CATALYST FOR CLEANING EXHAUST GASES FROM COMBUSTION ENGINES

摘要

Catalyst for purifying i.c. engine exhaust gas has an Al2O3 support of the transition series, which contains 3-70 (wt.)% CeO2, 0-20% La2O3, opt. mixed with other rare earth metal oxides, 1-20% ZrO2, 0-10% Fe2O3 and 0-20% NiO as promoter, and has an active phase of 0.02-3% Pt and/or Pd and Rh, with a ratio of Pt and/or Pd and Rh of 1:2 to 15:1, pref. 1:1 to 3:1 and opt. a wt. ratio of Pt and Pd of 10:1 to 1:5. The opt. lattice-stabilised support is impregnated with a soln. of a promoter cpd. and/or mixed with a suspension of oxides, hydroxides or carbonates of the promoter elements and heated in air at 300-900 deg.C, then impregnated with a soln. of the noble metal cpds.,dried and opt. activated in a gas contg. H2, opt. under hydrothermal conditions, at 250-1050 deg.C. The catalyst contains base metal(s), i.e. Li, K, Rb, Mg, Ca, Ba, La, Ce, Pr, Nd, Sm, Fe, Co and/or Ni, in an amt. up to 5 times the total amt. of noble metal; and is prepd. by impregnating the support contg. promoter with a soln. (A) of Pt and/or Pd cpd(s). corresp. to at least 30% of the total amt. of Pt and/or Pd, drying and activation, then impregnating with a soln. (B) contg. Rh cpd. opt. the rest of the Pt and/or Pd cpd. and base metal cpd(s)., followed by drying and activation.