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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A global methanol-to-hydrocarbons (MTH) model with H-ZSM-5 catalyst acidity descriptors

by Vicente, Aguayo, Castaño, Gayubo
Fuel Year: 2024 DOI: https://doi.org/10.1016/j.fuel.2024.132777

Abstract

This work presents a dual cycle-based kinetic model that uses H-ZSM-5 catalyst acidity descriptors for the methanol-to-hydrocarbons (MTH, -olefins, MTO, and –aromatics, MTA) processes. This model was developed using data obtained in 12 periodic reactions with three H-ZSM-5 zeolites of different acidity (Si/Al = 15, 40 and 140). We decoupled the kinetics of the model from the catalyst identity by linking the calculation of the kinetic parameters to the zeolite acidity, allowing us to perform simulations of the reactor operating under various conditions and with different zeolite acidity values different from those used experimentally. The results obtained in the simulations let us identify the best operating conditions for the MTO and MTA processes, and pointed at the main difficulties found when implementing these two technologies industrially. In addition, the conditions and values obtained for the target products, either light olefins or aromatics, were comparable with those presented by several existing works in the literature for H-ZSM-5 zeolites of similar acidity. Moreover, the methodology detailed here using acidity descriptors can be extrapolated for its application to other catalytic processes.

Keywords

MKM O2H