Carbon monoxide hydrogenation on potassium promoted Mo2N catalysts

Abstract The catalytic performance of Mo 2 N and K-Mo 2 N were assessed in hydrogenation of carbon monoxide in the reaction temperature range of 275–325 °C, 7 MPa and 60,000 h −1 . The nitrides were synthesized via temperature-programmed treatment of ammonium heptamolybdate (AHM) and K-AHM precursors under continuous NH 3 flow. The influence of potassium loading (0.45–6.2 wt.%) on the Mo nitride phase and its resultant effect on the catalytic properties were been investigated. The nitride catalysts were characterized in terms of BET/pore size, powder X-ray diffraction, DRIFTs, CO-TPD-mass, HR-TEM and XPS measurements. The formation of cubic γ-Mo 2 N and monoclinic K 2 MoO 4 phases were confirmed by XRD and TEM. Platelet morphology with particle size in the range of 5–10 nm was observed for γ-Mo 2 N. CO-TPD-mass results mainly revealed molecular CO sorption on Mo 2 N and K-Mo 2 N surface. The highest total oxygenate selectivity (44%, 300 °C) was observed on 1.3K-Mo 2 N with a K/Mo δ+ surface ratio of 0.06. This is associated with well distributed K in the matrix of γ-Mo 2 N. Distribution of K was reduced due to K 2 MoO 4 formation at 3 and 6.2 wt.% K loading. DRIFTs results clearly demonstrates greater hydrocarbon formation on unpromoted Mo 2 N due to (i) CO dissociative hydrogenation (ii) water-gas shift reaction. Further, addition of K to Mo 2 N significantly improved the oxygenate selectivity by promoting the molecular CO insertion into −CHx intermediate.