Effect of Ionic Liquids on Dissociation of Copper Flake into Copper Nanoparticles and Its Application to Facilitated Olefin Transport 이온성 액체를 이용한 양전하가 유도된 구리나노입자의 제조와 올레핀 촉진수송막 응용

Abstract

Abstract

Han, Kook In Department of Chemical Engineering Graduate School Hanyang University

The facilitated transport concept has been applied for separation of olefin/paraffin mixtures such as propylene/propane and ethylene/ethane mixtures. Facilitated transport is observed when carrier-mediated transport and normal Fickian transport occur together. The carrier is defined as any chemical compound which reacts with a specific solute reversibly. Facilitated transport membranes have been attracted because it can be a powerful device to improve both selectivity and permeability simultaneously. Silver ions and metallic nanoparticles have been successfully used as olefin carriers for separation of olefin/paraffin mixtures. In particular, the positively charged surface of metallic silver nanoparticles, which was induced by electron acceptor such as p-benzoquinone and ionic liquids, became active in complexing with olefin molecule reversibly. In chapter 1, the importance of the olefin/paraffin mixture separation and the advantages of membrane separation process were introduced. Previous studies on solid state facilitated transport membranes utilizing silver-polymer electrolytes were reviewed, and problems for practical applications were also issued. Especially, requirements of small-sized and highly polarized particles for performance improvement were reviewed. In chapter 2, Effect of ionic liquids on dissociation of copper flakes into copper nanoparticles and on facilitated olefin transport was investigated. Three different ionic liquids of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM+BF4− ), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6− ) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM+BF4− ) were employed for facile synthesis of copper nanoparticles and for inducing the positive charge density of the copper nanoparticles for facilitated olefin transport. The positively charged surface was generated by dissociation of the ionic liquids into free anions as evidenced by FT-Raman spectroscopy. The separation performance of the ionic liquids/Cu metal composite membranes for olefin/paraffin mixtures was in the following order: EMIM+BF4− /Cu ?q BMIM+PF6− /Cu ?q BMIM+BF4− /Cu. Surprisingly, XPS spectra for the binding energy of the copper atoms in the ionic liquids/Cu metal composite were consistent with the trend for the separation performance. The size distribution of the synthesized copper nanoparticles was evaluated by TEM images and UV-visible spectra. Consequently, it was concluded that facilitated olefin transport was consistent with the trend of increasing binding energy of copper atoms. In chapter 3, a new application of copper oxide nanorods as a novel carrier is used for facilitated olefin transport. The copper oxide nanorods is synthesized by hydrothermal method and had the shape of uniformal. The membrans using copper oxide nanorods polarized by 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6− ) showed high separation performance for propylene/propane, resulting from the increase of electron density on the surface of the nanorods, as confirmed by FT-IR and XPS. Also, BMIM+PF6− acted as both a stabilizer and an electron acceptor. In conclusion, copper nanoparticles and copper oxide nanorods activated by various ionic liquids were utilized as an olefin carrier for facilitated transport to separate olefin/paraffin mixtures, resulting in the high performance and long-term separation stability. Therefore, in this paper, fabrication and applications of copper nanoparticles and copper oxide nanorods to separate olefin/paraffin mixtures and also utilization of ionic liquids for fabricating facilitated olefin transport membranes are investigated.

Keywords: copper nanoparticles, ionic liquids, membrane, facilitated transport