Fractionated And Sequential Thermal Dissolution Of Xianfeng And Shengli Lignites

Xianfeng and Shengli lignites (XL and SL) were selected in this subject. The coalsamples were firstly thermal dissolved in cyclohexane at200oC,240oC,280oC and320oCrepeatedly. And then the insoluble fraction was then taken as the feed in fractionated thermaldissolution processes (FTDP) at320oC, with benzene, methanol, ethanol and isopropanol,respectively, followed by the investigation of the hydrogen transfer by anthracene, which waschosen as an acceptor of active hydrogen to prove whether there is a hygrogen transferexisting in FTDP. According to the dissolving rules and structural characteristic of organiccompounds detected by modern analysis instruments along with the results of hydrogentransfer investigation, the possible pathways in FTDP and origin of active hydrogen werediscussed.The partical sizes of the coal samples turn smaller after the FTDP. Pyrolysis temperatureraises to about500oC. Besides, the absorption peaks of hydroxy, aliphatic hydrocarbon, etherand arene in residues become weaker compared to the raw coals.XL is rich in mononuclear aromatics which are eazy to be dissolved. Cycloalkanes arefound in SL, which is absent in XL dissolved fractions. where a large amount of alkenes areobserved.It is noticed that no normal methyl alkanoates detected in the methanol thermaldissolution products (TDPs), which may attribute to thermal decarboxylation in long-chaincarboxylic acids during former thermal dissolution. Compared to the phenomenon above, aseries of normal ethyl alkanoates were found in ethanol TDPs. The interaction betweenehanol and oxygen bridge bond is stronger than that between methanol and oxygen bridgebond. The oxygen atom in ethanol could attact carbon atoms adjacent with bridge-bondoxygen, resulting ethyl esters and another alcohol.Hydrogen transfer is relatively weak in benzene and cyclohexane thermal dissolutionprocess. The activated hydrogen may derived from pyrolysis. While, hydrogen transfer inalcohols at320oC is effective. Transesterification and the interaction betweenalkyloxybenzene and alcohols may be the major source of the activated hydrogen.