US2853437A

US2853437A - Hydrocarbon conversion process

Info

Publication number: US2853437A
Application number: US511289A
Authority: US
Inventors: Haensel Vladimir
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1955-05-26
Filing date: 1955-05-26
Publication date: 1958-09-23
Anticipated expiration: 1975-09-23

Description

sept. 23, 1958 v. LIAENSEL- .2,853,437

-HYDROCARBON CONVERSION PROCES Filed May 26. 1955 Rabo m s vl Mw .f TH ,M wmf/ W United States Patent tO Y 2,853,437 HYDROCARBON CONVERSION PROCESS Vladimir Haensel, Hinsdale, lll., assignor to Universal Gil Products Company, Des Plaines, Ill., a corporation of Delaware Y Application May 26, 1955, Serial No. 511,289 6 Claims. (C1. 19e-50) This invention relates to the catalytic conversion of hydrocarbons boiling within the gasoline range. Itis more specifically concerned with a novel combination of catalytic reforming, solvent extraction and fractionation steps.

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 in 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 produc- I tion 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 ygasoline fractions to improve the anti-knock characteristics thereof. A highly successful and eco-nomical reforming process that has achieved wide commercial acceptance is described in my U. S. Patent No. 2,479,110. However, the present reforming processes are `all limited by decreasing yields at increasing octane numbers. There are also other limitations. For example, when a full boiling range straight-run gasoline or a relatively wide boiling range naphtha is reformed in the presence of `a catalyst that promotes dehydrogenation of naphthenes and hydrocraclcing of parafiins, relatively poor yields and considerable fouling of the catalyst are obtained when the operating conditionsare selected to obtain large octane number appreciation. This apparently is due to the fact that the relatively severe operating conditions that must be maintained in order to satisfactorily upgrade the higher boiling paraffinic constituents of the feed are too severe for some of the other constituents. The result is that an appreciable part of the feed stock is undesirably converted to ygases and to catalyst carbon. Therefore, under the usual conditions of operation the yield of liquid product `and catalyst life are limited to a considerable extent by and primarily dependent on the decomposition and carbon-forming tendencies of the `higher boiling paraffinic constituents and the aromatic constituents. The higher boiling paratiinic constituents may decompose to form coke on the catalyst and the aromatic constituents also deposit coke or carbonaceous material on the catalyst by reacting with each other and forming polynuclear aromatics which are the carbonaceous materials that foul the catalyst. I 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 increase the octane lnumber of low octane number ga-solines and fractions thereof.

-It is another object of the present invention to treat low octane number gasoline in a system utilizing catalytic reforming, solvent extraction, and fractionation so as to obtain a high octane number gasoline and high yields of liquid product.

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'predominantly .paraflinic fraction into a low boiling Spredominantly paraini'c fraction land said high boiling predominantly parafinic fraction, and '(-b) Phydrogenand a second hydrocarbon charge containing a high boiling straight-run naphthasfraction and `said low boiling kpredominantly ',parafiinic fra'ctio'n. Y

yIn another embodiment the Ipresent invention relates to a process which comprises fractionating a straight-run gasoline fraction 'into at least alow 'boiling fraction and a high boiling fraction, 'contacting ina catalytic reforming zone hydrogen, said low boiling fraction, and a high boiling Apredominantly parainic'fraction obtained ashereinaf-ter mentioned,.subjecting the effluentfroms'aid catalytic reforming Zone to asep'aration step to separate lsaid effluent into a predominantly parafiinic fraction and apredominantly aromatic fraction, fractionating said predominantly parafinic vfractionfinto at .least allow boiling predominantly parainic fractionland a 'high boiling .predominantly 'parafiinic fraction and introducing said high reforming zone, as hereinbefore .mentioned, and there- -aftercontacting in `said catalytic `reforming zon-e hydrogen,

said high boiling fraction, and said low boiling predominantly parafinic fraction.

ln a more specific embodiment my invention relates to a process which comprises ifractionating a `straight-run naphtha into a ylow 4`boiling fraction -havingiy an initial boiling point of about 200 F. and an end boiling `point of -about `300 F. and a high boiling fractionv having an initial boiling point of labout 300 F. `and an end boiling point of about 400 F., 'subjecting hydrogen, said low boiling fraction and a highboiling predominantly parafyfinic fraction obtained as hereinafter setforth, to contact 'with a catalyst comprising platinum, alumina, and combined halogen rat reforming conditions, introducing the effluent from the catalyticreforming'zone to anextraction zone wherein said effluent is treated with a selective solvent having a relatively Vhigh-er solvent power for aromatics, separately `withdrawing from said extractionizone a predominantly aromatic vfraction and a predominantly parafiinic raiinate, 'fractionating said raffinate into a low boiling predominantly p'araffinic fraction and a high boiling predominantly paraffinic fraction, introducing 'said high boiling predominantly paraffinic fraction 'to said catalytic reforming zone, and subsequently separately'coutacting said high Vboiling fraction `having yan initial yboiling point of about 300 F. and an end pointof vabout 400 F. and said low boiling predominantly parainic fraction to contact with a catalyst comprising platin-um, alumina-and combined halogen in a reforming zone at reforming conditions.

Briefly, the Ypresent invention provides a method `for effecting an improved yield of 1high octane gasoline from a hydrocarbon charge boiling in the-gasoline range, and hereinafter referred toas 'the primary charge, which comprises fractionating the hydrocarbon charge into at least two fractions; that is, a low boiling fraction and a high boiling fraction. The low boiling fraction of the primary charge is' combined with a high boiling fraction of apredominantly paraflinic raflinate`,;prepared as lnreinafter set forth, andthe combined stream is subjected .to

reforming in the presence of hydrogen and a suitable reforming catalyst. The heavy fraction, prepared in the prior fractionation of the primary charge, is combined with a low boiling fraction of a predominantly parafnic rafhnate, as hereinafter set forth, and this combined stream isV also subjected to reforming in the presence of hydrogen and a `suitable reforming catalyst. For economic reasons it is preferred to use only one reforming zone and to alternately and separately charge each of the combined streams as hereinbefore mentioned. For example, the low boiling portion of the primary charge and the high boiling portion of the predominantly parafinic raii'inate in combination are subjected to reforming. Subsequently the processing of this combined stream is discontinued and the high boiling portion of the primary charge and the low boiling portion of the predominantly parainic ranate in admixture are passed to the reforming zone. The invention, therefore, provides for a blocked-out type of operation, that is an operation in which a charge stream is reformed for a period of time, the reforming of thisl charge stream discontinued, followed by the reforming of another charge stream.

In the reforming zone naphthenes are dehydrogenated to aromatics and heavy paraiins are hydrocracked to lower boiling paraifins. It is also preferred that the conditions and the catalyst in the reforming zone be such that there is paran isomerization and paraffin dehydrocyclization. The resulting reformed stream is cooled and the separation thereof eected to provide a gaseous hydrogen-containing stream and an aromatic-rich hydrocarbon stream. The aromatic-rich hydrocarbon stream is fractionated to reject the normally gaseous hydrocarbons produced in the process and the resultant liquid is passed to a separation zone in which the recovery of aromatic hydrocarbons is effected. The resulting nonaromatic or paranic hydrocarbon stream is passed to a fractionation zone wherein the ranate or paraflnic hydrocarbon stream is fractionated into at least a low boiling fraction and a high boiling fraction. Each of these fractions contains predominantly paraflinic hydrocarbons. The low boiling fraction is passed to combine with the high boiling fraction prepared by fractionating the primary charge stock. The high boiling predominantly parainic fraction is passed to combine with the low boiling fraction of the primary charge stock. As hereinbefore mentioned, each of these combined streams' is separately reformed. Preferably the same reforming zone is utilized in a blocked-out, or alternate type of operation.

A feature of my invention is that greater utilization of the catalyst surface may be achieved by employing the steps of my invention. As hereinbefore mentioned, the preferred catalyst in the reforming zone effects dehydrogenation of naphthenes to form aromatics, the hydrocracking of high boiling parailns to form lower boiling parans, the isomerization of straight chain or slightly branched chain paraflins to more highly branched chain paraflins, and the dehydrocyclization of parans to form aromatics. Some of the higher boiling components of the charge stock, therefore, are hydrocracked on the catalyst surface to form lower boiling parains. Now if the high boiling portion of the primary charge is reformed in admixture with the high boiling portion of the predominantly parainic rafiinate there exists competition for the catalyst surface; that is, both the heavy naphthenes and the` heavy parains of the charge and the heavy parans of the predominantly paraffinic rafiinate are competing for the catalyst surface. Similarly, the low boiling hydrocarbons of the charge are preferably improved in octane number by isomerization and/or dehydrocyclzation. When these low boiling hydrocarbons of the primary charge are reformed in admixture with the low boiling components of the predominantly paranic ranate, there again exists a competing of the hydrocarbons for lthe catalyst surface; that is, some of the lower boiling naphthenic hydrocarbons from the primary charge stock competes With the lower boiling hydrocarbons from the predominantly parafinic raiiinate. Each of these components must be reacted to achieve an increase in octane number, however, the amount of catalyst surface available is limited and, therefore, these hydrocarbons' compete with each other for the available catalyst surface. Generally the competing of the hydrocarbons for the catalyst results in lower reforming eiciencies and accordingly lower yields and lower octane numbers. Accordingly when a charge stock is passed over the catalyst, there is a competition for the available catalyst surface and, therefore, for the reaction among the various species of hydrocarbons present. It is indicated that the most strongly adsorbed materials are the highest boiling aromatic hydrocarbons, while the least strongly adsorbed materials are the lowest boiling parains. The competition for the surface is not only on the basis of polarity of the molecule, but also on the basis of molecular weight, so that in any one particular species or type of hydrocarbon, the higher boiling materials are considerably more strongly adsorbed on the catalyst surface than the lower boiling member of the species. Thus, high boiling parains are converted only with diiculty in the presence of high boiling aromatics, while they are converted much more readily in the presence of low boiling aromatics. In the process of my invention, however, the disadvantages hereinbefore mentioned are limited by a novel combination of fractionation. The low boiling fraction of the charge stock is not reformed in the presence of the low boiling fraction of the predominantly parainic ranate and, therefore, the competing reactions are not present. The low boiling fraction of the primary charge and the high boiling fraction of the predominantly paranic rainate are reformed in admixture. Since the constituents of each of these fractions are in a different boiling range and since, generally, each of these fractions is best reformed by dierent reforming reactions, more eiicient use is made of the available catalyst surface and higher yields and higher octane numbers are achieved in the process.

The primary charge stocks which may be reformed in accordance with my process comprise hydrocarbon fractions that boil within the gasoline range and that contain naphthenes and paraflins. The preferred stocks are those consisting essentially of naphthenes and parans, although aromatics and minor amounts of oleiins 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 commonly 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 of the 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 accordance with the present invention, a charge stream, comprising a fraction of the primary charge and a fraction of a rainate recycle, is subjected to a reforming operation in a reforming zone maintained at reforming conditions. In accordance with the invention the charge to the reforming zone may be a mixture of a low boiling portion of the primary charge and a high boiling portion of the predominantly parainic ranate, or the charge may be a high boiling portion of the primary charge and a low boiling fraction of the predominantly parainic ranate. The low boiling fraction of the primary charge preferably has an initial boiling point within the range of from about 150 F. to about 250 F. and an end point within the range of from about 275 F. to about 325 F. The low boiling fraction of the predominantly parainic fraction or'rafnate also preferably has initial and end boiling points within the respective ranges. The high boiling fraction of the primary charge and the high boiling fraction of the predominantly parafnic fraction or raflnate preferably has an initial boiling point within the range of from about 250 F. to about 320 F. and an end boiling point within the range of fromV about 330 F. to about 425 F. These charge streams are separately reformed and when the same reforming zone is utilized the charge streams are separately reformed in a blocked-out type of operation. Either of the charge streams may be reformed first followed by the reforming of the other charge stream. For a better understanding of the invention the original charge stock, that is the charge stock to the first fractionator is referred to as the primary charge. The reforming reactor charge will, therefore, be either a low boiling fraction of the primary charge and a high boiling fraction of the rafnate, or a high boiling fraction of the primary charge and a low boiling fraction of the raffinate.

Various types of desirable and suitable catalysts may be used in the reforming zone of the process, however, the preferred operation utilizes a supported platinum catalyst in the reforming zone. The catalyst that may be used in the reforming zone of my invention comprises those reforming catalysts that permit dehydrogenation of naphthenic hydrocarbons, hydrocracking of paraflinic hydrocarbons, isomerization of paraflinic hydrocarbons, and dehydrocyclization of paraflinic 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 my U. S. Patent No. 2,479,109, issued August 16, 1949. Other catalysts such as molybdenaalumina, chromia-alumina, and platinum on a support, such as a cracking catalyst base may be used. The platinum concentration in the preferred catalyst may range up to about by weight 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 catalysts but preferably are present in an amount of from about 0.1% to about 3% by weight of the nal catalyst 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 ions, the bromide ions, and iodide ions.

The conditions in the reforming zone should be such that substantial conversion of naphthenes to aromatics, relatively mild hydrocracking of parains, isomerization of paratns, and dehydrocyclization of paraifins are induced. Usually the conditions in the reforming zone are, a temperature within the range of from about 600 F. to about 1000 F., a pressure of from about 50 to about 1000 pounds per square inch, 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. It is preferred that the reforming reactions 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 hydrogen from an external source or to recycle hydrogen within the process. However, it may 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 sufficient hydrogen atmosphere in the reaction zone. The hydrogen present in the reaction zone may be within the range of from about 0.5 to about 20 mols of hydrogen per mol of hydrocarbon. In some cases the gas to be recycled will contain hydrogen sulde introduced with the charge or` liberated by the catalyst and it is within the scope of the present invention to treat the hydrogen-containing gas to remove hydrogen sulfide or other impurities before recycling the hydrogen to the reforming zone. At these conditions there are substantially no olefms present in the effluent stream from the reaction Zone.

The effluent from the reforming zone is usually passed through a cooler and into a separator. In the separator a separation is effected to provide a gaseous hydrogencontaining stream and an aromatic-rich hydrocarbon stream. 'At least a portion of the hydrogen-rich gas stream is recycled to the reforming reactor. The aromatic-rich hydrocarbon stream is usually passed to a stabilizer which effects the separation of the normally gaseous material which comprises hydrogen, hydrogen sulfide, ammonia, and hydrocarbons containing from one to four carbon atoms per molecule, from the normally liquid hydrocarbons. A more concentrated aromatic fraction is then obtained in accordance with the present invention by subjecting the reformate, containing aromatic hydrocarbons to a separation process subsequent to being -suitably treated to improve its characteristics as a charge stock for the separation process.

Any suitable separation process may be used to separate the reformate into a predominantly para'inic fraction and a predominantly aromatic fraction. Suitable processes are solvent extraction, solid absorption, fractional crystallization, etc. Of these the solvent extraction process is preferred since it appears to form a predominantly parainic fraction that is most suitable for recycling to the reaction zone. v

Solvent extraction processes are used t-o separate 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. It is frequently desirable to separate various substances by solvent extraction when the substances to be separated have similar boiling points, are unstable at temperatures at which fractionation is effected, form constant boiling mixtures, etc. It is particularly desirable to separate aromatic hydrocarbons from a petroleum fraction containing these aromatic hydrocarbons by solvent extraction because a petroleum fraction is normally a continuous mixture of hydrocarbons whose boiling points are extremely close together and because the petroleum fraction contains numerous cyclic compounds which tend to form constant boiling or azeotropic mixtures. As hereinoefore stated, the ybasis of a solvent extraction separation is the diiference in solubility in a given solvent of one `of the substances to be separated from the other. It may, therefore, be -seen that the more extreme this difference, the easier the separation will be, and an easier separation reects itself process-wise, in less expensive equipment and greater yields per pass in the use of processing equipment as well as in higher purity of product.

A particularly preferred solvent for separating aromatic hydrocarbons from non-aromatic hydrocarbons is a mixtue of water and a hydrophilic organic solvent. Such a solvent may have its solubility regulated by adding more or less water. Thus, by adding more water to the solvent, the solubility of all components in the hydrocarbon mixture are reduced, but the solubility difference between the components is increased. This effect is reected process-wise in less contacting stages required to obtain a given purity of product, however, a greater 7 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 in the mixture is selected to regulate the solubility in the solvent of the materials to be separated. Suitable hydrophilic organic solvents include alcohol, glycols, aldehydes, glycerine, phenol, etc. Particularly preferred solvents are diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, and mixtures thereof containing from about 2% to about 30% by weight of water.

In classifying hydrocarbon and hydrocarbon type cornpounds according to increasing solubility in such a solvent, it is found that the solubility of the various classes increases in the following manner: the least soluble are the paratins followed in increasing order of solubility by naphthenes, oleins, diolelins, acetylenes, sulfur, nitrogen, and oxygen-containing compounds and aromatic hydrocarbons. It may thus be seen that a charge stock which is rich in unsaturated compounds will present a greater problem in solvent extraction than a .saturated charge stock since the unsaturated compounds fall between the parai'lins and aromaties in solubility. It may be seen that an ideal charge to solvent extraction is one containing paraflinic and aromatic hydrocarbons exclusively.

The paralhnic compounds also differ in their relative solubility in the solvent. The solubility appears to be a function of the boiling point of the parah'in, with the lower boiling or lighter parains being more soluble than the higher boiling or heavier parains. Therefore, when heavy paraliins are dissolved in the solvent, they may be displaced from the solvent by adding lighter paratlins thereto. In an embodiment of this invention it is preferred to recycle the heavier paramns to the reforming zone and therefore a light paraflin is charged to the extraction zone to displace these heavier parains from the solvent by putting the heavier paraiiins into the rafiinate phase.

In accordance with the present invention the raffinate, which comprises predominantly paraflinic hydrocarbons, is passed to a fractionation zone wherein the raiiinate is fractionated into at least two fractions, a low boiling fraction and a high boiling fraction. The low boiling fraction of the ratiinate is combined with the high boiling fraction of the primary charge stock as hereinbefore specified and the high boiling fraction of the raffinate is combined with the low boiling fraction `of the primary charge stock as hereinbefore specified. Each of these combined streams is separately reformed in accordance with the present invention.

Additional features and advantages of my invention will be apparent from the following description of the accompanying drawing which illustrates a particular method for conducting a gasoline upgrading operation in accordance with the present invention.

Referring nowto the drawing, a straight-run gasoline fraction having an initial boiling point of 200 F. and an end boiling point of 400 F. is passed through line 1, is picked up by pump 2, and discharged through line 3 containing valve 4 intovfractionator 5. A low boiling fraction'having an end point of about 300 F. is removed overhead from fractionator 5 through line 6, passes through cooler 7, line 8, and into receiver 9. A portion of the light or low boiling fraction in receiver 9 may be removed through line 12. Another portion is removed from receiver 9 through line 10 and passes through line 11 into an upper portion of fractionator 5 as retiux. Another portion of the low boiling fraction having an initial boiling point of V200 F. and an end point of 300 F. is removed through line lt) `and passes through lines 13 and 13 into storage tank 14. A high boiling portion of a rainate, prepared as hereinafter specified, also enters storage tank 14 through lines 77 and 13. A heavy or high boiling fraction having a boiling range of from about 300 F. to Vabout 400 F. is withdrawn from fractionator 5 through line l5 and passes through lines l and 18' into storage tank 19. A low boiling fraction of a ratiinate, prepared `as hereinafter specified, is also passed into storage tank 19 through lines 71 and 13'. Heat is provided for the fractionation in fractionator 5 by reboiler 16 with connecting lines l5 and 17.

ln the operation illustrated in the drawing, a single reaction zone Z7 is utilized; however, two or more in series or parallel may be used. The charge materials in storage tanks 14 and 19 are separately passed through reactor 27. ln the operation herein illustrated valve 26 may be assumed to be closed and valve 2h opened. The charge material in storage tank 14 is withdrawn through line 2l containing open valve 20 and mixes with hydrogen recycle in line 22 and the combined stream in line 23 passes into heater 24 wherein the combined stream is heated to a temperature of 900 F. The heated combined stream is withdrawn from heater 24 by way of line E5 vand passes into reforming reactor 27.

AReforming reactor 27 contains a bed of spherical catalyst of approximately 1A; inch diameter containing 0.4% platinum, 0.1% combined fluorine, and 0.5% combined chlorine. The pressure in the reactor is 500 pounds per square inch, the weight hourly space velocity 4,A and the hydrogen to hydrocarbon mol ratio 5 to l. During the passage of the charging stock through reactor 27 the buik of the naphthenes containing six or more carbon atoms per molecule are dehydrogenated to the corresponding aromatics and a portion of the paraiiins are hydrocracked to lower boiling parafns. Some isomerization of the paraffins also takes place. This reaction being of particular importance in the case of normal hexane as this hydrocarbon is of relatively low octane number and does not readily dehydrocyclicize. The important octane number Vincreasing reaction of dehydrocyclization also occurs in reactor 27. By this reaction, a substantial portion of the paraftins are converted into aromatics.V This reaction is extremely important in increasing the octane number of the paraffins which are recycled to the reforming reactor through line 77. The conditions in the reforming zone or reactor 27 are such that there are substantially no olenic substances produced.

The eliiuent from reactor 27 passes through line 28, cooler 29, line 28 and into separator or receiver 30. Hydrogen is withdrawn from the top of receiver 36 through line 3l. Makeup hydrogen or hydrogen added to the system may be added through line 32 containing valve 33. Excess hydrogen may also be withdrawn through line 32` At least a portion of the hydrogen in line 31 passes through line 36 and is picked up by compressor 37 'and discharged into line 22 and combines with the charge in line 2l and the combined stream passes through line 23 into heater 24,

The liquid hydrocarbons, comprising the reformate and the bulk of the normally gaseous hydrocarbons produced in the process, are withdrawn from receiver 30 through line 38 and passed into fractionator or stabilizer 40. Normally gaseous hydrocarbons are removed overhead through line 41. In stabilizer 4t) the normally gaseous material, which includes hydrogen, ammonia, hydrogen sulfide, and hydrocarbon gases containing from one to four carbon atoms per molecule, is separated from the hydrocarbon liquid comprising aromatic hydrocarbons and parainic hydrocarbons.

The gaseous material passes overhead through line 41 into cooler 42, wherein a portion of the material is condensed and the entire stream passes through line 43 into receiver-44. ln receiver 44 the liquid phase and the gaseous phase of theoverhead material separate. The gaseous phase passesthrough line 46 from which it may be vented to the atmosphere or used as fuel or else it may be further used in the present process or other processes. Thev stabilizer has heat provided thereto by reboiler 48 and connecting lines 47 and d". The conditions in the stabilizer 40 may be such that C4 and lighter components are removed as overhead, however, the gasolinetherein may be cutdeeper, that is C or C5 hydrocarbons may be removed overhead through line 41. However in the usual operation only C., and lighter components are removed as overhead. It is contemplated that the stabilizer and receiver will operate at a sufficient pressure to liquefy at least a portion of the overhead material so that a liquid reliux stream may be available to improve the separation in stabilizer di?. The liquid reflux passes from receiver 44 through line 45 into an upper portion of stabilizer 4h.

The stabilizer bottoms which, as hereinbefore stated, comprise substantially parafnic and aromatic hydrocarbons, are passed through lines 47 and 50 into a lower portion of extractor 52. In extractor 52 the hydrocarbon material rises and is counter-currently contacted at 300 F. and 165 pounds per square inch pressure, in the liquid phase with a descending stream of a selective solvent. In this embodiment diethylene glycol is used, with the latter entering the upper portion of extractor 52 through line 53. Water may also be introduced into extractor 52 through line 58 containing valve 59 which is shown aS entering the top of extractor 52; however, the water may also be added to line 53. The water content of the diethylene glycol and water mixture is maintained at about 3% in this embodiment. As hereinbefore mentioned, the water is added to increase the selectivity of the sol vent in line 53. As a result of the countercurrent contact of the selective solvent and hydrocarbon stock, the aromatic hydrocarbons contained in the charge stock in line 50 are selectively dissolved in the solvent thereby forming an extract stream containing the solvent and the bulk of the aromatic hydrocarbons and a predominantly paraflinic raffinate stream containing the bulk of the paraffinic hydrocarbons.

The raffinate stream passes from the upper portion of extractor 52 through line 54 while the extract stream passes from the lower portion of extractor 52 through line 56. The liquid in line 56 is introduced to stripper 60 wherein the dissolved aromatic hydrocarbons and Inino1- quantities of dissolved paraflins are separated from the selective solvent. The separation in stripper 60 is not diicult in that the aromatic hydrocarbons are substantially different in nature from the selective solvent as well as having a substantially different boiling point. The aromatic hydrocarbon stream along with some light parains passes overhead through line 61 and may be recovered as product or subjected to a further rectification or purification step. Heat is provided for the stripping operation by reboiler 63 and connecting lines 62 and 64. The solvent stream is taken from the bottom of stripper 60 through line 53 and is passed into the upper portion of extractor 52.

The rainate stream from extractor 52 which is withdrawn through line 54 is passed into rafnate fractionator 51. The raffinate may contain dissolved or entrained solvent and may be subjected to a settling and/or washing operation to remove the solvent from the hydrocarbons. The raffinate may contain components lighter than it is desired to catalytically reform and also the raffinate may contain components that are heavier than it is desired to reform, and these components may be removed in fractionator 51. The primary purpose of fractionator 51 is to separate the raflinate into a low boiling fraction and a high boiling fraction. In the embodiment herein illustrated, material having an end point of 200 F. is taken olf overhead through line 66, passes through cooler 67 and line 68 into overhead receiver 69. A portion of the liquefied material in receiver 69 may be removed through line 70. A portion of the liquefied material is also returned to an upper portion of fractionator 51 through line 70 as reflux toy aid inthe sepafation of :components in the fractionator 51. In the embodiment illustrated therefore components boiling below about 200 F. are removed as overhead. Itis generally undesirable to reform components having a boiling point above about 400 F. since it has been found that these heavy components generally tend to deposit coke on the catalyst and thereby deactivate the catalyst. In the embodiment herein illustrated components boiling above about 400 F. are removed through lines 74- and 74. Heat is provided for the'fractionation in fractionator 51 by reboiler 75 and connecting

lines

74 and 76. The withdrawal lines 71 and 77 are located on the column and the column operated so that the material withdrawn from fractionator 56 through line 71 has a boiling range of about 200 F.-300 F. The high boiling fraction removed through line 7'7 has a boiling range of about 300 F.-400 F. A portion of the low boiling raffinate in line 71 may be removed through line 72 containing valve 73 and the remaining portion is passed through line 71 and line 18 into storage tank 19 wherein it is vmixed with the high boiling fraction of the primary charge introduced into storage tank 19 through lines 18 and 18'.

Similarly a portion of the high boiling fraction of the raffinate in line 7'7 may be withdrawn through line 73 containing valve 79 and the remaining portion in line 77 passes through line 13 into storage tank 14. In storage tanke 14 the heavy raflinate fraction introduced through lines 77 and 13 is mixed with the light fraction of the primary charge introduced into storage tank 14 through lines 13 and 13.

After a period of operation in which valve 26 is closed and valve 20 open, the operaion is switched to reforming the material in storage tank 19 by opening valve 26 and closing valve 20. In this operation the material in tank 19 passes through line 26', valve 26, mixes with the hydrogen recycle in line 22 and the combined stream in line 23 passes into heater 24. After a period of operation on the charge stock in storage tank 19 valve 26 may be again closed and valve 20 opened to reform the charge Y material in storage tank 14.

Although the process illustrated in the drawing represents one of the preferred forms of my invention, it is to be understood that my invention is not limited thereby. A number of variations may be introduced into the process without departing from the scope of said invention.

The following examples are given to further illustrate my invention, but are not given for the purpose of unduly limiting the generally broad scope of said invention.

EXAMPLE I Table Charge Stock Product Percent; Ischexaue, Net Percent Methyl- Mol Percent Benzene, n-Hexano eycloof Total Mol Percent pentane I-Iexanes From the above table it may be noted that the presence of a naphthene markedly decreased the isomerization of n-hexane. In my invention after the methylcyclopentane is converted the n-hexane may be recycled to the reaction zone for isomerization.

EXAMPLE II A naphtha fraction having an initial boiling point of 178 F. and an end boiling point of 398 F. is passed through a bed of platinum-alumina-combined halogen catalyst comprising alumina containing 0.3 by weight of platinum and 0.2% by weight of iiuorine, at a pressure of 700 pounds per square inch, a hydrogen to hydrocarbon mol ratio of 7, a weight hourly space velocity of 4, and an initial average catalyst temperature f 905 F.

The effluent from the reaction zone is cooled and the C4 and lighter components removed by fractional distillation. The remaining liquid is countercurrently contacted in a sieve deck tower With a descending stream of 96% diethylene glycol and 4% water. The contact is effected at 315 F. and approximately 150 pounds per square inch pressure. The raffinate is removed from the top of the tower and the extract is removed from the bottom of the tower. The aromatics are recovered from the extract by fractional distillation. The raffinate is fractionated to form a low boiling fraction having an initial boiling point of 175 F. and an end boiling point of 300 F. and a high boiling fraction having an initial boiling point of 300 F. and an end boiling point of 400 F. The low boiling fraction is collected in storage tank A and the high boiling fraction of the raiiinate is collected in storage tank B.

After collecting a substantial amount of material in storage tanks A and B the primary charge stock is discontinued from being sent to the reforming reactor and the primary charge stock is now introduced into a fractionator. In the fractionator the 178 F.-398 F. primary charge is fractionated into a light fraction having an initial boiling point of 178 F. and an end boiling point of 302 F. and a high boiling fraction having an initial boiling point of 302 F. and an end boiling point of 398 F. The light fraction of the primary charge stock, that is the 178 F.-302 F. fraction is passed into storage tank B wherein it is mixed with ti e 300 F.-400 F. fraction of the predominantly parafiinic raffinate. The 302 F.- 398 F. fraction of the primary charge is passed into storage tank A wherein it 'is mixed with the 175 F.- 300 F. fraction of the predominantly parainic raffinate.

The mixture in charge tank A is passed through the bed of platinum-alumina-silica catalyst at the conditions hereinbefore specified and the etiluent is solvent extracted with diethylene glycol at the conditions hereinbefore specified and the raffinate obtained fractionated to provide a 175 F.-300 F. fraction which is recycled to storage tank A and a 300 F .-400 F. fraction which is passed to charge tank B. After a period of operation on charge tank A, the operation is discontinued and the charge material in charge tank B is separately reformed. After discontinuing the operation on the charge material in charge tank B the charge tanks may again be switched and the material in charge tank A reformed.

I claim as my invention:

l. A hydrocarbon conversion process which comprises catalytically reforming gasoline boiling hydrocarbons in a reforming zone, separating from the eiiuent of the reforming zone a predominantly aromatic fraction and a predominantly parafhnc fraction, fractionating the lastnamed fraction into a light parainic fraction boiling below about 325 F. and a heavier parafnic fraction boiling below about 425 F., separately fractionating a straightrun naphtha and separating therefrom a light naphtha fraction boiling below about 325 F. and a heavier naphtha fraction boiling below about 425 F., commingling said light naphtha fraction with said heavier paraffmic fraction and supplying the resultant mixture to said reforming zone,commingling Vsaid heavier naphtha fraction with said light parailinic fraction and catalytically reforming the mixture thus formed independently of the first-mentioned mixture.

2. A hydrocarbon conversion process which comprises reforming gasoline boiling hydrocarbons in contact with a reforming catalyst, separating from the reformed products a predominantly aromatic fraction and a predominantly paranic fraction, fractionating the lastnamed fraction into a light parainic fraction boiling below about 325 F. and a heavier parafnic fraction boiling below about 425 F., separately fractionating a straightrun naphtha and separating therefrom a light naphtha fraction boiling below about 325 F. and a heavier naphtha fraction boiling below about 425 F., commingling said light naphtha fraction Withsaid heavier paraifinic fraction, commingling said heavier naphtha fraction with said light parafnic fraction and alternately reforming the resultant mixtures in the presence of said catalyst.

3. A hydrocarbon conversion process which comprises -catalytically reforming gasoline boiling hydrocarbons in a reforming zone, separating from the effluent of the reforming zone a predominantly aromatic fraction and a predominantly parainic fraction, fractionating the lastnamed fraction into a low boiling paratinic fraction having an initial boiling point within the range of from about F. to about 250 F. and an end boiling point within the range of from about 275 F. to about 325 F. v

and a high boiling parafnic fraction having an initial boiling point within the range of from about 250 F. to about 320 F. and an end boiling point within the range of from about 330 F. to about 425 F., separately fractionating a straight-run naphtha and sepa rating therefrom a low boiling naphtha fraction 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 275 F. to about 325 F. and 'a high boiling naphtha fraction having an initial boiling point within the range of from about 250 F. to about 320 F. and an end boiling point within the range of from about 330 F. to about 425 F., commingling said low boiling naphtha fraction with said high boiling paraffinic fraction and supplying the resultant mixture to said reforming zone, commingling said high boiling naphtha fraction with said low boiling parafiinic fraction and'catalyticallyv reforming the mixture thus formed independently of the first-mentioned mixture.

4. A hydrocarbon conversion process which comprises reforming gasoline boiling hydrocarbons in a reforming zone in the presence of hydrogen and a platinum-containing catalyst, subjecting resultant reformed products to solvent extraction to separate therefrom a predominantly aromatic fraction and a predominantly paraflinic raflinate, fractionating said rainate into a low boiling paranic fraction 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 275 F. to about 325 F. and a high boiling predominantly paranic fraction having an initial boiling point within the range of from about 250 F. to about 320 F. and an end boiling point within the range of from about 330 F. to about 425 F., separately fractionating a straight-run naphtha and separating therefrom a low boiling naphtha fraction 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 275 F. to about 325 F. and a high boiling naphtha fraction having an initial boiling point within the range of from about 250 F. to about 320 F. and an end boiling point within the range of from about 330 F. to about 425 F., commingling said low boiling naphtha fraction with said high boiling parafnic fraction and supplying the resultant mixture to said reforming zone, commingling said high boiling naphtha fraction with said low boiling paranic fraction and independently reforming the mixture thus formed in 13 the presence of hydrogen and a platinum-containing catalyst.

5. The process of claim 3 further characterized in that said mixtures are independently reformed by alternate processing thereof in said reforming zone.

6. The process of claim 4 further characterized in that said mixtures are independently reformed by alternate processing thereof in said reforming zone.

References Cited in the le of this patent UNITED STATES PATENTS Burk et al. June 8, 1943 Goldsby Ian. 1, 1946 Tarnpoll Feb; 28, 1956 FOREIGN PATENTS GreatV Britain Dec. 15, 1954

Claims

1. A HYDROCARBON CONVERSION PROCESS WHICH COMPRISES CATALYTICALLY REFORMING GASOLINE BOILING HYDROCARBONS IN A REFORMING ZONE, SEPARATING FROM THE EFFLUENT OF THE REFORMING ZONE A PREDOMINANTLY AROMATIC FRACTION AND A PREDOMINANTLY PARAFFINC FRACTION, FRACTIONATING THE LASTNAMED FRACTION INTO A LIGHT PARAFFINIC FRACTION BOILING BELOW ABOUT 325*F. AND A HEAVIER PARAFFINIC FRACTION BOILING BELOW ABOUT 425*F., SEPARATELY FRACTIONATING A STRAIGHTRUN NAPHTHA AND SEPARATING THEREFROM A LIGHT NAPHTHA FRACTION BOILING BELOW ABOUT 325*F. AND A HEAVIER NAPTHA FRACTION BOILING BELOW ABOUT 425*F., COMMINGLING SAID LIGHT NAPHTHA FRACTION WITH SAID HEAVIER PARAFFINIC FRACTION AND SUPPLYING THE RESULTANT MIXTURE TO SAID REFORMING ZONE, COMMINGLING SAID HEAVIER NAPHTHA FRACTION WITH SAID LIGHT PARAFFINIC FRACTION AND CATALYTICALLY REFORMING THE MIXTURE THUS FORMED INDEPENDENTLY OF THE FIRST-MENTIONED MIXTURE.