| 摘要 |
PROBLEM TO BE SOLVED: To ensure high hydrothermal stability and to efficiently adsorb lower hydrocarbons in the exhaust gas of an automobile by preparing a hydrocarbon adsorbent from a zeolite having a hydrophobic porous refractory layer on the outer surface and having a specified SiO2 to Al2O3 molar ration in its composition. SOLUTION: The adsorbent excellent in capability to adsorb hydrocarbons, particularly <=3C hydrocarbons in the exhaust gas of an automobile is prepared from a zeolite having a hydrophobic porous refractory layer on the outer surface and having an SiO2 to Al2O3 molar ratio of <=200 in its composition. The thickness of the refractory layer is <=500 nm. The zeolite contains at least one framework structure selected from MFI type, MEL type, BEA type, FAU type, MOR type, FER type, EUO type and NES type structures, etc., and at least one element selected from Ga, B, Ti, Zr, Co, Zn, In, Sn, Sb, P, etc., is contained in the framework.
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