一步固相合成铈钴固溶体低温催化氧化甲苯

One-Step Solid-Phase Synthesis of Ce-Co Solid Solution for Low-Temperature Catalytic Oxidation of Toluene

将硝酸铈、硝酸钴和柠檬酸以固体形式进行混合,无需添加任何溶剂,直接通过程序升温焙烧制备一系列不同Ce/Co比的γCoOx-CeOy (γ = 6,5,4,3;记作6CoOx-CeOy,5CoOx-CeOy,4CoOx-CeOy,3CoOx-CeOy)固溶体催化剂,并以甲苯作为模拟挥发性有机化合物(VOC),评估了不同固溶体催化性能。X射线衍射(XRD)测试表明复合催化剂的晶体结构出现明显松弛畸变。程序升温氢气还原(H2-TPR)测试表明复合后的催化剂晶格氧的可迁移性变得到很大改善。在所有固溶体催化剂中,5CoOx-CeOy取得了最好的最低的甲苯总氧化表观活化能93.06 kJ∙mol−1和二氧化碳收率表观活化能111.62 kJ∙mol−1,其甲苯总氧化和二氧化碳收率的T90%可低至206℃和207℃。此外,也探讨了水蒸汽含量及空速对催化剂稳定性的影响。

A series of γCoOx-CeOy (γ = 6, 5, 4, 3;denoted as 6CoOx-CeOy, 5CoOx-CeOy, 4CoOx-CeOy, and 3CoOx- CeOy) were directly prepared by temperature-programmed calcination, wherein the cerium nitrate, cobalt nitrate and citric acid were mixed by solid form and no need to add any solvent. Toluene was used as a simulated volatile organic compound (VOC) to evaluate the catalytic performance of catalysts. X-ray diffraction (XRD) test showed that the crystal structure of the composite showed obvious relaxation distortion. Temperature-programmed hydrogen reduc-tion (H2-TPR) test showed that the mobility of lattice oxygen was greatly improved. Among all, 5CoOx-CeOy achieved the lowest apparent activation energy for total toluene oxidation of 93.06 kJ/mol and carbon dioxide yield of 111.62 kJ/mol, which of T90% for total toluene oxidation and car-bon dioxide yield can be as low as 206˚C and 207˚C. In addition, the effects of water vapor content and space velocity on the stability were also investigated.