Interactions between the Ionic Liquid and the ZrO2 Support in Supported Ionic Liquid Membranes for CO2 Separation

Cinthia Sánchez-Fuentes,Eduardo Terrés,Mirella Gutiérrez-Arzaluz,Violeta Mugica-Álvarez,Sibele Pergher,Miguel Torres-Rodríguez

doi:10.3390/technologies4040032

Abstract

This work reports the interaction study of two supported ionic liquid membranes (SILMs) based on 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), which were impregnated into porous zirconia supports with 20 nm average pore diameters. The interaction of ionic liquid-support observed from diffuse reflectance (DR), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS) is reported. The IR spectrum in the 600 to 4000 cm−1 range showed a specific interaction of the ionic liquid with the support. The N2 and CO2 permeances in the SILMs with [C4mim][BF4] were 8.7 × 10−8 mol·s−1·m−2·Pa−1 and 9.6 × 10−7 mol·s−1·m−2·Pa−1, respectively. The separation factor through the ionic liquid in the membrane as a function of temperature showed that the SILMs studied here can be used for CO2 separation at low temperatures.

Highlights

Some properties of ionic liquids (ILs), such as negligible vapour pressures and high viscosities, make them adequate candidates for the liquid phase in supported ionic liquid membranes (SILMs).a slow outward liquid displacement happens from a micro or mesoporous support under pressure, which reduces the loss of ILs from the supports [1]
In all of the permeance tests, the SILMs were tested at increasing and decreasing pressures repeatedly to verify that the ionic layer remained intact within the pore network of the support, until the pressure reached 3 bar; the results showed that the SILMs remained stable after the permeability tests
The results clearly indicate that the permeance decreased with the increase of CO2 pressure, at 2 bar, the permeance slowly decreased with further pressure increase

Summary

Introduction

Some properties of ionic liquids (ILs), such as negligible vapour pressures and high viscosities, make them adequate candidates for the liquid phase in supported ionic liquid membranes (SILMs).a slow outward liquid displacement happens from a micro or mesoporous support under pressure, which reduces the loss of ILs from the supports [1]. Some properties of ionic liquids (ILs), such as negligible vapour pressures and high viscosities, make them adequate candidates for the liquid phase in supported ionic liquid membranes (SILMs). The current materials that can support ionic liquids for gas separation in post-combustion processes, in which the goal is to separate CO2 from CO2 /N2 mixtures, can be categorized into inorganic ceramic and organic polymeric materials. The CO2 separation membrane can be either a single or composite structure made of, for example, silica, zeolite, zirconia, titania, or alumina [3,4]. Zirconia is an especially attractive material for ceramic membranes. A zirconia-based membrane exhibits excellent features, including elevated chemical stability, superior permeability, and greater flux during separation owing to its specific surface characteristics and excellent thermal resistance [5]

Objectives

Discussion

Conclusion