Kinetics study of C2+ oxygenates synthesis from syngas over Rh–MnOx/SiO2 catalysts

• The activity of C2+ oxygenates on Rh based catalysts is altered with the addition of MnOx.
• C2+ oxygenates from CO hydrogenation occurs at Rh–MnOx interface.
• The intrinsic kinetics of CO hydrogenation at 3.0 MPa is established using a power law model.
• The reaction mechanism for the formation of C2+ oxygenates were assumed.

C2+ oxygenates synthesis directly from syngas is one of the most promising processes for utilizing non-oil fossil fuels cleanly and efficiently. Bimetallic Rh–MnOx/SiO2 catalysts with different Rh/Mn ratios were prepared and characterized with HRTEM, TPD and TPR. It was evidenced that Rh nanoparticles were stabilized in a range 0.5–2.0 nm via the promotional effects of MnOx. Meanwhile the interface between Rh and MnOx was assumed to be favorable for the insertion of CO into Rh–CHx to form C2+ oxygenates; the intrinsic kinetics was performed over Rh (1.5 wt%)–Mn (0.4 wt%) catalysts at different temperatures. The kinetic parameters, including apparent activation energies and reaction orders, were calculated. With the combination of structural modification and kinetics, the reaction mechanism and the Mn promotional effects on Rh catalysts were elaborated.

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