Thermal stability and thermal decomposition mechanism of octamethyltrisiloxane (MDM): Combined experiment, ReaxFF-MD and DFT study

Wei Yu, Chao Liu, Luxi Tan, Qibin Li, Liyong Xin and Shukun Wang

Energy, 2023, vol. 284, issue C

Abstract: 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 CH4 was detected, along with liquid products such as hexamethyldisiloxane (MM) and decamethyltetrasiloxane (MD2M). 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 CH4 and siloxane oligomers. These findings are significant for the safe application of MDM as a working fluid in ORC system.

Keywords: MDM; Thermal stability; Pyrolysis mechanism; Experiment; ReaxFF; DFT (search for similar items in EconPapers)
Date: 2023
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Citations: View citations in EconPapers (4)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:284:y:2023:i:c:s036054422302683x

DOI: 10.1016/j.energy.2023.129289

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