In-situ DRIFTS and kinetic-thermodynamic evaluation of dry reforming of methane over La-modified alumina-supported Ni-Ce-Fe catalyst

Abstract

Dry reforming of methane (DRM) is a dual-purpose approach for reducing greenhouse gas emissions simultaneously producing syngas. Unraveling DRM mechanisms necessitates a combined interrogation of thermodynamic driving forces, transient surface species transformations, and rate-determining steps. Here, the study presents an integrated approach that combines thermodynamic assessment, kinetic modeling, and in-situ DRIFTS analysis to investigate the DRM reaction over the catalyst (Ni-Ce-Fe/La₂O₃-Al₂O₃) synthesized through the citrate sol–gel method. Catalyst characterization revealed that the La incorporation promotes the formation of NiAl₂O₄ spinel and strengthens metal-support interactions. Catalytic performance was evaluated in a fixed-bed reactor, exhibiting the highest conversions of CO₂ and CH₄ at approximately 92 % and 86 %, respectively. Thermodynamic analysis indicated that above 625 °C, the reverse water–gas shift (RWGS) reaction becomes thermodynamically favorable alongside DRM, contributing to CO₂ consumption and H₂ depletion, which resulted in a lower H₂/CO ratio and high CO₂ conversion. In-situ DRIFTS studies revealed the formation of surface intermediates such as bicarbonate, monodentate, and bidentate carbonates during CO₂ adsorption. Kinetic modeling based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW) model identified methane associative adsorption as the rate-limiting step, with activation energy for CH₄ activation estimated at ∼70 kJ/mol and enthalpy for CO₂ adsorption around ∼65 kJ/mol.