A catalyst for purifying exhaust gases exhibits not only effective purifying characteristics even in a low temperature range such as immediately after an engine starts but also high exhaust gas purifying ability. In the catalyst for purifying exhaust gases of a first aspect of the invention, HC adsorbed at low temperature are released at high temperature and the released HC are purified by a catalyst metal. This catalyst for purifying exhaust gases has an excellent advantage in purifying HC at low temperature as well as excellent exhaust gas purifying ability.

Catalyst for purifying exhaust gases

An exhaust gas-purifying catalyst includes a substrate, and a catalytic layer facing the substrate and including a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope. Another exhaust gas-purifying catalyst includes a substrate, and a catalytic layer formed on the substrate using slurry containing a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope.

Exhaust gas purifying catalyst

The present invention relates improving the performance of nitrogen oxide reduction by exposing rich exhaust to catalysts systems comprising a catalyst, wherein the catalyst systems are free of platinum group metals. The present invention also relates to improving reduction of carbon monoxide and hydrocarbon in exhaust by introducing air into a portion of the exhaust between a first catalyst system and a second catalyst system. The present invention also relates to improving nitrogen oxide, carbon monoxide and hydrocarbon reduction by (1) exposing rich exhaust to a first catalysts system, wherein the exhaust has an R value of greater than 1.0 and the first catalyst system comprises a catalyst and is free of platinum group metals and (2) introducing air into a portion of the exhaust in between the first catalyst system and a second catalyst system, wherein the second catalyst system is free of platinum group metals.

Zero platinum group metal catalysts

The composite oxide and the composite oxide carrier are manufactured by the precursor forming step and firing step. The precursor forming step includes high speed mixing means. The composite oxide catalyst is obtained by preparing a composite of catalytic components simultaneously with the formation of the precursor of composite oxide in the step of forming the precursor of composite oxide. The composite oxide and the composite oxide carrier are composed of a composite oxide in which at least one of cerium and zirconium, and aluminium disperse with extremely high homogeneity. With this structure, the heat resistance of the carrier is improved and consequently, enlargement of particles of the composite oxide defining the carrier, and sintering of adjacent particles of the composite oxide can be restrained, whereby the catalyst using the composite oxide carrier in accordance with the present invention is excellent in heat resistance. With the present invention, the carrier is not limited to a general catalyst carrier. The carrier may be interpreted to indicate general formed bodies. For example, the carrier with the present invention can be also used as materials for sensors and electrodes, optical materials, semiconductors and structure materials. Furthermore, the carrier can be used for a three-way catalyst, NOx catalyst or oxidation catalyst or a part thereof, and a promoter.

Composite oxide, composite oxide carrier and catalyst

A system for exhaust gas purification disposed in the exhaust pipe of internal combustion engine, includes the followings (C) and (D): (C) a catalyst giving an excellent light-off performance at low temperatures, comprising a carrier and a catalyst layer supported thereon, the catalyst layer comprising a precious metal and a substance having an electron donatability and/or a nitrogen dioxide absorbability and releasability, and (D) an adsorbent comprising a carrier and an adsorbent layer having a hydrocarbon adsorbability, supported on the carrier. This system for exhaust gas purification can effectively purify the harmful substances contained in the exhaust gases discharged from internal combustion engines of automobiles, etc., particularly the hydrocarbons discharged in a large amount from gasoline engines during their cold start.

System for exhaust gas purification and method for exhaust gas purification using said system

A catalyst for purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gases at the stoichiometric point or in oxygen-rich atmospheres, is disclosed, and it includes a support in which at least one element selected from the group consisting of alkali metals, alkaline-earth metals and rare-earth elements including La is dissolved in titania to form a solid solution, and a noble metal catalyst ingredient loaded on the support. A process for purifying, by bringing the exhaust gases into contact with the catalyst, is also disclosed.

Hiromasa C O Toyota Jidosha K.K. Suzuki

Papers

Process for purifying exhaust gases