US2960459A - Hydrocracking of hydrocarbon oils with spent cracking catalyst containing ferric oxide - Google Patents

Description

HYDROCRACKING F HYDROCARBON OILS WITH SPENT CRACKING CATALYST CON- TAINING FERRIC OXIDE Henry E. Reif, Drexel Hill, and Herbert L. Johnson,

Media, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed Dec. 8, 1958, Ser. No. 778,573

1 Claim. (Cl. 208-110) This invention relates to a catalytic composition effective in catalytic processes for converting hydrocarbons. More particularly, the invention relates to a new and improved inexpensive catalytic composition, its preparation, and to processes for using the new catalyst such as processes for removing non-hydrocarbons from mixtures thereof with hydrocarbons and for converting heavy hydrocarbons to relatively loW boiling hydrocarbons.

Heavy hydrocarbon materials such as residues from petroleum cracking operations, reduced heavy crude oil, still tars, and the like, are of little value. Processes for converting such materials to more valuable lower boiling products have been described. Such processes generally involve contacting hydrocarbon material with hydrogen and a cracking or hydrogenation catalyst at high temperature and high pressure, the pressure usually being of a magnitude of about 3000 p.s.i.g. or higher. These processes generally require special, expensive catalysts, and suffer from one or more other drawbacks, such as poor yields of the desired distillate liquid products, excessive coke formation resulting in plugged equipment and other difliculties, and high yields of dry gas.

An especially serious drawback of processes heretofore used is the degradation of the relatively high boiling products of the process so that they are unsuitable, or at least less suitable, for use in recycling to the process. By degradation is meant the conversion of a portion of the relatively high boiling materials of the charge stock to other relatively high boiling materials which, when again used in the process such as by recycling, are converted to coke. Degradation also includes concentrating such high boiling materials which are converted to coke on reuse, in the recycle fraction. The Ramsbottom carbon residue method (ASTM D524- 42) of evaluating the coke forming tendencies of both the charge stock and recycle stock of the process provides a measure of the degradation of the relatively high boiling materials. Thus, when the Ramsbottom carbon residue of the recycle stock from the process is greater than the Ramsbottom carbon residue of the charge stock, the recycle stock has been degraded and its reuse in the process results in the formation of relatively large quantities of coke. Conversely, when the Ramsbottom carbon residue of the recycle stock is less than the Ramsbottom carbon residue of the charge stock, the materials of the recycle stock have been upgraded and their reuse in the process results in a decrease in coke formation. Upgrading the recycle stock permits recycling to substantial extinction to form relatively low boiling hydrocarbons as the sole products of the process.

An object of the present invention is to provide new and improved inexpensive catalytic composition effective for converting hydrocarbons. A further object is to provide a process for preparing the new catalytic composition of the invention. Another object is to provide a process for converting heavy hydrocarbon materials to relatively low boiling hydrocarbon products. A particular object is to provide a hydrocracking process for we 2,960,459 Ice Patented Nov. 15, 1960 converting residual oils to distillate products in good yields,'using an inexpensive catalyst, in which only negligible quantities of coke and dry gas are formed and in which the relatively high boiling products are especially suitable for reuse in the process as recycle. stock. Other objects and their attainment in accordance with the invention will be apparent from the following specification.

GENERAL A new catalytic composition has been discovered which gives improved results in converting hydrocarbons. The new catalytic composition comprises a spent cracking catalyst having deposited thereon as an essential ingredient a minor quantity of iron oxide.

By the expression spent cracking catalyst, as used herein, is meant those catalysts which are effective for cracking hydrocarbons, especially hydrocarbons boiling above the gasoline range, and which by virtue of use in a hydrocarbon cracking operation exhibit a decreased activity toward such cracking, such decreased activity being a reduction of about 30% to 50%, after removal of coke, below the initial activity. The decrease in activity is caused at least in part by the deposition of foreign materials on the catalyst which are not removed in the usual regenerative processes for reactivating cracking catalysts. Catalytic activity, as used herein, is a measure of the efiicacy of a catalyst for cracking hydrocarbons, and is determined by a method described by Alexander, Proceedings Am. Pet. Inst. 27 (III) 51 (Nov. 1947). United States Patent No. 2,635,081 describes and claims an improved hydrogenation catalyst consisting essentially of a spent cracking catalyst, substantially as above described, having deposited thereon from 10% to 25% molybdenum sulfide.

The reactions involved in the preferred process employing the novel catalysts of the invention are primarily the cracking of the relatively high boiling hydrocarbon materials to lower boiling hydrocarbon materials and the hydrogenation of unsaturated hydrocarbons to saturated hydrocarbons. The overall process, therefore, can conveniently be designated as hydrocracking. Reaction variables used in the hydrocracking process are described hereinafter.

THE CATALYST The new catalytic composition of the invention may be prepared by a variety of means, the general techniques of which are known in the art. It is of primary importance that the limits on the ranges of components present in the catalytic composition be observed as hereinafter discussed.

As above stated, the catalytic composition in the present invention comprises a spent cracking catalyst and iron oxide. Ferric oxide (Fe O is the principal oxide of iron present although it is realized that oxides wherein the iron has a different valence state may be present. The calculations for iron oxide presented herein are based on ferric oxide (Fe O Spent cracking catalysts which can be employed in the catalytic composition of the invention are those which have been employed for the cracking of hydrocarbons until the cracking activity thereof has decreased to an extent of at least 30% of its initial activity.

As illustrative of cracking catalysts which become deactivated in cracking processes to form a spent catalyst which may be employed to prepare the catalyst of the present invention may be mentioned synthetic catalysts containing silica, such as silica-alumina, silica-magnesia, and silica zirconia compositions; and natural minerals such as clays, zeolites, feldspar and bauxite which may be specially treated prior to use in cracking such as by leaching with mineral acids. In accordance with the present invention, it is preferred to employ a cracking catalyst of siliceous nature, and more preferably to employ a synthetic catalyst composed of silica and alumina, which has become spent in a catalytic cracking operation and for simplicity the present invention is described with reference to this spent cracking catalyst, it being understood that other spent cracking catalysts may be employed and good results obtained therewith.

The use of silica-alumina catalysts for the cracking of hydrocarbons is well-known. Such catalysts generally contain a ratio of silica to alumina of 1:1 to 15:1, and preferably from 70% to 80% silica, from 20% to alumina, and not more than 10% of other metallic oxides. It is also essential that water be present preferably in a quantity of about 2%. Good results are obtained in cracking where the catalyst is prepared by impregnating silica with alumina salts, by directly combining precipitated hydrated alumina and silica, or by joint precipitation of alumina and silica from aqueous solutions of their salts, and by washing, drying, and heating the so-obtained compositions to approximately 1000 F.

In cracking operations, which are commonly conducted at temperatures of from about 750 F. to 950 F. and pressures of from about 25 p.s.i.g. (pounds per square inch gauge) to 200 p.s.i.g., the catalytic activity of the catalyst progressively decreases due to the accumulation of coke and other foreign materials thereon until its use in the operation is no longer feasible. Such spent catalysts may be regenerated by burning off the deposited coke by heating to a temperature usually less than about 1100 to 1200 F. in a stream of air which may be diluted with an inert gas in order to control the rate of burning. Regenerative processes, however, do not completely restore to the catalyst its initial activity, and regeneration becomes progressively less effective. This effect is due at least in part to the deposition of foreign materials on the catalyst which are not removed in the regeneration process. When the cracking activity, after regeneration, of a catalyst has decreased to from about 70% to 50% of its initial activity, regeneration thereof is no longer feasible and the catalyst is discarded.

The quantity of ferric oxide deposited on the spent cracking catalyst must be within the range of from 0.5 to 10% by Weight. At quantities below 0.5%, a substantial conversion of heavy hydrocarbon materials to lighter boiling materials requires relatively high temperatures and results in excessive coke formation and in the degradation of the recycle stock of the process. At concentrations above 10% by weight, prohibitively high yields of dry gas and undesired product are obtained from the process.

To illustrate a specific catalytic composition in accordance with the invention, a spent synthetic silica-alumina .cracking catalyst having deposited thereon 7.0% by weight Fe O gives good results.

PREPARATION OF CATALYST The catalytic composition of the present invention is advantageously prepared by impregnating a spent cracking catalyst with an aqueous solution of a water soluble iron compound such as ferrous sulfate. A quantity of a base such as sodium hydroxide is then advantageously added to precipitate iron hydroxide. The resulting impregnated composition is then washed, dried and heated in contact with air to convert the iron to ferric oxide.

The concentration of the water soluble iron compound in the impregnating solution and the quantity thereof used should be sufficient to obtain the desired concentration of ferric oxide in the final catalytic composition. Other water soluble iron salts can be employed if desired and other basic materials for precipitating iron hydroxide can be employed with substantially equivalent results. The calcining step is advantageously performed by heating the impregnated composition to a temperature of from about 800 F. to 1000 F. in Contact with an oxygen containing gas such as air for a time sufiicient to complete conversion to the oxide. The time required for the oxidation is usually from about 15 minutes to 4 hours.

Where it is desired to obtain the final catalytic composition in a specified particle size, it is preferred to pulverize a spent cracking catalyst to obtain the desired size prior to its impregnation with the iron compound. However, particle size can be adjusted after the impregnation and calcining steps if desired.

HYDROCRACKING The reactions involved in the present process for converting hydrocarbons to lower boiling hydrocarbons are primarily the cracking of the relatively heavy hydro carbons and the hydrogenation of unsaturated materials such as olefins, which may be present in the charge stock or formed in the process, to saturated materials. The relatively low boiling products can be separated into desired fractions, such as a gasoline fraction containing hydrocarbons having 4 carbon atoms up to those boiling at 400 F. (C 400 F.), a middle oil containing hydrocarbons boiling from 400 F. to 650 F., a heavy oil containing hydrocarbons boiling from 650 F. to 840 F and recycle oil consisting of hydrocarbons boiling above 840 F. Other desired fractions can be separated if desired.

A wide variety of heavy hydrocarbon materials having initial boiling points above 840 F. can be converted in the process of the invention, residues from petroleum cracking operations, reduced heavy crude oil, still tars, and the like, giving good results. It is preferred to use heavy hydrocarbons having a hydrogen to carbon atomic ratio of at least 1.2 and preferably above about 1.4. Good results are obtained when the A.P.I. gravity of the heavy hydrocarbons is below 25, but the process has its greatest utility when the A.P.l. gravity is below about 17. Generally the Ramsbottom carbon residue will be from about 9 to 30, but may be as low as about 4. It is preferred to use tower bottoms from petroleum operations, including for example the residues from thermal or catalytic cracking operations, or reduced heavy crude oils including crude oils having a high content of sulfur compounds, but other heavy hydrocarbon materials such as Athabasca tar can be used. For convenience, the hydrocracking process of the invention is herein de scribed using residual oil as illustrative of the heavy hydrocarbon materials that can be employed.

In the hydrocracking process, the residual oil is contacted with a catalyst of the invention for from about 15 minutes to 8 hours at a temperature of from 700 F. to 925 F., and a pressure of from 1500 p.s.i.g. to 5000 p.s.i.g. At pressures below about 1500 p.s.i.g. the recycle oil obtained from the hydrocracking operation is degraded, as evidenced by an increased Ramsbottom carbon residue as compared to the charge oil, whereas at pressures above 1500 p.s.i.g. the recycle oil from the hydrocracking operation has a reduced Ramsbottom carbon, and can be recycled to extinction, as will be later pointed out in more detail. Hydrogen must be present and preferably a substantial excess is used, such as a mole ratio of hydrogen to oil of from 2 to 20. The process may be operated batchwise or continuously. In batch operation a catalyst to oil weight ratio of from 0.05 to 1 gives good results. In continuous operation, such as a fixed bed operation, a space rate of oil through the reactor of from 0.2 to 6 volumes of oil per volume of catalyst per hour gives good results. Slurry type operation can also be employed using reaction conditions essentially equivalent to those above stated.

It is of primary importance, in operating the process, to relate the reaction conditions so that conversion of the hydrocarbon charge stock to material boiling below the boiling range of the charge stock is maintained below about by weight for each contacting with the catalyst. At higher conversions the production of coke and dry gas become excessive and deleteriously affect the process. For an operable process, however, the conversion of the charge stock should be above 30% by weight for each contacting with catalyst.

After contacting the residual oil and catalyst under the conditions as stated above, the oil is separated into desired fractions by distillation. A gasoline fraction can be separated and used as motor fuel, as a component of motor fuel, by blending with hydrocarbons from other sources, or used in subsequent refinery operations such as reforming. Distillate oil products can be used without further treatment such as for fuel oil, or can be used in subsequent refinery operations, such as thermal or catalytic cracking. The higher boiling materials, generally the hydrocarbons boiling above 840 F. provide excellent recycle stock for the process since, as shown hereinafter, such materials are upgraded in the process to contain a smaller quantity of materials that are convertible to coke than is contained by the initial charge material.

Example Iron oxide was deposited on the spent cracking catalyst. The spent cracking catalyst consisted of about 87% silica and about 13% alumina and had been employed in a commercial installation involving the catalytic cracking of a gas oil. During the period of cracking the catalyst had been subjected to many regenerations and its initial equilibrium activity of 32 decreased so that regeneration restored an activity of 12, i.e., the catalytic activity decreased by about 62.5%. Catalytic activity was measured by the method cited above. The spent catalyst contained minor amounts of various metals including at least about 0.1% to 1% of titanium, vanadium and iron, and at least about 0.001% to 0.1% chromium, and at least about 0.01% to 1% nickel. This spent catalyst was impregnated in an aqueous solution of ferrous sulfate in a quantity sufiicient to give 7% by weight ferric oxide in the final composition. An aqueous solution of sodium hydroxide sufficient to precipitate ferric hydroxide was then added. The composition was washed, dried and heated to about 1000 F. in contact with air for about 4 hours. The final composition consisted of a spent cracking catalyst containing 7% by weight of ferric oxide deposited thereon. The final catalytic composition thus contained about 81.4% by weight silica, about 12.1% by weight alumina and about 6.5% by weight Fe O For comparison and to emphasize the necessity of using ferric oxide as a catalytic component, the foregoing preparation was repeated except that molybdic oxide was the final catalytic component in place of ferric oxide. The catalyst was prepared by impregnating the spent cracking catalyst, as above described, with an aqueous solution of ammonium molybdate. The subsequent treatment was as for the iron oxide composition. The final composition consisted of the spent cracking catalyst having deposited thereon 5% by weight molybdic oxide.

Both of the catalytic compositions were used to hydrocrack the same residual oil. The residual oil charge stock was from the vacuum distillation of crude oil, and had an initial boiling point of about 840 F., an A.P.I. gravity of 15.3, a Ramsbottom carbon residue of 9.3% by weight, a hydrogen to carbon atomic ratio of 1.60, and contained 0.77% by weight sulfur compounds (calculated as sulfur).

In carrying out the process, the indicated catalyst and residual oil were introduced into a reactor, the catalyst to oil Weight ratio being 0.1. The reactor was flushed with hydrogen and hydrogen introduced to a pressure of 2100 p.s.i.g., the hydrogen to oil mole ratio being about 6. The reactor was then heated and maintained at a temperature of 800 F. for 2 hours. After cooling, the catalyst was separated and the hydrocarbon reaction mixture distilled to separate desired fractions. The results obtained with the catalysts prepared as above described are shown in the following Table I. In the table the results obtained with the iron oxide catalyst are designated as catalytic composition A. Results obtained with the molybdic oxide catalyst are designated catalytic composition B. For comparison, results obtained using the spent cracking catalyst as above described, without the deposition of an additional metal oxide thereon, are shown designated as catalytic composition C.

TABLE I Oatalytic Composition A B 0 Product distribution (wt. percent):

Dry gas (Or-O3) 5 3 8 Gasoline (Or-400 F.) Middle oil (400-650 F.) Heavy oil (650-840 F.)

The data of Table I show good operation in accordance with the invention using the catalyst of the invention. Thus the data of column A show good conversion of the residual oils to lower boiling products. The Ramsbottom carbon residue of the recycle oil was substantially less than the Ramsbottom carbon residue of the charge stock. Hence the value of the recycle oil for reuse in the process was substantially enhanced so that even better results are obtainable therewith on reuse in the process, and the oil can be recycled to substantial extinction, i.e., can be substantially completely converted to lower boiling, more valuable products.

In contrast to the data of column A, the data of column B (molybdic oxide containing catalyst) show a degradation of the recycle oil as compared to the charge stock (by the increase in Ramsbottom carbon residue), and hence operation therewith is unsatisfactory and outside the scope of the invention.

The data of column C show a very substantial degradation of the recycle oil when the spent cracking catalyst alone is used, thus showing the necessity for using ferric oxide as a catalytic component.

In order to determine the effect of pressure on the quality of the recycle stock, other similar runs on the same charge stock were made with a catalyst comprising 1% ferric oxide on a spent clay cracking catalyst. It was found that at 1500 p.s.i.g. and 825 F., under which conditions the conversion was of the same order of magnitude as shown in column A of Table I, the Ramsbottom carbon residue of the product boiling over 840 F. was 9.0, and at 750 p.s.i.g. and 825 F., the Ramsbottom carbon residue of the recycle oil was 12.5. These data indicate that at pressures less than about 1500 p.s.i.g., the catalyst of the present invention is ineffective to produce a recycle oil which is capable of being recycled to extinction.

This application is a continuation in part of our copending application Serial Number 511,419, filed May 26, 1955, now abandoned.

The invention claimed is:

Process for converting hydrocarbons to lower boiling hydrocarbons which comprises contacting, in the presence of hydrogen, a mixture of hydrocarbons boiling above about 840 F. with a catalytic composition consisting essentially of a spent cracking catalyst having deposited thereon from 0.5 to 10% by weight ferric oxide, said spent cracking catalyst having previously been utilized as the catalyst in a process for cracking hydrocarbons until its cracking activity was spent to an extent of at least 30% of its initial cracking activity, under reaction conditions including a temperature of from 700 F. to 925 F. and a pressure of from 1500 p.s.i.g. to 5000 p.s.i.g. to convert from 30% to by weight of the hydrocarbons to lower boiling hydrocarbons, separating about 840 F.

References Cited in the file of this patent UNITED STATES PATENTS Gilbert et a1 July 10, 1951 8 Mills et a1. Feb. 21, 1956 Jahnig Sept. 4, 1956 Heinemann et a1 Oct. 9,1956 Anhorn May 7, 1957 Kennedy et a1 Oct. 28, 1958 Boedeker et a1 Dec. 2, 1958 Lanning Aug. 11, 1959