Cu－ZSM－5分子筛表面铜离子的价态研究

A Study of Copper Valence on Cu-ZSM-5 Zeolite

以吸附ＣＯ红外光谱结合ＴＰＲ谱详细表征了经真空自还原及用不同还原剂还原的ＣｕＺＳＭ－５分子筛样品，考察了表面铜离子的价态分布情况及其影响因素。得知铜在Ｃｕ－ＺＳＭ－５表面是分步还原的。用不同方法进行氧化和还原时的难易程度不同。研究了用不同方法进行氧化还原时铜的价态转变条件和铜离子在不同价态间氧化还原循环的可逆性。Ｃｕ２＋与Ｃｕ＋间的氧化还原循环完全可逆，而Ｃｕ０与Ｃｕ＋间的氧化还原循环不完全可逆。Ｃｕ０氧化为Ｃｕ＋比Ｃｕ＋氧化为Ｃｕ２＋容易进行，探讨了Ｃｕ＋在Ｃｕ－ＺＳＭ－５分子筛中不同位置的分布情况及铜在不同条件下的氧化还原机理。

In-situ CO adsorption infrared spectroscopy and H2-TPR techniques were used to study the distribution of different valences of copper in the sample and the factors which influence such a distribution.The reduction mechanism is put forward on the basis of the results obtained. It is demonstrated that Cu2+is reduced to Cu0 through Cu+.The condition of changing valence by different reductant was studied and it was found that the redox process between Cu2+and Cu+is reversible,whereas that between Cu+ and Cu0 is not fully reversible.The Cu0 is easier to be oxidized to Cu+ than Cu+to Cu2+.The distribution of Cu+at different sites and the conditions for valence change were also studied.