US2768126A - Multiple stage reforming process - Google Patents

Description

V. HAENSEL ET AL MULTIPLE STAGE?` REFORMING PROCESS Oct. 23, 1955 Filed Feb. 23, 1952 BOLVNOILOVHS' HOLOVSH HOLOVB U Ill.

nited States Patent MULTIPLE STAGE REFORMING PROCESS Vladimir Haensel and Henry W. Grote, Hinsdale, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application February 23, 1952, Serial No. 273,102 Claims. (Cl. 196-50) This invention relates to a method for reforming gasoline fractions to provide both motor fuel and aviation gasoline. More specifically, the improved operation provides a multiple step integrated and combined process for converting oletinic gasolines, or alternatively, converting both cracked and straight-run `gasolines to high octane fuels.

Where cracked gasolines, or other olenic naphthas and gasolines, are to be reformed, it is desirable to subject the stream to saturation by hydrogenation prior to carrying out the reforming step. In the catalytic reforming operation, there is normally some hydrocracking and isomerization of parans, as well as the dehydrogenation of naphthenes, in order to effect the overall increase in octane number. It is a principal feature of a part of the present improved process to effect the reforming in the presence of an improved substantially non-regenerative catalyst comprising platinum-alumina and combined halogen. As a rst step of the present process, a catalytically or thermally cracked gasoline fraction, together with hydrogen,fis passed into contact with a suitable hydrogenation catalyst prior to entering the reforming zone. The hydrogenation catalyst is preferably cornposed of platinum and alumina, either with or without combined halogen, however, a cob,alt-'molybdenumalumina catalyst or other sulfur resistant catalyst may be used Vto advantage.

In the reforming step, in orderto obtain a high degree of the aromatization of the naphthenic components in the naphtha or gasoline stream, the saturated stream is also preferably subjected to dehydrogenation inthe presence of an improved platinum-alumina-combined halogen catalyst. This catalyst is a recently developed reforming catalyst of superior quality providing superior conversion results under long periods of use, being substantially non-regenerative when used under proper conditions. Where a straight-run gasoline fractionis to be reformed along with the olefinic fraction, the former may be introduced directly into the dehydrogenation zone in admixture with the hydrogenated stream.

Also, as a part of the present improved combined operation, after the dehydrogenation, the resulting aromatics are separated from the non-aromatic portion of the product stream. These non-aromatics are subjected to. hydrocracking in" the presence of a suitable hydrocracking catalyst and hydrogen which is obtained from the dehydrogenation stage, with the conversion effected at a higher pressure than that maintained in the aromatization step. A platinum-aiumina-combined halogen catalyst may be used advantageously in this hydrocracking'step, however, it is not intended to limit the present improved combined operation to that material alone. For example, a hydrogenation and cracking catalyst such as a silica-aluminanickel composite may be used to advantage in the hydrocracking step.

It is a principal feature of the present invention to provide a desirable multiple step combined reforming operation whereby the resulting productstreams Vare suitable for both high octane motor andl aviation fuels'.

' velocity in this step may also be in the range of 2,768,12 vifatented Oct. 23, 1956 into contact with a sulfur resistant hydrogenation catalyst and effecting the saturation thereof, contacting the resulting hydrogenated fraction with hydrogen and a platinum-alumina catalyst at reforming conditions effecting the dehydrogenation and aromatization thereof, cooling and separating the resulting product stream to provide a liquid stream and gaseous hydrogen containing stream, separating aromatic hydrocarbons and non-aromatic hydrocarbons from the liquid stream, passing the nonaromatic hydrocarbons together with hydrogen into contact with a hydrocracking catalyst at conditions effecting the hydrocracking thereof, cooling the resulting hydrocracked product stream and separating it to provide a liquid stream and a gaseous hydrogen containing stream, recycling the latter into contact with the olenic hydrocarbon fraction as the hydrogen stream being mixed therewith, and fractionating the resulting hydrocracked liquid boiling stream to provide a high boiling fraction suitable for motor fuel and a low boiling fraction suitable for aviation fuel.

In a preferred embodiment of the present combined operation, substantially different operating conditions are utilized in the various contacting zones in a manner providing optimum conversion conditions. Thus, in the rst stage of contact where the catalytically cracked fraction or olefinic fraction is saturated, conditions favoring hydrogenation are utilized, with temperatures within the range of from about 550 F. to about 850 F., while at a pressure of greater than p. s. i. g., say in the range of from about 100 to 800 p. s. i. g. The space velocity (which is defined as the weight of hydrocarbon charge per hour per weight of catalyst in the reaction zone) may be relatively high, say in the range of from about l to 50, and the hydrogen to hydrocarbon mole ratio in the range of from about l to 10.

The dehydrogenation stage is favored at high temperatures, say of the order of from about 600 F. to about 1000 F., and lower pressures, say in the range of from about 50 to 600 p. s. i. g. and preferably less than about 500 p. s. i. g. The space velocity through the dehydrogenation zone may also be relatively high, say Within the range of from about 0.5 to 30, while the hydrogen to hydrocarbon ratio may also be of the order of from about l to l0.

The hydrocracking step, for the non-aromatic fraction, is favored at a slightly lower temperature than that in the dehydrogenation Zone, say of the order of from about 550 F. to 750 F., and at high pressure, say within the range of from 500 p. s. i. g. to 2000 p. s. i. g. The space from about 0.5 to 30, while the hydrogen to hydrocarbon molal ratio may be in the range of from about l to l5 and preferably above about 4.0.

The platinum-alumnia-combined halogen catalyst, which is preferred for use in our combined reforming processes may contain substantial amounts of platinum, but for economic as Well as yield and quality reasons, the platinum content usually will be within the range of from about 0.05% to about l1.5%. The concentration of halogen ion in the reforming and hydrocracking catalyst may be within the range of from about 0.1% to about 8% by weight of the alumina on a dry basis. However, the fluoride ion appears to be more active than the chloride ion and therefore will be used within the range of from about 0.1% to about 3% by weight of the alumina on a dry basis. The chloride ion may be used within the range of from about 0.2% to about 8% by weight of the alumina on a dry basis. Of course, both fluoride and chloride ions may be used together to provide the halogen containing catalyst. Bromide and iodide ions may be used, but have been found to provide a lesser activity and preferably the aforementioned fluoride and chloride ions are combined with the platinium-alumina catalysts.

Reference to the accompanying diagrammatic drawing and description thereof will aid in more clearly setting forth the combined and integrated steps of the present invention for producing premium fuels for both aviation and automobile use.

Referring now to the drawing, there is shown a cracked gasoline fraction having a 200-400 F. end point, passing by way of line 1 and valve 2 through a suitable heater 3 in admixture with a hydrogen stream, obtained as will be set forth hereinafter and entering from line 4. The combined gasoline stream and hydrogen is heated to a temperature within the range of from about 550 F. to about 850 F., and in a specific embodiment say to about 700 F. This heated hydrocarbon and hydrogen stream passes through line 5 at a pressure of say about 600 p. s. i. g. into a hydrogenation reactor 6 and into contact with a suitable sulfur resistant catalyst, which in a desirable substantially non-regenerative operation may be the platinum-alumina-combined halogen catalyst as described hereinbefore, or alternatively a platinum-aluminacatalyst without halogen combined therewith. In the reactor 6, the olefins are converted to provide corresponding saturated parafns and the cyclo-olefins are converted to provide corresponding naphthenes. The resulting fraction passes from reactor 6 by way of line 7 and valve 8 into a heater 9 prior to entering the dehydrogenation zone. Actually the hydrogenation step is exothermic so that the saturated stream passed to heater 9 may rcquire but a very small amount of additional heating.

In the particular embodiment shown, a straight-run gasoline fraction, which is preferably debutanized, is combined with the hydrogenated fraction, and is introduced into line 7 by way of line 10 and control valve 11. The combined streams are heated within the furnace 9 to a temperature within the range of from about 750 F. to about 1000 F., and more particularly in this embodiment, to about 900 F. prior to being introduced into the first dehydrogenation reactor 12, by way of line 13. The hydrocarbon stream preferably contacts the improved platinum-alumina-combined halogen catalyst in reactor 12 at a pressure less than 500 p. s. i. g., say at about 300 p. s. i. g. in order to provide optimum aromatization conditions.

Excess hydrogen is utilized in combination with the stream passing through hydrogenation reactor 6, in order to readily provide for saturation of the stream and so that hydrogen is present to mix with the hydrocarbon stream entering reactor 12, providing a hydrogen to hydrocarbon charge ratio, which is in the range of from about 1 to 10 and preferably at least about 4. The partially aromatized and dehydrogenated stream leaving reactor 12 by way of line 14 and valve 15 enters intermediate heater 16 so that the temperature of the resulting hydrocarbon and hydrogen stream may be again raised to the order of about 900 F. prior to entering a reactor 17 by way of line 18. The dehydrogenation reaction is endothermic and in order to obtain an efficient conversion with a high production of aromatics it is advantageous to maintain a relatively high temperature. It is of course not intended to limit the use of the present invention to any set number of dehydrogenation reactors and accompanying intermediate heaters. Therefore, while two reactors are indicated, it is to be understood that three or more may be incorporated in the unit.

A resulting reformed stream, with substantially all of the naphthenes amortized, and with hydrogen formed in the reactors 12 and 17, leaves reactor 17 by way of line 19 and valve 20 to become cooled in a suitable heat exchanger or cooling means 21 and pass from the latter by way of line 22 into a separating zone 23. In the separating zone 23, a gaseous hydrogen containing stream is withdrawn from the upper portion thereof by way of line 24 and valve 25, while a liquid dehydrogenated stream is withdrawn from the lower portion of the separator by way of line 26 and valve 27. In accordance with the combined operation of the present process, the liquid stream from line 26 is passed into a fractionating zone 28 to effect the debutanization thereof. The resulting gaseous fraction, containing butane and lighter components, is discharged from the upper portion of the fractionator 28 by way of line 29 and valve 30, and may be used as a gaseous fuel. The debutanized liquid fraction is withdrawn from the lower portion fractionator 28 by way of line 31 and valve 32 and passed to a suitable aromatic extraction unit indicated at 33. The latter is indicated diagrammatically and may comprise a solvent extraction system, or other suitable separating means to provide the substantially complete separation or extraction of the aromatic components. The aromatic components withdrawn from unit 33 by way of line 34 and valve 35 may be in turn fractionated to provide benzene, toluene, and Xylene. The materials may then be used for aviation fuel blending, or for any other purpose. The nonaromatic components from extraction unit 33 are withdrawn by way of line 36, valve 37, and pump 44 and then passed through heater 38 and line 39, having valve 40, to a hydrocracking zone 41.

In accordance with a specic operation of the present invention, hydrogen separated and passed from the dehydrogenation step by way of separator 23 and line 24 is raised to a high pressure in a suitable compressor or pumping means 42 and passed by way of line 43 into admixture with the non-aromatic stream entering heater 38 by way of line 36. This combined stream is heated lto a temperature as hereinbefore noted, of the order of about 550 F. to 750 F. and preferably say at about 650 F., while at a pressure above 500 p. s. i. g., as hereinbefore noted, and more specifically say at about 800 p. s. i. g., prior to entering the hydrocracking reactor 41.

. The catalyst maintained within reactor zone 41 may be a platinum-alumina-combined halogen catalyst, as previously noted, or a suitable combined hydrogenation and cracking catalyst effecting the selective cracking and branching of this substantially paranic hydrocarbon stream to provide lower molecular weight and higher octane fractions. Also, as previously noted hereinbefore, it is not intended to limit the catalyst to any one material in this particular zone. The resulting hydrocracked fraction from zone 41, together with excess hydrogen, is passed by way of line 45 and valve 46 through cooling means 47 and line 48 to a separator 49. From separator 49, a resulting hydrogen containing gaseous stream is withdrawn by way of line 4 and valve 50, while a resulting hydrocracked liquid fraction is withdrawn by way of line 51 and valve 52. A portion of the hydrogen containing stream or from separator 49 may be vented by way of line 53 and valve 54 to prevent the build up of methane or other light gases, however, the larger portion of the stream is recycled to the hydrogenation zone to combine with the cracked gasoline stream entering line 1 as hereinbefore set forth. It is also to be noted that the separator 49 is maintained at a substantially high pressure, say of about 700 p. s. i. g., permitting the discharge of the hydrogen stream into the hydrogenation zone and subsequently into the dehydrogenation zones at lower pressures than that maintained within the hydrocracking step. In other words, the hydrogen stream utilized in. the hydrocrackiiig zone 41` at' about 800 pf S- ismay., hsztdacsd'fa @worden gf about 600 p. s. i. g. atthe hydrogenation reactor 6, and toa still lower' pi'es url e at the' dehydrogenation reactors. The use of arshingle circulatory system forlithe hydrogen stream permits` the use of but a single compressor 421e maintainontinuous movement of the hydrogen through all of the contacting zones. The hydrocracking zone being the highest pressure zone receives the high pressure hydrogen stream resulting from the dehydrogenation zone, and the hydrogen then passes through substantially lower pressure zones, specifically the hydrogenation zone 6 and the dehydrogenation zones 12 and 17 back tothe separator The hydrocracked non-aromatic fraction leaving separator 49 by way of line 51 and valve 52 is passed to a ractionator 55 and therein is debutanized to provide an overhead gaseous fuel stream, of butane and lighter gases that is discharged by way of line 56 and valve 57. A bottoms liquid fraction passes by way of line 58 and valve 59 to another fractionator 60 in order to effect another separation providing an overhead cut of high octane fuel containing C hydrocarbons and fractions boiling to about 185 F. This overhead fraction is indicated as being withdrawn by way of line 61 and valve 62 to provide an aviation fuel, or blending component for aviation fuel. The bottoms fraction is indicated as a 185 F. to 400 F. boiling point cut, withdrawn by way of line 63 and valve 64, and this fraction is particularly suitable as a high octane motor fuel. It is to be noted that the .high degree of branching of the lower boiling parain constituents produced during the hydrocracking step 41 provide the C5 to 185 F. aviation fuel, that is particularly desirable from the standpoint of lean mixture response. Thus, this overhead fraction from line 61 may be blended with portions of the aromatic components, obtained from line 34, to provide a desirable aviation fuel having both good lean and rich mixture response characteristics.

The foregoing describes a particular embodiment of an improved combined process for reforming and increasing the octane number of both cracked and straight run gasoline fractions. However, it is to be noted that, as mentioned in connection with the dehydrogenation step, one or more reactors or contacting steps may be utilized in connection with both the hydrogenation contacting and the hydrocracking contacting, and that where two or more such catalysts contacts are made, suitable intermediate heaters or heating means may be incorporated to maintain desirable temperature conditions. Further, the foregoing indicates that a catalytically or thermally cracked stream, is passed through the first stage of the operation, namely the hydrogenation step, while straight-run gasolines enter directly into the second stage of contact, however, natural gasolines and other uncracked fractions boiling Within the gasoline range and containing little or no oleiins may be also passed directly into the dehydrogenation zone.

We claim as our invention:

1. A method for reforming straight run and cracked gasoline fractions to provide high octane number fuels, which comprises, passing said cracked fraction in the presence of hydrogen into Contact with a sulfur resistant hydrogenation catalyst and effecting the saturation thereof, combining the resulting saturated fraction with the straight run gasoline fraction and passing the mixture in the presence of hydrogen into contact with ya platinumalumina catalyst under reforming conditions and effecting the dehydrogenation and aromatization thereof, cooling and separating the .resulting product stream to provide -a liquid stream and a gaseous hydrogen containing stream,

separating the resulting liquid stream into-aromatic hydrocarbons and non-aromatic hydrocarbons and recovering the former, passing the separated non-aromatic hydrocarbons with at least a portion of said gaseous hydrogen containing stream into contact with a hydrocracking cata- 6 lystl at hydrocracking conditions effecting hydrocracking thereof, cooling'the resulting hydrocracked product stream and separating it to provide a liquid stream anda gaseous hydrogen containing stream, recycling -at least a portion of the latter stream into contact with the cracked hydrocarbon fraction contacting said hydrogenation catalyst, and fractionating the resulting hydrocracked liquid stream to provide a high boiling fraction suitable for motor fuel and a low. boiling fraction suitable for aviation fuel.

2. A method for reforming straight run and cracked gasoline fractions to provide high octane number fuels, which comprises, passing said cracked fraction together with excess hydrogen obtained as hereinafter set forth at a pressure of the order of about 600 p. s. i. g. into contact with a platinum-alumina-combined halogen catalyst and effecting the hydrogenation and saturation of said fraction, combining the resulting saturated fraction with straight rnn gasoline and passing the mixture together with excess hydrogen from said hydrogenation contact at a pressure of less than 500 p. s. i. g. into contact with a catalyst containing platinum-alumina at reforming conditions and effecting the dehydrogenation and aromatization of said combined streams, cooling and separating the resulting dehydrogenated product stream to provide a gaseous hydrogen containing stream and a liquid stream, separating the resulting liquid stream into aromatic hydrocarbons and non-aromatic hydrocarbons and recovering the former, passing the separated non-aromatic hydrocarbons together with at least a portion of said separated gaseous hydrogen containing stream at a pressure greater than 700 p. s. i. g. into Contact with a platinum-alumina combined halogen catalyst and effecting the hydrocraeking of said non-aromatic fractions, cooling the resulting hydrocracked product stream and separating it to provide a liquid stream and a gaseous hydrogen containing stream, recycling at least a portion of the latter into contact with said cracked hydrocarbon charge fraction as the aforesaid hydrogen mixed therewith, and fractionating the resulting hydrocracked liquid stream to provide a low boiling fraction suitable for aviation fuel and a higher boiling fraction suitable for motor fuel.

3. The method of claim 2 further characterized in that said hydrocracked liquid product stream is fractionated and has butanes and lighter materials separated therefrom in a first fractionating step, and the resulting debutanized fraction is separated in a second fractionation step to provide a low boiling fraction containing C5 to about 185 F. boiling point material providing a desirable aviation fuel, and a higher boiling fraction containing F. to about 400 F. boiling point material suitable for motor fuel.

4. The method of claim 2 further characterized in that said cracked fraction undergoing saturation in the presence of said platinuin-alumina-combined halogen catalyst is introduced into contact therewith at a temperature of the order of about 700 F., the resulting saturated cracked fraction and the straight run fraction contacts said platinum-alumina catalyst at a temperature of the order of about 900 F. for effecting said aromatization step, and said non-aromatic fraction contacting said platinum-alumina-combincd halogen catalyst is heated to a temperature of the order of about 650 F. for effecting the hydrocracking thereof.

5. A method for reforming an olefinic hydrocarbon fraction boiling in the gasoline range which comprises catalytically hydrogenating said fraction in the presence of excess hydrogen in a first zone, subjecting the hydrogenated fraction to catalytic dehydrogenation and aromatization in admixture with the excess hydrogen in a second zone, introducing a straight run gasoline fraction to said second zone for conversion therein in admixture with said hydrogenated fraction, separating from the resultant products a hydrogen-containing gas, aromatic hydrocarbons and non-aromatic hydrocarbons, re-

covering the aromatic hydrocarbons, Supplying theV separated non-aromatic hydrocarbons to a third zone maintained under higher pressure than said rst and second zones, increasing the pressure on said hydrogen-containing gas and introducing the same to the third zone, cataw lytically hydrocracking the non-aromatic hydrocarbons in said third zone, separating the normally liquid hydrocracked products from hydrogen-containing gas, and supplying at least a portion of the last-mentioned gas to said rst zone.

References Cited in the le of ,this patent v UNITED STATESYPATENTS l'

Claims (1)

1. A METHOD FOR REFORMING STRAIGHT RUN AND CRACKED GASOLINE FRACTIONS TO PROVIDE HIGH OCTANE NUMBER FUELS, WHICH COMPRISES, PASSING SAID CRACKED FRACTION IN THE PRESENCE OF HYDROGEN INTO CONTACT WITH A SULFUR RESISTANT HYDROGENATION CATALYST AND EFFECTING THE SATURATION THEREOF, COMBINING THE RESULTING SATURATED FRACTION WITH THE STRAIGHT RUN GASOLINE FRACTION AND PASSING THE MIXTURE IN THE PRESENCE OF HYDROGEN INTO CONTACT WITH A PLATINUMALUMINA CATALYST UNDER REFORMING CONDITIONS AND EFFECTING THE DEHYDROGENATION AND AROMATIZATION THEROF, COOLING AND SEPARATING THE RESULTING PRODUCT STREAM TO PROVIDE A LIQUID STREAM AND A GASEOUS HYDROGEN CONTAINING STREAM SEPARATING THE RESULTING LIQUID STREAM INTO AROMATIC HYDROCARBONS AND NON-AROMATIC HYDROCARBONS AND RECOVERING THE FORMER, PASSING THE SEPARATED NON-AROMATIC HYDROCARBONS WITH AT LEAST A PORTION OF SAID GASEOUS HYDROGEN CONTAINING STREAM INTO CONTACT WITH A HYDROCRACKING CATALYST AT HYDROCRACKING CONDITIONS EFFECTING HYDROCRACKING THEREOF, COOLING THE RESULTING HYDROCRACKED PRODUCT STREAM AND SEPARATING IT TO PROVIDE A LIQUID STREAM AND A GASEOUS HYDROGEN CONTAINING STREAM, RECYCLING AT LEAST A PORTION OF THE LATTER STREAM INTO CONTACT WITH THE CRACKED HYDROCARBON FRACTIONC ONTACTING SAID HYDROGENATION CATALYST, AND FRACTIONATING THE RESULTING HYDROCRACKED LIQUID STREAM TO PROVIDE A HIGH BOILING FRACTION SUITABLE FOR MOTOR FUEL AND A LOW BOILING FRACTION SUITABLE FOR AVIATION FUEL.

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