Nanostructured molybdenum carbide on biochar for CO₂ reforming of CH₄

A simple procedure was developed to synthesize molybdenum carbide nanoparticles (Mo₂C/BC) by carburization of molybdate salts supported on the biochar from pyrolysis of biomass without using extra carbon source or reducing gas. The molybdenum carbide formation procedure investigated by in-situ XRD and TGA-MS indicated that the phase transitions followed the path of (NH₄)₆Mo₇O₂₄·4H₂O → (NH₄)₂Mo₃O₁₀ → (NH₄)₂Mo₁₄O₄₂ → Mo₈O₂₃ → Mo₄O₁₁ → MoO₂ → Mo₂C. The volatile gases CO, H₂, and CH₄ evolved from biochar and the biochar solid carbon participated in the reduction of molybdenum species, while the biochar and CH₄ served as carbon sources for the carburization. Temperature programmed surface reactions of Mo₂C/BC indicated that CH₄ dissociated as CH₄ ⇋ C∗ + 2H₂ on the catalyst surface, and CO₂ reacted as CO₂ + C∗ ⇋ 2CO+ ∗ due to oxidation of Mo₂C. Both experiment data and thermodynamic analysis for the study of operation conditions of CO₂ reforming of CH₄ clearly demonstrated that the yields of H₂ and CO increased with the increased temperature and the reasonable conversions should be performed at 850 °C, at which both CH₄ and CO₂ conversions were higher than 80%.