| 摘要 |
PROBLEM TO BE SOLVED: To treat hydrocarbons in an exhaust gas by a process in which the exhaust gas passes through a specified upstream layer to a specified downstream layer, and the hydrocarbon is adsorbed in the downstream layer at a low temperature, desorbed at a high temperature, returned to the upstream layer, and oxidized with the use of a catalyst. SOLUTION: A downstream layer containing an adsorbent which contains zeolite whose silica/alumina weight ratio is greater than 300, adsorbs hydrocarbon in exhaust gas at a relatively low temperature, and desorbs it at a relatively high temperature and an upstream layer which is arranged on the downstream layer and contains a catalyst which is bonded to a support which does not adsorb the hydrocarbon preferentially to water are provided. The catalyst is active for the conversion of the hydrocarbon into carbon dioxide and water. The layers are arranged so that the exhaust gas passes through the upstream layer to the downstream layer for the downstream layer to adsorb the hydrocarbon at a relatively low temperature, and the hydrocarbon subsequently desorbed at a relatively high temperature passes back through the upstream layer. |
