Low-temperature CO oxidation over Rh/Al<sub>2</sub>O<sub>3</sub> in a stagnation-flow reactor

Alghamdi, Nawaf M.; Gautam, Ribhu; Gascón, Jorge; Vlachos, Dionisios G.; Sarathy, S. Mani

doi:10.1039/d2re00235c

Cited by 4 publications

(21 citation statements)

References 54 publications

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“…Table shows the surface reaction mechanism we propose for the CO/O 2 system over 5 wt % Rh/Al 2 O 3 . The sticking coefficients for reactions – were taken from the literature. ,− The activation energy of reaction was lowered by 6.6 kcal/mol to capture the experimental reactivity, a change not far outside the typical error of DFT calculations . This change was based on the CO conversion sensitivity analysis, which revealed reaction to be the most sensitive.…”

Section: Resultsmentioning

confidence: 99%

“…Model prediction of reactivity at 250 °C (a) and 225 °C (b) under 20 SLM of total gas flow (corresponding to 13 cm/s) and a CO/O 2 ratio of 2:1. The model prediction is shown in solid lines, and the experimental data are shown in symbols and taken from Alghamdi et al …”

Section: Resultsmentioning

confidence: 99%

“…The simulated parameters include the density, strain rate, axial velocity, mixture binary diffusion coefficient of CO, Reynolds number, and kinematic viscosity vs the distance from the stagnation disk. The experimental conditions are 0.6 bar (at 20 and 30 standard liter per minute (SLM)) and 0.8 bar (at 20 and 30 SLM) . In all of the nonreactive simulations, the temperature was fixed at 250 °C.…”

Section: Methodsmentioning

confidence: 99%

“…The kinetic parameters were determined using the Python Multiscale Thermochemistry Toolbox (pMuTT) software, developed by Vlachos and co-workers. The subset of DFT data used was on Rh(110), which is the dominant facet for the Rh catalyst, as determined by X-ray diffraction . The same DFT calculations were used to determine the energy barrier dependence on CO coverage.…”

Section: Methodsmentioning

confidence: 99%

“…We utilized a stagnation-flow reactor configuration, which is a one-dimensional (1D) problem and enables more accurate kinetic mechanism estimation and validation. Details of the experiments and reactor setup can be found elsewhere …”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Microkinetic Modeling of the CO Oxidation over Rh/Al₂O₃

Alghamdi

Vlachos

Sarathy

2023

Ind. Eng. Chem. Res.

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Carbon monoxide (CO) results in the deaths of millions every year. Much of the transportation-related CO emissions in the U.S. are from light-duty vehicles equipped with three-way catalysts containing Pt and Rh. While spark-ignition engines are more efficient under fuel-lean operations, the current microkinetic mechanisms for CO oxidation on Rh are limited to predicting a stoichiometric CO and O2 feed. In this work, we present a thermodynamically consistent, density functional theory (DFT)-based parametrized microkinetic model that predicts CO oxidation on Rh at stoichiometric and lean conditions. We demonstrate the model’s versatility by accurately simulating experimental data at different temperatures, flow rates, and inlet compositions. We then show that the model can predict literature data collected under vastly different conditions. We utilize sensitivity analysis to determine the key reactions. Additionally, we study the surface affinity to oxygen and the lack of coke formation. This microkinetic mechanism can enable optimizing three-way catalysts to reduce CO emissions further and propose cheaper alternative catalysts.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revisiting the Microkinetic Modeling of the CO Oxidation over Rh/Al₂O₃

Alghamdi

Vlachos

Sarathy

2023

Ind. Eng. Chem. Res.

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Deposited PtGe Clusters as Active and Durable Catalysts for CO Oxidation**

Ugartemendia,

Mercero,

de Cózar

et al. 2024

ChemCatChem

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Control of CO emissions raises serious environmental concerns in the current chemical industry, as well as in nascent technologies based on hydrogen such as electrolyzers and fuel cells. Pt remains one of the state‐of‐art catalysts for the CO oxidation reaction, but suffers from CO self–poisoning. Recently, PtGe alloys were proposed as an excellent alternative to reduce CO poisoning. In this work we investigate the impact of Ge content on the CO oxidation kinetics of P4Gen subnanoclusters supported on MgO. Pt−Ge nanoalloys act as a bifunctional catalyst by displaying dual adsorption sites; i.e., CO is adsorbed on Pt whereas oxygen binds to Ge, forming an alternative oxygen source GeOx. Besides, Ge alloying modifies the electronic structure of Pt (ligand effects) and reduces the affinity to CO. In this way, the competition between CO and O2 adsorption and the overbinding of CO is alleviated, achieving a CO poisoning−free kinetic regime. Our calculations suggest that Pt4Ge3 is the optimal catalyst, evidencing that alloying composition is a parameter of extreme importance in nanocatalyst design. The work relies on global optimization search techniques to determine the accessibility of multiple structures at different conditions, mechanistic studies and microkinetic modelling

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