Insights into the interactions between cellulose and hemicellulose during pyrolysis for optimizing the properties of biochar as a potential energy vector

Cellulose and hemicellulose, the main components of biomass, undergo noticeable interactions during biomass pyrolysis. In this study, biochar was produced by the co-pyrolysis of cellulose and hemicellulose. Three co- pyrolysis parameters, namely, pyrolysis temperature (400-800 degrees C), residence time (5-30 min), and percentage of cellulose (0-100 %), were investigated to optimize the properties of biochar, including the application of response surface methodology in the experimental study. The analysis revealed that co-pyrolysis interactions could improve the biochar yield by up to 41.37 % (567.74 degrees C, 19.52 min, 50 % cellulose percentage). The co- pyrolysis interactions specifically enhanced the fixed carbon content, elemental carbon content, and higher heating value of the biochar, with the most significant enhancements being 0.87 %, 3.60 %, and 3.85 %, respectively, while simultaneously decreasing the volatile content, [H]/[C] ratio, and [O]/[C] ratio of the biochar, with the most significant reductions of- 9.30 %,-10.81 %, and-26.71 %. Based on the observed decrease in the intensity ratio of the D-band and G-band of biochar in the Raman spectra, greater co-pyrolysis interactions increased the graphitization degree of the biochar. The analysis of X-ray photoelectron spectroscopy (XPS) investigations revealed that the interactions enhanced the contents of the C-C, C-O/C-O-C, aromatic, and OH functionalities while reducing the number of COO-, COOH, and C--O functional groups. The results of this work indicate that the co-pyrolysis interaction between cellulose and hemicellulose contributes to optimizing the properties of biochar as a potential energy vector.