Depleting fossil fuel resources and the souring of energy requirements in the past few decades have supered the synthesis of value-added organic building blocks from conventional routes towards the potential biomass or coal-based syngas (CO+H2) process. Among these, the efficient conversion of syngas to aromatics (STA) has got much attention in recent years for its wider utilization as an important category of organic raw material in the energy and defense sectors. A series of different combinations of transition metal oxides (Zn, Cu, Ca, Co and Mg) along with Na and Mn on a conventional Fe-based catalyst were evaluated for the STA process. The effective inclusion of these metal oxides turned to a promising approach for facilitating the reaction rate and increasing the dissociative adsorption of CO to integrate with HZSM-5 in the STA process. In here, the desired decoration of Na and Mn could favorably suppress the excessive surface hydrogenation phenomenon. While, the alloying of different active FT synthesis metal components lead to the effective synergism for providing the expedient geometric and electronic configuration in homogenously distributed nanocrystals, where these active metal components could segregate to the bimetallic system by completely dispersing in Fe lattice and retaining as mixed oxide phase. This particular substitution of iron played a vital role in tailoring the reduction behavior of iron oxides and tuning the density of oxygen vacancies. It could adjust the adsorption characteristics of the catalytic surface that mainly dictate the concentration of active Fe5C2 species by facilitating the carburization process. The relative effects of pressure, temperature, space velocity and H2/CO molar ratio were also investigated on the catalytic performance of Fe-based catalyst. The optimal reaction conditions were evaluated as T = 355 oC, P = 4MPa, WHSV=1500h-1, H2/CO=1.5-2. The fabricated catalytic system was capable of meliorating the fraction of lower olefinic intermediates which were subsequently adsorbed on zeolite surface and transformed into ∼53% of aromatics selectivity in hydrocarbons by inhibiting the waste streams of CO2 (21%) in a stable single pass CO conversion of ∼99%. This work reveals an effective combination of different transition metal oxides with Fe which can potentially accelerate the desired catalytic activity for the one-step conversion of syngas to aromatics.

Meliorating the synergistic integration of Fe-based bimetallic oxides in a composite catalyst for directly converting syngas to aromatics

ACS Spring Meeting 2021

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