The synthesis and study of the physicochemical and catalytic properties of composites with the sulfated perfluoropolymer/carbon nanofiber composition

Resumo

Composites with the sulfated perfluoropolymer (SFP) (Nafion, etc.)—mesoporous support composition (SFP/support)—are promising solid acid catalysts with strong acid sites and very stable sulfo groups towards leaching processes. The effect of the SFP on the carbon nanofiber (CNF) (SFP/CNF) composite synthesis method, as well as the precursors of the acid phase, on the key acid catalyst characteristics (specific surface area and concentration and accessibility of the acid sites) is studied. The possibility of the direct composite synthesis from SO₂F-polymer latexes obtained as a result of the water emulsion SFP synthesis (without the intermediate stages of isolating the SO₃H form) is shown. The acid phase precursor types which are acceptable for the SFP/CNF composite synthesis (the equivalent polymer weight > 580 g/mol) are selected. The effect of the amount of the supported polymer on the total specific surface area and concentration and accessibility of the composite acid site is investigated. The structure of the synthesized composites is studied (by TEM, SAXS, and isopropanol TPD), and their catalytic activity in the test acetic acid esterification reaction is compared to the catalytic activity of pure polymer samples and acetic acid. It is found that the synthesized SFP/CNF samples outperform commercial SFP/SiO₂ samples (SAC, DuPont), as well as the SFP/CNF samples prepared using polymer solutions in the SO₃H form, in terms of the catalytic characteristics.