Separation of biohydrogen by supported ionic liquid membranes

This work studied the use of room temperature ionic liquids (RTILs) based on the 1-n-alkyl-3-methylimidazolium cation, in supported liquid membranes (SLMs), in order to use them as membrane materials for separation and enrichment of hydrogen from a gaseous mixture containing H2, CO2, and N2. Different RTILs, with different chain length of alkyl substituents on the imidazolium cation and different anions, were incorporated in a PVDF hydrophobic membrane in order to study its effect on the permeability and on the selectivity towards the gases present in the fermentation process. Experiments were conducted in a constant pressure system and temperature (30°C), and pure gas permeability/selectivity data were reported. Supported ionic liquid membranes (SILMs) have been found to be stable at the pressure studied. The highest permeability value (30.70 × 10−11 m2/s) was obtained for the PVDF membrane immobilized with the RTIL [OMIM][PF6]. The high slectivity values towards CO2, between 22 (for [OMIM][PF6]) and 35 (for [BMIM][BF4]), obtained indicates that these SILMs could be used for this process.