Activated carbon fibers modified with sulfur-containing functional groups

Activated carbon fibers (ACFs) made from polyacrylonitrile and viscose were treated with the sulfur vapor at the temperatures of 500–800 °C in an argon flow. Obtained materials were oxidized by 30% H2O2 water solution in order to convert S-containing surface moieties into SO3H-groups. The samples were studied using Boehm titration, thermogravimetric analysis and temperature-programmed desorption with a mass spectrometric registration of gaseous desorption products. According to obtained data, the surface layer of synthesized samples contains grafted SO3H-groups and different functional groups formed at the carbon oxidation. The decomposition of SO3H-groups occurs in the temperature range of 75–590 °C. Two peak maxima at 200±30 °C and 300±30 °C were registered on all SO2 desorption profiles. These maxima are assigned to two forms of surface SO3H groups having a different chemical environment. Testing of the catalytic activity shows that SO3H-functionalized carbon fibers are high active in the model reaction of propan-2-ol dehydration. The total conversion of propan-2-ol to propene is observed at 145–220 °C. The lowest temperature of total conversion was registered for the ACFs prepared from polyacrylonitrile being treated with the sulfur vapor at 500 °C. All SO3H-functionalized samples maintain their activity after repeated use.