Synthesis of mixed alcohols from synthesis gas over alkali and Fischer–Tropsch metals modified MoS₂/Al₂O₃-montmorillonite catalysts

Abstract

A series of modified MoS₂-supported catalysts was investigated for the synthesis of mixed alcohols from synthesis gas in a high-pressure gas–solid flow reaction system. Al₂O₃-pillared montmorillonite (denoted as Al₂O₃-Mont) was prepared by calcining [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]-pillared montmorillonite at 673 K in air. Al₂O₃-Mont was an excellent support for MoS₂ in the synthesis of mixed alcohols from synthesis gas. The MoS₂/Al₂O₃-Mont catalyst showed a CO conversion of 34.6 % and a selectivity for alcohols of 33.5 % at 553 K under 8 MPa. By introducing 3 wt% K (one of the alkali metals) in MoS₂/Al₂O₃-Mont, the CO conversion increased to 40.5 % and the selectivity for alcohols increased to 41.9 % at 553 K under 8 MPa. Furthermore, by increasing 5 wt% Ni (one of Fischer–Tropsch metals) in KMoS₂/Al₂O₃-Mont, the CO conversion increased to 51.8 % and the selectivity for alcohols increased to 50.5 % at 553 K under 8 MPa. With increasing reaction temperature, the CO conversion and the ratio of C₂₊ higher alcohols to methanol increased but the selectivity for total alcohols greatly decreased due to the formation of hydrocarbons over KNiMoS₂/Al₁₃-Mont under 8 MPa. With increasing reaction pressure, the CO conversion and the ratio of C₂₊ higher alcohols to methanol increased while the selectivity for total alcohols was almost constant over KNiMoS₂/Al₁₃-Mont at 553 K. KNiMoS₂/Al₁₃-Mont showed a good catalytic stability in a feed gas containing 10 ppm H₂S but gradually deactivated in a clean feed gas due to losing sulfur component during the reaction.