| 摘要 |
1,170,663. Silver catalysts. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 15 Feb., 1968 [22 March, 1967; 30 Oct., 1967], Nos. 13486/67 and 49261/67. Heading B1E. [Also in Division C2] A silver containing catalyst is prepared by impregnating a particulate solid porous substance with a solution of a reducible silver compound and subsequently evaporating the solvent by intimately contacting the particulate porous solid substance with a treated gaseous atmosphere under such conditions that at least 80% by volume of the liquid adsorbed by the solid porous substance is evaporated in at most 900 seconds and reduction occurs simultaneously. In a modification, the particles to be dried may fall through a heated and fluidized bed of an inert particulate solid the fluidized state of the particles being maintained by the upward stream of the drying gas. Suitable carrier materials include pumice, ceramics, SiC, SiO 2 , Al 2 O 3 and SiO 3 -Al 2 O 3 . The silver catalysts may contain promoters which include compounds of alkali or alkaline earth metals in the form of their oxides, or precursors such as hydroxides, carbonates, nitrates, acetates, &c. The silver compound is reduced to the metal or the oxide in the "shock-drying" treatment by heat or by the presence of a reducing agent. Most suitable reducing agents are polyhydric alcohols. The reducing agents and promoters are preferably impregnated during or prior to the drying treatment. Shock-drying temperatures are generally in the range 200‹ to 900‹C. The impregnated catalyst particles may have the form of pellets, spheres, rings or cylinders. Various pore volumes and surface areas are specified throughout. |
