Simple and large-scale synthesis of β-phase molybdenum carbides as highly stable catalysts for dry reforming of methane

Abstract

In this work, we propose a facile, fast and large-scale synthesis of β-Mo₂C catalysts (about 100 grams). The current approach uses a simple solid mixture of (NH₄)₆Mo₇O₂₄·4H₂O and carbon nanotubes (CNTs) as a precursor and employs a fast heating rate method without holding time. Moreover, there was no need for passivating the carbide products. A series of β-Mo₂C/CNT catalysts (denoted as MoC-5, -15, -30 and -60) were successfully prepared from the precursors with the Mo content ranging from 5 to 60 wt% and their catalytic activities for dry reforming of methane (DRM) were evaluated. CH₄-TPSR and CO₂-TPO over the fresh samples proved that the abilities of CH₄ dissociation and oxidation resistance of β-Mo₂C were greatly enhanced by compositing with CNTs. It was also found that these abilities were dependent on the Mo content, the particle size and the interaction between β-Mo₂C and CNTs. Among these β-Mo₂C/CNT catalysts, MoC-30 showed the best catalytic stability for DRM, attributed to its high activity for CH₄ dissociation and high resistance to oxidation. Additionally, it is worth noting that the catalytic stability of monometallic MoC-30 was found to be superior to that of bimetallic Ni/β-Mo₂C (recently known to be an efficient non-noble metal catalyst for DRM).