US2952614A - Optimum reforming of light virgin naphthas - Google Patents

Description

United States Patent OPTlNIUlVI REFORMING OF LIGHT VIRGIN NAPHTHAS Kenneth Earl Draeger, Charles Newton Kimberlin, Jr., William Floyd Arey, Jr., and Judson Mattox, all of Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed May 1, 1957, Ser. No. 656,355

'15 Claims. (Cl. 208-79) The present invention relates to the reforming of hydrocarbons and particularly to an improved method for upgrading naphtha fractions to produce high octane number motor fuels in high yields.

Hydroforming is a well known and Widely used process for upgrading hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range to increase their octane numbers and to improve their burning or engine cleanliness characteristics. In hydroforming the hydrocarbon fraction or naphtha is contacted at elevated temperatures and pressures and in the presence of hydrogen or hydrogen enriched process gas with solid catalytic materials under conditions such that there is no consumption of hydrogen and ordinarily there is a net production of hydrogen in the process. A variety of reactions occur during hydroforming including dehydrogenation of naphthenes to the corresponding aroomatics,

hydrocracking of paraflins, isomerization of straight chain parafiins to form branch chain parafiins, dehydrocyclization of paraflins and isomerization of compounds such as ethylcyclopentane to form methylcyclohexane which is readily converted to toluene. In addition to these reactions some hydrogenation of olefins and polyolefins occurs and sulfur or sulfur compounds are eliminated by conversion to hydrogen sulfide or to catalytic metal sulfides making the hydroformate burn cleaner or form less engine deposits when used as the fuel in an internal combustion engine.

Hydroforming is usually applied to a rather wide boiling range naphtha i.e., to one having a boiling range of from about 125 F. to about 400430 F. It has been known that the lower boiling naphthas are not substantially improved by hydroforming processes as ordinarily conducted. The extensive report entitled An Appraisal of Catalytic Reforming in Petroleum Processing for August 1955, for example, states at page 1174: Optimum reformer utilization is obtained by not using feed stock constituents boiling much below 200 F. which do not contribute greatly to increased octane. during reforming as these merely take up reformer capacity better used for high boiling materials more susceptible to octane upgrading. In view of the continuing demand for more and higher octane number gasolines, however, it is becoming increasingly important to upgrade naphthas to even higher octane levels and in this connection it is becoming essential to improve the octane number of these lower boiling naphtha fractions.

It is the object of this invention to provide the art 6 with an improved method for reforming or upgrading naphthas.

It is also the object of this invention to provide a simple and efiective method for upgrading petroleum naphthas boiling in the range of from about 110 to about 375 F. to form high octane products in high yields.

It is a further object of this invention to upgrade light petroleum naphthas boiling in the range of 150- 225 F. in a combination operation to form high octane products in high yields. a

Patented Sept. 13, 1960 These and other objects will appear more clearly from the detailed specification and claims which follow.

It has now been found that petroleum naphtha fractions can be converted into high octane number products with an exceptionally high yield advantage by separating the naphtha feed with molecular sieves having pore openings of about 5 A. into a non-normal paraffin fraction and a normal paratfin fraction, subjecting the non-normal paraflin fraction to hydroforming with platinum-containing catalysts at 25-400 p.s.i.g. or with a M00 on alumina catalyst at 100-400 p.s.i.g., preferably about 200 p.s.i.g., to increase the octane number thereof, subjecting the normal paratfin fraction to hydroisomerization with a metal catalyst or a Friedel-Crafts type catalyst or aromatizing treatment with a molybdic oxide on zinc aluminate spinel, chromia-alumina, chromia-titania catalyst or the like and combining the resultant products or blending either or both with other motor fuel fractions to form higher octane gasolines. In a preferred embodiment the conversion product of the normal paraffin fraction is treated with molecular sieves of the 5 A. type to separate a non-normal paraflin fraction which is passed to product blending and a normal paraflin fraction which is recycled to the hydroisomerization or the aromatizing step. By this particular combination of process steps it is possible to obtain naphtha products of about octane number at as much as 10% higher yields than can be obtained by the best reforming of the total naphtha. Moreover by proceeding in accordance with the preferred embodiment, it is possible to obtain naphtha products that are essentially free of normal paraflin constituents.

It has, of course, been known for some time that certain zeolites both naturally occurring and synthetic, and sometimes termed molecular sieves have the property of separating straight chain from branched chain hydrocarbon isomers as well as from cyclic and aromatic compounds. These zeolites have innumerable'pores of uniform size and only molecules small enough to enter the pores can be absorbed. The pores may vary in diameter from 3 or 4 A. to 15 A. or more but it is a property of these zeolites or molecular sieves that any particular product has pores of substantially uniform size.

The scientific and patent literature contains numerous references to the adsorbing action of natural and synthetic zeolites. Among the natural zeolites having this sieving property may be mentioned chabazite. A synthetic zeolite with molecular sieve properties is described in US. Patent 2,442,191. Zeolites may vary somewhat in composition but generally contain the elements silicon, aluminum and oxygen as well as an alkali metal and/or an alkaline earth metal e.g. sodium and/or calcium.-

US. Patent 2,522,426 describes a synthetic molecular.

sieve zeolite having the formula 4CaO.Al O .4SiO A large number of other naturally occurring zeolites having molecular sieve activity, i.e. the ability to adsorb a straight chain hydrocarbon and exclude or reject the branch chain isomers and aromatics because of differences in' molecular size are described in an article entitled Molecular Sieve Action of Solids appearing in Quarterly Reviews, vol. III, pages 293 to 320 (1949) published by the Chemical Society (London). I

Although it has in the past been proposed to effect the separation of straight chain hydrocarbons from isoparaffins and aromatics, it has been found that the particular combination of process steps disclosed herein produces an exceptionally high yield advantage in the conversion of naphtha fractions. Moreover, by proceeding in accord ance with the preferred embodiment of this invention, it is possible to producenaphltha products essentially free f-norn1al paraflin constituents. l

Reference is made to the accompanying drawing which diagrammatically illustrates a flow plan in accordance with the present invention.

Referring to the drawing, 10 is the naphtha feed inlet line through which wide boiling range or narrow cut, for example a light naphtha boiling in the range of from about llO to about 250 F. or a 200-350 boiling range heavy naphtha is supplied to the system. The naphtha feed, preheated to a 'sufliciently high temperature to vaporize it,fo r example, to temperatures of 200 400 F. is chargedto molecular sieve treatment zone 11. The naphtha feed is passed preferably in vapor phase through the adsorption zone or tower. The adsorbent, any natural or synthetic zeolite of the molecular sieve type heretofore described and having pore diameters of about A.vunits is arranged in any desired manner in the adsorption zone or tower 11. A suitable 5 A. molecular sieve may be prepared as follows: A solution of 600 g. of granular sodium metasilicate (composition 29.1 Weight percent Na O, 28.7 weight percent SiO 42.2 weight percent H O) in one liter of water is placed in a burette. A second solution of 370 g. of sodiumaluminate in 538 ml. of water is placed in a second burette. The two solutions are added dropwise', with vigorous stirring over a period of two hours to 510 ml. water containing a little NaOH to give an alkaline'solution at a temperature of 190 F. A slight excess of the metasilicate solution over the aluminate solution is maintained during the addition. At the endof the addition, heat is removed and stirring is continued for minutes. The mixture is filtered and washed. The precipitate, sodium alumina silicate is 4 A. sieve.

' To prepare the 5 A. sieve, 35 g. of the wet filter cake is stirred at room temperature for one hour in 600 g. of a'20% calcium chloride solution. The mixture is filtered, washed and then dried at 135 C. The dried product is calcined at 850 F. for four hours. The adsorbent may, for example, be arranged on trays or 'packed'in the adsorption zone or vessel with or without supports. Conditions maintained in the molecular sieve treatment in the adsorption zone or tower are flow rates of 0.1 to 5 v./v./hr., temperatures of about 200-400 F. and pressures from atmospheric pressure to several p.s.i.g. With molecular sieves of the indicated size of pores, the normal paratfins contained in the feed are readily adsorbed while the isoparafiins, naphthenes and aromatics are not adsorbed but pass overhead from the molecular'sieve treatment zone and are passed through transfer line'12 into platinum hydroformer 13.

l The rafiinate from the molecular sieve treatment or naphtha fraction essentially free of normal paraffins is hydroformed in reactor 13 in contact with a hyd'roforming catalyst of the platinum-alumina or molybdic oxidealumina type. Suitable catalysts of the first type are those containing 0.01 to 1.0 weight percent platinum or 0.1 to 2.0 weight percent palladium dispersed upon a' highly pure alumina support such as is obtained from aluminum alcoholate in accordance with U.S. Patent 2,636,- 865 or from an alumina hydrosol prepared by hydrolyzing aluminum metal with dilute acetic acid in the presence of very small, catalytic amounts of mercury. A suitable catalyst comprises about 0.1 to 0.6 weight percent platinum widely dispersed upon alumina in the eta phase prepared by hydrolyzing aluminum amylate, aging the hydrolyzate to convert it to beta alumina trihydrate, drying and calcining and having a surface area of about 150- 220 sq. meters/ gram. A preferred catalyst for fluidized solids operation is one. comprising a mixture of a platinum catalyst concentrate consisting essentially of 0.3 to

2.0 weight percent platinum on alumina microsphel'es.

4 .7 formed by spray drying an alcoholate alumina hydrosol prepared in accordance with U.S. Patent 2,656,321 and mixed with suflicient unplatinized alumina to form a catalyst composition containing about 0.01 to 0.2 weight percent of platinum. Suitable molybdic oxide-alumina catalysts are those containing about 5 to 15 weight percent M00 dispersed upon activated alumina, alumina;gel or preferably silica stabilized adsorptive or activated alumma.

The pressure in the hydroforming reaction zone 13 should be in the range of about -400 p.s.i.g. and is generally less, than about 125 p.s.i.g. preferably about 50 p.s.i.g. when hydroforming a narrow boiling, light naphtha cut with a platinum catalyst." When hydroforming a wide cut or heavy naphtha cut it is preferable to maintain a pressure of about 200 p.s.i.g. when using a molybdic oxide-alumina catalyst and about 250-350 p.s.i.g. when using a platinum-alumina catalyst. The temperature of the catalyst bed should be in the range of from 800-975 F. and is preferably within the range of 875-950 F.

The naphtha feed is preheated to temperatures in the range of from 900-1050 F., preferably about 975- 1000. F. preparatory .to charging .to the hydroforming reaction zone 13. Hydrogen or hydrogen-rich process or about 1000-3000 standard cu. ft./barrel of naphtha culating hot flue gases,

recycle gas is preheated to 900-1300 F. preferably about 1200 F., preparatory to charging to the hydroforming reaction zone. Theamount of recycle gas employed may vary from about 500-5000 and is preferfablly ee If desired,-the naphtha and hydrogen-rich gas maybe, heated together in which event the preferred preheat tem-' per'ature isin the range of from 900-1000 F. f In addition to preheating the naphtha feed and recycle gas, the additional heat load in hydroformer 13 may be supplied by the sensible-heat of the regenerated catalyst in the fluidized solids operations or by circulating reactor catalyst through a heating zone or by arranging heating: coils in the catalyst bed or jacketing the reactor and cirmercury, Dowtherm, or the like therethrough. The naphtha feed is maintained under'. these reaction conditions for a period sufficient to increase its octane number from 85 to about 100 Research octane" number clear.

The hydroformate and process gases are removed from the reaction zone, passed through suitable catalyst recovery equipment, if desired-or necessary, and then passed through suitable heat exchanger and condenser equip-- mentQand thence to a gas liquid separator 14. The high octane number hydroformate is withdrawn from separator 14 by a line 15 and is passed to' storage or blending or is used directly as a high octane number motor fuel. The normally gaseous products are removed from separator 14 and are either recycled to the hydroforming reaction zone 'or utilized in another conversion zone as described below.' V

' When hydroformer 13 is operated with platinum catalysts at pressures below about 200 p.s.i.g., and particularly at the preferred pressure of 50 p.s.i.g. for light naphtha cuts, carbonaceous deposits form upon the catalyst particles and it is necessary periodically to regenerate the catalyst. This may be aflected as required by burning carbonaceous materials fiom the catalyst with oxygen-containing 1200 F., preferably at'1000-1100 F. The regenw erated or carbon free catalyst can advantageously be treated with air or' oxygen-enriched gasat temperatures. of 900-1100 F. for from about one to four hours; It is also preferred to treat the regenerated catalyst particles with chlorine gas or a mixture of chlorine gas and air inorder to reactivate the catalyst, restore its chlorine. content,- and-redisperse or breakup thelarge platinurn' crystallite's that are formed during use of the catalyst.'

V The chlorinepartial pressuremay be in the range of from about 0.00110 2 atmospherespreferably about 0.01;; it etme r e q y t hlerine ,supp edmay;

gas at temperatures of about 900-.'

. '5 be in the range of 0.1 to 2.0-weight percent preferably about 0.5 weight percent based on the catalyst. The chlorine treatment may be carried out for periods of from about 15 seconds to 1 hour preferably about 1 to 15 minutes.

When hydroformer 13 is operated with molybdic oxidealumina catalysts regeneration is also required but this is done in an entirely conventional manner whether in fixed, moving or fluidized bed.

When the molecular sieves in the adsorption or treatment zone 11 becomes saturated with normal paraflins as may be readily determined by conventional means such as refractive index, gravity or spectrographic analysis of the effluent, the flow of naphtha feed to the adsorption zone is stopped and the desorption cycle or regeneration of the sieves begins. Desorption is effected by passing an olefin-containing gas preferably one containing a substantial proportion of propylene. For example, cracked refinery gases containing a major proportion of propylene and minor proportions of ethane and propane is a very satisfactory stripping gas. The stripping gas preheated to temperatures of from about ZOO-350 F. is passed through the exhausted bed of molecular sieves, the olefins in the stripping gas serving to displace the normal parafiins from the sieves. The desorbed normal parafins and excess stripping gas are discharged from the molecular sieve treatment zone 11 through line 17 and are cooled or condensed and passed into gas-liquid separator 18. The gaseous materials are rejected via line 19 and the normal paraflins from the original naphtha feed are withdrawn via line 20 and passed to normal paraflin conversion zone 21. Desorption can also be effected with hydrogen or hydrogen-rich recycle gas or by increasing the temperature or lowering the pressure on the bed or by a combination of two or more of these expedients.

The normal paraflins are converted in reaction zone 21 under conditions which are particularly suited to the upgrading of normal parafiins, for example, under hydroisomerizing conditions or under aromatizing conditions. For example, the normal paraflins may be eflfectively isomerized if contacted with aluminum chloride or other Friedel-Crafts type catalyst or weight percent nickel on silica alumina or 0.5 weight percent of platinum on silica-alumina at temperatures of about SOD-750 F., preferably about 600700 F. and at pressures of from about 100 to 500 p.s.i.g. It is desirable to maintain a high hydrogen partial pressure in the conversion zone during the isomerizing treatment and such a hydrogen atmosphere may be readily provided by withdrawing hydrogen-rich gas from separator 14 via line 22. Alternatively the normal parafiins may be subjected to aromatization by contacting the same with a catalyst con- 1 sisting essentially of about weight percent molybdic oxide dispersed upon zinc aluminate spinel or with chromia-alumina or chromia-titania catalysts containing i about 5 to 40 weight percent preferably about 25 weight percent chromia at pressures below 150 p.s.i.g. preferably at about 50 p.s.i.g. and at temperatures of from 850- 1050 F. The normal parafiin conversion products are withdrawn from reactor 21 via line 23, cooled and condensed and passed to gas-liquid separator 24. Gaseous a products are withdrawn by line 25 and passed through compressor 26 and are recycled to the hydroformer 13 via line 27. The liquid products are withdrawn by a line 28 and may be passed if desired directly to high j octane product blending or storage.

It is preferred, however, that the liquid products from the paraffin conversion zone be subjected to a molecular sieve treatment in order to separate the normal paratfin constituents therein. Accordingly, it is preferred to pass the liquid products via line 29 into molecular treatment zone 30 which, similarly to zone 11, is charged with a natural or synthetic zeolite or molecular sievehaving pore diameters of about 5 Angstrom units. Products cssentially free of normal parafiins are takeir overhead from zone 30 via line 31 and are passed to product blending or storage. In this way the product obtained is essentially free of normal paraflins. When the molecular sieves are completely saturated with normal paraflins they are regenerated similarly to the sieve material in zone 11 as by the supply of a desorbing gas preferably a propylene rich gas thereto via line 32. The desorbed normal paraifins are recycled via line 33 to the normal paraflin conversion zone 21. 7

It is noted that the drawing is entirely diagrammatic and that the hydroformer 13 as well as the normal paraflin conversion zone 21 can be operated fixed bed, moving bed, or as fluidized solids operation. The latter is to be preferred in any operation in which frequent regeneration of the catalyst is necessary. It is further noted that while the molecular sieve treatment zones are illustrated, as single vessels, it will ordinarily be con: venient to provide these vessels in pairs so that one vessel may be regenerated while the other is kept on stream. It is also within the scope of this invention to provide a guard chamber containing molecular sieves of 4 Angstrom units or smaller pore size upstream from the molecular sieve treatment zone 11 as well as zone 30 in order to remove water vapor or sulfur compounds which might have a tendency to lower the adsorptive capacity of the molecular sieves for normal parafiins.

The following examples areillustrative of the present invention:

Example 1 A light virgin naphtha boiling in the range (5% to of 162 F. to 191 F., having an API gravity of 67.9, a Research clear octane number of 66.3 obtained from West Texas crude oil is separated into a normal parafiin fraction and a normal paraflin-free fraction by treatment with a molecular sieve adsorbent which is se-. selective for the removal of normal paraffins from branched chained paraflins and cyclic hydrocarbons. This treatment is conducted by passing the vaporized naphtha through a column of sieve at atmospheric pres sure at a temperature of about 240 F. The flow of naphtha vapor over the sieve is continued until the ca pacity of the sieve for adsorbing normal paraflins is reached. The unadsorbed portion comprising the normal parafiimfree fraction is obtained'in a yield of 76 vol. percent and has a Research clear octane number of 82. The adsorbed normal parafiins are recovered from the sieve by passing propylene gas over the sieve at about 240 F. The propylene displaces the normal parafiins from the sieve. The normal parafiin fraction, which is Obtained in a yield of 24 vol. percent, comprises about 75 vol. percent of normal hexane and about 25 vol. per: cent of normal heptane. The normal parafiins and the non-normal paraffin traction separated as described in this example are subsequently treated further 'as described in Examples 2 to 5.

Example 2 The normal paraffin fraction separated as in Example 1 is isomerized by contacting with a catalyst comprising 5% nickel deposited on a silica-alumina cracking catalyst at a pressure of 350 p.s.i.g., a temperature of 650 F., a feed rate of 1 vol. of feed per vol. of catalyst per hour in the presence of 4 mols of added hydrogen per mol of hydrocarbon. The isomerized product is freed of unconverted normal paraifins by contacting with molecular sieves in the manner described in Example 1 and the unconverted normal parafiins are recycled to the isomerization zone to obtain substantially complete conversion. The isomerized parafiius have a Research clear octane number of 77.2 and are obtained in a yield of 97.3 vol. percent based on the normal parafiin feed to the isomerization zone. The isomerized paraflins obtained froni the complete isomerization of 24 volumes of norm-a1 paraflins are blended with 76 volumes of the non-normal obtain in 99.4 vol. percent yield, based on the original naphtha feed has a Research clearoctane number of 81.

For comparison hydroforming the original naphtha feed oyer'platinum catalyst at a pressure of 50 p.s.i.g. to a Research clear octane number of 81 gives a yield of only 84 vol. percent. xampl 3 p The normal paraflin fraction'obtained as in Example 1 is aromatizedby treatment with a catalyst comprising 10% M deposited on a ZnA1 O spinel base at a pressure of p.s.i.g., a temperature of l050 F., at a feed rate of 0.35 weight of feed'per-hour per weight of catalyst, in the presence of 2 mole of added hydrogen per mol of hydrocarbon. The aromatized product is obtainedin a yield of 59.4 vol. percent based on normal paraflin feed and hasa Research. clear-octane number of 93." The aromatized product obtained from 24 volumes of normal-paraflins is blended with 76 volumes of the non-'normal-paraflin fraction from Example 1. This blend is obtained in a yield of 90.5 vol. percent basedIon the original light virgin naphtha feed and has a Research clear octane number of 84. For comparison hydroforming thelight virgin naphtha. feed with platinum catalyst at-a pressure of 50 p.s.i.g. to a Research clear octane number of 84 gives a yield of only 82 vol. percent.

Example 4 The normal parafiin free fraction obtained as in Example l is hydroformed by contacting with a catalyst comprising 0.6 weight percent platinum deposited on v alumina at a pressure of 50 p.s.i.g., at a temperature of 900 F. in the'presence of 2000 cubic feet of added hydrogen per barrel'at a feed rate of 2.4 weights of feed per hour per weight of catalyst. The hydroformed product having a'Research clear octane number of 90 is obtained in a. yield of 83 vol. percent based on the non-normal paraflin feed. The 90 octane'number hydroformate obtained from 76 volumes of the non-normal parafl'in fraction is blended with the isomerized product obtained as in Example 2 from 24 volumes of the normal paraflins. This blend, which is obtained in a yield of 86.5 vol. percent based on the original light virgin naphtha feed has a Research clear octane number of 86.9. For comparison hydroforming the light naphtha with platinum catalyst at'50 p.s.i.g. to a Research clear octane number of 86.9 gives a yield of only 79.6 vol. percent.

The 90 octane number hydroformate 76 volumes of the normal paraffin-free fraction is blendedwith the aromatized product obtained as in Example 3 from 24 volumes of normal paraflins. This blend obtained in a yield of 77.4 vol. percent based on the original light virgin naphtha feed and has a Research clear. octane number of 90.5. For comparison hydro- !forming the light virgin naphtha feed with platinum catalyst at a pressure of .50 p.s.i.g. to a Research clear octane number of 90.5 gives a yield of only 76.2 vol. percent;

7 Example 5 V The normal paraflin-ree flaction obtained as in Ex ample l is hydroformed by contacting with a catalyst comprising 0.6 weight. percent platinum deposited on alumina-at a pressure of 50 p.s.i.g., at a temperature of 900 F. in the presence of 2000 cubic feet of added hydro'gen per barrel at a feed rate of 1.3 weights of feed per hour per weight of catalyst. The hydroformed prodnot having a Research clear octane number of 98 is obtained in a feld of 70.8 vol. percent based on the non-normal parafiin fraction feed. V s The 98 octane number hydroformate obtained from .76 volumes of the normal parafiin-fi'ee fraction is blended with the isomerized product obtained as in Example 2 from124 volumesof the normal fparaflin fraction. 1.

obtained from 7 blend, which is obtained in a yield of 7 7.2 val. percent based on the original light virgin naphtha feed, has a Re search clear' octane number of 93.0. For comparison hydroforming the light virgin naphtha in the presence of platinum catalyst at 50 p.s.i.g. to a Research clear octane number of 93.0 gives a yield of only 73.2 vol. percent.

The 98 octane number hydroformateobtained from- '76 volumes of the normal parafin free fraction is blended with the aromatized product obtained as in Example 3 from 24 volumes of the normal paraffin fraction. This blend, which is obtained in a yield of 68.1 vol. percent based on the original light virginnaphtha, hasfa Re search clear octane number of 97.2. For comparison hy-' droforming the light virgin naphtha with platinum catalyst at 50 p.s.i.g. "to a Research clear octane number of 97.2 gives a yield of only 66.4 vol. percent. a

Example 6 I A straight-run naphtha having'a boiling range of 206- 335 R, an API gravity of 57.3, and a Research octane number of 48.8 was hydroformed at 200 p.s.i.g., and 900 F. over a 10% MoO A1 0 catalyst using 4900 s.c.f./b. of recycle gas which contained 69.5% H Feed rate (w./hr./w.) was'varied to give hydroformates of various octane levels, including 85 and Research octane number. T

In a separate operation, the same straight-run naphtha feed was separated 'into a normal parafiin fraction (24%) and a non-normal fraction (76%). The non-normal paraflin fraction was hydroformed, in the 'same manner as described above, to octane levels including 85 and 95 Research clear. The normal paraifin fraction was aromatized over a chromia-alumina catalyst at atmospheric pressure, 1000 F., and with 2000 s.c.f.' H /b. This aromatic product was then blended with the hydroformate produced from the non-normal fraction from sieve treating. The following tabulation summarizes data obtained at various octane levels and shows considerable yield advantages for the combination operation with sieve separation.

The invention as described herein is a continuationin-part of our co-pending application Ser. No. 588,000, filed on May 29, 1956.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood, however, that this invention is not limited thereto since numerous variations are possible without departing from the scope of the following claims.

What is claimed is:

l. A method for upgrading naphtha fractions which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed,

recovering a stream of naphtha. feed vapors essentially 4 free of normal paraflins, contacting this paraflin-free feed stream with a hydroforming catalyst at 25-400 p.s.i.g. at

temperatures of 800-975 F. for a period sutlicient to 1 raise the octane number of this stream to from about 85-100 Researchoctane number, desorbing the normal paraflins from the molecular sieves withan olefin gas o a g a m jo r t o pf rq yl nei ra t yj 9 converting the normal paraflins to higher octane number components and blending the normal paraflin conversion products with other gasoline components to form a high octane number motor fuel.

2. A method for upgrading light naphtha fractions boiling in the range of from about 110-250 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a'bed of molecular sieves having pore diameters of about Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraflins, contacting this parafiinfree feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of 800-975" F. for a period suflicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal paraflins from the molecular sievm with an olefin gas containing a major proportion of propylene, separately converting the normal paraflins to higher octane number components and blending the normal parafiin conversion products with other gasoline components to form a high octane number motor fuel.

3. A method of upgrading naphtha fractions boiling in the range of from about 200-350 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal parafiins, contacting this paraflin-free feed stream with a hydroforming catalyst at 150-400 p.s.i.g. at temperatures of 800-975 F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal parafi'ms from the molecular sieves with an olefin gas containing a major proportion of propylene, separately converting the normal parafiins to higher octane number components and blending the normal parafiin conversion prodnets with other gasoline components to form a high octane number motor fuel.

4. -A method for upgrading light naphtha fractions boiling in the range of from about 110-250 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraflins, contacting this paraflinfree feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of 800-975 F. for a period sufiicient to raise the octane number of this stream V to from about 85-95 Research octane number, desorbing the normal paraflins from the molecular sieves with an olefin gas containing a major proportion of propylene, separately aromatizing the normal paratfin to higher octane number products and blending the latter with the product formed by the treatment of the paratfin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel.

5. A method for upgrading naphtha fractions boiling in the range of from about 200-350" P. which comprises vaporizing the naphtha feed, passing the naphtha feed .vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal paraflins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal parafiins, contacting this paraflin-free feed stream with a hydroforming catalyst at 150-400 p.s.i.g. at temperatures of BOO-975 F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal parafllns from the molecular sieves with an olefin gas containing a major proportion of propylene, separately aromatizing thenorm'al parafiin to higher octane number products and blending the latter with the product formed by the treat:

'10 ment of the parafin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel.

6. A method for upgrading light naphtha fractions boiling in the range of from about l10-250 P. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal paraflins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraflins, contacting this parafiinfree feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of BOO-975 F. for a period suflicient to raise the octane number of this stream to from about -95 Research octane number, desorbing the normal paraffins from the molecular sieves with an olefin gas containing a major proportion of propylene, separately aromatizing the normal parafiin to higher octane number products, contacting the reaction products from the aromatizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal paraflin-free conversion products from the unconverted normal parafiins and blending the said normal paraffin-free conversion products With the product formed by the treatment of the paraflin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel.

7. A method for upgrading naphtha fractions boiling in the range of from about ZOO-350 P. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraflins, contacting this parafiin-free feed stream with a hydroforrning catalyst at 150-400 p.s.i.g. at tem peratures of 800-975 F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal paraflins from the molecular sieves with an olefin gas containing a major proportion of propylene, separately aromatizing the normal parafiin to higher octane number products, contacting the reaction products from the aromatizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal parafiinfree conversion products from the unconverted normal parafiins and blending the said normal paratfin-free conversion products with the product formed by the treatment of the paratfin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel.

8. A method for upgrading light naphtha fractions boiling in the range of from about -250 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraflins, contacting this paraflinfree feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of 800-975" F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal paraflins firom the molecular sieves With a cracked refinery gas containing a major proportion of propylene, separately aromatizing the normal paraifin to higher octane number products, contacting the reaction products from the aromatizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal parafiin-free conversion products from the unconverted normal paraflins, blending the said normal paraflin-free conversion products with the product formed by the treatment of the parafiin-free feed stream in contact with the platinum catalyst thereby forminga high octane number motor fuel, desorbing the 11 normal parafiins from the molecular sieves used for the treatment of the aromatization products with a cracked refinery gas containing a major proportion of propylene, and recycling the desorbed normal paraffins to the aromatization treatment.

9. A method for upgrading naphtha fractions boiling in the range of from about 200350 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha teed vapors essentially free of normal paratfins, contacting this paraffin-free feed stream with a hydroforming catalyst at 150-400 p.s.i.g. at temperatures of BOO-975 F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal parafiins fiom the molecular sieves with a cracked refinery gas containing a major proportion of propylene, separately aromatizing the normal paraffins to higher octane number products, contacting the reaction products from the aromatizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal paraffin-tree conversion products from the unconverted normal parafiins, blending the said normal paraflin-free conversion products with the product formed by the treatment of the paraflin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel, desorbing the normal paraffins from the molecular sieves used for the treatment of the aromatization products with a cracked refinery gas containing a major proportion of propylene, and recycling the de'sorbed normal paraflins to the aromatization treatment. 7

- 10. A method for upgrading light naphtha fractions boiling in the range of from about 110-250 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal paraifins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraifins, contacting this paraffinfree feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of 800-975 F. for a period suflicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal paraflins from the molecular sieves with a cracked refinery gas containing a major proportion of propylene, separately isomerizing the norinal paraflin to higher octane number products and blending the latter with the product formed by the treatment of the paraffin-free feed stream in contact with the platinum catalyst thereby forming a high octane number motor fuel. a

11. A method for upgrading naphtha fractions boiling in the range of from about 200-35 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about Angstrom units which selectively adsorbs normal paraflins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraffins, contacting this paraflin-free feed stream with a hydroforming catalyst at 150-400 p.s.i.g. at temperatures of 800-975 F. foraperiod sufficient'to raise the octane number of this stream to form about 85-95 Re search octane number, desorbing the normal paraflins from the molecular sieves with a cracked refinery gas containing a major proportion of propylene separately isomerizing the normal parafi'in to higher octane number products and blending the latter with the product formed by the treatment of the paraffin-free feed stream in con tact with the platinum catalyst thereby forming 'a high octane number motor fuel. i 12.-A method for upgrading light naphtha fractions boiling in the range of from about 110-250 which 12 comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diametersof about 5 Angstrom units which selectively adsorbs no al paraflins from the naphtha feed,recovering"a stream of naphtha feed vapors essentially free of normalparaflins, contacting this paraflinfree'feed stream with a platinum alumina catalyst at 25-125 p.s.i.g. at temperatures of 800-975 F. for a period suflicient to raise the octane number of this stream to from about -95 Research octanenumbendesorbing the normal paraifins from the molecular sieves with a cracked refinery gas containing a major proportion of propylene, separately isomeriz ing the normal paraffin to higher octane number products, contacting the reaction products from the isomerizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal parafiin-free conversion products from the unconverted normal paraflins and blending the said normal paraffin-free conversion products with the product formed by the treatment of the paraflin-free feed stream in contact with the platinum catalyst thereby forming ahigh octane number motor fuel. 1 t W p 13. A method for upgrading'naphtha fractions boiling in the range of from about ZOO-350 F. which comprises vaporizing the naphtha feed, passing the naphtha feed vapors through a bed ofmolecular sieves having pore diameters of about'S Angstrom units which selectively adsorbs normal paratfins from the naphtha feed, recover ing a stream of naphtha feed vapors essentially free of normal paraffins, contacting this paraffin-free feed stream with a hydroforming catalyst at. 150-400 p.s.i.g. at tem- 3 pe'ratures of 800-975" F. for a period suflicient to raise j the octane number of this strea'm'to'from about 85-95 1 Research octane number, desorbing the normal paraflins 1 from the molecularisieves with a cracked refinery gas con- 1 taining a major proportion of '1 propylene, separately isomerizingthe normal paraflin to higher octane number products, contacting the reaction products from the isomerizing treatment with molecular sieves having pore diameters of about 5 Angstrom ,units to separate normal paraffin-free conversion products from the unconverted normal parafiins and blending the said normal paraffin free conversion products with the product formed by the treatment of the paraifin-free feed'stream in contact with the platinum catalyst thereby forming a high octane num ber motor fuel. i

14. A method for upgrading light naphtha fractions boiling in the range of from about -250 F. which comprises vaporizing the naphtha feed, passing .the naphtha feed vapors through a bed of molecular sieves having pore' diameters of about 5 Angstromrunits which selectively adsorbs normal paraflins from the naphtha feed, recovering a stream of'naphtha feed vapors essentially free of normal parafiins, contacting this paraifin-free feed stream with a platinum alumina catalyst at 25-125 p.s .r.g. at temperatures of 800-975 F. for a period sufficrent to raise the-octane number of this stream to from about 85-95 Research octane number, desorbing thenormal paraflins from the molecular sieves with a cracked refinery .gas containing a major proportion of propylene, separately rsomeri zing the normal paraflin to higher octane number-products, contacting the reaction products from the isornenzmg treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate norma1..paraflin-free conversion products from the un-' converted normal parafiins, blending the said normal paraffin-free conversion products with the product formed by the treatment of the paraffin-free feed stream in contact with the platinum catalyst therebyforming a high octane number motor fuel, desorbing the'normal paraflins from the molecular sieves used for the treatment of thei isomerization productswith a'crackedrefinery gas conraining a major proportion of propylene, and recycling thedesor'bed normal parafi'ms to the. isomerization treat ment.

15. A method for upgrading naphtha fractions boiling in the range of from about 200-350 F. which comprises vapon'zing the naphtha feed, passing the naphtha feed vapors through a bed of molecular sieves having pore diameters of about 5 Angstrom units which selectively adsorbs normal parafiins from the naphtha feed, recovering a stream of naphtha feed vapors essentially free of normal paraffins, contacting this paraffin-free feed stream with a hydroforming catalyst at 150-400 p.s.i.g. at temperatures of 800-975 F. for a period sufiicient to raise the octane number of this stream to from about 85-95 Research octane number, desorbing the normal paraflins from the molecular sieves with a cracked refinery gas containing a major proportion of propylene, separately isomerizing the normal paraflin to higher octane number products, contacting the reaction products from the isomerizing treatment with molecular sieves having pore diameters of about 5 Angstrom units to separate normal par- References Cited in the file of this patent UNITED STATES PATENTS 2,651,597 Corner et a1 Sept. 8, 1953 2,818,449 Christensen et al Dec. 21, 1957 2,818,455 Ballard et a1. Dec. 31, 1957 2,849,504 Kang Aug. 26, 1958 2,886,508 Hess et al May 12, 1959

Claims (1)

1. A METHOD FOR UPGARDING NAPHTHA FRACTIONS WHICH COMPRISES VAPORIZING THE NAPHTHA FEED, PASSING THE NAPHTHA FEED VAPORS THROUGH A BED OF MOLECULAR SIEVES HAVING PORE DIAMETERS OF ABOUT 5 ANGSTROM UNITS WHICH SELECTIVELY ADSORBS NORMAL PARAFFINS FROM THE NAPHTHA FEED, RECOVERING A STREAM OF NAPHTHA FEED VAPORS ESSENTIALLY FREE OF NORMAL PARAFFINS, CONTACTING THIS PARAFFIN-FREE FEED STREAM WITH A HYDROFORMING CATALYST AT 25-400 P.S.I.G. AT TEMPERATURES OF 500-975*F. FOR A PERIOD SUFFICIENT TO RAISE THE OCTANE NUMBER OF THIS STREAM TO FROM ABOUT 85-10 RESEARCH OCTANE NUMBER, DESORBING THE NORMAL PARAFFINS FROM THE MOLECULAR SIEVES WITH AN OLEFIN GAS CONTAINING A MAJOR PROPORTION OF PROPYLENE, SEPARATELY CONVERTING THE NORMAL PARAFFINS TO HIGHER OCTANE NUMBER COMPONENTS AND BLENDING THE NORMAL PARAFFIN CONVERSION PRODUCTS WITH OTHER GASOLINE COMPONENTS TO FORM A HIGH OCTANE NUMBER MOTOR FUEL.

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