Patent GB-870172-A (GB)
Title: Improvements in or relating to the preparation of active oxides
Inventor: SCHOBER ROLF
IPC: C07F5/06
Filed: 1959-03-17
Abstract: Active oxides of elements which form complex compounds of the general formula (RH)6-xMF6, where R is an amine group, M is the element, and x its valency, are prepared by reacting an oxidic compound, namely an oxide, hydroxide, carbonate, silicate, tantalate, or aluminate, of such element or elements with an organically substituted ammonium fluoride at elevated temperature, to form the above complex, and releasing an amine and water which are returned to the complex at a lower temperature to give the active oxide and the organically substituted ammonium fluoride.  The process may be carried out in aqueous or organic solution.  In a modification, the reaction is effected in organic solution and the active oxide obtained by the addition of water only.  The reaction of the oxidic compound and the fluoride may be effected under pressure.  The organically substituted ammonium fluoride may be a primary, secondary or tertary amine or one containing the nitrogen in a cyclic group. The amine has preferably a dissociation constant between 10-3 and 10-7.  To ensure that the active oxide is obtained as a fine dispersion, the fluoride should be employed in excess.  If no or only a slight excess is present a gel will normally be obtained.  Examples relate to the preparation of active alumina or silicia by dissolving alumina hydrate or quartz sand in a boiling aqueous solution of methyl ammonium fluoride, the preparation of active silica by dissolving quartz sand in a solution of ethyl ammonium fluoride in glycol, the preparation of active zirconia by dissolving zirconia in a solution of cyclohexyl ammonium fluoride in glycol and water, and the preparation of active iron oxide by dissolving iron oxide in aqueous methyl ammonium fluoride under pressure.  Reference is also made to the preparation of active oxides of beryllium, gallium, germanium, tin, titanium, hafnium, tantalum, niobium, and chromium.ALSO:Active oxides, that is, oxides or mixtures of oxides in a fine state of subdivision and large surface area, of elements which form complex compounds of the general formula (RH)6-x.MF6, where R is an amine group, M is the element, and x is the valency of the element, are prepared by reacting an oxidic compound, namely, oxides, hydroxides, carbonates, silicates, tantalates, and aluminates, of such element or elements, with an organically substituted ammonium fluoride at elevated temperature, thereby releasing an amine and water, and forming the above complex, and thereafter returning the released amine and water to the complex at a lower temperature, thereby forming the active oxide, which is separated, and simultaneously recovering the organically substituted ammonium fluoride, which is reused to prepare further active oxide. The process may be carried out in aqueous or organic solution.  In a modification of the process the reaction is carried out in organic solution and the active oxide is prepared by the addition of water only.  The reaction of the oxidic compound with the organically substituted ammonium fluoride may be effected under pressure.  The organically substituted ammonium fluoride may be a primary, secondary, or tertiary amine or an amine containing the nitrogen in a cyclic group.  Preferably the amine has a dissociation constant between 10-3 and 107.  To ensure that the active oxide is obtained as a fine dispersion, the fluoride should be employed in excess.  If no or only a slight excess is present a gel will normally be obtained. Examples relate to the preparation of active alumina or silica by dissolving aluminium hydrate or quartz sand in a boiling aqueous solution of methyl ammonium fluoride, the preparation of active silica by dissolving quartz sand in a solution of ethyl ammonium fluoride in glycol, the preparation of active zirconia by dissolving zirconia in a solution of cyclohexyl ammonium fluoride in glycol and water, and the preparation of active iron oxide by dissolving iron oxide in aqueous methyl ammonium fluoride under pressure.  Reference is also made to the preparation of active oxides of beryllium, gallium, germanium, tin, titanium, hafnium, tantalum, niobium, and chromium.