Add time:07/17/2019         Source:sciencedirect.com

Hybrid ceramic materials with amine function are prepared from aminopropyltriethoxysilane or bis(trimethoxysilylpropyl)amine as aminopropyl group bearing polysiloxane precursors. Methyl and methyl phenyl polysiloxane precursors are used to influence the hydrophobicity of the material. The materials are converted by inert gas pyrolysis at low temperatures (300–600 °C) to improve the applicability for CO2 gas separation. NaOH back titration is used to determine the number of basic sites and is compared to the amount of nitrogen for selected material compositions. The micro-structure and surface characteristics are investigated by nitrogen and water vapor sorption isotherms as well as CO2 adsorption.CO2-philic amine groups are observed after pyrolysis at temperatures up to 350 °C. The amine group bearing material derived from aminopropyltriethoxysilane shows a low sorption capacity for nitrogen at −196 °C. The CO2 sorption capacity of this material increases with the sorption temperature up to 1.1 mmol g-1 measured at 100 °C. Besides CO2 the material also adsorbs large amounts of water at room temperature. The hydrophobic precursors are shown to diminish water adsorption but to increase the CO2 sorption capacity per amine group. In the case of bis(trimethoxysilylpropyl)amine the material is mesoporous and displays high specific surface areas (364–629 m2 g−1). The high CO2 sorption capacity after pyrolysis at 350 °C (1.9 mmol g-1) decreases with increasing sorption temperature. Cross-linking of bis(trimethoxysilylpropyl)amine with hydrophobic precursors has not a great influence on both, CO2 sorption capacity per amine group and water sorption isotherms. Bis(trimethoxysilylpropyl)amine derived material should be less prone to problems of interactions with CO2 in the presence of water.

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