Investigation of sulfur-resistant, highly active unsupported MoS2 catalysts for synthetic natural gas production from CO methanation

This paper reports on an enhanced activity of sulfur-resistant methanation catalyst by introducing sulfur powder instead of toxic H2S in catalyst preparation. Ammonium heptamolybdate (AHM) was a suitable precursor for this catalyst preparation based on consideration of economy and activity. The effect of S/AHM weight ratio and sulfidation atmosphere on catalyst methanation performance was studied and the optimum S/AHM ratio was 3. Sulfidation atmosphere affected not only methanation activity but also the structure and morphology of the catalysts. The catalyst treated in inert atmosphere exhibited relatively the highest methanation activity with CO conversion as high as 88.2%, which was approaching the thermodynamic equilibrium value. The catalysts characterization results indicated that the as-prepared catalyst at S/AHM ratio as 3 had relatively higher specific surface area and larger pore volume than those with other S/AHM ratio. The MoS2 particles were poorly crystallized with long and straight multi-layered slabs. For the catalyst treated in nitrogen environment, more weakly-bonded sulfur species existed on the surface and more sulfur vacancies resided on the edge planes of MoS2 particles, which are considered to be the active sites for methanation.

► An alternative to prepare highly active unsupported MoS2 catalysts for CO methanation by introducing sulfur powder instead of H2S in catalyst preparation was proposed. The optimum S/AHM weight ratio of as-prepared catalyst for methanation activity was 3.
► Compared with H2S/H2 environment, sulfidation in nitrogen atmosphere yielded catalyst with more surface weakly-bonded sulfur species, which is favorable for active site formation.