Provided are: a hydrocarbon adsorbent capable of adsorbing hydrocarbons, storing the adsorbed hydrocarbons up to a relatively high temperature, and desorbing the adsorbed and stored hydrocarbons at a relatively high temperature; an exhaust gas purifying catalyst composition using the same; an exhaust gas purifying catalyst; and a method for treating an exhaust gas. The hydrocarbon adsorbent comprises a zeolite having an MRT-type framework structure. The hydrocarbon adsorbent comprises a small-pore zeolite having a total desorption amount ZD.sub.1 of propylene desorbed at 50° C. or higher and lower than 300° C. being 3.5 mmol/g or less and a total desorption amount ZD.sub.2 of propylene desorbed at 300° C. or higher and 500° C. or lower being 0.5 mmol/g or more, per 1 g by mass of the small-pore zeolite, when adsorbing propylene at 50° C. and then heating from 50° C. to 500° C. under the condition of 10° C./min by a temperature-programmed desorption method.

A hydrocarbon adsorbent having high hydrocarbon adsorbing properties even after exposed to a high temperature/high humidity reducing atmosphere, includes a FAU type zeolite having in ESR measurement a spin concentration of a least 1.0 × 10^19 (spins/g) and a ratio of a peak intensity at a magnetic field of at least 260 mT and at most 270 mT to a peak intensity at a magnetic field of at least 300 mT and at most 320 mT of at least 0.25 and at most 0.50 Å and containing bivalent copper. The hydrocarbon adsorbent may be used for a method for adsorbing hydrocarbons to be exposed to a high temperature/high humidity environment, and may be used particularly for a method for adsorbing hydrocarbons in an exhaust gas of an internal combustion engine, such as an automobile exhaust gas.

A composition is provided that has heat resistance sufficient for use as a hydrocarbon adsorbent and desorbs hydrocarbons slowly with respect to an increase in temperature. The composition includes an alkali metal and a zeolite having a YFI structure. A content of the alkali metal is 1 to 40 mass% based on a total mass of the composition, and a content of the zeolite having a YFI structure is 99 to 60 mass% based on the total mass of the composition.

An exhaust-gas purification system of an internal combustion engine includes an electrically heated catalytic device and a three-way catalytic device. The electrically heated catalytic device includes a first honeycomb base having a large number of honeycomb passages and a first catalyst component that is supported on, by a predetermined thin-film treatment, surfaces that define the honeycomb passages and that contains one or more types of noble metals. The three-way catalytic device includes a second honeycomb base having a large number of honeycomb passages and a second catalyst component that is supported on surfaces defining the honeycomb passages and that contains one or more types of noble metals. The total noble metal content per unit volume of the second honeycomb base is higher than the total noble metal content per unit volume of the first honeycomb base.

To provide a hydrocarbon adsorbent having high hydrocarbon adsorbing properties even after exposed to a high temperature/high humidity reducing atmosphere. A hydrocarbon adsorbent, which includes a FAU type zeolite having a lattice constant of at least 24.29 Å and containing copper. Such a hydrocarbon adsorbent may be used for a method for adsorbing hydrocarbons to be exposed to a high temperature/high humidity environment, and may be used particularly for a method for adsorbing hydrocarbons in an exhaust gas of an internal combustion engine, such as an automobile exhaust gas.

A hydrocarbon adsorbent having a high hydrocarbon desorption start temperature and a method for adsorbing hydrocarbons that uses the hydrocarbon adsorbent are provided. The hydrocarbon adsorbent includes an alkali metal and a zeolite having a ring structure that includes at least 10 members is used. In the hydrocarbon adsorbent, a content of the alkali metal is 1 to 40 mass % based on a total mass of the hydrocarbon adsorbent, a content of the zeolite having a ring structure that includes at least 10 members is 99 to 60 mass % based on the total mass of the hydrocarbon adsorbent, and at least a portion of the alkali metal is in a state of being ion-exchangeable.

The present invention relates to a hydrocarbon adsorbent with metal-impregnated zeolite particles having regular mesopores and a manufacturing method therefor. The hydrocarbon adsorbent includes a metal cation and a metal oxide that are impregnated in zeolite particles, in particular, the zeolite particles include regularly formed mesopores having a size of 2 to 10. By adjusting a Si/Al ratio and mesoporosity of the mesopores, a hydrocarbon adsorbent may have increased adsorption capacity for hydrocarbons in a cold-start section and can rapidly oxidize the hydrocarbon upon desorption thereof, thereby reducing the discharge of exhaust gas produced in automobiles and industries.

A catalytic converter includes a hydrocarbon catalyst trap including BEA zeolite configured to adsorb iso-octane at ambient temperatures and desorb iso-octane at temperatures between 150° C. and 170° C., and active metal supercage impregnated USY zeolite configured to adsorb and coke iso-octane at temperatures greater than 150° C.

A hydrocarbon adsorbent according to one exemplary embodiment of the present invention includes a beta zeolite containing copper, in which a Si/Al molar ratio of the beta zeolite is 12.5 to 150, and the amount of the copper contained is 1 wt % to 10 wt %.

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.