Mechanism and kinetic characteristics of photo-thermal dry reforming of methane on Pt/mesoporous-TiO₂ catalyst

Dry reforming of methane (DRM) reaction under photo-thermal catalysis route have attracted more and more attentions due to its fast reaction rate and higher conversion compared with traditional thermal catalysis techniques. However, most of current researches were mainly focused on the development of new photo-thermal catalysts, while the kinetic characteristics of DRM reaction under photo-thermal conditions was seldomly studied and discussed. Aiming this point, the performances of a Pt/mesoporous-TiO₂ catalyst were investigated under different reaction conditions (reaction temperature, light irradiation intensity and molar ratio of feed gases) in this paper. It was found that (1) Increasing the light intensity and reaction temperature possessed a positive effect on the DRM reaction, increasing the formation rates of two products and H₂/CO ratio; (2) The intensification ratio of formation rates of light/dark condition would decrease with higher reaction temperature; (3) Under dark conditions, increasing the partial pressure of CO₂ was not conducive to the progress of the DRM reaction; (4) With light irradiation, an appropriate increase in the partial pressure of CO₂ would be beneficial to the progress of the DRM reaction and improve the formation rates of the products. To explain the variations of light-enhanced intensification ratios and values at different temperatures, a possible simple model of light-enhanced reaction mechanism was proposed, and the contribution of light to the DRM reaction was deeply discussed. Meanwhile, combined with in situ DRIFTS characterization, the effects of operating conditions on specific micro-steps of the reaction were determined carefully. The obtained conclusions are of great practical significance for the design, development and process parameter optimization of photo-thermal DRM reaction process.