Pyrolytic characteristics of hemicellulose, cellulose and lignin under CO2 atmosphere

To understand the influence of CO2 on biomass pyrolysis, the pyrolysis behavior of hemicellulose, cellulose, and lignin with CO2 were investigated by thermogravimetric analysis and a fixed-bed reactor. The detailed formation behavior of the pyrolysis products (chars, liquids, and non-condensable gases) was monitored and characterized to determine the role of CO2. The char and liquid yield of the three components were higher under CO2 than under N-2 below 650 degrees C. For hemicellulose, more C elements were released as CO (from 1.25 mol% to 10.56 mol %) but the char yield decreased from 22.00 wt% to 10.50 wt% at 750 degrees C and the yield of ketones and furans was reduced. For cellulose, the yield of levoglucosans, furans, and ketones increased, but the yield of CO decreased (from 3.98 mol% to 3.10 mol% at 750 degrees C). For lignin, the selectivity of alkoxy phenols (G/S) increased whereas simple phenols decreased with more O elements released as CO (from 1.70 mol% to 3.41 mol% at 750 degrees C). For solid char, all samples exhibited more C=O and COO groups with CO2 at 750 degrees C.