复合沉淀剂制备的CeO2-ZrO2-Al2O3材料及其负载的单Pd三效催化剂

采用了一种由氨水和碳酸铵组成的复合沉淀剂来制备CeO₂-ZrO₂-Al₂O₃ （CZA）复合氧化物。作为对比，分别采用氨水和碳酸铵为沉淀剂制备了另外两个CZA复合氧化物。系统地研究了各CZA材料在织构、结构、氧化还原性能、热老化行为之间的区别，以及其负载的单Pd三效催化剂的催化性能。结果表明，不同的沉淀剂制得的材料中其CeO₂-ZrO₂ （CZ）和Al₂O₃之间的相互作用不同。用氨水做沉淀剂时，得到的材料中CZ和Al₂O₃之间的相互作用很小，导致其热稳定性较差。在碳酸铵做沉淀剂的情况下，CZ和Al₂O₃之间具有很强的相互作用，可以提高材料的热稳定性，但同时，CZ固溶体的均一性被严重破坏，使得材料的氧化还原性能不理想。而复合沉淀剂的使用可以有效地平衡CZ和Al₂O₃之间的相互作用，导致得到的CZA材料具有优异的织构、结构性能及良好的热稳定性。因此，其负载的单Pd催化剂表现出最为优异的氧化还原性能和三效催化活性。

Preparation of CeO2-ZrO2-Al2O3 with a Composite Precipitant and Its Supported Pd-Only Three-Way Catalyst

Acomposite precipitant composed of ammonia and ammoniumcarbonate was used to prepare CeO₂-ZrO₂-Al₂O₃ (CZA). For comparison, two other CZA samples were prepared using ammonia and ammonium carbonate as the precipitants, respectively. Differences in the textural, structural and redox properties, together with the evolution upon thermal aging treatment and the catalytic performance of the corresponding Pd-only three-way catalysts, were investigated systematically. The choice of precipitant was found to affect the interactions between CeO₂-ZrO₂ (CZ) and Al₂O₃. When ammonia was used as the precipitant, the resulting CZ and Al₂O₃ seemed insusceptible to each other, thus the obtained CZA composite displayed inferior thermal stability due to the weakest interaction between CZ and Al₂O₃. In the case of ammonium carbonate, stronger interaction between CZ and Al₂O₃ enhanced the thermal stability of CZA, but in the meantime, the homogeneity of the CZ solid solution was severely impaired by Al₂O₃, leading to undesirable redox performance. Fortunately, the use of the composite precipitant brought about favorable interaction between CZ and Al₂O₃, leading to excellent textural and structural properties along with the highest thermal stability of the CZA compound. Consequently, the corresponding Pd-based catalyst displayed prominent reducibility and oxygen storage capacity (OSC) performance, as well as superior three-way catalytic performance.