The OH induced cellulose degradation was examined by analyzing the reaction products of Fenton’s regents with cellobiose. Many degradation products including C2-C5 compounds such as oxaldehyde, malonaldehyde and 2-hydroxysuccinaldehyde were detected by GC MS analysis. Four reaction pathways for the formation of some degradation products were obtained from ReaxFF kinetics simulation and validated by the DFT quantum chemistry calculation at B3LYP/6-31+g(d,p) level. It was found that the H-abstraction from OH of the glucose unit by OH can cause saccharide ring open and breakage of the glycosidic bond. Pathways 1–4 showed that the glucose unit can react with OH consecutively to produce small molecular products with carbon atoms less than 6. This study indicated that ReaxFF reaction kinetics is a powerful tool for the exploration of the degradation mechanism of cellulose induced by OH at room temperature, which correlated well with the experimental results and was validated by DFT calculation.
Wei Yu,Chao Liu,Luxi Tan,Qibin Li,Liyong Xin,Shukun Wang
The thermal stability and decomposition mechanism of octamethyltrisiloxane (MDM) were studied using a combination of experimental, ReaxFF simulation, and DFT calculation techniques. After heating MDM for 24 h at 250 °C and 1 MPa, the signature product CH 4 was detected, along with liquid products such as hexamethyldisiloxane (MM) and decamethyltetrasiloxane (MD 2 M). The decomposition rate of MDM remained relatively constant in the temperature range of 250 °C–320 °C but exhibited a sharp increase at 350 °C. Higher pressure was found to promote MDM polymerization. The oxygen (O) atoms displayed a large negative electrostatic potential , while the hydrogen (H) and silicon (Si) atoms exhibited a large positive potential. The electrostatic interaction facilitated the rearrangement reactions, with O and carbon (C) atoms being the most reactive for electrophilic and free radical reactions. The thermal decomposition of MDM initiated with the cleavage of Si–C bonds. Hydrogen extraction reactions between methyl radicals and MDM, as well as Si–O bond rearrangement reactions of demethylated radicals with MDM, further promoted MDM decomposition and the formation of CH 4 and siloxane oligomers . These findings are significant for the safe application of MDM as a working fluid in ORC system.
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