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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Related Covers

Related Publications

Elucidating the rate-determining step of ammonia decomposition on Ru-based catalysts using ab initio-grounded microkinetic modeling

by Kulkarni, Realpe, Yerrayya, Velisoju, Sayas, Morlanes, Cerrillo, Katikaneni, Paglieri, Solami, Gascon, Castaño
Catal. Sci. Technol. Year: 2023 DOI: https://doi.org/10.1039/D3CY00055A

Abstract

Decarbonizing the current energy system requires a shift toward renewable energy sources, among which ammonia is a remarkable hydrogen carrier. However, developing an efficient process for the catalytic decomposition of ammonia is still required. Here, we propose a combined modeling–experimental approach to elucidate the rate-determining step in ammonia decomposition on Ru-based catalysts. We characterize and test two supported Ru and Ru–K catalysts in the reaction. We develop several microkinetic models based on ab initio calculations considering different rate-determining steps and validate them with the results of packed bed experiments. For the method validation, we develop a fitting strategy based on modifying the lowest number of parameters from those initially obtained theoretically. A good agreement between the simulated and measured experimental ammonia conversions is obtained, thus widening our understanding of this critical hydrogen production process. The approach presented here allows distinguishing the rate-determining step accurately, and it could be applied to other catalytic systems used in ammonia decomposition to avoid over-relying on empirical models.

Keywords

AMD MKM