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

Kinetics and Reactor Modeling of the Conversion of n-Pentane using HZSM-5 catalysts with Different Si/Al ratio

by Cordero-Lanzac, Aguayo, Castaño, Bilbao
React. Chem. Eng. Year: 2019

Abstract

The production of olefins and aromatics from n-pentane has been modeled using the experimental results collected in an isothermal packed bed reactor with HZSM-5 zeolite catalysts with different Si/Al ratios (15 and 140) in the temperature range of 400–550 °C. In the first stage, a lump-based kinetic model has been established, evaluating the role of the Si/Al ratio in the kinetic parameters and therefore, in the conversion, product distribution and deactivation by coke. The effect of the catalyst acidity and the reaction conditions has been explained by analyzing the used catalysts by means of N2 and tert-butylamine adsorption–desorption, temperature-programmed oxidation and confocal fluorescence microscopy. In the second stage, the kinetic parameters extracted for both catalysts have been used in simulations of an isothermal packed bed reactor in order to study the evolution of the reaction with the space time and time on stream. Certain suitable conditions (550 °C and 3.5 gcat h molC−1) for maximizing the yield and selectivity to olefins (31 and 51%, respectively, using the zeolite with Si/Al = 140) and aromatics (yield and selectivity of 53%, using the one with Si/Al = 15) in the simulated range were found.

Keywords

CHA MKM