US2322622A - Treatment of motor fuels - Google Patents

Description

June 22, 1943. HE ETAL 2,322,622

TREATMENT OF MOTOR FUELS Filed D90. 28, 1939 c0045?- QEACT//V 1 [7 zmve 1 97 2? i M5 I I l/EA rave/j l5 f WWW. #2

FRAcTIwvArM/G nwaz 3 Tu. L Pam Patented June 22, 1943 UNITED STATES PATENT OFFICE TREATMENT or MOTOR FUELS Herbert G. M. Fischer, Westiield, and Robert P.

Russell, Millburn, N. J., assignors. by mesne assignments, to Standard Catalytic Company, a

corporation of Delaware Application December 28, 1939, Serial No. 311,260

17 Claims.

teristics of the raw material so that a fuel of the desired quality may be produced with minimum loss and with maximum eiliciency. The catalytic treatments in question are catalytic reforming, catalytic isomerization and catalytic polymerization.

The term catalytic reforming wherever used in the specification and claims shall be understood to mean any process of subjecting material consisting essentially of hydrocarbons substantially boiling in the gasoline range to heat treatment at a temperature in excess of 500 F. and in the presence of catalysts to produce a dehydrogenated or otherwise chemically reconstructed product, for example of anti-knock characteristics superior to those of the starting material, with or without an accompanying change in molecular weight. By the term chemically reconstructed is meant something more than the mere removal of impurities or ordinary finishing treatments. The term catalytic reforming shall be understood to include, but not by way of limitation, reactions such as dehydrogenation, aromatization or cyclization, desulfurization and alkylation, all or some of which may occur to a greater or lesser extent during the process.

The term catalytic isomerization" wherever used in the specification and claims shall be understood to mean any process of subjecting materials consisting essentially of hydrocarbons substantially boiling in the gasoline range and rich in olefinic hydrocarbons to heat treatment at a temperature in excess of 500 F. and in the presence of normally solid catalytic materials to produce a product containing isomeric forms of the olefinic hydrocarbons or an otherwise chemically reconstructed product having anti-knock characteristics superior to those of the starting material, with or without an accompanying change in volatility, and with or without an accompanying change in molecular weight.

The term catalytic polymerization wherever used in the specification and claims shall be understood to mean any process of subjecting materials consisting essentially of hydrocarbons substantially boiling in the gasoline range to heat treatment at a temperature in excess of 300 F. and in the presence of catalysts to cause linking of lower molecular weight hydrocarbons to produce higher molecular weight compqunds having essentially the same carbon to hydrogen ratio and to cause, through the reduction of impurities or the elimination of undesirable secondary properties, an improvement in quality without important change of the primary constitution and properties of the hydrocarbons which make up the product.

In the process of the present invention all of these catalytic treatments are preferably carried out in the presence of substantial quantities of added hydrogen or gases rich in free hydrogen under conditions such that there is either no overall net consumption of free hydrogen or there is an overall net production of free hydrogen. By overall net consumption or production of free hydrogen is meant that while there may be a net consumption in one catalytic treatment this will be counterbalanced by a net production in another catalytic treatment so that the entire treatment will result in either no net consumption or a net production of free hydrogen. Conducting the catalytic treatments in the presence of hydrogen has several distinct advantages over carrying them out in the absence of hydrogen. There are (1) the length of time the catalyst can be used before it requires regeneration or replacement is substantially prolonged and (2) the yield and characteristics of the product obtained are markedly better. Operating under conditions such that there is no net consumption of hydrogen is especially advantageous because it means that the hydrogen containing gases initially added and those produced in the reactions may be continually recycled without having to add hydrogen from an extraneous source.

In accordance with the present invention, a-

hydrocarbon oil boiling in the gasoline range, such as a naphtha for example, may be subjected to any twoor all of the various catalytic treatments depending upon its characteristics and the characteristics of the product it is desired to produce. The manner in which the process may be carried out will be more fully understood from the following description when read with reference to the accompanying drawing which is a semi-diagrammatic view in sectional from any source.

elevation of one type of suitable apparatus and shows the lines of flow.

Referring to the drawing, numeral i designates a supply tank of hydrocarbon oil to be treated. This oil preferably consists of hydrocarbons substantially boiling in the gasoline range, say between 90 and 500 F., and may have been derived It is immaterial whether the oil is parafiinic, olefinic or naphthenic or whether it is a cracked or virgin material or whether it has a high or low sulfur content. Any type of hydrocarbon oil in this general boiling range, for example a naphtha, may be-treated according to the present invention with advantageous results, although, as will appear below, the initial characteristics of the feed material will determine to a large extent the nature of the treatment to which it should be subjected. Numeral 2 designates a supply tank of hydrogen or a gas rich in free hydrogen. Naphtha is withdrawn from tank I through line 3 by means of pump l and forced through line 5 into and through a heating means 6 mounted in a suitable furnace setting 1. Hydrogen is withdrawn from tank 2 through line I by means of pump 9, and forced through line l into and through a separate heating means H which may be mounted in the same furnace setting as heating means 6 or in a different setting. It is not essential to the operation of the process that the naphtha and hydrogen be heated in sepe arate heating means, but it is preferable from a practical and economic standpoint in order to reduce, pressure drop. It will be understood that both the naphtha and the hydrogen may be heated in the same heating means. The naphtha and hydrogen are heated in heating means 6 and II respectively to such temperature as will be suitable to maintain the reaction zone into which they are to be introduced at the desired temperature level. Hot naphtha and hot hydrogen leave heating means 6 and H through lines l2 and i3 respectively and the two lines converge into line H which carries a mixture of the two into a reaction zone l5 which contains a suitable catalytic material l6 which promotes reforming. The nature of this catalytic material will be more fully disclosed below. Although in the drawing the direction of flow is shown as being upward through reaction zone i5, it will be understood that the direction of. flow may be downward if it is more convenient.

- Reaction zone i5 is maintained under a pressure between slightly above atmospheric and 500 pounds per square inch, preferably between 50 and 400 pounds per square inch, and at a temperature between 800 and 1050 F., preferably between 900 and l000 F. The-rate of flow of naphtha through the reaction zone is between 0.2 and 5.0 volumes of liquid naphtha per volume of cata?yst per hour. Rates between 0.3 and 3.0 v./v./hour are preferred in most cases. The quantity of gas rich in free hydrogen introduced along with the naphtha should be between 500 and 5000 cubic feet of gas per barrel of naphtha, preferably between 1000 and 3000 cubic feet, and this gas should contain between 20 and 90 mol percent of free hydrogen, preferably between 30 and 70 mol percent.

Products of reaction leave reaction zone I 5 through line l1, pass thence through a cooling or heat exchange means l8 wherein they are cooled down to a temperature which will be suitable to maintain the next reaction zone into which said products are to be introduced at the desired level,

and then flow through line I9 into a second re- 75 action zone 20 which contains a catalytic material 2'i' which promotes isomerization. The nature of this catalytic material will be more fully disclosed below.

Reaction zone 20 may be maintained under the same, a higher or a lower pressure than reaction zone i5, preferably between 50 and 400 pounds per square inch and is maintained at an average temperature between 700 and 900 F., preferably at an average temperature between 750 and 850 F. The rate of flow of the hydrocarbon material through reaction zone 20 should be between 0.2 and 5.0-volumes of liquid hydrocarbon material per volume of catalyst per hour. The gas rich in free hydrogen in the products leaving reaction zone i5 also accompanies the other reaction products therefrom through reaction zone 20. It is not generally necessary to add additional hydrogen but this may be, done through line 22 if desired.

Reaction products leave reaction zone- 20 through line 23, pass through a cooling or heat exchange means 24 wherein they are cooledto such temperature as will be suitable to maintain the next reaction zone through which they are to be passed at the desired level, and then flow through line 25 into a third reaction zone 26 which contains a catalyst 21 which promotes polymerization. The nature of this catalyst will also be more fully disclosed below. The entire stream of products leaving reaction zone 20 may be passed through reaction zone 26 and ordinarily it will not be necessary to introduce additional gas rich in free hydrogen, but if this is desired it may be introduced through line 28.

Reaction zone 26 may be maintained under substantially the same pressure as reaction zones i5 and 20 or .under a higher or lower pressure, preferably between 50 and 400 pounds per square inch. The rate of flow of hydrocarbon material through reaction zone 26 may be between 0.2 and 5.0 volumes of liquid hydrocarbon material per volume of catalyst per hour. The temperature in reaction zone 26 is preferably maintained between 400 and 600 F.

- Reaction products leave reaction zone 25 'through line 29, may be passed thence through a cooling or heat exchange means 30 and are then passed through a line containing value 3i into a separating means 32 wherein gaseous and liquid products may be separated.

The gaseous products which will consist chiefly of hydrogen and normally gaseous hydrocarbons such as methane, ethane and propane are removed from the separating means 32 through line 33 and after being recompressed to reaction pressure by means of booster compressor 34 may be returned to the hydrogen supply tank 2 through line 35. During operation, a portion or all of these gases may be recycled directly to the system without being returned to the hydrogen supply tank 2. This may be done by passing the gases through by-pass line 36. From time to time it may be necessary or desirable to release a portion ofthe gaseous products from the system and this may be done through vent line 31.

Prior to recycling the gaseous products to hydrogen tank 2 or directly to the system, all or a portion thereof may be passed through a scrubbing means in order to remove a substantial proportion of the hydrocarbon constituents. In the drawing the scrubbing means is diagrammatically' denoted by numeral 38. Gaseous products flowing through line 35 may be diverted through line 39 into and through the scrubbing of the desired characteristics.

means 38 and then returned to line I! through line 40. The removal of hydrocarbon constituents from the gaseous products may be accomplished by any of several suitable means. Ordinarily, the most convenient method would be to scrub the gases with a hydrocarbon oil such as a naphtha or a gas oil under conditions which will permit the absorption of hydrocarbons but substantially no hydrogen. A portion of the feed to or product of the process may be used for this purpose if desired. Other well-known methods of separating hydrocarbons from mixtures of the same with hydrogen may of course also be used.

Returning to the separating means 32, the liquid products are removed therefrom through line 4| and are then introduced into a fractionating means 42. Hydrocarbon fractions which are too volatile or too low boiling for the desired product are removed from the fractionating tower through line 43. Fractions which are too high boiling for the desired product, for example high boiling polymers, are removed from the fractionating tower through line 44. The desired product is removed from the tower as a side stream through line 45 and is collected in a tank 48. V

The foregoing description is applicable to a type of feed stock which will require all three treatments, 1. e. catalytic reforming in the presence of hydrogen, catalytic isomerization in the presence of hydrogen and catalytic polymerization in the presence of hydrogen in order to produce therefrom the maximum yield of fuel Such a feed stock might, for example, be a virgin naphtha relatively poor in lower boiling fractions and derived from a paraflinic crude. For other types offeed stock, the type of treatment may be varied in accordance with the procedure now to be described.

If the feed stock is one rich in low boiling hydrocarbons, especially low boiling oleflns, for example a cracked naphtha, it may not be desirable to subject the' lower boiling fractions thereof to the first catalytic reforming treatment, because under the action of hydrogen at higher temperatures, the low boiling oleflns which are highly reactive toward hydrogen might be converted to paraf'lins which are less desir-.

able from the standpoint of high octane number.

Therefore when treating a feed stock of this character it is withdrawn from supp y tank I through line 3 by pump 4, and then valve 5a in line 5 is closed, and the naphtha is forced through line 50 into a distillation means ii, wherein the lower boiling fractions are separated from the higher boiling fractions- The higher boiling fractions are removed from the still through line'52 and returned to line 5 which then carries them through the heating means 6 and into reaction zone IS in the manner previously described. The lower boiling fractions are removed from still 5| through line 53, and then after passing through a heating means 54, if necessary, are introduced through line 55 into line H which is carrying reaction products from reaction zone l5 into reaction zone 20. In this way the lower boiling fractions of the feed naphtha are by-passed around the catalytic reforming treatment and are subjected first to catalytic isomerization. It will be understood that the low boiling fractions may be separated from the feed in an entirely separate system and that said low boiling fractions or low boiling fractions derived from any other source may be admitted to line 64 through a line 58. It is preferable in most cases, however, to have the separation system combined with the catalytic system so that the distillation may be sync ronized with the catalytic operations. 1

If the product from the catalytic reforirng step is relatively rich in aromatic hydrocarbons. it may be desirable to have it by-pass the catalytic isomerization treatment in reaction zone 2. so that it is subjected subsequently only to catalytic polymerization. In order to do this the reaction product leaving reaction zone ll through line l1 may be by-passed around reaction zone 20 by closing valves Na and 23a and allowing said products to flow through line 56 and line 23 into reaction zone 26.

In a similar manner it the feed stock is one of such characteristics that suitable polymerizable components do not form to an appreciable extent in the catalytic reforming and catalytic isomerization steps, the catalytic polymerization step may be by-passed. This may be done by passing the products leaving reaction zone 20 through lines 23-and 51 directly into line 29 which carries material into the separating means 32.

Itwill be understood that in all of the above .zone may not require treatment in the next succeeding zone but nevertheless a portion of the products can be treated to advantage therein.

The relative proportions of the products hypassed and not by-passed may of course be adjusted so that a final product of the best characteristics may be obtained with a minimum loss in yield.

The catalyst IS in reaction zone l5 may comprise any one or more of the many materials which promote reforming. Among these may be mentioned compounds, such as the oxides or sulfides of metals of the IV, V, VI and VIII groups of the periodic system, especially the oxides of vanadium, molybdenum, chromium, tungsten, cobalt and nickel. These metal compounds may be used alone, in various mixtures or combinations with each other or in combination with car riersor supporting materials such as aluminum oxide, alumina gel, peptized alumina gel, natural clays, activated clays, Super-Filtrol, and the like which may also have some catalytic activity. Particularly suitable catalysts are mixtures of alumina and chromium oxide. alumina and molybdenum oxide, and alumina and vanadium oxide in which the active metal oxide preferably comprises from. 1 to 50% by weight of the mixture. It is frequently advantageous to treat the carrier or supporting material with hydrofluoric or fluosilicic acid prior to incorporation therewith of the active metal oxide. The catalyst may be prepared in ayarie y of diifercnt ways. i. e. by mechanical mixing of the various ingredients. by impregnating the carrier with a solution of the active metal compound and thereafter heating to, convert the metal compound to the oxide, or, if the carrier is alumina, by coprecipitating the aluminum hydroxide and metal hydroxide and then heating to expel apart or all of the water.

The catalyst 2| in reaction zone 20 may comprise any normally solid material which promotes isomerization under the conditions of temperature and pressure maintained in said reaction zone. Among suitable materials for this purpose may be mentioned bauxite, aluminum oxide in its various forms such as alumina gel, hydrated aluminum oxide and peptized alumina gel, silica in various forms such as silica gel, silica-alumina gel, silica-magnesia gel and hydrated silicates of aluminum, heat resistant aluminum halides such as aluminum chloride and aluminum fluoride, zeolites, natural and activated clays and the like. Any or all of these materials maybe preliminarily treated with hydrofluoric or fluosilicic acid to increase their activity.

The catalyst 21 in reaction zone 26 may cornprise any material which promotes polymerization under the conditions of temperature and pressure maintained .in said reaction zone. Among such materials may be mentioned clays such as Attapulgus clay, kieselguhr, diatomaceous earth, Super-Filtrol and the like. Catalysts of the same general type as those 'used in the catalytic reforming step in reaction zone 15 may also frequently be used to advantage in the catalytic polymerization step in reaction zone 26, particularly those. comprising alumina and small amounts, say from 1 to 10% by weight, of oxides or sulfides of metals of the IV, V, VI and VIII groups of the periodic system.

In all of the abovecases the catalyst may be used in different forms, sizes, and shapes. For example, it may be used in a fixed or stationary form or in a suspended or finely divided form. In the drawing it has been shown as used in a stationary form. In this case it is preferably in the form of small lumps, pills, tablets, pellets, granules or other pieces of regular or irregular shape of approximately 10 to 20 mm. in diameter. If used in suspended or finely divided form it would be in the form of small particles of 200-400 mesh size or finer. It will be understood that finely divided catalyst could not be used in the apparatus as shown in the drawing, and that modifications would have to be made.

In the operation of the process, of operation are adjusted so that in a given reaction cycle there is preferably an overall net production of free hydrogen and in any event no overall net consumption of free hydrogen. It is ordinarily possible to run all three treatments under these conditions so that there is no net consumption of free hydrogen in any one of the three. However, the catalytic reforming treatment can be run under conditions to produce hydrogen only so long as the reforming activity of the catalyst is maintained at a certain level. It will be found that the reforming catalyst gradually loses activity because of the deposition thereon of carbonaceous contaminants such as coke. When-the activity of the catalyst has fallen off to such an extent that (1) there ceases to be a net production of free hydrogen or (2) the octane number improvement of the reformed product over the feed is not up to a' predetermined level of which the catalyst is known tobe capable, the flow of naphtha through'the reforming zone l5 should be stopped and the catalyst subjected to a regeneration treatment. Ordinarily the octane number improvement effected by the catalyst will fall below the desired level before there ceases the conditions to be a net production of free hydrogen, and the length of time before this happens may be from 3 to 12 hours or more. At this point the activity of the catalyst can be regenerated by any of several different means. The preferred method is to pass hot inert gases or steam containing regulated quantities of air or oxygen through the catalyst mass in reaction zone l5 whereby the coke and carbonaceous material is burned off and removed as carbon oxides. The passage of hot gases through the catalyst may be continued until there ceases to be a consumption of oxygen from the gases indicating that substantially no more combustible material remains on the catalist. It is frequently advantageous to pass the hot regenerating gases through the catalyst under superatmospheric pressure, say from 20 to 150 pounds per square inch. Under these conditions, the time required for regeneration may be reduced considerably and the volume of the regenerating gases is of course substantially smaller. When fixed or stationary catalyst is used, as in the operation illustrated in the drawing, regeneration may be accomplished in situ. In the case where finely divided catalyst is used, however, it will be understood that regeneration of the catalyst would have to be carried out in a separate chamber and that means would have to be provided for circulating the catalyst through the reaction and regenerating zones. The actual mechanism of the regeneration treatment is substantially the same in both cases.

After regeneration the flow of oil and hydro gen may be resumed and thereafter alternate cycles of reaction and'regeneration may be carried out for an indefinite period or until the catalyst requires replacement. While in the drawing only one reaction zone l5 for catalytic reforming has been-shown, it will be understood that two or more reforming zones may be provided so that while one is on a regeneration cycle, another may be on a reforming cycle. The flow of oil and hydrogen may be switched from one zone to another so that operation may be continuous.

The catalyst in reaction zones 20 and 26 may require regeneration or replacement from time to time, but in general these catalysts can be used for much longer periods before requiring regeneration than the reforming catalyst in reaction zone l5. Regeneration of the catalysts in zones 20 and 26 can be accomplished, when necessary, in the same manner as the regeneration of the catalyst in zone l6, that is by the passage of hot inert gases or steam containing regulated quantities of .oxygen therethrough until the contaminating materials have been burned off. The regeneration of the catalysts in zones 20 and 26 may be carried out in series with the regeneration in zone l5 or separately,

It will have been seen from the foregoing description that theprocess, once it has started up, is substantially self-sustaining with respect to it's requirement ofhydrogen because it is operated under conditions which produce hydrogen. Therefore, it is not necessary to add hydrogen from an extraneous source, but is only necessary to recycle the gases separated from the products of reaction. The concentration of hydrogen in these gases may be regulated and controlled by the scrubbing means 40. For example, if the concentration of hydrogen, i. e. between 30 and 70 mol percent is being well maintained, it is not necessary to pass any of the gases through the scrubbing means. 0n the other hand, if the hydrogen concentration is too low or if it is desired to raise it above the level at which it is, at any given time, being maintained, a suillcient portion of the recycle gases may be passed through the scrubbing means so that the hydrogen concentration in the entire recycle gas stream may be brought up to the desired level. The quantity of scrubbing oil may also be varied to increase the concentration of hydrogen in the recycle gases. When starting up, if an independent supply of hydrogen is not available, the reforming reaction itself may be used to supply it. For example, the reforming reaction may be operated at substantially atmospheric pressure and at a high temperature for a short period. Under these conditions, large quantities of hydrogen are produced although the quality of the hydrocarbon product is not as good as that obtained at higher pressures. This hydrogen gradually builds up until a suilicient supply is available to keep the process going at the desired operating conditions. The pressure is gradually increased until reactionlevel is reached. When shutting down the process for any reason, the supply of recycle gases is retained in storageand this may be used for starting up again.

It will be understood that wherever cooling is necessary in the process, as for instance between the various reaction zones, this may be accomplished by heat exchange between the hot products and the cold entering feed stock or recycle gas. Similarly other variations and expedients may be made use of in accordance with usual procedure.

The product produced by this process is in most cases a finished, stable internal combustion engine fuel and does not require any further treatment except rerunning to a specified end-point, a mild caustic wash to-remove traces of H28, stabilizing or blending. The usual blending agents such as isopentane, iso-octane, alkylated iso-butenes, hydrogenated polymers of butenes may of course be added, as may also anti-knock agents such as tetraethyl lead and iron carbonyl, and, if necessary, gum and oxidation inhibitors.

This invention is not limited by any theories of the mechanism of the reactions nor by any details which have been given merely for purposes of illustration, but is limited only in and by the following claims in which it is intended to claim all novelty inherent in the invention.

We claim:

1. An improved process for preparing an internal combustion engine fuel of high octane number which comprises subjecting a hydrocarbon oil derived from any source and consisting essentially of hydrocarbons boiling substantially in the gasoline range to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050" F., subjecting the products of catalytic reforming to catalytic isomerization in the presencev of hydrogen at a temperature between 700 and 900 F., subjecting the products of catalytic isomerization to catalytic polymerization in the presence of hydrogen at a temperature between 400 and 600 F., recovering from the products of catalytic polymerization a fraction boiling in the range of an internal combustion engine fuel, and a fraction which is uncondensed, and continuously recycling the uncondensed fraction to the catalytic reforming treatment to provide gas rich in free hydrogen required therein and in the two subsequent catalytic treatments.

2. An improved process for preparing an internal combustion engine fuel of high octane number, high stability and low gum content,

which comprises subjecting a hydrocarbon oil derived from any source and consisting essentially of hydrocarbons boiling substantially in the gasoline range to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050" F., subjecting the products of catalytic reforming to catalytic isomerization in the presence of hydrogen at a temperature between 700 of an internal combustion engine fuel, and a ucts of catalytic polymerization a fraction boiling fraction which is uncondensed, and continuously recycling the uncondensed fraction to the catalytic reforming treatment to provide gas rich in free hydrogen required therein and in the two subsequent catalytic treatments.

3. An improved process for preparing an internal combustion engine fuel of high octane number, high stability and low gum content, which com-prises subjecting a hydrocarbon oil derived from any source and consisting essentially of hydrocarbons boiling in the gasoline range to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050 F., subjecting the products of catalytic reforming to eatalytic isomerization in the presence of hydrogen at a temperature between 700 and 900 F., subjecting the products of catalytic isomerization to catalytic polymerization in the presence of hydrogen at a temperature between 400 and 600 F., conducting all three reactions in the presence of between 500and 5000 cubic feet of hydrogen per barrel of oil and under conditions such that there is no overall net consumption of free hydrogen in the entire process, recovering from the prodin the range of an internal combustion engine fuel, and a fraction which is uncondensed, and continuously recycling the uncondensed fraction to the catalytic reforming treatment to provide gas rich in free hydrogen required therein and in the two subsequent catalytic treatments.

4. An improved process for preparing an internal combustion engine fuel of high octane number, high stability and low gum content which comprises subjecting a hydrocarbon oil consisting essentially of hydrocarbons boiling in the gasoline range to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050 F., subjecting a portion of the products of catalytic reforming to catalytic isomerization in the presence of hydrogen at a temperature between 700 and 900 F., combining the remainder of the products of catalytic reforming with the products of catalytic isomerization, subjecting this mixture to catalytic polymerization in the presence of hydrogen at a temperature between 400 and 600 F., and recovering from the products of catalytic polymerization a fraction boiling in the range of an internal combustion engine fuel.

5. An improved process for pr'eparing'an internal combustion engine fuel of high octane number, high stability and low gum content which comprises subjecting a hydrocarbon oil consisting essentially of hydrocarbons boiling in the gasoline range to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050" Fr, subjecting the products of catalytic reto catalytic reforming in the lower boiling fractions with I nets of isomerization to I in the presence of hydrogen, conducting all three catalytic operations under conditions such that 6 forming to catalytic isomerization in the presence of hydrogen at a temperature between 700 and 900 F., subjecting a portion 01' the products of catalytic isomerization to catalytic polymerization in the presence of hydrogen at atemperature between 400 and 600 F., combining the remainder of the products of catalytic isomerization with the products of catalytic polymerization, and recovering from this mixture 9. fraction boiling in the range of an internal combustion engine fuel.

6. Process accordingto claim 4 in which the three reactions are carried out in the presence of between 500 and 5000 cubic feet per barrel of oil of a gas containing between and 90 mol per cent of free hydrogen and under such conditions that there is no overall net consumption of free hydrogen in the entire process.

'7. Process according to claim 5, in which the three reactions are carried out in the presence of between 500 and 5000 cubic feet per barrel of oil of a gas containing between 20 and 90 mol per cent of free hydrogen and under such conditions that there is no overall net consumption of free hydrogen in the entire process.

8. An improved method for preparing an internal combustion engine fuel of high octane number, high stability and low gum content from a petroleum fraction boiling substantially in the gasoline range and rich in lower boiling olefinic hydrocarbons which comprises separating the lower boiling fractions from the higher boiling fractions, subjecting the higher boiling fractions presence of hydrogen, combining said the products of reforming, subjecting the combined mixture to catalytic isomerization in the presence of hydrogen, then subjecting the prodcatalytic polymerization there is no overall net consumption of free hydrogen therein, and recovering a fraction boilin in the range of an internal combustion engine fuel from-the products of catalytic polymeriza-, tion.

9. Process according to claim 8 in which. the petroleum fractionis a cracked naphtha.

10. Process according to claim 8 in which each catalytic treatment is carried out under a pressure between 50 and 500 pounds per square inch. 11; Process according-to claim 8 in which each catalytic treatment is carried out under pressure between 50 and 500 pounds per square inch and in the presence of between 500 and 5000 cubic feet of gas per barrel of oil, said gas containing between 20 and 90 mol percent of free hydrogen.

12. An improved method for preparing an internal combustion engine fuel of high octane number, high stability and low gum content which comprises subjecting a hydrocarbon oil consisting of hydrocarbons substantially boiling in the range between 90 and 500 F. first to catalytic reforming in the presence of hydrogen at a temperature between 850 and 1050 F., next to catalytic isomerizationin the presence'of hydrogen at a temperature between 700 and 900 F. and then to catalytic polymerization in the presence of hydrogen at a temperature between 400 and 600 F., conducting all three treatments under a pressure between 50 and 500 pounds per square inch and in the presence of between 500 and 5000 cubic feet of gas per :barrel of oil, said gas containing between 20 and mol percent of free free hydrogen required therein and in the subsequent two catalytic treatments, and recovering a fraction boiling in the range of the desired internal combustion engine fuel from the condensate.

13. Method according to claim 12 in which the three catalytic treatments are conducted under substantially the same pressure and said pressure is between 50 and 500 pounds per square inch.

14. Method according to claim 12 in which the uncondensed products which are continuously recycled are subjected, prior' to recycling, to a treatment to remove therefrom at least a portion of the hydrocarbon constituents thereof.

15. Method according to claim 12 in which a portion of the uncondensed products which are continuously recycled is subjected, prior to recycling, to a scrubbing treatment with a hydrocarbon oil to remove from said scrubbed portion at least some of the hydrocarbon constituents thereof, and the portion of the uncondensed products so subjected to scrubbing is adjusted so that the concentration of free hydrogen in the entire quantity of rcycled gases is maintained between 20 and 90 mol percent.

16. Method according to claim 12 in which the hydrocarbon oil is passed through each of the three treatments at a feed rate between 0.2 and 50 volumes of liquid oil per volume of catalyst per hour.

1'7. An improved method for preparing an internal combustion engine fuel of high octane number, high stability and low gum content which comprises subjecting a hydrocarbon oil boiling substantially in the gasoline range to catalytic reforming in the presence of hydrogen, separating the product of catalytic reforming into two fractions one comprising the lower boiling hydrocarbons and the other comprising the higher boiling hydrocarbons, subjecting said fraction comprising the lower boiling hydrocarbons to catalytic isomerization in the presence of hydrogen, combining said other fraction comprising the higher boiling hydrocarbons with the product of isomerization, subjecting the combined mixture to catalytic polymerization in the presence of hydrogen, and recovering a fraction boiling in the range of an internal combustion engine fuel from the product of catalytic polymerization.

HERBERT G. M. FISCHER. ROBERT P. RUSSELL.

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