US2906691A - Hydrocarbon conversion process - Google Patents

Description

Sept. 29, 1959 v. HAENsEL ErAL HYDRocARBoN CONVERSION PRocEss Filed Oct. 3. 1955 N- VEN 7'0 RS: Vlad/'m if George f?. Donaldson Hoense/ @mf J Ww .v mm\ M. /W l' mm 1 mm\ 1v mm @mi o mm; & mm A 1v mm I/ 3 v am vm s w a w, o d. (hm /fmmu Qm|\ w, Fw M QEYQ \m\ \m\ Y m n A E mm /mm wf ww .nu w. G mm km. u m mm /m /Ksw m B\ m wm/ um 4 wnu vw *Kv SES mv United States Patent O HYDROCARBON CONVERSION PROCESS Vladimir Haensel, Hinsdale, and George R. Donaldson, North Riverside, Ill., assignors, by mesne assignments, vto Universal Oil Products Company, Des Plaines, Ill.,

a corporation of Delaware Application October 3, 1955, Serial No. 538,215

3 Claims. (Cl. 208--64) This invention relates to the catalytic conversion of hydrocarbons boiling within the gasoline range. It is more specifically concerned with a novel combination of catalytic reforming, fractionation and alkylation.

The refining industry has been deeply concerned with recent trends in both the automotive and refining fields which give rise to predictions of unprecedented increases 1n gasoline quality in the near future. In recognition of these trends, research efforts have been directed toward the development of a practical method for the production of such super quality gasolines.

One process that has recently received commercial attention is the catalytic reforming process. The term reforming is well known in the petroleum industry and refers to the treatment of gasoline fractions to improve the anti-knock characteristics thereof. A highly successful and economical reforming process that has achieved er* ICC that it becomes increasingly difficult to attain high octane numbers because of the rapid reduction in the blending octane number of the component which is being produced. It is a object of the present invention to provide a better way of attaining very high octane numbers; not by the route of converting low octane number paralinsl into more aromatics, but by the route of converting these paratlins into highly branched chain high octane number paraliins.

It is another object of the present invention to convert the paraflins into other parans which should occupy a greater volume, so that the final aromatic content of the finished gasoline is lower in order to take advantage of the higher blending octane number of the aromatics present by virtue of their lower concentration.

in one embodiment the present invention relates toa process for effecting an improved yield of high octane number gasoline which comprises subjecting hydrogen and a gasoline fraction to catalytic reforming in a first Wide commercial acceptance is described in U.S. Patent erating conditions are selected to obtain large octane numl ber appreciation. This apparently is due to the fact that the relatively severe operating conditions that must be maintained in order to satisfactorally upgrade some of the paratiinic constituents of the feed are too severe for some of theother constituents.l The result is that an appreciable part of the feed stock is undesirably converted to gases and to catalyst carbon. We have invented a method of reforming which largely overcomes these objectionable features of the prior art reforming processes.

It is an object of the present invention to treat full boiling range straight-run gasoline or a fraction thereof in such a manner that increased yields of high octane number gasoline are obtained.

As hereinbefore mentioned, the high octane numbers such as 95-100 F-1 clear are attained in most cases through the production of maximum amounts of aromatics. These high aromatic contents are attained by increasing the dehydrogenation and dehydrocyclization reactions so that the final gasoline contains as much as 75-80% by weight of aromatics. However, it has been established that under those conditions, the blending octane number of the aromatics is quite low. For example, when the aromatic content of the reformed gasoline is 40% by volume, the blending octane number of the aromatics is about 136, while when the aromatic content of the Platformate is 70% by volume, the blending octane number of the aromatics is 120. Thus, it is clearly seen in that going from 40% aromatics to 70% aromatics, the incremental 30% of aromatics must have an exceedingly low `blending octane number. This indicates reforming Zone, introducing at least a portion of the re. formed gasoline fraction to a fractionation zone, withdrawing from said fractionation zone at least a low boiling fraction anda high boiling fraction and subjecting at least a portion of said low boiling fraction to alkylation.

ln another embodiment the present invention relates to a process for effectingan improved yield of high octane number gasoline which comprises subjecting hydrogen, a gasoline fraction and a predominantly paraflinic recycle fraction prepared in the manner to be hereinafter set forth to catalytic reforming in a reforming Zonein troducing at least a portion of the resultant reformed stream to a fractional distillation zone, separately withdrawing from said fractional distillation zone at least a low boiling fraction and a high boiling fraction, subject-l ing at least a portion of said low boiling fraction and an olefin containing less than tive carbon atoms per molecule to alkylation, introducing at least a portion of said high boiling fraction to a separation zone and therein effecting the separation into a predominantly paraflinic fraction and a predominantly aromatic fraction, andrecycling at least a portion of said predominantly paratiinic fraction as said hereinbefore described predominantly paraflinic recycle fraction.

In a specific embodiment the present invention relates to a process which comprises subjecting a gasoline frac-y tion and a predominantly parafinic recycle fraction prepared in the manner to be hereinafter specified to reforming in a lirst reforming zone, at a temperature of from about 600 F. to about 1000" F., a pressure of from about 200 to about 1000 pounds per square inch, with hydrogen at a hydrogen to hydrocarbon mol ratio of from about 0.5 to about 20 mols of hydrogen per mol of hydrocarbon, in the presence of a catalyst comprising alumina, from about 0.01% to about 1% by weightvof platinum and from about 0.1% to about 3% by weight of combined halogen, subsequently cooling the resultant reformed stream and effecting the separation thereof to provide a gaseous hydrogen-containing stream and an aromatic-rich hydrocarbon stream, introducing said aroi matic-rich hydrocarbon stream to a first fractionation zone to remove propane and lighter lcomponents therefrom, passing the liquid fraction from said first fractionation zone to a second fractionation zone, separately withdrawing from said second fractionation zoneat least a low boiling fraction having an' end point within the range of from about F. to about 250 F. and a high drous hydrouoric acid at a temperature of from about F. to about 200 F., recovering an alkylate product, introducing at least a portion of said high boiling fraction to a solvent extraction zone and therein countercurrently contacting said portion with a selective solvent containing diethylene glycol and from about 1% to about 20% by weight of water, separately withdrawing from said extraction zone an extract containing said selective solvent and a substantial amount of aromatics and a rainate containing a substantial amount of parainic hydrocarbons, introducing said extract to a stripper, removing as overhead from said stripper an aromaticcontaining stream, removing as bottoms from said stripper a solvent stream and recycling said stream to said extraction zone, and recycling at least a portion of said rainate to said first reforming zone as said hereinbefore described predominantly paraffinic recycle fraction.

Briefly, the present invention provides a method for effecting an improved yield of high octane gasoline from a hydrocarbon stream boiling approximately within the gasoline range which comprises subjecting the hydrocarbon stream to reforming in the presence of hydrogen and a suitable reforming catalyst. In the first reforming zone naphthenes are dehydrogenated to aromatics and heavy parains are hydrocracked to lower boiling paraffins. It is also preferred that the conditions and catalyst in the first reaction zone promote parafiin isomerization and parain dehydrocyclization reactions. In a preferred embodiment of the present invention a relatively high boiling, predominantly parainic recycle fraction, prepared in the manner herein set forth, is also reformed in the first reforming zone.

The resulting reformed stream is cooled and the separation thereof effected to provide a gaseous hydrogencontaining stream and an aromatic-rich hydrocarbon stream. The hydrogen-rich gas stream is normally recycled to the first reaction zone to provide a hydrogen atmosphere therein. Y The aromatic-rich hydrocarbon stream is passed to a stabilizer or rst fractionation zone and is fractionally distilled to reject components boiling below isobutane. The remaining liquid stream is passed to a second fractionator. In this fractionator the hydrocarbon liquid is distilled into at least two fractions, a low boiling fraction and a high boiling fraction. rfhe low boiling fraction is passed to an alkylation zone wherein it is contacted with an alkylation catalyst. A suitable alkylating agent is also charged to the alkylation zone to alkylate the alkylatable hydrocarbons in the low boiling fraction. The alkylate produced in said alkylation zone is recovered as product and in a preferred embodiment of this invention, which is hereinafter described in greater detail, at least a portion of the alkylate is combined with an aromaticrich extract and the combined stream is the final product of the process.

The high boiling fraction is passed to a separation zone i'n which the fraction is separated into a predominantly aromatic fraction and a predominantly parafiinic fraction. The resulting aromatic fraction is recovered as product. In a preferred embodiment of the present invention the predominantly parainic fraction is recycled to the first reforming reaction zone as hereinbefore described.

A feature of our process is that mild hydrocracking conditions may be employed in the rst reforming step. Generally more severe conditions are necessary to dehydrocyclicize lower boiling straight chain parains to form aromatics than to dehydrogenate a cycloparafn or a naphthene to form an aromatic. If the more severe conditions were maintained in the reforming zone, excessive hydrocracking and the production of large amounts of methane would result with the entailing loss of yield of liquid products. Alkylation of the low octane number lower boiling isoparafiins and/ or aromatics in an alkylation zone results in their .being alkylated to higher boiling higher octane number isoparains and/or aromatics without the excessive production of gaseous hydrocarbons. Therefore, a feature of our process is that the alkylation may be conducted so as to convert a substantial portion of the low boiling low octane number paraflins and aromatics to higher octane number isoparathns and aromatics while at the same time minimizing undesirable side reactions which otherwise reduce yields of useful gasoline products.

As hereinbefore mentioned, one of the chief reasons for deposits of carbon or carbonaceous material on the catalyst is the reaction of heavier aromatics to form polynuclear aromatics. In our process, however, the aromatics are removed from a portion of the charge to the reforming reaction zone and, therefore, substantially less carbon is formed on the catalyst with resultant longer catalyst life. High severity operation in the presence of aromatics is also not desirable from considerations of chemical equilibria involved, as in such operations the aromatics in the feed limit the extent to which such aromatics can be .formed from naphthenes and parafiins. In contrast, however, the use of our process involves the removal of a substantial portion of the aromatics from the charge to the second reaction zone which thus permits the` formation of additional aromatics unrestricted by the limitations of chemical equilibria.

Accordingly, the eluent from the first catalytic reaction zone is fractionated into at least a low boiling fraction and a high boiling normally liquid fraction for several reasons. One reason is that we have discovered that the low boiling fraction contains a smaller percentage of aromatics than the entire liquid fraction and, of course, that the high boiling fraction contains a higher percentage of aromatics than the entire fraction. When the end point of the low boiling fraction is within the range of from about F. to about 250 F., the low boiling fraction contains a small amount of aromatics and a large amount of isoparaflins and, therefore, the low boiling fraction is very suitable as a charge of alkylatable compounds.

Further, according to our invention, the high boiling fraction, and preferably a fraction having an initial boiling point within the range of from about 150 F. to about 250 F. contains a relatively high proportion of aromatics. This stream cannot be appreciably enhanced in octane number by a subsequent reforming operation. We have discovered, however, that when this high boiling fraction is introduced into a separation zone and the fraction separated into a predominantly aromatic fraction and a predominantly paratinic fraction, that the predominantly parafinic fraction may be very substantially increased in octane number by a catalytic reforming operation. Further, we have discovered that the conditions existing in the first reforming zone are approximately the optimum conditions for the reforming of this predominantly parafiinic fraction and, therefore, in a preferred embodiment of the present invention this predominantly paraffinic fraction is recycled to the first rcforming zone.

The charge stocks which may be reformed in accordance with our process comprise hydrocarbon fractions that boil within `the gasoline range and that contain naphthenes and paraiiins. The preferred stocks are those consisting essentially of naphthenes and parains, although aromatics and minor amounts of olens may be present. This preferred class includes straight-run gasoline, natural gasoline and the like. The gasoline fraction may be a full boiling range gasoline having an initial boiling point within the range of from about 50 F. to about 100 F. and an end boiling point within the range of from about 350 F. to about 425 F. or it may be a selected fraction thereof which usually is a higher boiling fraction cornmonly referred to as naphtha and having an initial boiling point within the range-of from about 150 F. to about 250 F. and an end boiling point .within the range of from about 350 F. to about 425 F. Mixtures ofthe various gasolines and/ or gasoline fractions may also be used and thermally cracked and/or catalytically cracked gasolines may be used as charging stock. However, when these unsaturated gasoline fractions are used, it is preferred that they be used either in admixture with a straight-run or natural gasoline fraction, or else hydrogenated prior to use.

In a preferred operation in the rst reforming step, wherein the charge is subjected to hydrocracking and aromatization, the contact is made at a pressure of from about 200 to about 1000 pounds per square inch.

A preferred operation effects the recycle of the hydrogen stream being separated from the reformed gasoline stream into contact with the charge stream in order to kprovide added hydrogen to the catalytic reforming zone.

Various types of desirable and suitable reforming catalysts may be utilized in the reforming reaction zone, however the preferred operation utilizes platinum-containing catalysts. The catalysts may be used in the first reforming zone of our invention comprise those reforming catalysts that permit dehydrogenation of naphthenic hydrocarbons, hydrocracking of paraflinic hydrocarbons and isomerization of parafiinic hydrocarbons. A satisfactory catalyst comprises a platinum-alumina-silica catalyst of the type described in U.S. Patent No. 2,478,916, issued August 16, 1949. A preferred catalyst comprises a platinum-alumina-combined halogen catalyst of the type described in U.S. Patent No. 2,479,109, issued August 16, 1949. Other catalysts such as molybdena-alumina, chromia-alumina, and platinum on a carrier or support such as a cracking catalyst base may be used. The platinum concentration in the catalyst may range up to about by weight or more of the alumina, but a desirable catalyst may be provided to contain as low as from about 0.01% to about 1% by Weight of platinum. The halogen ions may be present in an amount of from about 0.1% to about 8% by weight of the catalyst but preferably are present in an amount of from about 0.1% to about 3% by Weight of the alumina on a dry basis. Also, while any of the halogen ions provide a desirable catalyst, the fluoride ions are particularly preferred and next in order are the chloride ions7 the bromide ions and iodide ions.

The conditions in the first zone should be such that substantial conversion of naphthenes to aromatics and relatively mild hydrocracking of parathns are induced; and, further, the operating conditions in the second zone should be such that there is a substantial alkylation of isoparaflinic compounds and/or aromatics. When. employing platinum-alumina-combined halogen catalyst in the reforming zone, the conditions in each are usually a temperature within the range of from about 600 F. to about 1000 F., and a weight hourly space velocity of from about 0.5 to about 20. The weight hourly space velocity is defined as the weight of oil per hour per weight of catalyst in the reaction zone. lt is preferred that the reforming reaction be conducted in the presence of hydrogen. In one embodiment of the process, sufficient hydrogen will be produced in the reaction to furnish the hydrogen required in the process and, therefore, it may be unnecessary to introduce hyd-rogenfrom an external source or to recycle hydrogen within the process. However, it will be preferred to introduce hydrogen from an external source generally at the beginning of the operation and to recycle hydrogen within the process in order to be assured of a sufcient hydrogen atmosphere in the reaction zone. The hydrogen present in the reforming reaction zone will be within the range of from about 0.5 to about mols of hydrogen per mol of hydfocarbon.. In some cases, theV gas to be recycled will contain hydrogen sulfide introduced with the charge or liberated by the catalyst and it is within the scope of the present invention to treat the hydrogenrcontaining gas to remove hydrogen `sulfide or other impurities beforethat there are substantially no olefins present in the product streams from the reforming reaction zone.

The effiuent from the first reaction zone is, therefore, first passed to a high pressure separator to separate the hydrogen from the hydrocarbons and, as hereinbefore mentioned, the hydrogen is usually recycled to the first reaction zone. The hydrocarbons are then usually passed to a first fractionation zone which effects the separation of gaseous material which comprises hydrogen, hydrogen sulfide, ammonia and hydrocarbons containing from one to three carbon atoms per molecule. This fractionation column may be termed a depropanizer since its function is to remove propane and lighter components.

It is an essential feature of the present invention that the depropanized liquid is passed to a fractional distillation zone in which the depropanized liquid is fractionated into at least two fractions, that is a low boiling fraction and a 'nigh boiling fraction. We have discovered, and our invention is based on this discovery, that when the depropanized fraction is fractionated into at least two fractions that the optimum operating conditions for reforming the low octane number higher boiling parafiins in the high boiling fraction are those existingv in the first reforming zone and, therefore, in a preferred embodiment of our invention the higher boiling parains are recycled to the first reaction zone. The low octane number lower boiling fraction, however, requires a different treatment. fins in the low boiling fraction may be dehydrocyclicized to form additional aromatics; however, as hereinbefore been illustrated, the production of additional aromatics is not particularly vdesirable since these additional aromatics have a low blending octane number. We have discovered that the lower boiling fraction contains large amounts of alkylatable compounds such as branched chain alkanes and cyclic hydrocarbons and, that the low boiling fraction is an excellent charge of alkylatable compounds for an alkylation process.

In some cases the heavy boiling fraction may contain components which are heavier than it is desirable to recycle to the first reforming zone. For example, the high boiling fraction may contain heavy parains, that is parans boiling above about 400 F., and upon recycling these heavy parains to the first reforming zone, these heavy parafiins have a tendency to form carbonaceous material on the catalyst and to deactivate the same. In a preferred embodiment of the present invention the heavy fraction is further fractionated to remove heavy components therefrom, that is components boiling above about 400 F. The heavy fraction, substantially free of components boiling above 400 F., is then introduced to a separation zone to effect the separation of the aromatics from the heavy parains, and the heavy parafiins are then preferably recycled to the first reforming zone. The exact temperature at which the depropanized fraction is split in general depends upon the character of the components in the fraction; however, we have found that generally it is preferred that the end point of the low boiling fraction is within the range of from about F. to about 250 F. The low boiling fraction, that is to be subsequently alkylated, therefore, has a preferred initial boiling point of about isobutanes boiling point and a preferred end point within the range of from about 150 F. to about 250 F. The lheavy fraction has a preferred initial boiling point within the range of from about 150 F. to about 250 F. and an end boiling point within the range of'from` about 375 F. to about 425 F.

The light fraction from the second fractionation zone`- is passed to an alkylation zone along with a suitable all As hereinbefore mentioned the parafsuenan kylati'ng, agent. In the alkylation zone asuitable alkylation rcatalyst andialkylation,conditions are maintained.

Suitablealkylating agents which may be charged to tl'ealltyl'ation zone are olefin-acting compounds including mono-olefins, diolens, polyolefins, also alcohols, ethers, esters, the latter including alkyl halides, alkyl phosphates, certain alkyl sulfates and also esters of variousv organic carboxylic acids. The preferred alkylating agents are olefinic hydrocarbons which comprise monooleins having one double bond per molecule and polyol'ens which have more than one double bond per molecule. Mono-olefins which may be utilized for alkylating aromatic hydrocarbons and other alkylatable compounds in the presence of the catalyst of this invention, as herein setlforthare either normally gaseous or normally liquid and include ethylene, propylene, butylenes, pentenes and higher normally liquid olens, the latter including various'` polymers of gaseous oletins, particularly polymers having from six to eighteen carbon atoms per molecule. Cyclo-oleiins such as cyclopentene, cyclohexene, and various alkylcyclooletins may also be used. Other unsaturated hydrocarbons used as alkylating agents in this process include conjugated diolens such as butadiene andiisoprene, non-conjugated diolens, other polyolen hydrocarbons containing more than two double bonds per molecule, terpenic hydrocarbons, etc.

Any suitable alkylation catalyst may be used in the alkylationezone. The primary reaction in the alkylation zone is the alkylation of isoparafns with olens and for. this reaction the preferred catalysts comprise concentrated' sulfuric acid, hydrogen fluoride, aluminum chloride with hydrogen chloride and phosphoric acid either in:liquid form or in the form of a solid cornp'osite' With a suitable adsorbent. When using these acid"catalysts, temperatures within the range of from about 'FL to about 200 F; are preferred, Sufficient pressure ismaintained in thev system to keep the reactants in the liquid phase.

The alkylation of isoparainic hydrocarbons with olefinie hydrocarbons in the presence of various condensing agents is a process for the production of saturated hydrocarbons or hydrocarbon fractions which, because of their high octane number and high susceptibility to added tetraethyl lead, are important constituents of aviation gasoline. Catalysts such as concentrated sulfuric acid, chlorosulfonic acid, fluorosulfonic acid, phosphoric acid, aluminum. chloride, etc., have been proposed forl effecting this reaction.

Hydrogen uoride is a preferred alkylation catalyst. Hydrogen fluoride catalysts are, in general, more selective, and undesirable side reactions such as polymerization, oxidation,retc. are avoided to an appreciable extent` even when operating at temperatures substantially higher than are feasible with other alkylation catalysts. Moreover, the use of substantially higher operating temperatures eliminates the necessity for expensive refrigeration equipment which is required, for example, in

commercial alkylation units employing sulfuric acid as a catalyst. contaminated with continued use, it may be regenerated readily and1 returned to the process for reuse. For example, regeneration may be effected by a distillation step-or series of steps wherein purified hydrogen fluoride is' separatedV from water'and organic contaminants of a rpolymer-like nature.

Isoparans generally, including thenormally liquid isoparafns such as isopentane or-isohexane, may be alkylated with either normally gaseous or normally liquid olei'ns using a hydrogen fluoride catalyst. One of the most important applications of the process is found in the alkylation: of isobutane with normally gaseous oleiins, particularly the butenes. Substantial amounts of isobutane are-presente in the light fraction and the butenes are-readily availablefrom stabilizer overhead` streams,

cracking plant gas, etc.

As the hydrogen fluoride catalyst becomesv The etlluent fromthe alkylation. zone may be fractionated toproduce an alkylate within the gasoline boiling range, and. in ay preferred embodiment of this invention at least a portion of the alkylate is combined with an aromatic extract stream prepared as hereinafter set forth. and the combined stream is the final product of theprocess. The combined stream is a motor fuel of highoctane rating and excellent starting characteristics.

The heavy fraction from the second fractional distillation zone is passed to a separation zone to produce a more concentrated aromatic fraction. The separation. of a more concentrated aromatic fraction may be accomplished in any conventional manner suchV as solvent extraction,- solid absorption, fractional crystallization, the..

use of urea adducts, molecular sieves, etc.; however, thev solvent extraction process is particularly preferred in the,v

present invention since4 its use generally produces best results.

Solvent extraction processes are used to separatev certain components in a mixture from other components. thereof by a separation process based upon a difference in, solubility of the components in a particular solvent. Itis frequently desirable to separate various substances by solvent extraction: when the substances to be separated have similar boiling points, are unstablev at temperatures at which fractionation is elfected, form constant boilingl mixtures, etc. It is particularly desirable to separate aromatic hydrocarbons from a petroleum fraction,` containing these aromatic hydrocarbons by solvent ex-v tractionv because a petroleum fraction is normally a com plex mixture ofv hydrocarbons whose boiling points are extremely close togetherI and because the petroleum frac.- tionv contains numerousl cyclic compounds which tend, to, form constant boilingor, azeotropic mixtures. Ashereinbefore stated, the basis of a solvent extraction separationis the difference inA solubility inV a given solvent off one of the substances to be separated from the other. Itmay, therefore, be seen that the more extreme this` difference the easiervthe separation will be and an easier, separation reflects itself process-wise in lessA expensive; equipment and greater yields per` pass in the use of processing equipment as well as in higher purity of product..

Aparticularly preferredsolvent for separating aromatic hydrocarbons from non-aromatic hydrocarbons isa mixture of water and ahydrophilic organic solvent. Such a solvent may have. its solubility regulated by adding more or` less water thereto. Thus, by adding more water to the, solvent, the solubility of all components in the hydrocarbon mixture are reduced, but the solubility differences among the components are increased. This effect is reected process-wise in less contacting stages required to4 obtainV a given purity of product. However, a greaterl throughput of solvent must be used in order to obtain the same amount of material dissolved.

As hereinbefore stated, the solvent to be used in this invention is preferably a mixture of a hydrophilic organic solvent and water, wherein the amount of water contained inthe mixture is selected to regulate the solubility in the solvent of the materials to be separated. Suitable hydrophilic organic solvents include alcohols, glycols, aldehydes, glycerine, phenol, etc. Particular preferred solvents are diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol ad mixtures thereof containing from about 1% to about 20% by weight of water. Some hydrophilic substances can be used without added water, such as, for example, sulfur dioxide.

Inv classifying hydrocarbon type compounds according to increasing solubility in such a solvent, it is found that the solubility of the various classes increases in the following rnanner: the least soluble are the parains followed in increasing order of solubility by naphthenes, 0lens, diolefins, acetylenes, sulfur, nitrogen and oxygen-containing compounds and aromatic hydrocarbons. It mayl thus be seen that a charge stock which is rich in unsaturated compounds will present a greater problem` iir solvent extraction than a saturated charge stock since the unsaturated compounds fall between the paratiins and aromatics in solubility. It may be seen that an ideal charge to solvent extraction is one containing paraiiinic and aromatic hydrocarbons exclusively.

The high boiling paratiinic hydrocarbons recovered from the separation zone are preferably recycled to the first reaction'zone. It is within the scope of the present invention to treat the high boiling paraiiin fraction by fractionation, water washing, clay treatment, etc. before recycling the same to the iirst reaction zone.

Additional features and advantages of our invention will be apparent from the following description of the accompanying drawing which illustrates a particular method for conducting a gasoline reforming operation in accordance with the present invention. Although the process illustrated in the drawing represents one of the preferred forms of our invention, it is to be understood that our invention is not limited thereto. A number of variations may be introduced into the process without departing from the spirit and scope of said invention.

For simplification many valves, pumps, heat exchangers, land similar appurtenances have been omitted fromv the drawing since their illustration is not necessary tothe'understanding of the invention.

Referring now to the drawing, there is indicated a 200 F. to 400 F. straightrun naphtha stream being passed by way of line 1,*valve 2 and line 3 into heater 7. The rcharge stream in line 3 before entering heater 7 combines with hydrogen being recycled by way of line 4 arid' a-hig`h boiling predominantly paraflinic recycle fraction being introduced by wayof line 5. The combined stream iii line 6 passes into heater 7. The gasoline or naphtha charge stream may be a straight-run gasoline or naphtha, a naturalu gasoline or naphtha or other relatively lowoctane number stream which is to undergo reforming to provide a high yield of aromatic hydrocarbons, together with desirable high octane number aviation and motor fuels. A heated stream of the order of about 920 F. while at a` pressure of the order of 600 pounds/per square inch is introduced by way of line 8 into reactor 9.

Reforming reactor 9 contains a bed of spherical catalystof approximately 1A; inch average diameter' containing 0.3% platinum, 0.5% combined fluorine, and 0.1% combined chlorine. During the passage of the charging stock through the iirst reactorv 9 the bulk of the naphthones containing six or more carbon atoms per molecule Iaredehydrogenated to the corresponding aromatics. and a portion of the paraiiins are hydrocracked to lowerFV b oiling parafiins. Isomerization of the paraflins and some dehydrocyclization of the paraiiins in the charge preferably also-takes place. The drawing indicates a single conversion zone 9, however, it is to be understood that one -or morezones may be utilized in series, with inter-V heaters therebetween if desired, so that there may be accomplished a substantial degree of aromatization of the charge stream.v Y Y At the conditions vin the reforming zone or reactor 9 and in the presence of hydrogen and the catalyst of this process,` oleiinic materials will not be produced in any appreciable amounts., n Y

'Ihe resulting ref ormedstream passes from the first reactionzone 9 byway `of line 10, cooler 11 and line 12 and subsequently enters high pressure receiver 13. A resulting hydrogen-containing gaseous` stream is discharged from the upper portion of receiver 13 by way of line 14. A portion of the hydrogen-rich gas stream may be withdrawn from line 14 through line 15 containing valve 16. The rest of the hydrogen continues through line 17, is picked up by compressor 18 and discharged through line 4. The hydrogen in line 4 combines with the charge stream and ultimately passes into reaction zone 9. Acondensed hydrocarbon stream is passed from receiver 13 by way of line 22, valve 23 and line g4 and ,y hydrogen fluoride.

enters a iirst fractional distillation zone or depropanizer 30. In accordance with'the present invention, normally gaseous hydrocarbons are removed overhead through line 31. In depropanizer 30 the normally gaseous material, which includes hydrogen, ammonia, hydrogen sulfide and hydrocarbon gases containing from one to three carbon atoms per molecule, is separated from the hydrocarbon liquid comprising aromatic hydrocarbons and parafiinic hydrocarbons.

The gaseous material passes overhead through line 31 into cooler 32, wherein a portion of the material is condensed and the total stream passes through line 33 into receiver 34. In receiver 34 the liquid phase and gaseous phase of the overhead separate; the gaseous material passes through line 35 from which it may be vented to' the atmosphere 0r used as fuel or may be further usedv in the present process or other processes. The depropanizer has heat provided thereto by reboiler 39 and con-p` necting lines 38 and 40. The depropanizer 30 and receiver 34 are operated at a suiiicient pressure to liquefy at least a portion of the overhead material so that a liquid reflux stream is available to improve the separation in depropanizer 30. The liquid reux is removed from receiver 34 through line 37 and passes into an upper portion of depropanizer 30. The depropanized fraction Awhich, as hereinbefore stated, comprises substantially paraflinic and aromatic hydrocarbons, is withdrawn from -depropanizer 30 through line 45 and introduced into fractionator 46. The conditions in fractionator 46 are maintained so that components which are suitable for alkylation are removed as an overhead fraction. In the embodiment of the drawing the overhead is shown asV components boiling from isobutane to F. These components 'are removed from Ifractionator 46 through line 47 and passed into cooler 48 wherein the material is condensed and the entire stream passes through line 49 into receiver 50. The liquid in receiver 50 splits into several streams. A portion of the liquid in receiver 50 may be withdrawn through line 52 and introduced to an upper portion of fractionator 46 as reflux. The charge for the alkylation zone is withdrawn through line 51, picked up by pump 59 and discharged through line 60. A portion of the liquid may be withdrawn from line 60 through line 61 containing valve 62 while the remaining portion continues through line 58 into alkylator 63.

In alkylator 63 the isoparaiiins are contacted with a butene-Z stream introduced through line 64.v A temperature of 30 F. is maintained in the alkylation zone and the alkylation is conducted in the presence of anhydrous mixing or agitation zone. tion zone 63 is withdrawn through line 65 and a portion may be withdrawn through line 66 containing valve 67 and recovered as product. However, in a preferred embodiment of this invention the alkylate continues through line 68 and combines with an aromatic concentrate in line 96 and the combined stream in line 69 is recovered asf the iinal product.

Referring back to fractionator 46 a high boiling stream, boiling above 400 F. is Withdra-wn as bottoms through line 56. Heat is provided for the fractionation in frac-l tionator 46 by reboiler 54 and connecting lines v53 and'55.. A high boiling fraction having an initial boiling point of 175 F. and an end boiling point of 400 F. is withdrawnk Alkylation zone 63 is preferably a Y The product from the alkyla`l forming. an extract. streamv 81 containingv the solventandC aromatichydrocarbons, and a raffinate stream. 5jcontaining.,theparaflinic hydrocarbons.` Therai'nate stream passes from the, upper portion, of extractor 8.0 through line 5`while the extractstream passes through the. lower portion ofcextractor 80 throughv line 81. Line 81passes4 to-ash drum 82., Flash drum. 82 is maintained at a pressure lower than the extractor andV preferably iskeptat matic hydrocarbons and'dissolved parains areseparated4 from the selectiveV solvent.A Line 84 is preferably cone n ectedgto the stripper 85 yat apoint in the upper half of the column.. The separation .instripper 85 isnOtdifcult as the aromatic hydrocarbonsare substantially, different, in nature from the selective solvent aswell as havinga substantially differingr boiling; point. The aromatic hyd'rocarbonA stream along with some paraflins passes over.-

head from the stripper 854 through line 86 and combines. with the overhead from the flash drum inline 83 and the combinedstream in line 87 is recoveredas product. through line 94 containing valve 9S. As hereinbefore mentioned it ispreferred to combine atleast aportionof the aromatic concentrate in line. 96 with the, product in. line 68' and to recover the combinedstream in line. 69-

as the final' product. Heat is providedfor the stripping operation by reboiler 89 and connecting lines 88, and 90..

The solvent streamis removed from.the bottom, ofstrip; per 85.through line 91` and is, passedV into the upperV por.- tion of extractor 801ashereinbeforedescribed.

The raffinate stream from extractor 80 .which is with:

drawn through line is recycled to the first reforming. zone. 9; AV portion' of the ranate may beremoved through. line 92 containing valve 93. Therainate may` containdissolved and entraned solventand therainate may be water washed to remove thesolventand/or fur-V ther fractiouatedbefore recycling the ranateto the re.- forming zone.

The following exampleA is given tofurther illustrate vour invention but is notv given for the purposeof unduly limit-- ing the generally broadscope-ofgsaid` invention..

Example. A naphtha fraction having an initial boiling point of 185 F. and an end point of 392 F. is passed through a,

bed of catalyst comprising, aluminacontaining 054% by weight of platinum and 0.6% by'weight of fluorine ata pressure of 500 pounds per square inch, a hydrogen to hydrocarbon mol ratio of 10:1, a weight hourly space velocity of 3.0 and an initial average, catalysttemperature of' 900 F. A predominantly paraflinic` hydrocarbon fraction prepared as hereinafter described is also intro.-

duced to the reforming zone along with the naphtha.

fraction.

The eflluent from the reaction zone is cooledfand C and lighter components removed by fractional distilla:

tion. The depropanized. liquid isV fractionally4 distilled in-a second fractionation column to form a low boiling fraction having an end boilingrpointof 180 F. and a high boiling fraction having an initialV boiling pointof 180 F. and an end point of.400 F.

The vlow boiling fraction Ais introducedto analkyl'ation'. zone. VButene-Z is also introducedlto the alkylation zone., Thealkylation is carried out at 40 Fl inthe presence. o'. 98% hydrogen iluoride. The pressure inthe; alkylation. zone is 10 atmospheres. The space time, which is,de fined as the volume of liquid catalyst in the reactionzoney provided by the feed rate of hydrocarbon, reactants in: volumes ofliquid per minute, is 35 minutes. As. iswelL knownin the` alkylationV art, a relatively large excessof` isoparains over olelns is maintained inthe alkylation. zone. The alkylate is fractionated to produce afraction having an initial boiling point of about and an, end point of about 400 F.

The high boiling, 180-400" FL fraction,l is countercurrently` contacted in a sieve deck tower with a descendf. ing stream of 96% diethyleneglycol and.4% water.. The. contact is effected at 310 F. and 250 poundspersquare. inch pressure. The raiinate is removed from thetop of` the tower and the extract isremoved from thebottomfof..A the tower. The aromatics arerecovered from the extract' by fractional distillation. The` raflnate removed from the extractor is recycled to the first reforming reactor as. the hereinbefore described predominantly paranic recyf cle stream. The aromaticsV are blended. with the frac.- tionated alkylate. The mixture is-a motor fuelof. high road octaine number and excellent startingcharacteristics We claimas our invention:

1. A process. for producing an improved motor fueliwhich comprisescatalytically reforming a: gasoline frac-.- tion, separatingfromV the resultant reformed. products,t a. relatively light fractioncontaining isobutane and.highexl boiling-,isoparans and a heavier'fraction.containingarozV maticsn and paraflins,. said. light fraction havingl amend..

boiling point of.from.about to about 250? Rand. said heavier. fraction; having an initial, boiling pointof;

from. 150 to about 250 F., subjectingsaid lightfracff tion to alkylation to alkylate isobutane and heavier iso-- paraffins presenttherein and thereby form an.alkylate oh.

high. octane number, subjecting said heavier fractionto, solvent extraction with a selectivesolvent for aromatics to separate aromatics from parains, blending,i at least-.a.

portion of the thusseparated aromatics with atleasta portionof said alkylateand recoveringthe resultant blend.` as said improved motor fuel.

2. The process of. claim 1 furthercharacterized.in'thaty paraflins separated by the solvent. extractionare supplied. to the reforming step.

3. The process of claim l further. characterized. in that. said light fraction is alkylated with. an olefin oflessthan.v 5 carbon atomsper molecule.

References Cited in the tile of. this patent.` UNITED STATESPATENTS

Claims (1)

1. A PROCESS FOR PRODUCING AN IMPROVED MOTOR FUEL WHICH COMPRISES CATALYTICALLY REFORMING A GASOLINE FRACTION, SEPARATING FROM THE RESULTANT REFORMED PRODUCTS A RELATIVELY LIGHT FRACYION CONTAINING ISOBUTANE AND HIGHER BOILING ISOPARAFFINS AND A HEAVIER FRACTION CONTAINING AROMATICS AND PARAFFINS, SAID LIGHT FRACTION HAVING AN END BOILING POINT OF FROM ABOUT 150* TO ABOUT 250* F, AND SAID HEAVIER FRACTION HAVING AN INITIAL BOILING POINT OF FROM ABOUT 150* TO ABOUT 250* F, SUBJECTING SAID LIGHT FRACTION TO ALKYLATION TO ALKYLATE ISOBUTANE AND HEAVIER ISOPARAFFINS PRESENT THEREIN AND THEREBY FORM AN ALKYLATE OF HIGH OCTANE NUMBER, SUBJECTING SAID HEAVIER FRACTION TO SOLVENT EXTRACTION WITH SELECTIVE SOLVENT FOR AROMATICS TO SEPARATE AROMATICS FROM PARAFFINS, BLENDING AT LEAST A PORTION OF THE THUS SEPARATED AROMATICS WITH AT LEAST A

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