| 摘要 |
PURPOSE:To obtain catalysts for purifying exhaust gas whereby even under conditions of lean-gas combustion, NOx can be efficiently reduced and purified by heat-treating zeolite catalysts having been ion-exchanged by means of transition metals in a gas stream containing sulfur compounds. CONSTITUTION:A zeolite catalyst 1 having been ion-exchanged by means of copper ions is put into, for example, an electric furnace 2 and gas 4 containing hydrogen sulfide (H2S: about 1000-10000ppm) is caused to flow from a hydrogen sulfide bomb 3. At the same time, the furnace 2 is heated by means of a heater 5 (usually to about 500-700 deg.C), so that copper oxides and the like which are attached, during ion-exchange, to an area other than a point where ion exchange is carried out and oxidized, are sulfurized to provide copper sulfides to eliminate oxidation activity. As a result, intended catalysts for purifying exhaust gas are obtained. The catalysts thus obtained eliminate catalytic action of oxides which oxidize hydrocabons, so that it is possible to accomplish purifying ratio of NOx in a NOx purification process. |
