An evidence for the strong association of N-methyl-2-pyrrolidinone with some organic species in three Chinese bituminous coals

Abstract

Three Chinese bituminous coals collected from Shenfu, Heidaigou and Feicheng coal fields were respectively extracted with carbon-disulfide/N-methyl-2-pyrrolidinone (CS2/NMP) mixed solvent (volume ratio 1:1) at room temperature followed by distillation of CS2 under ambient pressure and subsequent removal of most of NMP by distillation at 110°C under reduced pressure to afford mixed solvent-extractable fractions (MSEFs) with small amount of NMP. Acetone-extractable fraction 1 (AEF1) was obtained by extracting each MSEF under ultrasonic irradiation at room temperature and subsequently using a Soxhlet extractor. Direct extraction of each bituminous coal affords acetone-soluble fraction 2 (AEF2). GC/MS analysis shows that m/z of base or secondary peak in mass spectra of a series of components from each AEF1 is 98, whereas such components were not detected in AEF2. Since m/z of base peak in mass spectrum of NMP itself is 99, the base or secondary peak at m/z 98 should result from loss of α-H from NMP, i.e., NMP is strongly associated with some organic species (OSs) and thereby the components detected with base or secondary peak at m/z 98 in their mass spectra should be associated NMP-OS.