Fe-modified catalytic carbons for enhanced CO2 gasification: Influence of carbon source and operating conditions

Abstract

In this study, we present results of characterization and reactivity of Fe-doped carbonaceous materials during their catalytic gasification with CO₂. The samples include carbons derived from the thermal treatment of lignocellulosic residues pine sawdust (PiDC) and almond shells (AlDC) and a commercial graphite (AG) used for comparison. Iron-supported samples (Fe/PiDC, Fe/AlDC, Fe/AGC) were prepared by impregnating the raw materials (pine sawdust, almond shells and graphite) with a Fe precursor, followed by thermal decomposition under a reducing atmosphere. Characterization results revealed that Fe incorporation significantly influences the textural properties of the resulting carbonaceous materials. Specifically, Fe doping increased defect density and surface roughness while reducing microporosity, particularly in biomass derived carbons, as the Fe content increased. Dynamic gasification tests demonstrated that Fe enhances the reaction rate and lowers the onset temperature. Optimal gasification performance was achieved with intermediate Fe loadings maximizing catalytic efficiency while preventing rapid deactivation of Fe nanoparticles. Within the temperature range of 850–950 °C, nearly complete gasification was achieved, with residual content minimized to 10 % for Fe(4.2 %wt)/AGC, 16 % for Fe(2.4 %wt)/PiDC and 13 % for Fe(3.2 %wt)/AlDC. However, higher Fe loadings and temperatures exceeding 900 °C led to accelerated Fe deactivation due to sintering and oxidation. At CO₂ concentrations below 8.3 %, these adverse effects were mitigated, optimizing the gasification rate. These findings underscore the critical interplay between Fe dispersion, carbon structure and gasification conditions, offering valuable insights for designing efficient Fe-based catalytic systems for CO₂ valorization in sustainable energy applications.