Abstract: The composition based on a discharge from an oil refining plant after a desulfurization of heavy oils in the oil refining plant using a catalyst, comprising: 80% or less of vanadium; 80% or less of molybdenum; 20% or less of nickel; 30% or less of cobalt; 99% or less of alumina; and a trace of the impurities, which is catalytically active to purify the exhaust of diesel vehicles. A filter or a washcoat made of the discharged catalyst composition alone or in combination with ordinary filtering materials or ordinary washcoat materials can be very useful for purification of smoke. In addition, a catalyst in which at least one metal of the platinum group is uniformly impregnated on the filter is quite superior to conventional ones employing alumina or titania as a washcoat in stability to both high temperature and sulfur trioxide.