이온성액체에 의한 산화구리 나노입자의 표면 양극화 유도현상 및 올레핀/파라핀 촉진수송 복합분리막 응용

Abstract

Olefin/paraffin mixtures have been separated by the cryogenic distillation process requiring intensive-energy and large space. Therefore, novel energy-saving process has been demanding. The membrane process has been considered as a promising alternative as an energy- and space-saving process. In particular, solid membranes using the concept of facilitated transport can be a powerful candidate to get enhanced selectivity and permeability simultaneously. In facilitated transport membrane, carrier mediate transport can occur in addition to a normal Fickian transport because of the reversible reaction of the carrier with a specific solute, resulting in remarkably improved separation efficiency.

It is well known that silver ions and metallic silver nanoparticles can interact reversibly with olefin molecules making silver-olefin complexes, but not with paraffin, and act, thus, as the carrier for facilitated olefin transport membrane. Especially, the positively charged surface of metallic silver nanoparticles, induced by electron acceptor such as p-benzoquinone and ionic liquid, can act as a robust olefin carrier making complexation with olefin molecules reversibly. In this thesis, copper oxide nanoparticles were oxplored as an novel olefin carrier along with ionic liquids.

First, a new application of ionic liquid as an olefin carrier for facilitated transport without nanoparticles was investigated. It was found that when ionic liquid of 1-methl-3-oxtylimidazolium (MOM+NO3-) was exposed to propylene/propane (50/50 v/v) gas mixture for ten minutes, mixed gas selectivity gradually increased to 2.5. The selectivity was associated with the interactions between cations in MOIM+NO3- and propylene gas as investigated using FT-IR spectroscopy. The interactions may be possible because of the formation of free ions of ionic liquids upon exposure of propylene, evaluated by deconvoluted FT-IR spectra showing the blue-shift of the N-O stretching band. Finally, using ab initio calculation, we suggest the possible theoretical interactions between cation of ionic liquids and olefin molecules were suggested.

Secondly, copper oxide nanoparticles were applied for a novel carrier for facilitated olefin transport membrane, by inducing positive charge on their surface with ionic liquids. Copper oxide nanoparticles are attractive due to their competitive price and chemical stability at ambient conditions. They were easily made by solvothermal method with narrow size distribution. The formation of copper oxide nanoparticles was confirmed with transmission electron microscope (TEM), UV-vis spectroscopy and X-ray diffraction measurement (XRD). Then, ionic liquids were as an electron acceptor to induce surface positive charge on copper oxide nanoparticles. The formation of partially positive surface charge of copper nanoparticles was observed by the increase of the binding energy with X-ray photoelectron spectroscopy (XPS). The membrane containing copper oxide nanoparticles activated ly the ionic liquid showed improved separation performance to a large extent: the mixed-gas selectivity for propylene/propane mixture was 5 and permeance was 5.5 GPU.

In conclusion, it was found that the ionic liquids acted as a novel olefin carrier for facilitated transport, resulting in the selectivity of 2.5. The separation performance was further improved to 5.5 when the copper oxide nanoparticles were introduced into the ionic liquids. The improved separation performance was mostly due to the surface positive charge formation by the ionic liquid.