氧化锰与氧化铈协同等离子体催化氧化甲醇的活性差异研究

Exploration on the difference in performance of manganese oxide and cerium oxide in synergistic plasma-catalytic oxidation of methanol

在等离子体催化系统中,不同催化剂常表现出显著的性能差异.本文通过表面氧物种表征及臭氧氧化原位反应,探究了α-MnO_(2)与CeO_(2)两种常用催化剂在等离子体催化系统中催化氧化甲醇性能差异的本质原因.等离子体催化氧化甲醇的性能评价结果显示,在相同输入功率下CeO_(2)对甲醇的转化率和CO_(2)选择性均高于α-MnO_(2).氧气程序升温脱附(O_(2)-TPD)和X射线光电子能谱(XPS)等表征手段及甲醇常温催化、O_(3)分解和O_(3)催化氧化实验结果表明,CeO_(2)比α-MnO_(2)拥有更多的表面活性氧,能吸附活化更多的甲醇分子;同时,CeO_(2)能更有效地利用臭氧分解产生的活性氧物种对甲醇进行深度氧化.进一步通过原位DRIFTS实验研究两种催化剂协同臭氧催化氧化甲醇反应中间产物的变化,结果表明,CeO_(2)催化剂氧化甲醇的表面副产物较少,而α-MnO_(2)表面则会累积大量的副产物碳酸盐,从而影响其催化性能.

Different types of catalysts usually exhibit significant activity differences in plasma-catalytic systems.In this paper,the performance ofα-MnO_(2) and CeO_(2) in the plasma-catalytic oxidation of methanol was explored by characterizing the surface oxygen species and investigating the in-situ ozone oxidation.At the same input power,CeO_(2) demonstrated higher methanol conversion and CO_(2) selectivity thanα-MnO_(2).By characterizing the catalysts with temperature-programmed desorption of oxygen(O_(2)-TPD)and X-ray photoelectron spectroscopy(XPS),and performing catalytic methanol oxidation,O_(3) decomposition and methanol ozonation experiments at ambient temperature,we revealed that CeO_(2),as compared toα-MnO_(2),possessed more surface oxygen species that are highly beneficial for activating methanol molecules.Besides,CeO_(2) might utilize more effectively the active oxygen species generated by ozone decomposition for complete methanol degradation.In-situ DRIFTS was performed to track the formation of intermediates in catalytic methanol oxidation by ozone over the two catalysts,and suggests that,while a large amount of carbonate by-products accumulate on the surface ofα-MnO_(2),CeO_(2) generated less surface by-products.