Microwave-assisted hot water treatment of sugarcane bagasse for fast pyrolysis

Pretreatment is an essential pathway to improve agro-based feedstock (sugarcane bagasse) for fast pyrolysis. The undesirable changes in the chemical composition and large amounts of alkali metals are obstacles in using common pretreatment process of sugarcane bagasse. To address this challenge, microwave-assisted hot water treatment (MW-HT) was introduced as an environment-friendly and low-cost pretreatment process. Other pretreatments such as sulfuric acid, formic acid, and hot water were compared with MW-HT at ambient temperature before pyrolyzing the treated bagasse at 500 °C in a tandem microreactor. Higher amounts of cellulose and hemicellulose derivatives including levoglucosan, furfural, and HMF were obtained with MW-HT, finding immense applications in polymer and chemical industries, while lignin-rich components such as phenols, guaiacol, benzene, and char formation increased with sulfuric acid pretreatment. The yield of compounds containing C5-C12 alkane chains increased significantly from 6.5 to 13.6% by weight through MW-HT, while the yield of compounds containing C5-C12 olefinic chains increased from 9.8 to 16.9% by weight for sulfuric acid pretreatment. In terms of compounds containing aromatic hydrocarbon yield, an increase from 3.2 to 10.1% by weight was obtained after applying formic acid pretreatment but was reduced to 5.7 wt% when hot water treatment was considered.