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

Kinetic Model Discrimination for Toluene Hydrogenation over Noble-Metal-Supported Catalysts

by Castaño, Arandes, Pawelec, Fierro, Gutierrez, Bilbao
Ind. Eng. Chem. Res. Year: 2007

Abstract

The hydrogenation of toluene has been studied using an integral fixed-bed reactor with a Pt/γ-Al2O3 commercial catalyst over a wide range of experimental conditions:  temperature = 100−250 °C, H2 inlet pressure = 0.3−1.9 bar, toluene inlet pressure = 0.04−0.15 bar, and space time = (2−10) × 10-2 gcat h gtol-1. Hydrocarbon molecules block the active sites at elevated temperature and toluene partial pressure, and, as a consequence, three reaction-controlled regimes occur:  (i) kinetic, (ii) surface coverage, and (iii) thermodynamic. The experimental data have been fitted to 23 kinetic models proposed in the literature (empirical and mechanistical), and their parameters have been estimated. The model discrimination has been performed based on statistical F-test and mechanistical aspects. A simplified kinetics model is proposed by introducing the thermodynamical equilibrium constant. Finally, that kinetic model is used for reactor simulation.

Keywords

HPC MKM