Numerical Modeling of n-Hexane Pyrolysis with an Optimized Kinetic Mechanism in a Hydrogen Plasma Reactor

TL;DR

This study develops and validates an optimized kinetic model for n-hexane pyrolysis in a hydrogen plasma reactor, using CFD simulations to analyze reaction dynamics and product selectivity, revealing higher C2 monomer yields compared to traditional methods.

Contribution

The paper introduces an automated reaction mechanism generation for plasma pyrolysis and integrates it with CFD modeling to analyze transport phenomena and product distribution.

Findings

Higher C2 monomer selectivity (~50%) in plasma pyrolysis compared to conventional methods (~30%)

Fluid mixing dynamics significantly influence conversion and product selectivity

The CFD model captures essential transport phenomena missed by lower-dimensional models

Abstract

The physicochemical mechanisms underlying the pyrolysis of n-hexane in a high temperature Ar-H2 environment were investigated for plasma pyrolysis process. An optimal chemical kinetics model was developed using the Reaction Mechanism Generator (RMG), an automated tool for constructing reaction mechanisms. This model was validated through 0-D analyses, where simulation result were compared with existing kinetic models (LLNL,JetSurf) and experimental data from conventional n-hexane pyrolysis. Subsequently, 1-D analysis were conducted to identify the optimal operational flow rate in plasma pyrolysis reactor, the results of which informed detailed three-dimensional (2-D) computational fluid dynamics (CFD) modeling of the plasma reactor. The CFD simulations reveal that fluid mixing dynamics play a dominant role in determining the extent of conversion and product selectivity, highlighting the limitations of lower-dimensional models in capturing essential transport phenomena. Notably, the simulations indicate a higher C2 monomer selectivity of approximately 50 % under plasma-based n-hexane pyrolysis, in contrast to the roughly 30 % selectivity achieved via conventional fossil-fuel-based methods. These findings underscore the potential advantages of plasma-driven pyrolysis and represent a critical step toward a comprehensive understanding of the complex thermochemical behavior governing plasma-assisted processes.