Elucidating the synergistic fabrication of dual embedded (χ-Fe5C2 + θ-Fe3C) carbide nanocomposites in Na-FeCa@AC/HZSM-5 integrated catalyst for syngas conversion to aromatics

Abstract

Herein, an activated carbon (AC) modified Fe-oxide catalyst has been employed in Na-FeCa@AC/HZSM-5 integrated catalytic system for the direct conversion of syngas to aromatics (STA). In comparison to the conventionally impregnated Fe/C catalysts, the spatial confinement of highly dispersed Fe 3 O 4 nanocrystals in a rigid geometry of defective graphite sheet by the efficient modulation of different (AC, Ca) promoters, calcination environment and the surface carbon reactions in sol-precipitation method, potentially deflected the sintering and agglomeration behavior of Fe nanoparticles . The meliorated higher extent of CO chemisorption on the tuned Fe surface and the different reduction/carburization schemes cultivated the high-purity (54% χ-Fe 5 C 2 + 44% θ-Fe 3 C) carbide nanoparticles . The encapsulation of perforated carbon patches during carburization favored the stabilization of highly active carbide phase under reaction conditions, where the subsequent precipitation of carbon elements led to the further recruitment of multi-layer carbide films for the accelerated CO dissociation and the partial decomposition of olefinic intermediates. Since, the dually embedded terrace carbide islands were rather enriched from one phase to another (27.3%θ-Fe 3 C ⇌ 70.7%χ-Fe 5 C 2 ) during the reaction, giving a simultaneously enhanced catalytic activity of 97% CO conversion and 60% aromatics selectivity while suppressing the net CO 2 release (21%). The current study anticipates a promising scheme to formulize a highly active and stable iron-based catalyst to be integrated with HZSM-5 for STA process.