Positive Catalytic Effect and Mechanism of Iron on the Gasification Reactivity of Coke using Thermogravimetry and Density Functional Theory

Abstract

The catalytic gasification characteristics and kinetics of metallurgical coke by iron were investigated by non-isothermal thermogravimetry using volumetric (VM), unreacted core (URCM), and random pore (RPM) models. Density functional theory (DFT) calculations were used to analyse the interaction mechanism of CO₂ on the iron catalyst surface. Carbon conversion curves were shifted to a lower-temperature zone upon iron addition, indicating the strong catalytic effect of iron on carbon gasification. Kinetic analysis showed that RPM described coke gasification better than VM and URCM, with an RPM activation energy of 197.1–218.1 kJ/mol. DFT calculations indicated that CO₂ molecules parallel to the crystal surface can easily interact with the iron surface. Three stable adsorption configurations with energies of −0.59, −0.62, and −0.78 eV were obtained. In the Löwdin population analysis, the C atom acts as a major electron acceptor from Fe. The C and O orbitals overlap with Fe 3d, 4s, and 4p, indicating stronger hybridisation and demonstrating that Fe (001) can activate CO₂.