NO752379L - - Google Patents

Description

The present invention relates to the hydrodesulphurisation of petroleum hydrocarbon fractions such as residual oils, and a method for the production of a catalytic material particularly suitable for this.

Desulphurization technology is currently concentrated on hydrotreating and the development of catalysts that are more selective and/or operate under less stringent conditions to prevent hydro-cracking of the residual oil. Hydrotreatment or hydrodesulphurisation is generally carried out at a hydrogen pressure of from 7 to 200 ata. Normally, the hydrogen is fed together with recycled hydrogen to provide approx. 150 - 1000 volumes H2 at 15°C, 1 ata per volume of oil at 15°C. Hydrodesulfurization temperatures are usually 100 - 450°C, preferably 315 - 425°C. The fluid space velocity is usually approx. 0.5 - 20 volumes of oil at 15°C per volume catalyst. Hydrodesulfurization catalysts preferably comprise a metal from group VIB, usually molybdenum, and a metal from group VIII, usually nickel or cobalt, on a refractory inorganic oxide support material, usually aluminum oxide.

These conventional catalysts work well, but research work continues to find a catalyst that will be more active than conventional catalysts.

The present invention provides a method for the production of a catalyst which comprises mixing and peptizing to form an extrudable dough of a finely divided metal compound of group VIB > a metal compound of group VIII and a poorly melting inorganic oxide, which compounds provide approx. 60 - 90% of the group VIB and VIII components in the finished catalyst, after which the dough is extruded and dried and the extrudate is calcined, after which the calcined extrudate is impregnated with a metal compound from group VIB and a metal compound from group VIII to give a finished catalyst containing element base 4 - 30% by weight group VIB metal, and 1 - 10% by weight group VIII metal, after which the impregnated extrudate is dried and calcined in an oxidizing atmosphere.

The invention further relates to a hydrotreatment process comprising treatment of a sulfur-containing fuel oil at a hydrogen pressure of 7 - 200 ata, a hydrogen to hydrocarbon ratio of 150 - 10,000 volumes H2 at 15°C, 1 ata per volume of oil at 15°C, a temperature of lOO - 450°C, and a liquid space velocity of 0.5 -

20, which process is characterized by the use of a catalyst produced according to the method according to the invention.

According to the present method, a finely divided metal compound from group VIB, a metal compound from group VIII and a difficult-to-melt inorganic oxide are mixed and peptized to form an extrudable dough. Appropriately, all components can be dried before a peptizing agent is added. It is also possible to dry mix several of the ingredients, add the peptizing agent and then add the remaining dry ingredients.

The term "finely divided" denotes particles with an average diameter of less than 150 microns, for example particles which pass through a 105 micron microsieve. The difficult-to-melt inorganic oxide can be aluminum oxide, silicon oxide, zirconium oxide, thorium oxide, boron oxide, chromium oxide, magnesium oxide, titanium dioxide and the like, or compositions thereof such as aluminum oxide-silicon oxide, aluminum oxide-zirconium oxide, and the like. Alumina is preferred, especially alpha-alumina monohydrate of boehmite structure. The dry mixing operation is improved using an alpha-aluminum oxide monohydrate which is characterized

by a weight loss on ignition at 900°C of 20 - 30% by weight. The alpha aluminum oxide monohydrate improves the extrusion properties of

the mixture so that the mixture is easily extruded through a 0.8 - 3.2 mm opening at a pressure of less than approx. 35 ata.

Molybdenum trioxide is a particularly suitable metal compound of group VIB, and cobalt carbonate is a particularly suitable metal compound of group VIII for dry mixing with the alpha aluminum oxide monohydrate considered here. Other suitable metal compounds from group VIB include molybdic acid, ammonium molybdate, ammonium chlornate, chromium dichloride, chromium nitrate, tungstic acid and similar compounds. Other metal compounds from group VIII that can be used include nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, cobalt sulfate, iron nitrate, jerry sulfate, platinum chloride, palladium chloride and the like. In each case, the resulting mixture is peptized by the addition of an acid. A weak acid such as formic acid, acetic acid or propionic acid can be used, although stronger acids such as sulfuric acid, hydrochloric acid<p>g and in particular nitric acid are preferred. Sufficient peptizing agent is mixed or ground with the mixture to form an extrudable dough or pliable plastic mass.

The extrusion operation is conventional. For example, the dough is pressed through a perforated plate using a rotating screw. The extrudate can be cut into particles of the desired length for drying and calcination by means of a rotary knife since the extrudate flows out of the perforated plate. Alternatively, the extrudate can be broken into particles of arbitrary length during the drying and calcining process. In each case, the extrudate is dried and calcined; the drying usually at up to 120°C over the course of 1 - 24 hours, and the calcination in an oxidizing atmosphere such as air at 300 - 650°C for 2 - 4 hours.

The catalyst will contain approx. 4 - 30% by weight of group VIB metal and 1 - 10% by weight of group VIII. The extrusion step provides only 60 - 90% of each metal component. The remainder of the desired total metal content is added by impregnating the calcined extrudate with a metal compound of group VIB and a metal compound of group VIII.

Conventional impregnation methods can be used to impregnate the extrudate. Typically, a soluble compound of the desired metal component is impregnated onto the support material from an aqueous solution. The soluble compound serves as a precursor for the metallic component, so that upon subsequent heating of the impregnated carrier material at a temperature which causes cleavage of the compound, the desired metal component is formed on the carrier. The aqueous impregnation solution will thus comprise a soluble precursor compound of a group VIB metal. Suitable compounds include ammonium arolybdate, ammonium paramolybdate, molybdic acid, ammonium chloronate, ammonium peroxychromate, chromium-III acetate, chromium-II chloride, chromium-III nitrate, ammonium metatungstate, tungstic acid and similar compounds. Low soluble compounds from Group VIII include nickel nitrate, nickel sulfate, nickel chloride, nickel bromide, nickel fluoride, nickel iodide, nickel acetate, nickel formate, cobalt-II nitrate, cobalt-II sulfate, cobalt-II fluoride, iron-III fluoride, iron-III bromide, iron-III nitrate, iron-III sulfate, iron-III formate, iron-III acetate, platinum chloride, chloroplatinic acid, chloropalladiuric acid, palladium chloride and similar compounds.

The impregnation can be carried out by known methods whereby the extrudate particles are exposed, dipped, suspended or otherwise immersed in the impregnation solution to absorb a soluble compound comprising the desired catalytic component. Impregnation of the group VIB and group VIII metal components takes place preferably from an ordinary aqueous ammoniacal solution of soluble compounds thereof, e.g. an ammoniacal 'solution of molybdic acid and cobalt nitrate. Furthermore, the impregnation is preferably carried out with a minimal volume of impregnation solution which corresponds to an even distribution of the catalytic components on the calcined extrudate particles.

A preferred method involves the use of a rotary dryer provided with a steam jacket. The extrudate particles are immersed in the impregnation solution and swirled around there due to the rotational movement of the dryer. There should be approx. 0.7 - 1 volume of extrudate per volume impregnation solution. Evaporation of the impregnation solution is carried out by supplying water vapor to the dryer jacket and by continuously flushing the dryer with dry gas, suitable air or nitrogen. The thus dried impregnated particles are then calcined in an oxygen-containing atmosphere by

300 - 650°C for 1 - 8 hours.or more.

Example I

450 g of commercial powdered alpha aluminum oxide monohydrate (Catapal S) was thoroughly dry mixed with 95.6 g of finely powdered molybdenum oxide free of volatile constituents and 19.9 g of powdered cobalt carbonate. About. 245 g of 13% nitric acid was then added to the powdery mixture in a mold, and the mixture was then converted into a dough. The mixture was ground approx. 1 hour and then extruded through a plate with 0.8 mm'S perforations. The extrudate was dried and calcined in air for 1 hour at 400°C, and for a further 1 hour at 590°C. The extruded

those particles cut to an average length of approx. 3.2 mm contained 2.8 wt% Co and 8.7 wt% Mo.

Example II

The extrudate particles from example I were impregnated according to the present invention. About. 100 g of the extrudate was impregnated with an ordinary ammoniacal solution of molybdic acid and cobalt nitrate prepared by mixing an aqueous solution of 2.7 g of 85% molybdic acid and 2.2 ml of ammonium hydroxide with an aqueous solution of 1.2 g of cobalt nitrate hexahydrate and 1 .2 ml of ammonium hydroxide, after which the resulting solution was then diluted to 170 ml with water. The extrudate particles were immersed in the impregnation solution which was then evaporated to dryness. The impregnated particles were then calcined in air for 1 hour at 400°C and for a further 1 hour at 590°C. The extrudate particles contained 3.5 wt% Co and 10.3 wt% Mo.

Example III

In this example, the cobalt and molybdenum components were incorporated into the catalyst only by impregnation. About. 100 g of powdered alpha aluminum oxide monohydrate was ground with 55 g of 13% by weight nitric acid to form a dough. The dough was then extruded, dried and calcined in air for 1 hour at 400°C and then for a further 1 hour at 590°C. The calcined particles were immersed in an ordinary ammoniacal solution of molybdic acid and cobalt nitrate hexahydrate prepared by treating an aqueous solution of 20.7 g of 85% molybdic acid and 12 ml of ammonium hydroxide with an aqueous solution of 16 g of cobalt nitrate hexahydrate and 12 ml of ammonium hydroxide. About. 87 g of the extrudate particles were immersed in the impregnation solution which was then evaporated to dryness. The impregnated particles were then calcined as previously described. The impregnated extrudate particles contained 3.25 wt% Co and 9.4 wt% Mo.

A summary of the catalyst properties and activity test results is given below.

The catalysts described above were assessed with regard to the desulphurisation of a vacuum gas oil which boils in the range 315-565°C and which contains 2.6% by weight of sulphur. The catalyst was placed as a stationary bed in a vertical tube-shaped reactor maintained at 45 ata and 399°C. The vacuum gas oil was fed over the catalyst at a liquid space velocity of 3.0 in mixture with 320 volumes of H at 15°C, 1 ata per volume added starting material at 15°C. The reactor effluent was separated into a liquid solid and a gas phase in a high pressure separator at 121°C, and the liquid phase was treated in a stripping column to remove light fractions. The bottom products from the liquid separator were collected over an 8-hour period and analyzed with regard to sulfur content.

The catalyst according to example II in which the cobalt and molybdenum components were incorporated into the catalyst by extrusion followed by impregnation according to the present method, was 55% more active than the catalyst according to example III in which the cobalt and molybdenum components were incorporated only by impregnation, and 95% more active than the catalyst according to example I in which the cobalt and molybdenum components were incorporated only by extrusion with aluminum oxide.

Claims (10)

1. Method for the production of a catalyst, characterized in that (a) a finely divided Group VIB metal compound, a Group VIII metal compound and a poorly fusible inorganic oxide are mixed and peptized to form an extrudable dough, in which the compounds provide 60-90% of the Group VIB and VIII constituents of the finished product catalyst, (b) the dough is extruded and dried, and the extrudate is calcined, (c) the calcined extrudate is impregnated with a Group VIB metal compound and a Group VIII metal compound to provide a finished catalyst containing, on an elemental basis, 4-30% by weight Group VIB metal and 1-10% by weight Group VIII metal, and (d) the impregnated extrudate is dried and calcined in an oxidizing atmosphere. 2. Method according to claim 1, characterized in that the poorly fusible inorganic oxide is aluminum oxide. 3. Method according to claim 1, characterized in that the difficult-to-melt inorganic oxide is alpha aluminum oxide monohydrate. 4. Method according to any one of claims 1-3, characterized in that the peptizing agent is nitric acid. 5. Method according to any one of claims 1-4, characterized in that the metal compound from group VIB is a molybdenum bond. 6. Method according to any one of claims 1-5, characterized in that the metal compound from group VIB is molybdenum anhydride (molybdenum trioxide). 7. Method according to any one of claims 1-6, characterized in that the metal compound from group VIII is a cobalt compound. 8. Method according to any one of claims 1-7, characterized in that the metal compound from group VIII is cobalt carbonate. 9. Method according to any one of claims 1-8, characterized in that the calcination takes place in an oxidizing atmosphere at 300 - 650°C. 10. Hydrotreating process comprising treatment of a sulphurous fuel oil at a hydrogen pressure of 7 - 200 ata, a hydrogen to hydrocarbon ratio of 150 to lO.OOO volumes H o at 15°C, 1 ata per volume of oil at 15°C, a temperature of 100p450°C and a liquid space velocity of 0.5 - 20, characterized in that a catalyst produced by: (a) mixing and peptizing to form an extrudable dough, of a finely divided group VIB metal compound, a group VIII metal compound and a refractory inorganic oxide, which compounds provide 60-90% of the group VIB and VIII components of the finished catalyst, (b) extruding the 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 form a finished catalyst containing, on an elemental basis, 4-30% by weight group VIB metal and 1-10% by weight group VIII metal, and (d) drying and calcining the impregnated extrudate in an oxidizing atmosphere.