Thermal dissolution of Naomaohu sub-bituminous coal and catalytic hydroconversion of its soluble portions

Naomaohu sub-bituminous coal (NMH) was thermally dissolved in isometric methanol/toluene mixed solvent affording soluble portions (SPs) and thermal dissolution residues (R_TD), then hydroconversion of SP₃₂₀ was catalyzed over Co/C@N-700 catalyst affording CSP₃₂₀. The composition and structural characteristics of SP₃₂₀ before and after catalytic hydroconversion were analyzed with a gas chromatograph/mass spectrometer (GC/MS), and pyrolysis reactivity and structural characteristics of NMH and R_TD were characterized with Fourier transform-infrared spectroscopy (FT-IR), thermogravimetry, as well as solid state ¹³C nuclear magnetic resonance (¹³C NMR). The SPs yields increase with increasing temperature, and reach a maximum (36.46%) at 320 ^oC. GC/MS analysis shows that SP₃₂₀ are mainly composed of alkanes, phenols and arenes, and their relative contents are 45.45%, 18.03% and 24.75%, respectively. After catalytic hydroconversion, relative contents of arenes and phenols in CSP₃₂₀ decrease to 3.86% and 13.6%, respectively, while those of alkanes and alcohols increase to 66.99% and 9.36%, respectively, and kinds of cycloalkanes increase from 8 to 24. These results indicate that arenes and phenols in SP₃₂₀ could be hydrogenated into alkanes and alcohols catalyzed by Co/C@N-700. Compared to NMH, R_TD possesses higher thermal stability, more aromatic carbons, and less carbonyl carbons in its skeleton structure. In addition, intensity of adsorption peaks attributed to O−H, −CH₂−, C=O and C−O−C in the FT-IR spectrum of R_TD are weaker, while adsorption peaks assigned to aromatic C=C are stronger than those of NMH.