A comparative study of CeO2 and Nb2O5-based supports for ethanol steam reforming (ESR) catalysts

Abstract

Ethanol steam reforming (ESR) over CeO₂ and Nb₂O₅-based supports was studied in order to determine the role played by the support in the processs of hydrogen generation for fuel cells. Temperature of calcination as well as the presence of dopants influence the chemical and physical characteristics of the supports with impact in the product mixture distribution. The CeO₂ support calcined at 800 °C and the Nb₂O₅-Na support calcined at 500 °C presented the best results in ESR, both in terms of acidity, conversion and selectivity. While CeO₂ gives predominantly hydrogen and acetone, Nb₂O₅ produces mores ethylene. In the two cases, however, conversion is low ($\sim 15$ %), so that the undesired products generated by the supports may not impact too much the product mixture under the presence of an active metallic phase. Density functional calculations (DFT) show that the preference for ethylene formation in Nb₂O₅ comes from the thermodynamic stability of the products, but not directly from acidic catalysis.