Abstract
The lignin pyrolysis products generated by biomass combustion make an essential contribution to the formation of secondary organic aerosols (SOAs). The ozone-initiated oxidation of guaiacol, syringol and creosol, major constituents of biomass burning, were investigated theoretically by using the density functional theory (DFT) method at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. Six primary addition reaction pathways and further decomposition routes with corresponding thermodynamic values were proposed. The Criegee intermediates can be excited by small molecules, such as NOx, H2O in the atmosphere, and would further proceed via self-decomposition or isomerization. The most predominant product for ozonation of guaiacol is the monomethyl muconate (P1). At 295 K and atmospheric pressure, the rate constant is 1.10 × 10−19 cm3 molecule−1 s−1, which is lies a factor of 4 smaller than the previous experimental study. The branching ratios of the six channels are calculated based on corresponding rate coefficient. The present work mainly provides a more comprehensive and detailed theoretical research on the ozonation of methoxyphenol, which aspires to offer novel insights and reference for future experimental and theoretical work and control techniques of SOAs caused by lignin pyrolysis products.
Highlights
Biomass refers to various organisms engendered by plants through photosynthesis
In order to gain a deeper understanding of the migration and transformation of methoxyphenol produced by biomass combustion, we presented initial reactions of guaiacol, syringol and creosol with ozone
We studied the reaction pathways of IM8 with NOx
Summary
Biomass refers to various organisms engendered by plants through photosynthesis. It is a renewable energy that is abundant, cheap and easy to obtain. Lignin burning produces extensive methoxyphenol [12], the most three of which are guaiacol, creosol and syringol in fresh wood smoke [13] They mainly exist in the gas-phase since they have relatively high vapor pressure at 25 ◦C [14]. Yang et al [18] illustrated the major degradation products of guaiacol, creosol and syringol with NO3 respectively and measured the corresponding reaction constants by using the relative rate method. These achievements provide guidance for approaching research work. In order to gain a deeper understanding of the migration and transformation of methoxyphenol produced by biomass combustion, we presented initial reactions of guaiacol, syringol and creosol with ozone. This work explored more profound reaction mechanisms and calculated the rate coefficient of guaiacol with ozone
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