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Thermally Induced Mesophase Development in Ethanesilica Films via Macromolecular Templating Approach
Cho, Whirang,Char, Kook-Heon,Kwon, Su-Yong The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.9
Mesoporous ethanesilica thin film was prepared using PEO-PLGA-PEO triblock copolymers as structure-directing agents and (1,2-bis(triethoxysilyl) ethane BTESE; bridged organosilicates) as inorganic precursors via one-step sol-gel condensation of ethanesilica precursors. The mesostructure of ethanesilica films is critically dependent on the processing experimental parameters after the hydrolyzed silica sol mixture was spin-cast. This study examined the effects of the block copolymer template/organosilica precursor ratio in the casting solution and aging period before calcination of the mesostructure. It was further demonstrated that mesoscopic ordering of organosilicate thin films is induced by the rearrangement of block copolymer template/organosilica hybrid during thermal decomposition of the PEO-PLGA-PEO triblock copolymer. The mesoporous structure and morphology were characterized by SAXS, TEM and solid-state NMR measurement.
코발트 이온교환 mordenite 촉매에 의한 O - Xylene 이성질화반응
김영걸,차국헌 한국화학공학회 1983 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.21 No.6
Cobalt 이온交換된 mordenite를 使用하여 O-Xylene의 異性質化反應을 壓力, 觸媒의 前處理過程 및 反應 雰圍氣를 바꾸어가며 硏究하였다. 常壓때와 달리 高壓에서는 水素 雰圍氣下에서 觸媒의 非活性化가 안 잃어 났으며 異性質化 選擇度가 낮아졌다. 水蒸氣處理한 觸媒는 乾燥空氣處理한 觸媒에 比하여 活性은 높으나 選擇度는 낮아졌음을 보았다. 反應雰圍氣는 coke 形成에 影響을 미쳤다. 壓力에 關係없이 窒素와 헬륨 雰圍氣에서는 水素雰圍氣에 比하여 바른 非活性化가 일어났으며 1, 3, 5-TMB의 急激한 減少가 일어나며 그에 따라 1, 2, 3-TMB도 줄어들었다. The isomerization of o-xylene on cobalt-exchanged catalyst was studied by varying the pressure, pretreatment conditions and the reaction atmosphere. Compared with the low-pressure(1 atm) operation, high pressure operation (180.7 psia) gave lower isomerization selectivity, but no deactivation. Steamtreatment of the catalyst resulted in higher activity and lower selectivity than the dry air treatment. Reaction atmosphere had an effect on coke formation. Regardless of pressure, nitrogen and helium atmosphere speeded up the deactivation process, and resulted in rapid decrease in 1, 3, 5-TMB formation and also decreased the amount of 1, 2, 3-TMB formed.
Kang, Sang-Wook,Char, Kook-Heon,Kim, Jong-Hak,Kang, Yong-Soo The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.2
The reduction behavior of silver ions to silver nanoparticles is an important topic in polymer/silver salt complex membranes to facilitate olefin transport, as this has a significant effect on the long-term performance stability of the membrane. In this study, the effects ofthe solvent type on the formation of silver nanoparticles, as well as the long-term membrane performance of a solid polymer/silver salt complex membrane were investigated. These effects were assessed for solid complexes of poly(N-vinyl pyrrolidone) $(PVP)/AgBF_4$, using either an ionic liquid (IL), acetonitrile (ACN) or water as the solvent for the membrane preparation. The membrane performance test showed that long-term stability was strongly dependent on the solvent type, which increased in the following order: IL > ACN >> water. The formation of silver nanoparticles was more favorable with the solvent type in the reverse order, as supported by UV-visible spectroscopy. The poor stability of the $(PVP)/AgBF_4$ membrane when water was used as the solvent might have been due to the small amount of water present in the silver-polymer complex membranes actively participating in the reduction reaction of the silver ions into silver nanoparticles. Conversely, the higher stability of the $(PVP)/AgBF_4$, membrane when an IL was used as the solvent was attributable to the cooperative coordination of silver ions with the IL, as well as with the polymer matrix, as confirmed by FTIR spectroscopy.