Molybdenum phosphide as a novel and stable catalyst for dry reforming of methane

Abstract

In this work, we proposed a novel catalyst, molybdenum phosphide (MoP), which exhibited high coking and oxidation resistance for dry reforming of CH₄ with CO₂ (DRM). The catalytic stability of MoP was found to be superior to that of Ni/Mo₂C (recently known to be an efficient non-noble metal catalyst for DRM). At higher temperatures (≥800 °C) and weight hourly space velocity (WHSV) values, the MoP catalyst would deactivate due to the oxidation of the catalyst to MoO₂ with the loss of P, while operation at a lower temperature (750 °C) and WHSV resulted in stabilization of the MoP for the duration of the experiments (100 h). This might be due to a decrease in the oxidant-to-catalyst exposure. It was proposed that there were two possible DRM mechanisms (redox-type and noble metal-type) over the MoP catalyst, which were similar to those over the Ni/Mo₂C catalyst. Nevertheless, the contribution of the noble metal-type mechanism to DRM activity on MoP was more than that on Ni/Mo₂C, which accounted for the fact that the former showed better stability than the latter. It was suggested that the noble metal-type mechanism should be preferable for DRM over carbide and phosphide catalysts.