Reactivity and in situ X-ray absorption spectroscopy of Rb-promoted Mo 2C/MgO catalysts for higher alcohol synthesis

Abstract

The influences of MgO support and Rb 2CO 3 promoter on the activity and selectivity of Mo 2C-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 cm 3 g Mo - 1 h −1, and H 2:CO ratio of 1:1. When promoted by Rb 2CO 3, the selectivity of alcohols over 5 wt.% Mo 2C/MgO can reach 61 C% on a CO 2-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 Mo 2C/MgO was more oxidized than bulk Mo 2C, but exposure to reaction conditions for 4 h partially reduced the passivated sample. Electron microscopy and XAS confirmed that Mo 2C was highly dispersed on MgO. The Rb K edge structure suggested that the Rb 2CO 3 promoter was structurally modified in the reaction.