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

Related People

Related Covers

Related Publications

Evaluating catalytic (gas–solid) spectroscopic cells as intrinsic kinetic reactors: Methanol-to-hydrocarbon reaction as a case study

by Valecillos, Elordi, Cui, Aguayo, Castaño
Chem. Eng. J. Year: 2022 DOI: https://doi.org/10.1016/j.cej.2022.137865

Abstract

Commercial spectroscopic gas–solid cell reactors are routinely used to analyze the dynamics of the catalyst (catalyst pelletized as a disc) structure and retained/adsorbed species using multiple operandotechniques. These instruments have revolutionized the understanding of many catalytic reactions, including the methanol-to-hydrocarbon reactions. We propose a reaction engineering framework to evaluate spectroscopic cells based on (a) analyzing the fluid dynamic performance, (b) comparing their performance with a reference packed-bed reactor, and (c) the assessment of the external and internal mass transfer limitations. We have used a Specac HTHP and a Linkam THMS600 cell reactors coupled with the corresponding gas conditioning, spectroscopic, and mass spectrometry apparatuses. Our results reveal that these cells approach a perfect mixing only with several equivalent tanks in series and they are reliable at low catalyst loadings (thin disc) and high flowrates (low spacetimes). Under these conditions, we can avoid external-internal mass transfer limitations and fluid dynamic artifacts (e.g., bypassing or dead/stagnant volume zones), obtaining intrinsic kinetics with the corresponding operando spectroscopic signatures. The proposed methodology allows to understand the influence of process parameters and potential design modifications on the observed kinetic performance.

Keywords

O2H MKM CRE