The objective of this study was to examine the effects of annealing polyimide-organosilicate hybrid membranes on gas transport. In addition, the effects of carbon dioxide pressure on the gas transport of unannealed polyimide-organosilicate hybrid membranes were evaluated. The membranes in both studies consisted of sol-gel derived organosilicate domains covalently bonded to a 6FDA-6FpDA-DABA polyimide using partially hydrolyzed tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMOS) or phenyltrimethoxysilane (PTMOS).
The first study subjected the hybrid membranes to a 400°C annealing process to enhance gas separation performance by altering the organosilicate structures. The hybrid membranes were evaluated before and after annealing using pure gases (He, O₂, N₂, CH₄, CO₂) at 35°C and a feed pressure of 4 atm. The permeability for most of the membranes increased 200-500% after the annealing process while the permselectivity dropped anywhere from 0 to 50%. The exceptions were the 6FDA-6FpDA-DABA-25 22.5 wt% TMOS and MTMOS hybrid membranes, both of which exhibited increases in the CO₂ permeability and CO₂-CH₄ permselectivity. The increase in permeation was attributed to increases in the free volume and enhanced segmental mobility of the chain ends resulting from the removal of sol-gel condensation and polymer degradation byproducts.
For the second study, the transport properties of four membranes, 6FDA-6FpDA polyimide, 6FDA-6FpDA-DABA polyimide, MTMOS and PTMOS-based hybrid materials, were characterized as a function of feed pressure to evaluate how the hybrid materials reacted to CO₂ plasticization. Steady-state gas permeation experiments were performed at 35°C using pure CO₂ and CH₄ gases at feed pressures ranging from 4 to 30 atm. All four materials exhibited dual mode sorption up to feed pressures of 17 atm, at which point the effects of CO₂ plasticization were observed. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/32357 |
| Date | 10 May 2002 |
| Creators | Hibshman, Christopher L. |
| Contributors | Chemical Engineering, Marand, Eva, Saraf, Ravi F., Davis, Richey M. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | Etd.pdf |
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