Enhanced carbon resistance and regenerability in methane partial oxidation to syngas using oxygen vacancy-rich fibrous Pd, Ru and Rh/KCC-1 catalysts

Abstract

Rising concerns about petroleum depletion and energy demand are calling for alternative processes such as methane partial oxidation to produce syngas for downstream synthetic fuel production. However, industrial application is limited by catalyst deactivation caused by carbon deposition and reoxidation of active metals. Here we synthesized dendritic fibrous Pd, Ru and Rh/KAUST Catalysis Centre 1 (KCC-1) catalysts by microemulsion followed by wetness impregnation. Catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, electronic spin resonance, Fourier transform infrared spectroscopy and UV–Vis diffuse reflectance spectroscopy. We measured catalytic performance, stability and regenerability at 900 °C over 16 h-on-stream. Results reveal that oxygen vacancies into the KCC-1 framework enhance the interaction with noble metal particles, creating a strong metal–support interaction decreasing in the order Rh/KCC-1, Pd/KCC-1, Ru/KCC-1. Interestingly, CH4 conversion followed the same order: 74-80% for Rh/KCC-1, 60-71% for Pd/KCC-1, 53-63% for Ru/KCC-1, without a significant carbon deposit. These findings mean that oxygen vacancies retained the metal in the active metallic phase and prevented carbon deposits. Overall, metal/KCC-1 is as bifunctional catalyst whereby oxygen vacancies generate labile electrons contributing to electrostatic metal–support interactions, stabilization of metal phases and providing labile oxygen ions for carbon gasification.