exerts a beneficial effect upon the equilibrium of the polymerization process. For this reason it may be desirable to add alkyl sulfates to the fresh feed.

. Should the content o f alkyl sulfates in the circulating acid become so high that removal of some or all of these sulfates is desirable, this may be done by arranging in the acid return line a reaction chamber maintained under conditions suitable for the decomposition of these alkyl sulfates. This chamber may be so operated, namely, at a temperature somewhat 'above the temperature employed in the main reaction zone, as

to convert the alkyl sulfates into ethers containing smaliamounts of alcohols. Alternatively a hydrolyzing agent, such as water or an alkali, may be fed into this chamber and the conditions so adjusted in a known manner as to convert the balkyl sulfates into the corresponding alcohols containing small amounts of ether. When this latter method is employed, it is usually necessary to adjust the concentration of the acid before reintroducingv it into the polymerization zone. 4If caustic soda is used as the hydrolyzingagent. it

unnecessary to take measures to remove the resulting sodium acid sulfate or sodium sulfate Alternatively, the recycle from the circulating acid, since the presence of either of these salts is not detrimental tothe polymerizing action of the sulfuric acid.

As previously stated, itis preferable to hydrogenate at least part of the normally liquid oleiinic hydrocarbons obtained as a result of the acid treatment. If these liquid products are free from sulfur,'the hydrogenation is preferably` carried out in the presence of a highly active nickel catalyst, that is a nickel catalyst prepared by the roasting and reduction with hydrogen of a freshly precipitated nickel compound. The nickel so prepared is used to best advantage when disposed on a carrier, such as kaolin, pumice, etc. When such a catalyst is employed, the hydrogenation is generally carried out at a pressure of at least 50 lbs/sq. in. and at a temperature between abouty300 and 600 F.

Should the normally liquid hydrocarbon prod- .uct contain sulfur, it is advisable to employ la hydrogenating catalyst which is immune to poisoning by sulfur. The preferred catalysts of this type are those which have previously been menqtioned -for use in the dehydrogenation of' normally gaseous hydrocarbons. When a catalyst of thisvtype is employed, ed for the hydrogenation is generally somewhat higher than that required for hydrogenation in the presence of a nickel catalyst.

If it is .desired to employ a. nickel catalyst for the hydrogenation operation, measures may be taken to preclude the presence of sulfur in the liquid hydrocarbon feed to the hydrogenation chamber. This is best accomplished Aby scrubbing the normally gaseous hydrocarbons employed as a feed stock to the polymerization chamber with caustic. The e 'nation of sulfur from this feed stock also improves the polymerization stage of the process. Sulfur may often be removed from the normally liquid products by vsuitable fractionation. these products may also be reduced to the necessary extent by caustic washing or by treatment of these products in the vapor phase with a desulfurizing agent, such as bauxite, ferrous sulfide, fullers earth, alumina and the like.

While in the preferred embodiment of the present invention the isopropyl ether is separated from the normally liquid product before the latter is subjected to hydrogenation, this step may be modied. The separated isopropyl ether will always contain a considerable amount of hexylene which is formed in the polymerization chamber and which may be improved as a motor fuel constituent by hydrogenation. The complete separation of these two compounds by fractionation is practically impossible, and it may accordingly be desirable in producing a fuel to remove, prior to the hydrogenation, only so much of the isopropyl ether as can be separated substantially free of hexylene.

This separation of the isopropyl ether from the hydrocarbon polymers may also of course be carried out in any other suitable manner, such-as by treatment of the reaction product with solvents having a selective solvent action between the ether and the hydrocarbons, such as aqueous alcohol.

The products of the process of the present invention, having a highly branched structure and having a boiling range nearly commensurate with that of gasoline, canbe readily converted into a gasoline of high octane number by the addition of the necessary amount of low boiling hydrothe temperature best suitl highly .saturated motor` vention is graphically carbons to properly adjust their vapor pressure, 75

, the liquid state through line I3 which is below C1 hydrocarbons and the addition, if necessary, of certain high boiling compounds to provide a gasoline of the necessary end point. As suitable additions of low boiling point may be mentioned iSO-pentane and butane or iso-butane. When it is necessary to add high boiling hydrocarbons this may be done with a simultaneous improvement in the octane number of the `total blend by the addition of aromatic extracts of heavy naphthas, that portion o the extract which has an end boiling point of about 400 F. being selected. In many instances, however, the product of the process of the present invention has a suiiiciently high end point to make the addition of extraneous heavy hydrocarbons unnecessary.

The nature o the process of the present inillustrated in the accompanying drawing in which the single gure is a front elevation in diagrammatic form of an apparatus suitable for carrying out said process.

Referring to the drawing in detail, I is a feed line for the introduction of Cs to C5 hydrocarbons into the unit; Arranged in lli e I is a compressor 2 `by which the C3 and C5 hydrocarbons are liquefied and pumped thru the system. The liquefied feed stock is fed into polymerization chamber 3 through a porous thirnble 4. Sulfuric acid of suitable strength is fed into chamber 3 at its bottom through line '.i.V

The mixture of sulfuric acid,` unconverted feed and reaction product leaves reaction chamber Y3 through line 6, passes through cooler 1 into a settling chamber 8 provided with an interface indicator 9. The sulfuric acid settles to the bottorn and is drawn offl through line 5, which returns it to the reaction chamber 3. The mixture of normally liquid reaction product and liqueiied normally gaseous unconverted feed leaves separator 3 through line I0, which discharges it into still Il which is maintained under such conditions that' unconverted feed, isopropyl ether, and any' hexylene formed, leavesthe top thereof in vapor form through line I2, and hydrocarbons having seven or more carbon atoms leave the bottom in provided with a valve III and a branched line I5 in which the flow of liquid is controlled by valve I6. With valve I6 closed and valve I4 open, the liquid reaction product is conducted by line I3 to storage tank I1. By suitably controlling valves I4 and I6, part'or all of the liquid product may be conducted by line I5 through heating coil I8 i'nto hydrogenation chamber I9.

Line I5 is provided with a branch 20 through which the necessary hydrogen forfthe hydrogenation of the liquid product is introduced into the hydrogenation chamber.- The product from the lrvdrogenation chamber passes into separator 2I from which the hydrogenated hydrocarbons are drawn olf at the bottom through line 22 by which they are fed to storage tank 23. Excess hydrogen leaves separator 2| through line 24 and may be recycled to the hydrogenation chamber.

The unconverted feed and the products boiling are conducted by line I2 to a. partial condenser higher boiling constituents thereof are liquefied and returned to the top of still II as reflux condensate by line ture leaves condenser 25 through line 21 by which it is fed to cooling coil 28 after the pressure thereon has been suliiciently released by pressure release valve 29'in vline 21. The mixture is then discharged into a separating chamber 30 provided with a liquid level indicator.

25 in which part of the- 26. vThe remainder of the mixisopropyl for hydrolysis, leaves vessel I point just ahead of .this valve, with a branch a reaction chamber 31 which, as previously stated, may be employed for cracking, catalytic dehydrogenation or. thermal polymerization. When this vessel is cracking or catalytic dehydrogenation, the eiliuent therefrom passes through line 3B to a separator 39 from the top of which C2 and lighter hydrocarbons are removed from the system and from the bottom of which C; to C5 hydrocarbons are pumped through line 40 to line 33b.

Line 38 is provided with a valve 4| and with a branch line 42 controlled by a valve 43. When chamber 31 is employed for thermal polymerizal is closed and valve 43 is opened, and from said chamber passes through branch line 42 into separator 44 from which gasoline and heavier hydrocarbons are withdrawn by line 46, and C5 and lighter hydrocarbons pass overhead through line 41 back to line 33.

Line 5 is provided with a valve 48 and a branch line 49 controlled by a' valve 50. When it is desired to remove alkyl sulfates from the circulating sulfuric is opened, and

acid, 4valve 48 is closed, valve 50 the acid, containing alkyl sulfates,

removed from separator 8, is introduced into a' chamber 5| which may be operated as a hydrolyzlng zone, in which event a. hydrolyzingagent is introduced` thereinto through reaction chamber for the production of ethers.

The alcohol or ether, as the case may be, leavesv vessel 5I through line 53 in which it is conducted to cooler 54 and thence to storage chamber 55. Sulfuric acid, which may contain the water added through line 55, goes to a concentrator 51, in any suitable manner, and then through line 58 back to line 5. Line 58 is provided Withan inlet 59 for fresh acid.`-

Tanks 1 1, 23, 32, and 55 are provided respectively lwith outlets 60, 6|, 612, and 63 leading to a commonline 64. the, blending of the products contained in the various storage tanks in any desired proportions.

It is apparent that many changes may be made in the above described apparatus without departing from the scope of the present invention. A

Six runs were made with a three-'foot height of sulfuric acid with a cross-sectional area of 4.9 sq. in. under a pressure of 600lbs./sq. in. The feed was introduced into the acid through a'jet having an internal diameter of 0.018". One of the runs was made zit-.266 F. in the gas phase to determine what eect a change of phase would have on the yield.- Since jet employed for which may be heated l .is not as emcient as that oi.' liquids. the feed inl this 4run was not preheated whereby it was dispersed as liquid and converted to gas in the reactor. 'I'he data for -these runs may be summarized as follows: n

' Run No.

Feed rate, 1./hr 16 16 15 15 l5 Weightpercent acid 50 60 69 69 69 gerperature, Fy 224 215 224 221 v26o ec l Mole percent ethane 0.6 0.6 0.6 0.8 0.8 0 Mole percent propylene 12.5 12.5 12.5 12.8 .12.8 12 Mole percent propane 56.1 56.1 56.1 53.1 53.1 66. Mole percent isobutylene. 3.4 3.4 3.4 3.7 3.7 2. ole percent n-butylenes 7. l 7. l 7. 1 7. 0 7.0 4 Mole percent butanes 20.1 20.1 20.1 22.2 22.2 14. Mole percent Cri- 0.2 0.2 0.2 0.4 0.4 0. Exit gas:

Mole percent ethane an lighter 3.6 1.8 1.8 0.2 Mole percent propylene 11.0 6.9' 6.8 7.2 Mole percent propane 55.4 60.6 60.3 68.6 Mole percent isobutylenes. 2.7 0.4 0.8 0 8 0.6 Mole percent nbuty]enes 6.0 4.9 5.0 3.1 Mole percent butanes 20.8 25.1 25.0 18.3 Mole percent 05+ 0.5 0.3 0.3 2.0 Yield on prop vlene:

Based on product 12.0 4l 65 54 65 Based on olefin reducton 16. 0 94 90 86 75 Yield on total nnsats.:

Based on product 19. 3 31 27 32 Based on'oleiln reduction.. 17.5 52 50 48 45.5 Olelin reductions:

Percent reduction of iso 64H5.. 23 91 94 87 75 Percent reduction of n- CiHs.. 1 8 39 34 30 Percent reduction of propylene 51 52 43 Percent reduction of total uns s 17.5 52 50 48 45.5 Product -It will be noted that with acid the yield was mainly isopropyl alcohol. This .is evident from the. fact that whereas only 45% of the product distilled over at 1'71,'80% distilled over at 183. It is also to. be observed that the gas phase experiment gave a yield comparable to that rate and` acid temperature of phase operation,

obtained with the same feed strength in liquid phase 'at a 224 F. The product of the gas however, was somewhat higher boiling, indicating Thisarrangement facilitates dispersion of gases the presence of higher polymers.

The products ofthe runs made with acid of higher than 50% concentration contained varying amounts of isopropyl ether ranging from about 5% to 10%. of isopropyl alcohol in the various products, not taking into consideration the isopropyl alcohol recovered from the circulating acid, ranged from about 1% to 3%.

The products from and distilled to 329 F.; 75% of the mixture was recovered as overhead. This overhead was hydrogenated in the presence of nickel at 500 F. under a pressure 'of 1600 lbs/sq. in. A 40% blend ofthe hydrogenated product in a 74 octane number straight-run naphtha gave a blending octane number o1' 9 3. A similar blend of the straight-run naphtha with isooctane indicated the blending octane number of the iso-octane to be 92.5. Thus acid treatment thefhydrogenated 'product of the of the C's and C4 cut is about equal to iso-octane as a blending agent for- Runs 3 and 4 were mixed o! the distillation was a 'l0 aqueous solution of normalbutylene. The results were as follows: isopropyl alcohol. In the run itself 1616 grams ot vliquid product was obtained. 1000 'grams o! Run No. isopropyl alcohol was obtained from the spent acid. Thus, the total weight per cent yield o! 47 s product, based on the propylene, was 65% (shown y in the data above) plus 28.6% (yield of alcohol) Poiyiiirligldi: 9/9 or 93.6%. This figure checks'with the figure weigmgmuwmmamm- ...-1 given in theabove table for yield based on Polyvggi gentonisobutylene 191 propylene reduci-dgn- U 1() Percent rdpylenepolymerlzed 58.5 Several analytical d1stlllations were run on Pnobut lg lglllyelggg-z-e-m *gli ai products of polymerization of propane-butane poymmnspectim: y mixtures. The estimates of the compositions o! Pfnit WW 82 85 om N6. fsa o.H.As'rM 85.2 s4. the various products are tabulated below with 02mg Nagfngim man polymer 01.4.4 95. the respective feeds to the polymerization unit y 4 for the several products. The product obtained in Run No. 7 over a reac- Sample No.

1 2 n ya 4 :il

Temp..I- 22's 225 224 221 200 Weight percent acid 69 69 69 69 66 gentil height, reet a a a a 3 M01@ percent 10.11. 3.1 5.4 3.4 3.7 2.2 Mole percent n-CHs... l. 7. 9 0. 7 7. 1 7. 0 4. l Mole percent CiHq 8.6 7. 5 l2. 5 l2. 8 l2. 1 Total 19.0 ne 23.0, am 18.4 Ram: iso-orHB/n-oHS/om 1/2. sla s 1/1. 911.4 i/a 1/a.1 1/1. 0/3. s 1/1. sels. 5 Percent reacted:

s1 87 01 04 ...-15 :nas ai -so 4a 4c 51 se 4s .11. 42/1 107/1 ae/i aan 4.4/1 1.42 1.es/1/1.01 1.15/1/1131 1an/as 1.a2/1/t4 is Cass/0m1- oiefins 12. aa 111.21 1/2. 0 1/1. s 1 4. 1 Percent reduction of unsats... 46 46.5 A 52 50 45.5 Estimates of product:

Percent isopropyl ether 8 l 5 10 10 Percent C+C1 hydrocarbons 14 y'14 ll l5 Percent C; hydrocarbons 62 52 38l 25 Percent C|Cu+hydrocarbons 13 23 38 46 Percent loss i 3- 6 3 4 100.0 100.0 100.0 100.0

The per cent isopropyl ether in the product Y tion period of 132 hours had the following averapparently increases with increasing feed ratio age characteristics; f of CaHe to 04H8. Samples 5 and 3 contain a -considerably higher percentage of material above Product! 1 Sample Smal 60% 243 e. e 70% 1 v.253

90% 350 F. B. aas 34s 95% 359 Percent recovery 88.0 87.0 F. B P. o F 361 .5 Comparative results. obtained by processing a 'gg' 9L;

feed containing propylene and butylenes and one Anmne point o F 103 containing only butylenes respectively. were obtained by treating the respective feeds in a, re-

Ananalytical distillation of this product showed actionchamber having an 1l it. height of 60% 6 5 that, on the average, it contained about 2% of sulfuric acid with a crosslsectional area of 9.6 sopropyi ether. A cut of this product obtained sq. in. The operating temperature was 225 F., by distlling the product to 911.85% overhead the pressure was 425 lbs/sq. in. and the feed yielded, upon hydrogenati'on, a product having rate was 24 liters/hour. The feed was introan octane number of 95.6. The unhydrogenated duced.l into the reaction chamber through a jet product usually contains about 9 and 10 mole having aninternal diameter of 0.023". per cent reacted propylene in the form of ether, In Run'No. 7 thefeed contained 4.9% propylalcohol, and the unsaturated hydrocarbons 06H12. ene, 1'7.l'%isobutylenc, and 26.5% of normal C1H14, and Cel-11e, and higher hydrocarbons. The butyiene. In Run fNo. 8 the feed contained no first traction fromthe distillation of this product propylene, 7.2%"of .isobutylene, and 18.4% o! im? an ethereal odor. The presence of hexylene v hydrocarbon in this first overhead was indicated by its refractive index and boiling point.

'I'he following example illustrates advantages of operation according to the preferred method of this invention. A crude polymer, obtained by co-polymerization of C: and C4 olens and con-'- taining isopropyl ether, was found to have an octane number of 85.6. Hydrogenation of this polymer product to saturate the double bonds produces a saturated product having an octane number of 90.0. But when th'e isopropyl ether is separated before the hydrogenation, the rea fraction containing isopropyl ether and a hymaining polymer being hydrogenated under the same conditions as before, and the isopropyl ether is then reblended with the hydrogenated polymer, the inal blend has an octane number of 93.3'. 'In addition to this increased octane number'the yield isalso greater'in the second case as hydrogenation of isopropyll ether to pro- Dane is avoided.

The experiments described above do not, of course, define the metes and bounds of the present invention. They are complete operations carriad out under various conditions falling ,within the broad ranges of operating conditions heretofore described and esta lished by experiments of a qualitative nature.

It is tobe understood that' while it is preferred to employ, tis a'feed stock in the process of the present invention, one containing propylene and both isoand normal butylene, this process may be practiced successfully on any feed stock containing propylene and any olefin containing 4 or 5 carbon atoms.

The nature and objects of the present invention having been thusdescribed and illustrated, what is claimed as new and useful, and'desired to be secured by Letters Patent is:

1. A process for the production of a motor fuel of high octane number which comprises contacting a mixture the olefin content essentially comprising propylene and at least one other olein of higher molecular weight and having no hydrocarbon constituents containing more than 5 carbon atoms with sulfuricsacid of'a concentration between 55% and 7,5% at a temperature between 175 and 300 F. and under elevated pressure, separating a reaction product predominantly boiling within the gasoline range and cong a minor amount of isopropyl ether from the sulfuric acid, dividing the reaction product into a fraction containing isopropyl ether and a fraction boiling in the motor fuel range, then saturating the double bonds in the said hydrocarbon .fraction with hydrogen.

y ing the hydrogenated containing isopropyl ether.'

containing less than 6 carbon atoms with sulfuric acid under conditions causing vthe formation of a polymerization reaction product predominantly containing hydrocarbon polymers boiling in the motor fuel range and a minor amount of isopropyl ether, removing the reaction product from the sulfuric acid, dividing the reaction product into drocarbon fraction, saturating the double bonds in the said hydrocarbon fraction with hydrogen, and combining the hydrogenated product with the fraction containing isopropyl ether.

3. A process for the production of a motor fuel of high octane number containing isopropyl ether .which comprises contacting a mixture the olefin content essentially comprisingvpropylene and at least one other olefin `of higher molecular weight and having no hydrocarbon constituents containing .more than 5 carbon atoms with sulfuric acid of a concentration between 55% and 75% at a temperature between-175 and 300 F. and under elevated pressure, removing the `reaction product and lunconverted initial material from the sulfuric acid, separating the reaction product from the unconverted initial material, dividing the reaction product into a fraction containing isopropyl ether and a higher boiling hydrocarbon fraction, said`latter fraction constituting the major portion of the reaction product, saturating the double bonds in the said higher boiling hydrocarbon fraction with hydrogen, and combinproduct with the fraction 4. A process according to claim 3 in which the feedstock is a mixture containing C3 and C4 olefins. s

5. A process according to claim 3 in which the said mixture is passed through a body of sulfuric f acid at a rate varying between about 11/2 and '7 propyl ether, and

-2. A process for the production of a motor fuel reaction product.

liters/hr./ft. of acid height of a cross-sectional area of about 0.05 sq. ft.

6. In the process for the production of motor fuel of high octane number by contacting a hydrocarbon mixture, the olefin content of which essentially comprises propylene and atleast one olefin of higher molecular weight containing less than six carbon atoms'per molecule, with sulfuric acid under conditions causing the formation of a polymerization reaction product predominantly containing hydrocarbon polymers boiling in the motor fuel range and a ininor amount of isoremoving the reaction product, from the sulfuric acid mixture, the improved steps comprising separating afraction containing .substantially all of the isopropyl ether from the and hydrogenating at least a reaction product portion of the substantially isopropyl-ether-fx'ee ELDoN E. s'rAHLY.

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