Exploration of the sulfur removal mechanism of diphenyl sulfone loaded on activated carbon during Fe-assisted pyrolysis

Iron-assisted pyrolysis (Fe-assisted pyrolysis) is a high-efficiency technique to remove sulfur from low-rank coal. However, the sulfur removal mechanism of Fe-assisted pyrolysis did not compressively address. For filling this gap, this study explored the sulfur removal mechanism of diphenyl sulfone during Fe-assisted pyrolysis based on the factor optimization of desulfurization performance. The iron powder under the optimal conditions of Fe-assisted pyrolysis was characterized with X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS), showing that FeS and some FeS2 were formed on the surface of post-pyrolysis iron powder. Gas chromatography (GC) analysis manifested that the addition of iron powder in the pyrolysis process could considerably reduce the SO2 emission. GC and Fourier transform infrared spectrometer (FTIR) analyses demonstrated that there was C–S bond broken in the diphenyl sulfone structure during Fe-assisted pyrolysis. From the results of thermogravimetry-mass spectrometry (TG-MS), the addition of iron powder in the pyrolysis process could enhance the reaction rate and reduce the temperature required for the reaction. We believe that the results of the present study provided a theoretical basis for a profound understanding of the desulfurization mechanism of Fe-assisted pyrolysis.