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Mass Transfer Kinetics of Novel Asymmetric Hollow-fiber Membranes

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This report investigates the mass-transfer kinetics of gas diffusion through an asymmetrical hollow-fiber membrane developed for the membrane biofilm reactor (MBfR) when it is used to microbiologically convert syngas (a mixture of H2, CO2, and CO) to organic products.

This report investigates the mass-transfer kinetics of gas diffusion through an asymmetrical hollow-fiber membrane developed for the membrane biofilm reactor (MBfR) when it is used to microbiologically convert syngas (a mixture of H2, CO2, and CO) to organic products. The asymmetric Matrimid® membrane had superior diffusion fluxes compared to commercially available symmetric, three-layer composite and polypropylene single-layer membranes. The Matrimid® asymmetric membrane had a H2 gas-gas diffusion flux between 960- and 1600-fold greater than that of the composite membrane and between 32,000- and 46,800-fold greater than that of the single-layer membrane. Gas-gas diffusion experiments across the Matrimid® membrane also demonstrated plasticization behavior for pure CO2 and H2 gas feeds. In particular, a 10 psia increase in inlet pressure resulted in a 12-fold increase in permeance for H2 and a 16-fold increase for CO2. Plasticization was minimal for symmetric composite and single-layer membranes. Thus, diffusion fluxes were much higher for the asymmetric membrane than for the symmetric composite and single-layer membranes, and this supports the promise of the asymmetric membrane as a high-efficiency means to deliver syngas to biofilms able to convert the syngas to organic products. Gas-liquid diffusion was much slower than gas-gas diffusion, and this supports the benefit of using the MBfR approach over fermentation reactors that rely on sparging syngas.

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2018-05

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Bi-phase Synthesis of the Zirconium Metal-Organic Framework, UiO-66

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Metal-organic frameworks (MOFs) are a new set of porous materials comprised of metals or metal clusters bonded together in a coordination system by organic linkers. They are becoming popular for gas separations due to their abilities to be tailored toward

Metal-organic frameworks (MOFs) are a new set of porous materials comprised of metals or metal clusters bonded together in a coordination system by organic linkers. They are becoming popular for gas separations due to their abilities to be tailored toward specific applications. Zirconium MOFs in particular are known for their high stability under standard temperature and pressure due to the strength of the Zirconium-Oxygen coordination bond. However, the acid modulator needed to ensure long range order of the product also prevents complete linker deprotonation. This leads to a powder product that cannot easily be incorporated into continuous MOF membranes. This study therefore implemented a new bi-phase synthesis technique with a deprotonating agent to achieve intergrowth in UiO-66 membranes. Crystal intergrowth will allow for effective gas separations and future permeation testing. During experimentation, successful intergrown UiO-66 membranes were synthesized and characterized. The degree of intergrowth and crystal orientations varied with changing deprotonating agent concentration, modulator concentration, and ligand:modulator ratios. Further studies will focus on achieving the same results on porous substrates.

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2016-12