GB764083A - Improvements in or relating to the production of metal oxides - Google Patents

Abstract

In the decomposition of a vaporized metal chloride, bromide or iodide with an oxidizing gas to form the corresponding oxide, the decomposition is effected within a reaction zone provided with a porous refractory wall which is cooled and maintained free from scale on the inside thereof by forcing a normally gaseous fluid in the liquid state, which is inert towards the reactants and the reaction products under the reaction conditions, into and through the wall for vaporization on the surfaces thereof. An examplary apparatus is shown in the Figure wherein an oxygen containing gas is fed through line 4 to flow through a vertical pipe 3, and titanium tetrachloride, for example, to be decomposed is fed from line 10 to a chamber 12 surrounding the tube 3 and <PICT:0764083/III/1> from which the titanium tetrachloride enters the oxygen flowing through the tube 3 through a slotted jet 13. The reactant inlets are contained in a furnace 1 which may be heated or insulated. The mixture of reactants passes into the main reactor 6 which is provided with porous walls 7 about which is a jacket 15 to which the liquid shielding fluid is fed; the reaction products are removed at 5. The porous wall may be made of aluminium oxide, zirconium dioxide, porous carbon or graphite, porcelain, silica, or porous metals such as nickel, steel, platinum or tantalum having in preference a pore diameter of less than 250 microns. Suitable shielding fluids are liquid chlorine, nitrogen, carbon dioxide and carbonyl chloride. Metal oxides which may be formed include those of iron, titanium, silicon and aluminium the chlorides, bromides or iodides of which are reacted with oxygen, air preferably humidified or steam. According to a typical example titanium tetrachloride pre-heated to 1000 DEG C. and oxygen at the same temperature containing added water vapour are reacted at approximately 1300 DEG C. and liquid chlorine is passed through the porous reactor wall thereby maintaining the wall temperature not higher than 300 DEG C. The preferred retention time for the titanium dioxide formed is from 0.1 to 5 seconds. If desired only the upper portion of the reaction space 6, where scale decomposition is likely to be most, may be made of porous material and the lower section made of solid nickel for example, surrounded by a cooling jacket. In addition the reactor inlet jets may be formed of porous refractory material and the normally gaseous fluid in the liquid state may be flowed or diffused through these surfaces in order to prevent scale decomposition. Specifications 757,703 and 764,082 are referred to.