PROCEDIMIENTO DE FORMACION DE DEPOSITOS SOBRE LAS SUPERFI- CIES INTERNAS DE UN MATERIAL POROSO.

摘要

Metal hydroxides are deposited on the interior surfaces of porous materials, e.g. woven cotton fabrics, sponges, bricks and ceramic fibre blankets, by contacting without precipitation of hydroxide the interior surfaces with (a) an aqueous solution of at least one metal salt from which the corresponding hydroxide may be precipitated at a pH of 1.7-12.5 and (b) a substance capable of decomposing at the pH of the solution to give ammonia with a consequent rise of the pH, and initiating the decomposition of the substance thereby raising the pH of the solution to a value such that the corresponding hydroxide of the metal is precipitated on the interior surfaces. The salt may be of copper, silver, beryllium, magnesium, calcium, zinc, cadmium, mercury, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, zirconium, thorium, tin, lead, chromium, uranium, manganese, iron, cobalt, nickel, ruthenium, rhodium, pelladium, iridium, or aluminium, aluminium oxychloride being preferred, and the substance decomposing to give ammonia may be hexamethylene tetramine, urea preferably in admixture with urease, urea orthophosphate and condensation products of aldehydes and ammonia. The aqueous solution of the metal salt and the ammonia producing substance may be mixed and the resulting solution adjusted to the desired pH and applied to the porous material which is then heated. The porous material may subsequently be heated to convert the precipitated hydroxide to the corresponding oxide or to a salt of the metal and if it is a carbonaceous material e.g. a cotton material or sponge, to burn away the substrate to form a material suitable for use as a catalyst. In the case of a ceramic blanket the metal hydroxide is deposited as discrete nodules around the fibres especially at the points of intersection of two or more fibres thus locking them together.ALSO:Metal hydroxides are deposited on the interior surfaces of porous materials, e.g. woven cotton fabrics and ceramic fibre blankets, by contacting without precipitation of hydroxide the interior surfaces with (a) an aqueous solution of at least one metal salt from which the corresponding hydroxide may be precipitated at a pH of 1.7-12.5 and (b) a substance capable of decomposing at the pH of the solution to give ammonia with a consequent rise of the pH, and initiating the decomposition of the substance thereby raising the pH of the solution to a value such that the corresponding hydroxide of the metal is precipitated on the interior surfaces. The salt may be of copper, silver, beryllium, magnesium, calcium, zinc, cadmium, mercury, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, zirconium, thorium, tin, lead, chromium, uranium, manganese, iron, cobalt, nickel, ruthenium, rhodium, pelladium, iridium, or aluminium, aluminium oxychloride being preferred. and the substance decomposing to give ammonia may be hexamethylene tetramine, urea preferably in admixture with urease, urea orthophosphate and condensation products of aldehydes and ammonia. The aqueous solution of the metal salt and the ammonia producing substance may be mixed and the resulting solution adjusted to the desired pH and applied to the porous material which is then heated. The porous material may subsequently be heated to convert the precipitated hydroxide to the corresponding oxide or to a salt of the metal and if it is a cotton material or sponge to burn away the substrate to form a material suitable for use as a catalyst. In the case of a ceramic fibre blanket the metal hydroxide is deposited as discrete nodules around the fibres especially at the points of intersection of two or more fibres thus locking them together.