Issue 13, 2022

Kinetic Monte Carlo simulations of the dry reforming of methane catalyzed by the Ru (0001) surface based on density functional theory calculations

Abstract

We combined first-principles calculations with kinetic Monte Carlo (kMC) simulations to study the dry reforming of methane catalyzed by the Ru (0001) surface. We considered adsorption/desorption reactions and a total number of 36 elementary steps with all rates obtained from periodic density functional theory (DFT)-based calculations. Our DFT results suggest that the CO2 cleavage occurs directly, leading to CO* and O*. The CO2 dissociation also has a lower energy barrier than the CH4 activation, while subsequent C–H activations leading to CH*/C* are easier than methane's first C–H cleavage. The O* produced by CO2 dissociation is the oxidant of C/CH* intermediates, leading to the formation of a second CO molecule. Graph-theoretical kinetic Monte Carlo simulations were subsequently carried out at different partial pressures and temperatures over 5 × 5 hexagonal periodic lattices considering various adsorption sites. In contrast to the DFT results, the kinetic Monte Carlo simulations suggest that the DRM reaction proceeds predominantly through the direct C* + O* route, with minor participation of the CH* + O* step. kMC simulations at different temperatures suggest an Arrhenius behavior for the catalytic system. We obtain an apparent activation energy of 78 kJ mol−1 within 700–800 K and at low pressure (0.32 kPa). Conversely, under typical conditions of dry reforming of methane (within 800–1023 K and at a total pressure of 100 kPa), we calculated an apparent activation energy equal to 158 kJ mol−1. Increasing the temperature also increases the calculated turnover frequency of the system and changes the coverage of species present on the catalytic surface. The inclusion of a pairwise O–O interaction is needed at the low pressure/temperature regime to avoid surface poisoning. The C–C interaction is also included at high pressures and temperatures since C* accumulates on the surface otherwise.

Graphical abstract: Kinetic Monte Carlo simulations of the dry reforming of methane catalyzed by the Ru (0001) surface based on density functional theory calculations

Supplementary files

Article information

Article type
Paper
Submitted
31 Dec 2021
Accepted
05 May 2022
First published
05 May 2022

Catal. Sci. Technol., 2022,12, 4350-4364

Kinetic Monte Carlo simulations of the dry reforming of methane catalyzed by the Ru (0001) surface based on density functional theory calculations

E. Díaz López and A. Comas-Vives, Catal. Sci. Technol., 2022, 12, 4350 DOI: 10.1039/D1CY02366G

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