Low temperature microwave pyrolysis of lignocellulosic materials for renewable fuels and chemicals

摘要

Microwave pyrolysis of lignocellulosic materials (cellulose, lignin, xylan, white birch) were investigated at the relatively low temperatures of 200-300ᴼC and low power of 300 W. Effects of temperature, microwave absorber (activated carbon and water), closed/open microwave, and cellulose crystallinity on yield and product distribution were examined. Microwave results were compared with higher temperature (250-475ᴼC) conventional pyrolysis using pyrolysis-gas chromatography. Results from both microwave and conventional method revealed that increasing temperature produced more bio-oil at the expense of biochar. Bio-oil yields with microwave pyrolysis from cellulose, xylan and white birch at 260ᴼC were 45%, 47%, and 17%, respectively, while lignin required microwave heating up to 280ᴼC to give only 4% yield. Torrefaction improved the quality of bio-oil but also increased the biochar yield while reducing bio-oil. High yields of useful levoglucosan were obtained from microwave pyrolysis of amorphous cellulose. Addition of the adsorbent water increased bio-oil production by 25%.