气凝胶骨架镶嵌的CeO_2纳米团簇催化氧化HCl制Cl_2

CeO_2 nanoclusters stabilized in aerogel matrix as catalysts for Cl_2 production from HCl oxidation

采用一步溶胶-凝胶法制备了镶嵌于气凝胶骨架内的CeO2纳米团簇催化材料(CeO2@MxOy,MxOy=SiO2、ZrO2、Al2O3)用于HCl催化氧化反应。镶嵌于气凝胶骨架内的CeO2纳米团簇显著的量子尺寸效应导致其表现出不同于晶相CeO2的特性,H2-TPR测试结果显示在晶相CeO2表面氧物种还原温区内CeO2纳米团簇即可被充分还原。优异的氧化还原性能导致CeO2@MxOy在HCl氧化过程具有良好的催化活性,其中,40CeO2@SiO2的活性最高,在接触时间为0.1598h,VO2/VHCl为1,430℃时,Cl2空时产率可以达到2.10g·(gcat)-1·h-1。催化剂表面的HCl氧化反应同时受O2分压和HCl分压的影响,这表明Cl2从催化剂表面的脱附是该反应的决速步骤。

CeO2 nanoclusters inserted into aerogel matrix （CeO2@MxOy, MxOy= SiO2, ZrO2, Al2O3） prepared by a single-step sol-gel method were used as catalysts for recycling Cl2 from HCl oxidation. Due to their remarkable quantum-size effects, the properties of CeO2 nanoclusters were significantly different from crystal phase CeO2. The CeO2 nanoclusters could be completely reduced at the temperature range for reduction of the surface oxygen species of crystal phase CeO2. The unique properties of CeO2 nanoclusters resulted in the high activity of CeO2@MxOy in the process of HCl oxidation reaction. 40CeO2@SiO2 exhibited the highest activity and the STY （space time yield of Cl2） reached to 2.10 g·（g cat）^-1·h^-1 at 430℃ with VO2/VHCl of 1 and contact time of 0.1598 h. Kinetic studies showed that both O2 and HCl competed for the active sites rendering desorption of surface Cl as the rate-determining step.