INCAPE   05401
Unidad Ejecutora - UE
congresos y reuniones científicas
Effect of lanthana addition on cobalt based catalysts for hydrogen production via ethanol steam reforming
Santa Fe Capital
Congreso; VI San Luis Conference on Surfaces, Interfaces and Catalysis; 2018
Institución organizadora:
SPECS, Alexander Von Humboldt, aaiFQ, CONICET, UNL
Currently, most of the energy consumed comes from non-renewable sources, like fossil fuels. The dependence on these fuels has caused serious environmental problems, namely air pollutants, greenhouse gas emissions and natural resource depletion1. Hydrogen has been identified as an ideal energy carrier, demonstrating remarkable properties, i.e. it is completely carbon free and possess the highest energy content compared to any known fuel2. Ethanol steam reforming (ESR) is a promising production process for obtaining hydrogen from a renewable source, which requires an active, stable and H2 selective catalyst. Cobalt based catalysts are known for their capacity for C-C bond cleavage3 and its relative low prize compared to noble metals.In this work, Co based catalysts supported on lanthana-silica binary oxides were synthetized by incipient wetness impregnation, varying the La2O3 composition from 0 to 50 wt.%. The samples were characterized by several techniques (XRD, TPR, Raman, XPS) in order to elucidate the catalyst properties and correlate them with their catalytic behavior. The Co3O4 spinel was present and the appearance of the La2SiO7 phase was observed as the lanthanum concentration increased. In addition, a strong metal-support interaction was identified. The low surface composition of the active metal determined by XPS can be attributed to the impregnation method, as well as the high metal loading decreasing the surface dispersion of the metal. Moreover, a combination of oxidation states (Co+3, Co+2 and Co0) was found in the surface after exposing the samples to a H2 flow at 500 °C. The performance of the solids for the ethanol steam reforming reaction was investigated in a conventional fixed-bed reactor at 500 °C with a water/ethanol molar rate (R=5), using 20 mg of catalyst diluted in 70 mesh quartz (1:3). The catalytic results showed that for the best catalysts (with a La2O3 composition of 15 and 20 wt.%) hydrogen was the main product, while the CO concentration was below 10 %. The addition of La2O3 improves catalysts stability, but concentrations of La2O3 above 20 wt.% on the catalyst support, decreased the hydrogen selectivity. Similar results were obtained for catalyst supported on bare La2O34, demonstrating the influence of the support on the selectivity towards acetaldehyde, decreasing hydrogen yield. Characterization of used catalysts by XPS, Raman and TGA revealed the presence of two different carbon species and a different amount of total coke among the samples, indicating that lanthanum avoided catalysts deactivation by diminishing carbon deposition.