Surface modification of g-C3N4-supported iron catalysts for CO hydrogenation: Strategy for product distribution

Abstract

Surface modified g-C3N4 supported iron catalysts were prepared using ultrasonic-assisted impregnation and employed as model catalysts to investigate the surface modification effects on product distribution in Fischer–Tropsch synthesis. Characterizations evidenced that both hydroxyl and amino groups were grafted on the g-C3N4 surface. Results showed that the selectivity of light olefins in hydrocarbons was increased from 12.3% on pure Fe3O4 to 31.5% on Fe/C3N4 further to 38.4% on Fe/AMC3N4 under same reaction condition as well as elevated activity owing to electron transfer of amino groups. But high CO2 selectivity was inevitable via the enhanced water gas shift reaction. H2O2 treatment increased the hydrophilicity of g-C3N4, resulting in predominance of water-assisted pathway promoted the chain growth. Compared with Fe/C3N4, the CH4 selectivity for Fe/OHC3N4 was significantly reduced from 38.4% to 22.8%. The Fe/OHC3N4 also exhibited lower CO2 selectivity of 11.4% than Fe/AMC3N4 of 24% due to the enrichment of surface hydroxyl. Surface modification played a critical role in tuning the product distribution and promoting the formation of light olefins with low C1 by products (CH4 and CO2).