An exhaust gas purifying system has a honeycomb filter including a porous partition wall having a number of pores arranged so that a plurality of cells communicating between two end faces are formed, and a plugging portion disposed in either of the end faces or inside the cell so as to plug the cell
An exhaust gas purifying system has a honeycomb filter including a porous partition wall having a number of pores arranged so that a plurality of cells communicating between two end faces are formed, and a plugging portion disposed in either of the end faces or inside the cell so as to plug the cell; and a NOx purifying catalyst including a honeycomb catalyst carrier having substantially same shape as the honeycomb filter, and a NOx selective reducing SCR catalyst or a NOx occluding catalyst carried on surface of the partition wall and/or on surface of the pores, wherein the honeycomb filter and the NOx purifying catalytic member are disposed in this order in an exhaust gas flow path where exhaust gas discharged from a diesel engine circulates. To provide an exhaust gas purifying system which realizes excellent purifying efficiency of NOx contained in exhaust gas discharged from a diesel engine, and small pressure loss, and can be mounted in limited space.
대표청구항▼
What is claimed is: 1. An exhaust gas purifying system comprising: a first oxidation catalytic member carrying oxidation catalyst containing at least one metal selected from platinum and palladium, and ceria; a honeycomb filter including a porous partition wall having a number of pores arranged so
What is claimed is: 1. An exhaust gas purifying system comprising: a first oxidation catalytic member carrying oxidation catalyst containing at least one metal selected from platinum and palladium, and ceria; a honeycomb filter including a porous partition wall having a number of pores arranged so that a plurality of cells communicating between two end faces are formed, and a plugging portion disposed in either of the end faces or inside the cell so as to plug the cell; a second oxidation catalytic member carrying oxidation catalyst containing at least one metal selected from platinum and palladium, and ceria; and a NOx purifying catalytic member including a honeycomb catalyst carrier having substantially same shape as the honeycomb filter, and a NOx purifying catalyst carried on surface of the partition wall or on surface of the pores, wherein the first oxidation catalytic member, the honeycomb filter, the second oxidation catalytic member, and the NOx purifying catalytic member are disposed in this order in an exhaust gas flow path where exhaust gas discharged from a diesel engine circulates, wherein when the NOx purifying catalyst is the NOx selective reducing SCR catalyst, a first supply part capable of jetting and supplying an urea aqueous solution or ammonia aqueous solution is further provided upstream the NOx purifying catalytic member in the exhaust gas flow path, and a second supply part capable of jetting and supplying an urea aqueous solution or ammonia aqueous solution is further provided upstream the honeycomb filter in the exhaust gas flow path, and wherein cell density of the honeycomb catalyst carrier is 12.4 to 93.0 cells/cm2, and thickness of the partition wall is 0.1 to 0.508 mm, and in the condition that NOx purifying catalyst is carried, the partition wall of the NOx purifying catalytic member has mean pore size of 20 to 65 μm, porosity of 40 to 70%, and common logarithm standard deviation of pore size distribution of 0.1 to 0.6. 2. The exhaust gas purifying system according to claim 1, wherein the NOx purifying catalyst is a NOx selective reducing SCR containing at least one selected from the group consisting of vanadium, titania, tungsten oxide, silver and alumina, or a NOx occluding catalyst containing alkaline metal and/or alkaline earth metal. 3. The exhaust gas purifying system according to claim 1, wherein length of the exhaust gas flow path between the end face located downstream the honeycomb filter and the end face located upstream the NOx purifying catalytic member is 1 m or less. 4. The exhaust gas purifying system according to claim 1, wherein at least part of the honeycomb filter carries oxidation catalyst containing platinum and/or palladium and ceria. 5. The exhaust gas purifying system according to claim 1, wherein at least part of the NOx purifying catalytic member carries oxidation catalyst containing platinum and/or palladium and ceria. 6. The exhaust gas purifying system according to claim 1, wherein the honeycomb filter and/or the honeycomb catalyst carrier is formed of at least one ceramics selected from the group consisting of silicon carbide, cordierite, alumina titanate, Sialon, mullite, silicon nitride, zirconium phosphate, zirconia, titania, alumina and silica. 7. The exhaust gas purifying system according to claim 4, wherein when the honeycomb filter carries the oxidation catalyst, the partition wall of the honeycomb filter in the condition that the oxidation catalyst is carried has a mean pore size which is 10% or more and less than 70% of mean pore size of the partition wall of the NOx purifying catalytic member in the condition that that NOx purifying catalyst is carried. 8. The exhaust gas purifying system according to claim 1, wherein the honeycomb catalyst carrier is formed with a plurality of penetrating cells which communicate between the two end faces and lack the plugging portion by provision of the partition wall, and proportion of number of penetrating cells, relative to the sum of plugged cells in which the plugging portion is placed and the penetrating cells is 10% or more.
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이 특허에 인용된 특허 (1)
Pitcher ; Jr. Wayne H. (Big Flats NY), Diesel particulate trap.
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