GB391322A - Methods of producing active silicic acid or active mixed gels of silicic acid with metal hydroxides or metal oxides, or mixed gels of silicic acid with active carbon - Google Patents

Abstract

In the manufacture of active silicic acid or active mixed gels of silicic acid with metal oxides or hydroxides or mixed gels of silicic acid with active carbon by known processes, loose fibres of the kind possessing capillaries or leaving capillaries behind on heating are added to the components of the reaction or to the reaction mixture, at any stage before the drying of the gel, to the extent of 0,1 to 15 per cent by weight of the dry silicic acid. The artificially-produced capillaries facilitate the adsorption and the driving-off of substances or gases adsorbed. If fibres of the kind embodying capillaries are employed, for example, animal hair, the drying temperature need not be sufficient to char or to burn the fibres. If fibres such as cotton, artificial silk or wood are employed, the drying temperature should be sufficient to burn or char the fibres, or a hot current of air may be employed, either during or after drying p for this purpose. When the gel is prepared by precipitation from aqueous solutions the fibres may be added before, during or after precipitation, and can also be added to the gel after separation from the liquid or when the gel is partly dried. A portion of the fibres may be added at an earlier stage and the remainder at a later stage. When employing animal hair, it should preferably be boiled with water before admixture. According to an example, a water-glass solution, with which is admixed animal hair of a length depending on the required size of the dried gel, is stirred with a dilute hydrochloric acid solution. The weakly alkaline sol produced eventually coagulates to a gel which is filtered, washed, if desired, shaped, dried and heated.ALSO:In the manufacture of active silicic acid or active mixed gels of silicic acid with metal oxides or hydroxides or mixed gels of silicic acid with active carbon by known processes, loose fibres of the kind possessing capillaries or leaving capillaries behind on heating are added to the components of the reaction or to the reaction mixture, at any stage before the drying of the gel, to the extent of 0,1 to 15 per cent by weight of the dry silicic acid. The artificially produced capillaries facilitate the adsorption and the driving off of substances or gases absorbed. If fibres of the kind embodying capillaries are employed, for example animal hair, the drying temperature need not be sufficient to char or to burn the fibres. If fibres such as cotton, artificial silk or wood are employed, the drying temperature should be sufficient to burn or char the fibres, or a hot current of air may be employed either during or after drying for this purpose. When the gel is prepared by precipitation from aqueous solutions the fibres may be added before, during or after precipitation and can also be added to the gel after separation from the liquid or when the gel is partly dried. A portion of the fibres may be added at an earlier stage and the remainder at a later stage. When employing animal hair, it should preferably be boiled with water before admixture.