Polarized Silver Nanoparticles by Ionic Liquid and Its Application to Facilitated Olefin Transport Membranes
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1006-R07-12
Polarized Silver Nanoparticles by Ionic Liquid and its Application to Facilitated Olefin Transport Membranes Sang Wook Kang1, Kookheon Char1, and Yong Soo Kang2 1 School of Chemical & Biological Engineering, Seoul National University, Seoul, 151-744, Korea, Republic of 2 Department of Chemical Engineering, Hanyang University, Seoul, 133-791, Korea, Republic of
ABSTRACT The BMIM+NO3-/Ag metal nanocomposite membranes were utilized for separation of propylene/propane mixtures. The selectivity of propylene/propane and the mixed gas permeance increased to 10 and 1.3 GPU, respectively. It is anticipated that the interactions between NO3- of BMIM+NO3- and the surface of silver nanoparticles causes the Ag surface to be partially positively charged, resulting in the reversible complexation with propylene and consequently facilitated propylene transport. The surface positive charge was confirmed from the increase in the binding energy of the d5/2 orbital of the silver nanoparticles by x-ray photoelectron spectroscopy. It increased from 368.26 for the neat silver nanoparticles to 368.47 eV for BMIM+NO3-/Ag metal composite. The positively charged surface of silver nanoparticles can be utilized as a new durable olefin carrier for facilitated transport. INTRODUCTION Silver nanoparticles can be utilized as electronic conductor, catalyst, surface enhanced Raman effect and anti-bacterial agent.1-5 Recently we first reported the possibility of silver nanoparticles with partial positive charges on the surface a novel durable olefin carrier.6 In particular, electron acceptor such as p-benzoquinone induced partial positive charges on the surface of silver nanoparticles, resulting in chemically more active to olefin molecules and consequently amplified interactions with propylene. 6 Here ionic liquid (IL) instead of pbenzoquinone is utilized to induce the partial positive charge on the surface of silver nanoparticles for facilitated olefin transport. ILs have many advantages such as high polarity, ionic conductivity, thermal stability and low vapor pressure.7,8 Thus, the highly charged nature of ILs is expected to polarize the surface of silver nanoparticles. In this study, the ionic liquid 1-butyl-3-methylimidazolium nitrate (BMIM+NO3-) was employed to polarize the surface properties of silver nanoparticles. BMIM+NO3-/Ag metal composite membranes were prepared for the separation of olefin/paraffin mixtures and the polarity of silver metal induced by BMIM+NO3- was investigated by XPS. EXPERIMENT Materials: Silver nanopowder (70 nm, 99.5%) was purchased from Aldrich Chemical Co. The ionic liquid 1-butyl-3-methylimidazolium nitrate (BMIM+NO3-) was purchased from C-TRI Co. All the chemicals were used as received. Separation performance: The ILs/Ag composite membranes were prepared by dispersing Ag nanopowder in ILs. The weight of the IL was fixed at 1g and the amount of the Ag nanopowder
was varied. For the fabrication of the separation membrane, the silver nanoparticle-dispersed solution in the IL was coated onto polyester
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