Aqueous-phase reforming of model compounds of wet biomass to hydrogen on alumina-supported metal catalysts

Abstract

Catalytic aqueous-phase reforming (APR) of wet biomass such as microalgae and activated sludge is a potential technique for the production of H₂-rich gaseous products. In the present work, model compounds such as ethylene glycol, xylose and alanine were selected as representatives of the polyols, carbohydrates and proteins in wet biomass. APR trials were performed in a stirred batch reactor using commercial Pt/Al₂O₃ and Ru/Al₂O₃ catalysts. The reforming reactions were investigated at different conditions: temperature (T), 498 to 518 K, feed concentration, 1 to 5 wt. %, catalyst loading (ω), 2 to 6 kg/m³, and reaction time (t), 1 to 6 h. The commercial Pt/Al₂O₃ catalyst exhibited higher reforming activity. The influence of reaction parameters on turnover frequency (TOF_H₂), hydrogen yield (Y-H₂) and carbon-to-gas conversion (C to G conversion) was studied. The values of TOF_H₂ for Pt/Al₂O₃ were measured at T = 518 K, ω = 2 kg/m³ and t = 3 h using 1 wt% feed and these values were 19.2, 4 and 6 1/min for ethylene glycol, xylose and alanine. The values of TOF_H₂ over Ru/Al₂O₃ under identical conditions were: ethylene glycol–12.4, xylose–1.4 and alanine–5.4 1/min. The activation energies for H₂ production from ethylene glycol, xylose and alanine over Pt/Al₂O₃ and Ru/Al₂O₃ catalysts were determined. APR of the mixture of model compounds was also studied over laboratory-made Pt/Al₂O₃ and Ru/Al₂O₃ catalysts at the optimum reaction conditions. Thus, this work has provided crucial insights into the production of H₂ from model compounds of wet biomass using Al₂O₃-supported catalysts.