IE41780B1 - Hydrodesulfurization catalyst and method of manufacture and use thereof - Google Patents

Abstract

1502915 Hydrodesulphurization catalysts UOP Inc 30 June 1975 [1 July 1974] 27449/75 Heading C5E [Also in Division B1] Sulphur-containing fuel oils are hydrodesulphurized at a hydrogen pressure of 7-200 atm., a hydrogen to hydrocarbon vol. ratio of 150-10,000, a temperature of 100-450‹ C. and a LHSV of 0À5-20 using a catalyst comprising a Group VIB component (i.e. Cr, Mo or W) and a Group VIII component (e.g. Fe, Co, Ni, Pt or Pd) on a refractory carrier, wherein the catalyst has been prepared by a specified process involving partial incorporation of the active components by mixing in finely divided form with the carrier to form a dough then extruding and completion of active component incorporation by impregnation of the calcined extrudate (see Division B1). The examples describe the treatment of a vacuum gas oil of boiling range 315-565‹ C.

Description

This invention relates to the hydrodesulfurization of petroleum hydrocarbon fractions such as residual fuel oils, and to a method for the manufacture of a catalytic composite particularly adapted thereto.

Desulfurization technology is presently concerned with hydrotreating and the development of catalysts that are more selective and/or operate at less severe conditions to obviate hydrocracking of the residual fuel oil. Hydrotreating, or hydrodesulfurization, is generally effected at hydrogen pressures of 7 to 200 atm. absolute. Normally, the hydrogen is charged together with recycle hydrogen to provide about 150 to 10,000 volumes of H2 (at 15°C, 1 atm abs.) per volume of oil (at 15°C). Hydrodesulfurization temperatures are usually 100 to 45O°C, preferably 315 to 425°C.

The liquid hourly space velocity is usually 0.5 to 20 (volumes of oil at 15°C per volume of catalyst). Hydrodesulfurization catalysts preferably comprise a Group VIB metal (i.e. of the group consisting of chromium, molybdenum and tungsten), usually molybdenum, and a Group VlII metal, usually nickel or cobalt, on a refractory inorganic oxide carrier material, usually alumina.

These conventional catalysts work reasonably well, but - 2 41780 research efforts have continued to attempt to find a catalyst which would be more active than conventional catalysts.

We have now found an improvement.

According to the present invention there is provided a method of manufacturing a catalyst which comprises mixing and peptizing, to form an extrudable dough, a finely divided Group VIB metal compound, a finely divided Group VIII metal compound and a finely divided refractory inorganic oxide, said compounds being mixed in respective amounts which provide 60 to 90% of each of the Group VIB and VIII metal components of the finished catalyst; extruding said dough and drying and calcining the extrudate; impregnating the calcined extrudate with a Group VIB metal compound and a Group VIII metal compound, to provide a finished catalyst containing, on an elemental basis, 4 to 30 wt % Group VIB metal and 1 to 10 wt % Group VIII metal; and drying and calcining the impregnated extrudate in an oxidizing atmosphere.

The present invention also provides a hydrotreating process comprising treating a sulfur-containing fuel oil at a hydrogen pressure of 7 to 200 atm. abs., a hydrogen to hydrocarbon ratio of 150 to 10,000 volumes of H2 (at 15°C. 1 atm. abs.) per volume of oil (at 15°C), a temperature of 100 to 45O°C, and a liquid hourly space velocity of 0.5 to 20, in the presence of a catalyst manufactured by the method of the present invention.

In accordance with the method of this invention, a finely divided Group VIB metal compound, a finely divided Group VIII metal compound and a finely divided refractory inorganic oxide are mixed and peptized to form an extrudable dough. For convenience, all of the ingredients may be dry mixed before a peptizing agent is added. It should also be possible to dry mix some of the ingredients, add the peptizing agent, and then add the remainder of the dry ingredients.

The finely divided particles used to form the dough generally have an average diameter less than 150 microns, for example they may be particles recoverable through a 105 micron microsieve. The refractory inorganic oxide can be alumina, silica, zirconia, thoria, boria, chromia, magnesia, titania, and the like, or composites thereof such as alumina-silica, alumina-zirconia, and the like. Alumina is preferred, especially alpha-alumina monohydrate of the boehmite structure. The dry mixing operation is improved utilizing an alpha-alumina monohydrate characterized by a weight loss on ignition at 900°C of 20 to 30 wt.%. The alpha-alumina monohydrate improves the extrusion characteristics of the mixture so the mixture is readily extruded through a 0.8 to 3.2 mm orifice at a pressure of less than 35 atm.

Molybdic anhydride is a particularly suitable Group VIB metal compound, and cobalt carbonate is a particularly suitable Group VIII metal compound for dry mixing with the alpha-alumina monohydrate as herein contemplated. Other suitable Group VIB metal compounds include molybdic acid, ammonium molybdate, ammonium chromate, chromium acetate, chromous chloride, chromium nitrate and tungstic acid.

Other Group VIII metal compounds which may be employed include nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, cobaltous sulfate, ferric nitrate, ferric sulfate, platinum chloride and palladium chloride. In any case, the resulting mixture is peptized, generally by the addition of an acid. A weak acid such as formic acid, acetic acid or propionic acid may be used, although the stronger acids such as sulfuric acid, hydrochloric acid, and particularly nitric acid are preferred. Sufficient peptizing agent is blended or - 4 41780 mulled with the mixture to form an extrudable dough or pliable plastic mass.

The extrusion operation may be carried out in a conventional manner. For example, the dough may be pressured through a perforated plate by means of a rotating screw.

The extrudate may be cut into particles of desired length, prior to drying and calcining, by means of a rotating knife as the extrudate emerges from the perforated plate. Alternatively, the extrudate may be broken into particles of random length during the drying and calcining process. In any case, the extrudate is dried and calcined, drying usually being carried out at up to 120°C over 1 to 24 hours and calcinating usually being carried out at 300 to 65O°C for 2 to 4 hours in an oxidizing atmosphere such as air.

The final catalyst will contain, on an elemental basis, 4 to 30 wt % Group VIB metal and 1 to 10 wt % Group VIII metal. The co-extrusion step provides only 60 to 90% of each metal component. The remainder of the desired total metals content is added by impregnating the calcined extrudate with a Group VIB metal compound and a group VIII metal compound.

Conventional impregnation techniques may be used to impregnate the extrudate. Typically, a soluble compound of the desired metallic component is impregnated on the carrier material from an aqueous solution. The soluble compound serves as a precursor of the metallic component such that, upon subsequent heating of the impregnated carrier material at a temperature effecting decomposition of said compound, the desired metallic component is formed on the carrier. The aqueous Impregnating solution will thus comprise a soluble precursor compound of a Group VIB metal. Suitable compounds include ammonium molybdate, ammonium paramolybdate, molybdic acid, ammonium chromate, ammonium peroxychromate, chromium acetate, chromous chloride, chromium nitrate, ammonium metatungstate and tungstic acid. 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 and palladium chloride.

Impregnation can be accomplished by conventional techniques whereby the extrudate particles are soaked, dipped, suspended or otherwise immersed in the impregnating solution to absorb a soluble compound comprising the desired catalytic component. Impregnation of the Group VIB and Group VIII metal components is preferably from a common aqueous ammoniacal solution of soluble compounds thereof, for example, an ammoniacal solution of molybdic acid and cobalt nitrate. Further, the impregnation is preferably effected with a minimal volume of impregnating solution commensurate with an even distribution of the catalytic components on the calcined extrudate particles.

One preferred method involves the use of a steam-jacketed rotary dryer. The extrudate particles are immersed in the impregnating solution and tumbled therein by the rotating motion of the dryer. There should be about 0.7 to 1 volumes of extrudate per volume of impregnating solution. Evaporation of impregnating solution is expedited by applying steam to the dryer jacket and by a continuous purge of the dryer with a dry gas, suitably air or nitrogen. The impregnated particles, thus dried, are then calcined, usually at 300 to - 6 41780 65O°C, in an oxidizing (oxygen-containing) atmosphere for 1 to 8 hours or more.

The following Examples illustrate the preparation of catalysts and the improved results achieved with catalysts according to the invention.

Example I (Comparative) About 450 grams of a commercial finely divided alphaalumina monohydrate (Catapal S) was thoroughly dry mixed with 95.6 grams of a finely divided, volatile free, molybdic oxide and about 19.9 grams of finely divided cobalt carbonate. All these finely divided particles had an average diameter of less than 150 microns. Approximately 245 grams of 13 wt % nitric acid was then added to the powdered mixture in a muller, the mixture being thereby converted to a dough. The mixture was mulled for about an hour and thereafter extruded through a plate with 0.8 mm perforations. The extrudate was dried and calcined in air one hour at 400°C and for one additional hour at 59O°C.

The extruded particles, broken to an average length of about 3.2 mm contained 2.8 wt % Co and 8.7 wt % Mo.

Example II (According to the invention) I'nrsib-uil (o Mie firnsent Invention, extrudate partielnn prepared according to Example I were impregnated to introduce further molybdenum and cobalt. About 100 grams of the extrudate was impregnated with a common ammoniacal solution of molybdic acid and cobalt nitrate prepared by commingling an aqueous solution of 2.7 grams of 85% molybdic acid and 2.2 milliliters of ammonium hydroxide with an aqueous solution of 1.2 grams of cobait nitrate hexahydrate and 1.2 milliliters of ammonium hydroxide, the resulting solution being subsequently diluted to about 170 millilitres with water. - 7 41780 The extrudate particles were immersed in the impregnating solution which was then evaporated to dryness. The impregnated particles were-then calcined in air for one hour at 400°C and for an additional hour at 59O°C. The extrudate particles contained 3.5 wt % Co and 10.3 wt % Mo.

Example III. (Comparative) In this example, the cobalt and molybdenum components were incorporated in the catalyst solely by impregnation.

About 100 grams of the finely divided alpha-alumina monohydrate was mulled with about 55 grams of 13 wt % nitric acid to form a dough. The dough was then extruded, dried, and calcined in air for about one hour at 400°C and then for additional hour at 59O°C. The calcined particles were immersed in a common ammoniacal solution of molybdic aoid and cobalt nitrate hexahydrate prepared by commingling an aqueous solution of 20.7 grams of 85% molybdic acid and 12 milliliters of ammonium hydroxide with an aqueous solution of 16 grains of cobalt nitrate hexahydrate and 12 milliliters of ammonium hydroxide. Approximately 87 grams of the extrudate particles were - immersed in the impregnating solution which was then evaporated to dryness. The impregnated particles were then calcined as heretofore described. The impregnated extrudate particles contained 3.25 wt % Co and 9.4 wt % Mo.

A summary of catalyst properties and activity test results is tabulated below. Η β 0 •Η Md Κ μ 0 κ Φ 4J Φ G tn Ul rH Φ >η<Χ Μ Η £ ίχ (ϋ Φ £ +1 X Η Φ Μ U Ο· σ> co m ι—4 ID ΡΜ Ν ιη Ο <~Η Ο co σ\ CM σ ιη Γ> CM μη w Ο Η 4-) Φ Ul rH >t& r4 £ fO Φ 4J X Φ M U o3 β C 0 Ο Ή •Η 4-» Ul Φ 3 G β tn 4-» Φ X μ Φ Ch Ο £ υ η co co Ο r-4 co η ιη co Ο γΗ Ο «η Ο η· Ο ιη r-4 σ» κο CM μη Ο Η 4-» Ul Φ ί>Η«—ί r-4 ίΧ Φ £ 4J Φ Φ X α w β ο •Η ω μ •μ X φ ο υ ιη 00 m Η r-4 \£> ΓΜ Γ- CO Γ-» m • • • • • Ο Η Ο CM CO σι Ο CO σι ΙΟ CM 4-> θ’ ϋ 10 •Η 0 ω >1 β \ a Η 43 tn 0 Φ Ο μ •μ Φ 0 4J Φ ΕΗ >1 υ 01 U -μ χ tn tn β •Η tn ίη β Ο W CM χ •Η β » ε 0 +» Φ >1 υ κ Q -μ h. μ τί •rl ς£ Φ φ •ύ 44 Ul £ Φ (!) «μ ι-Η β μ £ Φ G Φ ·» 3 £ μ ω α Μ Η φ φ Φ 0 Ο φ 0 •Η •μ μ •μ U g 0 > Q 0 β Λ! Φ Φ ε Φ Φ g &> ύΡ ΜΗ φ Φ Ο Μ φ Φ μ μ μ Μ Φ •Η •Η 4) 4) 0 0 ο (X Λ (X Q £ £ ω X IX a c The above-described catalysts were evaluated with respect to the desulfurization of a vacuum gas oil boiling in the 315 to 565°C range and containing 2.6 wt 5 sulfur.

The catalyst was disposed as a fixed bed in a vertical tubular reactor maintained at 45 atm. absolute, and 399°C.

The vacuum gas oil was charged over the catalyst at 3.0 liquid hourly space velocity in admixture with 320 volumes of II2 (at 15°C, 1 atm. abs.) per volume of charge (at 15°C). The reactor effluent was separated into a liquid and a gaseous phase in a high pressure separator at 121°C, and the liquid phase treated in a stripper column for removal of light ends. The liquid stripper bottoms collected over an 8-hour period was analyzed for sulfur.

The catalyst of Example II, wherein the cobalt and molybdenum components were incorporated in the catalyst by coextrusion followed by impregnation pursuant to the method of this invention, was 55% more active than the catalyst of Example III, wherein the cobalt and molybdenum components were incorporated solely by impregnation,and 95% more active 20 than the catalyst of Example I, wherein the cobalt and molybdenum components were incorporated solely by coextrusion with the alumina.

Claims (12)

1. CLAIMS;

1. A method of manufacturing a catalyst which comprises: (a) mixing and peptizing, to form an extrudable dough, a finely divided Group VIB metal compound, a finely divided Group VIII metal compound and a finely divided refractory inorganic oxide, said compounds being mixed in respective amounts which provide SO to 90% of each of the Group VIB and VIII metal components of the finished catalyst; (b) extruding said dough and drying and calcining the extrudate; (c) impregnating the calcined extrudate with a Group VIB metal compound and a Group VIII metal compound, to provide a finished catalyst containing, on an elemental basis, 4 to 30 Wt % Group VIB metal and 1 to 10 wt % Group VIII metal; and (d) drying and calcining the impregnated extrudate in an oxidizing atmosphere.

2. The method of Claim 1 wherein the refractory inorganic oxide is alumina.

3. The method of Claim 1 wherein the refractory inorganic oxide is alpha-alumina monohydrate.

4. The method of any of Claims 1 to 3 wherein the peptizing agent is nitric acid.

5. The method of any of Claims 1 to 4 wherein the Group VIB metal compound is a compound of molybdenum. 11 41780

6. The method of.any of Claims 1 to 5 wherein the Group VIB metal compound is molybdic anhydride.

7. The method of any of Claims 1 to 6 wherein the Group VIII metal compound is a compound of cobalt.

8. The method of any of Claims 1 to 7 wherein the Group VIII metal compound is cobalt carbonate.

9. The method of any of Claims 1 to 8 wherein each calcining occurs in an oxidizing atmosphere at 300 to 65O°C.

10. A method of manufacturing a catalyst carried out substantially as described in the foregoing Example II.

11. A catalyst whenever manufactured by the method of any of Claims 1 to 10.

12. A hydrotreating process comprising treating a sulfurcontaining fuel oil at a hydrogen pressure of 7 to 200 atm. abs., a hydrogen to hydrocarbon ratio of 150 to 10,000 volumes of H 2 (at 15°C. 1 atm. abs.) per volume of oil (at 15°C), a temperature of 100 to 45O°C, and a liquid hourly space velocity of 0.5 to 20, in the presence of a catalyst manufactured by the method of any of claims 1 to 10.