富铈Ce1-xLaxO2催化甲烷氧氯化性能

以硝酸铈、硝酸镧为前体,用氨水共沉淀法制备了一系列Ce_1-xLa_xO₂(x≤0.5)催化剂,利用XRD、N₂吸附-脱附、SEM、Raman、H₂-TPR和OSC对催化剂的物理化学性质进行了表征,并考察其在甲烷氧氯化反应中的催化性能。结果表明:Ce_1-xLa_xO₂催化剂的氧化还原性质随着镧含量的变化发生显著改变,并且这一性质的变化与反应的转化率及产物分布具有较强的联系。Ce_1-xLa_xO₂表面氧物种的活泼性对催化剂活性影响显著,而体相氧物种容易将生成的甲烷氯化物深度氧化。在Ce_1-xLa_xO₂(x<0.3)催化剂上表面氧物种起主导作用,氯甲烷为主要反应产物,Ce_0.8La_0.2O₂催化剂上氯甲烷选择性最高为52%。在体相氧物种更活泼的Ce_0.7La_0.3O₂和Ce_0.5La_0.5O₂上产物中CO的选择性显著上升,Ce_0.5La_0.5O₂催化剂上CO选择性高达48%。稳定性测试表明Ce_0.8La_0.2O₂催化剂具有良好的稳定性。

Catalytic performance of Ce-rich Ce1-xLaxO2 oxides in CH4 oxy-chlorination

A series of Ce_1-xLa_xO₂(x≤0.5) catalysts were prepared by ammonia co-precipitation method and characterized by XRD,N₂ adsorption-desorption,SEM,Raman,H₂-TPR and OSC. Then their catalytic performances in CH₄ oxy-chlorination to chloromethane were investigated. The results showed that the redox properties of Ce_1-xLa_xO₂ changed significantly with the change of the lanthanum content,and there should be a strong link between this change and the conversion and product distribution. More specificly,the surface oxygen species had a remarkable influence on the activities of the catalysts,while advanced oxidation of the generated methane chloride was easily induced by bulk oxygen species. Chloromethane was the main product over Ce_1-xLa_xO₂(x<0.3) and the highest selectivity of chloromethane (52%) could be obtained over Ce_0.8La_0.2O₂. A significant increase of CO selectivity was found over Ce_0.7La_0.3O₂ and Ce_0.5La_0.5O₂ as they had more active bulk oxygen species,and Ce_0.5La_0.5O₂ showed the highest selectivity of CO (48%). The long-term stability test showed that Ce_0.8La_0.2O₂ catalyst had a good stability.