GB979564A - Production of titanium oxide - Google Patents

Abstract

In the production of TiO2 by vapour phase oxidation of titanium tetrahalide TiX4, particularly TiCL4, a stream containing O2 and a stream containing TiX4 vapour are projected into the reaction zone, the linear velocity of the stream containing O2 being greater than that of the stream containing TiX4, and product TiO2 and Cl2 are withdrawn from the reaction zone in the same linear direction as the stream containing oxygen is projected into the reaction zone. If VO is the linear velocity of the oxygen-containing stream, VT is the component of linear velocity of the TiX4 <PICT:0979564/C1/1> <PICT:0979564/C1/2> <PICT:0979564/C1/3> <PICT:0979564/C1/4> stream along the axis of oxygen flow and do is the diameter of the oxygen-containing stream, within 0.5 seconds of contact with the TiX4, the formula <FORM:0979564/C1/1> should have a numerical value greater than 50, preferably greater than 300. An inert gas stream, for example N2, CO2, recycled produce gases, A, or particularly Cl2 may also be projected into the reaction zone having velocity VI such that <FORM:0979564/C1/2> is greater than 50, and preferably such that VI< 1/2 VO. Suitable reactors are illustrated in Figs. 1, 3, 4. Fig. 1 shows a furnace A1 having a burner A fitted in its upper part and an outlet 7 at its base. Burner A consists of concentric tubes 2, 3, 4 through which are introduced TiCl4, Cl2 and O2 respectively at feed rates correlated with the tube diameters to give a positive number between 300 and 20,000 as determined by the above formula. Product TiO2 and Cl2 formed in zone 30 are withdrawn in the direction indicated by the arrow from outlet 7. Fig. 3 depicts burner B constructed of concentric tubes 10, 11, 12 through which are passed TiCl4, Cl2, O2 respectively. The tubes differ in length so that O2 jetting past slot 16 is circumscribed by inert gas, and this stream when passing slot 17 is enveloped by TiCl4, the three streams retaining their identity as they are projected into the reaction zone. The reactant streams may also include an aluminium compound or a zirconium salt, and a silicon halide, particularly AlCl3 or ZrCl4, and SiCl4. Other suitable additives include potassium salts and organo potassium compounds; metals and metal compounds of Groups Ia, Ib, IIa, IIb, particularly Mg, Ca, Cu, Zn in the metallic vapour state, as salts, or as organometallic compounds. Fig. 4 illustrates a suitable reactor for the introduction, in separate streams, of oxygen, chlorine, chlorine + AlCl3, and TiCl4. The oxygen-containing gas stream may be pure oxygen, air, or a mixture of oxygen with the products of combustion of a combustible gas, e.g. CO. In the latter case the gas may be formed in situ before the introduction of TiX4. The temperature of the reaction zone is usually maintained between 750 DEG and 1600 DEG C. The reactants may be preheated and the temperature of the inflowing oxygen stream is the same or greater than that of the TiX4 vapour stream. It is also preferred to pass inert gas along the furnace wall during the reaction.