GB756497A - Recovery of titanium tetrachloride by adsorption - Google Patents

Abstract

Titanium tetrachloride is separated and recovered from gas mixtures containing 1-11 per cent by weight thereof by contacting said mixture with a solid adsorbent under anhydrous conditions and subjecting the adsorbent to heat treatment under anhydrous conditions to recover the adsorbed titanium tetrachloride and reactivate the adsorbent. Adsorption may take place, e.g. at 20 DEG C. in one or more towers packed with a suitable adsorbent such as carbon, charcoal, bone char, alumina, silica, titania, activated clays, or bauxite. The adsorbent may be desorbed by direct heating, e.g. in a distilling vessel at below 600 DEG C., e.g. 350 DEG C., or by directly contacting it with a hot gas, non-reactive with the titanium tetrachloride at the desorption temperature, e.g. with titanium tetrachloride itself at 300-600 DEG C. preferably 500 DEG C. with a chlorinating gas, with nitrogen, or with a stream of dry oxygen or air at a temperature, e.g. 200 DEG C. below the oxidation temperature of titanium tetrachloride, and also of carbon, if the latter is the adsorbent used; the resultant mixture can then be used for vapour phase oxidation. Alternatively, the description may comprise a first heating, e.g. with superheated titanium tetrachloride to remove a portion of the product followed by treatment with a hot, non-reactive gas, e.g. chlorinating or oxidizing gas. The bed of adsorbent may be cooled by water jackets or cooling coils if desired, and a pressure up to 200 lbs./sq. in. may be applied during adsorbtion; during desorption a reduced pressure may be applied. In order to preserve the adsorbent it is generally preferred to desorb only 30-90 per cent of the adsorbed tetrachloride. Examples are given. The process may most usefully be applied (1) to the removal of titanium tetrachloride from the gases produced when a titanium bearing material is treated with 30-100 per cent Cl2 at 600-1100 DEG C. in the presence of carbonaceous material, by condensing the main product at -10 to +30 DEG C. by conventional means, adsorbing the tail gas, desorbing it by heating at 100-400 DEG C., and recycling to the chlorination or condensation stages (chlorination with chlorine at 800-1350 DEG C. is also mentioned), (2) to recovery of titanium tetrachloride from the tail gases resulting from vapour phase oxidation or hydrolysis of titanium tetrachloride, (3) in a process for producing titanium tetrachloride by chlorinating titaniferous materials wherein the chlorinating gas is used before employment as the desorbing gas, e.g. at 300 DEG C., thus recycling the desorbed product.