Method for preparing multi-metal catalysts

摘要

PCT No. PCT/FR91/00969 Sec. 371 Date Oct. 13, 1992 Sec. 102(e) Date Oct. 13, 1992 PCT Filed Dec. 4, 1991 PCT Pub. No. WO92/11086 PCT Pub. Date Jul. 9, 1992.A method for preparing multi-metal catalysts including an active phase consisting of at least two metals, A and B, which are selected from groups VIII and IB of the periodic table, and a porous support. According to the method: firstly, at least a part of the porous support is impregnated with at least one precursor of metal A; secondly, activation is performed in a neutral or oxidizing atmosphere at a temperature of 120 DEG -800 DEG C. whereafter a treatment is carried out in a reduction medium at a temperature of 0 DEG -800 DEG C.; thirdly, at least a part of the support which was previously impregnated with the precursor of metal A is impregnated with at least one precursor of metal B; and fourthly, activation is performed in a neutral or oxidizing atmosphere at a temperature of 120 DEG -800 DEG C. The catalysts thereby obtained have improved stability, particularly when subjected to high temperatures, such as when they are used as post-combustion catalysts for exhaust gases from internal combustion engines, in which case metal A is platinum or palladium and metal B is platinum, palladium or rhodium, with the proviso that B is not the same as A.