Synthesis of Methanethiol from Carbonyl Sulfide and Carbon Disulfide on (Co)K-Promoted Sulfide Mo/SiO 2 Catalysts

The catalytic properties of a series of (Co)K-promoted Mo sulfide catalysts supported on SiO2 were explored in the synthesis of methanethiol from carbonyl sulfide (COS) and CS2. MoS2 was very active for the conversion of COS, but allowed only low yields of CH3SH because of the parallel decomposition of COS to CO and H2S and the reduction of CH3SH to CH4. CS2, on the other hand, was completely converted to CH3SH with high yield below 570 K on MoS2. The formation of CH4, however, dramatically decreased the yield of CH3SH above 570 K. The addition of K+ cations decreased the conversion of both reactants, but also reduced the rate of decomposition/reduction reactions. The doubly promoted CoK-Mo catalyst led to the highest conversions with moderate to high yields of methanethiol. We conclude that the addition of K+ cations generates very weak adsorption sites, suppressing so the C-S bond cleavage. These sites catalyze, however, COS disproportionation. Accessible Co and Mo sites are part of the active sites for all reactions observed. All catalytic active sites are concluded to be on the edge of MoS2 slabs.