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

Kinetic Modelling for Assessing Product Distribution in Toluene Hydrocracking on a Pt/HZSM-5 Catalyst

by Castaño, Arandes, Pawelec, Olazar, Bilbao
Ind. Eng. Chem. Res. Year: 2008

Abstract

A kinetic model has been proposed to quantify the distribution of product lumps in the hydrocracking of toluene on a bifunctional catalyst prepared by physically mixing Pt/γ-Al2O3 with high-acidity HZSM-5 zeolite (Si/Al = 15). The current model is based on one that was previously proposed for the hydrogenolytic cracking of methylcyclohexane, given that this is the limiting step because of the rapid hydrogenation of toluene. The experimental results used for calculating the kinetic parameters were obtained in an isothermal fixed-bed reactor under a wide range of operating conditions (250−450 °C; WHSV = 2.85−100 h-1, τ = 1.0−3.5 gzeolite h gtoluene-1); pressure = 20−60 bar; molH2/moltoluene = 19−59; conversion = 0−100% (integral reactor). The model faithfully predicts the effects of operating conditions on the product distribution and is suitable for use in the optimization of C2+n-alkane production.

Keywords

HPC MKM