Abstract
Highly dispersed gold particles (dAu < 5 nm) were deposited on ZnO, ZrO2, and Al2O3 supports by deposition precipitation method. Catalytic activity of gold catalysts toward methanol reforming reactions was tested in the fix bed reactor. The catalytic activity and selectivity of four different methanol reforming processes: methanol decomposition (MD), steam reforming of methanol (SRM), partial oxidation of methanol (POM), and oxidative steam reforming of methanol (OSRM), over gold catalysts were discussed in this study. In comparison with commercial copper catalysts (20 wt% Cu/ZnO-Al2O3), prepared gold catalysts can catalyze the POM reaction at lower temperature (TR) with higher methanol conversion (CMeOH) and lower CO selectivity (SCO). Support of gold catalysts significantly affected the selectivity to hydrogen. Among the tested catalysts, Au/ZnO exhibited the highest methanol conversion, the highest selectivity to hydrogen, and the least contamination of CO. The Au/ZnO was not active to DM and SRM at TR < 623 K but exhibited good activity for POM and OSRM at TR < 423 K. Oxygen in the feed of POM and OSRM definitely promoted the methanol decomposition over Au crystallites at low temperatures. Au/ZnO is an excellent catalyst for reforming methanol to hydrogen rich gas (HRG) through OSRM reaction. At stoichiometries of w (nH2O/nMeOH) = 1.5 and x (nO2/nMeOH) = 0.25 at TR ~ 450 K, a dried HRG product composed with high hydrogen ( > 50 %), low methanol (~ 1 %) and CO (~ 0.2 %) contamination. The composition of HRG is suitable to feed hydrogen fuel cell after a single stage CO removal by preferential oxidation.