Hydrocarbon (HC) traps are disclosed. The HC trap may include a first zeolite material having an average pore diameter of at least 5.0 angstroms and configured to trap hydrocarbons from an exhaust stream and to release at least a portion of the trapped hydrocarbons at a temperature of at least 225° C. The HC trap may also include a second zeolite material having an average pore diameter of less than 5.0 angstroms or larger than 7.0 angstroms. One or both of the zeolite materials may include metal ions, such as transition, Group 1A, or platinum group metals. The HC trap may include two or more discrete layers of zeolite materials or the two or more zeolite materials may be mixed. The multiple zeolite HC trap may form coke molecules having a relatively low combustion temperature, such as below 500° C.

A reducing agent injection device includes a first honeycomb structure and a urea spraying device spraying a urea water solution in mist form. A pair of electrode members is formed in the first honeycomb structure. The ratio L/D of length L in the cell extending direction of the honeycomb structure body to diameter D of the cross section perpendicular to the cell extending direction is 0.5 to 1.2. Also, it is preferable that a urea hydrolysis catalyzer is provided in the second end face side of the honeycomb structure body, with a gap from the second end face.

The present invention is related to a catalyst supported for the selective oxidation of sulphur compounds of the tail gas from the Claus process or streams with an equivalent composition to elemental sulphur or sulphur dioxide (SO.sub.2). It is also the object of the present invention, a process for the preparation of a catalyst of this type, as well as the process of selective oxidation of sulphur compounds to elemental sulphur using the catalyst of the invention, as well as the process of catalytic incineration of the tail gas from the Claus process using the catalyst of the present invention.

A porous ceramic honeycomb body (10) including intersecting walls that form channels (22) extending axially from a first end face to a second end face and layered plugs (62) comprised of a first layer (64) disposed on channel walls and a second layer (66) disposed inward toward an axial center of each respective channel on the first layer. The plugs seal at least one of a first portion of the channels at the first end face and a second portion of channels at the second end face of the porous ceramic honeycomb body.

An emissions treatment system for an exhaust stream of an internal combustion engine including hydrocarbons, carbon monoxide, and nitrogen oxides is provided. The disclosed system can include an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold; a first three-way conversion catalyst (TWC-1) located downstream of the internal combustion engine in the exhaust conduit; an SCR-HCT catalyst comprising a selective catalytic reduction catalyst and a hydrocarbon trap downstream of the TWC-1 in the exhaust conduit; and a third catalyst downstream of the SCR-HCT combination in the exhaust conduit, the third catalyst comprising a platinum group metal (PGM) e.g., in an amount effective to oxidize hydrocarbons. Methods of making and using such systems and components thereof are also provided.

A method is disclosed for the preparation of a metal exchanged microporous materials, e.g. metal exchanged silicoaluminophosphates or metal exchanged zeolites, or mixtures of metal exchanged microporous materials, comprising the steps of providing a dry mixture of a) one or more microporous materials that exhibit ion exchange capacity and b) one or more metal compounds; heating the mixture in a gaseous atmosphere containing ammonia and one or more oxides of nitrogen to a temperature and for a time sufficient to initiate and perform a solid state ion exchange of ions of the metal compound and ions of the microporous material; and obtaining the metal-exchanged microporous material.

The honeycomb structure includes a honeycomb structure body having porous partition walls, and a plugging portion disposed in one of open ends of each cell, a thickness of the partition walls is 0.30 mm or more and 0.51 mm or less, a cell density is 30 cells/cm.sup.2 or more and 93 cells/cm.sup.2 or less, a filtration area (cm.sup.2) of inflow cells included per cm.sup.3 of the honeycomb structure body is defined as an inflow side filtration area G (cm.sup.2/cm.sup.3), a value obtained by dividing a pore volume Vp (cm.sup.3) formed in the partition walls by a total volume Va (L) including the cells is defined as a pore volume ratio A (cm.sup.3/L), and in this case, a product of the inflow side filtration area G (cm.sup.2/cm.sup.3) and the pore volume ratio A (cm.sup.3/L) is 1800 cm.sup.2/L or more and 3200 cm.sup.2/L or less.

A process for the removal of nitrous oxide from a gas stream having a contaminating concentration of nitrous oxide to provide a gas stream with a significantly reduced concentration of nitrous oxide is described. The process includes the use of a process system having multiple N.sub.2O decomposition reactors each of which contain a nitrous oxide decomposition catalyst and heat transfer units each of which contain a heat sink media that are operatively connected in a particular order and arrangement for use in the process. The gas stream is passed to the process system that is operated for a period of time in a specific operating mode followed by the stopping of such operation and reversal of the process flow. These steps may be repeatedly taken in order to provide for an enhanced energy recovery efficiency for a given nitrous oxide destruction removal efficiency.

A process for the removal of nitrous oxide from a gas stream having a contaminating concentration of nitrous oxide to provide a gas stream with a significantly reduced concentration of nitrous oxide is described. The process includes the use of a process system having multiple N.sub.2O decomposition reactors each of which contain a nitrous oxide decomposition catalyst and heat transfer units each of which contain a heat sink media that are operatively connected in a particular order and arrangement for use in the process. The gas stream is passed to the process system that is operated for a period of time in a specific operating mode followed by the stopping of such operation and reversal of the process flow. These steps may be repeatedly taken in order to provide for an enhanced energy recovery efficiency for a given nitrous oxide destruction removal efficiency.

A reducing agent injection device includes a honeycomb structure having a honeycomb structure body and a pair of electrode members arranged in a side surface of the honeycomb structure body and a urea spraying device spraying a urea water solution in mist form. The urea water solution sprayed from the urea spraying device is supplied inside cells from a first end face of the honeycomb structure body, and urea in the urea water solution supplied in the cells is heated and hydrolyzed inside the electrically heated honeycomb structure body to generate ammonia. The ammonia is discharged outside the honeycomb structure body from a second end face and injected outside. There is provided a reducing agent injection device that can generate and inject ammonia from a urea solution with less energy.