焙烧温度对低温水煤气变换Au/Fe2O3催化剂性能的影响

采用改性沉积-沉淀法制备了系列低温水煤气变换Au/Fe2O3催化剂, 发现经300 ℃焙烧的样品具有较好的催化活性和稳定性. 并运用N2物理吸附、原位X 射线粉末衍射(in situ XRD)、程序升温还原(H2-TPR)和X射线光电子能谱(XPS)等技术, 探讨焙烧温度对催化剂性能的影响机制, 同时对样品的失活原因进行了分析. 结果表明, 催化剂性能与焙烧温度引起的金和载体氧化铁的相互作用以及载体还原性质的变化密切相关. XPS表征结果说明, 尽管反应后在催化剂表面有碳酸盐或类碳酸盐物种生成, 但半定量分析表明这些物种的形成不是催化剂失活的主要原因;根据在低温水煤气变换反应过程中Au/Fe2O3催化剂的比表面积明显下降, 载体的结晶度也明显提高, 推断Au/Fe2O3催化剂载体的结构性质的变化才是其失活的主要原因.

Influence of Calcination Temperature on Properties of Au/Fe2O3 Catalysts for Low Temperature Water Gas Shift Reaction

Aseries ofAu/Fe2O3 catalysts for the water gas shift (WGS) reaction were prepared by modified deposition-precipitation method. The sample calcined at 300 ℃ showed higher catalytic activity and better stability than other samples. Using N2 physisorption, in situ XRD, H2-TPR, and XPS techniques, the influence of calcination temperature on properties of Au/Fe2O3 catalyst was explored, and the cause of deactivation was analyzed as well. The results showed that the catalytic behaviors were related to the interaction between Au and Fe2O3, and the reductive property of support, both of which were significantly affected by calcination temperature. Furthermore, according to the results of XPS, although stable carbonate and carbonyl surface species were found on the spent catalysts, the semiquantitative analysis of these species indicated that they were not the main cause of the deactivation. In fact, the deactivation of Au/Fe2O3 was sensitive to the structure change of support. During the water gas shift reaction, Fe3O4 particle would aggregate and crystallize leading to increase in the crystallinity of support and a significant reduction in the surface area of the catalysts, which resulted in the deactivation of Au/Fe2O3.