Overcoming bamboo recalcitrance via deep eutectic solvent pretreatment combined with pyrolysis for enhanced pyrolytic sugars

Renewable and short-season bamboo is a potential feedstock to produce pyrolytic sugars (e.g., levoglucosan) that can be upgraded into liquid fuels and chemicals. However, cellulose in bamboo is tightly intertwined with lignin and hemicellulose, forming a high recalcitrance and complex composition, resulting in hindering the effective release of levoglucosan during fast pyrolysis. The novel route of bamboo pretreated by deep eutectic solvents (DESs) coupled with fast pyrolysis was proposed for producing pyrolytic sugars. The results showed that the bamboo pretreated by choline chloride (ChCl)/formic acid (FA) produced the levoglucosan yield of 198.6 mg/g via fast pyrolysis, increased by about 43 times as compared to raw bamboo, while the relative contents of phenols and acids were significantly reduced. The characteristic analysis showed that the activation energy of the pretreated sample is in a direct proportional relationship with the crystallinity index. The change of crystallinity index and removal of lignin and AAEMs promoted the levoglucosan formation. This work provides an effective route to convert highly resistant lignocellulose into pyrolytic sugars via fast pyrolysis.