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

Related People

Related Publications

Optimized coupling of photocatalysis and cavitation for phenol degradation: Use of an extended-kinetic approach

by Sarvothaman, Subburaj, Velisoju, Kulkarni, Canciani, Castaño, Nagarajan, Guida, Roberts
Environ. Adv. Year: 2024

Abstract

The coupling of hydrodynamic cavitation (HC) and photocatalysis (PC) predominantly exhibits a complementary nature, which is highlighted through a synergistic index. However, this calculation, based on pseudo-first order kinetics, fails to accurately represent the concentration data, often skewed by the formation of reaction intermediates. To address this, an ‘extended’ kinetic approach previously developed with two parameters, which accounts for the formation of intermediates, was adopted. The PC process was optimized for a simulated wastewater containing phenol of concentration (C0) of 100 ppm by applying a UV-A light source of intensity 175 ± 8 W/cm2 on an operating volume (VL) of 200 mL. Catalyst loading, solution pH and initial concentration (C0) were optimized. These optimal parameters were used to operate HC-PC (VL = 3500 mL) at a comparable illumination intensity across the 2 techniques’ reactors. It was observed that phenol conversion was observable only with halved C0 (= 50 ppm) for the HC-PC system, increasing catalyst loading from 0.5 to 1.0 g/L exhibited no increase in phenol conversion. The obtained results from experiments were interpreted with the help of the two-parameter model. For the PC system, the initial rate constant (k0) exhibits a similar trend to the final oxidation extent, however, it did not compare quantitatively. The second parameter – ‘y’ showed a high finite value, denoting the need for dosing external oxidants. The trends of the two-parameters with respect to different relevant parameters presented will help leverage this kinetic approach for AOPs, while optimizing and translating processes to larger scales of operation.

Keywords

MKM W2C