Theoretical Study on Elementary Reaction Steps in Thermal Decomposition Processes of Syringol-Type Monolignol Compounds

Abstract

This paper theoretically investigated a large number of reaction pathways and kinetics to describe the vapor-phase pyrolytic behavior of several syringol-type monolignol compounds that are derived from the primary pyrolysis of lignin: 1-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-en-1-one (HDPP), sinapyl alcohol, 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)propan-1-one (HHDPP), 1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol (HDPPD), and syringol. The possible pyrolytic pathways involving unimolecular decomposition, addition, and abstraction reactions were investigated by comparing the energy barriers calculated at the B3LYP/6-311++G(d,p) level. In the proposed pathways, all syringol-type monolignols containing a side chain undergo its cleavage to form syringol through the formation of syringaldehyde or 4-vinylsyringol. Syringol is then converted into two products: (a) pyrogallol via the homolysis of the O-CH bond and hydrogenation or (b) guaiacol via addition of an H atom with a carbon bearing methoxyl group in syrignol and the subsequent demethoxylation. The pyrolytic pathways of pyrogallol are classified into two processes: (a) the concerted dehydrogenation of the two hydroxyl H atoms and the unimolecular decomposition to produce acetylene (CH), ethynol (CHOH), and CO or (b) the displacement of an OH with H to produce catechol and resorcinol. Additionally, HDPP undergoes O-CH bond cleavage to form but-1-en-3-yne. The high-pressure limit rate constants for all the proposed elementary reaction steps were evaluated on the basis of transition state theory.

Detailed kinetics of substituted phenolic species in pyrolysis bio-oils

“…Furutani et al 32 theoretically investigated the pyrolysis behaviour of phenol-type monolignol compounds released from the primary heterogeneous pyrolysis of lignin. They observed that all these phenol compounds convert to phenol by sidechain cleavage at high temperatures, whereas the dominant channel below 1000 K produces cyclopentadiene species.…”

Measuring biomass fast pyrolysis kinetics: State of the art

“…These studies provide information on the dominant types of reactions involved such as concerted, free-radical, or ion-driven mechanisms. In addition, mechanistic studies describe the type of reaction intermediates and competing pathways involved in the product formation (Asatryan, Bennadji, Bozzelli, Ruckenstein, & Khachatryan, 2017;Bahrle, Custodis, Jeschke, van Bokhoven, & Vogel, 2014;Custodis et al, 2014;Furutani, Dohara, Kudo, Hayashi, & Norinaga, 2018;Khachatryan et al, 2016;Kibet, Khachatryan, & Dellinger, 2012;Kim, Bai, Cady, Gable, & Brown, 2015;Koirala, Villano, Carstensen, & Dean, 2013;Qi, Zhang, Kudo, Norinaga, & Hayashi, 2017;Seshadri & Westmoreland, 2012;Shen, Jarboe, et al, 2015;Wornat, Ledesma, & Marsh, 2001;Xu, Khachatryan, Baev, & Asatryan, 2016). Advances in analytical techniques have made it possible to even detect intermediate radicals and important product species (Bahng et al, 2009;Kanaujia, Sharma, Agrawal, & Garg, 2013;Michailof, Kalogiannis, Sfetsas, Patiaka, & Lappas, 2016;Negahdar et al, 2016;Pouwels, Eijkel, & Boon, 1989;Sarrut et al, 2015;Traore, Kaal, & Martinez Cortizas, 2016).…”

A Review on Detailed Kinetic Modeling and Computational Fluid Dynamics of Thermochemical Processes of Solid Fuels

“…Therefore, the elementary reaction rate constant of monolignol gas-phase decomposition was estimated on the basis of the quantum chemistry calculations and transition-state theory. Detailed chemical reaction models were also constructed for the pyrolysis process of resorcinol, catechol, guaiacol, syringol-based monolignol, and phenol-based monolignol …”

“…Therefore, the elementary reaction rate constant of monolignol gas-phase decomposition was estimated on the basis of the quantum chemistry calculations and transitionstate theory. Detailed chemical reaction models were also constructed for the pyrolysis process of resorcinol, 40 catechol, 41 guaiacol, syringol-based monolignol, 42 and phenol-based monolignol. 43 Therefore, a reliable prediction method for the thermochemical reaction of solid fuels that minimizes the amount of empirical information should be established in the future.…”