Effect of lanthanum promoter on the catalytic performance of steam reforming of ethanol over ceria-supported catalysts

摘要

Fossil fuels, which are an indispensable source of energy in our daily lives, are causing serious environmental problems, such as emission of carbon dioxide and air pollutants, and are a depleting non-renewable energy source. Hydrogen has been considered an ideal candidate as an alternative energy source because it can be used to generate electricity in fuel cells with high efficiency and is environmentally friendly. As a feedstock for the production of hydrogen, alcohols are very promising candidates because they are readily decomposed in the presence of water, to generate a hydrogen-rich mixture at a relatively low temperature. The steam reforming of ethanol (SRE) is of particular interest because ethanol, obtained by the fermentation of biomass, has advantages from the environmental point of view. Cobalt and nickel are widely recognized for their catalytic activity in SRE reaction. These metallic phases favouring C-C bond and O-H bonds rupture, and C-O bonds generation. Also, they acting as oxygen carriers and are therefore used in chemical looping and autothermal reforming. However, the deactivation due to deposition of carbonaceous species on cobalt and nickel-based catalysts have promoted the development of different methods of synthesis, catalyst composition, incorporation of promoters, etc. in order to diminish such limitations. The addition of basic oxides (e.g. MgO, La_2O_3) can decrease the coke deposition rates through gasification of carbon; for example lanthanide oxide can facilitate the removal of coke deposits (formed in SRE) on the catalytic surface though formation of carbonate species which decompose readily during reaction [1-4]. Therefore, the aim of this work was to study effect of lanthanum promotion on the catalyst performance in SRE reaction and to verify its influence on activity, selectivity and coking of the cobalt- and nickel-based catalysts.