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

Unraveling the promoter role of Ba in Co–Ce catalysts for ammonia decomposition using microkinetic modeling

by Lezcano, Realpe, Kulkarni, Sayas, Cerrillo, Morlanes, Mohamed, Velisoju, Aldilajan, Katikaneni, Rakib, Solami, Gascon, Castaño
Chem. Eng. J. Year: 2023 DOI: https://doi.org/10.1016/j.cej.2023.144623

Abstract

Ammonia decomposition is an attractive process for decarbonized hydrogen production. Alkalis are known to promote the reaction, which is especially important to enable non-noble metal catalysts to achieve similar performances to the benchmark Ru catalyst. Herein, we evaluate the kinetic contribution of Ba as a promoter in Co–Ce catalysts, using a microkinetic approach to investigate the influence of the promoter on the elementary steps of ammonia decomposition. For this purpose, we performed experiments over a wide range of conditions with two Co–Ce catalysts, with and without Ba. The results were used to fit microkinetic models with enthalpy–entropy constraints for parameters such as prefactors, activation energies, and sticking coefficients. Based on the differences in these parameters, we compared surface coverages and partial equilibrium indices to show how Ba enhances the rate of N2 desorption, one of the two kinetically relevant steps, along with the NH2 dehydrogenation.

Keywords

AMD MKM