摘要:
The invention relates to a suspension of cerium oxide particles in which the particles (secondary particles) have an average size not exceeding 200 nm, said secondary particles being comprised of primary particles having an average size not exceeding 100 nm with a standard deviation having a value not exceeding 30 % of the value of said average size. This suspension is prepared from a solution of a cerium-III salt, comprising cerium IV or hydrogen peroxide, which is brought into contact with a base in the presence of nitrate ions and in an inert atmosphere. The medium thus obtained is submitted to a thermal processing in an inert atmosphere, then acidified and scrubbed. The powder is obtained by drying and calcining of the suspension. The suspension and the powder can be used for polishing.
摘要:
The composition of the invention comprises at least one supported oxide chosen from zirconium oxide, titanium oxide or a mixed zirconium titanium oxide on an alumina-based or aluminium-oxyhydroxide-based support and is characterized in that, after calcination for 4 hours at 900°C, the supported oxide is in the form of particles deposited on said support, the size of said particles being at most 10 nm when the supported oxide is zirconium oxide and being at most 15 nm when the supported oxide is titanium oxide or a mixed zirconium titanium oxide. The composition of the invention may be used as catalyst, especially for the selective reduction of NOx.
摘要:
The composition of the invention is based on zirconium oxide, which comprises 1 to 20% yttrium oxide, 1 to 30% tungsten oxide and the balance zirconium oxide. This composition may have a specific surface area of at least 40 m2/g after calcination at 700oC for 4 hours and an acidity measured by the methylbutynol test of at least 90%. The composition may be used as a catalyst or catalyst support, especially for the treatment of motor vehicle exhaust gases.
摘要:
The composition of the invention comprises at least one supported oxide, based on a zirconium oxide, a titanium oxide or a mixed zirconium titanium oxide on a silica-based support. The composition is characterized in that, after calcination for 4 hours at 900 °C, the supported oxide is in the form of particles deposited on said support, the size of the particles being at most 5 nm when the supported oxide is based on a zirconium oxide, being at most 10 nm when the supported oxide is based on a titanium oxide and being at most 8 nm when the supported oxide is based on a mixed zirconium titanium oxide. The composition of the invention may be used as catalyst, especially for the selective reduction of NOx.
摘要:
The colloidal dispersion of the invention is a dispersion of inorganic particles in a liquid phase of the invention which contains an ampholytic copolymer comprising at least one macromolecular chain B and a part A bonded to a single end of at least one macromolecular chain B and in which the macromolecular chain B comprises cationic units Bc, deriving from cationic monomers Bc and the part A is a polymeric or non-polymeric group comprising at least one anionic or potentially anionic group. This dispersion may have a positive zeta potential within a pH range between 1 and 11.
摘要:
The invention relates to a composition containing zirconium oxide, silicon oxide and an oxide of an element M selected from titanium, aluminium, tungsten, molybdenum, cerium, iron, tin, zinc, and manganese, in the following mass proportions of said different elements: silicon oxide : 5%-30%; de M-element oxide : 1%-20%; the balance consisting of zirconium oxide. The composition further has an acidity, as measured by the methylbutynol test, of at least 90 %. The composition can be prepared according to a method that involves placing a zirconium compound, a silicon compound, an M-element compound and a basic compound in a liquid medium, thereby generating a precipitate; maturing said precipitate in a liquid medium; and separating and calcining the precipitate. The composition can be used for processing the exhaust gases of diesel engines.