Abstract:

Shenfu Dongsheng (SD) coal liquefaction is a critical part for the energy diversification strategy in China. However, because of the unique behavior of Chinese western coal macerals during the liquefaction process, no theory exists that explains the difference between Shenfu Dongsheng inertinite (SDI) and vitrinite (SDV) and Chinese eastern coal macerals. The different thermochemistry of inertinite and vitrinite cannot be explained by only considering the structure of these coals. To investigate the unique behavior of SDI and SDV in the liquefaction process a qualitative analysis of the characteristics and transformation of covalent bonds during pyrolysis of the‘average’molecular structure of a SD coal was performed using quantum chemistry, molecular mechanics and molecular dynamics. The formation of residual coal, pyrolyzed gases and tar during pyrolysis was simulated. Results showed that the activity of SDI was higher than that of SDV during cracking and initially CO2 was released without destroying the macromolecular structure. From a statistical analysis of bond order in the molecular model, the amount of broken covalent bonds in SDV was found to be far more than that found in SDI after pyrolysis. When SDI cracked further during pyrolysis, the extent of inertinite decomposition eventually reached the same level as that for vitrinite. There was a difference in pyrolysates from SDI and SDV and there were mainly aliphatic hydrocarbons and single-ring aromatic hydrocarbons for SDV while dual-ring aromatic hydrocarbons were dominant after SDI pyrolysis. Molecular fragments obtained from quantum chemical calculations were compared to thermal gravimetric analyzer-mass spectrometry (TG-MS) data and found to agree well.

Key words: Shenfu Dongshen coal macerals, Pyrolysis, Quantumchemistry, Thermal gravimetric analyzer-mass spectrometry