Steam reforming of ethanol over Ni/MgAl2O4 catalysts

Hydrogen is considered one of the most promising energy vectors in order to match the current energy and environmental issues. Bioethanol steam reforming is a sound opportunity and close to the industrialization considering an integrated biorefinery concept. MgAl2O4 was selected as a stable support, with improved activity, selectivity and stability due to negligible acidity. Increasing the Ni loading from 1.5 to 10 wt% over MgAl2O4 improved the conversion of ethanol as well as the yield of hydrogen, while the carbon deposition and yield of byproducts decreased. Small acidity characterised the samples, attributed exclusively to the Ni active phase. This prevented extensive catalyst coking due to ethylene formation and subsequent polymerisation. Consequently, small coke amount was found on the spent catalysts, mainly amorphous, allowing rather easy regeneration. DRIFT analysis of adsorbed ethanol at variable temperature evidenced the intermediates of reaction and their evolution with temperature, allowing to suggest the main reaction paths. Acetaldehyde was found as intermediate, rapidly evolving to reformate. Among the possible evolution paths of acetaldehyde, the oxidation to acetate and carbonate species (likely stabilised by the support) was preferred with respect to decomposition to methane and CO. This is reflected in the products distribution evidenced through activity testing.