Recovery of volatile solutes from dilute aqueous solutions using immobilized silicalite

A silicalite/polyethylene mixture was sintered to the exterior of a heat exchanger tube allowing regeneration by steam or hot water, rather than by inefficient, hot stripping gases. Ethanol, acetone, and butanol were adsorbed onto the silicalite until a final bulk concentration of 4 g/L was obtained. Single-step desorption would enrich ethanol 5.2 times, 1-butanol 9.3 times, and acetone 10.1 times. In an attempt to increase the product concentration even more, the silicalite was regenerated using “temperature-programmed desorption,” where the water was selectively removed at a lower temperature and the solute was selectively removed at a higher temperature. The high-temperature desorption enriched ethanol up to 11.1 times, 1-butanol 4.44 times, and acetone 22.1 times, but at the expense of lower solute recovery. Temperature-programmed desorption was able to significantly enrich the product compared to single-step desorption except for butanol, for which higher regeneration temperatures were required.