Transformation of doped Fe in pitch sphere in carbonization and activation processes

Ferrocene was added into the starting pitch in order to produce the pitch-based spherical activated carbon with mesopore (PSAC-M) forms of doped Fe in different stages—stabilization, carbonization, and activation—during the preparation process of the PSAC-M being analyzed using Mössbauer spectroscopy (MES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Ferrocene was oxidized into α-Fe2O3 at the stabilization step. The major portion of α-Fe2O3 was reduced into α-Fe during carbonization at 900°C, which was subsequently transformed into Fe3C by 1200°C. No obvious sintering or agglomeration of iron particles occurred during carbonization process even when the carbonization temperature was as high as 1200°C. The activation re-oxidized α-Fe into γ-Fe2O3, which aggregated and grew up along with the activation time and iron content.