Microwave pyrolysis of cellulose at low temperature

•Bio-oil, biochar and gas can be easily produced from microwave pyrolysis of cellulose at low temperatures (200–280 °C).•The highest bio-oil yield (45%) from microwave pyrolysis of cellulose was obtained at 260 °C.•Water and activated carbon were used as microwave absorbers and had significant influences on product yields.•Amorphous cellulose gave significantly higher amounts of levoglucosan than from microcrystalline cellulose.

Microwave pyrolysis of cellulose was successfully achieved at low temperature (200–280 °C) using a lab-scale microwave synthesis system. Both closed and open microwave setups were developed to measure yields of pyrolysis products and to characterize the bio-oil. The effect of temperature, type of cellulose (crystalline and amorphous), and microwave absorber were examined. Microwave-derived bio-oil compositions were compared to conventional pyrolysis (microfurnace pyrolyzer–GC/MS) under similar heating rates. Maximum bio-oil yield (45%) was obtained from amorphous cellulose at 260 °C using an open system. Addition of water significantly increased the bio-oil yield to 52% (amorphous) and to 47% (crystalline) while addition of activated carbon had the effect of increasing gaseous products. Microwave-derived bio-oil products varied in chemical nature and abundance depending on cellulose crystallinity and between open or closed microwave pyrolysis and showed significant differences from conventional pyrolysis bio-oil. High yields of levoglucosan were obtained from amorphous cellulose at 260 °C while conventional pyrolysis required a much higher temperature (400 °C).