Combined Gasification and Catalytic Methane Reformation for Enhanced Syngas Production from Biomass

Because of the growing threat of a changing climate and increasing energy demand, there is a need to investigate new energy solutions that are both clean and sustainable. Biomass gasification offers one such route, but presently there are several major drawbacks with gasification technology. The most significant of these pertain to the generation of low energy-dense products with a composition and C:H ratio that is not optimum for many downstream applications. To enhance the quality of syngas, a study was conducted to investigate the integration of gasification with catalytic methane reformation. Thermodynamic simulation with AspenPlus was completed for desired reactions, and catalyst characterization and lab-scale experiments were carried out for five catalysts: Ni/gamma-alumina, Ni-Co/gamma-alumina, Ni/alpha-alumina, Ni-Co/alpha alumina and commercially available HiFuel R110 (Alfa Aesar). Catalysts were characterized using SEM/EDS and temperature programmed reduction. Thermodynamic simulation indicates that syngas from biomass gasification can be enhanced to a H2:CO ratio of approximately 1.8 (from 1.0) with an energy content (HHV) 92% greater than original syngas. Experimentally, HiFuel was the most successful catalyst, increasing the H2:CO ratio to approximately 1.5 and HHV to 8.7 MJ/Nm3, 71% greater than original syngas. Stoichiometric bi-reforming at 950 °C for 8 hours (sampled every 15 minutes) was carried out for the HiFuel, Ni/alpha-alumina and Ni-Co/Alpha-alumina catalysts. For HiFuel, the steady state exit gas composition of H2 was 37.74% ± 0.18% and of CO was 24.86% ± 0.03% with a CH4 conversion of 81.57% ± 0.81% and CO2 conversion of 88.98% ± 0.50%. The promoting effect of calcium on thermal stability is postulated to most responsible for increased catalyst activity. Conversely, the bimetallic Ni-Co catalyst showed lowest activity in an 8-hour run, which was attributed to Co oxidation. Additionally, it was determined that at steady state there is no statistically significant (for p\u3c0.05) difference between alpha alumina and gamma alumina-supported catalysts with respect to hydrogen production. All results indicate that methane reformation coupled with biomass gasification is an effective tool for increasing the quality of produced syngas. However, future research can investigate mass transfer limitations and reactor conditions to further optimize desired syngas characteristics