摘要:
This composite oxide powder can secure a large pore volume even after calcination at high temperature and, when a catalyst is formed by loading a noble metal on this composite oxide powder, noble metal grain growth can be suppressed. The composite oxide powder comprises particles of an oxide of a metal M1 and an oxide of a metal M2 which does not dissolve in the oxide of the metal M1, the oxide of the metal M1 and the oxide of the metal M2 being dispersed at the nanometer level. Since different oxides serve as a barrier to each other, sintering is suppressed. Therefore, in the case of composite oxide powder comprising Ce as a metal M1 and Al as a metal M2, grain growth is small even after exposed to high temperature and pores of 3.5-100 nm secure a volume of 0.07 cc/g or more after calcination at 600° C. for 5 hours and a volume of 0.04 cc/g or more after calcination at 800° C. for 5 hours.
摘要:
A composite oxide includes agglomerated particles which have an average particle diameter of 20 μm or less, which are composed of a plurality of metallic element oxides being in form of fine particles having an average diameter of 50 nm or less, and which have a surface and an inner portion whose metallic element distributions differ with each other. The characteristics of the respective metallic elements are exhibited maximally. Hence, it is extremely useful as a support for an exhaust gas purifying catalyst. The catalyst exhibits the activities which degrade less even after it is subjected to a sever durability, is good in terms of the heat and sulfur-poisoning resistance, and can efficiently purify the harmful components in exhaust gases. Moreover, it is possible to produce such a composite oxide and catalyst easily and stably by production processes disclosed herein.
摘要:
Composite oxide powder has a large specific surface area and a large pore volume even after a high-temperature durability test, without losing oxygen storage ability of a single metal oxide. In this composite oxide powder, a first metal oxide having oxygen storage ability is held as ultrafine particles in the form of islands by a second metal oxide which is different from the first metal oxide, pore volume is not less than 2 cc/g and the first metal oxide particles have a diameter of not more than 30 nm even after subjected to high temperature of 900° C. or more. Since the first metal oxide particles are held in the form of islands by the second metal oxide particles, separated from each other and suppressed from contacting each other, the first metal oxide particles hardly grow granularly.
摘要:
A composite oxide includes CeO2, ZrO2 and a metallic oxide being free from reacting with CeO2 and ZrO2 at 700° C. or more, preferably at 900° C. or more and further preferably at 1,000° C. or more. The composite oxide has a regulatory oriented phase, such as a pyrochlore phase, etc., in which at least a part of Ce cations and Zr cations are oriented regularly. The composite oxide makes a catalytic support. The CeO2—ZrO2 composite oxide and the reaction-free metallic oxide make barriers each other which suppress the granular growth when the composite oxide is subjected to high-temperature heat in a reducing heat treatment to form the regulatory oriented phase. The regulatory oriented phase improves the oxygen storage-and-release capability of the catalytic support. Thus, it is possible to simultaneously attain a large a specific surface area and a high oxygen storage-and-release capability.
摘要:
An exhaust gas purification catalyst includes a composite oxide support, and a precious metal catalyst supported on the composite oxide support. The composite oxide support includes alumina, zirconia, ceria, a first additive element oxide and a second additive element oxide. The first additive element oxide contains an additive element selected from the group consisting of rare earth elements excluding cerium and alkali earth elements. The second additive element oxide contains an additive element selected from the group consisting of rare earth elements excluding cerium and alkali earth elements. In the composite oxide support, alumina is contained in a range of 30 to 40% by mass and zirconia is contained in a range of 36 to 46% by mass.
摘要:
An exhaust gas purification catalyst includes a composite oxide support, and a precious metal catalyst supported on the composite oxide support. The composite oxide support includes alumina, zirconia, ceria, a first additive element oxide and a second additive element oxide. The first additive element oxide contains an additive element selected from the group consisting of rare earth elements excluding cerium and alkali earth elements. The second additive element oxide contains an additive element selected from the group consisting of rare earth elements excluding cerium and alkali earth elements. In the composite oxide support, alumina is contained in a range of 30 to 40% by mass and zirconia is contained in a range of 36 to 46% by mass.
摘要:
A catalyst for purifying an exhaust gas includes a support and a noble metal loaded on the support. The support includes a mixture containing a porous oxide and a composite oxide. The composite oxide is expressed by the following formula: (Al2O3)a(CeO2)b(ZrO2)1−b in which the values “a” and “b” are molar ratios and the value “a” falls in a range of from 0.4 to 2.5 and the value “b” falls in a range of from 0.2 to 0.7. The support includes a particle having a particle diameter of 5 &mgr;m or more in an amount of 30% by volume or more. With the thus arranged support, even when the catalyst is subjected to such a severe durability test that it is heated at 1,000° C. for 10 to 20 hours, it exhibits a high purifying activity, and its coating layer is inhibited from cracking or coming off.
摘要:
An ordinary-temperature purifying catalyst includes an oxide having an oxygen defect introduced by a reduction treatment, and a noble metal loaded on the oxide. For example, the oxide can be at least one oxide selected from the group consisting of cerium oxides and zirconium oxides, at least a part of which has an oxygen defect. The catalyst can purify an environmental loading material, such as carbon monoxide, a nitrogen oxide, ethylene, formaldehyde, trimethylamine, methyl mercaptan and acetaldehyde, in air at an ordinary temperature. A method for how to use the catalyst is also disclosed.
摘要:
A porous composite metal oxide, including a mixture of first ultrafine particles containing alumina and second ultrafine particles containing zirconia, wherein the first ultrafine particles and the second ultrafine particles are uniformly dispersed in such a way as to satisfy a condition that standard deviations of content ratios (% by mass) of all metal elements contained in the porous composite metal oxide at 0.1% by mass or more are each 10 or less, the standard deviations being obtained by measuring content ratios of the metal elements at 100 measurement points within a minute analysis region of 20 nm square by energy dispersive X-ray spectroscopy using a scanning transmission electron microscope equipped with a spherical aberration correction function.
摘要:
The object of the present invention is to provide an exhaust gas purifying catalyst that can achieve high purification performance while suppressing H2S emissions. The object is solved by an exhaust gas purifying catalyst in which the lower layer of the catalyst coating layer comprises a ceria-zirconia composite oxide having a pyrochlore-type ordered array structure, in which the ceria-zirconia composite oxide contains at least one additional element selected from the group consisting of praseodymium, lanthanum, and yttrium at 0.5 to 5.0 mol % in relation to the total cation amount, and the molar ratio of (cerium+additional element):(zirconium) is within the range from 43:57 to 48:52.