摘要
研究了乙烯在添加了Re、Cs助剂的电解银催化剂上的环氧化反应,并用热脱附(TDS)、功函数(WF)和程序升温表面反应(TPSR)等手段和方法研究了氧在表面的吸附、与表面间的电子相互作用以及与乙烯的反应。结果表明:乙烯在添加了Re、Cs助剂的电解银上的环氧化活性和选择性显著优于纯电解银。氧在表面存在三种吸附态,其中原子态吸附氧是乙烯环氧化和深度氧化的活性物种,分子态氧对两个反应不起直接作用。在Ag-Re-Cs催化剂中,Re具有抑制乙烯深度氧化,提高环氧化选择性,稳定含Cs银催化剂性能的作用。
An electrolytic silver catalyst with adding Re and Cs was prepared and used in the reaction of ethylene epoxidation. It has been found that both the activity and selectivity on Ag-Re-Cs are higher than that on Ag. Re can stabilize the catalytic performance of electrolytic silver cata lyst with promoter Cs. TDS, WF and TPSR were also used to investigate the adsorption of oxygen and the function of Re and Cs. It can be seen that oxygen adsorbed on the surface has three states: molecular oxygen, atomic oxygen and subsurface oxygen. The adsorbed atomic oxygen is the common oxygen species for both ethylene epoxidation and combustion; molecular oxygen plays no direct role in either two reactions. The role of Re is to suppress the total oxidation of the ethylene, and Cs is to suppress the further oxidation of ethylene oxide. They work in cooperation, which make Ag-Re-Cs catalyst show higher activity and selectivity.
基金
国家自然科学基金
