A theoretical investigation into gallic acid pyrolysis
1Institute of Theoretical Physics, TU Bergakademie Freiberg, Freiberg, Germany.
Journal of Computational Chemistry
|April 23, 2022
Summary
Gallic acid pyrolysis involves decarboxylation and dehydrogenation. Dehydrogenation is the rate-limiting step, influencing reaction rates at high temperatures.
Area of Science:
- Chemical kinetics
- Thermodynamics
- Computational chemistry
Background:
- Gallic acid pyrolysis is a complex process with multiple reaction pathways.
- Understanding the thermodynamic and kinetic parameters is crucial for controlling pyrolysis outcomes.
Purpose of the Study:
- To elucidate the thermodynamic and kinetic profiles of the initial two steps in gallic acid pyrolysis.
- To identify the rate-determining step and transition states involved in gallic acid decomposition.
Main Methods:
- Density Functional Theory (DFT) and quantum chemistry calculations were employed.
- The climbing image nudged elastic band (CI-NEB) method was used to locate transition states.
Main Results:
- Two transition states were identified for each of the decarboxylation and dehydrogenation steps.
- Gallic acid pyrolysis is overall endothermal, shifting from endergonic to exergonic between 500-750 K.
- Dehydrogenation of pyrogallol was confirmed as the rate-determining step.
Conclusions:
- The study provides detailed thermodynamic and kinetic insights into gallic acid pyrolysis.
- Reaction rate constants for dehydrogenation remain below 1 s⁻¹ below 1250 K, indicating slow kinetics at lower temperatures.
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