Patent GB-144663-A (GB)
Title: Process for modifying the physical characteristics of solid substances produced by chemical reactions
IPC: C01F7/32
Filed: 1920-06-08
Abstract: Solid substances which are to be employed in chemical processes, or as catalytic substances or carriers, or absorption media &c., are prepared in graduated degrees of dispersion by selecting an initial solid reagent according to the concentration in the space-net of those atoms or groups of atoms that characterize the initial material and the final product, which concentration corresponds to the degree of dispersion desired, and then by reacting on this selected initial material with a liquid, dissolved or gaseous reagent; the said product of the reaction constitutes at the commencement a layer on the surface of the initial material, and thereafter complete transformation is effected without material change of volume-that is, without variation in concentration of the pertinent atoms or groups of atoms-by diffusion through this layer.  The space-net structure of the initial substance may be modified by a preliminary treatment, for example, in the case of salts containing water of crystallization, by a preliminary dehydration.  The degree of dispersion is also affected by variation in the concentration of the liquid or gaseous reagent, the temperature of the reaction, by the addition of substances that do not participate in the reaction, and by recovering the by-products of the reaction as soon as they are produced.  Substances to which the process is applicable are-metals, metal oxides, carbonates, phosphates, &c., particularly the oxides and hydroxides of aluminium, chromium, nickel, iron, and the rare earths.  The process is particularly applicable to the preparation of carriers for metal and oxide catalysts, which may be precipitated on to the former during the process of formation, or may be subsequently incorporated therewith; and to the preparation of metal catalysts in varying grades of dispersion by the reduction of suitable solid substances or by subsequent reduction of previously prepared oxides.  In examples, aluminium hydroxide is prepared by adding to cold ammonia solution crystallized ammonium alum and aluminium sulphite, the former giving a more finely divided form of hydroxide; aluminium hydroxide is prepared by treating ammonium alum with concentrated and dilute solutions of ammonia, the hydroxide produced by the former being the more finely divided, but different in its properties from that obtained according to the first example; aluminium oxides of comparable dissimilar properties are obtained on igniting these hydroxides; hydroxides of different properties are obtained if the ammonium alum and aluminium sulphate is subjected to a preliminary dehydration, and the oxides obtained from these show a much stronger catalytic activity in decomposing alcohol for the production of ethylene; a nickel catalyst is prepared by carefully drying at 150 DEG  C. crystallized nickel sulphate, treating the powdered dehydrated sulphate with a 10 per cent solution of carbonate of soda, dehydrating the washed hydroxide at 200 DEG  C., and finally reducing in hydrogen at 400 DEG  C.ALSO:The catalytic decomposition of alcohol is carried out in the presence of an aluminium hydroxide catalyst obtained by treating dehydrated alum with ammonia solution.ALSO:Metal oxides, carbonates, phosphates, &c., particularly the oxides and hydroxides of aluminium, chromium, nickel, iron, and the rare earths are prepared in graduated degrees of dispersion by selecting an initial solid reagent according to the concentration in the space-net of those atoms or groups of atoms that characterize the initial material and the final product, which concentration corresponds to the degree of dispersion desired, and then by reacting in this selected initial material with a liquid, dissolved or gaseous reagent; the solid product of the reaction constitutes at the commencement a layer on the surface of the initial material, and thereafter complete transformation is effected without material change of volume, that is, without variation in concentration of the pertinent atoms or groups of atoms, by diffusion through this layer. The space-net structure of the initial substance may be modified by a preliminary treatment, for example, in the case of salts containing water of crystallization by a preliminary dehydration. The degree of dispersion is also affected by variation in the concentration of the liquid or gaseous reagent, and the temperature of the reaction, by the addition of substances that do not participate in the reaction, and by removing the by-products of the reaction, as soon as they are produced.  Substances to which the process is applicable are metals, metal oxides, carbonates phosphates, &c., particularly the oxides and hydroxides of aluminium, chromium, nickel, iron, and the rare earths. The process is particularly applicable to the preparation of carriers for metal oxide catalysts, which may be precipitated on to the former during the process of formation, or may be subsequently incorporated therewith.  In examples, aluminium hydroxide is prepared by adding to cold ammonia solution crystallized ammonium alum and aluminium sulphate, the former giving a more finely divided form of hydroxide; aluminium hydroxide is prepared by treating ammonium alum with concentrated and dilute solutions of ammonia, the hydroxide produced by the former being the more finely divided, but different in its properties from that obtained according to the first example; aluminium oxides of comparable dissimilar properties are obtained on igniting these hydroxides; hydroxides of different properties are obtained if the ammonium alum and aluminium sulphate is subjected to a preliminary dehydration, and the oxides obtained from these show a much stronger catalytic activity in decomposing alcohol.