Active and stable Co catalysts supported on La-Si binary systems for H2 production through ethanol steam reforming

Abstract

Co catalysts supported on La2O3-SiO2 binary systems were used in the steam ethanol reforming reaction for the production of hydrogen. Calcined and used catalysts were characterized by different techniques, in situ Raman spectroscopy, XPS and HRTEM to determine the Co species present in the solids before and after the reaction. The Co catalysts were active and stable for H2 production. In order to improve catalyst stability and H2 production, the contact time (W/F) effect was studied (4.9 10−3 g h L−1 to 3.3 10−2 g h L−1). In the case of the catalytic measurements with lower W/F, the catalyst with 15 wt% of Co presented higher selectivity to H2. It was observed that a higher content of Co0 species increased the hydrogen yield, suggesting that metallic cobalt could be the active species in most of the parallel reactions that occur in the reforming of ethanol. In the solid with lower Co content, the low formation of carbon nanotubes produced a slight decrease of ethanol conversion with a decrease in the hydrogen yield. On the other hand, in the catalyst with higher cobalt content the carbonaceous deposits are of the amorphous type and the hydrogen yield equal to 3.5 remained constant with time on stream. The most active and stable catalyst with 15 wt% of Co was tested in a membrane reactor, obtaining a high H2 recovery of 54% under moderate reaction conditions (H2O/ethanol = 5, 500 °C and 1 bar).