Experimental and Theoretical Study on the Pyrolysis Mechanism of Three Coal-Based Model Compounds

An experimental study of three coal-based model compound (anisole, phenyl ethyl ether, and p-methyl anisole) pyrolysis was carried out at low pressure (below 50 Pa) within the temperature range from 573 to 1323 K. The pyrolysis process was investigated by detecting the reactants, radicals, and products using vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry. The similarities and differences of three model compounds in the pyrolysis process were discussed. The results suggested that the radical reactions were dominant in the pyrolysis process at higher temperatures, whereas the intermolecular reactions were significant at lower temperatures. beta-H was a key factor for the non-radical reactions. The PhO-C homolytic bond scission was the first step for the radical reaction. Substituents on the benzene ring play an important role in the pyrolysis process of phenyl ethers, which can directly form conjugated stable structure compounds. These observations were supported by our theoretical calculation at the mPW2PLYP level.