Abstract
Three polyimides and six inorganic fillers in a form of nanometer-sized particles were studied as thick film solution cast mixed matrix membranes (MMMs) for the transport of CO2, CH4, and H2O. Gas transport properties and electron microscopy images indicate good polymer-filler compatibility for all membranes. The only filler type thatdemonstrated good distribution throughout the membrane thickness at 10 wt.% loading was BaCe0.2Zr0.7Y0.1O3 (BCZY). The influence of this filler on MMM gas transport properties was studied in detail for 6FDA-6FpDA in a filler content range from one to 20 wt.% and for Matrimid® and P84® at 10 wt.% loading. The most promising result was obtained for Matrimid®—10 wt.% BCZY MMM, which showed improvement in CO2 and H2O permeabilities accompanied by increased CO2/CH4 selectivity and high water selective membrane at elevated temperatures without H2O/permanent gas selectivity loss.
Highlights
Mixed matrix membranes (MMMs) [1,2] are considered as a very promising route to overcome limitations of the Robeson upper bound of the permeability/selectivity relationship by combining good mechanical, but rather disappointing gas transport properties of polymers, with excellent diffusion and sorption properties of inorganic porous media having very poor mechanical properties, e.g., flexibility [3].Gas separation membranes have been on the market since 1980 [4] and have proven their reliability [5]
Thermogravimetric analysis experiments (TGA) were performed in order to evaluate the thermal stability of the MMMs and to determine the real amount of particles in the final sample [50]
The parameter used to evaluate the quantity of particles in the membranes is the residual mass (RM )
Summary
Mixed matrix membranes (MMMs) [1,2] are considered as a very promising route to overcome limitations of the Robeson upper bound of the permeability/selectivity relationship by combining good mechanical, but rather disappointing gas transport properties of polymers, with excellent diffusion and sorption properties of inorganic porous media having very poor mechanical properties, e.g., flexibility [3]. New membranes introduced to the market should exhibit significantly better properties, as compared to those already commercially available At this point, the combination of properties of polymers and inorganic substances able to selectively transport gas or vapor molecules becomes very appealing [7]. The requirements for polymers to be used in membranes are: Adequate gas transport properties (balance between permeability and selectivity), processability as a thin film, and high reproducible. This normally results in an increase of the selectivity, due to the increased rigidity, and in a decrease of the permeability This is normally confirmed by an increase on the Tg of the MMMs. Case 3 exhibits a creation of an interphase due to the incompatibility between the particle and the polymer matrix.
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