Cu-ZSM-5分子筛上[Cu-O-Cu]~(2 )物种的原位红外光谱研究

通过原位监测Cu－ZSM－5分子筛的振动红外光谱随温度及不同处理条件的变化情况，观察到［Cu－O－Cu］2＋物种的形成过程，即两个Cu（OH）＋在脱水过程中经二聚形成［Cu－O－Cu］2＋.低交换度样品开始产生［Cu－O－Cu］2＋物种所需脱水温度较高,通过观察不同处理条件对［Cu－O－Cu］2＋的影响，说明Cu2＋是通过脱出［Cu－O－Cu］2＋中的超晶格氧而被还原为Cu＋,较高温度时［Cu－O－Cu］2＋中的超晶格氧能与气相中的氧达到某种平衡.超晶格氧的脱出性能是影响Cu－ZSM－5分子筛上铜价态变化的重要因素．

A Study of [Cu-O-Cu]~(2 ) Species on Cu-ZSM-5 Zeolite by in situ Infrared Spectroscopy

The appearance of [Cu-O-Cu]2 species with increasing temperature is observed by in situ infrared spectra. [Cu-O-Cu]2 is formed by dehydrated dimer composed of two Cu(OH) . Low copper content sample needs higher temperature to form [Cu-O-Cu]2 than high copper-conten ones. Cu2 ions can be reduced to Cu by release of oxygen from [Cu-O-Cu]2 . In oxygen atmosphere, an equilibrium can be reached between the oxygen in [Cu-O-Cu]2 and the oxygen in gas phase at high temperature. The property of extra-lattice oxygen is an important factor in detendning the change of copper valence.