Thermal decomposition of PFOA: Influence of reactor and reaction conditions on product formation

The thermal decomposition of perfluorooctanoic acid (PFOA) was studied in an a-alumina flow reactor between 400 and 1000 degrees C. Experimental results indicate that the thermal decomposition of PFOA is initiated at 400 degrees C and that at temperatures below 600 degrees C, the primary products are perfluoroheptene (C7F14), CO2, and HF, together with minor amounts of perfluoroheptanoyl fluoride (C7F14O) and CO. These results contradict quantum chemical calculations that predict HF, CO, and C7F14O to be the major products formed via a lactone intermediate. Through quantum chemical calculations, we discovered that PFOA can be physisorbed onto an alumina nanocluster and can release C7F14 and CO2. Adding more a-alumina surface area confirmed a significant increase in CO2 concentration, supporting the postulate that an a-alumina surface impacts the thermal decomposition of PFOA. Temperatures above 600 degrees C were found to result in an increased yield of HF and CO and fluorocarbons.