| 摘要 |
<p>A catalyst member suitable for catalyzing the oxidation to innocuous substances of gaseous hydrocarbons contained in an oxygen-containing exhaust stream is produced by disposing an adsorbent layer having a desorption temperature TD on a carrier, and coating thereover a permeable catalytic layer having a light-off temperature TL. Deleterious interaction between the adsorbent layer and the catalytic layer is avoided by the method of preparing the catalytic material of the catalytic layer and/or by disposing a barrier layer between the adsorbent layer and the catalytic layer. The preferred method for preparing the catalytic material includes impregnating a refractory support material with a solution containing dissolved salts of one or more platinum group metals, drying the wetted support material and fixing the platinum group metal(s) onto the support by thermal fixation, i.e., calcination, rather than chemical fixation, e.g., by exposure to gaseous H2S. The barrier layer is preferably substantially free of silica and of platinum group metals. The catalytic layer contains a sufficient loading of one or more platinum group metals so that TL∫TD + 150 °C, e.g., there may be 300 grams or more of platinum group metals per cubic foot of the catalyst member.</p> |
