Synthesis and evaluation of biochar-derived catalysts for removal of toluene (model tar) from biomass-generated producer gas

Challenges in removal of contaminants, especially tars, from biomass-generated producer gas continue to hinder commercialization efforts in biomass gasification. The objectives of this study were to synthesize catalysts made from biochar, a byproduct of biomass gasification and to evaluate their performance for tar removal. The three catalysts selected for this study were original biochar, activated carbon, and acidic surface activated carbon derived from biochar. Experiments were carried out in a fixed bed tubular catalytic reactor at temperatures of 700 and 800 °C using toluene as a model tar compound to measure effectiveness of the catalysts to remove tar. Steam was supplied to promote reforming reactions of tar. Results showed that all three catalysts were effective in toluene removal with removal efficiency of 69–92%. Activated carbon catalysts resulted in higher toluene removal because of their higher surface area (∼900 m2/g compared to less than 10 m2/g of biochar), larger pore diameter (19 A° compared to 15.5 A° of biochar) and larger pore volume (0.44 cc/g compared to 0.085 cc/g of biochar). An increase in reactor temperature from 700 to 800 °C resulted in 3–10% increase in toluene removal efficiency. Activated carbons had higher toluene removal efficiency compared to biochar catalysts.