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

Insight into the Deactivation and Regeneration of HZSM-5 Zeolite Catalysts in the Conversion of Dimethyl Ether to Olefins

by Cordero-Lanzac, Ateka, Perez-Uriarte, Castaño, Aguayo, Bilbao
Ind. Eng. Chem. Res. Year: 2018

Abstract

The impact of different process variables affecting the coking and rejuvenation of HZSM-5 zeolite catalyst has been studied during the conversion of dimethyl ether (DME) to olefins in a fixed bed reactor. Those variables involve the effect of (i) the matrix material with mesopores; (ii) temperature; (iii) space time; (iv) acidity of the catalyst; (v) steam, inert or air in the reaction-regeneration medium. Used catalysts have been characterized through N2 adsorption-desorption and temperature-programmed oxidation, and the presence of three coke fractions has been identified, deposited within the zeolite micropores, the external surface of the crystals and the mesopores of the matrix. Low Si/Al ratios (140) and temperatures (350 °C), and cofeeding water with DME, reduce the formation of coke within the zeolite micropores, favoring the stability of the catalyst. Reaction-regeneration cycles confirm that catalysts totally recover the activity through combustion of coke during a heating ramp up to 550 °C.

Keywords

O2H MKM