Patent GB-764082-A (GB)
Title: Improvements in or relating to the manufacture of metal oxides
Inventor: LANE FRANK WESLEY
IPC: C01G23/07
Filed: 1953-08-04
Abstract: <PICT:0764082/III/1> <PICT:0764082/III/2> In the vapour phase oxidation of volatile metal halides the halogen component of which has an atomic number greater than 9 at temperatures of above 700 DEG C., metal oxide scale deposition and build-up upon the surfaces of inlets to the reactor employed is prevented by flowing a cooling fluid about said inlets and out of contact with the reactants to maintain the internal wall surfaces of said inlets which come into contact with the halide and/or oxidizing gas, at a temperature below said oxidation temperature but above the vaporization temperature of the halide reactant. The chlorides, bromides and iodides of titanium, iron, zirconium, aluminium, chromium, vanadium, zinc, tin, tungsten, antimony, niobium and tantalum are referred to, particular reference being made to titanium and iron and to co-oxidation of aluminium chloride with titanium tetrachloride.  For example, in a titanium tetrachloride oxidation using a fused silica jet, the inlets and reactor walls are maintained at temperatures below 800 DEG C., preferably below 700 DEG C. and with a nickel jet at from about 140 to 325 DEG C., the reaction temperature being between 900 and 1350 DEG C., preferably 900 to 1200 DEG C.; in ferric chloride oxidations, reactor inlet and wall temperatures of not below 300 DEG C., and preferably from about 300 DEG C. to 500 DEG C., are resorted to. Suitable oxidization gases are oxygen, oxygen-enriched air, and oxygen-enriched air with an inert gas.  The reactants may be preheated to 800 to 1000 DEG C.  Batch or continuous operation may be used.  With particular reference to the production of titanium dioxide, the Specification refers to quenching below 600 DEG C. by dispersing cold, inert, finely divided refractor solids e.g. silica therein; to the addition of small amounts, i.e. 0.05 to 10 per cent, preferably 0.1 to 5 per cent by volume of water vapour; and to the use of small amounts i.e. 0.05 to 10 per cent fo aluminium trichloride with the titanium tetrachloride to produce a modified titanium dioxide having a neutral pH.  After collection, a titanium dioxide product may be calcined to remove chlorine.  Titanium tetrachloride and ferric chloride for the production of oxides according to the invention may be obtained by chlorinating a titaniferous material such as ilmenite, rutile, or a titanium dioxide concentrate at from 600 DEG  to 1100 DEG C. in the presence of a solid or gaseous reducing agent such as carbon, charcoal and coal, and thereafter fractionally distilling the mixed chlorides reaction product to recover the desired titanium or ferric chloride in pure state.  One suitable apparatus is shown in Fig. 1 in which 1 is a tubular conduit through which one reactant is passed into reaction zone 5, and a second conduit 7 having an inlet 8 for the other reactant is situated concentrically around it.  The walls of the conduits 1 and 7 may be constructed as shown so that a bank or banks of cooling coils e.g. for water, 111 may be incorporated therein.  In the apparatus shown in Fig. 2, open ended conduits 13 and 14 are disposed as shown to form a narrow peripheral slot 22 through which the gaseous metal halide passes as a relatively thin sheet or stream at a velocity about 15-40 times the mass velocity of the oxidizing gas into the oxidizing gas stream.  The halide is passed through conduits 24 into an annular chamber preferably lined with silica, or other corrosion resistant material, and thence passes out through the slots 22.  A fluid coolant passes into passages 30 and 31 from conduits 32 and 33 and passes out through conduits 34 and 35 respectively, thus cooling the walls 37 and 38 adjacent the mixing and reaction zones.  Suitable materials for the cooling coils or jackets include nickel, copper, silver, aluminium, magnesium, platinum, stainless steel and corrosion-resistant alloys.  The reactors are preferably constructed of corrosion resistant metals or alloys and are adapted to be lined, if desired, with a ceramic or refractory material such as silica, magnesia or porcelain.  Suitable cooling fluids include in addition to water, glycerine, alcohol, oils such as various well-known petroleum and lubricating oils, fused salts, and steam.  A liquid cooling medium may be sprayed on to and over the exterior surfaces of the inlet ducts and reactor walls or flowed as a thin sheet or stream over the surfaces of the conductor metal or jacket on the other side of the surfaces over which the reactant gases flow.  If desired the reactant inlets may be independently cooled.  Heat exchange by using the hot coolant to partly pre-heat the reactants and recirculating said coolant, may be employed.  Specification 757,703 is referred to.