US2347216A - Producing gasolines - Google Patents

Description

Patented Apr. 25, 1944 UNITED STATES PATENT OFFICE.

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No Drawing. Application March 27, 1941, Serial No. 385,465

12 Claims. (01.19am) stocks, for example, by cracking gas oils or other heavy hydrocarbons or by transformation of light or heavy naphthas. It is especially concerned with a catalytic process for improving the characteristics of such gasolines.

High compression spark ignition engines, for example, of the type employed in modern commercial and military aircraft, require fuels meeting exacting specifications, including high anti-knock rating and stability. In preparing such fuels, it has been necessary to build suitable base stocks up to anti-knock specifications by use of addition agents, for example, lead tetraethyl. With many acceptable base stocks, use of maximum permissible quantities of addition agent has not yielded the desired anti-knock rating. Consequently, it has been necessary to include in the base stock substantial quantities of expensive high anti-knock blending agents, for example, aikylation products or hydrogenated polymers, often in quantity exceeding the amount of less expensive portions of the base stock.

The base stocks themselves must meet exacting specifications. They must have the stability required /of the finished product. They must also have reasonably high octane rating. In addition, they must be subject to substantial increase in anti-knock with use of permissible quantities of addition agent, i. e., they must have good response or susceptibility to such agents. Straight-run gasolines of proper end point have been the most commonly used base stocks. Because of the low are incapable of meeting stability specifications of aviation grade fuels. Many of them also fail to have other properties which would make them such decomposition cts to the extent necessary to produce gasolin tion base stocks have failed to yield products capable of competing commercially with straightrun distillates on the basis of quality, that of price, or both.

However, notable exceptions to the general class of gasolines are those produced from selected charging stocks and with the aid of selected composite catalysts obtained or derived from synthetic inorganic gels and the like. Certain processes capable of producing base stocks which satisfy the high stability and other specifications of aviation base stock aredescribed in the following copending applications of John R. Bates: Serial No. 310,762, filed December 23, 1929; Serial No. 365,923, filed November 16, 1940; serial No. 365,924, filed November 16, 1940. The invention, however, is not concerned with treatment of straight-run gasolines to improve substantially their anti-knock ratings, or of other gasolines which, as produced, meet stability and other specifications for base stocks of the type hereinabove described.

One object is to produce stable aviation base stocks and other motor fuels from gasolines produced by decomposition and having unsatisfactory stability. Another object is to provide base stocks superior in quality to straight-run distillates. Another object is to avoid depreciation of anti-knock rating. Another object is to improve susceptibility to addition agents. Another object is to minimize or even to eliminate the use of high anti-knock blending agents in producing aviation gasolines of commercial and fighting grades. Other objects will be apparent from the detailed description that follows.

The invention involves subjecting gasolines of low stability produced by decomposition reactions to the action of silicious splitting catalysts at cracking conditions controlled to efiect' appreciable production 01 gas and coke without afiecting substantially the anti-knock of the, gasoline charge. The surprising and unexpected discovery has been made that gasolines of low stability produced, for example, by cracking or reforming.

reactions, when subjected to cracking in the presence of silicious splitting catalysts are improved in stability to an extent that is dependent upon suitable for such use. Many attempts to refine o the extent of crackins as measured y the proof the duality of aviaduction of gas, coke, or both. By splitting catalysts, reference is made to catalysts which promote decomposition of hydrocarbons predoml nantly by rupture of carbon-to-carbon linkages in contradistinction to dehydrogenation catalysts which act predominantly to increase unsaturation by rupture of carbon-to-hydrogen linkages. In practice of the invention, substantial improvement of stability is ordinarily obtained only when the cracking conditions are sufllciently severe to convert at least 1% by weight of the charge into coke.

It is preferred that the charge be free or substantially so of components above the gasoline boiling range, above about 440 F., because higher boiling hydrocarbons often are subject to complex decomposition processes including those which produce unstable lower boiling materials. However, when the desired stable product is a low boiling distillate, for example, aviation gasoline of 275 to 350 F. end point, higher yields of such products are obtained when the gasoline charge produced by decomposition reactions contains or has added to it a naphtha, preferably produced by decomposition, which is higher boiling than the desired product.

Coke produced accumulates on the catalyst as deposit. The stability of the cracked gasoline falls off substantially when the total quantity of charge fed is such that the accumulated deposit exceeds a low proportionate quantity of the catalyst, usually 50 grams per liter of catalyst. It is preferred to avoid deposits in excess of this amount. For best results, especially when the desired product is aviation base stock, it is preferred to limit the total accumulated deposit til 25 or even grams per liter of catal st.

When the selected quanti y of deposit is reached, the feed to the catalyst is cut oil. The catalyst may then be rejected but preferably is regenerated by combustion at controlled temperature, preferably not in excess of about 1100 F. In commercial practice such regeneration is ordinarily effected at frequent intervals, usually after runs not exceeding a few hours, say 4 to 8 hours, in length, and often after runs of an hour or less, for example, of 10 to 30 minutes duration. Thus, to provide continuous flow through the plant, a plurality of converters of suitable design adapted for use alternately onstream and in regeneration may be employed, the flow being transferred from one converter to another at desired intervals so that there is always at least one converter on-stream while one or more is being subjected to regeneration.

Porous adsorptive contact masses which promote cracking of hydrocarbons higher boiling than gasoline into substantial yields of stable gasoline are employed as catalysts. Satisfactory catalysts include active or activated plural component silicious materials having substantial cracking activity, for example, blends of silica and alumina of suitable activity obtained from natural or synthetic sources.

Because of the wide variation in results that are obtainable from different higher boiling hydrocarbon charging stocks and from different combinations of reaction conditions, cracking activity of a catalyst, as referred to herein and inthe appended claims, is the per cent gasoline obtained by utilization of the catalyst with a selected charging stock under definite cracking conditions. A refractory paraiiinic virgin gas oil having substantially the following properties is utilized as the aforesaid selected charging stock.

A. P. I 36.0:03"

Engler distillation, F.:

Int 440 5%- 464 10% 484 20% 498 30% '510 40% 522 50% 534 60% 550 572 600 -1 646 704 Dry point (96-99%) 724 Sulphur, per cent wt 0.3

Pour, "F 35:5 Flash, F. open cup 220:10 Fire, F 2501-5 S. U. via/100 F 40:3 Conradson carbon 0.03 Aniline point, F.. 16512.5

Several degrees variation in the distillation temperatures throughout the range of the abo've Engler are permissible without any substantial effect upon the yield of gasoline. Gas oils having the requisite properties may be obtained as straight run distillates from East Texas crude or by blending other suitable parafllnic distillates in known manner. For the purposes of this invention, the activity of the catalyst is the per cent. by liquid volume, based on the charge, of 410 F. end point distillate separated from synthetic crude condensed at 60 F. and obtained by passing the vaporized gas oil for a period of 10 minutes at substantially atmospheric pressure and at rate of one and one-half volumes per hour (liquid basis) over one volume of catalyst maintained at 800 F.

In practice of the invention, catalysts of at least 15% activity as above defined should be employed. Better results are obtained with and it is preferred to utilize catalysts of at least 20% activity, for example, those within or above the range of 25 to 40% activity.

Preferred silica-alumina catalysts are blends of silica and alumina in the weight ratio of 3%:1, 4:1 or higher, prepared synthetically or derived from naturally occurring earths. Of particular value are such blends which are free or substantially so of the alkali metals, sodium and potassium. These catalysts not only have the requisite activity but also maintain desired activity for long periods of use involving frequent and repeated regenerations. One method of preparing active and stable synthetic silica-alumina blends is by interreaction of solutions of soluble silicate and of a soluble aluminum compound under controlled pH of 11 or below to produce a zeolitic gel and then to remove the desired amount of alkali metal by base exchange with a solution of a volatile or unstable cation such as ammonium,

with most cracked gasolines, the desired high ly stable product is obtained with temperatures in the range of 100 to 900 F. with a preferred range of 750 to 875 F. Temperatures above about 900 F. tend to cause thermal decompositions which form unstable products and should be avoided. In selecting temperatures within the above ranges, it is best to consider other operating conditions, especially specific catalyst activity. With higher catalyst activity lower temperatures will produce from a given gasoline charge the yield of coke and gas necessary for the dc:- sired extent of refining. Temperatures above that which yields only the necessary quantity of these by-products eil'ects still further improvement in quality of the gasoline, if further improvement is possible, but often at the expense of increased proportionate quantity of coke, gas, or both. Consequently, in the interest of higher yields, it is preferred to employ temperatures which, although high enough to promote cracking to the desired extent, are of such order as to avoid substantial excess of either or both these by-products. Naturally, the particular temperature or range of temperatures best suited for a particular gasoline charge will vary with the ease with which that gasoline can be cracked. Generally, with catalysts of about 25% activity or greater, the desired amount of cracking is obtained at temperature of at least 700 F. but not in excess of 850 F., as within the range of 750 to 840 F. with most gasolines obtained by decomposition reactions.

The conditions of rate and pressure are selected to give contact times in the catalyst chamber sufficiently high to effect cracking of the gasoline charge and sufliciently low to prevent substantial change in octane. Contact times employed are usually at least 15 seconds, based on the volume of the catalyst chamber, and may be as high as 250 seconds as for example, from 20 to 250 seconds. The general trend is for higher contact times within the above range the greater the improvement in stability that is to be effected. with catalysts of at least 20% activity and especially with those of at least 25% activity, many if not most unstable gasolines are converted into products having the high stability necessary for aviation fuels with contact times of 100 seconds or less.

Desired contact time may be obtained simply by regulation of feed rate at substantially atmospheric pressure. However, use of superatmospheric pressure accelerates the desired improvements in the characteristics of the cracked gasoline charge and, in addition, permits use of higher feed rates. Accordingly, it is preferred to utilize superatmospheric pressure, for example, at least 25 lbs. per square inch gauge. Excessive pressures, however, tend to produce excessive coke and gas losses. With most cracked gasolines, pressures within the range of 50 to 200 lbs. per square inch gauge may be employed without incurring excessive gas and coke losses. It is preferable to avoid pressures substantially above about 200 lbs. because at higher pressures the proportionate quantities of these by-products in crease rapidly.

With pressures of 25 lbs. per square inch or greater, the requisite amount of reaction is usually obtained with feed rates of at least 3 volumes of liquid charge per hour to '7 volumes of catalyst. Pressures within the range of the order of 50 to 200 lbs. per square inch gauge ordinarily may be accompanied with feed rates of at least one volume of charge per hour per volume of catalyst,

as for example, within or above to 8 volumes.

Several tests or combination of tests may be utilized as the measure of stability. Exemplary tests include ongen bomb induction periods (A. S. T. M. test D525-40T), Army-Navy accelerated gum determinations (Test F-5d described in U. 8. Government pamphlet AN-VV-F-776) and acid heat (A. S. T. M. test D481-39). Acid heat (equivalents are bromine number determinations such as those utilized by the French and Italian Governments) has been utilized for the purposes of this invention as a convenient test. This test. although it does not measure stability directly, is actually indicative of stability because it is a measure of the quantity of unsaturated and usually olefinic components in the gasoline which are'susceptible to or capable of oxidation to produce undesired gum and color forming bodies. One. convenient measure of the extent of cracking is the per cent of charge that is converted to poke. Coke deposit and desired reduction in acid heat may be correlated to serve as a basis for selecting suitable cracking conditions. Thus, in treating unstable gasolines of aviation boiling range, to produce base stocks for commercial, training, or fighting grades of aviation fuel, it is desired to obtain products having acid heats within or below the range of 60 F. to 15 F. and preferably not in excess of about 40 F. To Produce such stocks from typical but comparatively stable cracked charge having acid heats 40 to 60 F. higher than that desired, coke equivalent the range of 1 to about 1% by weight of the charge should be produced, typical operations yielding up to about 3% by weight of coke. With less stable charging stocks, for example, those whose acid heats are to F. higher than desired, it is ordinarily necessary to obtain coke deposits of at least 2% by weight, as for example, from 2% to 5%. When the desired acid heat reduction is about F. or more, the coke production usually must be about 3.5% or more, for example, 3.5% to 10%. The coke yield necessary to provide determined reduction of acid heat will vary somewhat with the basic chemical composition of the cracked or other decomposition-produced gasoline charged, as governed by the conditions and method employed in its production. Thus, with some decomposition-produced gasolines, for example, highly refractory cracked products, it is desirable to utilize cracking conditions which produce larger quantities of coke than indicated by the lower values of the above ranges. Also. greater quantities of coke are sometimes produced when the charge is a wider boiling range fraction than the desired product, as for example, when the charge is a gasoline of 420 to 440 F. end point and the desired product is of lower end point, for example, aviation gasoline.

Gas produced during the operation may be similarly correlated with stability improvement desired. Ordinarily, the per cent by weight of charge converted to gas will range from about at least 0.5 for acid heat reductions of about 40 to 60 F., to about 10 for acid heat reductions of 200 'F. or more. In most instances, however, coke production provides a better basis for selecting reaction conditions because the quantity of gas is often more subject to substantial variation with minor changes in one or more reaction con- 7 ditions, and especially of temperature.

It is to be understood that the invention is not limited to use of cracking conditions which produce minimum or optimum quantities of byproducts considering the improvement in quantity of gasoline charge that is desired. On the contrary, the highly stable products resulting from practice of the invention are obtained under more severe conditions. ,So long as the conditions of cracking are at least severe enough to provide at least the quantities of cracked by-products necessary to effect the desired degree of improvement in the gasoline charge, highly stable and otherwise improved products are obtained.

As an incident to the cracking reactions, a small portion of the charging stock is usually converted into higher. boiling hydrocarbons of the nature gas oil. These are separated in suitablemanner from the gasoline produced, as by fractionation. Also, if the charge contains organic sulphur compounds, these are decomposed to produce hydrogen sulphide which, in order to yield a finished non-corrosive product, may-be removed by any suitable method, as for example, by fractionation talned at about the same temperature under pressure of the order of 200lbs. per sq. in. gauge and 0.01%, its navy gum about 0.5 milligram, and its color 30. A. P.'I. Under the operating conditions here employed, the contact time was about 96 seconds; The catalytic cracking reaction produced, in addition to the liquid products, about 8.4% by weight of coke and oi. the order of 3.7% by weight of gas. The quantity of coke accumulated on the catalyst was found to be about 10.5 grams per liter. When the same distillate was subiected to another batch of the above catalyst (after regenerasuch as utilized in removing excess light ordinarily v gaseous materials from ,the condensed gasoline to provide a final product of desired vapor pressure. Another method of removing sulphurous material from the products of the catalysis is to contact such products 'preferaly in vapor form and at reduced temperature, for example, within the range of 400 to 650 F. with contact material containing a metal or metal oxide capable of reacting with sulphur bearing components of the vapors to absorb sulphur. Such contact masses may comprise, for example, nickel, cobalt or copper in oxide form deposited or otherwise incorporated in an active or inactive porous support, preferably silicious, and comprising for example silica and alumina. Suitable active supports include active blends of silica and alumina suitable for use as catalysts for the preceding cracking step.

Although production of base stocks for aviation gasolines is an important application of the invention, it is by no means the. only application. On the contrary, the invention finds application in the production of any desired highly stable hydrocarbon fraction which boils within the boiling range of gasoline or the like. Another specific application is in the production of high quality gasolines of the type which commands premium prices on the motor fuel market. For example,

' cracked motor gasoline, which is unsuited for use Example 1 A cracked distillate of aviation boiling range having an acid heat of about 132 F., octane rating of about 79 (CFR-MM) which could be raised to approximately 86 by the addition of 3 cc. per gallon of tetraethyl lead, navy gum of 377 milligrams, A. P. 1. color of 13, and sulphur content of 0.035% by weight, was contacted with an activated hydrosilicate of alumina of about 28% activity composed to the extent of at least 90% by weight of silica and alumina in the weight ratio of' about 4:1. The distillate, after preheating to about 820 E, was fed to the silica-alumina catalyst mintion of the latter by controlled combustion) for a 20 minute run period in which temperature of about 820 F., feed rate of about 2:1, and pressure of about 100 lbs. were employed to give a contact time of the order of 33 seconds, the fractionated products of aviation boiling range had acid heat of about 39 F., navy gum of the order of 11 milligrams, sulphur content of about 0.02%, and cotane rating of about 79 which could be raised to approximately 89 with 3 cc. of tetraethyl lead per gallon. In this operation, the production of gas and coke was about 2.6% and 2.0% respectively and the coke accumulated on the catalyst was of the order of 10 grams per liter.

Example 2 lyst of about 34% activity and similar in composition to that employed in Example 1, at temperature of about 840 F., feed rate of about 1:2, and pressure of the order of 50 lbs. per sq. in. for an operating period of 20 minutes duration. The cracking reaction produced of the order of 8.6% by weight of coke, 8.3% by weight of gas, and a liquid product which upon fractionation yielded a fraction of aviation gasoline boiling range having acid heat of about 20 F. and octane rating of the order of which could be raised to .above 90 by the addition of 8 cc. of tetraethyl lead per gallon, and was otherwise suitable for use as a base stock in the production of commercial or fighting grades of aviation fuel. The reaction conditions employed in this run gave contact time of the order of 75 seconds. Accumulated coke deposit was approximately 10 grams per liter of catalyst.

When another batch of the same charging stock was contacted with the same catalyst in regenerated condition under modified conditions of rate andpressure (rate of 0.75:1 and pressure of 200 lbs. per sq. in.) to give a contact time of the order of seconds for another 20 minute run, an aviation base stock having an acid heat of only 12 F. was produced together with about 10% by weight each of gas and coke, the coke deposit then amounting to about 18.5 grams per liter of catalyst.

, small quantities in conjunction with silica and alumina, either deposited on or otherwise uni-- Ezample 3 A gasoline of aviation boiling range produced by fractionation of a cracked motor iuel of about 390 F. end point and having octane rating of about 79 which could be raised to approximately 90 by the addition of 6 cc. of tetraethyl lead and having an acid heat of about 147 F. when contacted with catalyst similar to that employed in Example 1, at temperature of about 820 F., feed rate of about 0.9 to 1, and pressure of the order of 50 lbs. per sq. in. (these conditions giving contact time of about 42 seconds) yielded about 81% by volume of an aviation gasoline boiling range distillate of about 45 F. acid heat, whose octane of about 79 could be raised to 95 by the addition of 6 cc. per gallon of tetraethyl lead and to above 91 with only half this quantity of addition agent, together with about 3.0% and 5.8% by weight, respectively, of coke and gas. When the entire motor fuel, which contained approximately 20% by volume of components heavier than aviation gasoline, was contacted with the freshly regenerated catalyst under the same operating conditions except a slightly increased rate of about 1:1 (giving contact time of about 38 seconds), fractionation of the liquid products produced aviation gasoline distillate of about 40 F. acid heat and octane rating of about 79 which was raised to about 94.5 by the addition of 6 cc. of tetraethyl lead. This distillate amounted to somewhat more than 89% by volume of the aviation gasoline content of the charge. The coke and gas produced were about 2.6 and 3.4% by weight, respectively. In both the above runs, the accumulated catalyst deposit was approximately 6.5 grams per liter of catalyst.

Example 4 A cracked aviation gasoline having acid heat of about 114 F. and octane rating of the order of 78 (AFB-1C method), which could be raised to about 90 by the addition of 4 cc. of tetraethyl lead, was converted into an aviation base stock having acid heat of about 17 F. and octane rating of about 78, which was raised to about 90 with only 3 cc. of tetraethyl lead per gallon and to 93 upon addition of one more cc. of this material. To effect the conversion, the aviation gasoline charge at temperature of about 790 F., feed rate of the order of 1.5:1 and pressure of about 50 lbs. per sq. in., and an operating period of 10 minutes, was subjected to the action of a catalyst of about 31% activity composed substantially entirely of silica and alumina and Produced by coprecipitation of these materials from a soluble silicate solution and sodium aluminate solution in the presence of ammonium sulphate to form a zeolite from which substantially all alkali metal was removed by base exchange with ammonium chloride solution and by calcination of the resulting purified zeolite. The contact time was about 26 seconds. The coke produced in this operation was about 2.5% by weight of the charge and the gas about 3.1% by weight. The accumulated coke deposit was approximately 4.7 grams per liter of catalyst.

It is to be understood that theinvention is not .formlyincorporated in a suitable synthetic silicaalumina blend or activated hydrosilicate of alumina, or it may replace, in whole or in part,

the alumina content 01' a silica-alumina catalyst.

Suitable diluting agents, for example, steam, may be fed to the catalyst together with the gasoline charge to provide, as desired or necessary, additional control over time of contact. In some instances. small amounts of steam so used may also contribute to the improvement in stability characteristics.

I claim as my invention:

1. In refining fuel of the gasoline type the steps of subjecting gasoline produced by decomposition reactions in the presence of an adsorptive silicious splitting catalyst of at least 20% activity to cracking conditions including temperature within the range of 700 to 900 F. regulated to effect cracking of at least 1% or said charge into coke but only sufllcient to reduce acid heat with-* out aflecting substantially the anti-knock of the charge, and limiting the quantity of charge fed to said catalyst to produce coky deposit thereon not in excess of 50 grams per liter thereof.

2. The process of reducing the acid heat of gasolines produced by decomposition reactions comprising the steps of subjecting such gasolines in the presence of an active silicious cracking catalyst of at least 20% activity to cracking conditions including temperature above 750 F. insufllcient to effect substantial thermal decomposition of said gasoline, regulating said cracking conditions to effect decomposition of at least 1% by weight of said charge into coke but only surficient to reduce acid heat without substantial change in octane rating of said charge, limiting the quantity of gasoline fed to the catalyst to produce coky deposit thereon not in excess of 50 grams per liter thereof, and separating from the products a gasoline having substantially the octane rating or said charge.

3. The process of refining gasolines produced by cracking, reforming, or the like comprising the steps oi. subjecting such gasoline in vapor phase and absence of higher boiling hydrocarbons to cracking at temperatures of at least 750 F. insuiilciently high to effect substantial thermal cracking in the presence of a silicious cracking catalyst of at least 15% activity, regulating said cracking conditions to convert atleast 1% by weight of said charge into coky deposit but only sufilcient to reduce acid heat, limiting the quantity of gasoline fed to said catalyst to produce deposit not in excess of 25 grams per liter of catalyst, and separating hydrocarbons boiling outside the gasoline boiling range from the products of the aforesaid catalysis.

4. The process of improving oxygen stability and other characteristics of gasolines of high octane rating produced by decomposition reaclimited to the use of silica and alumina catalysts tions comprising the step of subjecting such gasoline substantially free of higher boiling hydrocarbons to transformation in the presence of a silicious catalyst of at least 20% activity for promoting transformation of hydrocarbons higher boiling than gasoline into substantial yields of gasoline under such controlled conditions, including cracking temperature of at least 750 F., insufiicient to eflect substantial thermal crackin of said gasoline, and contact time of at least 15 seconds, that at least 1% by weight of the gasoline charge is decomposed to coky deposit to reduce acid heat without substantially affecting the anti-knock rating of said charge, and renewing or regenerating the catalyst before the coky de-- posit thereon reaches 50 grams per liter.

5. In the production of fuels or the gasoline type stable to oxidation, the process oi contacting a gasoline produced by decomposition processes with a silica-alumina cracking catalyst of at least 20% activity under cracking conditions including temperature withinthe range of 100 to 900 F. and contact time in the range of 15 to 250 seconds, limiting said cracking conditions to con- .vert at least 1% by weight oi said gasoline into coke, restricting the quantity of gasoline charge contacted with the catalyst to limit the quantity of colw deposit accumulated on the same to not in excess of 25 grams per liter thereof, and separating a fraction of gasoline boiling range from the resulting products. 1

6. In reducing acid heat of fuels oi the gasoline type, the process of contacting a gasoline produced by cracking, reforming or the like, and having acid heat in excess of 60 F., under cracking conditions including temperature within the range of 700 to 900 F. for 15 to 100 seconds with a silicious splitting catalyst of at least 20% activity, regulating said cracking conditions to effect decomposition oi suillcient quantity of said charge, at least 1% by weight, into coke to reduce the acid heat of the charge at least 40 F., separating a fractionof gasoline boiling range from the resulting products, and limiting the quantity of charge contacted with the catalyst to restrict the coke depomt accumulated on the latter to 25 grams or less per liter thereof.

'7. The process of converting gasolines to reduce their acid heat comprising the steps of subjecting a gasoline produced by decomposition having acid heat of at least 60 F. to the action of a silica-alumina cracking catalyst of at least 25% activity under vapor phase cracking conditions including temperature within the range of 750 to 875 F.,-superatmospherlc pressure below about 200 lbs. per sq. in., and contact time within the range of 20 to 250 seconds, controlling said cracking conditions within the above ranges to effect suillcient decomposition of said charge, at least 1% by weight, into coke to reduce by at least 40 F. the acid heat of that portion of the charge boiling within the boiling range of aviation gasoline, limiting the total quantity of charge contacted with said catalyst during a run to restrict the accumulated coky catalyst deposit to less than 50 grams perliter of catalyst, and separating a gasoline fraction of reduced acid heat from the reaction products.

8. The process ofproducing aviation ba'se stocks from gasolines comprising contacting a gasoline of motor fuel boiling range produced by decomposition reactions and having acid heat in excess of 60 F. with a silicious splitting catalyst of at least 15% activity under cracking conditions including temperature within the range of 700 to 900 F. superatmospheric pressure of at least 25 lbs. per sq. in. and contact time of at least 15 seconds, controlling said cracking conditions to increase the quantity of components within the boiling range of aviation gasoline and to effect suillcient decomposition of said components, at least 1% weight thereof, into coke to eifect reduction of at least 40 F. in the acid heat thereof, restricting the quantity of motor gasoline contacted with assure said catalyst to limit the coky deposit to not more than 25 grams per liter of catalyst, and

separating a fraction-of aviation gasoline boilins range from the resulting reaction products.

9. The process of producing motor fuel oi improved resistance to oxidation from sulphur bearing gasoline containing unstable unsaturated laydrocarbons produced by decomposition reactions comprising subjecting said gasoline to the action of a silicious splitting catalyst of at least 20% activity under cracking conditions including temperature above 750 F. but below thermal decomposition temperature controlled to effect decomposition into coke of at least 1% by weight of said gasoline without affecting substantially its anti-knock rating, removing sulphur bearing components from the products of the cracking step, and regenerating the catalyst before the coky deposit thereon reaches 50 grams per liter.

10. The process of improving resistance to oxidation of high anti-knock gasoline produced .-.by decomposition comprising subjecting such gasoline to the action of a catalyst of at least 25% activity for promoting cracking of hydrocarbons heavier than gasoline into substantial yields of gasoline under such cracking conditions including temperature in the range of 750 F. to 875 F. and contact time in the range of 15 to seconds that at least 1% by weight of the charge is decomposed to coky deposit without aflecting substantially the anti-knock rating of the charge, and limiting the quantity of the latter contacting with the catalyst during a run to produce cow deposit not in excess of 25 grams per liter of catalyst. v

11. The process of refining gasolines produced by cracking, reforming or the like comprising subjecting such gasoline substantially free of higher boiling hydrocarbons to the action of a splitting catalyst for transforming hydrocarbons heavier than gasoline into gasoline and having at least 25% cracking activity, maintained at cracking conditions including temperature of at least 750 F. but insufllcient to effect substantial thermal decomposition of said gasoline, regulating said cracking conditions to establish a contact time of at least 15 seconds under superatmospheric pressure of at least 20 lbs. per square inch so as to effect decomposition of at least 1% by weight of said charge into coke, separating from the products a gasoline fraction of approximately the octane rating of said charge, and renewing or regenerating said catalyst before the coky deposit thereon exceeds 50 grams per liter.

12. The process of producing stocks for aviation gasoline from motor gasolines produced by decomposition comprising subjecting such gasoline substantially free of higher boiling hydrocarbons to cracking conditions in the presence of a splitting catalyst of at least 25% cracking activity under cracking conditions including temperature within the range of 750 to 875 F., superatmospheric pressure of at least 25 pounds per square inch, and contact time of at least 20 seconds, controlled to decompose at least 1% by weight of the gasoline charge into coky deposit, separating a fraction of aviation gasoline boiling range from the converted product, and renewing or regenerating said catalyst before the coky deposit thereon exceeds 25 grams per liter.

ALBERT G. PETERKIN.