ES352710A1 - Catalyst preparation - Google Patents

Abstract

A supported metal-containing catalyst is prepared by a process which comprises pre- 'paring an aqueous medium comprising a soluble compound of a catalytic metal in solution and particulate carrier material in the solid phase e.g. alumina, titania or, silica, which compound forms a precipitate of catalytically-active material or precursor therefor on reaction with a hydroxyl ion, agitating the medium thereby to obtain a suspension of the carrier material, making available hydroxyl ions in the agitated suspension by an in situ generation of hydroxyl ions thereby to form a precipitate of catalytically-active material or precursor therefor, the rate at which the hydroxyl ions are made available being controlled at such a low rate that the precipitate is formed on the carrier material and not in the body of the aqueous medium and the agitation being controlled so that the concentration of hydroxyl ions is uniform throughout the aqueous medium thereby to provide a homogeneous distribution of precipitate in finely divided form on the carrier material, separating carrier material loaded with precipitate from the aqueous medium, and drying the separated carrier material loaded with precipitate to provide a catalyst which subsequently may be moulded to form artefacts having a predetermined shape and size. The artefacts may include thermostable filler material. The catalyst and/or the artefacts moulded therefrom may be calcined alternatively or subsequently, the catalyst and/or the artefacts moulded therefrom may be heated under reducing conditions, for example in a stream of hydrogen. The catalytically-active material supported by the carrier material preferably has a particle size not greater than 50 the weight ratio of catalytically-active material to carrier material may be between 0À1 to 1 and 3 to 1 and preferably is not more than 2 to 1. The hydroxyl ions may be made available by the provision in the aqueous medium of urea and/or nitrite ions, which nitrite ions may be provided by the use of a nitrite as the soluble compound of the catalytic metal alternatively, such soluble compound may be a chloride, a nitrate or a sulphate. The carrier material, preferably has a specific surface area of about 150 m.2/g. The catalytic metal may be tin, lead, vanadium, antimony, bismuth, chromium, uranium, manganese, iron, cobalt or nickel and may be present in the form of elemental metal or an oxide thereof the catalyst may contain two or more catalytic metals or oxides thereof which may be in the form of a salt, for example a vanadate, a molybdate or a tungstate. Catalysts referred to include silica-elemental nickel obtained by reduction, for example with hydrogen, of a silicanickel oxide catalyst precursor prepared from an aqueous medium containing silica, nickel nitrate, sodium nitrite and urea (Example 1) or silica, nickel nitrate and urea (Example 2) or silica, nickel nitrate and sodium nitrite (Example 10) silica-bismuth oxide prepared from an aqueous medium containing silica, bismuth nitrate and urea (Example 3) silica-cobalt molybdate prepared from an aqueous medium containing silica, cobalt nitrate, ammonium molybdate and urea (Example 4) silicachromium oxide prepared from an aqueous medium containing silica, chromium nitrate and urea (Example 5) silica-stannic oxide prepared from an aqueous medium containing silica, stannic chloride and urea (Example 6) silicaplatinum prepared from an aqueous medium containing silica chloroplatinic acid and urea (Example 7) titania-nickel oxide prepared from an aqueous medium containing titania, nickel nitrate and urea (Example 8) and silica-ferric oxide prepared from an aqueous medium containing silica, ferrous chloride and urea (Example 9). The silica used is a commerciallyavailable highly-porous silica obtained from silicon tetrachloride by flame hydrolysis.