Production of pure hydrogen by ethanol dehydrogenation.

Hydrogen production from bio-ethanol is one of the most promising renewable processes to generate electricity using fuel cells. In this work, we have studied the production of pure hydrogen as a by-product of the ethanol dehydrogenation reaction. This reaction is promoted by copper based catalysts and according to the catalyst used and the operating conditions gives place to acetaldehyde or ethyl acetate as main products. We studied in particular the performance of a commercial copper/copper chromite catalyst, supported on alumina and containing barium chromate as a promoter, which gave the best results. By operating at low pressure and temperature with short residence times, acetaldehyde is more selectively produced, while, by increasing the pressure (10– 30 bars), the temperature (200–260 °C) and the residence time (about 100 grams hour/ mol of ethanol contact time) the selectivity is shifted to the production of ethyl acetate. However, in both cases pure hydrogen is obtained, as a by-product, which can easily be separated. Hydrogen obtained in this way is free of CO and can be directly fed to fuel cells without any inconvenience. In this work, runs performed under different operating conditions have been reported with the scope to select the best conditions. A carrier of H2 6% in N2 has been used. The studied catalyst has also shown a good thermal stability with respect to sintering phenomena, which generally occur during the dehydrogenation over other copper catalysts. Hydrogen productivities of 8–39 gH2 (Kgcat)–1 (h)–1 were obtained for the explored temperature range of 200–260 °C. Finally the most accredited reaction mechanism is reported and discussed on the basis of the obtained results.