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

Simultaneous Modeling of the Kinetics for n-Pentane Cracking and the Deactivation of a HZSM-5 Based Catalyst

by Cordero-Lanzac, Aguayo, Gayubo, Castaño, Bilbao
Chem. Eng. J. Year: 2018

Abstract

A kinetic model for the catalytic cracking of n-pentane over a HZSM-5 zeolite (Si/Al = 15) based catalyst has been proposed. In this model, the kinetic scheme of reactions is based on the paraffin cracking mechanisms and uses lumps (light olefins, light paraffins, C5+ paraffins, aromatics and methane). The reaction steps of the scheme are related with the catalytic cracking routes: protolytic cracking, β-scission, oligomerization-cracking, hydride transfer, olefin condensation and methane formation. In addition, a kinetic deactivation equation has been used for modeling the catalyst deactivation, depending on the coke precursors (light olefins and aromatics) concentration. The catalyst has been prepared by agglomerating the HZSM-5 zeolite with a mesoporous matrix of weak acidity, using pseudoboehmite as a binder. The kinetic runs have been carried out in a fixed bed reactor using the following conditions: 350–550 °C, 1.4 bar, space time up to 1.1 gcat h−1 molC−1 and time on stream up to 15 h. The formation of olefins and aromatics, as well as the catalyst deactivation, are favored at high temperatures. A mathematical methodology based on the Levenberg-Marquardt algorithm has been used for the kinetic parameters estimation. The method has allowed for the simultaneous computing of the kinetic parameters of each step of the reaction scheme and the deactivation kinetics, from the experimental results of evolution with the time on stream of each lump concentration.

Keywords

O2H CHA MKM