435158 Membranes for Energy-Efficient Separations

Sunday, November 8, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Zachary P. Smith, Department of Chemistry, University of California, Berkeley, Berkeley, CA; McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, TX

Gas and vapor separations in the petrochemical industry are often accomplished with energy-intensive and environmentally harmful processes such as distillation and absorption, so a need exists to identify new, environmentally benign, and more energy-efficient separation technologies.  Of particular promise are membrane-based separations, which, unlike distillation, do not require a thermal driving force, and, unlike absorption, operate under steady-state conditions without the need for regeneration.  However, in their current form, membranes often do not possess the requisite productivity, efficiency, and chemical stability needed to compete with traditional separation technologies.   To overcome these challenges, new polymer membranes and composite membranes, containing highly-structured, inorganic materials that far surpass the separation performance of pure polymers, are needed. 

Separations with dense polymer membranes are accomplished by selectively permeating molecules, and permeation, in turn, is governed by the product of molecular diffusion rates and gas sorption in membranes.  Both of these factors can be tuned to control separation performance.  My graduate research focused on two distinct families of polymers, both of which showed outstanding separation properties for certain gas pairs.  One family of polymers achieved their separation performance based on selective diffusion (i.e., thermally rearranged polymers) and the other on selective sorption (i.e., perfluoropolymers).  My postdoctoral research focuses on extending the limit of membrane performance by synthesizing and characterizing mixed-matrix membranes, whereby metal-organic framework (MOF) nanoparticles with unsaturated metal sites are suspended into polymer matrixes.  MOFs are porous, crystalline materials that have fundamentally different separation property sets compared to those of pure polymers.  Additionally, the metal cations and organic linkers used to build MOFs can be modified to precisely tune porosity, crystalline space groups, and MOF-molecule adsorption and diffusion characteristics, thereby providing a novel platform of porous materials for achieving more efficient separations.

My research interests are in understanding the fundamental structure-property relationships of gas sorption and transport in both polymers and organic/inorganic composite materials.  These interests interface between chemical engineering, chemistry, and materials science, where fundamental research expertise is needed to synthesize and characterize novel polymers and nanomaterials, and applied research expertise is needed to characterize permeation, sorption, and diffusion rates of molecules through these diverse systems.  Creating new polymeric and composite materials needed to revolutionize separation practices currently used in industry will remain a primary focus in my future research.  Synthetic work will focus on designing new polymers and new MOF nanocrystals, and characterization work will focus broadly on gas separations and exploring membrane performance under aggressive, high-temperature, gas-phase vapor-vapor separations.

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