Catalytic steam gasification of biomass for a sustainable hydrogen future: Influence of catalyst composition

Hydrogen is regarded as a clean energy for fuelling the future. Hydrogen will be the energy carrier from other resources such as hydropower, wind, solar and biomass. Producing hydrogen from gasification of biomass wastes, particularly in the presence of steam, represents a promising route to produce this clean and CO₂-neutral fuel. The steam pyrolysis-gasification ofbiomass (wood sawdust) was carried out with various nickel-based catalysts for hydrogen production in a two-stage fixed bed reaction system. The wood sawdust was pyrolysed in the first reactor and the derived products were gasified in the second reactor in the presence of the catalyst and steam. The synthesised Ni-Ca-Al and Ni-Zn-Al catalysts were preparedbyco-precipitation method with different Ni loadings of 20 mol% and various Zn/Al or Ca/Al ratios, which were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO). The results showed that the Ni/Zn-Al (1:9) catalyst resulted in higher hydrogenproduction(23.9 mmol H₂ g^-1biomass)compared with the Ni/Ca-Al (1:9) catalyst (12.7 23.9 mmol H₂ g^-1 biomass) and in addition, the increase of Ca or Zn content in the catalyst slightly increased the hydrogen production. The TPO results showed that the catalyst suffered negligible coke deposition from the catalytic steam pyrolysis/gasification of wood sawdust. Additionally, Na₂CO₃ basic solution was also found toproduce a catalyst with better performance and lower coke deposition, compared with NH₄OH catalyst preparation agent, as observed by TPO, SEM and TEM analysis.