Fractionation And Sequential Thermal Dissolution Of Medium-and Low-rank Coal

In order to study the small soluble organic molecules and the dissolved organicmacromolecule clusters in medium-and low-rank coals, Xilinhaote lignite (XL), Huolinguolelignite (HL) and Zhundong subbituminous (ZSB) were selected in this subject. After beingextracted with acetone or carbon disulfide-acetone mixed solvent at mild conditions, they werethen sequential thermal depolymerized with methanol.The resulting products were analyzed with GC/MS. The results show that theGC/MS-detectable species can be classifed into hydroxybenzenes (HBs), esters, ketones,alcohols, arenes, methoxybenzene (MBs), alkanes, alkenes, nitrogen-containing organiccompounds (NCOCs), sulfur-containing organic compounds (SCOCs), aldehydes and othercompounds (OCs). These results suggest that XL is rich in Ar-CH₂-O,-(CH₂)₁₉CH₃andCH₃(CH₂)₂₂COO moieties, while ZSB is rich in Ar COO and R COO orCH₃(CH₂)₂₂COO moieties in their macromolecules. XL was depolymerized in supercriticalmethanol at310oC with or without air and the resulting products were investigated withnonparametric statistics. The p-value of nonparametric statistics demonstrates that the groupcomponents and relative molecular mass distribution of the products from supercriticalmethanolysis of XL without and with air are not significantly different.In order to investigate the detailed methanolysis mechanisms for medium-and low-rankcoals, we used ReaxFF reactive force feld to perform a series of molecular dynamicssimulations (MDSs) on unimolecular model compound. Phenyl butyrate, propyl benzoate,(1S,2S)-1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy) propane-1,3-diol (1) and2-methoxy-4-((2-methoxyphenoxy)methyl)phenol (2), were selected as representatives oflinkages in medium-and low-rank coals. The reaction products predicted by ReaxFF MDSs areconsistent with those from experimental results reported. For the MC1and MC2, theinitiation reaction observed in ReaxFF MDSs involving cleavage of the ether linkage andparticipation of methanol closely matches with the results observed from previously reportedexperiments. For the phenyl butyrate and propyl benzoate, the most favorable reaction pathwayis the attacking of oxygen atom of hydroxyl moiety in methanol on the carbon atom ofaliphatic ethers in MCs. However, the reaction pathway related to reaction between the carbonatom of methanol and the oxygen atom of carbonyl in MCs, leading to the formation ofbiradicals, is difficult to react.