Reactivity and in situ X-ray absorption spectroscopy of Rb-promoted Mo2C/MgO catalysts for higher alcohol synthesis

The influences of MgO support and Rb2CO3 promoter on the activity and selectivity of Mo2C-based catalysts for higher alcohol synthesis from syngas were explored. The reaction was performed in a fixed-bed reactor system operating at 573 K, 30 bar, gas flow rate of 24,000 cm3 gMo-1 h−1, and H2:CO ratio of 1:1. When promoted by Rb2CO3, the selectivity of alcohols over 5 wt.% Mo2C/MgO can reach 61 C% on a CO2-free basis, with C1–C4 hydrocarbons being the main side products. Production of higher alcohols was enhanced at high promoter loading and low conversion. Characterization by X-ray absorption spectroscopy (XAS) indicated that passivated Mo2C/MgO was more oxidized than bulk Mo2C, but exposure to reaction conditions for 4 h partially reduced the passivated sample. Electron microscopy and XAS confirmed that Mo2C was highly dispersed on MgO. The Rb K edge structure suggested that the Rb2CO3 promoter was structurally modified in the reaction.

Nanoparticles of Mo2C were supported on MgO, extensively characterized by a variety of methods, and evaluated as catalysts for syngas conversion to alcohols. Addition of Rb2CO3 promoted the alcohol synthesis reaction at the expense of hydrocarbon formation. Since bulk Mo2C was primarily a Fischer–Tropsch catalyst, the basic support and the promoter are critical components for alcohol synthesis.Figure optionsDownload high-quality image (115 K)Download as PowerPoint slideHighlights
► Nanoparticles of Mo carbide were synthesized on the surface of magnesia.
► CO hydrogenation was catalyzed effectively by supported Mo carbide.
► Addition of Rb to Mo2C/MgO promoted the alcohol formation from syngas.
► X-ray absorption spectroscopy showed the reduction of passivated Mo carbide by syngas.
► Rb2CO3 promoter was structurally modified in the syngas reaction.