Role and importance of proper kinetic parameter estimation during the kinetic modeling of CO_x Methanation

Accurate reactor scale prediction of CO_x methanation performance depends critically on kinetic models that remain physically valid beyond the narrow conditions in which they were originally fitted. However kinetic parameters are often estimated through purely numerical fitting, without verifying their thermodynamic consistency or mechanistic plausibility, a practice that can yield deceptively good fits while hiding non-physical behavior upon extrapolation.

This work examines the issue by confronting two competing LHHW kinetic frameworks, a three-reaction scheme with an independent CO₂ methanation reaction, and a two-reaction scheme, against experimental temperature and composition profiles from two non-isothermal, oil-cooled packed-bed reactors: operating at 4-6 bar and GHSV between 6,000-25,000 h^-1. Kinetic parameters were estimated via nonlinear regression employing the Levenberg-Marquardt optimization method on 1D pseudo-homogeneous PFR models and several specific statistical analysis to corroborate that the values obtained are optimal.

Results revealed that parameter estimation quality governs predictive robustness. One framework produced thermodynamically consistent equilibrium terms and physically reasonable activation energies, for instance, achieving r² values as high as >0.98, and remarkable results in other statistical analysis applied.

These findings demonstrate that kinetic parameter estimation and the proper establishment of a kinetic model are determinant steps when performing kinetic modeling and of whether a model can be reliably transferred across different systems in CO_x methanation.