Pyrolysis characteristics of Shendong coal by CH3OH-THF swelling coupled with in-situ loading of metal ions

The effects of demineralization, CH3OH-THF mixed solvent swelling, CH3OH-THF swelling coupled with in-situ loading of metal ions (Ca2+, Mn2+, Cu2+ and Co2+) on pyrolysis reactivity and kinetic characteristics of Shendong low rank coal were investigated. The structure of coal samples was characterized by solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS C-13 NMR) and Fourier transform infrared spectrometer (FTIR). The pyrolysis characteristics and distribution of pyrolysis products of coal were analyzed by thermogravimetric analyzer/Fourier transform infrared spectrometer (TG-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and the fixed bed reactor. The results show that solvent swelling coupled with in-situ loading of Ca2+, Mn2+, Cu2+ and Co2+ promotes coal pyrolysis, and their net weight losses increase by 2.14 wt%, 0.07 wt%, 6.31 wt% and 6.18 wt%, respectively. Py-GC/MS analysis shows that the treatment of solvent swelling coupled with in-situ loading of metal ions Ca2+, Mn2+, Cu2+, Co2+ can increase the content of aromatic hydrocarbons and decrease the content of acidic compounds in coal tar. The content of benzene increases under the action of solvent swelling coupled with in-situ loading of Cu2+ and Co2+ by 42.73 wt% and 40.98 wt%, respectively. The kinetic calculation shows that the activation energies of the first and second stages of coal pyrolysis are reduced and the reactivity of coal can be improved by swelling coupled with in-situ loading of metal ions.