HYDROGEN PRODUCTION THROUGH GLYCEROL STEAM REFORMING REACTION USING TRANSITION METALS ON ALUMINA CATALYSTS

摘要

Hydrogen can be produced from a wide variety of primary energy sources and by applying quite different technologies. For a long period of time it has been considered as a sustainable and environmentally friendly alternative to conventional fossil fuels, with a large potential that can meet energy requirements, ensuring future supplies. At present, research is mainly focusing on biomass and biomass-derived fuels that can be used for the production of hydrogen through thermo-chemical or biological processes.On the other hand, biodiesel production has recorded enormous growth in the last decade, which has led to a simultaneous co-production of glycerol. As a consequence, finding alternative feasible uses for glycerol has become imperative as such processes would not only solve the environmental problems associated with its disposal, but also, the discovery of new and innovative uses for glycerol would greatly increase its market demand. Thus, the development of new uses for glycerol is the subject of heightened research interest.The production of hydrogen from biomass-model compounds including glycerol via low temperature catalytic aqueous phase and steam reforming has been investigated. Steam reforming (SR) is a highly energy efficient technology and can be carried out at atmospheric pressure. Glycerol steam reforming reaction (GSR) has intensively been studied experimentally using a variety of supported catalysts. Nickel (Ni) is the most investigated active metal in the GSR reaction, due to its well known property to promote the necessary C-C rupture. Nickel catalysts were shown to be active and selective with a strong dependence on the reaction temperature with glycerol conversion to gaseous products.In this contribution a systematic study of supported on y-alumina transition metals', catalytic performance is reported. Catalysts with active phase nickel (Ni), cobalt (Co) and copper (Cu) were synthesized via the incipient wetness impregnation method (dry impregnation) at a series of constant loading (8wt%). The synthesized samples, at their calcined or/and their reduced form, were characterized by the X-Ray Diffraction (XRD) and the N_2 adsorption-desorption techniques. The chemical composition of the catalysts was determined by inductively coupled plasma emission spectroscopy (ICP), while the deposited on their surface carbon during the reaction was measured by a CHN analyzer. Catalytic performance for the glycerol steam reforming reaction was studied in order to investigate the effect of reaction temperature on: (i) glycerol total conversion, (ii) glycerol conversion to gaseous products, (iii) hydrogen selectivity and yield, (iv) selectivity of gaseous products, (v) selectivity of liquid products.It was concluded that all catalysts were active with glycerol conversion values ranging from 75% to 95% for the studied reaction temperatures. However, the Ni/AI catalyst reveals higher conversion to gaseous products, improved hydrogen yield and selectivity especially for T>500 and less carbon deposited on its surface compared with the Co/AI and Cu/AI catalysts.