Online Study on the Catalytic Pyrolysis of Bituminous Coal over HUSY and HZSM-5 with Photoionization Time-of-Flight Mass Spectrometry

Pyrolysis is considered to be a simple and effective method for the clean conversion of coal. In this work, catalytic pyrolysis of bituminous coal over two commercial available zeolites, i.e., HZSM-S and HUSY, was investigated with newly constructed pyrolysis photoionization time-of-flight mass spectrometry (Py-PI-TOFMS) in real time. The fragment-free mass spectra of coal pyrolysis products at different pyrolysis temperatures were measured. Products such as alkanes, alkenes, dienes, phenols, aromatics, and small amounts of NH3 and H2S could be detected. The abundant products at a relatively low temperature (500-600 degrees C) are phenols. With the presence of zeolites, the product distribution could be observed from the mass spectra. Temperature effects for pyrolysis products show some different tendencies with and without HZSM-5 and HUSY as a result of different acidities and pore sizes of the catalysts. Time-evolved profiles of major products were also measured during the pyrolysis processes. The temperature and catalyst can both dramatically affect the reaction rates. Our work demonstrates the good performance of Py-PI-TOFMS for the online study of the bituminous coal pyrolysis. In addition, it can be used to evaluate the performance of different catalysts.