US3166490A

US3166490A - Combination process for upgrading gasoline fractions

Info

Publication number: US3166490A
Application number: US239914A
Authority: US
Inventors: Harry D Evans
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1962-11-26
Filing date: 1962-11-26
Publication date: 1965-01-19
Anticipated expiration: 1982-01-19

Description

Jan. 19, 1965 H. D. EVANS 3,165,490

COMBINATION PROCESS FOR UPGRADING GASOLINE FRACTIONS Filed Nov. 26, 1962 GASOLINE BLENDING ARONATIC SEPARATION DEPENTANIZER DEHYDROGENATION ZONE INVENTOR= HARRY D. EVANS BY A W X HIS ATTORNEY DEHEXANIZER in order to provide a balanced gasoline.

ited States Patent Office 3,l%,4 Patented Jan. 19, 1965 3,166,490 (IGMBTNATIQN PRUCE FGR UPGRADING GASOLINE FRACTTGNS Harry 1). Evans, Galdand, Calif, assignor to Shell Oil Company, New York, N.Y., a corporation of Deiaware Filed Nov. 26, 1962, fier. No. 239,914 16 Qlaiins. (til. 208-66} This invention relates to production of high octane gasoline fractions. More particularly, this invention relates to an integrated sequence of steps for efiecting the reforming and isomerization of hydrocarbons to produce high octane gasoline components and aromatics.

Catalytic reforming is a well known and now widely used process for converting low octane hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range into hydrocarbon mixtures having a higher octane rating. Fractions employed as the usual reforming feeds comprise a mixture of varied and complex hydrocarbons having a wide range of molecular weight and varying constructural configurations such as parafiins, isoparaffins, naphthenes, alkyl naphthenes, aromatics, alkyl aromatics and the like. When these hydrocarbon compounds are contacted with a reforming catalyst, the reactions which take place are varied and are strongly dependent on the particular type of compounds, particular catalyst, temperature, pressure, and other process conditions. Among these reactions are hydrocracking, aromatization, cracking, isomerization, cyclization, dehydrogenation, hydrogenation-and the like. Thus, it is difficult, if not impossible, when treating the usual complex feed mixture to control the degree of any individual reaction or reactions to provide a specific product distribution. Therefore, the impossibility of establishing operating conditions which provide an optimum conversion of each compound in the reforming feed makes it necessary to carry out the conventional reforming process under conditions which provide, instead, the best average or overall conversion of the feed components to give a product of relatively high octane number.

At first, octanerequirement could be met by reforming under relatively mild conditions wherein the predominant reaction is dehydrogenation of naphthenes to aromatics and consequently yield loss was relatively low. The development of high compression automotive engines in recent years has caused the octane requirement of the automotive industry to spiral upwards to an octane number level approaching 100 and higher. As a result, reforming severity has been increased considerably with concomitant loss in yield of product. Along with requirements for higher octane has come increased demand for gasoline. Thus, it has become a critical problem of refiners to produce high octane gasoline in large volume with maximum efficiency and with a minimum of complicated and involved apparatus and equipment.

Moreover, it has become increasingly'necessary to convert low boiling hydrocarbons into higher octane products As a consequence, increasing consideration has been given to isomerization of the low boiling hydrocarbons, which conversion process heretofore has been seldom used except for the production of isoparafiins from normal paraflins for the production of aviation gasoline. Although many and varied isomerization processes are known, a difficulty encountered by the refiner has been in adapting a particular isomerization process with its specific limitations into an overall processing scheme for converting low octane hydrocarbons into high octane gasoline components. Another difficulty has been inability to achieve the desired separation of hydrocarbons for particular conversion processes because of limitations in hydrocarbon separation methods. The process of the present invention provides a highly integrated and efficient process forconverting low octane materials into high octane gasoline components.

In addition to producing high octane gasoline for motor fuel, the refining industry has also become a major producer of aromatic hydrocarbons such as benzene, toluene and xylene for use in chemical and related industries. One of the factors leading to this result is that rapidly increasing demand for aromatics has far outpaced the ability of the coal tar industry, until recently the primary source of such aromatics, to produce them. The availability of the catalytic reforming process, which produces reformates rich in aromatics, has also been an important factor. The fact that the aromatics have a high octane rating and boil in the gasoline boiling range again points out the necessity for highly efficient processing to produce both aromatics and high octane gasoline. The present invention produces such highly efiicient processing.

In accordance with a preferred embodiment of the present process, a hydrocarbon feed such as straight-run gasoline is fractionated to separate a C and lighter fraction containing benzene and a cyclohexane and a heavier fraction. The cyclohexane and heavier fraction, is subjected to catalytic reforming. The low boiling fraction is passed to a treating zone to remove substantially all the benzene by means of a solvent selective for aromatics and is then passed to a low temperature isomerization zone where normal hexane, and normal pentane if desired, is converted into branched hydrocarbons by means of a Friedel-Crafts catalyst. The reformed product, is fractionated to remove C and lighter hydrocarbons, is subjected to a solvent extraction to recover an aromatic extract. The selective solvent used in the isomerization feed extraction is also used in the reformate extraction. The rafiinate can be blended into gasoline or can be fractionated to recover a C frac tion which is isomerized. The extract can be used with the isomerizate as a blending component for high octane gasoline or can be processed to recover aromatics for sale.

It will-be noted that the present invention provides an integrated combination process involving low temperature isomerization, catalytic reforming and aromatic extraction. While many integrated combination conversion processes have been proposed heretofore, such as the combination of isomcrization and reforming, such processes frequently have certain disadvantages. For example, it is known to reform C and heavier fractions, the reformed product being fractionated to separate C and lighter fractions which are combined with other C fractions and subjected to high temperature, isomerization using, for example, a noble metal catalyst and hydrogen produced in the reforming process. Hydroisomerization with noble metal catalysts is generally conducted at temperatures between about 650 F. and 800 F. However, at the high temperature isomerization equilibrium is less favorable to "in detail in connection with the accompanying drawing wherein the sole figure shows a flow diagram which illustrates the combined process of the invention.

Referring to the drawing, straight-run gasoline introduced through line 1 is fractionated in the dehexanizer 2 to separate an overhead fraction comprising normal hexane and lighter hydrocarbons and a bottom fraction comprising cyclohexane and higher boiling components. ()peration of the dehexanizer will depend to a certain extent upon whether benzene is to be produced as a chemical or whether an aromatic rich fraction is to be produced as a high octane premium gasoline component. In the manufacture of high octane gasoline components, the dehexanizer will be operated to remove overhead as much of the normal hexane as possible while leaving methylcyclopentme, benzene and cyclohexane in the bottoms fraction. In maximizing the production of benzene for chemical sales, it is advantageous to operate the dehexanizer to remove overhead as much of the methylcyclopentane as possible, the methylcyclopentane being converted in the isomerization zone to cyclohexane which is recovered and passed to the dehydrogenation zone. In either case, because of the close boiling temperatures of the various hexane components and because of azeotrope formation, the overhead fraction from the dehexanizer will include a small percentage of benzene and methylcyclopentane.

The bottoms fraction, comprising cyclohexane and higher boiling hydrocarbons, withdrawn from dehexanizer 2 through line 3 is subjected to dehydrogenation, such as catalytic reforming, in zone 4. While the process of the invention is described with reference to catalytic reforming, which is widely practiced in industry with platinum type catalysts, it is to be understood that the term reforming includes processes for the dehydrogenation of naphthenes to aromatics, such as the dehydrogenation of C C naphthenes with tungsten-nickel-sulfide or other catalyst. While reforming zone 4 is indicated as a single zone, it is to be understood that this system will comprise heaters, heat exchangers, a series of reaction zones, usually 3 or 4, coolers, receivers and the like. The reforming is effected at a temperature from about 800 F. to 1,000 F., at a pressure from about 50 to 1,000 pounds per square inch, a liquid hourly space velocity from about 0.5 to 10, and in the presence of hydrogen at a mole ratio to hydrocarbon of from about 0.5 to 20. Any suitable reforming catalyst can be utilized and preferably comprises a composite of alumina and platinum, the platinum being in a concentration of from about 0.01 to about 5% by weight of the catalyst. More particularly, a composite of alumina, platinum and combined halogen is preferred, the platinum being in a concentration of from about 0.1 to about 3% and the halogen being in a concentration of from about 0.2 to about 3% by weight of the final catalyst. The halogen preferably is fluorine and/ or chlorine. Tungsten/ nickel/ sulfide, a well known dehydrogenation catalyst employed in the dehydrogenation of C C and C naphthene fractions to aromatics can also be used if desired. The catalyst may be in the form of granules of irregular size and shape but is preferably in the form of particles of rather uniform size and shape, such as are obtained by pilling, extruding and the like.

Reformate from the reforming zone in line 5 is fractionated in the column 6 which can be operated as a lebutanizer but is preferably operated as a depentanizer to remove C and lighter components overhead via line 7. Aromatics are recovered from the reformate in an extraction system which comprises extraction, extract stripping, and solvent recovery zones. The C and heavier reformate withdrawn from the depentanizer via line 3 is passed to extraction zone 9, where the reformate is contacted, preferably countercurrently, with a solvent selective for aromatics introduced via line 10. Any suitable solvent selective for aromatics can be used although preferred solvents are the alkylene glycols such as diethylene'glycol, dipropyleneglycol, or sulfolane solvents such as sulfolane and/or substituted sulfolane such as methyl and/or dimethyl sulfolane or mixtures thereof.

The countercurrent extraction is conducted at a slightly elevated temperature depending on the particular solvent used. With a glycol solvent, temperature is usually not more than 300 F. and is preferably between 250 and 300 F. Whereas the sulfolane extraction temperature is above the solidification point of the sulfolane/water mixture and preferably is between F. and 250 F. The ratio by weight of solvent to feed to be extracted is generally between 3:1 and 10:1 for glycol type solvents and preferably between 4:1 and 8:1. When using solvents of the sulfolane type, these ratios are generally between 2:1 and 5:1 and preferably are between 1.621 and 4: 1.

A rafr'inate phase predominately non-aromatic hydrocarbons is withdrawn from one end of the extraction zone via line 11. The extract phase withdrawn from the extraction zone 9 via line 12 is passed to stripper column 13 Where non-aromatic compounds and usually some light aromatics are removed overhead and recycled to the extraction zone via line 14. The stripped extract is then passed via line 15 to solvent recovery column 16 to separate the aromatics from the selective solvent which is returned to the extraction zone via line 10. Aromatics removed overhead from the solvent column via line 17 can be processed further to remove benzene, toluene, or xylene for sale or can be used as a high octane blending component in motor gasoline. When the extract, is to be used as a gasoline blending component, stripping zone 13 can be operated as a simple flash zone or, if desired, by-passed.

The light straight-run C fraction from dehexanizer 2 is passed via line 18 to extraction zone 19. In extraction zone 19, the light hydrocarbon fraction is contacted countercurrently with an aromatic selective solvent such as sulfolane which is the same as the solvent used in the reformate extraction zone. Because of the lower aromatic content of the feed, usually about 1 to 5% by weight aromatics, the solvent to feed ratio used in the extraction zone 19 is somewhat different than the ratio used for high aromatic content reformate in extraction zone 9. Solvent to feed ratios of 1/1 to 4/1, preferably 1.5/1 to about 3/ 1 are used in extraction zone 19. Extraction temperatures and other operating conditions are similar to those in extraction zone 9.

Extract phase Withdrawn from extraction zone 19 can be passed via line 20 directly to the reformate extraction system where it can be introduced to extraction zone 9, stripping zone 13, or solvent recovery zone 16 via

lines

21, 22, and 23, respectively. Advantages to be derived from a specific routing of the extract phase are governed to a certain extent by the overall operation desired, for example, whether operations are being conducted for high octane gasoline blending components, for aromatics recovery per se, whether reformate ralfinate is isomerized, and the like. The extract phase from extraction zone 19 contains benzene and a rather high proportion of light parafiins. Passing the extract phase to stripping zone 13 has the advantage that benzene recovery is facilitated although the light parafiins removed overhead and introduced to extraction zone 9 are more difiicult to recover. The light parafiins are substantially all recovered in the rafiinate stream in line 11. As will be described below, C parafiins can be separated from the raflinate and isomerized.

The extract phase from extraction zone 19 is preferably passed to extraction zone 9. This has the advantage that solvent circulation rates are lowered with consequent savmgs in utility requirements, although benzene recovery is slightly reduced. Removal of light parafiins into the raflinate in line 11 is facilitated, however. Light paralfins in the extract phase from zone 19 can be retained as isomerization feed by passing the extract phase via line 24 to a separate stripping zone 25. Light parafiins stripped from the extract phase are returned to zone 19 while the stripped extract phase is removed though line 27. To increase benzene recovery, stripped extract is passed to solvent recovery zone 16 rather than to extraction zone 9.

The rafiinate from extraction zone 19 can be treated,-

e.g., by a water wash, in facilities not shown to remove traces of solvent. Treated rafiinate having an aromatic content less than 0.5% by Weight and preferably less than 0.1% byweight, together with C and/or C fractions if desired, introduced through line 34, is passed to isomerization zone 36 via line 35. The raffinate will include methylcyclopentane, which is desirable in an isomerization feed since it is converted to cyclohexane which can be recovered from the isomerizate and dehydrogenated.

Cyclohexane is converted to benzene more easily than methylcyclopentane in the dehydrogenation unit.

While isomerization zone 35 is illustrated as a single zone, it is to be understood that this system will comprise one or more reaction zones, catalyst separation and recovery facilities, heat exchangers, coolers, caustic neutralizers, and the like. In isomerization zone 36, the hydrocarbons are subjected to a low temperature process similar to the process described in Oil and Gas Journal, No. 13, page 151, April 3, 1961. In brief the hydrocarbon is passed with hydrogen and HCl at a slightly elevated temperature such as 150250 F. into a reaction zone where it is contacted with a Friedel-Crafts type catalyst such as a molten salt mixture comprising aluminum chloride and antimony chloride. The concentration of aluminum chloride in the molten salt mixture is from about 1 to by weight. After phase separation from the catalyst, usually within a section of the reactor itself, the isomerizate flows to a catalyst removal column for separation of dissolved catalyst by simple fractionation. The recovered catalyst is pumped from the catalyst removal column back to the reactor while the isomerizate is taken overhead, condensated and then charged to an HCl stripper column where the acid gas is removed and recycled to the reactor.

In the isomerization of C and C hydrocarbons, it is generally preferred to include a minor percent of hydrogen in the reaction zone to suppress cracking. The hydrogen can be obtained from the catalyst reforming zone, or, if desired, from extraneous sources. In the isomerization reaction, a portion of the catalyst will react with feed impurities and/ or intermediate reaction compounds to form a sludge which is insoluble in hydrocarbon. Sludge is removed by contacting a portion of the catalyst with a hydrocarbon stream, such as the feed, to dissolve active catalyst components therefrom, the insoluble sludge being separated from the hydrocarbon by phase separation and being withdrawn continuously or periodically as necessary.

The isomerizate can be passed to gasoline blending via line 37 or all or a portion of the isomerizate can be passed via line 38 to fractionate column 39 wherein a methylcyclopentane and heavier fraction is removed as a bottom stream via line 40 and passed to reforming zone 4. Overhead from fractionation zone 39 can be passed to gasoline blending via line 37 or can be passed to a further fractionation zone, not shown, to recover unconverted normal paraffins which are recycled to the isomerization zone.

The raffinate withdrawn from extraction zone 9 can be passed directly to gasoline blending, usually lower octane regular grade gasoline in contrast to high octane premium gasoline. All or a part of the rafiinate can be passed via line 29 to fractionation zone 30. In fractionation zone 30 a C and heavier fraction is removed via line 31l'to gasoline blending while a C fraction is removed overhead. The C fraction from fractionation column 30 can be passed to extraction zone 19 via line 32 or to isomerization zone via line 33 depending on the aromatic content of the C fraction. Since rafiinates obtained by the extraction of reformate fractions generally contain olefins in a minor amount, it is generally desired to hydrogenate at least the C raflinate fraction prior to isomerization.

While the process of the invention has been described with reference to splitting a straight-run gasoline feed in a dehexanizer, it is to be observed that this split between reforming feed and isomerization feed can beeffected by various other fractionation schemes which are frequently available in a refinery. For example, the reforming feed fraction may be prepared on a crude oil distillation unit Whereas the light hydrocarbon components of the crude oil are recovered and processed through such fractionating columns as a debutanizer, depentanizer, deisopentanizer, deisohexanizer and the like.

The following illustrates the process of the invention for application on a commercial scale. A light reforming feed fraction corresponding to deisohexanizer bottom fraction, such as in line 3 of the drawing, is charged to a catalytic reforming zone at a rate of 14,810 b./d. This reforming feed has an API gravity of 64.2, a boiling range of approximately 158/255 F. and contains 6% v. aromatics, 42% v. naphthenes and 52% v. paraffins. Reforming operating conditions are 250-300 p.s.i.g. reactor outlet pressure, 2-3 LHSV, 4-4.5 H /oil mol ratio, and temperatures in the range of 900980 F. Stabilized reformate having an approximate boiling range of 290 F. and containing 41.4% v. aromatics is charged to an extraction column at the rate of 12,200 b./d. The reformate is extracted in countercurrent operations with 28,865 b./ d. of sulfolane, a solvent selective for aromatics. A raffinate phase containing 1.1% v. aromatics is withdrawn from the extraction zone at the rate of 7,801 b./d., while 6,742 b./ d. of hydrocarbon (77.8% aromatics) contained in the extract phase is passed to a stripping column.

A C hydrocarbon fraction containing 3.9% v. aromatics and corresponding to dehexanizer tops fraction, is passed to a separate extraction zone at the rate of 3,241 b./d. and contacted countercurrently with 3,571 b./d. of sulfolane. A rafiinate containing 0.1% v. aromatics is passed to isomerization reactor at the rate of 2,538 b./d. for isomerization by means of aluminum chloride antimony trichloride molten salt catalyst. The extract phase from the isomerization extraction zone comprises 703 b./d. hydrocarbon having an aromatic content of 17.6% v. This extract phase together with the extract phase from the reformate extraction column is passed to a stripping column such as column 13 in the drawing wherein 2,343 b./d. of light hydrocarbon are removed overhead and recycled to the reformate extaction column. This light recycle contains approximately 12% v. aromatics. Bottoms from the stripper comprising solvent and extract are then passed to a solvent recovery column to recover 5,102 b./d. of product aromatics containing 99.8% v. aromatics lean solvent recovered as a bottom stream from the solvent recovery column is returned to the extraction zones.

I claim as my invention:

1. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexanc and Cr, and heavier hydrocarbons, passing reformate product to an aromatics recovery system wherein the reformate is separated into an aromatic rich extract and a paraflinic raffinate by means of a solvent selective for aromatics, contacting a light normal paraifin fraction containing normal hexane and benzene in an extraction zone with said solvent selective for aromatics to obtain an aromatic rich extract phase and a normal parafiin raffinate phase, passing the extract phase to said aromatics recovery system to recover said benzene, and isomerizing the normal paraffin rafiinate with a Friedel-Crafts catalyst to obtain an isomerizate product rich in isoparaffins.

2. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, contacting reformate product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatics extract phase and a first paraitinic rafiinate phase, stripping light parafiins from the first extract phase in a stripping zone, separating stripped extract into aromatic extract and solvent, contacting a normal paraffin fraction containing normal hexane and benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a second rafiinate phase, passing the extract phase to said stripping zone, and isomerizing the second rafiinate phase with a Friedel-Crafts catalyst to obtain an isomerizate product rich in isoparaifins.

3. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, contacting reformate product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first paraifinic rafiina'te phase, stripping light paraffins from the first extract phase in a stripping zone, separating stripped extract into aromatic extract and solvent, contacting a normal parafiin fraction containing normal hexane and benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a second rafiinate phase, passing the extract phase to the first extraction zone, and isomerizing the second rafiinate phase with Friedel-Crafts catalyst to obtain an isomerizate product rich in isoparaffins.

4. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, contacting reformate product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first paraffinic rafiinate phase, stripping light parafiin from the first extract phase in a stripping zone, separating stripped extract into aromatic extract and solvent in a separation zone, contacting a normal hexane fraction containing benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a second raifinate phase, passing the extract phase to said separation zone, and isomerizing the second raffinate phase with a Friedel-Crafts catalyst to obtain an isomerizate product rich in isoparafiins.

5. The process according to claim 1 wherein said Friedel-Crafts catalyst is a molten salt comprising aluminum chloride and antimony trichloride.

6. A process according to claim 1 wherein the selective solvent is sulfolane.

7. The process according to claim 1 wherein the selective solvent is an alkylene glycol.

8. The process according to claim 1 wherein the normal parafiin rafiinate phase, contains less than 0.5 by volume aromatics.

9. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and O; and heavier hydrocarbons, contacting reformate product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first parafiinic rafiinate phase, stripping light paraifins from the first extract phase in a stripping zone, separating stripped extract into aromatic extract and solvent, contacting a normal paraffin fraction containing normal hexane and benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and second raffinate phase containing less than 0.5% by volume benzene, passing the extract phase to said stripping zone, and isomerizing the second raflinate with a Friedel-Crafts catalyst comprising aluminum chloride and antimony trichloride to obtain an isomerizate product rich in isoparaffins.

10. A process for upgrading light straight-run gasoline which comprises in combination fractionating straight-run gasoline into a normal hexane and lighter fraction containing benzene and a heavy fraction comprising C naphthenes and higher boiling hydrocarbons, catalytically reforming the heavy fraction to produce an aromatic rich reformate, contacting reformate with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first paraffinic rafiinate phase, contacting the normal hexane fraction with said solvent selective for aromatics in a second extraction zone to obtain a second extraction phase and a second rafiinate phase containing less than 0.5 by volume benzene, passing said first extract phase and second extract phase to a stripping zone to strip light paraffins from the extract phase, separating stripped extract phase into aromatic extract and solvent which is recycled to said first extraction zone and second extraction zone, and isomerizing the second rafiinate phase with a Friedel- Crafts catalyst to obtain an isomerizate product rich in isoparafiins.

11. A process for upgrading light straight-run gasoline which comprises in combination fractionating said straight-run gasoline into a light normal hexane fraction containing benzene and a heavy fraction comprising C naphthenes and higher boiling hydrocarbons, catalytically reforming the heavy fraction to produce an aromatic rich reformate, contacting the reformate with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first parafifinic rafiinate phase, contacting the normal hexane fraction with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a second rafiinate phase containing less than 0.5 by volume benzene, passing the first extract phase and the second extract phase to a stripping zone to strip light parafiins from the extract, separating stripped extract into aromatic extract and solvent which is recycled to the first extraction zone and second extraction zone, separating the first railinate phase into a C and lighter rafiinate containing less than 0.5 benzene and isomerizing said C and lighter raffinate and said second raffinate phase with a Friedel-Cra-fts catalyst to obtain an isomerizate product rich in isoparafiins.

12. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy fraction comprising cyclohexane and C and heavier hydrocarbons, passing reformate product to an aromatic recovery system wherein the reformate is contacted in a first extraction zone with a solvent selective for aromatics, to obtain a first aromatic rich extract phase and a first parafiinic raffinate phase, contacting a saturated C fraction in a second extraction zone with said solvent selective for aromatics to obtain a second aromatic rich extract phase and a second raifinate phase, said solvent being the selective solvent which is used in the reformate aromatics recovery system, passing the second extract phase to the aromatic recovery system wherein aromatics are separated from solvent, isomerizin-g the second raffinate phase by means of a Friedei-Crafts catalyst to produce an isomerizate rich in isoparafiins, and blending at least a portion of the isomerizate with at least a portion of the aromatic extract product to produce a high octane motor fuel.

13. A process for upgrading ligh straight-run gasoline which comprises in combination fractionating said gasoline into a light normal hexane fraction containing benzene and heavy fraction comprising C naphthenes and higher boiling hydrocarbons, catalytically reforming the heavy fraction to produce an aromatic rich reformate, extracting the normal hexane fraction with a solvent selective for aromatics to produce a paraffinic rafilnate having an aromatic content less than 0.5% by volume and a C aromatic extract phase, isomerizing the parafiinic raffinate with Friedel-Crafts catalyst in an isomerization zone to produce an isomerizate rich in isoparaffins, separating aromatics from the catalytic reformate in an aromatic recovery zone by means of said solvent selective for aromatics, the reformate extract phase and the C extract phase being passed to a fiash zone whereby low boiling aromatics and parafiins are removed from the extract phase, and recovering an aromatic rich product from the extract phase, solvent recovered from the extract phase being recycled to extraction zone, and blending at least a portion of the isomerization product with at least a portion of the aromatic product to produce a high octane number motor fuel.

14. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, passing reformate product to an aromatics recovery system wherein the reformate is separated into an aromatic rich extract and a paraffinic raffinate by means of a solvent selective rfor aromatics, contacting a light normal paraffin fraction containing nor mal hexane and benzene in an extraction zone with said solvent selective for aromatics to obtain an aromatic rich extract phase and a normal paraffin raflinate containing less than 0.5 by volume aromatics, stripping light paraffins from the extract phase and passing stripped extract phase to said aromatics recovery system, and isomerizing the normal parafiin rafiinate phase with a Friedel-Crafts catalyst to obtain an isomerizate product rich in isoparafiins.

15. A process for upgrading gasoline fractions which comprises in combination catalytica-lly reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, contacting reformation product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first parafiinic rafiinate phase, stripping light paraffins from the first aromatic extract phase in a first stripping zone, separating stripped extract into aromatic extract and solvent, contacting a normal parafiin fraction containing normal hexane and benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a normal paraflin raifinate phase con taining less than 0.5% by volume aromatics, stripping 10 light parafiins from the second extract'phase in a second stripping zone and passing the stripped second extract phase to said first extraction zone, and isomeriziing the normal paraifin raffinate with a Friedel-Crafts catalyst to obtain an isomerizate rich in isoparafiins.

16. A process for upgrading gasoline fractions which comprises in combination catalytically reforming a heavy gasoline fraction comprising cyclohexane and C and heavier hydrocarbons, contacting reformate product with a solvent selective for aromatics in a first extraction zone to obtain a first aromatic extract phase and a first parafiinic rafiinate phase, stripping light paraffins from the first aromatic extract phase in a first stripping zone, separating stripped extract into aromatic extract and solvent in a separation zone contacting a normal parafiin fraction containing normal hexane and benzene with said solvent selective for aromatics in a second extraction zone to obtain a second extract phase and a normal paraffin rafiinite phase containing less than 0.5% by volume aromatics, stripping light parafiins from the second extract phase in a second stripping zone and passing the stripped second extract phase to said separation zone, and isomerizing the normal paraffin raflinate with a Friedel- Crafts catalyst to obtain an isomerizate rich in isoparaflins.

ReEerences Cited by the Examiner UNITED STATES PATENTS 2,921,015 1/60 Shiras 20879 2,976,231 3/61 Bloch 208-79 3,001,927 9/61 Gerhold et al. 20896 3,003,949 10/61 Hamilton 208-79 ALPHONSO D. SULLIVAN, Primary Examiner.

Claims

1. A PROCESS FOR UPGRADING GASOLINE FRACTIONS WHICH COMPRISE IN COMBINATION CATALYTICALLY REFORMING A HEAVY GASOLINE FRACTION COMPRISING CYCLOHEXAND AND C7 AND HEAVIER HYDROCARBONS, PASSING REFORMATE PRODUCT TO AN AROMATICS RECOVERY SYSTEM WHEREIN THE REFORMATE IS SEPARATED INTO AN AROMATIC RICH EXTRACT AND A PARAFFINIC RAFFINATE BY MEANS OF A SOLVENT SELECTIVE FOR AROMATICS, CONTACTING A LIGHT NORMAL PARAFFIN FRACTION CONTAINING NORMAL HEXANE AND BENZENE IN AN EXTRACTION ZONE WITH SAID SOLVENT SELECTIVE FOR AROMATICS TO OBTAIN AN AROMATIC RICH EXTRACT PHASE AND A NORMAL PARAFFIN RAFFINATE PHASE, PASSING THE EXTRACT PHASE TO SAID AROMATICS RECOVERY SYSTEM TO RECOVER SAID BENZENE, AND ISOMERIZING THE NORMAL PARAFFIN RAFFINATE WITH A FRIEDEL-CRAFTS CATALYST TO OBTAIN AN ISOMERIZATE PRODUCT RICH IN ISOPARAFFINS.