Bimetallic Catalysts for Hydrogen Generation by Low Temperature Ethanol Steam Reforming

Abstract

The production of hydrogen through the low temperature-ethanol steam reforming (LT-ESR) reaction requires the development of an efficient catalyst. A bimetallic formulation, based on Pt and Ni and supported on CeO2 was investigated, in terms of activity, selectivity, stability. Very interesting results were obtained, with a complete ethanol conversion and a perfect agreement between the experimental and equilibrium products distributions, yet at T = 300 °C, contact time=240 ms and stoichiometric water/ethanol molar ratio. Furthermore, the selectivity towards the desired compounds was very high, with low coke selectivity and appreciable stability, especially with higher water/ethanol ratio. A mechanistic study of the reaction was carried out through the detailed analysis of the experimental evolution of the products distribution as a function of contact time (3 – 600 ms) and temperature (340 – 480 °C). The most significant result was the formulation of a possible Pt/Ni/CeO2 catalysed reaction pathway, that includes the following steps: ethanol adsorption followed by dehydrogenation to acetaldehyde; intermediate decomposition and reforming to CH4, CO, H2 and CO2; CO-WGS and CO2 methanation reaction. These outcomes were validated by specified characterizations of the exhaust sample, as temperature programmed desorption (TPD) experiments.