K修饰的CZA载体对全钯三效催化剂性能的影响

采取柠檬酸溶胶凝胶法制备铈锆铝复合氧化物（CZA）载体，考察K对Pd/CZA催化剂性能的影响。实验结果表明，K的添加对此类催化剂具有明显劣化作用，其原因在于使用CZA作为载体时，K减弱Pd－Ce相互作用，降低催化剂活性，使之发生中毒；但随着K含量的增大，阻塞催化剂表面的活性位，促使Pd颗粒聚集长大，较大粒径的Pd颗粒有利于三效活性的提高，因而在一定程度上使活性有所恢复。相关的XRD和TPR实验也在一定程度上证明了这点。

Impact of Ce-Zr-Al Mixed Oxide Modified by Potassium on Pd-Only Three-Way Catalysts

The Ce-Zr-Al mixed oxides were prepared by sol-gel method with some special procedures. Pd-K/CZA catalysts were characterized by TG-DTA, XRD, H2-TPR, O2-TPD and CO-TPD. The results showed that the activity of Pd-K/CZA catalysts with a small amount of potassium reduced, when it had been recovered with a large amount of potassium. It is shown by the calculation from CO uptake that the dispersion of Pd increased from 14.8% (K/CZA: 0 wt %) to 22.3% (K/CZA: 1.5 wt%), then decreased to 8.6%(K/CZA: 14.6 wt%). The light-off temperatures of the samples increase with increment of amount of potassium, which is due to poison of potassium that weakens SMSI of Pd-Ce. For the sample K-4 with a big amount of potassium (K/CZA: 14.6 wt%), the poison was lightened because the particle size of Pd is beneficial to the three-way reaction.