Pyrolysis of Huolinhe lignite extract by in-situ pyrolysis-time of flight mass spectrometry

In this paper, tetrahydrofuran extract of Huolinhe lignite was selected as sample and a new in-situ pyrolysis-time of flight mass spectrometry (PY-TOF-MS) was used to study the evolution of initial pyrolysis products of extract. Electron impact mass spectrometry (EI-MS) and vacuum ultraviolet photoionization mass spectrometry (VUV-PI-MS) were used to detect different pyrolysis products. The similarity of DTG curve and ion counts of PY-TOF-MS shows the good performance of the equipment in coal pyrolysis. EI-MS results show that the oxygen containing gases present multiple peaks; however, H2 and CH4 present single evolution peak. More evolution peak numbers of CO2 and H2O in extract pyrolysis than that of coal show that extract has more advantages to investigate the formation mechanisms of CO2 and H2O. VUV-PI-MS is proved to be a useful method to analyze tar components. The aliphatics and aromatics in initial products have relatively larger molecular weight than those of the low boiling point substances in extract. The polycyclic aromatic hydrocarbons have an increasing tendency with ring number. Phenols exhibit different evolution curves, and C7H8O and C8H10O are dominant compounds. These results illustrate that different initial products have different formation mechanisms and oxygen atom plays an important role during pyrolysis.