高温老化气氛对单钯三元催化剂活性的影响

EFFECTS OF THE HIGH-TEMPERATURE AGEING ATMOSPHERE ON THE ACTIVITY OF THE 3-WAY Pd-YCZ CATALYSTS

本文制备了一种含 Y、Ce和 Zr的单钯三元催化剂 (Pd- YCZ)。在 1 0 50℃下 ,分别于空气和配气中对这一催化剂进行了高温老化 ,并对其催化活性进行了测试。实验结果表明 ,Pd-

The present paper presents a kind of Pd only three way catalyst with Y, Ce and Zr (Pd YCZ), which proves to be aged under different experimental conditions at 1 050 ℃ for 1.5 h. One of such Pd YCZ catalysts turned to be aged in air in muffle oven and the others aged in the simulated gases in a reactor. The volume percentage of the simulated gases were 0.80% O 2, 0.75×10 -3 C 3H 6, 1.00×10 -3 NO and 1.00% CO, and N 2 balanced. The space velocity of the gases was 60 000 h -1 . In addition, the above said aged catalysts were tested and evaluated under the same conditions, which proves that Pd YCZ aged in air in muffle oven shows little deactivation, while Pd YCZ aged in simulated gases in rector shows large deactivation. Thus, it can be thought that the ageing atmosphere may have takes great effect on the deactivating process of Pd YCZ. On the other hand, since it was aged in air in the muffle oven, Pd only participated in the oxidizing process and then oxidized into PdO, the space velocity of the ageing gases can be so small as to be almost zero. But aged in simulated gases in a reactor, Pd YCZ would be oxidized and shrunk repeatedly when reacting with the simulated gases at high temperature. Such catalytic reaction can promote the increase of the palladium particle size, and in turn, decrease their catalytic activation. At the same time, the strong washing effect of the gases at a high space velocity would also lead to the deactivation process of Pd YCZ with it being aged in the simulated gases. Therefore it can be concluded that high space velocity of the simulated gases in the catalytic reaction at 1 050 ℃ etc proves to be the main reason for the deactivation of the catalysts aged in simulated gases.