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

Assessment of Thermogravimetric Methods for Calculating Coke Combustion-Regeneration Kinetics of Deactivated Catalyst

by Ochoa, Ibarra, Bilbao, Arandes, Castaño
Chem. Eng. Sci. Year: 2017

Abstract

This work compares different methodologies for calculating the kinetic parameters of coke combustion, employed for catalyst regeneration, using thermogravimetric methods. A reference fluid catalytic cracking (FCC) spent catalyst was used as a representative example of the deactivated catalyst for the combustion runs, pre-used in the cracking of a vacuum gas oil at 773 K and 3 s. Three different types of approaches have been performed in order to obtain kinetic combustion parameters: (i) kinetic model-based, (ii) isoconversional and (iii) modulated methods. Additionally, a series of empirical modifications have been proposed to predict the kinetic behavior at different heating rates for the model-based approach. Using the best conditions and methods, the combustion activation energy of coke, deposited after the reaction mentioned, is in the order of ∼114, ∼156, and ∼162 kJ mol−1 for the kinetic model-based, isoconversional and modulated methods, respectively. The recommendations for measuring kinetic parameters are reported together with the benefits/disadvantages using the three mentioned approaches.

Keywords

O2H OLG CHA FCC REF MKM