Enhancement of glucose gasification by Ni/La2O3-Al2O3 towards the thermodynamic extremum at supercritical water conditions

This communication presents the promotional effects of La on Ni/La-Al2O3 catalyst for biomass gasification in supercritical water using glucose as a biomass surrogate. The experimental findings were also compared with the product compositions predicted by the thermodynamic model. In modeling, the equations of state (EoS) by Peng-Robinson, as well as by Duan, were separately used to derive the residual Gibbs' free energy and compressibility factor, Z. Results, obtained by both EoS showed close agreement. The accuracy of our calculation was checked by comparing the compressibility factor, Z of the gaseous products, with those obtained from Aspen-HYSYS. In all cases considered, the percentage error in Z was less than 10%. Moreover, we have found that water to glucose (W/G) ratio affects the syngas composition. For example, at 600 °C and 25 MPa, an increase in W/G ratio from 6 to 9 led to an increase in H2/CO ratio from ∼3.2 to ∼4.7. On the other hand, operating pressure has little effect on syngas composition. This finding could be useful in the design and optimization of supercritical water gasification (SCWG) plants. Finally, we also observed that lanthanum helped to drive the hydrogen yield towards the thermodynamic extremum, while at the same time scavenging CO2 and coke, and retarding the methanation reaction.