Gas Separation Properties of Polymeric Membranes Modified by Acetylene/Nitrogen Plasmas

• Main Authors: Cheng-Yao Shih, 施証耀
• Other Authors: Ta-Chin Wei
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/76072088283840121358

碩士 === 中原大學 === 化學工程研究所 === 89 === In this study the plasma-polymerized films from C2H2/N2 mixtures were deposited onto the commercial TPX membranes to enhance the separation of oxygen over nitrogen. The effect of operating parameters on gas separation properties was investigated. It was found that the deposition rate of plasma polymer increases with the plasma power and the flow rate of C2H2, and it decreases with the operating pressure. Regarding to the gas separation properties, the thin plasma polymer grown onto the TPX membrane results in a favorable increase of O2/N2 selectivity without a sharp decrease on gas permeability. The better separation performance occurred in films deposited at higher growth rates, such as pure C2H2 plasma at 60 W, or C2H2/N2 plasma at 90 W. However, the deposition time has to be short otherwise the film would lose its favorable selectivity due to film rupture induced by elevated internal stress. The internal stress in a plasma polymer was found to decrease as the feed ratio of N2 increased. Finally, the surface structure of plasma polymer was characterized, hemispherical structures of broad size distributions was seen on the surface of the plasma polymer deposited in C2H2/N2 plasmas. The polymer deposited from C2H2/N2 plasmas contains more oxygen than nitrogen-containing functional groups. The O2/N2 separation property of TPX membrane modified by C2H2/N2 plasma is mainly determined by the degree of cross-linking in the plasma polymer, rather than the preferential sorption from different functional groups.