乙烯环氧化反应机理述评

A review on the mechanism of ethylene epoxidation

本文就多年来人们对乙烯在银催化剂表面发生环氧化反应的机理研究结果进行了综述 ,指出银表面的吸附态原子氧物种是乙烯环氧化反应的关键物种 ,对环氧乙烷的选择性不存在 85.7%的上限 ;依据吸附态原子氧与银之间相互作用的强弱 ,可将其分为“强吸附氧”和“弱吸附氧”。“弱吸附氧”利于乙烯环氧化 ,“强吸附氧”易导致乙烯完全氧化。凡有利于“弱吸附氧”生成的化学环境均利于催化剂选择性的提高。并对次表面氧 (Osub)及氯抑制剂、Cs和 Re助剂的作用机理进行了概括。

This paper reviewed the studies on the mechanism of ethylene epoxidation over silver catalyst.It was pointed out that the chemsorbed atomic oxygen species on silver surface are the key species for ethylene epoxidation;there is not an upper limit of 85 7% for the selectivity to ethylene oxide.There are two adsorption states for the chemisorbed atomic oxygen on silver surface——“strongly adsorbed”and“less strongly adsorbed”.“Less strongly adsorbed”oxygen favors ethylene epoxidation,while“strongly adsorbed”oxygen is likely to cause complete oxidation of ethylene.Atmosphere that favors“less strongly adsorbed”oxygen will favor enhancement of selectivity of the catalyst.Function mechanism of subsurface oxygen,chlorine inhibitor,cesium and rhenium were also outlined.