Abstract: The invention relates to a catalytic composition for treating coal combustion gases, to a method for preparing said composition, to a catalytic system having such a composition, and to the use of the catalytic composition for treating coal combustion gases. The catalytic composition is made of particles of a solid composition cCeO2zZrO2 containing rhodium in the form of Rh2O3 and rhodium in the form of Rh4+.

Abstract: A method and catalytic systems for treating a gas to reduce nitrogen oxide emissions are disclosed. The catalytic systems can include a catalytic composition which comprises an active phase on a support. The active phase is based on rhodium in the form RHx+ and at least another element selected among palladium and platinum and the support is based on cerium oxide and zirconium oxide. Gases capable of being treated by the method and the catalytic systems include in particular those derived from gas turbines, from gas-fired or coal-fired stream plant boilers, or from internal combustion engines.

Abstract: The invention concerns a method for treating a gas to reduce nitrogen oxide emission. Said method is of the type using a catalytic composition comprising an active phase on a support and is characterised in that the active phase is based on rhodium in the form Rhx+ and at least another element selected among palladium and platinum and the support is based on cerium oxide and zirconium oxide. Gases capable of being treated by said method include in particular those derived from gas turbines, from gas-fired or coal-fired steam plant boilers or from internal combustion engines.

Abstract: A method for manufacturing a zinc oxide based powder by coprecipitation with one or more additions is disclosed. The method comprises:a step for the preparation of one or more solutions by dissolving defined quantities of salts of elements that go into the composition of the powder: zinc and addition(s),a step for the preparation of a buffer solution pre-saturated by the said elements, the said buffer solution possessing a pH which is defined so as to cause the precipitation of the hydroxylated compounds of elements corresponding to the elements saturating the buffer solution,a step during which the solutions are added to the said buffer solution, the drop in the pH being compensated for by the addition of a base and the volume of the buffer solution being kept constant by drawing off excess liquid,a step during which the precipitate obtained is treated to obtain the said powder.