Perfluorosulfonic acid polymer composites: Effect of the support and synthesis method on the acid and catalytic properties

Several composite samples containing perfluorosulfonic acid polymer (PFSA; e.g. Nafion) over silica, carbon nanofibers or zirconia were synthesized to determine the effect of the support on the acid catalytic properties. The synthesized composites contained 5-25 wt.% of the perfluorosulfonic acid polymer with variable concentration of sulfonic groups (equivalent weight of PFSA). The acidity of the composites was investigated by titrimetric techniques, in a model catalytic reaction between resorcinol and ethyl acetoacetate, by EPR using spin probes and by temperature programmed desorption of propylene. It is shown that impregnation of silica with high surface area or mesoporous carbon nanomaterials yields samples with characteristics exceeding commercially available SAC (Nafion over silica) samples. A method for synthesis of zirconia-based catalytic composites was developed. It was shown that despite the relatively low catalytic activity (compared to PFSA/SBA-15 and PFSA/CNF samples) these samples have increased resistance to the PFSA desorption. So, polymers with lowequivalent weight characterized by higher acidity can be used.