Influence of the Support on the Reaction Network of Ethanol Steam Reforming at Low Temperatures Over Pt Catalysts

The influence of the support on the reaction network of steam reforming of ethanol at low temperature was investigated over pure and platinized Al₂O₃, ZrO₂ and CeO₂. The carriers exhibit catalytic activity, which is approximately 3 orders of magnitude lower than that of the Pt-containing catalysts. Product distribution is significantly different over the carriers: ethanol dehydration to ethylene occurs on the surface of all supports and is enhanced over ZrO₂. Alumina favors ethanol etherification to diethyl ether, CeO₂ enhances the formation of acetone, whereas ZrO₂ exhibits higher ethanol dehydrogenation activity. However, over the catalysts, identical products were detected and the nature of the support only affected selectivity variation with temperature. Platinum supported catalysts catalyze ethanol dehydrogenation and the decomposition/reformation of dehydrogenation and dehydration products, as well as the WGS and CO methanation reactions. The reaction network with respect of the nature of the support was investigated employing transient techniques. Specifically, the interaction of ethanol/H₂O mixture, as well as product intermediates (CH₃CHO/H₂O, CO/H₂) with the catalyst surface was probed. Evidence is provided that the main reaction pathway is initiated via ethanol dehydrogenation, through the formation of acetaldehyde, which is decomposed toward methane, hydrogen and CO. Carbon monoxide is consumed via the WGS and methanation reactions. The former reaction is enhanced on Pt/CeO₂ and Pt/ZrO₂ catalysts, whereas the latter is more favorable over Pt/ZrO₂ and Pt/Al₂O₃ catalysts. Acetaldehyde cracking during ethanol steam reforming contributes significantly to carbon deposition, whereas a minor contribution by CO disproportionation and methane decomposition is also observed.