Advanced gas separation membrane materials: Hyper rigid polymers and molecular sieve-polymer mixed matrices.

摘要

Despite efforts by the membrane community to develop polymeric materials with improved O{dollar}sb2{dollar}/N{dollar}sb2{dollar} separation performance, limited progress has occurred for almost a decade. Molecular sieving media, which can exhibit gas separation properties superior to polymers, tend to be brittle and difficult to produce for large scale membrane separation processes. Considering this, the hyper rigid polymer structures investigated in this work were designed to mimic aspects of the structure of molecular sieving media such as zeolites and carbon molecular sieves while maintaining the processability associated with polymers. In addition, a fundamental analysis of mixed matrix membrane, incorporating molecular sieving materials within a polymeric matrix, was performed. This analysis indicates that high performance membranes can potentially be achieved with careful materials section and defect elimination.; The permeability, sorption, and diffusion coefficients of He, CO{dollar}sb2{dollar}, O{dollar}sb2{dollar}, N{dollar}sb2{dollar}, and CH{dollar}sb4{dollar} in BBL, a hyper rigid, flat, packable ladder polymer were investigated. Regardless of penetrant size, gas permeation through such a rigid, packable matrix was extremely slow and only moderately selective.; Significantly more attractive gas separation material properties were obtained from a refined approach to hyper rigid polymers that attempted to create a "molecular jack". Such materials were polypyrrolone copolymers formed from a flat, packable monomer and a monomer with a bulky group to disrupt packing. The gas transport properties in the materials changed dramatically as a result of different interchain spacing. Moreover, all of the polypyrrolones studied in this work exhibited performance lying on or above the existing O{dollar}sb2{dollar}/N{dollar}sb2{dollar} upper bound trade-off line between permeability and permselectivity, whereby indicating highly attractive performance relative to most polymers reported to date.; The temperature dependence of He, CO{dollar}sb2{dollar}, O{dollar}sb2{dollar}, N{dollar}sb2{dollar}, and CH{dollar}sb4{dollar} gas transport and sorption in these polypyrrolones was investigated. By probing the polymer matrix with penetrants of different dimensions, insights into the gas separation environment created by the given copolymer composition are gained. In addition, entropic selectivity analysis of these materials indicated that a reasonably open polymer matrix is necessary to achieve enhanced entropic selectivity polymers. Even for the materials possessing low entropic selectivities, high performance gas separation properties are achieved with exceptionally high energetic selectivities.