US2315506A - Catalytic treatment of petroleum hydrocarbons - Google Patents

Description

April 6, 1943.

GATALYTIC TREATMENT OF PETROLEUM HYDROCARBONS P. S. DANNER ET AL Filed April 27, 1957 Patented Apr. `6, 1943 CATALYTIC' TREATMENT 0F PETROLEUM HYDROCARBONS Philip S. Danner and Calif., assignors to Robert C. Mithoff, Berkeley, Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application April 27, 1937, Serial No. 139,208

' 12 Claims. (Cl. 19652)f The invention relates to catalytic treatment of petroleum hydrocarbons boiling within the range of ordinary gasoline to increase the combustion eiilciency or octane number thereof and to stabilize the hydrocarbons against gum formation or color deterioration.

The invention involves the discovery of catalysts and operating conditions which effect an increase in the octane number of straight run gasolines without material alteration of the boiling point range of the fuel. 'I'he discovery of operating conditions which minimize catalyst poisoning and which increase the life of the catalyst many fold also comprises an important feature of the invention.

Stabilization of gasolines against formation of gums and color bodies without decreasing the octane number of the fuel is regarded as an important feature of the invention.

Accordingly, an object of this invention is to provide a process of catalytically treating petroleum hydrocarbons boiling within the gasoline range to increase the anti-knock value thereof without materially altering the boiling range of the product.

Another object of the invention is to provide a two-stage catalytic process for treating gasolines; the first stage producing hydrocarbons which increase the octane number of the fuel and the second stage stabilizing the converted gasoline against gum formation and color deterioration.

An additional object of the invention is to provide a method of inhibiting catalyst poisoning in a catalytic process for producing hydrocarbons of high octane number from hydrocarbons of lower octane number.

A further object of the invention is to control the production of high octane number hydrocarbons during catalytic treatment of gasoline so that fuels having a constant octane number are produced despite variation in catalyst activity.

To provide a process of inhibiting deposition of Y gums, carbon and the like on the catalyst during vapor phase catalytic treatment of gasoline and to simultaneously avoid interference with formation of hydrocarbons having a high octane number, comprises another object of the invention.

A further object is to provide a two-stage catalytic process utilizing the same type of catalyst first to increase the octane number and then to stabilize the reformed gasoline against gum formation and color deterioration.

The process of this invention should not be confused with other types of processes, such as catalytic cracking, destructive hydrogenation, or

#catalytic desulfurization which require diiferent conditions of operation, involve different chemical reactions, and which produce different results.

Vapor phase catalytic cracking or destructive hydrogenation processes utilize temperatures and/or pressures higher than are suitable for ythe process employed in this invention.

Vapor phase catalytic desulfurization is carried out at temperatures below approximately 750 F. Such temperatures are inoperative for the purpose of producing hydrocarbons having high octane numbers as herein disclosed.

The process of this invention avoids many of the diiiiculties and disadvantages encountered in the practice of prior known processes for reforming gasolines to increase the octane number. For example, non-catalytic thermal reforming processes have the disadvantage of producing hydrocarbons too light or too heavy to be used in gasolines, often to the extent that distillation is necessary to remove low and high boiling products formed by the thermal treatment. The present invention not only avoids this difficulty but also produces a gasoline which has less tendency to form gum or color bodies.

One of the principal difficulties which have been encountered in known catalytic dehydrogenating processes is catalyst poisoning and consequent short catalyst life. By utilizing the particular combination of operating conditions and catalysts of the present invention, poisoning has been inhibited to such an extent that `catalyst life is increased many fold. Dehydrogenating processes have also been carried out at such high temperatures (as, for instance, at 650 C. in Example 3 of French Patent No. 629,838 to I. G. Farbenindustrie), that both accelerated catalyst poisoning and material alteration of the boiling range of the product result.

The preferred embodiment of this invention involves a two-stage process. In order that the chemical changes occurring in each stage may be more clearly understood the conditions of operation of the two stages, together with the chemical changes so far as they are understood resulting therefrom, will. be described separately.

The drawing illustrates a flow sheet of the two-stage process of the present invention.

The rst stage involves the production of hydrocarbons having high octane numbers from hydrocarbons of lower octane number. One of the most critical'featurcs of this first stage of the operation is temperature control. The temperature of the catalyst should be maintained fOr the most part within the range of 850 F. to

950 F. and preferably at approximately 900 F. At the beginning of operations with a fresh catalyst, it is possible to use temperatures as low as 825 F. During the final portion of an operation with a catalyst which has become sluggish, the temperature can be raised to an upper maximum of 1025 F. By controlling temperature in this manner and by coordinating temperature with catalyst activity (that is, increasing temperature as catalyst activity decreases) soi that the ratio Aof volume of fixed gases formed to amount of hydrocarbons treated is maintained approximately constant, a treated gasoline having the same octane number at the beginning and end of an operating cycle, is obtained. At temperatures below 825 F. the catalysts are not suf- .ciently active to increase the octane number of the vapors to any substantial extent. Temperatures above 950 F. produce accelerated catalyst poisoning and short catalyst life. 'I'he temperature range specified is therefore of critical importance.

Catalysts found to be active and best suited for the above first stage of operation are bauxite, precipitated alumina, zinc oxide, stannic oxide,

l zirconium oxide and thorium oxide.

It has been discovered that introduction of steam along with the hydrocarbon vapors.` very greatly increases the active life of the :above catalysts without interfering with the formation of hydrocarbons having high octane number. For example, when one to two molecules of 'water vapor is introduced for each ten molecules `of hydrocarbon vapor (using the average molecular weight of the hydrocarbons in the vapors being treated as the basis for calculation) the catalyst life was increased in some cases as much as tenfold over that obtained under the same operating conditions without the introduction of steam. Although it has been found that water vapor inhibits catalyst poisoning without interfering with formation of hydrocarbons of high octane number, the chemical mechanism of this action has not been established. So far as known to applicants the selective action of water vapor on catalyst poisons rather than on the hydrocarbons of high octane number which are being formed has no adequate theoretical explanation. Having once discovered this empirical and unpredictable result, the partial pressure or proportion of water vapor can be adjusted by simple tests to obtain maximum catalyst life and minimum interference with formation of the desired hydrocarbons of high octane number. The proportions previously indicated have been found satisfactory. These proportions may of course vary with the stock being treated, the catalyst used and the conditions of operation.

The use of pressure is unnecessary in the operation of the above process. Within the broad aspects of the invention, however, pressures up to approximately 500 pounds per square inch may be utilized. The use of superatmospheric pressure possesses some advantage in the separation of fixed gases from the condensed vapors, in scrubbing the dissolved hydrogen sulfide from the condensate, and in increasing the capacity of the catalyst chamber. Insofar as the essential feature of increasing the octane number of the treated vapors is concerned, atmospheric pressures are preferred.

The following specific example is given to illustrate the effects of treatment at temperatures of 82,5 to 1025 F. according to this invention.

A California straight-run gasoline distillate was vaporized and the vapors passed at atmospheric pressure through a bed or body of bauxite held at 918 F. The hydrocarbons were fed through the catalyst at a rate of 1 gallon of liquid fuel charged per 1.4 cubic foot of catalyst space per hour. The following tabulation shows the chemical changes and the improvement in octane number resulting from this treatment.

gas were produced per gallon of gasoline charged. This gas contained about hydrogen at the beginning of the run, but the hydrogen content dropped to about 50% after 80 to 100 hours of operation without catalyst revivication.

The second stage of the processconsists in passing gasoline from the rst sta'ge of treatment, with or without the gases formed therein, in vapor phase over a stabilizingcatalyst. Temperature is of critical importance in this second stage of operation. From the standpoint of stability of the product against gum formation the temperature should be between approximately 570 F. and 660 F.; however, temperature as low as 525 F. and as high as 800 F. are operative to increase the stability of the fuel and may be utilized. Feed rates of 50 to 100 gallons of liquid fuel per hour per ton of catalyst produce satisfactory results.

Catalysts found to be active for stabilizing the treated gasoline are tungsten oxide, alumina, bauxite and Florida clay. The preferred catalysts are either alumina or bauxite, since these materials are among the more active and satisfactory ones used to produce hydrocarbons of o high octane number in the first stage of the process. One important discovery which this invention utilizes is that when these catalysts have become sluggish as stabilizing catalysts in the lsecond stage of the process, they are still active to produce hydrocarbons of high octane number when utilized in the first stage of treatment. By adopting the procedure of using the catalyst first to stabilize the fuel and then to catalytically convert low octane number hydrocarbons to high octane number hydrocarbons a single body of catalyst is used twice, that is, in both the vfirst and second stage of operation without an intervening regeneration step being necessary.

The exact chemical nature of the phenomenon which occurs during the stabilization step has not been established. We have observed that there is a reduction of 10% or more in the amount of unsaturated compounds present in the fuel and a corresponding increase in the amount of more stable hydrocarbons, principally aromatics and' naphthenes. There also appears to be a change in the form of the remaining unsaturates as indicated by their increased stability against gum formation and against polymerization when the fuel is treated with sulphuric acid. I

The following analysis shows changes which occur during the present process. These analyses were made on the same fuel, first before tralmcnt, then after treatment according to Aiwr ist Untrcaicd Agt'gt and '.d

` stage OctaneNo 56 (i7 Unsaturatas". pirccnt 18. il 7. 2 Aromatics .lo 7.0 15.2 Naphthcuos do... 48 47.1 Paraiiins .dom. 26.2l 30.5 Miligrams oi gum per 100 cc.

ill 31H (i2 A. I. I. gravity l 50.8 40.0

These data indicate that unsaturates are converted to aromatics as shown by the decrease from 18.8% to 7.2% of unsaturates and theinf crease from 7% to 15.2% of aromatics.

A gasoline which gums or discolors readily is rendered completely color-stable and gum stable by the above described stabilization treatment. Further refinement is not necessary for most purposes since the product is water-white and completely satisfactory. This feature is illustrated by the data from gum stability tests recorded in the above table. Before stabilization the fuel formed 331 mgs. of gum and after stabilization only 62 mgs. of gum, in a standardized test.

When specifications as to extremely low sulfur content must be met it is sometimes necessary to subject the fuel to further refining treatments, as for instance, treatment with sulphuric acid.

'I'he stabilization treatment produces a gasoline which requires less sulphuric acid for a given degree of refinement than is required by straight cracked or reformed gasolines. Naphtha stabilized according to the present process and treated with a given amount of sulfuric acid, yields a treated naphtha of higher gasoline content than do cracked or reformed naphthas. 'Ihese facts are illustrated by the data from treatment of a crude vapor phase naphtha which had been passed over bauxite at 570 F.

Original Processed naphtha naphtha Unsaturation 7i'- 69 louncls of cold lili llo. l|'-S() por gallon of naphtha required io prorluw gasoline of (M50/i, sulfur contont 0.75 0.5 Overall gasoline yclii. 711. 80. ii

The increase-in the stability against polymerization of the unsaturates remaining in the fuel is illustrated by the following data: An unprocessed naphtha was treated with 0.5 lb. of 66 B. sulphuric acid per gallon of fuel. This treatment caused a polymerization loss of 8.3%. Another portion of this same fuel was stabilized by treatment at 660 F. according to the present invention and then treated with the same amount of sulphuric acid underthe same conditions. The polymerization loss was reduced to 1.3%. This represents a decrease of approximately 85% in the amount of polymerization.

It should be noted that the second stage of the process of this invention effects stabilization of the high octane hydrocarbons without substantially reducing the octane number of the fuel. It has been found that the stabilization treatment may either increase or decrease the octane. number of the fuel to a minor extent,'depending upon the conditions of treatment and the characteristics of the distillate being treated. To

illustrate these factors the following specific examples are given: A crude California natural gasoline having an octane number of 56 was run through the rt stage of treatment and its octane number increased to '70. This product was then separated into two fractions by distillation. The most volatile fraction, the first ,over, was passed over 1700 cc. of bauxite at 570 F. at the rate of 400 cc. of liquid fuel per hour. The octane number of this stabilized fraction was 67. The less volatile 50% of the original gasoline was stabilized in exactly the same manner. The octane number of the second fraction was 71. It is thus seenthat the octane number of the more volatile fraction was decreased somewhat and that of the less volatile fraction increased. The net change on the entire fuel is therefore relatively small. To further exemplify the utility of this invention tetraethyl lead fluid as sold onl the market was added to a gasoline which had been .treated by the two-stage process herein described The increase in octane number resulting from the addition of various amounts of thetetraethyl lead is shown in the following table:

l Octane No. Original fuel-. 67 Original fuel 2 cc. per gal. tetraethyl lead fluid g 75 Original fuel 4 cc. per gal. tetraethyl lead fluid '77 Original fuel 6 cc. per gal, tetraethyl lead uirl '79 Original fuel 8 cc. per gal. tetraethyl lead fluid Original fuel -i- 10 cc. per gal. tetraethyl lead fluid 82 In regard to the catalyst used in the process of this invention, it is noted that even though catalyst life has been increased many times, the catalytic materials do eventually become poisoned with carbon, gums and the like. The catalyst must be regenerated after long periods of opbons and intermittently regenerating the catalystv is to provide a series of separate catalyst chambers connected by valve controlled conduits so that the chambers can be used in rotation. For example, when three chambers are provided there will be the following periods of operation involved in a complete cycle:

lst periml-Fntalyst chamber #l at S25-800 ll'.

Catalyst chamber #2 at 825-1025" F. Catalyst chamber #3 catalyst revivifcniion. 2nd period-Catalyst chamber #3 at E25-800 1".

Catalyst chamber it] at S25-1025* l. Catalyst chamber #2 natal si: revivil'caiion. 311i polimi-Catalyst chamber #2 at 52. M800 F.

("ntnlyst chamber :d3 at 825-1025 F. Catalyst chamber #l catalyst reviviflnatinn. 4thperiod-Sunmlas lst period and begins repetition oi' (gwl.

From the above tabulation it is evident that a particular body of catalyst passes through a cycle involving, first, use in the second stage of -the process at temperatures of 570-660 F. to stabilize the hydrocarbon vapors and, second, use in the rst stage of the process at temperatures of from 825-1025 F. to convert incoming low octane numer hydrocarbons to high octane number hydrocarbons.

Another method of providing a continuous process is to supply active catalyst to one end of a catalyst chamber while removing exhausted or inactive catalyst from the other end. In this latter instance the temperature of the catalyst at the end where the fresh catalyst is introduced will be maintained at 525 to 800 F. and the temperature at the opposite end of the catalyst chamber maintained at from 825 to 1025 F. The hydrocarbons to be treated ow in at the high temperature end, through the chamber and out, at the low temperature end. The temperature; gradient may be maintained and controlled by suitable heating and cooling coils or by introduction of live steam into the vapors at points intermediate the ends of the catalyst chamber. .A1- though the two-stage process can be carried lout in a single catalyst chamber, as described, we prefer to keep thc two stages of operation separate and effect each stage of treatment in a separate chamber. The latter method is more exlble and casier to control. Low pressure steam provides an effective cooling medium since its temperature may be as low as 212 F. y

The process steps of the preferred specific embodiment of the invention as hereinabove described may be summarized as follows:

(a) Vaporizing petroleum hydrocarbons of substantially gasoline boiling point range;

(bl Passing the vapors, together with Water u vapor, at a moderate rate over bauxite at ternperatures between 850 F. and 950 F. for vthe major portion of a catalyst operating period;

(c) Controlling the temperature of the catalyst so that the ratio of fixed gases to vapors treated is maintained approximately constant;

(d) Passing the hydrocarbon vapors over bauxite at temperatures from 570 to 660 F.;

(e) Condensing the vapors of substantially gasoline boiling point range;

if) Separating xed gases from the condensed vapors;

(y) Utilizing the catalyst which `has become sluggish at 570 to 660 F. for the treatment at 850 to 950 F.;

(h) Regenerating the catalyst by blowing with ail` or air and steam.

As previously indicated a number of catalysts are operative in the process of this invention. In order to compare the relative efficiency of catalysts and their activity in converting low octane number hydrocarbons to high octane number hydrocarbons, straight run gasoline was passed through various catalyst bodies at the rate of one gallon per hour per .07 cubic feet (2000 cubic centimeters) of catalyst. The temperature of treatment was maintained at 900 F. and the catalyst activity compared by measuring the volume of fixed gases produced. Fresh artificial alumina appeared to be the most highly active of all of the catalysts tried. Bauxite was only slightly less active initially but showed greater resistance to poisoning after continued use. Starmic oxide, zinc oxide (dry process), zirconium oxide, thorium oxide, and alkalinized zinc oxide are all sat isfactory active catalysts, but are not as active as the aluminum oxide catalysts.

Catalysts found to be less active than the above are molybdic oxide, manganese dioxide, zinc chromite, a mixture of aluminum, chromium and molybdenum oxides, precipitated zinc oxide, and precipitated alumina which had been heated to 1600 F.

Various methodsof preparing the above catalysts are within the skill of the art. The following illustrations are given to exemplify one method which has been found to be satisfactory.

Bauxite was ground and screened to 30-60 mesh.

Aluminum hydroxide was precipitated from aluminum chloride solution with ammonia, washed, dried, and groundeto 30-60 mesh to give artiiicial alumina.

Commercial zinc oxide powder produced by calcining or burnlng,.was wet with a 5% solution of agar-agar, dried, and ground to 30-60 mesh. This catalyst is designated in the presentspecication as "Dry process zinc oxide."

Basic zinc carbonate was precipitated from zinc sulfate solution with sodium carbonate, filtered, Washed, and dried. This precipitate was then moistened with enough potassium carbonate solution to give 1% as much KzO as ZnO, dried, and ground to 30-60 mesh. This product is termed alkalinized Zinc oxide in the present application.

Sponge tin was heated with excess concentrated nitric acid to form insoluble stannic oxide. The mixture was dried and screened to 30-60 mesh.

Zirconium oxidewas prepared by sintering a commercial zirconium oxide powder with agaragar and grinding to 30-60 mesh as in the case of dry process zinc oxide.

Thorium carbonate was precipitated from thorium nitrate solution with sodium carbonate, l- Itered, washed, dried, heated to transform it to the oxide, and ground to 30-60`mesh.

As previously noted the above methods of catalyst preparation are merely to be regarded as one illustrationof the many suitable methods which may be adopted. i

Reference has been made throughout the present specification to regeneration of the catalyst.

When the catalyst becomes poisoned after long continuous use, it may be regenerated without removal from the catalyst chamber, by burning with air. The hydrocarbon vapors are first swept from the catalyst chamber with steam, then air or a mixture of steam and air is admitted to the catalyst chamber until the combustion of the poisoning deposits is complete. Precautions should be taken to maintain the air flow rate below that which causes local overheating with consequent damage to both apparatus and catalyst` Regeneration by this method renews activity to substantially that of a fresh catalyst.

Our process nds its greatest utility in the treatment of straight-run gasolines having a boiling range of from 200 to 400 F. and more particularly to such straight-run gasolines containing 20% or more naphthenic hydrocarbons. It is particularly effective for the treatment of California or Mid-Continent straight-run gasolines and for treatment of aluminum chloride gasolines produced by processes such as in U. S. Patents Nos. 1,193,540 and 1,127,465. The process is also applicable to parailnic gasolines and can be applied with less advantage to cracked gasolines.

Gasoline treated by the process of this invention shows greater susceptibility to increase in octance number by addition of lead tetraethyl than the same gasoline treated to give the same octane value by non-catalytic thermal reforming processes. This may be due to the fact that as much as of the sulfur is removed by our catalytic treatment at the same time reforming of the hydrocarbons is occurring. Gasoline treated by non-catalytic reforming processes is also generally less desirable as to color, odor and stability than is gasoline from our particular catalytic treatment.

The provision of suitable apparatus for carrying out ourvprocess is regarded as withinthe skill of the petroleum technician. Common the group consisting of bauxite, precipitated alumina, zinc oxide. stannic oxide, zirconium oxide and thorium oxide, whereby the antiknock value of said fuel is catalytically increased without material alteration of the boiling range thereof; and then stabilizing said fuel against forms of catalyst chambers, support for catalyst beds, heating and cooling means to control the temperature of the catalyst `bed and the' temperature of the petroleum vapors, may be utilized. The apparatus disclosed in the patent to Harrison et al. 2,031,600 comprises an example of a known form of apparatus suitable for carrying out the process of this invention.

The scope of this invention is not limited to the specific examples herein disclosed but comprehends variations and equivalents included within the spirit and terms of the appended claims.

We claim:

l. A process of catalytically treating and stabilizing a hydrocarbon fuel boiling within the range of gasoline which comprises: dehydrogenating hydrocarbons of low octane number, without cracking said fuel sufficiently to substantially alter the boiling range thereof, by passing said fuel in vapor phase at temperatures of from approximately 825 F. to 1025 -F. and in the absence of substantial quantities of added hydrogen over a metal oxide catalyst capable of catalyzing dehydrogenation reactions without concurrently producing substantial cracking, whereby the anti-knock value of said fuel is catalytically increased without material alteration of the boiling range thereof; and then stabilizing said fuel against gum formation, without substantial adverse effect upon the octane number thereof, by passing said fuel vapors over a metal oxide catalyst selected from the group consisting of tungsten oxide, alumina and bauxite at a temperature of from approximately 525 F. to 800 F.

2. A process of treating petroleum hydrocarbon fuels having a boiling range of from approximately 200 F. to 400 F. which comprises: dehydrogenating hydrocarbons of low octane number, without cracking said fuel sufficiently to substantially alter the boiling range thereof, by passing said hydrocarbons in vapor phase in the absence of substantial quantities of added hydrogen over` a metal oxide catalyst capable of catalyzing dehydrogenation reactions without concurrently producing substantial cracking; maintaining said fuel vapors and catalyst at from approximately 825 F. to 1025 F. whereby said fuel is dehydrogenated without substantial alteration of the boiling range thereof; and then stabilizing said fuel against gum formation, without substantial adverse effect upon the octane number thereof, by passing said fuel vapors over a metal oxide catalyst selected from the group consisting of tungsten oxide, alumina and bauxite at a. temperature of from approximately 525 F. to 800 F.

3. A process of catalytically treating and stabilizing a hydrocarbon fuel boiling within the range of gasoline which comprises; reforming hydrocarbons of low octane number, without cracking said fuel sufficiently to substantially alter the boiling range thereof, by passing said fuel in vapor phase at temperatures of from approximately 825 F. to 1025 F. and in. the absence of substantial quantities of added hydrogen over a metal oxide catalyst selected from gum formation, without substantial adverse effect upon theoctane number thereof. by passing said fuel vapors over a metal oxide catalyst selected from-'the group consisting of tungsten oxide, alumina, and bauxite at a temperature of from approximately 525 to 800 F.

4. A` process of catalytically treating and stabilizing ahydrocarbon fuel boiling within the range of gasoline which comprises: dehydrogenating hydrocarbons o f low octane number, without cracking said fuel sufficiently to substantially alter the boiling range thereof, by passing said fuel in vapor phase at temperatures of from approximately 825 F. to 1'025 F. and in the absence of substantial quantities of added hydrogen over an aluminum oxide catalyst capable of catalyzing dehydrogenation reactions without concurrently producing `substantial cracking, .whereby the anti-knock value of said fuel is catalytically increased without material alteration of the boiling range thereof; and then stabilizing said fuel Vagainst gum formation, without substantial adverse effect upon the octane number thereof, by passing said fuel vapors over an aluminum oxide catalyst at a temperature of from approximately ozb F. to uu F.

5. A process of catalytically treating and stabilizing a hydrocarbon fuel boiling witnm the range of gasoline which comprises: rdehydrogenating hydrocarbons ol' low octane number, witnout cracking said I'uel sufficiently to substantially alter the boiling range thereof, by passing said fuel in vapor phase at temperatures of from approximately 825 F. to 1025 F. and in the aosence of substantially quantities of added hydrogen over a bauxite catalyst capable of catalyzing dehydrogenation reactions without concurrently producing substantial cracking, whereby the antiknock value of said fuel is catalytically increased without material alteration of the boiling range thereof; and then stabilizing said fuel against gum formation, without substantial adverse effect upon the octane number thereof, by passing said fuel vapors over a bauxite catalyst at a temperature of from approximately 525 F. to 800 F.

o'. A process of catalytically treating and stabilizing a hydrocarbon fuel boiling within the range of gasoline which comprises: dehydrogenating hydrocarbons of low octane number, without cracking said fuel sufficiently to substantially l alter the boiling range thereof, by passing said fuel in vapor phase at temperatures of from approximately 825 F. to 1025u F. and in the absence of substantial quantities of added hydrogen over an aluminum oxide catalyst capable of catalyzing dehydrogenation reactions without concurrently producing substantial cracking, whereby the anti-knock value of said fuel is catalytically increased without material alteration of the boiling range thereof; then stabilizing said fuel against gum formation, without substantial adverse effect upon the octane number thereof, by passing said fuel vapors over an aluminum oxide catalyst at a temperature of from approximately 525 F. to 800 F.; and, when the catalyst in said stabilizing treatment at 525 F. to 800 F. has become substantially inactive at this temperature, utilizing said aluminum oxide to catalytically instabilizing hydrocarbon fuels boilingY within the range of gasoline. comprising vaporizing said fuel, catalytically increasingthe anti-knock value of said fuel, without substantial alteration of the boiling range thereof, by passing said fuel vapors over a catalyst capable of catalyzing dehydrogenation reactions without concurrently producingsubstantial cracking, whereby the anti-lfnckv value of said fuel is catalytically increasedy without material alteration of the boiling range: the steps of maintaining said catalyst at a temperature of from approximately 850 F. to 950 F. for a major portion of the duration of said catalytic treatments and stabilizing said fuel against gum formation, without material reduction of the octane number thereof, by passing said fuel vapors after said catalytic treatment over bauxite at a tzxlperature f from approximately 525 F. to 8 F.

11. A process of treating petroleum hydrocarbon fuels boiling within the range of gasoline which comprises: catalyzing conversion of hydrocarbons of low octane number to hydrocarbons of high octane number, Without producing sufficient cracking of said fuel to substantially alter the boiling range thereof, by passing said hydrocarbons in vapor phase over a metal oxide catalyst capable of catalyzing dehydrogenation reac-1 tions without concurrently producing substantial cracking, whereby the anti-knock value of'said fuel is catalytically increased without material alteration of the boiling range; maintaining said fuel vapors and catalyst at from approximately 825 F. to l025 F. during said catalytic treatment; inhibiting poison of the catalyst, without substantially interfering with said conversion, by contacting said catalyst simultaneously with steam and with said hydrocarbon vapors; and then stabilizing said fuel against gum formation,

AWithout substantial reduction of the octane number thereof. by passing said vapors over a metal oxide catalyst selected from the group consisting of tungsten oxide, alumina and bauxite at a temperature of from approximately 525 F. to 800 F.

l2. In a process of treating petroleum hydrocarbon fuels boiling within the range of gasoline which comprises catalytically increasing the antiknock value of said fuels, Without substantial alteration of the boiling range thereof, by passing said hydrocarbons in vapor phase over a metal oxide catalyst capable of catalyzing dehydrogenation reactions without concurrently producing substantial cracking, whereby the anti-knock value of said fuel is catalytically increased witnout material alteration of the boiling range: the steps of maintaining said catalyst at a temperature of from approximately 850 F. to 950 F. for a major portion of the duration of said catalytic treatment and then correlating temperature with catalyst activity by increasing the catalyst temperature from 850 F. to no more than approximately 1025 F. at a rate suliicient to maintain the ratio of fixed gases formed to amount of fuel treated substantially constant throughout an operating cycle.

PHHJP S. BANNER. ROBERT C. MITI-IOFF.

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