| 摘要 |
Solid sol particles having a surface area of at least 100 m<2>/g have a surface coating of a metal or a sparingly soluble metal compound, in particular a catalytically active substance, and are optionally coherent as aggregates. The solid surface-coated sol particles are obtained by preparing a liquid-borne sol of carrier particles having a surface area accessible to the liquid of at least 100 m<2>/g, preferably 100-1000 m<2>/g, and by dissolving a soluble metal compound in the sol and precipitating it thereform on the surface of the carrier particles. The soluble compound may be one component (anionic or cationic) of the sparingly soluble metal compound that is dissolved in a very low concentration in the sol, the other component of the sparingly soluble metal compound being supplied at a supply rate which allows preferential adsorption or attraction of the precipitating sparingly soluble compound on and against, respectively, the sol particles, instead of formation of crystal nuclei and precipitation of the sparingly soluble metal compound in the liquid phase of the sol. A surface coating of metal on the carrier particles is achieved by first precipitating the metal thereon as a reducible sparingly soluble metal compound which is thereafter reduced to metal. Alternatively, a soluble compound of the desired metal can be dissolved in the sol in order that this should adsorb or attract the metal-containing ion or molecule of the compounds, whereupon these ions or molecules are directly reduced to metal. A liquid-borne sol of solid carrier particles with a surface coating of catalytically active metal or metal compound or a precursor thereof is used for producing a catalyst by spray drying or for producing a catalyst mass by coating the surface of a catalyst support with the surface-coated solid carrier particles. |
