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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Synthesis and Characterization of ZIF-71/PDMS Membranes for Biofuel Separation

January 2017 (has links)
abstract: Membranes are a key part of pervaporation processes, which is generally a more efficient process for selective removal of alcohol from water than distillation. It is necessary that the membranes have high alcohol permeabilities and selectivities. Polydimethylsiloxane (PDMS) based mixed matrix membranes (MMMs) have demonstrated very promising results. Zeolitic imidazolate framework-71 (ZIF-71) demonstrated promising alcohol separation abilities. In this dissertation, we present fundamental studies on the synthesis of ZIF-71/PDMS MMMs. Free-standing ZIF-71/ PDMS membranes with 0, 5, 25 and 40 wt % ZIF-71 loadings were prepared and the pervaporation separation for ethanol and 1-butanol from water was measured. ZIF-71/PDMS MMMs were formed through addition cure and condensation cure methods. Addition cure method was not compatible with ZIF-71 resulting in membranes with poor mechanical properties, while the condensation cure method resulted in membranes with good mechanical properties. The 40 wt % ZIF-71 loading PDMS nanocomposite membranes achieved a maximum ethanol/water selectivity of 0.81 ± 0.04 selectivity and maximum 1-butnaol/water selectivity of 5.64 ± 0.15. The effects of synthesis time, temperature, and reactant ratio on ZIF-71 particle size and the effect of particle size on membrane performance were studied. Temperature had the greatest effect on ZIF-71 particle size as the synthesis temperature varied from - 20 to 35 ºC. The ZIF-71 synthesized had particle diameters ranging from 150 nm to 1 μm. ZIF-71 particle size is critical in ZIF-71/PDMS composite membrane performance for alcohol removal from water through pervaporation. The membranes made with micron sized ZIF-71 particles showed higher alcohol/water selectivity than those with smaller particles. Both alcohol and water permeability increased when larger sized ZIF- 71 particles were incorporated. ZIF-71 particles were modified with four ligands through solvent assisted linker exchange (SALE) method: benzimidazole (BIM), 5-methylbenzimidazole (MBIM), 5,6- dimethylbenzimidazole (DMBIM) and 4-Phenylimidazole (PI). The morphology of ZIF- 71 were maintained after the modification. ZIF-71/PDMS composite membranes with 25 wt% loading modified ZIF-71 particles were made for alcohol/water separation. Better particle dispersion in PDMS polymer matrix was observed with the ligand modified ZIFs. For both ethanol/water and 1-butanol/water separations, the alcohol permeability and alcohol/water selectivity were lowered after the ZIF-71 ligand exchange reaction. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2017

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