dc.description.abstract | Part I:Cu/RHA catalysts
Copper catalysts supported on rice husk ash (Cu/RHA) were tested for partial oxidation of methanol (POM) to produce H2. The catalysts were prepared by deposition-precipitation and characterized by ICP-AES, TGA, XRD, TPR, XPS and N2O titration techniques. The Cu/RHA catalyst with 10.2 wt. % Cu loading and under 673 K calcination has higher copper dispersion and smaller Cu particle size. This catalyst exhibits higher activity and selectivity for POM to produce H2. The partial pressure of O2 plays an important role to determine the product distribution. Catalytic activity of the catalyst at different reaction temperatures shows that CH3OH conversion, H2 selectivity and CO selectivity increase with rise in temperature. At different temperatures along with POM, several reactions such as methanol combustion, steam reforming of methanol, methanol decomposition, water gas shift and oxidation of CO and H2 might be involved. Comparison of catalytic activity of Cu/RHA and Cu/SiO2 catalysts demonstrates that Cu/SiO2 catalysts deactivate with time with faster rate and have higher CO selectivity. This proves that Cu/RHA catalysts have good thermal stability and selectivity for POM to produce H2.
Part II:Cu/ZnO/RHA catalysts
ZnO-promoted copper catalysts supported on rice husk ash (Cu/ZnO/RHA) have been tested for partial oxidation of methanol (POM) to produce hydrogen. The catalyst was prepared by deposition-precipitation method and characterized by XRD, TPR, and N2O titration techniques. Detail study on the catalytic activity of the Cu/ZnO/RHA catalysts was performed to optimize the amount of ZnO promoter, pH, calcination temperature and reaction temperature. The results showed that with appropriate amount of ZnO promoter, CH3OH conversion increased significantly and the undesired by–product, CO was reduced. The improved activity and selectivity is due to the enhanced copper surface area and copper dispersion by the ZnO additon. The catalysts prepared with 1 wt.% ZnO promoter, pH 8, and calcined at 673 K showed the superior catalytic activity because of its high copper surface area under these experimental conditions. The CH3OH conversion and H2 selectivity are increased from 40% to 91.2% and 80.1% to 99.2%, respectively, when rising the temperature from 473 to 573 K. Beyond 523 K, the CO selectivity was significant. Comparison between Cu/ZnO/RHA and Cu/ZnO/SiO2 catalysts proves that Cu/ZnO/RHA is an active catalyst with good stability compared to the silica supported catalyst.
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