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 image 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.