Applications Of Triethylbutylammonium Ionic Liquids On The Membrane Separation Of Acidic Gases

The capture of acidic gases has attracted common attention from industrial and academic community. Membrane separation technology has become a good way of chemical separation process, due to the advantages of simple equipment, easy operation, low energy consumption and green performance. However, the commercially available polymeric membranes cannot achieve both high permeability and selectivity because of the Robeson upper limitation, which hindered the research and application of current gas separation process. It is accepted that ionic liquids (ILs) are environmental because of the unique characteristics such as non volatile, high thermal stability and designable structures. The use of task-specific ionic liquids as novel membrane material is a key factor to overcome this limitation.This paper designed two series of ILs-triethylbutylammonium carboxylates and dicarboxylates, achieving their facilitated transport performance through reversible chemical reactions between ILs and CO2, SO2molecules. The detailed research includes:(1) The synthesis of weakly alkaline triethylbutylammonium carboxylates and the preparation of supported ionic liquid membranes (SILMs) to facilitate transport CO2, testing the influence of IL species, operation pressure and temperature, the water content in operation environment on separation performance.(2) The synthesis of weak acidic triethylbutylammonium dicarboxylates and the preparation of SILMs to facilitate transport SO2, testing the impact factors similar to the CO2separation process. Based on the experimental results, following conclusions have been obtained:(1) The weakly alkaline carboxylates as [N2224][malonate] and [N2224][maleate] can be used as carriers in assistance of water vapor to facilitate transport CO2through reversible chemical reactions, resulting in excellent permeability and selectivity under low CO2partial pressure. The facilitated transport membrane immobilized with [N2224][maleate] displayed CO2permeability above2840barrers and CO2/N2selectivity over250when CO2partial pressure was10KPa at40℃.(2) Operation pressure and temperature have important influence on separation process. The facilitated transport of CO2tends to decrease with the increasing partial pressure, primarily due to the carrier being saturated with CO2. All gas permeability increase with the increasing temperature, but the gas selectivity decrease.(3) The weak acidic half deprotonated dicarboxylates such as [N2224][H-malonate],[N2224][H-maleate] and [N2224][H-glutarate] achieved excellent SO2facilitated transportation. A eight atomic ring is formed in assistance of water vapor to trap SO2and it is reversible by heating and vacuuming. In [N2224][H-malonate] SILM, the SO2permeability reached as high as10918barrers when SO2partial pressure was kept at15KPa. The selectivity of SO2/N2and SO2/CO2gas pairs were above1390and25respectively.(4) Operation pressure and temperature have significant influence on separation process. When the driving force increase, the SO2permeability in three half deprotonated dicarboxylates increase gradually to stabilize, while the SO2permeability in the other ILs show abnormal increasing. All gas permeability increase with the increasing temperature, but the gas selectivity decrease.In this paper, we made a preliminary exploration on the CO2and SO2facilitated transportation by novel triethylbutylammonium carboxylates SILMs. The present study is believed to provide new ideas on the thesis research and engineering application of facilitated transport membrane to separate acidic gases.