Multiscale kinetic modeling in catalysis ⇒ from microkinetics to computational fluid dynamics and process simulations

Problem statement

We envision multiscale modeling as critical enablers of reaction understanding, catalyst and reactor design, scale-up, and process optimization. The framework includes predicting the molecular reaction mechanism at the molecular level to the process optimization stage. As catalytic processes occur at the multiscale, we address these issues individually and collectively.

At the microkinetic level, our models resolve the rates of the individual elementary steps, rate-determining step (RDS), adsorption, and desorption mechanisms. We use quantum chemical calculations (density functional theory, DFT) to support our assumed kinetic pathways, original parameter estimations, and adsorption-desorption energies.

We incorporate thermodynamic constraints into our models. Once developed, the microkinetic model could guide the catalyst and reactor design. We also have experience developing Langmuir-Hinshelwood and Eley-Rideal types of kinetic models.

At the macrokineitc level, we develop lump-based and empirical models which, in some cases, are very robust and, together with other models, can be used to extract information such as mechanism change, optimize conditions, or for reactor pre-design.

We couple hydrodynamics, heat transfer, and reaction kinetics at the reactor level in computational fluid dynamic (CFD) simulations. Together with optimization algorithms, we aim to improve operating scenarios, develop innovative reactor prototypes, and predict process behaviors at the industrial scale.

Goals

  • Microkinetics I ⇒ key thermodynamic relationships
  • Microkinetics II ⇒ fitting, training, and optimization
  • Microkinetics III ⇒ ab initio kinetic modeling
  • Macrokinetics ⇒ complex reaction networks and population balances
  • CPFD ⇒ reactor modeling and scale-up
  • CFD ⇒ reactor modeling and optimization
  • CFD II ⇒ modeling operando reactors
  • Process system engineering ⇒ gPROMS

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Mechanistic and kinetic effects of Ga on a Cu catalyst for CO₂ hydrogenation to methanol

by Yerrayya, Lezcano, Velisoju, Trueba, Kulkarni, Almofleh, Aljama, Castaño
J. CO2 Util. Year: 2025 DOI: https://doi.org/10.1016/j.jcou.2025.103086

Abstract

This work investigates the mechanistic and kinetic effects of gallium (Ga) promotion on copper (Cu) catalysts for carbon dioxide hydrogenation using the density functional theory (DFT), in situ infrared spectroscopy, and mean-field microkinetic simulations. The DFT calculations reveal potential reaction pathways for methanol synthesis, emphasizing the role of formate (HCOO) and carboxyl (COOH) intermediates on Cu (111) and Ga–Cu (111) surfaces. The in situ infrared spectroscopic analysis identifies surface intermediates, validating DFT-predicted mechanistic trends and confirming the preferential COOH pathway on unpromoted Cu catalysts and the HCOO pathway on Ga–Cu catalysts. Microkinetic simulations demonstrate how Ga promotion alters reaction kinetics, favoring the HCOO pathway via H₂COO** formation and explaining the enhanced methoxy intermediate generation on Ga–Cu, which is critical for dimethyl ether production. The temperature effects demonstrate a kinetic shift toward the COOH pathway on Cu catalysts, contrasting with the stability of the HCOO pathway on Ga–Cu. This integrative study demonstrates the significance of Ga in modulating surface chemistry and reaction mechanisms, offering a foundation for designing efficient methanol synthesis catalysts.

Keywords

MKM HCE CO2