An internal combustion engine wherein an HC treatment catalyst (12) having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst (14), an urea aqueous solution fed from the reducing agent feed valve (15) is arranged upstream of the HC treatment catalyst (12), urea, and NOx contained in the exhaust gas, and HC adsorbed on the HC treatment catalyst 12 are reacted with each other to form intermediate products having cyano groups, oximes, and amino groups, and these intermediate products are sent to the NOx selective reducing catalyst (14).

Exhaust purification device of internal combustion engine

Zeolite-based materials for the selective catalytic reduction of NOx with hydrocarbons

Concerns about emissions of carbon dioxide have created a need to develop more fuel‐efficient vehicles. Diesel engines are generally more efficient than gasoline engines but improvements in the latter can be achieved by operating under lean‐burn conditions. With both diesel and lean‐burn gasoline engines, the nitrogen oxides are emissted under oxidising conditions. It is scientifically very challenging to reduce nitrogen oxides under oxidising conditions. After a short survey of conventional three‐way catalysts, and the associated fundamental aspects of NOx reduction under stoichoimetric conditions, this review focuses on the knowledge and know‐how that has been developed for lean engine emission control. Early research on hydrocarbon selective catalytic reduction on zeolite, oxide, and metal‐based systems is examined, and some of the key mechanistic models are described. Since none of these systems are of sufficient activity and stability to satisfy current legislation attention has turned to NO...

Knowledge and Know‐How in Emission Control for Mobile Applications

An NOx absorbent (6, 6A) is installed in an exhaust conduit (4) of an internal combustion engine (2) capable of fuel combustion at lean air-fuel ratios. An oxygen concentration is repeatedly or continuously decreased by, for example, switching the air-fuel from the lean air-fuel ratio to a stoichiometric or rich air fuel ratio when the exhaust gas temperature is higher than 550°C or when NOx absorbent temperature is higher than 500°C. As a result, the SOx absorbed in the NOx absorbent (6, 6A) during lean air-fuel ratio, low temperature operation is released from the NOx absorbent (6, 6A), and the SOx-poisoned NOx absorbent is recovered.

Exhaust gas purification apparatus for an internal combustion engine

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

In the exhaust gas purifying catalyst (3), palladium is contained as a catalytic component and cerium oxide and (Ce, Pr) compound oxide is contained as a promoter. Now, the weight ratio of cerium oxide to (Ce, Pr) compound oxide is set between 9/1 and 7/3, and the ratio of praseodymium to cerium in the (Ce, Pr) compound oxide is set between 3 mol % and 50 mol %. In this way, because in this exhaust gas purifying catalyst (3), palladium with high low-temperature activity is used for a catalytic component, the exhaust gas purifying performance at low temperature is improved. And because cerium oxide and (Ce, Pr) compound oxide improves catalytic activity of palladium at high temperature, the exhaust gas purifying performance at high temperature, in particular, NOx purifying performance, is improved.

Catalyst for cleaning exhaust gas

Zeolite-supported precious metal catalysts for NOx reduction in lean burn engine exhaust

A catalytic convertor for treating exhaust gas includes a first catalyst layer formed on a base material and a second catalyst layer formed on the first catalyst layer. The first catalyst layer is composed of metal-containing silicate provided with transition metal by ion exchange and at least one precious metal borne on the silicate, and the second catalyst layer is composed of metal-containing silicate provided with transition metal by ion exchange and at least one metal borne on the silicate which is selected from the group consisting of Zr, Co, Cu, Cr, Mn, Y, Fe, Ni, V, Ti, Zn, Ga, Ba, Mg, La, Ce, Pr, Nd, Sm and Tb and differs from the transition metal provided on the silicate by ion exchange.

Catalytic converter for treating exhaust gas

PROBLEM TO BE SOLVED: To provide an exhaust-gas cleaning catalyst arranged with a catalyst layer containing Pd as a catalytic noble metal, alumina and an oxygen occluding material on a honeycomb carrier, wherein a catalytic reaction by the catalytic noble metal and an action of the oxygen occluding material are optimized to provide a high carrying ratio capable of displaying a high cleaning performance when the catalytic noble metal is carried on both of the alumina and the oxygen occluding material. SOLUTION: The catalyst layer 11b consists of the catalyst layer of two layers of upper and lower sides, wherein a carrying amount A, B of Pd per unit weight on first alumina and a Ce-Zr-La-Y alumina complex substance of the lower layer is nearly equivalent. The carrying amount C, D of Rh per unit specific surface area on third alumina and the Ce-Zr-Nd multicomponent oxide of the upper layer is determined such that the latter is grater in the amount. COPYRIGHT: (C)2007,JPO&INPIT

Exhaust-gas cleaning catalyst

PURPOSE:To improve the heat resistance of Ir supported on a catalyst carrier and to maintain satisfactory NOx removing performance and removing performance to HC, etc., at a low temp. over a long period of time by supporting a multiple oxide or a multiple metal compd. contg. Ir as well as other noble metal catalyst on a catalyst supporting layer formed on the surface of a carrier. CONSTITUTION:A catalyst supporting layer 11 contg. a metal catalyst is formed on the surface of a carrier 1 and the multiple oxide of Ir and at least one among Ba, Ti, Zr, Co, Sr, Ca, Cu, Nd, La, Gd, Li and Na as well as other noble metal catalyst is supported on the catalyst supporting layer 11. As a result, Ir excellent in NOx removing performance does not cause such thermal deterioration as vaporization at a high temp. or alloying with other metal catalysts and the satisfactory NOx removing performance is maintained.

Masahiko Shigetsu

Papers

Catalyst for cleaning exhaust gas

Zeolite-supported precious metal catalysts for NOx reduction in lean burn engine exhaust

Catalytic converter for treating exhaust gas

Exhaust-gas cleaning catalyst

Catalyst for purification of exhaust gas