Epsilon iron carbide derived from Fe4N for ethanol synthesis via ester hydrogenation

A supported ε-Fe 2 C catalyst derived from the carbonization of Fe 4 N/SiO 2 showed significantly higher activity than χ-Fe 5 C 2 in DMO hydrogenation to ethanol. Ethanol synthesis via dimethyl oxalate hydrogenation has garnered increasing attention in the fields of syngas utilization. Although ε-Fe 2 C has been identified as a promising active species for DMO hydrogenation to ethanol, its formation is kinetically challenging during carbonization . In this work, a Fe 4 N phase was first synthesized by pretreating a 30Fe/SiO 2 catalyst in an ammonia environment, followed by carbonization in a methanol-H 2 flow to obtain ε-Fe 2 C as the active phase. Fe 4 N, rather than Fe O Si, facilitates the transformation into iron carbide during the carbonization process. The transformation pathway of iron nitride (Fe x N) is mediated by intermediate iron carbonyl species (Fe CO), ultimately leading to the formation of iron carbide as the active phase. The resulting catalyst exhibited 40 times higher catalytic activity than the untreated catalyst in DMO hydrogenation. Combined structure properties and DFT calculation revealed that the lower energy barrier of ε-Fe 2 C for ester hydrogenation underpins/strengthens its superior performance, while the STY of ε-Fe 2 C is 2.8 times that of ε′-Fe 2.2 C and 58 times that of χ-Fe 5 C 2 . This study provides a novel strategy for designing highly efficient iron carbide catalysts for the esters hydrogenation system.