(6dv) Molecularly Engineered Nanoporous Adsorbents: Synthesis, Characterization, and Application

The controlled synthesis of molecularly engineered materials, a quantitative understanding of mass transport in those materials, and the ability to mathematically model how new materials, equilibria, and mass transfer impact an entire adsorption process are important to developing effective adsorption based separations. This research studies these areas by examining three specific examples: the synthesis and characterization of a novel nanoporous molecularly engineered carbon-silica composite adsorbent material, the use of concentration-swing frequency response to quantitatively determine the mass transfer mechanism in nanoporous materials, and the study of the impact of mass transfer resistances and subsequent optimization of a fixed bed system using a mathematical model.

More specifically, a novel molecularly engineered carbon-silica composite using MCM-41 and polyfurfuryl alcohol has been synthesized and extensively characterized. The novel material shows a nearly uniform pore size near 5 Angstroms, a carbonaceous adsorbent surface, and a high surface area. A novel flow-through, concentration-swing, frequency-response apparatus has been modified to measure the diffusion of condensable vapors in nanoporous materials. To illustrate the application of frequency response to measure the diffusion of condensable liquids for commercially important systems, the diffusion of water vapor at various humidities on silica gel and the diffusion of hexane vapor on activated carbon have been studied. Finally, a mathematical model has been developed to examine the sensitivity of the breakthrough of fixed beds with respect to system parameters. The impact of mass and energy transfer effects and optimal bed layering is determined by calculating the derivatives of the outlet concentration and outlet temperature with respect to process parameters.