Effects of inherent potassium on the catalytic performance of Ni/biochar for steam reforming of toluene as a tar model compound

Reforming of biomass-derived producer gas using toluene as model tar: Deactivation and regeneration studies in Ni and K-Ni catalysts

Within the syngas production from biomass gasification, tar removal constitutes a chief issue to overcome for advanced catalytic systems. This work investigates the performance of Ni and Ni-K catalysts for reforming of derived-biomass producer gas using toluene as model tar. At 750 °C and 60Lg-1h-1, the stability test (70 h) revealed stable performances (CO2, CH4 and C7H8 conversions of 60, 95 and 100%, correspondingly) uniquely for the Ni-K catalyst. Although the efficient protection towards coking let by K was demonstrated, TPO studies over the post-reacted systems still evidenced the presence of carbon deposits for both samples. Conducting three successive reaction/regeneration cycles with different gasifying agents (air, steam and CO2) at 800 °C for 1h, the capability towards regeneration of both catalytic systems was assessed and the spent catalysts were characterized by XRD, SEM and TEM. While none of the regeneration treatments recovered the performance of the unpromoted catalyst, the Ni-K catalysts demonstrated the capability of being fully regenerated by air and CO2 and exhibited analogous catalytic performances after a series of reaction/regeneration cycles. Hence, it is proved that the addition of K into Ni catalysts not only enhances the resistance against deactivation but enables rather facile regenerative procedures under certain atmospheres (air and CO2).

Highly efficient and durable syngas production over one-step synthesized synergistic oxygen carriers in biomass chemical looping gasification

Biomass chemical looping gasification (BCLG) gives a promising platform for cost-effective and low-polluting syngas production. To overcome the cumbersome process and poor dispersion of two-step synthesized synergistic oxygen carriers (OCs), NiO-LaFeO3 synergistic OCs were synthesized in one-step by sol-gel method with the found best Ni introduction amount of 0.5. The high lattice oxygen mobility and powerful oxidation capacity derived from the Ni-Fe synergistic effect made it perform better in the BCLG reaction. Due to the extraordinary stability of crystalline phase and oxygen activity, its reactivity did not suffer from any degradation during the 50 long-time redox cycles over 2750 min under the optimal working conditions of the ex-situ configuration, mutual mode and steam/biomass mass ratio of 5.0. The gas yield, carbon conversion, syngas selectivity and H2/CO ratio were constantly maintained around 1846.45 mL/g, 86.74%, 79.96% and 2.0, respectively. This study provides a feasible technical route for highly efficient and durable syngas production.

Hydrogen-rich syngas production from biomass gasification using biochar-based nanocatalysts

Nanocatalysts are beneficial for tar elimination and syngas production during biomass gasification. In this study, novel biochar-based nanocatalysts loaded with Ni/Ca/Fe nanoparticles was prepared by one-step impregnation method for catalytic steam gasification of biomass. Results showed that the metal particles were evenly distributed with the particle size of less than 20 nm. With the introduction of nanoparticles, H₂ yield and tar conversion were obviously increased. Ni and Fe particles help to maintain the stability of the carrier microporous structure. Fe loaded biochar showed the best catalytic gasification performance, with 87% tar conversion and 42.46 mmol/g H₂ production. The catalytic effect of Fe was also higher than that of Ni and Ca if deducting the influence of carrier consumption. It demonstrated that Fe-loaded biochar was a promising catalyst candidate for hydrogen-rich syngas production from biomass gasification.