Nozomu Tanihara

Gas Permeation Properties and Characterization of Asymmetric Carbon Membranes Prepared by Pyrolyzing Asymmetric Polyimide Hollow Fiber Membrane

Abstract Carbon membranes were continuously prepared by pyrolyzing an asymmetric polyimide hollow fiber membrane at temperatures ranging from 600 to 1000°C under nitrogen for 3.6 min. The asymmetric polyimide hollow fiber membrane was treated under atmospheric air at 400°C before pyrolysis. By scanning electron microscopy, the carbon membranes were observed to have an asymmetric structure of which a skin layer consisted of nodule aggregates. The asymmetric carbon membranes displayed high performance of gas permeability and selectivity. For example, the membranes prepared by pyrolyzing at over 700°C had permeation rates of hydrogen ranging from 10 −4 to 10 −3 cm 3 (STP)/(cm 2 s cmHg) and ratios of the permeation rate of hydrogen to that of methane ranging from 100 to 630 at a feed gas composition of 50% hydrogen in methane and at 80°C.

Permeation properties to hydrocarbons, perfluorocarbons and chlorofluorocarbons of cross-linked membranes of polymethacrylates with poly(ethylene oxide) and perfluorononyl moieties

Abstract Two kinds of cross-linked polymer membranes were prepared by photo polymerization. One of them (PEO membrane) is a co-polymer of methoxy-terminated poly(ethylene glycol) methacrylate (MEMA) and poly(ethylene glycol) dimethacrylate (EDMA) in feed ratio of 70/30 in wt%. The other (PF/PEO membrane) is a co-polymer of 1H,1H,9H-hexadecafluorononyl methacrylate and EDMA in feed ratio of 70/30 in wt%. The block lengths of poly(ethylene oxide) (PEO) are 9 and 14 for MEMA and EDMA, respectively. Permeation properties of inorganic gases, hydrocarbons, perfluorocarbons and chlorofluorocarbons (CFCs) were investigated for these membranes compared with a silicone rubber (SR) membrane. The PF/PEO membrane is inferior to the SR membrane as for CFCs/N 2 separation because the former has lower permeabilities. The PEO membrane has good performance for separation of hydrocarbons and CFCs from N 2 or perfluorocarbons.

Microporous carbon membranes

This article surveys the production and permeation of carbon membranes in the field of gas separation. Carbon membranes, which are prepared under optimized conditions, show appreciable selectivities for gas mixtures such as H2/N2, CO2/N2 and O2/N2. Separation between organic and inorganic gases, as well as alkane and alkene, is also possible using the carbon membranes. Permeances may be decreased by exposing the membranes to an oxidative or humidified atmosphere at temperatures below 100°C, but can be recovered by heat-treating in an inert atmosphere.