In-situ reforming of biomass primary tars via reactive flash volatilization

Tar formation during biomass gasification has remained a major challenge. Using acetol and guaiacol as model tar compounds from cellulose and lignin, respectively, in-situ tar conversion into synthesis gas (H₂ and CO) was studied using a Rh–Ni/Al₂O₃ catalyst under reactive flash volatilization conditions. The influence of operating conditions, including temperature, steam-to-carbon molar ratio (S/C), carbon-to-oxygen molar ratio (C/O), gas hourly space velocity (GHSV), and catalyst weight, on the H₂/CO molar ratio in the product gas were experimentally examined. The contribution of non-catalytic thermal oxidation on overall conversion was also measured by varying the distance between the catalyst bed and the feeding point position. In the case of acetol reforming at 650 °C, more than 60% of the carbon in the feed was converted via thermal oxidation into permanent gases before reaching the catalytic bed. Moreover, a minimum reaction temperature of 500 °C was necessary to avoid coke formation and the optimal operating conditions for reforming of acetol were 650 °C, C/O = 1.7, S/C = 1.2, and atmospheric pressure. Likewise, for guaiacol, the minimum operating temperature of 600 °C was required. By using two pure components, this study has provided insight into how reactive flash volatilization generates tar-free synthesis gas.