US3523913A - Method of preparing hydrorefining catalysts - Google Patents

Description

United States Patent 3,523,913 METHOD OF PREPARING HYDROREFINING CATALYSTS Mark J. OHara, Prospect Heights, 111., assignor to Universal Oil Products Company, Des Plaiues, Ill., a corporation of Delaware No Drawing. Filed Mar. 13, 1968, Ser. No. 712,623 Int. Cl. BOlj 11/40 U.S. Cl. 252-455 5 Claims ABSTRACT OF THE DISCLOSURE A method of catalyst preparation. A carrier material is impregnated with an aqueous solution of a soluble compound of a metal of Groups VI B and VIII. A rapid evaporation of water and/or water vapors from contact With the catalyst is effected at temperatures up to about 125 C. The catalyst is useful for hydrorefining of petroleum crude oils and residual oils.

BACKGROUND OF THE INVENTION The present invention relates to a method of preparing an improved hydrorefining catalyst which is particularly adapted to the catalytic hydrorefining of petroleum crude oils and residual oils produced as a result of separating lighter fractions from petroleum crude oil. The residual fuel oils are variously referred to as asphaltum oil, liquid asphalt, black oil, petroleum tailings, residuum, residual reduced crude, bunker fuel oils, etc. Petroleum crude oils and residual oils normally contain nitrogenous and sulfurous compounds, organo-metallic compounds, and pentane-insoluble asphaltenes which alone or in combination seriously impair the conversion of said oils to lower boiling more useful fractions thereof. The nitrogenous and sulfurous compounds can be reduced to an acceptable level at hydro-refining conditions whereby they are converted to ammonia and hydrogen sulfide and readily separated as gaseous products.

The reduction of organo-metallic contaminants and pentane-insoluble asphaltenes is substantially more diffi cult. The organo-metallic contaminants occur principally in the form of organo-metallic compounds such as metal porphyrins and various derivatives thereof. The organometallic contaminants, generally comprising nickel and vanadium but also comprising other metals such as iron and copper, are present in relatively small concentrationsoften less than about ppm. calculated as the elemental metal. Nevertheless, in the subsequent treatment of petroleum feed stocks over catalysts specifically designed to yield a desired product distribution, said metals accumulate on the catalyst to effect a shift in product distribution. Such an effect is undesirable with respect to the catalytic cracking of top petroleum crude oils, as Well as other processes, since the product distribution is shifted in favor of lower liquid product yield, excessive formation of coke and increased hydrogen production. The presence of organo-metallic compounds carried over to the lighter petroleum feed stocks has a similar effect with respect to the catalytic reforming, isomerization, hydrodealkylation, hydrorefining, etc., thereof.

The pentane-insoluble asphaltenes which occur in petroleum crude oils and residual oils comprise a significant fraction thereof. For example, a Wyoming sour crude oil having an API gravity of 232 at 60 F. have been shown to contain about 8.37 weight percent pentane-insoluble asphaltenes. These compounds tend to deposit Within a reaction zone and on the catalyst situated therein forming a gummy hydrocarbonaceous residue which functions as a coke precursor. The deposition of this residue constitutes a significant loss of product and it is economically desirable to convert such asphaltenes into useful hydrocarbon fractions.

In addition to virtually eliminating the organo-metallic contaminants, the hydrorefining process herein contemplated affords the added advantage of converting pentaneinsoluble asphaltenes into pentane-soluble hydrocarbons. The hydrorefining catalyst prepared by the method of this invention effects said conversion at hydrorefining conditions without incurring the relatively rapid deposition of coke and other hydrocarbonaceous matter. It will be appreciated that the overall effect is an increase in the volumetric yield of liquid product substantially equivalent to the amount of pentane-insoluble asphaltenes converted to more valuable pentane-soluble products.

SUMMARY OF THE INVENTION In one of its broad aspects the present invention embodies a method of preparing a hydrorefining catalyst which comprises impregnating a refractory inorganic oxide carrier material with an aqueous solution of a soluble compound of a metal of Groups VI-B and VIII, substantially immediately thereafter effecting a rapid evaporation of water from the resulting composite at a temperature up to about C. and at conditions to remove water vapors from contact with said composite substantially immediately as formed, and calcining the resulting catalyst composite.

The catalyst support or carrier material treated in accordance with the method of this invention is most suitably a refractory inorganic oxide such as alumina, silica, zirconia, thoria, boria, etc., or composites thereof including alumina-silica, alumina-zirconia, and the like. The carrier material is preferred to comprise alumina composited with one or more other refractory inorganic oxides. A carrier material comprising alumina in at least an equimolar amount with silica is particularly desirable. Thus, a carrier material comprising about 63 weight percent alumina composited with about 37 weight percent silica is a particularly effective carrier material. The carrier material is further enhanced by the inclusion of boron phosphate, especially in the case of the preferred alumina-silica composites. Thus, a carrier material comprising about 68 weight percent alumina, 10 weight percent silica and about 22 weight percent boron phosphate is advantageously employed.

The carrier material is preferably prepared to embody the most advantageous physical properties with respect to the hydrorefining process herein contemplated, said properties including a surface area of from about 50 to about 700 square meters per gram, an average pore diameter of from about 20 to about 300 A., and an average pore volume of from about 0.2 to about 2.0 milliliters per gram. The preferred alumina-silica carrier material may be prepared by commingling an aqueous water glass solution with an aluminum chloride hydrosol, or other aluminum salt solution, the resulting mixture being added to a suitable alkaline precipitant, such as ammonium hydroxide, to coprecipitate the hydrogel composite of alumina and silica. The gel is water-washed, filtered and slurried in an aqueous solution of phosphoric and boric acids, the latter being utilized in about equimolar amounts and in a total amount to yield a finished carrier material containing from about 13 Weight percent to about 35 weight percent of boron phosphates. The boron phosphate-containing material is dried and formed into the desired size and/or shape and subsequently calcined.

One preferred method of preparing alumina-silica carrier materials which affords a convenient means of developing the desired physical characteristics, relates to the cogelation of an alumina sol and a silica sol to form spherical gel particles utilizing the well-known oil drop method. Thus, an alumina sol, suitably prepared by disgesting aluminum pellets in aqueous hydrochloric acid solution, is commingled with a silica sol, suitably prepared by the acidification of water glass as is commonly practiced, and the sol blend dispersed as droplets in a hot oil bath whereby galatin occurs with the formation of spheroidal particles. In this type of operation, the silica is set thermally, the alumina being set chemically utilizing ammonia as a neutralizing or setting agent. Usually the amomnia is furnished by an ammonia precursor which is included in the sol. The ammonia precursor is sutiably urea, hexamethylenetetramine, or mixtures thereof, although other weakly basic materials which are substantially stable at normal temperatures but hydrolyzable to ammonia with increasing temperature may be employed. Only a fraction of the ammonia precursor is hydrolyzed or decomposed in the relatively short period during which initial gelation occurs. During the subsequent aging process, the residual precursor retained in the spheroidal gel particles continues to hydrolyze and effect further polymerization of the alumina-silica whereby the pore characteristics of the composite are established. The alumina-silica particles are aged, usually for a period of from about to about 24 hours, at a predetermined temperature, usually from about 120 to about 220 F., and at a predetermined pH value. The aging time may be substantially reduced utilizing the pressure aging techniques. With alumina-silica ratios in the higher range, pressure aging tends toward lower apparent bulk densities.

As previously stated, the foregoing method affords a convenient means of developing the desired physical characteristics of the carrier material. The method includes a number of process variables which affect the physical properties of the alumina-silica composite. However, it should be noted that a particular process variable will not necessarily be as effective to produce a desired result with one alumina-silica ratio as with another. Generally, the aluminum-chloride ratio of the alumina sol will influence the average bulk density of the aluminasilica product and, correspondingly, the pore volume and pore diameter characteristics attendant therewith, lower ratios tending toward higher average bulk densities. Other process variables effecting the physical properties of the catalyst support include the time, temperature and pH at which the particles are aged. Usually, the temperatures in the lower range and shorter aging periods tend toward higher average bulk densities. Surface area properties are normally a function of calcination temperature, a temperature of from about 800 to about 1500 F. being suitably employed. Prior to calcination, the alumina-silica spheres are advantageously treated with an aqueous solution of phosphoric and boric acids as hereinabove described.

It is the general practice to deposit catalytically active metals on a carrier material from an aqueous impregnating solution. Thus, the carrier in a particulate form is immersed in an aqueous solution of a soluble compound of a catalytically active metal. The solution is sufficiently dilute to insure contact with the entire catalyst mass to effect an even distribution of the catalyic component thereon. The impregnation solution therefor commonly comprises a considerable excess of Water in contact with the catalyst mass, said excess being subsequently evaporated to leave a catalytic residue on the carrier material. It is the common practice to expedite said evaporation by means of a rotary steam drier or its equivalent. In the latter case, the catalyst mass is further exposed to a steam atmosphere for periods up to about eight hours or more.

It has been observed that, in the manufacture of the hydrorefining catalyst herein contemplated, the catalyst product yield as well as the catalyst activity is improved when the carrier material is impregnated at conditions to forestall undue exposure of the carrier material to water and/ or water vapor in the course of the impregation process. Accordingly, pursuant to the method of this invention, the carrier material is impregnated with an aqueous solution of soluble compound of a catalytically active metal, the water being substantially immediately thereafter rapidly evaporated from the resulting composite at a temperature up to about C. and at conditions to remove water vapor from contact with said composites substantially immediately as formed.

Upon immersing the carrier material in the impregnating solution, the desired even and equal distribution of the catalytic component is accomplished almost immediately so that evaporation of the water can be effected substantially immediately thereafter. Said evaporation is suitably accelerated utilizing a rotary steam drier apparatus at a temperature up to about 125 C. provided that suitable means are available to remove steam or water vapors from contact with the catalyst substantially immediately as formed. This is suitably accomplished by continuously sweeping the catalyst mass with a flow of dry gas such as air, nitrogen, etc., until the water has been substantially completely evaporated therefrom. Water removal is of course facilitated by using a minimum excess of impregnating solution commensurate with adequate contact of the carrier material in the rotary steam drier. Other means for separating water and/or water vapors from contact with the catalyst during the impregnation process, including the percolating of dry gases through the impregnating solution to extract moisture therefrom, can be suitably employed at temperatures up to about 125 C.

The hydrorefining catalyst of this invention is prepared to contain a metal of Group VI-B and a metal of Group VIII. Thus, the catalyst composite may comprise chromium, molybdenum, and/or tungsten in combination with one or more metals of Group VIII, i.e., iron, nickel, cobalt, platinum, palladium, ruthenium, rhodium, osmium and iridium. The aqueous impregnating solution will thus comprise a soluble compound of a Group VIB metal. Suitable compounds include ammonium molybdate, ammonium paramolybdate, molybdic acid, molybdenum, trioxide, ammonium chromate, ammonium peroxy chromate, chromium acetate, chromus chloride, chromium nitrate, ammonium metatungstate, tungstic acid, etc. The impregnating solution is suitably a common solution of a Group VI-B metal and a Group VIII metal compound. Suitable soluble compounds of Group VIII metals include nickel nitrate, nickel sulfate, nickel chloride, nickel bromide, nickel fluoride, nickel iodide, nickel acetate, nickel formate, cobaltous nitrate, cobaltous sulfate, cobaltous fluoride, ferric fluoride, ferric bromide, ferric nitrate, ferric sulfate, ferric formate, ferric acetate, platinum chloride, chloroplatinic acid, chloropalladic acid, pallaium chloride etc. Of the Group VI-B metals, molybdenum is preferred. The Group VIB metal is suitably employed in an amount to comprise from about 5 to about 20 weight percent of the final catalyst composite. The Group VIII metal, which is preferably nickel, is suitably effective in amounts to comprise from about 0.1 to about 10 weight percent of the final catalyst composite.

The final catalyst composite, after all of the catalytic components are present therein, is usually dried at a temperature of from about 212 F. to about 260 F. in a drying oven, and oxidized in an oxygen-containing atmosphere such as air, at a temperature of from about 800 F. to about 1500 F. for a period of from about 1 to about 8 hours or more.

The hydrorefining process, utilizing the catalyst prepared in accordance with the method of the present invention, is effected by reacting the petroleum crude oil, or other heavy hydrocarbon mixture, and hydrogen in contact with said catalyst. The charge stock and hydrogen mixture is heated to the operating temperature within the range of from about 225 C. to about 500 C., and contacts the catalyst under an imposed pressure of from about 500 to about 5,000 p.s.i.g. The total reaction zone product effluent is passed into a suitable high pressure, low temperature separator from which a gaseous phase rich in hydrogen is removed and recycled to combine with fresh hydrocarbon charge. The remaining normally liquid product effluent is then introduced into a suitable fractionator or stripping column for the purpose of removing hydrogen sulfide and light hydrocarbons including methane, ethane, and propane. Although the normally gaseous phase from the high pressure separator may be treated for the purpose of removing the ammonia formed as a result of the destructive removal of nitrogenous compounds, a more convenient method involves the introduction of water upstream from the high pressure separator, removing said water and absorbed ammonia via suitable liquid level control means disposed in said pressure separator.

The following examples are presented in illustration of the method of this invention and are not intended as an undue limitation on the generally broad scope of the invention as set out in the appended claims. The petroleum crude oil utilized was a sour Wyoming crude having a gravity, API at 60 F., of 22.0, and contained about 2700 p.p.m. of total nitrogen, about 2.8% sulfur (calculated as the element) and 100 p.p.m. total metals (nickel and vanadium), the pentane insoluble asphaltenes portion being in an amount of about 8.37 wt. percent.

EXAMPLE I In the conventional manner, an impregnating solution was prepared by admixing a solution comprising 57.7 grams of 85% molybdic acid in 160 milliliters of water and 40 milliliters of ammonium hydroxide, with a solution comprising 27.6 grams of nickel nitrate hexahydrate in 22 milliliters of ammonium hydroxide, and diluting the resulting solution to 325 milliliters with water. 150 grams of a calcined carrier material in the form of spheres and comprising 63 weight percent alumina and 37 weight percent silica, was immersed in the solution which was thereafter evaporated to dryness over a 2-hour period in a rotary steam drier. The product was then further dried in an oven for 3 hours at 115 C. The product thus dried amounted to 253.5 grams, a gain of 19.2 grams over the solids initially employed, and attributable to water retention. The product was thereafter calcined in air at 590 C. for 1 hour. The spherical catalyst product measured about a 27% shrinkage as compared with the carrier material initially employed. The stress and strain incurred in such shrinkage is a primary cause of catalyst breakage. About 205.5 grams of catalyst product was recovered. Analysis of the physical properties disclosed an average bulk density of 0.695 gram per cubic centimeter, an average pore diameter of 108 angstroms, a surface area of 166 square meters per gram, and an average pore volume of 0.45 cubic centimeter per gram.

EXAMPLE II In this example, an impregnating solution was prepared by admixing a solution comprising 38.5 grams of 85 molybdic acid in 90 milliliters of water and 29 milliliters of ammonium hydroxide, with a solution comprising 13.5 grams of nickel nitrate hexahydrate in 11 milliliters of ammonium hydroxide, and diluting the resulting solution to only 170 milliliters with water. grams of the calcined carrier material of Example I was immersed in the solution for about 5 minutes at ambient temperature. The impregnating solution was thereafter evaporated to dryness in a drying oven at C., water vapors being purged from the oven by a stream of air. The product thus dried amounted to grams, a gain of only 3 grams over the solids initially employed, and attributable to water retention. The product was thereafter calcined in air at 590 C. for a period of one hour. In contrast to the spherical catalyst product of Example I, the product of this example measured less than about 2% shrinkage. About 135.2 grams of catalyst product was recoverd. Analysis of physical properties disclosed an average bulk density of 0.51, an average pore diameter of 99 angstroms, a surface area of 145 square meters per gram, and an average pore volume of 0.36 cubic centimeter per gram.

EXAMPLE III An impregnating solution was prepared by admixing a solution comprising 32.5 grams of 85% molybdic acid in milliliters of water and 21 milliliters of ammonium hydroxide, with a solution comprising 11.1 grams of nickel nitrate hexahydrate in 9 milliliters of ammonium hydroxide, and diluting the resulting solution to 320 milliliters with water. 100 grams of a calcined carrier material in the form of A3" spheres and comprising 68 weight percent alumina, 10 weight percent silica and 22 weight per cent boron phosphate, was immersed in the solution which was thereafter evaporated to dryness over a 2-hour period in a rotary steam drier. The product was further dried in an oven at 1215" C. for 1 hour. The product was thereafter calcined in an air atmosphere for /2 hour at 300 C., /2 hour at 400 C., /2 hour at 500 C. and 1 hour at 593 C. A crude tower bottoms characterized by an API of 12.0, 6.75% heptane-insoluble asphaltenes and 3.77% sulfur, was processed over the catalyst at a temperature of 380-425 C. under 3,000 p.s.i.g. hydrogen pressure and at a liquid hourly space velocity of 1.0. Hydrogen was recycled at the rate of 15,000 cubic feet per barrel of charge stock. The liquid product recovered analyzed 2.41 percent heptane insoluble asphaltenes (64.3% conversion), 1.04% sulfur (72.5% conversion), and had an API of 18.7.

EXAMPLE IV The crude tower bottoms described in Example III was converted to a liquid product, at the described conditions, which analyzed 2.01 heptane-insoluble asphaltenes (70.2% conversion), 0.63% sulfur (83.2% conversion), and had an API of 19.8. In this example, the catalyst was prepared in accordance with the method of this invention. The catalyst was prepared as in Example 'III with the exception that the impregnating solution was diluted to only 260 milliliters. The carrier material was immersed in the solution for about 10-15 minutes at ambient temperature. The impregnating solution was thereafter evaporated to dryness in a drying oven at 125 C., Water vapors being purged from the oven by a stream of air. The product was thereafter calcined in air at the conditions of Example I-II. 108.9 grams of oxidized catalyst was recovered.

I claim as my invention:

1. A method of preparing a hydrorefining catalyst which comprises impregnating a refractory inorganic oxide carrier material in aqueous solution of a soluble compound of a metal or Groups VI-B and VIII, substantially immediately thereafter effecting a rapid evaporation of water from the resulting composite at a temperature up to about 125 C. and at conditions to remove water vapors from contact with said composite substantially immediate ly as formed, said water removal conditions including continuously sweeping said composite with a flow of dry gas, and calcining the resulting catalyst composite.

2. The method of claim 1 further characterized in that said refractory inorganic oxide is a composite of alumina and silica.

3. The method of claim 2 further characterized in that said aqueous solution is a common solution of a soluble compound of molybdenum and a soluble compound of nickel.

4. The method of claim 3 further characterized in that said composite of alumina and silica comprises alumina and at least an equimolar amount composited with silica.

5. The method of claim 4 further characterized in that said common solution comprises a soluble compound of molybdenum and a soluble compound of nickel in a concentration suificient to insure a catalyst composite com,- prising from about 5 weight percent to about 20 weight percent molybdenum and from about 0.1 Weight percent to about 10 Weight percent nickel.

References Cited UNITED STATES PATENTS DANIEL E. WYMAN, Primary Examiner C. F. DEES, Assistant Examiner US. Cl. X.R. 2524S8, 46 5