The influence of inorganic materials on the pyrolysis of polytetrafluoroethylene. Part 1: The sulfates and fluorides of Al, Zn, Cu, Ni, Co, Fe and Mn

•PTFE was pyrolysed in the presence of aluminium- and fourth period metal compounds.•Al2(SO4)3 and NiSO4 were shown to increase the yield of hexafluoropropylene.•AlF3 was shown to produce exclusively hexafluoropropylene and hexafluoroethane.•Cu2+ and Co2+ compounds produced waxy substances.•The other metal fluorides were shown to be generally inactive as catalysts.

The thermal decomposition of PTFE intimately mixed with the solid sulfates and fluorides of selected metals (Al2(SO4)3, ZnSO4, CuSO4, NiSO4, CoSO4, FeSO4, AlF3, CuF2, NiF2, CoF2, FeF2 and MnF2) was investigated by TGA-FTIR. It was found that the sulfates affect the rate of pyrolysis with CuSO4 lowering mass-loss onset temperature by 60 °C. The fluorides have no effect on the pyrolysis rate, with the exception of AlF3 which lowers the onset temperature by 35 °C. It was also found that Al2(SO4)3 and NiSO4 moderately increase the yield of hexafluoropropylene, and that AlF3 shifts the product composition to almost exclusively hexafluoropropylene and hexafluoroethane.

Graphical abstractThe catalytic pyrolysis of PTFE was investigated using AlF3, Al2(SO4)3 and the sulfates and fluorides of selected fourth period transition metals. Product shifts favouring hexafluoropropylene formation were observed with Al2(SO4)3 and NiSO4. Near exclusive production of hexafluoropropylene and hexafluoroethane were observed with AlF3.Figure optionsDownload full-size imageDownload as PowerPoint slide