Enhancement of CO2/CH4 permselectivity via thermal rearrangement of mixed matrix membranes made from an o-hydroxy polyamide with an optimal load of a porous polymer network

Abstract

Mixed matrix membranes, MMMs, consisting of variable loads of a porous polymer network, PPN, within an o-hydroxipolyamide, HPA (6FCl-APAF, made from the reaction between 2,2-bis[4-chlorocarbonylphenyl)hexafluoropropane, 6FCl, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, APAF), have been thermally treated to induce the rearrangement of HPA to a polybenzoxazole (β-TR-PBO). HPA is 6FCl-APAF was loaded with a PPN synthetized, by us, by combining triptycene (TRP) and trifluoroacetophenone (TFAP). Mechanical, thermal and morphological properties of the membranes have been determined.

CO2/CH4 selectivity of MMMs decreased slightly both when the PPN load was augmented and when thermal rearrangement took place. The changes in selectivity can be attributed mostly to solubility effects for β-TR-MMMs and to diffusive effects for the MMM from neat HPA. CO2 and CH4 permeabilities increased to the 2008 Robesońs upper bond for an optimal 30% PPN load both before and after thermal rearrangement. These relatively good permselectivities are explained in terms of compaction, rigidity, fractional free volumes and filling-matrix interactions.