Abstract: A filter regeneration system for an internal combustion engine, the filter regeneration system including: a calculation unit configured to calculate a minimum oxygen concentration and a minimum nitrogen dioxide concentration at which a passive regeneration reaction, in which carbon in PM accumulated on a filter arranged in an exhaust gas passage of the internal combustion engine reacts with nitrogen dioxide and oxygen to generate carbon dioxide and nitrogen monoxide, occurs based on an amount of the PM accumulated on the filter; and an exhaust gas temperature control unit configured to, in a case where an oxygen concentration and a nitrogen dioxide concentration in exhaust gas on an upstream of the filter are equal to or higher than the minimum oxygen concentration and the minimum nitrogen dioxide concentration, respectively, control a temperature of exhaust gas flowing into the filter within a temperature range in which the passive regeneration reaction occurs preferentially.

Abstract: This particulate matter (PM) sensor is provided with a porous body that has a partition disposed in a passage for exhaust gas including particulate matter, at least a pair of electrodes that oppose each other in a prescribed direction so as to sandwich the porous body, and a deposition part that includes the surface of the partition on the upstream side of the passage, has the particulate matter deposited thereon, and has, formed therein, pores having an average pore diameter smaller than the average pore diameter of the portion of the partition other than the deposition part.

Abstract: A filter regeneration system for an internal combustion engine, the filter regeneration system including: a calculation unit configured to calculate a minimum oxygen concentration and a minimum nitrogen dioxide concentration at which a passive regeneration reaction, in which carbon in PM accumulated on a filter arranged in an exhaust gas passage of the internal combustion engine reacts with nitrogen dioxide and oxygen to generate carbon dioxide and nitrogen monoxide, occurs based on an amount of the PM accumulated on the filter; and an exhaust gas temperature control unit configured to, in a case where an oxygen concentration and a nitrogen dioxide concentration in exhaust gas on an upstream of the filter are equal to or higher than the minimum oxygen concentration and the minimum nitrogen dioxide concentration, respectively, control a temperature of exhaust gas flowing into the filter within a temperature range in which the passive regeneration reaction occurs preferentially.

Abstract: This particulate matter (PM) sensor is provided with a porous body that has a partition disposed in a passage for exhaust gas including particulate matter, at least a pair of electrodes that oppose each other in a prescribed direction so as to sandwich the porous body, and a deposition part that includes the surface of the partition on the upstream side of the passage, has the particulate matter deposited thereon, and has, formed therein, pores having an average pore diameter smaller than the average pore diameter of the portion of the partition other than the deposition part.

Abstract: A CO2 adsorbent that enhances the CO2 recovery rate in the CO2 separation and recovery process is provided. The CO2 adsorbent is made of active carbon and/or molecular sieve carbon with a large specific surface area. The active carbon and/or molecular sieve carbon has micropores and/or mesopores 200 Å or less in size and penetrating pores formed by the micropores and/or mesopores connecting with one another. All or part of surfaces of inner passages through which a gas flows and of terminal pores are covered directly with a polar liquid or polar solid without a reaction layer there between.

Abstract: The present invention provides an NO.sub.x decomposition catalyst which can decompose NO.sub.x in exhaust gas to decrease the amount of NO.sub.x in exhaust gas and is improved in durability through suppression of thermal decomposition thereof, and an exhaust gas purifier wherein said catalyst is used. This NO.sub.x decomposition catalyst is a compound having a brownmillerite type structure represented by the general formula: A.sub.3-X B.sub.X C.sub.4-Y D.sub.Y O.sub.Z, the carbon content of which compound may be at most 1.25 wt. %. This NO.sub.x decomposition catalyst can be used in an exhaust gas purifier applicable to an internal combustion engine.