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 Covers

Related Publications

The technological prospects of repurposing methane steam reformers into ammonia crackers for decarbonized H2 production

by Realpe, Lezcano, Kulkarni, Sayas, Morlanes, Rakib, Aldilaijan, Solami, Gascon, Castaño
Appl. Energy Year: 2024 DOI: https://doi.org/10.1016/j.apenergy.2024.124244

Abstract

The decarbonization of hydrogen production can be accelerated by repurposing existing methane steam reformers into ammonia crackers. Through kinetic modeling, reactor optimization, and process integration, we demonstrated the viability of repurposing industrial reformers into NH3 crackers using a Co-Ba-Ce extrudate catalyst. First, we combined an improved kinetic rate expression, validated through experiments, with a high-fidelity 2-D model to optimize the operation of a multi-tubular reactor with a fixed capacity of 7000 Nm3 h−1. Subsequently, we used heat integration techniques to integrate the reactor with supplementary and separation units. We proved the process energy efficiency to be 65.7% before heat integration and 75.3% for the integrated plant. The integrated, optimized plant results demonstrated the necessity of implementing an adiabatic pre-cracker, an element typically omitted in catalytic NH3decomposition techno-economic models. Our findings underscore the importance of real-world constraints and operational aspects in designing and optimizing NH3 conversion processes.

Keywords

MKM AMD