Experimental Insights into the Oxidative Pyrolysis Mechanism of Chlorobenzene

Chlorinated benzenes are ubiquitously generated in thermal processes, and their continuous transformation into toxic pollutants has caused great concern. However, direct observation of key intermediates in the chlorobenzene oxidative pyrolysis remains inadequate. Here, using synchrotron vacuum ultraviolet photoionization mass spectrometry, we conducted in situ observation of the products and intermediates during chlorobenzene oxidative pyrolysis. Products such as chlorophenol, naphthalene, and chloro-dibenzofuran were detected. Our research directly observed a sequence of radicals, including propargyl (C3H3•), cyclopentadienyl (C5H5•), 2-ethynylphenyl (C8H5•), and 2-vinylphenyl (C8H7•). Temperature-dependent analysis revealed that oxygen promoted chlorobenzene transformation to chlorophenol and phenol at low temperatures. Both phenoxy transformation and phenyl addition had a significant effect on aromatic growth. Diphenyl ether was identified, indicating a key route of phenyl-phenoxy reaction in the formation of dibenzofuran. These findings provided new experimental insights to deepen our understanding of the evolution of chlorobenzene in thermal industrial processes, especially its transformation into naphthalene and dibenzofuran.