Abstract: The invention relates to a method for treating a gas containing nitrogen oxides (NOx), in which an NOx-reduction reaction is carried out using a nitrogen-containing reducing agent, which invention is characterized in that the catalyst used for the reduction reaction is a catalytic system containing a composition comprising zirconium, cerium and niobium in the following percentages by weight, expressed in terms of the weight of oxide: 10-50% of cerium, 5-20% of niobium and the remainder consisting of zirconium.

Abstract: A process is described for preparing cubic metallic nanoparticles, comprising: a) preparing an aqueous solution containing a source of a metal from group VIII, a reducing agent R1 and a stabilizer; b) preparing an aqueous solution containing a source of a group VIII metal and a stabilizer at a temperature strictly higher than 70° C. and less than or equal to 80° C.; c) mixing at least a portion of the aqueous solution obtained in step a) with the aqueous solution obtained in step b) to obtain, in the presence of a reducing agent R2, metallic nanoparticles in the cubic form representing at least 70% by number of the entire quantity of metallic nanoparticles which are formed; d) depositing said metallic nanoparticles derived from step c) on a support.

Abstract: The invention relates to a method for treating a gas containing nitrogen oxides (NOx), in which an NOx-reduction reaction is carried out using a nitrogen-containing reducing agent, which invention is characterized in that the catalyst used for the reduction reaction is a catalytic system containing a composition comprising zirconium, niobium in the following percentages by weight, expressed in terms of the weight of oxide: 10-50% of cerium, 5-20% of niobium and the remainder consisting of zirconium.

Abstract: A process is described for preparing cubic metallic nanoparticles, comprising: preparing an aqueous solution containing a source of a metal from group VIII, a reducing agent R1 and a stabilizer; preparing an aqueous solution containing a source of a group VIII metal and a stabilizer at a temperature strictly higher than 70° C. and less than or equal to 80° C.; mixing at least a portion of the aqueous solution obtained in step a) with the aqueous solution obtained in step b) to obtain, in the presence of a reducing agent R2, metallic nanoparticles in the cubic form representing at least 70% by number of the entire quantity of metallic nanoparticles which are formed; depositing said metallic nanoparticles derived from step c) on a support.