In situ generation of Ni metal nanoparticles as catalyst for H2-rich syngas production from biomass gasification

The strategy of impregnating lignocellulosic biomass with aqueous metal salts solutions was efficiently applied in our group for producing H2-rich gas by pyrolysis of wood at 700 °C. The present work is a thorough study on the formation of nickel metal nanoparticles (NPs) during the pyrolysis of nickel(II) impregnated wood in the temperature range of 400–500 °C. During the wood impregnation step, the numerous oxygenated groups present in the bio-macromolecules act as adsorption sites for metal cations in aqueous medium yielding very high metal precursor dispersion into the wood matrix. During pyrolysis, an amorphous NixOyHz phase is formed which is reduced to metallic nickel (Ni0) by carbon atoms at temperatures below 500 °C, leading to the formation of Ni0 NPs, as demonstrated by XRD, XPS, STEM and temperature-programmed pyrolysis characterizations. These findings reveal that the in situ formed Ni0 nanocrystallites act as the catalytic active phase for enhancing both H2 production and tar conversion during biomass pyrolysis, i.e. during the initial stage of gasification. Potential interests of these in situ generated Ni nanocatalysts for biomass gasification applications are discussed.

Graphical abstractDuring wood impregnation with nickel nitrate aqueous solution, specific adsorption of Ni2+ cations on oxygenated groups of wood surface occurs and leads to high metal dispersion inside the solid fuel matrix. During pyrolysis, nickel(II) species are reduced by carbon atoms yielding Ni0 nanoparticles which can act as the catalytic active phase for tar conversion and H2 production in biomass gasification process.Figure optionsDownload full-size imageDownload high-quality image (70 K)Download as PowerPoint slide