滴定法
催化作用
乙烯
化学
环氧乙烷
化学吸附
无机化学
氯
活动站点
氧化物
分解
有机化学
聚合物
共聚物
作者
K. R. Krishna Iyer,Aditya Bhan
标识
DOI:10.1002/cctc.202300329
摘要
Abstract We enumerate the active site density for a promoted Ag/α‐Al 2 O 3 ethylene epoxidation catalyst (35 wt.% Ag) by using trifluoroethanol as a chemical titrant. Trifluoroethanol, when introduced into the reactant stream, deprotonates to deposit stable trifluoroethoxy or trifluoromethyl groups on the Ag surface and inhibits ethylene oxide (EO) rates, thus enabling us to assess catalytic site densities. Active site densities vary between 52 and 69 μmol TFE g cat −1 across different chlorine coverages (0–0.4 monolayers) and different oxygen concentrations (2.5–7.7 mol%) in the reactor feed. Site densities measured by in situ trifluoroethanol chemical titration are distinct compared to those evaluated using ex‐situ N 2 O decomposition (12.3 μmol N2O g cat −1 ) suggesting that dynamic restructuring of the Ag surface under reaction conditions may render pre‐reaction chemisorption measurements insufficient to accurately enumerate the active sites relevant for ethylene epoxidation.
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