Sol-Gel Route to Carbon-Silica Molecular Sieving Adsorbents

Abstract

Molecular sieve adsorbents have been prepared by the sol-gel route comprising simultaneous hydrolysis of tetraethylorthosilicate (TEOS) and polymerization of furfuryl alcohol (FA). The mixtures of TEOS (10%) and FA (90%) have been forced to interaction in the presence of small amounts of water (hydrolyzing agent) and sulfuric acid (polymerization catalyst) under ambient conditions, and successive carbonization at 923–1,023 K under argon. Adsorption of nitrogen at 77 K appears to be essentially non-equilibrium indicating activated character of diffusion. The ratio of CO₂/N₂ adsorption uptake at 1 bar changes from 9:1 for carbon, obtained without TEOS additives under other similar conditions, to ∼1:3 for carbon-silica composite, indicating the reciprocal change of the adsorption selectivity factor.