Membranas de PEBAX® com líquidos iônicos para a separação CO2/CH4

Abstract

The technology of gas separation through polymeric membrane has been used to separate carbon dioxide (CO2) from light gases. Thermoplastic elastomers commercially available as poly(ether-block-amide) under the trade name PEBAX®, which possess flexible polyether segments and rigid polyamide segments, are known to be promising materials for CO2 separation through membranes. One strategy to achieve higher permeability and selectivity is the addition of components that enhance both CO2 sorption and diffusion. Ionic liquids (ILs) are salts that exist in a liquid state at room temperature and, when incorporated into polymeric membranes, can increase species permeability through specific and selective interactions with the target gas, as well as alter the physical properties of the membranes. The objective of this work is the preparation, characterization, and permeation in membranes of PEBAX® 1657 and PEBAX® 2533 with protic ILs that exhibit good sorption selectivity for CO2/CH4 separation ([m-2HEA][Ac] and [m-2HEA][Pr]), aiming to evaluate the influence of IL type and content on the properties and performance of the material for CO2 separation. The pure polymer membranes and those with ILs were synthesized and characterized regarding morphology, thermal resistance, mechanical resistance, and gas permeation performance. It was observed that the addition of ILs to the polymeric matrices did not significantly influence the morphology of the films. For films formed from PEBAX® 1657, ILs significantly influenced mechanical resistance, reducing film rigidity by 56 to 83 % compared to pure film. Thermal resistance was also affected by the presence of ILs, as the initial degradation temperature decreased by 11 to 24 °C compared to pure film. For PEBAX® 2533, only thermal resistance was observed to be influenced, however, since ILs did not affect the organization of the polymer chains, the decrease in initial degradation temperature is solely due to the increase in thermal conductivity of the material due to the presence of IL in its structure. The effect of IL type and content, as well as feed pressure, on membrane performance in CO2 and CH4 separation was also studied. For PEBAX® 2533 membranes, the addition of IL did not show significant effects on the permeation performance of both gases, while for PEBAX® 1657, the most promising result indicated that, at 2 bar and 35 °C, the introduction of 40 % [m-2HEA][Pr] to this polymer increased the permeability of CO2/CH4 separation by approximately 230 % compared to the pure polymer membrane.