Abstract: A catalyst comprising at least one porous support, at least some platinum, and at least a second group VIII metal which is different from platinum and iridium, said catalyst having been prepared in accordance with a process comprising a) impregnation of the support with at least one solution containing a platinum precursor, b) activation in a neutral or oxidizing atmosphere, at a temperature of between 120 and 800° C., c) activation in a reducing medium, at a temperature of between 0 and 800° C., d1) impregnation with an aqueous solution and d2) treatment with at least one hydrogen donor compound, at a temperature of less than 200° C., e) the impregnation of the support, which has already been impregnated with the platinum, with at least one solution containing a precursor of said second group VIII metal, and f) activation in a neutral, reducing, or oxidizing atmosphere, at a temperature of between 100 and 800° C.

Abstract: A method for treating/purification a gas containing nitrogen oxides (NOx) includes conveying same through a NOx trap containing a composition based on a catalyst for oxidizing NOx into NO2 and a compound based on zirconium oxide and praseodymium oxide in a proportion of praseodymium oxide ranging from 5 wt. % to 50 wt. % of oxide; such compound may further include cerium oxide and the subject process is useful for treating the exhaust gas of a Diesel or lean mixture gasoline internal combustion engine.

Abstract: A description is given of a catalyst comprising at least one porous support, at least some platinum, and at least a second group VIII metal which is different from platinum and iridium, said catalyst having been prepared in accordance with a process comprising a) impregnation of the support with at least one solution containing a platinum precursor, b) activation in a neutral or oxidising atmosphere, at a temperature of between 120 and 800° C., c) activation in a reducing medium, at a temperature of between 0 and 800° C., d1) impregnation with an aqueous solution and d2) treatment with at least one hydrogen donor compound, at a temperature of less than 200° C., e) the impregnation of the support, which has already been impregnated with the platinum, with at least one solution containing a precursor of said second group VIII metal, and f) activation in a neutral, reducing, or oxidising atmosphere, at a temperature of between 100 and 800° C.

Abstract: 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.degree.-800.degree. C. whereafter a treatment is carried out in a reduction medium at a temperature of 0.degree.-800.degree. 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.degree.-800.degree. C.