Carbon monoxide and carbonyl sulfide emissions are reduced in manufacturing processes, including titanium tetrachloride production processes. Gas contaminated with CO and COS, and an oxygen-containing gas, is contacted with a suitable catalyst. The catalyst may be a metal oxide catalyst containing bismuth, cobalt and nickel, such as metal oxides containing oxides of the formula, (Bi.sub.a Co.sub.b Ni.sub.c).sub.y Mo.sub.1-y O.sub.z, where a, b and c are from 0 to 1, y is from 0.01 to 0.75 and z is from 1.125 to 4.875; a xerogel or aerogel catalyst containing Au, Rh, Ru and Co in aluminum oxide/oxyhydroxide matrices, such as those of the formula [(Au.sub.1-(w+d) Rh.sub.w Ru.sub.d).sub.e Co.sub.f AlO.sub.1.5-u (OH).sub.2u ].sub.1-(e+f), where w and d are from 0 to 1, e is from 0.001 to 0.2, f is from 0 to 0.2 and u is from 0 to 1.5; or a supported metal catalyst that contains at least one metal from the group Pd, Rh, Ru and Cu. In the latter case, the catalyst support contains alumina or carbon. A catalyst composite of Au, Rh, Ru and Cr, and cerium oxide and lanthanum oxide may also be used, such as a composites containing Au, Rh, Ru and Cr, and cerium oxide and lanthanum oxide of the formula (Au.sub.1-(w+d) Rh.sub.w Ru.sub.d).sub.e Cr.sub.f (Ce.sub.g La.sub.1-g).sub.1-(e+f) O.sub.v, where w and d are from 0 to 1, e is from 0.001 to 0.2, f is from 0 to 0.2, g is from 0 to 1 and v is from 1.1 to 2.4.