昭通褐煤及其萃取和热溶残渣的13C NMR和XPS研究

s the direct characterization techniques without destroying the structures of samples, solid-state 13C nuclear magnetic resonance (NMR) and X-ray photoelectron spectrometry (XPS) can provide important information on carbon skeleton structures and heteroatom (oxygen, nitrogen, and sulfur) forms.In this study, sequential extraction and thermal dissolution of Zhaotong lignite (ZL) were conducted to obtain extraction residue (ER) and thermal dissolution residue (TDR). Carbon skeleton structures and oxygen-functional groups in ZL, ER, and TDR were analyzed by 13C NMR and XPS tools, respectively. The results show that aliphatic carbons are abundant in ZL and ER, while the TDR is dominated by aromatic carbons. Through extraction and thermal dissolution, the condensation degree of organic species in the TDR is obviously higher than that in ZL and ER. In addition, organic oxygen species in ZL, ER, and TDR are mainly present in the forms of C-O groups.