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:
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:
Disclosed are (1) a titania-zirconia powder having at least a part of the zirconia solid-dissolved in the titania crystalline phase or at least a part of the titania solid-dissolved in the zirconia crystalline phase, (2) a titania-zirconia powder containing 3 to 30 wt % of zirconia and 0.5 to 10 wt % of yttria and containing less than 20 wt %, in total, of at least a complex oxide having a composition of ZrTiO4 or (Ti,Zr) O2, monoclinic phase zirconia, and tetragonal phase zirconia, wherein the titania-zirconia powder comprises an anatase phase, and which retains a specific surface area of 34 m2/g or more after heat-treated at 900° C. for 5 hours in the air, and (3) a titania-zirconia powder wherein the titania-zirconia powder (1) or (2) having an average particle size of 1 &mgr;m or smaller is mutually dispersed with an alumina powder; and processes for producing the powders are disclosed.
摘要:
Disclosed are a porous material comprising particles without substantial fibrous structure and having pores, the pores having a mean pore diameter in a meson-pore region, sharp pore size distribution, and at least a part of the pores being connected three-dimensionally to form a three-dimensional network structure with random passages, the porous material preferably being of alumina and having a spongy structure or the porous material preferably being an aggregate of particles having an aspect ratio of 3 or less; a process of producing the porous material which includes a step of aging a system capable of becoming an oxide on thermal decomposition; a catalyst for exhaust gas purification having excellent NOx removal performance, high resistance against sulfur poisoning, and satisfactory high-temperature durability which comprises the porous material as a carrier having supported thereon a noble metal and an NOx storage component; and a method of exhaust gas purification using the catalyst.
摘要翻译:公开了一种多孔材料,其包含没有实质纤维结构且具有孔的颗粒,孔具有介孔区域中的平均孔径,尖锐的孔径分布,并且至少一部分孔三维连接以形成 具有随机通道的三维网状结构,多孔材料优选为氧化铝并具有海绵结构,或多孔材料优选为纵横比为3以下的颗粒的聚集体; 一种制造多孔材料的方法,包括使能够在热分解时成为氧化物的体系老化的步骤; 用于排气净化的催化剂具有优异的除去性能,高耐硫中毒性和令人满意的高温耐久性,其包括作为载体的多孔材料负载有贵金属和NO, SUB> x SUB>存储组件; 以及使用该催化剂的排气净化方法。
摘要:
Disclosed are a porous material comprising particles without substantial fibrous structure and having pores, the pores having a mean pore diameter in a meso-pore region, sharp pore size distribution, and at least a part of the pores being connected three-dimensionally to form a three-dimensional network structure with random passages, the porous material preferably being of alumina and having a spongy structure or the porous material preferably being an aggregate of particles having an aspect ratio of 3 or less; a process of producing the porous material which includes a step of aging a system capable of becoming an oxide on thermal decomposition; a catalyst for exhaust gas purification having excellent NOx removal performance, high resistance against sulfur poisoning, and satisfactory high-temperature durability which comprises the porous material as a carrier having supported thereon a noble metal and an NOx storage component; and a method of exhaust gas purification using the catalyst.
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:
An exhaust gas purifying catalyst includes a substrate that defines an exhaust gas passage; a lower catalyst layer formed over the substrate, and an upper catalyst layer formed over the lower catalyst layer. The lower catalyst layer has a lower catalytic precious metal that contains at least one of Pt and Pd, and a lower-layer carrier that supports the lower catalytic precious metal. The upper catalyst layer has an upper catalytic precious metal that contains Rh, and an upper-layer carrier that supports the upper catalytic precious metal. The upper-layer carrier includes an inorganic mixed oxide that contains Ce, Zr, Al, Nd, and at least one element selected from the group consisting of rare earth elements other than Ce and alkaline earth elements. The Nd is unevenly distributed in covering layers that covers surfaces of interior regions within the inorganic mixed oxide.
摘要:
An exhaust gas purifying catalyst includes a substrate that defines an exhaust gas passage; a lower catalyst layer formed over the substrate, and an upper catalyst layer formed over the lower catalyst layer. The lower catalyst layer has a lower catalytic precious metal that contains at least one of Pt and Pd, and a lower-layer carrier that supports the lower catalytic precious metal. The upper catalyst layer has an upper catalytic precious metal that contains Rh, and an upper-layer carrier that supports the upper catalytic precious metal. The upper-layer carrier includes an inorganic mixed oxide that contains Ce, Zr, Al, Nd, and at least one element selected from the group consisting of rare earth elements other than Ce and alkaline earth elements. The Nd is unevenly distributed in covering layers that covers surfaces of interior regions within the inorganic mixed oxide.