Studies on the Thermal Decomposition of Phthalic Acid Esters. V. Thermal Decomposition of Di-n-butylphthalate and Analysis of Its Decomposed Products

Abstract

As a study of the thermal behavior of phthalic acid esters (PAE's), the thermal decomposition of di-n-butylphthalate (DBP) was carried out in a flow system at 250-500°. The major products were butene-1, butanol and phthalic anhydride (PA). Benzoic acid, butyl benzoate, phthalic acid and monobutyl phthalate (monoester), as minor products, were also isolated and identified. These minor products, especially phthalic acid and monoester, were so unstable to the heat treatment that they were not isolated in a conventional GC analysis. A simple one step analysis was achieved by the use of a GC, by pretreating the products with diazomethane to improve their heatstability. This analytical method made clear the composition of commercial polyvinyl chloride sheet (PVC) for agricultural use. It was found that the plasticizer it originally contained, di (2-ethylhexyl) phthalate (DEHP), were partially decomposed and identified the decomposition products. 2-Ethylhexanol, PA and mono 2-ethylhexyl phthalate, the thermal decomposition products of DEHP, were analyzed to be 0.1%, 0.7% and 0.1% of the products, respectively.