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 Publications

Dual-cycle-based lumped kinetic model for methanol-to-aromatics (MTA) reaction over H-ZSM-5 zeolites of different Si/Al ratio

by Vicente, Aguayo, Castaño, Gayubo
Fuel Year: 2024 DOI: https://doi.org/10.1016/j.fuel.2023.130704

Abstract

In this work we developed a 7-lump kinetic model for the methanol-to-aromatics (MTA) reaction based on the dual-cycle mechanism, with consideration of deactivation of the catalyst by coke formation and applicable to H-ZSM-5 zeolite-based catalysts of different acidity. The model developed is suitable to be implemented at an industrial scale, as the intrinsic kinetic aspect fits the experimental data in a wide range of operating conditions. Moreover, the model is validated for two catalysts (prepared from two H-ZSM-5 zeolites of Si/Al ratio = 15 and 40), and considers a combined formation of coke from both unreacted oxygenates and reaction products (specifically, aromatics and light olefins). The final model comprises 10 reaction steps, and considers the effect of water co-feeding. The kinetic parameters of best fitting are obtained in the simultaneous fitting of the zero time and the deactivation kinetics. We compared the kinetic parameters of the best-fitting model for the two catalysts and related the differences obtained between both sets of parameters to catalyst properties.

Keywords

MKM O2H