Abstract:
The invention relates to a composition essentially consisting of a zirconia-ceria mixed oxide, with a zirconia content of at least 40 wt. % and, after 4 hours of calcination at 1000°C, a specific surface area of at least 25 m 2 /g and a quantity of mobile oxygen between 200°C and 400°C of at least 0.5 ml O 2 /g. Said composition is produced using a method wherein a mixture of cerium and zirconium compounds is continuously reacted with a basic compound in a reactor, with a maximum residence time of the reactive medium in the mixture zone of the reactor of 100 milliseconds; and the precipitate is heated then brought into contact with a surfactant before being calcinated.
Abstract:
A composition is described that includes oxides of zirconium, cerium and another rare earth different from cerium, having a cerium oxide content not exceeding 50 wt % and, after calcination at 1000° C. for 6 hours, a maximal reducibility temperature not exceeding 500° C. and a specific surface of at least 45 m2/g. The composition can be prepared according to a method that includes continuously reacting a mixture that includes compounds of zirconium, cerium and another rare earth having a basic compound for a residence time not exceeding 100 milliseconds, wherein the precipitate is heated and contacted with a surfactant before calcination.
Abstract:
The invention relates to a method for treating a gas containing nitrogen oxides (NOX), comprising a reduction reaction of the nitrogen oxides by a nitrogen-containing reducing agent. The invention is characterised in that the catalyst used for the reduction reaction is a catalytic system containing a composition based on cerium oxide and comprising niobium oxide in a proportion by mass of between 2 and 20 %.
Abstract:
The composition of the invention is based on oxides of zirconium, cerium, niobium and tin in proportions by weight of oxide of between 5% and 50% for cerium oxide, 5% and 20% for niobium oxide, 1% and 10% for tin oxide and the remainder being zirconium oxide. The composition may be used in a catalytic system for an SCR-type process for treating a gas that contains nitrogen oxides (NOx).