Catalytic Conversion of Cellulosic Biomass to Ethylene Glycol: Effects of Inorganic Impurities in Biomass

The effects of typical inorganic impurities on the catalytic conversion of cellulose to ethylene glycol (EG) were investigated, and the mechanism of catalyst deactivation by certain impurities were clarified. It was found that most impurities did not affect the EG yield, but some non-neutral impurities or Ca and Fe ions greatly decreased the EG yield. Conditional experiments and catalyst characterization showed that some impurities changed the pH of the reaction solution and affected the cellulose hydrolysis rate; Ca and Fe cations reacted with tungstate ions and suppressed the retro-aldol condensation. To obtain a high EG yield, the pH of the reaction solution and the concentration of tungstate ions should be respectively adjusted to 5.0-6.0 and higher than 187ppm. For raw biomass conversion, negative effects were eliminated by suitable pretreatments, and high EG yields comparable to those from pure cellulose were obtained.