Study on the formation of phenols during coal flash pyrolysis using pyrolysis-GC/MS

• The source of phenols was proposed during coal pyrolysis.
• Phenols of lignite is the highest (2316 μg/g) during different rank coal pyrolysis.
• Most phenols were formed by the thermal cracking of aryl ether at 600–800 °C.
• Phenols amount is augmented with the increasing SSA during coal pyrolysis.

Phenols from coal pyrolysis are extremely precious chemicals, understanding the factors that influence the amounts and species of phenols during coal pyrolysis is of vital importance. In this study, the concentrations of seven species of phenols in the coal extracts were analyzed by GC/MS. Then, the phenols obtained from the pyrolysis of four different coals were characterized by using a flash pyrolysis-GC/MS in-situ. In addition, the amounts of phenols from coal pyrolysis at 400–1000 °C with the heating rate of 10 °C/ms were calculated. Results show that the total amount of phenols during the pyrolysis of lignite (coal A) was higher than those of long-flame coal (coal B), bituminous coal (coal C), and anthracite (coal D) at 800 °C. The main source of phenols is the thermal decomposition of the oxygen-containing structures, particularly aryl ether, rather than the volatilization of the already existing phenols in the raw coal. The formation of phenols, dominated by phenol and cresols, is facilitated during the coal pyrolysis at 600–800 °C, otherwise, certain phenols may be decomposed at higher temperatures. Moreover, there is close correlation between the release amount of phenols and the specific surface area of the coal during coal pyrolysis.