Catalysts for dehydration of isopropyl alcohol based on chlorinated carbon fiber

Abstract

Gas-phase chlorination of carbon fiber based on polyacrylonitrile was performed and active chlorine-containing precursors were obtained, in which chlorine can be replaced by sulfur-containing functional groups. It is shown that chlorination of carbon fiber samples with carbon tetrachloride at temperatures of 300, 450 and 6000C in an argon stream leads to the introduction of 0.2–1.7 mmol g–1 of chlorine into the surface layer of the fiber. The thermodesorption properties of the modified carbon fiber samples were investigated by thermogravimetry and thermoprogrammed desorption with mass spectrometric registration of products. It was established that the obtained samples exhibit a relatively high thermal stability. The study conducted by means of thermoprogrammed desorption method showed that chlorine is desorbed from the surface in a wide temperature range (up to 8000C). It was found that the treatment of chlorinated samples with sulfur-containing reagents with subsequent oxidation produce the samples of carbon fiber with a concentration of sulfo-groups up to 0.3 mmol g–1, which are catalytically active in the dehydration reaction of isopropyl alcohol in the gas phase. The temperature of 50% conversion of isopropyl alcohol to propylene was used as a measure of catalytic activity. It was found that pre-chlorination leads to an increase in the catalytic activity of the fiber modified with sulfur-containing reagents: the temperature of 50% conversion of isopropyl alcohol to propylene is 215–2900C, depending on the concentration of sulfo-groups.