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

Continuous Lumped Hydrocracking Kinetics of Plastic (Polyethylene) Pyrolysis Oil Blended with Gas Oil

by Lezcano, Trueba, Rodriguez, Palos, Gutierrez, Castaño
Ind. Eng. Chem. Res. Year: 2025 DOI: https://doi.org/10.1021/acs.iecr.5c01838

Abstract

The kinetics of coprocessing plastic waste into existing refinery infrastructure is challenging due to the complexity of the composition and its impact on catalyst deactivation. This work investigates the kinetics of cohydrocracking mixtures composed of vacuum gas oil and plastic pyrolysis oil (derived from waste polyethylene pyrolysis) over a NiW/HY catalyst in a laboratory-scale semibatch reactor. We used the continuous lumping approach (based on population balance) for the kinetic modeling, given its flexibility to model the entire product distribution and population dynamics, and incorporated a deactivation function. Deactivation was promoted by longer reaction times (i.e., beyond 0.5 h), heavier feed components (i.e., 350+ °C TBP fraction), and lower temperatures (e.g., 370 °C compared to 440 °C). Two types of expressions were considered for the deactivation function: coke-dependent and agnostic, time-based decay models. Both types of deactivations reproduced the experimental distillation curves, but the time-dependent model led to parameters that align better with expected hydrocracking behavior. Our findings highlight the feasibility of continuous lumped models as a tool for plastic valorization process design and optimization and the necessity of paying attention to the deactivation function to robustify these kinetic models.

Keywords

HPC W2C MKM