Mechanistic aspects of the low temperature steam reforming of ethanol over supported Pt catalysts

The influence of the support of Pt catalysts for the reaction of steam reforming of ethanol at low temperatures has been investigated on Al2O3, ZrO2 and CeO2. It was found that the conversion of ethanol is significantly higher when Pt is dispersed on Al2O3 or ZrO2, compared to CeO2. Selectivity toward H2 is higher over ZrO2-supported catalyst, which is also able to decrease CO production via the water-gas shift reaction. Depending on catalyst employed, interaction of the reaction mixture with the catalyst surface results in the development of a variety of bands attributed to ethoxy, acetate and formate/carbonate species associated with the support, as well as by bands attributed to carbonyl species adsorbed on platinum sites. The oxidation state of Pt seems to affect catalytic activity, which was found to decrease with increasing the population of adsorbed CO species on partially oxidized (Ptδ+) sites. Evidence is provided that the main reaction pathway ethanol dehydrogenation, through the formation of surface ethoxy species and subsequently acetaldehyde, which is decomposed toward methane, hydrogen and carbon oxides. The population of adsorbed surface species, as well as product distribution in the gas phase varies significantly depending on catalyst reactivity towards the WGS reaction. ► Catalytic performance of supported noble metal catalysts depends on the nature of the support. ► Ethanol conversion is higher when Pt is dispersed on Al2O3 or ZrO2, compared to CeO2. ► ZrO2-supported catalyst is able to decrease CO production via the WGS reaction. ► Catalytic activity decreases with increasing the population of adsorbed CO species on Ptδ+ sites. ► The key step for ethanol reforming at low temperatures is ethanol dehydrogenation reaction.