Development and gas permeation study of flat asymmetric polyphenylene oxide membranes.

Abstract

Natural gas is a mixture of hydrocarbon gases and impurities. Processing is required to recover valuable hydrocarbon liquids, remove water vapor, and increase the heating value of the gas before it can be sold to consumers. In addition, the removal of acid gases such as hydrogen sulfide and carbon dioxide is necessary to prevent hydrate formation and corrosion. When compared to other gas separation processes such as cryogenics, adsorption and absorption, membrane separation for gases must compete primarily on the basis of overall economics and convenience. The use of membrane separation for natural gas processing would reduce the size and weight of the processing units and should require less maintenance and operator supervision, at a lower capital cost. For these reasons, membrane processing systems are particularly well suited for remote sites such as off-shore platforms. Asymmetric gas separation membranes were prepared from polyphenylene oxide (PPO) and modified PPO and tested for CO$\sb2$/CH$\sb4$ separation. Using a fractional factorial design, a study of membrane casting conditions was completed in order to optimize the flux and the selectivity of the membrane. A membrane with a CO$\sb2$/CH$\sb4$ pure gas permeation rate ratio of 119 and a CO$\sb2$ permeation rate of 6.8 $\times\ 10\sp{-9}$ moles/(m$\sp2$ s Pa) was obtained.