RESUMEN
A mechanism for carbon deposition and its impact on the reaction kinetics of Methane Dry Reforming (MDR) using Rhodium-based catalysts is presented. By integrating Raman spectroscopy with kinetic analysis in an operando-annular chemical reactor under strict chemical conditions, we discovered that carbon deposition on a Rh/α-Al2O3 catalyst follows a nucleation-growth mechanism. The dynamics of carbon aggregates at the surface is found to be ruled by the CO2/CH4 ratio and the inlet CH4 concentration. The findings elucidate the spatiotemporal development of carbon aggregates on the catalyst surface and their effects on catalytic performance. Furthermore, the proposed mechanism for carbon formation shows that the influence of CO2 on MDR kinetics is an indirect result of carbon accumulation over time frames exceeding the turnover frequency, thus reconciling conflicting reports in the literature regarding CO2's kinetic role in MDR.
RESUMEN
We propose the use of surface plasmon resonance (SPR) as a distinctive marker for real-time monitoring in reaction conditions of gold nanoparticles supported on α-Al2O3. The study leverages the SPR shape-and-size dependency to monitor metal nanoparticles in reaction conditions, evidencing an influence of both dimensions and agglomerations on the SPR peak position. Operando measurements, coupling UV-vis spectroscopy and catalytic testing, allows to follow the dynamics during nanoparticle formation (Au3+ to Au0 reduction) and during the reverse water gas shift reaction (CO2 + H2 â CO + H2O). The catalyst structure and stability in reaction conditions was further confirmed by operando X-ray spectroscopy and PXRD data. Overall, this approach enables the direct acquisition of information on the structure-activity relationship of metal-based supported catalysts under actual reaction conditions.