摘要
应用红外光谱研究了CO,NO及其混合气在氧化态CuO/γ-Al_2O_3上的吸附。用XPS测量了表面铜的价态,用XRD分析了催化剂的物相。综合实验结果可知,催化剂体相为CuO,,CuAl_2O_4,,而Cu^+和Cu^(2+)则在样品表面上并存。红外光谱显示,CO在Cu^+上的吸附比在Cu^(2+)上的吸附强,而NO在Cu^(2+)上的吸附比在Cu^+上的吸附强。当CO和NO共存在体系中,CO选择吸附在Cu^+上,而NO选择吸附在Cu^(2+)上。高于室温时,除分子态吸附外,CO在催化剂表面上部分氧化为HCO_3^-,,CO_3^(2-)以及少量HCOO^-,NO吸附,被氧化为NO_3^-。CO和NO共吸附,CO抑制了NO的氧化。
In this paper, the composition of the bulk phase and the valance states of surface copper ions on the CuO/γ-Al2O3 catalyst were measured by XRD, XPS and the adsorption characteristics of CO and NO were studied by infrared spectroscopy.
It was concluded that the catalyst was composed of CuO and CuAl2O4 in the bulk phase, no other phase was detected. But Cu2+ and Cu+ coexisted on the surface of the catalyst, although the sample was oxidized in an O2 atmosphere.
The low temperature infrared spectra of CO, NO and (CO+NO) adsorption on the catalyst were recorded from 123 K to RT. CO ( or NO) could be adsorbed on Cu2 + (CuO and CuAl2O4)and Cu+ sites below 173K,but CO was only adsorbed on Cu+ sites and NO only on Cu2 + (CuO and Cu Al2O4)sites over 173K. If CO and NO coexisted in the gas phase, CO was selectively adsorbed on the Cu+ sites,whereas NO was selectively adsorbed on the Cua+(CuO and CuAl2O4 ) sites, even the temperature was below 173 K. This phenomenon was clearly demonstrated by the alternate adsorption and coadsorption of CO and NO.
From RT to 673 K, besides molecular state adsorption of CO on Cu + and NO on Cu2 + (CuO and CuA12O4), HCO3-, HCOO-, bridged and uni-dentate CO32- were formed on the catalyst surface for CO adsorption. NO was partially oxidized to NO3- ions on the catalyst surface for NO adsorption. During CO and NO coadsorption, no NO3- was detected, only HCO3- and unidentate CO32- formed on the catalyst surface, so that CO impeded the oxidation of NO to NO3-.
出处
《分子催化》
EI
CAS
CSCD
1991年第4期325-332,共8页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金
