| dc.description.abstract | Selective production of hydrogen by oxidative steam reforming of methanol (OSRM)(CH3OH + 0.5H2O + 0.25O2 → 2.5H2 + CO2) over Cu/SiO2 catalysts, prepared by deposition-precipitation method was studied. The catalysts were characterized by ICP-MS, TGA, TPR, Dissociative adsorption of nitrous oxide, XRD, SEM, TEM and XPS analyses. XRD patterns of Cu/SiO2 catalysts showed unclear peak or broad peak of metallic copper or copper oxide, it indicated that the copper species particles, which are amorphous or very small and highly dispersed within the matrix. From TPR, it was difficult to reduce for higher copper loading, had similar reduction temperature with different calcination temperature. Form dissociative adsorption of nitrous oxide, copper loading increases from 4.7 to 24.4 wt% with decrease in dispersion and increase in metallic surface area. TEM images show that copper crystallites are spherical in shape. The particles size of copper increases with increasing the copper loading and calcinaiton temperature. The catalysts were sintering after OSRM reaction. SEM observations show that plate-like structure of these catalysts is formed with great net work structure. XPS analyses demonstrate that in uncalcined catalysts copper existed in three different states i.e. metallic copper (Cu0), copper oxide (Cu2+) and copper hydroxide (Cu(OH)2). After calcination at 673 K and reduction at 600 K the copper states change from copper oxide to metallic copper. Upon reaction, the state reduce to copper oxide that proved metallic copper is the active site. The catalytic activity of Cu/SiO2 catalysts for the OSRM reaction significantly depended on the particle size and surface area of metallic copper. Increasing surface area and decreasing particle size raises the hydrogen production rate. In this study, the catalyst with 17.3 wt% loading and calcined at 673 K showed the highest activity for methanol conversion and hydrogen production. The appropriate molar ratios of O2/CH3OH and H2O/CH3OH for reaction were 0.25 and 1.0, respectively. Both hydrogen production rate and methanol conversion increased with increasing reaction temperature. The reaction pathway is suggested to consist of consecutive oxidative steam reforming of methanol, partial oxidation of methanol, methanol decomposition, and methanol steam reforming. The Cu/SiO2 catalysts showed high activity for OSRM that produce high hydrogen with low carbon monoxide. Therefore, the application of OSRM reaction over Cu/SiO2 in the fuel cells for electric-powered vehicles can be expected. | en_US |