Abstract: A system for exhaust gas purification disposed in the exhaust pipe of an internal combustion engine, includes an adsorbent comprising a monolithic carrier and an adsorbent component having a hydrocarbon adsorptivity, loaded on the carrier, and a catalyst comprising a monolithic carrier and a catalyst component loaded on the carrier, having a purifiability for the harmful substances present in the exhaust gas emitted from the engine, the catalyst being provided downstream of the adsorbent in the flow direction of the exhaust gas.

Abstract: A system for exhaust gas purification disposed in the exhaust pipe of an internal combustion engine, which includes a zeolite as adsorbent component capable of adsorbing the hydrocarbons present in the exhaust gas emitted from the engine and a catalyst capable of reducing the harmful substances present in the exhaust gas; the system satisfies the following conditions: a/c=3 to 50 cc/g, wherein a is the total volume of the pores of diameters of 10 Å or smaller possessed by the zeolite as measured using N2, and c is the total amount of the hydrocarbons emitted from the engine during the period of 140 seconds from the start of the engine when the engine is operated in accordance with the LA-4 mode of FTP, thereby the adsorption capacity of the zeolite used as a HC adsorbent is optimized against the amount of the HC discharged from an engine during a certain period of the cold start so as to adsorb and purify the HC effectively.

Abstract: A catalyst for exhaust gas purification is capable of purifying the hydrocarbons, nitrogen oxides and carbon monoxide present in the exhaust gas discharged from an internal combustion engine. The catalyst has a carrier and a catalyst layer containing at least one kind of noble metal, Ba and Cs, formed on the carrier. This catalyst for exhaust gas purification is improved in hydrocarbon purification ability for a low-temperature fuel-rich exhaust gas (such as exhaust gas emitted during cold start) of automobile.

Abstract: A method for exhaust gas purification using an exhaust gas purification system including (a) an adsorbent for adsorbing hydrocarbons in internal combustion engine exhaust gas provided in the engine exhaust pipe, (b) at least one catalyst for reducing harmful substances present in the exhaust gas, provided in the exhaust pipe upstream of the adsorbent in the flow direction of the exhaust gas, (c) at least one catalyst for reducing harmful substances present in the exhaust gas, provided in the exhaust pipe down-stream of the adsorbent in the flow direction of the exhaust gas, (d) a first inlet for introduction of secondary air into exhaust gas, formed in the exhaust pipe upstream of the most downstream catalyst of the catalyst (b), and (e) a second inlet for introduction of secondary air into exhaust gas, formed in the exhaust pipe between the catalyst (b) and the most downstream catalyst of the catalyst (c).

Abstract: A system for exhaust gas purification disposed in the exhaust pipe of an internal combustion engine, includes followings (i) a catalyst giving an excellent light-off performance at low temperatures, including a carrier and a catalyst layer supported thereon, the catalyst layer including a precious metal and a substance having an electron donatability and/or a nitrogen dioxide absorbability and releasability, and (ii) 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 a gasoline engine during cold start.

Abstract: A catalyst for purification of exhaust gases, comprising a monolithic carrier and a catalyst layer formed thereon for reduction of the carbon monoxide, hydrocarbons and nitrogen oxides emitted from internal combustion engines, wherein (1) the catalyst layer contains catalyst particles each comprising a heat-resistant inorganic oxide and at least one noble metal selected from Pt, Pd and Rh, loaded thereon, (2) the catalyst layer contains, as a whole, three noble metals of Pt, Pd and Rh, (3) the catalyst layer contains, at any position ranging from the outer surface to the midpoint of the thickness, catalyst particles comprising a heat-resistant inorganic oxide and 2-10% by weight, based on the inorganic oxide, of Pd loaded thereon, and (4) the catalyst layer has, at the outer surface, exposed catalyst particles comprising an heat-resistant inorganic oxide and at least Rh loaded thereon.

Abstract: A catalyst for exhaust gas purification, comprising a heat-resistant inorganic monolith carrier and a catalyst layer loaded thereon, the catalyst layer including a catalyst composition containing at least one noble metal selected from Pt, Pd and Rh, as an active catalyst component, and active alumina. The catalyst composition has a specific surface area of at least 50 m.sup.2 /g and a porosity of at least 50%. This catalyst for exhaust gas purification contains noble metal(s) in a well dispersed state, has excellent high-temperature durability, and is low in thermal deterioration of catalyst performance. Hence, the catalyst can be suitably used as a converter installed in engine manifolds of gasoline engine automobiles, or as a heater having improved purification ability for the exhaust gases emitted from automobiles during their cold start.

Abstract: A catalyst for exhaust gas purification has at least one monolith carrier, at least one first catalyst layer having a three-way catalytic activity, provided on the carrier, and a second catalyst layer having a hydrocarbon purification activity, provided on the first catalyst layer. In a gasoline engine automobile provided with the above catalyst for exhaust gas purification in the exhaust gas system, the hydrocarbons present in the exhaust gas can be converted at a high efficiency by introducing secondary air into the exhaust gas in front of the catalyst to make the exhaust gas lean, at the engine start when a large amount of unburnt hydrocarbons are present in the exhaust gas. Further, the engine warm-up property of the automobile can be improved by the heat generated by the catalytic reaction of the hydrocarbons. The catalyst further exhibits a three-way catalytic activity even during the steady state engine operation after warm-up.

Abstract: A catalyst composition for purification of exhaust gas, including (a) high-silica zeolite having a Si/Al ratio of 40 or more, subjected to ion exchange with at least one metal selected from Pt, Pd, Rh, Ir and Ru, and (b) a heat-resistant oxide containing at least one metal selected from Pt, Pd, Rh, Ir and Ru; a catalyst for purification of exhaust gas, including a monolith carrier and the catalyst composition supported on the carrier; and a process for producing the catalyst. The catalyst has high activity for exhaust gas purification even when the catalyst contains Rh--, --, which is an expensive catalyst component, in a very small amount.