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 Modeling of the Hydrotreating and Hydrocracking Stages for Upgrading Scrap Tires Pyrolysis Oil (STPO) towards High Quality Fuels

by Hita, Aguayo, Olazar, Azkoiti, Bilbao, Arandes, Castaño
Energy & Fuels Year: 2015

Abstract

The upgrading of scrap tires pyrolysis oil (STPO) has been studied in order to produce high-quality alternative fuels, conceived as the second and third stage of an industrially orientated valorization pathway for tires: pyrolysis, hydrotreating, and hydrocracking. The experiments have been carried out in a fixed-bed reactor under the following experimental conditions: (i) for hydrotreating: NiMo/Al2O3 catalyst; time on stream (TOS), 0–8 h; 300–375 °C; 65 bar; H2:oil ratio, 1000 (v/v); space time, 0–0.5 gcat h gfeed–1; and (ii) for hydrocracking: PtPd/SiO2–Al2O3 catalyst; TOS, 0–6 h; 440–500 °C; 65 bar; space time, 0–0.28 gcat h gfeed–1; H2:oil ratio, 1000 (v/v). From the results, lump-based kinetic models have been established for both stages, considering the reactions of (i) hydrodesulfurization (HDS), (ii) hydrocracking (HC), and (iii) hydrodearomatization (HDA) in each one of them. Catalyst deactivation is insignificant in the hydrotreating stage but important for the hydrocracking stage. Therefore, deactivation has been considered in the corresponding kinetic equations. The computed deactivation constants have allowed for quantifying the contribution of each lump/composition fraction to coke formation.

Keywords

HPC MKM W2C