SLURRY PROCESS FOR HYDROCARBONACEOUS BLACK OIL CONVERSION
United States Patent 3657111
A catalytic slurry hydrorefining process of a hydrocarbonaceous charge stock containing hydrocarbon-insoluble asphaltenes is effected by dissolving in the charge stock an oxyvanadate salt having the following structural formula: [N(R)4 ]3 V0(X)5 wherein "X" is a cyano, or thiocyano radical, and "R" is hydrogen, or an alkyl group containing up to 10 carbon atoms. The slurry is formed in situ at hydrorefining conditions with hydrogen containing hydrogen sulfide resulting in colloidally dispersed vanadium sulfide.
US Patent References:
Hydrorefining of crude oil and catalyst therefor
Gleim et al. - January 1965 - 3165463
Crude oil hydrorefining process
Gleim et al. - May 1966 - 3252895
/3558474.html
Gleim et al. - January 1971 - 3558474
Hydrorefining of crude oil and catalyst therefor
Gleim et al. - January 1965 - 3165463
Crude oil hydrorefining process
Gleim et al. - May 1966 - 3252895
/3558474.html
Gleim et al. - January 1971 - 3558474
Application Number:
05/013838
Publication Date:
04/18/1972
Filing Date:
02/24/1970
View Patent Images:
Export Citation:
Assignee:
Universal Oil Products Company (Des Plaines, IL)
Primary Class:
Other Classes:
208/213, 208/215
International Classes:
C10G45/16; C10G45/02; C10G13/06; C10G23/06
Field of Search:
208/215,209,213,108,251H,254H,264
Primary Examiner:
Gantz, Delbert E.
Assistant Examiner:
Crasankis G. J.
Claims:
I claim as my invention
1. A process for hydrorefining an asphaltene-containing hydrocarbon charge stock which comprises dissolving in said charge stock a hydrocarbon-soluble oxovanadate salt having the following structural formula:
2. The process of claim 1 further characterized in that said charge stock is admixed with from 1.0 percent to about 25.0 percent by weight of said oxovanadate salt.
3. The process of claim 1 further characterized in that said oxovanadate salt is a pentacyano-oxovanadatealkylammonium salt.
4. The process of claim 1 further characterized in that said oxovanadate salt is a pentathiocyano-oxovanadate-alkylammonium salt.
5. The process of claim 1 further characterized in that said alkyl group contains from 1 to 6 carbon atoms.
6. The process of claim 1 further characterized in that said hydrorefining conditions include a temperature from 225° C. to about 500° C. and a pressure from 500 p.s.i.g. to about 5,000 p.s.i.g.
7. The process of claim 1 further characterized in that said hydrogen contains from 1.0 mol percent to about 20.0 mol percent hydrogen sulfide.
1. A process for hydrorefining an asphaltene-containing hydrocarbon charge stock which comprises dissolving in said charge stock a hydrocarbon-soluble oxovanadate salt having the following structural formula:
2. The process of claim 1 further characterized in that said charge stock is admixed with from 1.0 percent to about 25.0 percent by weight of said oxovanadate salt.
3. The process of claim 1 further characterized in that said oxovanadate salt is a pentacyano-oxovanadatealkylammonium salt.
4. The process of claim 1 further characterized in that said oxovanadate salt is a pentathiocyano-oxovanadate-alkylammonium salt.
5. The process of claim 1 further characterized in that said alkyl group contains from 1 to 6 carbon atoms.
6. The process of claim 1 further characterized in that said hydrorefining conditions include a temperature from 225° C. to about 500° C. and a pressure from 500 p.s.i.g. to about 5,000 p.s.i.g.
7. The process of claim 1 further characterized in that said hydrogen contains from 1.0 mol percent to about 20.0 mol percent hydrogen sulfide.
Description:
APPLICABILITY OF INVENTION
The invention described herein is adaptable to a process for effecting the conversion of asphaltene-containing petroleum fractions into lower-boiling hydrocarbon products. More specifically, the present invention is directed toward a slurry-type catalytic process for continuously converting hydrocarbonaceous material such as atmospheric tower bottoms, vacuum tower bottoms (vacuum residuum), crude oil residuals, topped crude oils, coal oil extracts, crude oils extracted from tar sands, etc., all of which are generally referred to in the art as "black oils." In particular, the process described herein affords a high degree of asphaltene conversion into hydrocarbon-soluble products, while simultaneously effecting a substantial degree of hydrorefining in order to reduce the concentration of sulfurous and nitrogenous compounds.
Hydrocarbonaceous black oils contain high molecular weight, sulfurous compounds in exceedingly large quantities. Black oils also contain excessive quantities of nitrogenous compounds, high molecular weight organo-metallic complexes, principally comprising nickel and vanadium, and hydrocarbon-insoluble asphaltenic material. The latter is generally found to be complexed or linked with sulfur and, to a certain extent, with the organo-metallic contaminants. An abundant supply of such hydrocarbonaceous material exists, most of which has a gravity less than 20.0° API, and which is further characterized by a boiling range indicating that at least 10.0 percent by volume has a normal boiling point above a temperature of about 1,050° F.
The process of the present invention is particularly directed toward the catalytic conversion of black oils into distillable hydrocarbons. Specific examples of black oils, illustrative of those to which the present invention is especially applicable, include a full boiling range Wyoming sour crude oil, having a gravity of about 23.2 °API, and containing about 2,8 percent by weight of sulfur, approximately 2,700 p.p.m. of total nitrogen, a total of about 100 p.p.m. of metallic contaminants (computed as elemental nickel and vanadium) and an insoluble asphaltenic fraction in an amount of about 8.4 percent by weight; a crude tower bottoms product, having a gravity of about 14.3 °API, and containing about 3.0 percent by weight of sulfur, 3,800 p.p.m. of total nitrogen, about 85 ppm. of total metals, and about 10.9 percent by weight of asphaltenic material; and, a vacuum tower bottoms product having a gravity of about 7.0 °API, and containing more than 6,000 ppm. of nitrogen, about 4.0 percent by weight of sulfur, more than 450 ppm. of metallic contaminants and about 24.0 percent by weight of pentane-insoluble asphaltenic material.
With respect to such charge stocks, the principal difficulty, heretofore encountered in a fixed-bed catalytic unit, resides in the lack of sufficient catalyst stability in the presence of the asphaltenic compounds and the excessive concentrations of sulfur. The asphaltenic fraction consists primarily of high molecular weight, non-distillable coke precursors, and is insoluble in light hydrocarbons such as propane, pentane, heptane. In addition to the asphaltenes, sulfurous and nitrogenous compounds, hydrocarbonaceous black oils contain large quantities of metallic contaminants generally in the range of about 50 p.p.m. to as high as 1,000 p.p.m. by weight, calculated as the elemental metals. A reduction in the concentration of the organo-metallic contaminants, such as metal porphyrins, is not easily achieved, and to the extent that the same no longer exert detrimental effects with respect to further processing. The difficulties encountered with a fixed-bed catalytic unit have lead to extensive investigations into slurry processing utilizing a solid, unsupported catalyst in admixture with the charge stock.
The primary purpose of the present invention is to provide an efficient and economical slurry process for the conversion or hydrorefining of heavy hydrocarbonaceous material containing insoluble asphaltenes. The term "hydrorefining," as employed herein, connotes the catalytic treatment, in an atmosphere of hydrogen, of a hydrocarbon fraction or distillate for the purpose of eliminating and/or reducing the concentration of the various contaminating influences previously described. The present invention involves the use of a colloidally dispersed, unsupported catalytic material. There is afforded a greater yield of liquid hydrocarbon products which are suitable for further processing without experiencing the difficulties otherwise resulting from the presence of the foregoing contaminating influences.
The unsupported catalyst, utilized in the slurry process of the present invention, is a vanadium sulfide of non-stoichiometric sulfur content. Prior investigations have indicated that this catalytic component, in unsupported form, yields the most advantageous results. The novel concept, upon which the present invention is founded, resides in the manner in which the catalytic vanadium sulfide is caused to be colloidally dispersed within the charge stock.
OBJECTS AND EMBODIMENTS
As hereinbefore set forth, a principal object of the present invention resides in providing a slurry process for the conversion of petroleum black oils. A corollary object is to convert hydrocarbon-insoluble asphaltenes into hydrocarbon-soluble, lower-boiling normally liquid products.
Another object is to effect the destructive removal of sulfurous and nitrogenous compounds through the conversion thereof to hydrocarbons, hydrogen sulfide and ammonia.
A specific object of my invention is to effect the continuous decontamination of asphaltenic black oils by providing a slurry process utilizing a solid, unsupported vanadium sulfide catalyst. In conjunction with this object, it is intended to provide a commercially feasible method for intimately dispersing the catalytic vanadium sulfide within the fresh feed charge stock.
These objects are accomplished by admixing the fresh feed charge stock with an oxovanadate salt having the following structural formula:
[N(R) 4 ] 3 VO(X) 5
wherein "X" is a cyano, or thiocyano radical, and "R" is hydrogen, or an alkyl group containing up to about 10 carbon atoms, and reacting the resulting mixture with hydrogen and hydrogen-sulfide whereby the catalytic vanadium sulfide is produced in situ within the reaction zone.
Therefore, in one embodiment, my invention encompasses a process for hydrorefining an asphaltene-containing hydrocarbon charge stock which comprises admixing said charge stock with a hydrocarbon-soluble oxovanadate salt having the following structural formula:
[N(R) 4] 3VO(X) 5
wherein "X" is a cyano, or thiocyano radical, and "R" is hydrogen, or an alkyl group containing up to about 10 carbon atoms and, reacting the resulting mixture, at hydrorefining conditions, with hydrogen containing hydrogen sulfide.
Other embodiments of my invention reside in the utilization of particular operating conditions and techniques, concentration of reactants, etc. These are well as other objects and embodiments will become apparent from the following more detailed summary of my invention.
SUMMARY OF INVENTION
The unsupported catalyst utilized in the slurry process of my invention, is a vanadium sulfide of non-stoichiometric sulfur content. The use of the term "unsupported" is intended to designate a catalyst or catalytic component which is not an integral part of a composite with a refractory inorganic oxide carrier material. That is, the catalyst is a non-stoichiometric vanadium sulfide without the addition thereto of extraneous material. While the precise atomic ration of sulfur to vanadium, in the catalytic, non-stoichiometric vanadium sulfide, is not know with accuracy, the catalytic vanadium sulfide is known to have a ratio of sulfur to vanadium not less than 0.8:1, nor greater than l.8:1. This is not intended to mean that the vanadium sulfide catalyst has but a single specific sulfur/vanadium atomic ratio, but rather refers to a mixture of vanadium sulfides having sulfur/vanadium atomic ratios within the aforesaid range. Although four oxidation states are known for vanadium, 2, 3, 4 and 5, Periodic Table of the Elements, E. H. Sargent and Company, 1964, only three stoichiometric vanadium sulfides are sufficiently stable for identification. These are: mono-vanadium sulfides, VS; sesqui-vanadium sulfide, V 2S 3; and, penta-vanadium sulfide, V 2S 5 , Handbook of Chemistry and Physics, Chemical Rubber Publishing Company, 42 nd Edition, Page 680, 1960-1961. However, many literature references are replete with examples of a multitude of identifiable non-stoichiometric vanadium sulfides which are specific compounds in their own right, as indicated by their individual X-ray patterns which are distinct and reproducible. Significantly, I have previously found that the catalytic vanadium sulfide is not identifiable with any of the stoichiometric vanadium sulfides. The present invention is primarily directed toward a method for producing the catalytic, non-stoichiometric vanadium sulfide in situ, which method affords a commercially feasible, economical slurry-type process.
As hereinabove set forth, it has been found that colloidally dispersed, non-stoichiometric vanadium sulfides are capable of effecting the hydrorefining of a wide variety of petroleum black oils in a slurry-type process. Furthermore, it has previously been shown that these catalytic vanadium sulfides must necessarily be produced in situ in order to yield more advantageous results. In accordance with the present invention, the production of the finely divided catalytic vanadium sulfide is accomplished by initially dissolving a hydrocarbon-soluble oxovanadate salt in the fresh feed charge stock. Heretofore, the dispersion complexes been accomplished by dissolving organic complexed of tetravalent vanadium in the charge stock. However, the high cost of the complexing agent, for example, acetyl acetone, or methyl napthalene, prohibits their use in a commercially-scaled process where the fresh feed charge rate may be as high as 40,000 barrels per day. I have now found that the eventual catalyst can be produced within the reaction system by dissolving, in the fresh feed charge stock, an oxovanadate salt having the following structural formula:
[N(R) 4] 3VO(X) 5.
wherein "X" is either a cyano, or thio cyano radical, and "R" is either hydrogen, or an alkyl group containing up to about ten carbon atoms. Preferred alkyl groups are those containing from one to six carbon atoms, inclusive. It is understood that oxovanadate salts containing alkyl groups of varying carbon chain length may also be used. Thus, the catalytic vanadium sulfide precursor includes mono-, di-, tri- and tetramethyl-, ethyl-, propyl-, amyl- and hexylammonium pentacyanooxovanadate, the thio analogs thereof, and mixtures. Exemplary, but not intended to be limited are: the tetramethylammonium salt of pentacyanooxovanadate; the dimethyldiethylammonium salt of pentacyanooxovanadate; the tetrapropylammonium salt of pentacyanooxovanadate; the tri- butylamylammonium salt of pentacyanooxovanadate; the amyltrihexylammonium salt of pentacyanooxovanadate; the dipnopyldibutylammonium salt of pentathiocyanooxovanadate; the tetramethylammonium salt of pentathiocyanooxovanadate and the tetraethylammonium salt of pentacyanooxovanadate, etc. These compounds are readily prepared by adding the appropriate alkylammonium bromide to a water solution of vanadyl sulfate in 6 normal sodium cyanide or thiocyanide, depending on whether the pentacyano or pentathiocyano salt is desired. The selected oxovanadate salt, or mixtures of such salts, are employed in an amount of from 1.0 Percent to about 25.0 percent by weight of the fresh feed charge stock.
The charge stock/oxovanadate salt mixture is commingled with hydrogen in an amount of from 5,000 to about 10,000 scf./Bb1. which hydrogen contains hydrogen sulfide in an amount of 1.0 mol percent to about 20.0 mol percent. Following suitable heat-exchange with various hot effluent streams, the temperature of the mixture is further increased to the level desired at the inlet to the reaction zone, or chamber. Since the reactions being effected are principally exothermic, the temperature of the effluent from the reaction chamber will be higher than the inlet temperature thereto. The inlet temperature is generally controlled at a minimum level of about 225° C. and at higher levels such that the outlet temperature does not exceed about 500° C. Experience indicates that excellent results are generally attainable when the temperature gradient across the reaction chamber is about 380° C. to about 450° C. The reaction zone is maintained under an imposed pressure greater than about 500 p.s.i.g., and preferably at a level of from 1,500 to about 5,000 p.s.i.g.
Although the present process may be effected in an elongated reaction zone, with the mixture being introduced thereto in the upper portion thereof and the effluent being removed from a lower portion, an upflow system offers numerous advantages. The principal advantage resides in the fact that the extremely heavy portion of the charge stock has an appreciably longer residence time within the reaction zone, with the result that a greater degree of conversion is attainable, and incoming hydrogen will effectively strip lower-boiling products therefrom. Also, the heavy unconverted asphaltenic material can be withdrawn from the bottom of the reaction chamber along with particles of the catalytic vanadium sulfide formed in situ at the foregoing reaction conditions. The internals of the reaction chamber, or vessel, may be constructed in any suitable manner capable of providing the required intimate contact between the charge stock, the gaseous mixture and the catalyst. In some instances, it may be desirable to facilitate distribution by means of perforated trays or other well known mechanical devices.
The liquid product effluent, containing distillable hydrocarbons, along with hydrogen, hydrogen sulfide, ammonia and normally gaseous hydrocarbons, principally methane, ethane and propane, are removed from the upper portion of the reaction chamber. A hot flash system, functioning at essentially the same pressure as the reaction chamber in a first stage, and at a substantially reduced pressure in a subsequent stage, serves to separate the overhead product effluent into a principally vaporous phase, the greater proportion of which boils below about 800° F., and a principally liquid phase boiling above about 800° F. The latter may be recycled to combine with the fresh charge stock, thereby serving as a diluent, or it may be conveniently employed to facilitate the introduction of the hydrocarbon-soluble oxovanadate salt to the reaction chamber.
The principally vaporous phase passes into a cold, high pressure separator (about 60° F. to about 140° F.), wherein a hydrogen-rich gaseous phase is recovered and recycled, along with make-up hydrogen required to supplant that consumed within the reaction chamber. The normally liquid phase from the cold separator, containing some butane, is generally subjected to fractionation to prepare a charge stock suitable for further processing. The hot flash system may also function to remove all distillable hydrocarbons boiling below any other desired temperature such as 750° F., 950° F., 1,050° F., etc.
With respect to the bottom stream from the reaction chamber, it may be totally recycled to combine with the fresh hydrocarbonaceous charge stock. However, a preferred operating technique involves withdrawing a drag stream containing at least about 10.0 percent by weight of the catalytic vanadium sulfide. Any suitable means may be utilized to separate the solid catalyst and unreacted asphaltenic material from the liquid-phase hydrocarbons, including filtration, settling tanks, a series of centrifuges, etc. A like quantity of the hydrocarbon-soluble oxovanadate salt is then added in order to maintain the desired catalyst content of the slurry.
The material withdrawn from the drag stream is separated, for example, by a series of filtration and methyl naphthalene washing techniques. Methyl naphthalene is employed to remove residual soluble hydrocarbons from the vanadium sulfide-containing sludge. The remainder of the sludge may then be burned in air to produce vanadium pentoxide which may then be converted into an oxovanadate salt. The salt is redissolved in the hydrocarbon charge stock, or recycle diluent, and introduced into the reaction chamber wherein the catalytic vanadium sulfide is formed.
DESCRIPTION OF A PREFERRED EMBODIMENT
The fresh feed charge stock in this illustrative embodiment is a sour Wyoming crude oil having a gravity of about 23.2° API. The crude oil contains about 2.8 percent by weight of sulfur, 2,700 p.p.m. by weight of nitrogen and about 8.4 percent by weight of hydrocarbon-insoluble asphaltenic material. Analyses further indicate a total of about 100 ppm. of metallic porphyrins, computed as elemental nickel and vanadium.
The tetramethylammonium salt of pentacyanooxovanadate is dissolved in the charge stock in an amount of about 5.0 percent by weight. The reaction zone is pressured to a level of about 3,000 p.s.i.g., utilizing compressive hydrogen recycle in an amount of about 20,000 scf/Bbl; the hydrogen recycle stream contains about 15.0 mol percent hydrogen sulfide.
The charge stock hydrogen mixture is circulated through a block heater at a temperature of about 250° C. for a period of about one hour. The temperature of the block heater is increased to a level such that the temperature gradient, from the inlet to the reaction zone to the outlet thereof, is controlled at about 380° C. to about 450° C. The fresh feed charge rate is about 150 milliliters per hour, and make-up hydrogen is added in an amount of about 12.5 scf./hr.
Following a line-out period of about 12 hours, analyses of the normally liquid product effluent, from about an 8 -hour test period, indicate greater than about 96.5 percent asphaltene conversion, less than about 15.0 p.p.m. of organo-metallic complexes and a gravity of about 30.5° API. Furthermore, approximately 50.0 percent of the sulfurous and nitrogenous compounds are converted into hydrocarbons, hydrogen sulfide and ammonia.
The invention described herein is adaptable to a process for effecting the conversion of asphaltene-containing petroleum fractions into lower-boiling hydrocarbon products. More specifically, the present invention is directed toward a slurry-type catalytic process for continuously converting hydrocarbonaceous material such as atmospheric tower bottoms, vacuum tower bottoms (vacuum residuum), crude oil residuals, topped crude oils, coal oil extracts, crude oils extracted from tar sands, etc., all of which are generally referred to in the art as "black oils." In particular, the process described herein affords a high degree of asphaltene conversion into hydrocarbon-soluble products, while simultaneously effecting a substantial degree of hydrorefining in order to reduce the concentration of sulfurous and nitrogenous compounds.
Hydrocarbonaceous black oils contain high molecular weight, sulfurous compounds in exceedingly large quantities. Black oils also contain excessive quantities of nitrogenous compounds, high molecular weight organo-metallic complexes, principally comprising nickel and vanadium, and hydrocarbon-insoluble asphaltenic material. The latter is generally found to be complexed or linked with sulfur and, to a certain extent, with the organo-metallic contaminants. An abundant supply of such hydrocarbonaceous material exists, most of which has a gravity less than 20.0° API, and which is further characterized by a boiling range indicating that at least 10.0 percent by volume has a normal boiling point above a temperature of about 1,050° F.
The process of the present invention is particularly directed toward the catalytic conversion of black oils into distillable hydrocarbons. Specific examples of black oils, illustrative of those to which the present invention is especially applicable, include a full boiling range Wyoming sour crude oil, having a gravity of about 23.2 °API, and containing about 2,8 percent by weight of sulfur, approximately 2,700 p.p.m. of total nitrogen, a total of about 100 p.p.m. of metallic contaminants (computed as elemental nickel and vanadium) and an insoluble asphaltenic fraction in an amount of about 8.4 percent by weight; a crude tower bottoms product, having a gravity of about 14.3 °API, and containing about 3.0 percent by weight of sulfur, 3,800 p.p.m. of total nitrogen, about 85 ppm. of total metals, and about 10.9 percent by weight of asphaltenic material; and, a vacuum tower bottoms product having a gravity of about 7.0 °API, and containing more than 6,000 ppm. of nitrogen, about 4.0 percent by weight of sulfur, more than 450 ppm. of metallic contaminants and about 24.0 percent by weight of pentane-insoluble asphaltenic material.
With respect to such charge stocks, the principal difficulty, heretofore encountered in a fixed-bed catalytic unit, resides in the lack of sufficient catalyst stability in the presence of the asphaltenic compounds and the excessive concentrations of sulfur. The asphaltenic fraction consists primarily of high molecular weight, non-distillable coke precursors, and is insoluble in light hydrocarbons such as propane, pentane, heptane. In addition to the asphaltenes, sulfurous and nitrogenous compounds, hydrocarbonaceous black oils contain large quantities of metallic contaminants generally in the range of about 50 p.p.m. to as high as 1,000 p.p.m. by weight, calculated as the elemental metals. A reduction in the concentration of the organo-metallic contaminants, such as metal porphyrins, is not easily achieved, and to the extent that the same no longer exert detrimental effects with respect to further processing. The difficulties encountered with a fixed-bed catalytic unit have lead to extensive investigations into slurry processing utilizing a solid, unsupported catalyst in admixture with the charge stock.
The primary purpose of the present invention is to provide an efficient and economical slurry process for the conversion or hydrorefining of heavy hydrocarbonaceous material containing insoluble asphaltenes. The term "hydrorefining," as employed herein, connotes the catalytic treatment, in an atmosphere of hydrogen, of a hydrocarbon fraction or distillate for the purpose of eliminating and/or reducing the concentration of the various contaminating influences previously described. The present invention involves the use of a colloidally dispersed, unsupported catalytic material. There is afforded a greater yield of liquid hydrocarbon products which are suitable for further processing without experiencing the difficulties otherwise resulting from the presence of the foregoing contaminating influences.
The unsupported catalyst, utilized in the slurry process of the present invention, is a vanadium sulfide of non-stoichiometric sulfur content. Prior investigations have indicated that this catalytic component, in unsupported form, yields the most advantageous results. The novel concept, upon which the present invention is founded, resides in the manner in which the catalytic vanadium sulfide is caused to be colloidally dispersed within the charge stock.
OBJECTS AND EMBODIMENTS
As hereinbefore set forth, a principal object of the present invention resides in providing a slurry process for the conversion of petroleum black oils. A corollary object is to convert hydrocarbon-insoluble asphaltenes into hydrocarbon-soluble, lower-boiling normally liquid products.
Another object is to effect the destructive removal of sulfurous and nitrogenous compounds through the conversion thereof to hydrocarbons, hydrogen sulfide and ammonia.
A specific object of my invention is to effect the continuous decontamination of asphaltenic black oils by providing a slurry process utilizing a solid, unsupported vanadium sulfide catalyst. In conjunction with this object, it is intended to provide a commercially feasible method for intimately dispersing the catalytic vanadium sulfide within the fresh feed charge stock.
These objects are accomplished by admixing the fresh feed charge stock with an oxovanadate salt having the following structural formula:
[N(R) 4 ] 3 VO(X) 5
wherein "X" is a cyano, or thiocyano radical, and "R" is hydrogen, or an alkyl group containing up to about 10 carbon atoms, and reacting the resulting mixture with hydrogen and hydrogen-sulfide whereby the catalytic vanadium sulfide is produced in situ within the reaction zone.
Therefore, in one embodiment, my invention encompasses a process for hydrorefining an asphaltene-containing hydrocarbon charge stock which comprises admixing said charge stock with a hydrocarbon-soluble oxovanadate salt having the following structural formula:
[N(R) 4] 3VO(X) 5
wherein "X" is a cyano, or thiocyano radical, and "R" is hydrogen, or an alkyl group containing up to about 10 carbon atoms and, reacting the resulting mixture, at hydrorefining conditions, with hydrogen containing hydrogen sulfide.
Other embodiments of my invention reside in the utilization of particular operating conditions and techniques, concentration of reactants, etc. These are well as other objects and embodiments will become apparent from the following more detailed summary of my invention.
SUMMARY OF INVENTION
The unsupported catalyst utilized in the slurry process of my invention, is a vanadium sulfide of non-stoichiometric sulfur content. The use of the term "unsupported" is intended to designate a catalyst or catalytic component which is not an integral part of a composite with a refractory inorganic oxide carrier material. That is, the catalyst is a non-stoichiometric vanadium sulfide without the addition thereto of extraneous material. While the precise atomic ration of sulfur to vanadium, in the catalytic, non-stoichiometric vanadium sulfide, is not know with accuracy, the catalytic vanadium sulfide is known to have a ratio of sulfur to vanadium not less than 0.8:1, nor greater than l.8:1. This is not intended to mean that the vanadium sulfide catalyst has but a single specific sulfur/vanadium atomic ratio, but rather refers to a mixture of vanadium sulfides having sulfur/vanadium atomic ratios within the aforesaid range. Although four oxidation states are known for vanadium, 2, 3, 4 and 5, Periodic Table of the Elements, E. H. Sargent and Company, 1964, only three stoichiometric vanadium sulfides are sufficiently stable for identification. These are: mono-vanadium sulfides, VS; sesqui-vanadium sulfide, V 2S 3; and, penta-vanadium sulfide, V 2S 5 , Handbook of Chemistry and Physics, Chemical Rubber Publishing Company, 42 nd Edition, Page 680, 1960-1961. However, many literature references are replete with examples of a multitude of identifiable non-stoichiometric vanadium sulfides which are specific compounds in their own right, as indicated by their individual X-ray patterns which are distinct and reproducible. Significantly, I have previously found that the catalytic vanadium sulfide is not identifiable with any of the stoichiometric vanadium sulfides. The present invention is primarily directed toward a method for producing the catalytic, non-stoichiometric vanadium sulfide in situ, which method affords a commercially feasible, economical slurry-type process.
As hereinabove set forth, it has been found that colloidally dispersed, non-stoichiometric vanadium sulfides are capable of effecting the hydrorefining of a wide variety of petroleum black oils in a slurry-type process. Furthermore, it has previously been shown that these catalytic vanadium sulfides must necessarily be produced in situ in order to yield more advantageous results. In accordance with the present invention, the production of the finely divided catalytic vanadium sulfide is accomplished by initially dissolving a hydrocarbon-soluble oxovanadate salt in the fresh feed charge stock. Heretofore, the dispersion complexes been accomplished by dissolving organic complexed of tetravalent vanadium in the charge stock. However, the high cost of the complexing agent, for example, acetyl acetone, or methyl napthalene, prohibits their use in a commercially-scaled process where the fresh feed charge rate may be as high as 40,000 barrels per day. I have now found that the eventual catalyst can be produced within the reaction system by dissolving, in the fresh feed charge stock, an oxovanadate salt having the following structural formula:
[N(R) 4] 3VO(X) 5.
wherein "X" is either a cyano, or thio cyano radical, and "R" is either hydrogen, or an alkyl group containing up to about ten carbon atoms. Preferred alkyl groups are those containing from one to six carbon atoms, inclusive. It is understood that oxovanadate salts containing alkyl groups of varying carbon chain length may also be used. Thus, the catalytic vanadium sulfide precursor includes mono-, di-, tri- and tetramethyl-, ethyl-, propyl-, amyl- and hexylammonium pentacyanooxovanadate, the thio analogs thereof, and mixtures. Exemplary, but not intended to be limited are: the tetramethylammonium salt of pentacyanooxovanadate; the dimethyldiethylammonium salt of pentacyanooxovanadate; the tetrapropylammonium salt of pentacyanooxovanadate; the tri- butylamylammonium salt of pentacyanooxovanadate; the amyltrihexylammonium salt of pentacyanooxovanadate; the dipnopyldibutylammonium salt of pentathiocyanooxovanadate; the tetramethylammonium salt of pentathiocyanooxovanadate and the tetraethylammonium salt of pentacyanooxovanadate, etc. These compounds are readily prepared by adding the appropriate alkylammonium bromide to a water solution of vanadyl sulfate in 6 normal sodium cyanide or thiocyanide, depending on whether the pentacyano or pentathiocyano salt is desired. The selected oxovanadate salt, or mixtures of such salts, are employed in an amount of from 1.0 Percent to about 25.0 percent by weight of the fresh feed charge stock.
The charge stock/oxovanadate salt mixture is commingled with hydrogen in an amount of from 5,000 to about 10,000 scf./Bb1. which hydrogen contains hydrogen sulfide in an amount of 1.0 mol percent to about 20.0 mol percent. Following suitable heat-exchange with various hot effluent streams, the temperature of the mixture is further increased to the level desired at the inlet to the reaction zone, or chamber. Since the reactions being effected are principally exothermic, the temperature of the effluent from the reaction chamber will be higher than the inlet temperature thereto. The inlet temperature is generally controlled at a minimum level of about 225° C. and at higher levels such that the outlet temperature does not exceed about 500° C. Experience indicates that excellent results are generally attainable when the temperature gradient across the reaction chamber is about 380° C. to about 450° C. The reaction zone is maintained under an imposed pressure greater than about 500 p.s.i.g., and preferably at a level of from 1,500 to about 5,000 p.s.i.g.
Although the present process may be effected in an elongated reaction zone, with the mixture being introduced thereto in the upper portion thereof and the effluent being removed from a lower portion, an upflow system offers numerous advantages. The principal advantage resides in the fact that the extremely heavy portion of the charge stock has an appreciably longer residence time within the reaction zone, with the result that a greater degree of conversion is attainable, and incoming hydrogen will effectively strip lower-boiling products therefrom. Also, the heavy unconverted asphaltenic material can be withdrawn from the bottom of the reaction chamber along with particles of the catalytic vanadium sulfide formed in situ at the foregoing reaction conditions. The internals of the reaction chamber, or vessel, may be constructed in any suitable manner capable of providing the required intimate contact between the charge stock, the gaseous mixture and the catalyst. In some instances, it may be desirable to facilitate distribution by means of perforated trays or other well known mechanical devices.
The liquid product effluent, containing distillable hydrocarbons, along with hydrogen, hydrogen sulfide, ammonia and normally gaseous hydrocarbons, principally methane, ethane and propane, are removed from the upper portion of the reaction chamber. A hot flash system, functioning at essentially the same pressure as the reaction chamber in a first stage, and at a substantially reduced pressure in a subsequent stage, serves to separate the overhead product effluent into a principally vaporous phase, the greater proportion of which boils below about 800° F., and a principally liquid phase boiling above about 800° F. The latter may be recycled to combine with the fresh charge stock, thereby serving as a diluent, or it may be conveniently employed to facilitate the introduction of the hydrocarbon-soluble oxovanadate salt to the reaction chamber.
The principally vaporous phase passes into a cold, high pressure separator (about 60° F. to about 140° F.), wherein a hydrogen-rich gaseous phase is recovered and recycled, along with make-up hydrogen required to supplant that consumed within the reaction chamber. The normally liquid phase from the cold separator, containing some butane, is generally subjected to fractionation to prepare a charge stock suitable for further processing. The hot flash system may also function to remove all distillable hydrocarbons boiling below any other desired temperature such as 750° F., 950° F., 1,050° F., etc.
With respect to the bottom stream from the reaction chamber, it may be totally recycled to combine with the fresh hydrocarbonaceous charge stock. However, a preferred operating technique involves withdrawing a drag stream containing at least about 10.0 percent by weight of the catalytic vanadium sulfide. Any suitable means may be utilized to separate the solid catalyst and unreacted asphaltenic material from the liquid-phase hydrocarbons, including filtration, settling tanks, a series of centrifuges, etc. A like quantity of the hydrocarbon-soluble oxovanadate salt is then added in order to maintain the desired catalyst content of the slurry.
The material withdrawn from the drag stream is separated, for example, by a series of filtration and methyl naphthalene washing techniques. Methyl naphthalene is employed to remove residual soluble hydrocarbons from the vanadium sulfide-containing sludge. The remainder of the sludge may then be burned in air to produce vanadium pentoxide which may then be converted into an oxovanadate salt. The salt is redissolved in the hydrocarbon charge stock, or recycle diluent, and introduced into the reaction chamber wherein the catalytic vanadium sulfide is formed.
DESCRIPTION OF A PREFERRED EMBODIMENT
The fresh feed charge stock in this illustrative embodiment is a sour Wyoming crude oil having a gravity of about 23.2° API. The crude oil contains about 2.8 percent by weight of sulfur, 2,700 p.p.m. by weight of nitrogen and about 8.4 percent by weight of hydrocarbon-insoluble asphaltenic material. Analyses further indicate a total of about 100 ppm. of metallic porphyrins, computed as elemental nickel and vanadium.
The tetramethylammonium salt of pentacyanooxovanadate is dissolved in the charge stock in an amount of about 5.0 percent by weight. The reaction zone is pressured to a level of about 3,000 p.s.i.g., utilizing compressive hydrogen recycle in an amount of about 20,000 scf/Bbl; the hydrogen recycle stream contains about 15.0 mol percent hydrogen sulfide.
The charge stock hydrogen mixture is circulated through a block heater at a temperature of about 250° C. for a period of about one hour. The temperature of the block heater is increased to a level such that the temperature gradient, from the inlet to the reaction zone to the outlet thereof, is controlled at about 380° C. to about 450° C. The fresh feed charge rate is about 150 milliliters per hour, and make-up hydrogen is added in an amount of about 12.5 scf./hr.
Following a line-out period of about 12 hours, analyses of the normally liquid product effluent, from about an 8 -hour test period, indicate greater than about 96.5 percent asphaltene conversion, less than about 15.0 p.p.m. of organo-metallic complexes and a gravity of about 30.5° API. Furthermore, approximately 50.0 percent of the sulfurous and nitrogenous compounds are converted into hydrocarbons, hydrogen sulfide and ammonia.