(469d) La2O3 Modified Ni/Gamma-Al2O3 Catalyst for Steam Gasification of Biomass Model Compounds In a CREC Riser Simulator
Biomass is a clean, renewable, CO2 neutral and abundant energy source. Catalytic steam gasification is a process able to convert low value solid biomass to a uniform gaseous mixture effectively and economically.
To accomplish this and in the context of the present study, Ni catalyst supported on La2O3 modified γ-Al2O3 was prepared via incipient wetness technique. BET results showed that calcination of γ-Al2O3 results in loss of surface area due to thermal sintering via phase transition towards the α-Al2O3. Addition of the lanthanum oxides decreased the loss of surface area, as it increases the thermal resistance of γ-Al2O3 by reducing the number of sites where nucleation of α-Al2O3 is possible. La2O3 also improved the reducibility by reducing the nickel-aluminate formation as well as dispersion of active phase as determined by TPR and H2 chemisorption experiments. The multiple cycles of TPR and TPO experiments proved that the prepared catalysts remains stable under repeated oxidation and reduction cycles, which are the conditions expected in an autothermal fluidized biomass gasifier unit.
Gasification of biomass model compunds glucose (cellulose) and 2-methoxy-4methylphenol (lignin) were conducted using the Ni/La2O3-γAl2O3 catalyst at different steam/biomass ratios, temperatures and reaction times in a CREC riser simulator. Significant improvements in dry gas yield and carbon conversion compare to the non-catalytic and catalytic gasification using Ni/α-Al2O3 catalyst at the same operating conditions confirmed the high activity of the developed catalyst for reforming of tars compounds, coke combustion and WGS reactions. The trends of gasification products (H2, CO, CO2, CH4, etc) with the variation of these parameters are in consistent with the thermodynamics predictions. With the increase in temperature, H2 and CO concentrations were increased while CO2 and CH4 concentrations were decreased. On the other hand, increasing CO2 and decreasing CO profiles were observed with the steam/biomass ratio and residence time due to WGSR. TOC analysis of spent catalyst showed negligible coke deposition.