Highly dispersed and stable Ni catalysts for hydrogen production by steam reforming of ethanol

Abstract

Highly dispersed Ni/CeO2-SiO2 catalysts were synthesized by incipient wetness impregnation using silica previously modified with ethylene glycol (EG). Their catalytic activity in the steam reforming of ethanol for hydrogen production was evaluated in a fixed-bed reactor at 500 °C. Different characterization techniques such as XRD, TEM, XPS, in-situ DRIFT, TPR and TPO were used to analyze the textural properties, morphology, particle interaction, and carbon deposition of the catalysts. The results indicated that EG functionalization could modify the nature of the Si-OH sites and also the CeO2 structure. The Ni species, which may be anchoring on the ceria sites, present an average particle size of 2.5 nm. A uniform and well-distributed spherical geometry nanoparticle was present in the EG modified catalyst. In addition, the reducibility and dispersion of the nickel on the surface were also favored. In this way, more active, stable, and selective catalysts for H2 production were obtained. A 100 % ethanol conversion was achieved during 24 h of reaction with a hydrogen yield of around 3.6 mol H2/mol ethanol on the Ni/CeO2-SiO2(EG) catalyst.The catalyst reactivity was also studied by in-situ DRIFT measurements during the ESR reaction, showing that the oxidation of acetaldehyde is favored as a possible reaction pathway in these Ni-based materials. Finally, the work also includes preliminary results for the potential application of the modified catalyst in the sorption-enhanced steam reforming of ethanol (SESRE) reaction using a CaO-derived sorbent (CaO/Ca12Al14O33), in which the purity of H2 was increased compared to the conventional reforming.