Pyrolysis of phthalic acid esters: Their fate

The pyrolysis of die(2-ethylhexyl)phthalate (DEHP) and dibutylphthalate (DBP) in the presence and absence of polyvinyl chloride (PVC) lead to the formation of a number of polynuclear aromatic hydrocarbons (PAH's) such as methylnaphthalene, acenaphthene, fluorene, biphenyl, methylfluorene, and a number of other compounds yet unidentified. We have reason to believe that some of these compounds are formed from a “bezyne” intermediate produced during the high-temperature pyrolysis of DEHP and DBP. It is possible that the DEHP and DBP first decompose to give phthalic anhydride and other fragments, followed by the further decomposition of phthalic anhydride to “benzyne”, carbon dioxide and carbon monoxide.