Stamicarbon B.v.

Abraham Van Montfoort

Joseph J Scholten

Process for preparing high mechanical strength pure silicon dioxide suitable for demanding high-grade technical applications including the combination of steps of (a) forming a reaction mixture containing a silicon dioxide precipitate by controllably and gradually admixing with firm agitation an at most 15 weight percent aqueous solution of hexafluorosilicic acid with an about 15 to about 35 weight percent ammonium hydroxide solution at about 25.degree. C. to about 45.degree. C. until the pH is about 8.5 to about 9.2 in the thus formed mixture containing a silicon dioxide precipitate; (b) separating the silicon dioxide precipitate from the mixture; (c) washing the thus separated precipitate; and (d) calcining the thus washed precipitate at about 900.degree. C. to about 1500.degree. C. Silicon dioxide produced in accordance with the present process has better physical properties than commercially available porous alpha-alumina.

Process for preparing pure silicon dioxide having high mechanical

A process for preparing activated carbon supported catalysts by mixing an activated carbon support having acid surface groups with an aqueous solution containing one or more cations selected from the groups IB and VIII of the Periodic System of Elements as well as Zn to effect cation exchange with the acid groups on the surface of the activated carbon support, separating the cation exchanged activated carbon. Said exchanged surface cations are thereafter reduced on the carbon support in the medium which is later to be subjected to the catalyzed reaction. The surface of the activated carbon support may be oxidized to increase the number of acid groups per unit area prior to ion exchange.

Process for the preparation of supported catalysts

The invention relates to a process for preparing active noble-metal catalysts on a carbon carrier. In particular, the process comprises adsorbing a salt of the catalytically active metal onto the carbon in an aqueous medium; hydrolyzing said salt to the oxide or hydroxide, by employing a basic reagent; and reducing said oxide or hydroxide to the metal.

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Geleen, Netherlands

Abraham Van Montfoort