From Woody Biomass to Ethylene Glycol: Inorganics Removal Boosts the Yield

Tungstate-catalyzed hydrogenolysis of sugars in untreated woody biomass to ethylene glycol (EG) has so far been unsuccessful. This work shows that production of EG is predominantly hampered by the presence of inorganic impurities in the biomass, which can be selectively removed by an acid leaching step at room temperature. Catalytic hydrogenolysis of untreated and acid-leached samples of woody biomass was run at 245 °C using sodium polytungstate and Raney Ni catalysts at low loadings, which make them sensitive to deactivation by biomass impurities. Acid-leached pine and poplar samples gave a combined glycol yield (ethylene glycol + propylene glycol) of ∼44 wt %, similar to microcrystalline cellulose, whereas their untreated counterpart only delivered a yield of 22 wt %. Measurement of the dissolved fraction of the homogenous tungstate catalyst, i.e., active, after the experiment was found to be a key predictor of the EG yield: inorganic contaminants, such as calcium, are indeed shown to precipitate the tungstate catalyst