A study on catalytic depolymerization of a typical perhydrous coal for improving tar yield

Catalytic depolymerization proposed by our team was used on the thermal decomposition study of a typical perhydrous coal for improving the tar yield. The products from the coal catalytic depolymerization with or without a small amount of ZnCl2 or CoCl2 catalysts were investigated and compared. The composition of the tar and the structure of the coal char were characterized by a comprehensive two-dimensional gas chromatography coupled with mass spectrometric detection (GC x GC-MS), thermogravimetric analysis (TGA), Raman spectrum and Elemental analysis, respectively. Compared with 8.21% of tar yield generated from the depolymerization of the raw coal, the tar yield increased to 9.19% and 10.02% when ZnCl2 and CoCl2 catalysts were added, respectively. The light fractions of tar also increased from 81.71% to 84.02% and 84.51%, respectively. Meanwhile, the yield of the aromatic ring components (> 3 fused benzene rings) and the ratio of aromatic rings with six or more fused benzene rings in the tar decreased. Further analysis reflected that the addition of catalysts in the catalytic depolymerization process could facilitate the cracking of more C-al-O bonds and precipitate the reaction start at lower temperature, which finally increases the volatiles released during the depolymerization stage.