Hydrogen production via the steam reforming of biomass-derived ethanol is a promising environmental alternative to the use of fossil fuels and a means of clean power generation. A microkinetic modelling study of ethanol steam reforming (ESR) on Nickel is presented for the first time and validated with minimal parameter fitting against experimental data collected over a Ni/SiO2 catalyst. The thermodynamically consistent model utilises Transition State Theory and the UBI-QEP method for the determination of kinetic parameters and is able to describe correctly experimental trends across a wide range of conditions. The kinetically controlling reaction steps are predicted to occur in the dehydrogenation pathway of ethanol, with the latter found to proceed primarily via the formation of 1-hydroxyethyl. CC bond cleavage is predicted to take place at the ketene intermediate leading to the formation of CH2 and CO surface species. The latter intermediates proceed to react according to methane steam reforming and water gas shift pathways that are enhanced by the presence of water derived OH species. The experimentally observed negative reaction order for water is explained by the model predictions via surface saturation effects of adsorbed water species. The model results highlight a possible distinction between ethanol decomposition pathways as predicted by DFT calculations on Ni close-packed surfaces and ethanol steam reforming pathways at the broad range of experimental conditions considered.

The catalytic steam reforming of bio-ethanol will provide a sustainable route for renewable hydrogen production in a future hydrogen economy. Ni catalysts will be an economically attractive alternative to noble metals. Biochar is a promising reforming catalyst or catalyst support, having shown already good activity for tar reforming. The structure of biochar, its inherent alkali and alkaline earth metallic species and the content of O-containing functional groups are factors affecting its catalytic performance. A kinetic study of ethanol steam reforming and decomposition over a biochar-supported Ni catalyst is presented in this study in order to elucidate the role of biochar in the reaction mechanism. The effects of temperature, space velocity and reactant partial pressure were investigated over a range of conditions. The chemical structural features of used biochar samples were characterized with Raman spectroscopy. Biochar itself was found to be catalytically active and participating in ethanol reforming and decomposition. It was established that the reactions on Ni and biochar active sites were not independent. Analysis of kinetic compensation effects showed commonality on biochar and suggested that the rate-limiting step occurs in the dehydrogenation pathway on the biochar surface. O-containing functional groups in biochar were observed to reduce with reforming/decomposition time.