Effect of the water-ethanol molar ratio in the ethanol steam reforming reaction over a Co/Ce/MgAl2O4 catalyst

Abstract

A Co/MgAl2O4 catalyst with Ce addition was prepared and characterized by different techniques (BET, XRD, SEM-EDX, TPR and TG-TPO). Its catalytic performance was tested in the ethanol steam reforming reaction at 650°C and a W/FC2H5OH= 50 g min mol−1 using different H2O:C2H5OH molar ratios (MR) in the feed. The presence of Ce on catalyst markedly increased selectivity of hydrogen (from 3.2 to 5.2 molH2/molC2H5OH for MR=4.8) and carbon resistance. The increase of H2O:C2H5OH molar ratio led to a significant decrease in the CO/CO2 ratio (from 0.84 for RM=4.8 to 0.5 for RM=8) and in the carbon amount after 7 h on stream (from 22.9% for RM=4.8 to 6.8% for RM=8). Molar ratios higher than 6 did not significantly improve the catalytic performance. Taking into account previous studies about thermal balance of this reaction, the optimum molar ratio in the ethanol steam reforming seems to be around 6. The ethanol conversion was nearly constant after 7 h in spite of the carbon amount detected by TG-TPO and SEM-EDX. It could be inferred that an important Co fraction was exposed on the filament tips and/or a fraction of carbonaceous species was deposited on the support surface.