Interaction among cellulose, hemicellulose and lignin during pressurized pyrolysis: Importance of deoxygenation and aromatization reactions

Mild pressurized pyrolysis is an effective deoxygenation method for biomass to produce high-quality energy fuels with low power consumption, thereby contributing to environmental sustainability. However, the interactions among cellulose (C), hemicellulose (H), and lignin (L) during pressurized pyrolysis remain underexplored. Herein, response surface methodology (RSM) was used to rapidly identify synergies and predict optimal blend ratios. Results demonstrated that char properties, such as volatile matter and O/C ratio, were primarily affected by lignin and its interaction with cellulose/hemicellulose during pressurized pyrolysis at 200∼280 °C. Moreover, the impact of component interactions on products characteristics during pressurized and conventional pyrolysis was essential explored. C-L interaction significantly promoted deoxygenation and carbon enrichment in semi-char, especially pronounced under pressure. A strong promotion effect of C-L interaction was observed on the formation of aromatic = C-H groups and the condensation from small to large aromatic rings. GC-MS results showed a decrease in actual sugars and furfural content, especially furfural decreased from 3.95 % and 10.93 % to 1.04 % and 1.34 % in C-L-AP and C-L-GP, respectively. The peak area of phenols increased dramatically from 30.67 % and 42.82 % to 60.73 % and 57.37 %. Similarly, furfural content in H-L-GP decreased from 10.79 % to 7.67 %, with a slight rise in phenolic substances. H-L interaction under pressure had a limited promotion of aromatic substance formation. Accordingly, a synergistic deoxygenation and aromatization reaction pathway was proposed during co-pressurized pyrolysis of C-L and H-L. The production of green carbon-rich solid fuels from biomass raw materials is a significant goal of this effort.