Novel Nanoporous Composite Materials for Light Gas Adsorption

Abstract

This research addresses the synthesis and development of biphasic, nanoporous composite materials for use in single pass filters of various types for the removal of light acidic and basic gases from humid air. Potential applications of the new adsorbent materials range from military and first responder protective masks to industrial filters.

Research into several different composite materials is considered, including mesoporous silica impregnated with metal salts, a metal organic phase, carbonaceous phases, and organoalkoxysilanes. The research also includes an organoalkoxysilane-modified zirconium hydroxide composite. The materials are characterized using a plethora of analytical techniques including nitrogen isotherms, BET surface areas, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. They are also tested for light gas capacities of ammonia and sulfur dioxide using a breakthrough apparatus.

Of the materials reviewed in this work, the organoalkoxysilane-modified composites exhibit the highest single pass capacities for sulfur dioxide, a representative acidic gas, and ammonia, a representative basic gas. A siliceous MCM-41 support provides high capacity for ammonia, and a zirconium hydroxide support provides high capacity for sulfur dioxide. Functional groups including carbonyls and amines grafted onto the supports provide ammonia and sulfur dioxide capacity, respectively. Two organoalkoxysilane molecules have also been grafted onto the supports to optimize the capacities. For example, MCM-41 has been grafted with 3-aminopropyltriethoxysilane, which contains an amine functional group, as well as 3-triethoxypropylsilyl isocyanate, which contains a carbonyl group, to produce an adsorbent with high capacities for both sulfur dioxide and ammonia. The resulting biphasic materials have high adsorption capacities for these gases, and the adsorbents can be easily tuned to capture a predominant amount of either gas.