GC-MS and TG-FTIR Study of Petroleum Ether Extract and Residue from Low Temperature Coal Tar

Abstract

The heavy tar (H-tar) of low temperature coal tar was collected from a low temperature carbonization plant in Shanbei. H-tar was extracted with petroleum ether (PE) under ultrasonic irradiation and separated into PE soluble and insoluble fractions. Then, the PE insoluble fraction was extracted in a Soxhlet extractor with PE and methanol (MeOH), respectively. PE extract, PE residue, MeOH extract, and MeOH residue were obtained. PESE (PE soluble fraction and PE extract) and MeOH extract were examined by gas chromatography−mass spectrometry (GC-MS). GC-MS analysis of PESE shows considerable alkanes and extensive series of phenols, naphthalenes, fluorenes, benz[a]anthracene, chrysene, etc. Particularly, the content of methyl phenol is about 9.0%. No GC-MS detectable species are found in MeOH extract. So, additional research will focus on PE residue. The pyrolysis behavior of PE residue was investigated by using a thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). The results indicate that the release of volatiles takes place mainly between 110 and 425 °C and the maximum mass loss rate occurs at 315 °C. The main products in the whole process are CO2, phenols, H2O, saturated hydrocarbons, aromatic compounds, anhydride compounds, oxygen heterocycles, pyridines, etc. But there is no significant peak of CO. The compounds of alkanes, phenols, heterocyclic compounds, and oxygen-containing heterocyclic compounds in PE residue can be also detected. PE residue semicoke (the products of PE residue after TG) and PE residue were estimated by FTIR. PE residue is mainly composed of phenols, aliphatics, and aromatics. The analyses indicate the high degree and polycyclic aromatic structure of PE residue semicoke.