Subcritical water gasification of lignocellulosic wastes for hydrogen production with Co modified Ni/Al2O3 catalysts

Abstract

Nickel-based catalysts with different supports and cobalt loadings were synthesized for hydrothermal gasification of cellulose at 350 °C. The activity of Ni catalysts was found in the order of Al2O3 > spent bleaching clay ash > SiO2 with H2 yield of 80.6%, 69.0% and 57.0%. When 6 wt. % Co was added, 10Ni-6Co/Al2O3 showed the highest H2 yield of 88.4% i.e., 1.44 times that without Co addition. Catalysts were characterized by NH3-TPD, TPR, XRD, BET and XPS, showing that Ni-Co alloy formation promoted H2 production. Single-factor experiments were conducted to study variables in the presence of 10Ni-6Co/Al2O3 with the selected conditions of 0.5 g biomass and 20 min at 350 °C (achieving 94.9% H2 yield from cellulose) for gasification of rice straw, peanut shell and cotton straw with the increase in H2 yield by 51.4, 76.0 and 67.8 times. Ni-Co/Al2O3 catalysts enhanced hydrothermal gasification of actual agricultural residues.