Direct Transformation of Syngas to Aromatics over Na-Zn-Fe5C2 and Hierarchical HZSM-5 Tandem Catalysts

Summary

Direct synthesis of aromatics from syngas is a great challenge because of severe operating conditions and low yield of aromatics. Making this process more competitive than the MTA (methanol to aromatics) process will require high energy efficiency and low CO₂ emission. A combination of Na-Zn-Fe₅C₂ and hierarchical HZSM-5 with uniform mesopores dramatically changed the product distribution of Fischer-Tropsch synthesis, leading to 51% aromatic selectivity under the stable stage with CO conversion >85%. C₁₂₊ heavy hydrocarbons almost disappeared, and the catalyst showed good stability. The hierarchical zeolitic structure and Brønsted acidity of HZSM-5 could be precisely tuned by controlling the alkali treatment conditions and the degree of ion exchange. The appropriate density and strength of the Brønsted acid sites and the hierarchical pore structure of HZSM-5 endowed the catalyst with an unprecedented aromatic yield. This work shows a broad area for development for syngas conversion.