(639r) Mechanistic Study of Guaiacol Fast Pyrolysis Using DFT Calculations, Microkinetic Model and Experiments
- Conference: AIChE Annual Meeting
- Year: 2017
- Proceeding: 2017 Annual Meeting
- Group: Topical Conference: Thermal Deconstruction of Biomass
- Time: Wednesday, November 1, 2017 - 6:00pm-8:00pm
In this study, theoretical, kinetic and experimental analysis of fast pyrolysis of guaiacol, which is a model monomeric compound of lignin, was investigated. Fast pyrolysis experiments were carried out in micropyrolyzer and the evolved vapors were analyzed in gas chromatography-mass spectrometer. Experiments were conducted at different temperatures from 450 to 650 oC for high heating rate (> 1000 oC/s). The effect of temperature (450-650 oC) on the yield of phenolic compounds was studied. The main products from the pyrolysis of guaiacol were catechol, 2-hydroxybenzaldehyde, o-cresol, and phenol. The results suggested that conversion of guaiacol (27.7 to 100 %) increased with increasing temperature from 450 to 650oC. The maximum yield of catechol (23.7 %) was observed at 600oC. The highest phenol yield (10.8 %) was observed at 650oC. The decomposition of the primary products seems to have occurred via dehydration, decarboxylation, demethylation, demethoxylation, dehydroxylation, decarbonylation and radical rearrangement reactions. Based on the experimental results, the reaction mechanism of fast pyrolysis of guaiacol was formulated. Thermodynamic and kinetic analysis of 19 reactions were theoretically investigated by using density functional theory methods at B3LYP /6-31++G (d, p) level. The kinetic parameters (Arrhenius activation energy and pre-exponential factor) of 19 reactions were theoretically calculated. The homolytic cleavage of O-CH3 bond was the initial reaction in the reaction mechanism of pyrolysis of guaiacol, due to its low bond dissociation energy (52.9 kcal/mol). The effects of temperature (450-650oC) and residence time (0-600 s) on product yields were evaluated by solving the rate equations of a detailed kinetic model. From the results, it can be concluded that the experimental and simulation trends are inline but the yields are different due to different operating conditions used and evaluation of the limited number of reactions. Even though the evaluation of limited number of reactions used in this study, the major products from the fast pyrolysis of guaiacol were captured.
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