摘要:
Thermally stable/highly reducible catalyst compositions, well suited for the catalytic conversion of exhaust gases emanating from internal combustion engines notably vehicular exhaust gases, comprise alumina, the oxides of cerium praseodymium and zirconium, and, optionally, at least one other oxide of bismuth, of a rare earth, or of an element of group VIII of the Periodic Table, and exhibit a stabilized hydrogen-absorption capacity up to a temperature of at least 1,000.degree. C.
摘要:
The invention provides a catalytic composition which is based on a cerium oxide and on at least one other oxide chosen from iron, manganese and praseodymium oxides, which controls H.sub.2 S emissions in the catalysis of treatment of automobile exhaust gas.
摘要:
The invention relates to new compositions based on ceric oxide having an improved oxygen storage capacity, these compositions being characterized in that they contain, besides ceric oxide, at least one oxide of another metallic element M chosen from the group consisting of iron, bismuth, nickel, tin and chromium or one of their mixtures, this oxide preferably being in solid solution with the abovementioned cerium oxide. The process of synthesis of these compositions consists in first of all preparing an intimate mixture between (i) a ceric oxide or a ceric hydroxide and (ii) at least one additive consisting of a hydroxide or a salt, thermally decomposable to an oxide, of the metallic element M, and in then calcining this mixture so as to obtain the desired composition based on oxides. The compositions according to the invention are particularly useful in the manufacture of catalysts and/or catalyst supports, especially those intended for treating exhaust gases from internal combustion engines.
摘要:
Thermally stable ceric oxide-based compositions, well suited as catalysts/catalyst supports for a wide variety of reactions, notably for the catalytic conversion of exhaust gases emanating from internal combustion engines, comprise particulates of immixture of a major amount of ceric oxide with at least one other metal oxide of magnesium, gallium, boron, scandium, or mixture thereof, and having a specific surface greater than 10 m.sup.2 /g after calcination at 800.degree. C.
摘要:
A detection gate for detecting substances carried by an individual or an object, has two lateral uprights facing one another and defining a passage there between for the individual or the object, a blowing device installed in a blowing chamber in one of the uprights which are adapted to exhaust the air contained in the blowing chamber towards the other upright, an exhaust device installed in an exhaust chamber in the other upright, which are suitable for exhausting the air thus blown, a detection device arranged upstream from the passage and adapted to detect the presence of the substances in the air thus blown, and a transfer line which, via one of the ends thereof, leads into the blowing chamber and, via the other end thereof, into the exhaust chamber, the blowing device and the exhaust device being such that a single volume of air has time to pass through the passage at least twice during the time that individual or the object is present in the passage.
摘要:
Unique compositions based on at least one crystalline rare earth sesquisulfide, well suited for the coloration of a wide variety of substrates, e.g., cosmetics, plastics, paints and rubbers, contain a dopant amount of at least one alkali/alkaline earth metal, at least a fraction of which being included within the crystal lattice of such at least one rare earth sesquisulfide.
摘要:
A detection gate for detecting substances carried by an individual or an object, has two lateral uprights facing one another and defining a passage there between for the individual or the object, a blowing device installed in a blowing chamber in one of the uprights which are adapted to exhaust the air contained in the blowing chamber towards the other upright, an exhaust device installed in an exhaust chamber in the other upright, which are suitable for exhausting the air thus blown, a detection device arranged upstream from the passage and adapted to detect the presence of the substances in the air thus blown, and a transfer line which, via one of the ends thereof, leads into the blowing chamber and, via the other end thereof, into the exhaust chamber, the blowing device and the exhaust device being such that a single volume of air has time to pass through the passage at least twice during the time that individual or the object is present in the passage.
摘要:
Storage-stable colloidal organic sols comprise suspended tetravalent metal oxide particulates in an organic diluent medium, notably cerium dioxide particulates, the tetravalent metal oxide particulates having a particle size d90 no greater than 200 nanometers and being complexed with at least one amphiphilic organic acid, and either said tetravalent metal oxide particulates comprising agglomerates of crystallites, the d80 of which being no greater than 5 nanometers and at least 90% of said agglomerates comprising from 1 to 5 crystallites, and/or said at least one amphiphilic organic acid has from 11 to 50 carbon atoms and is branched in at least one of the &agr;-, &bgr;-, &ggr;- or &dgr;-positions relative to the atom bearing the acidic hydrogen.
摘要:
The invention concerns a procedure for preparation of a precursor of a mixed cerium and zirconium oxide-based composition, characterized by the following steps:a liquid mixture is prepared containing cerium and zirconium compounds;the preceding mixture is placed in contact with carbonate or bicarbonate, thus forming a reactive medium exhibiting a neutral or basic pH during the reaction;the precipitate obtained is collected.A mixed cerium and zirconium oxide-based composition is obtained by calcining this precursor. This composition is characterized by the fact that it has a total pore volume of at least 0.6 cm.sup.3 /g, and that at least 40%, and more particularly at least 50%, of the total pore volume is composed of pores having a diameter of at most 1 .mu.m.
摘要:
Cerium/zirconium mixed oxides (optionally including yttrium values), comprising solid solutions thereof, having contents of zirconium of up to 60 atom % and having thermally stable, very high specific surface areas at least greater than 80 m.sup.2 /g, preferably at least 100 m.sup.2 /g and more preferably at least 150 m.sup.2 /g, are well suited as catalysts and/or catalyst supports, notably for the treatment/conversion of vehicular exhaust gases; such Ce.sub.x Zr.sub.1-x O.sub.2 particulates are conveniently prepared by thermally treating an aqueous solution of soluble compounds of cerium and zirconium (and optionally yttrium), e.g. the nitrates thereof, present in the desired stoichiometric amounts, and thence recovering and, if appropriate, calcining the reaction product thus formed.