Fluidizable NiO–Fe 2 O 3 /SiO 2 –γAl 2 O 3 for tar (toluene) conversion in biomass gasification

Abstract

Abstract This communication reports synergetic effects of bimetallic Ni–Fe on NiO–Fe2O3/SiO2–γAl2O3 catalysts for biomass tar (toluene) conversion. The catalysts were successfully synthesized using a one-pot, solvent-deficient method and characterized using XRD, N2 adsorption isotherm and NH3-TPD techniques. The introduction of SiO2 enhanced thermal stability of the NiO–Fe2O3/SiO2–γAl2O3 catalysts, as observed in XRD and BET surface area analysis. The synthesized NiO–Fe2O3/SiO2–γAl2O3 catalysts showed high BET specific surface area (52–58 m2/g) even after calcination at 950 °C. The NH3-TPD analysis exhibited that the addition of NiO significantly decreased the strong acid sites of the NiO–Fe2O3/SiO2–γAl2O3 catalysts. The performance of the synthesized catalysts were evaluated in a fluidized CREC Riser Simulator using toluene as a tar model compound. The NiO containing NiO–Fe2O3/SiO2–γAl2O3 catalyst yielded high toluene conversion with higher H2 concentration in the produced gas, as compared to Fe2O3/SiO2–γAl2O3 catalyst. The presence of nickel promoted both methane reforming and water-gas shift reactions, contributed to higher H2 concentration in the producer gas. A gasification process model, as developed in Aspen Plus, also showed that hydrogen composition of the producer gas can also be enhanced by adjusting the gasification temperature, pressure and steam/biomass ratios. These results indicate that the NiO–Fe2O3/SiO2–γAl2O3 catalyst has a great potential for industrial use since it is a relatively cheap, less toxic, and stable for extended period of gasification operation. The spent catalyst materials are also useful to produce other commercial products, such as Portland cement and glass-ceramics.