Evaluation of thermal pyrolysis characteristics and kinetic parameters of cellulose extracted from date waste using natural deep eutectic solvent

Abstract

Natural deep eutectic solvent (NADES) composed of choline chloride and formic acid was used to fractionate date waste into lignin and cellulose streams. NADES treatment increased the cellulose content from 44 wt% in raw waste (RW) to 72 wt% in extracted cellulose fibers (CFs). Scanning electron microscopy revealed needle-like fibers, underlining the effectiveness of NADES treatment in removing non-cellulosic components. Additionally, the CFs exhibited improved thermal stability, with an initial decomposition temperature ($T_{onset}$) of 265 °C. Kinetic analysis revealed a higher activation energy ($E_a$) of 100.90 kJ/mol for CFs than 63.10 kJ/mol for RW, indicating higher thermal stability due to enhanced cellulose content. Pyrolysis coupled with gas chromatography/mass spectroscopy analyses of CFs showed a lower release of nitrogen compounds and a higher content of hydrocarbons and cyclic ethers, all of which are beneficial for bio-oil production. Overall, the findings of this study will promote the use of NADES as an inexpensive, nontoxic, and recyclable solvent to advance the field of selective pyrolysis.