Abstract
Hydrogen has been proposed as an energy carrier which could reduce atmospheric pollution, GreenHouse Gases (GHG) emissions, and dependency on fossil fuels.
In this context, one of the most environmentally friendly process for hydrogen production is ethanol steam reforming (ESR). In addition, the biomass-derived ethanol is renewable and also able to significantly reduce NOx, SOx emissions. Furthermore, ethanol is easier to reform than gasoline or natural gas as well as ready to be used in ESR reactions as an aqueous solution, thus, avoiding the water separation costs. When the reaction is carried out at low temperature, with the aim to reduce the thermal duty and promote the Water Gas Shift (WGS) reaction, the role of the catalyst is especially important. Various formulations have been proposed in literature but this work focuses on the development of innovative formulations; with this purpose, several CeO2-supported samples, based on the synergic activity of a noble and a non-noble metal, were investigated. The results showed that Pt can positively interact with Ni or Co, allowing the complete ethanol conversion, yet at T < 600 °C. The selectivity towards the desired compounds was one of the key parameters for the selection of the optimal catalyst, through specified tests in the following operating range: pressure=1 atm, temperature (300 – 600 °C), contact time = 240 – 720 ms, water-to-ethanol molar ratio = 3. Another central study was relevant to the stability of the sample, through Time-on- Stream (TOS) tests carried out at 430 °C and 10 vol.% of ethanol in the feed stream. The coke selectivity and coke formation rate were calculated and compared with current literature. The reaction pathway over the most interesting catalytic formulation was obtained, thanks to a detailed experimental campaign in which the evolution of the product distribution vs. contact time (0.600 ms) and temperature (300-600 °C) was analysed. In addition, the ethanol adsorption and the subsequent Temperature Programmed Desorption (TPD) experiments were performed. The results were also evaluated in terms of reaction rate, by considering the contribution of each possible reaction along the catalytic bed.
