Synthesis of Mesoporous Cu-Mn-Al2O3 Materials and Their Applications to Preferential Catalytic Oxidation of CO in a Hydrogen-rich Stream

摘要

A series of mesoporous Cu-Mn-Al2O3(CMA) materials was synthesized at moderate temperature and their structures were characterized by XRD, N2 physical adsorption and TPR techniques. It was found that using metal complex ion[Cu(NH3) 42+-Mn(NH3)62+] as raw materials is easier to form good-structure mesoporous Cu-Mn-Al2O3 materials than using its nitrate salt [Cu(NO3)2-Mn(NO3)2]. The TPR tests results indicate that CuO and MnOx were homogeneously dispersed in the mesoporous materials. Their catalytic application to preferential catalytic oxidation of CO in a hydrogen-rich stream was studied. The activity varies in the order of CMA(1:1, molar ratio)> CMA(1:2)>CMA(2:1)>CMA(CP)>CMA(1:0)≈CMA(0:1). The CMA(1:0) and CMA(0:1) have lower activity compared to other samples, implying that there existed coordination effect between Cu-Mn in the samples. The selectivity varied in the order of CMA(0:1)≥CMA(1:2)>CMA(1:1)>CMA(2:1)>CMA(1:0) at higher temperature (≥120 °C), indicating that increasing the Cu content enhanced the conversion of H2. The sample CMA(CP) made by coprecipitation method has a lower CO oxidation activity and selectivity than its counter-parts of mesoporous Cu-Mn-Al2O3 materials[CMA(1:2)], this attributed to the lower surface area of the former and poor interaction of CuO with MnOx.