| dc.description.abstract | Selective production of hydrogen by oxidative steam reforming of methanol (CH3OH + 0.5H2O + 0.25O2-->2.5H2 + CO2) was investigated over Cu/SiO2-MOx (M=Zn, Zr and Al) catalysts. The catalyst preparation involves two steps. In the first step, the binary supports (SiO2-MOx) were prepared by incipient wetness impregnation method. In the second step, copper was supported on the binary support by deposition-precipitation technique. The catalysts were calcined at 673 K and finally reduced at 623 K. The catalysts were characterized by TGA, XRD, TPR, N2O titration, SEM-EDS and XPS analyses. The XRD analysis confirms the desired phase purity of ZnO, ZrO2 and Al2O3 samples and presence of metallic copper in all these catalysts. The TPR analysis illustrates that the reduction temperature for copper is higher in Cu/SiO2-Al2O3 catalyst than in Cu/SiO2-ZnO catalyst, which suggests that the presence of Zn to binary support could improve the catalytic reductive property. The studies on dissociate adsorption of nitrous oxide at various Si/Zn atomic ratios reveal that the catalyst with Si/Zn atomic ratio 8/2 exhibited better dispersion with smaller copper particle compared to the catalyst with Si/Zn atomic ratio 7/3. XPS analyses demonstrate that metallic copper in the catalysts are oxidized to Cu2O and CuO after catalytic tests. The catalytic activity of the catalysts for oxidative steam reforming of methanol to produce hydrogen depends strongly on the nature of the binary support, particle size and surface area of metallic copper. The activity of the copper catalysts supported on different binary supports shows that the Cu/SiO2-ZnO catalyst exhibited higher activity towards hydrogen formation compared to Cu/SiO2-ZrO2 and Cu/SiO2-Al2O3 catalysts. Since Cu/SiO2-ZnO catalyst showed higher catalytic activity for hydrogen formation, the activity of Cu/SiO2-ZnO catalyst were studied in detail at different Si/Zn atomic ratio, calcination temperature, O2/CH3OH molar ratio, H2O/CH3OH molar ratio and reaction temperature. The catalyst with Si/Zn atomic ratio 8/2 shows higher activity for methanol conversion and hydrogen production rate. The higher activity of the catalyst with Si/Zn atomic ratio 8/2 has been explained in terms of presence of highly dispersed small copper particle. The appropriate molar ratios of O2/CH3OH and H2O/CH3OH for the reaction are found to be 0.3 and 1, respectively. The optimum calcination temperature for OSRM is 673 K. The catalytic performance at various reaction temperatures shows that with increasing reaction temperatures from 473 to 573 K, methanol conversion increases from 15 to 95 % and hydrogen production rate increases from 0 to 269 mmol kg-1 s-1 and CO selectivity increases from 0.5 to 6.7 %. When the CO exceeds few ppm deactivates the Pt electrode, so the appropriate reaction temperature for OSRM is envisaged as 523 K, at which the methanol conversion is 95 % and hydrogen production rate is 287 mmol kg-1 s-1 and CO selectivity is 2.1 %. The present study proves that the Cu/SiO2-ZnO catalysts are active for OSRM that produce high hydrogen content with low carbon monoxide. Therefore, OSRM reaction over Cu/SiO2-ZnO catalyst to produce hydrogen for the application of fuel cells for electric-powered vehicles would be expected. | en_US |