Unimolecular Decomposition Pathway for the Vapor-Phase Cracking of Eugenol, A Biomass Tar Compound

Abstract

To design optimal thermochemical processes for the conversion of biomass into chemicals, fuels, and electrical power, an understanding of the mechanisms for the secondary vapor-phase cracking of tar compounds is crucial. Despite the many studies examining the homogeneous secondary cracking of biomass tar existing in the literature, its thermal decomposition reaction pathways are not completely understood. Much of this lack of understanding is due to the complex, heterogeneous nature of biomass tar. A useful approach is to examine the pyrolysis of model-fuel compounds that are actual components or are representative of compounds found in biomass tar. In this study, we focus on eugenol, a model-fuel compound representative of the lignin-derived components found in biomass tar. We conduct pyrolysis experiments at temperatures of 300–900 °C and one second residence time using a non-isothermal laminar-flow reactor system. We report the variation in the experimental yield of light product gases as functions of the reactor temperature. We examine a reaction pathway for the unimolecular decomposition of eugenol with consideration of the experimental product distributions and analogous reactions based on established decomposition mechanisms of similar compounds. We examine the detailed energetics of the unimolecular decomposition route using computational chemistry calculations at the B3LYP/6-311G+(d,p) level of theory. The results presented in this study would be of relevance to the pyrolysis, gasification, and combustion of biomass.

Processed Lignin as a Byproduct of the Generation of 5‐(Chloromethyl)furfural from Biomass: A Promising New Mesoporous Material

“…Ledesma et al have discussed the mechanism of the thermal decomposition of the lignin model compound eugenol, in which they show computationally that the scission of the CÀO bond between the aromatic ring and the methoxy oxygen atom occurs with the formation of radicals. [24] Through as eries of cracking experiments,m ethanew as shown to form at temperatures above 450 8C, which supportedt he notion that the methyl radical, once formed, subsequently abstracted ahydroxyl hydrogen from eugenol. The phenoxyr adical then breaks down the arene ring by radical attack.…”

Gas phase conversion of eugenol into various hydrocarbons and platform chemicals

“…which can be signicant in the production of many specialty or platform chemicals. There has been a very few experimental studies 8,[12][13][14]24,25 on eugenol as the bio-oil model compound and only a single combined, i.e., both experimental and computational study 25 of eugenol as the bio-oil model compound is available in the literature to the best of authors' knowledge. For instance, Nimmanwudipong et al 13 carried out conversion reactions of eugenol in the presence of Pt/g-Al 2 O 3 and HY zeolite catalysts; and reported various products, e.g., phenol, guaiacol, veratrole, 4-propylguaiacol, 4-propylphenol, p-cresol, etc.…”

“…Chen et al 8 carried out hydrodeoxygenation of eugenol over carbon nanotube (CNT) supported ruthenium catalyst and reported propylcyclohexane as nal alkane product with 4-propylguaiacol and 4-propylcyclohexanol as intermediate products. A combined study of eugenol decomposition in vapour phase carried out by Ledesma et al 25 and they reported methane, ethylene, acetylene, propylene, benzene, CO, and 1-butene as the major products.…”

“…Finally, it can be understood from the literature review that eugenol component has been studied by a very few experimental researchers and only one computational work due to Ledesma et al 25 is available. However, Ledesma et al 25 carried out only one reaction pathway which initiated from the dehydrogenation of hydroxyl functional.…”

“…Finally, it can be understood from the literature review that eugenol component has been studied by a very few experimental researchers and only one computational work due to Ledesma et al 25 is available. However, Ledesma et al 25 carried out only one reaction pathway which initiated from the dehydrogenation of hydroxyl functional. Therefore, for the conversion of eugenol to various products, in this numerical study, we have carried out eugenol decomposition in gas phase by eight primary reaction schemes producing various important products such as propylbenzene, guaiacol, methylbenzene, propylcyclohexane, 4-propylphenol, allylbenzene, isoeugenol, and 2-methyl-4-propyl-phenol.…”