Pyrolysis of α-cellulose using a multimode microwave oven

•Pyrolysis of cellulose was run using a multimode microwave oven.•High yield of bio-oil was reached with iron as MW absorber.•Large gasification was obtained using carbon as MW absorber.•High char production was realized with alumina as MW absorber.•Water was formed in low amount using silica as MW absorber.

α-Cellulose was pyrolyzed using a multimode microwave oven, different microwave absorbers and experimental set ups. The microwave absorber showed a strong influence: carbon gave a large gasification of cellulose (yield of gas up to 53.8%) while Al2O3 gave a high yield of bio-char (64.1%) and a low gas production (3.0%). Bio-oil was obtained with the highest yield (37.6%) using iron as microwave absorber and a condenser between the oven and the collecting system. Dark brown bio-oils having low density and viscosity due to the presence of large amount of furanosidic compounds were collected. Bio-oils were characterized through GC–MS, FT-IR, NMR, The GC–MS analysis was employed to evaluate the composition of bio-oils using calculated retention factors. A high concentration of levoglucosan (133.9 mg/mL) together with acetic acid, acetic anhydride, 1-hydroxy-2-propanone, formic acid and furfural were obtained using graphite as microwave absorber. A mechanisms was proposed to rationalize the formation of aromatic compounds present in bio-oils. Water contents in bio-oils were affected by all parameters of the process, mainly by the microwave absorber. The use of silica has proved to be a promising way to obtain bio-oil with low water content (13%), while pyrolysis in the presence of carbon gave a large amount of water (46%).