Catalytic Activity of Au loaded CeO_2-MO_x (M = Fe, Zr) Mixed Oxides in Steam Reforming of Methanol

摘要

Au supported on CeO_2-MO_x mixed oxides (M = Fe, Zr) with different Ce/M atomic ratios prepared by deposition-precipitation, were tested for steam reforming of methanol (SRM) in the temperature range of 200-400 °C. Effects of total metal loading, calcination temperature, and Cu/Au atomic ratio were investigated and correlated with catalyst properties. It was found that the use of Au1Cu3/Ce_(0.75)Zr_(0.25)O_2 catalyst exhibited much better catalytic activity in terms of full CH_3OH conversion and 82 % H_2 selectivity when compared with that of Au/Ce_(0.5)Fe_(0.5)O_2 catalyst since the formations of Au-Cu alloy and Ce_(0.75)Zr_(0.25)O_2 solid solution were found to be active for SRM. However, the use of CeO_2-Fe_2O_3 support showed less stable solid solution with short life-time, whereas the use of CeO_2-ZrO_2 coupling with Au-Cu displayed the superior stability with very low coke contamination as the consequences of uniform Au-Cu alloy at the metal site and more stable CeO_2-ZrO_2 solid solution at the support site. For the product distribution, the 7 wt% Au-Cu catalyst gave low CO concentration (10,000 ppm), which can be sent to the CO reduction unit before applying in the proton exchange membrane fuel cell.