Study On Properties Of Gas Separation Of Composite Carbon Membrane Prepared By Interfacial Polymerization

Carbon molecular sieve membrane is a novel carbon-based membrane material with high gas separation performance, heat resistance and corrosion resistance etc. It has a well application prospect in the gas separation, such as oxygen-rich gas, hydrogen recovery, natural gas, acid gas removal etc. However, the weak mechanical strength limits the application of carbon membrane. People prepare the supported carbon membrane to improve the mechanical strength of the carbon membrane, but the cracks, pinholes and other surface defects which appear in the process of preparation. In this paper, the interfacial polymerization is used to modify the defects, which may exist in the surface of spiral-wound carbon membrane, so as to improve the selectivity of carbon membranes. Composite membranes were prepared by interfacial polymerization of trimesoylchloride (TMC) with m-phenylenediamine (MPD) or bisphenol A (BPA). The chemical structure, micro-structure and gas separation properties of the composite membranes were characterized by FTIR, TG, SEM and gas permeation tests. Preparation conditions impacting gas separation performance of the composite membrane were systematic characterized. The results were summarized as follows:(1) The polyamide film was prepared by interfacial polymerization of MPD with TMC. As the polymerization time increasing, the gas permeation flux of composite membrane rapidly decreased to stabilize and the gas separation factor increased to stabilize. By increasing the monomer concentration, the permeation flux first decreased and then slightly increased. The composite membrane gas permeation flux first decreased and then stabilized with increasing heat treatment time and selectivity increased and then stabilized. With pH increase, the permeation flux first decreased and then increased, on the contrary, the selectivity increased. Increasing the reaction times increased the selectivity of the composite membrane. The optimum preparation conditions were concluded:polymerization reaction time is5-10min; MPD and TMC concentrations are8%(wt.%) and0.4%(wt.%); pH value is11; the reaction times are twice or three times; the heat treatment time is10-20min. The permeation flux of O2and N2of the composite carbon membrane prepared under the optimum conditions are29.06GPU and15.41GPU separately. The O2/N2separation factor is1.89. (2) The polyester thin film was prepared by interfacial polymerization of BPA with TMC. As the polymerization time increasing, the gas permeation flux of composite membrane rapidly decreased to stabilize the gas separation factor increased to stabilize. By increasing monomer concentration, the permeation flux first decreased and then slightly increases. The composite membrane gas permeation flux first decreased and then stabilized with increasing heat treatment time and selectivity increased and then stabilized. Increasing the reaction times increased the selectivity of the composite membrane. The gas permeation flux of composite membrane prepared using toluene as the organic phase solvents is the better.The optimum preparation conditions were concluded:the reaction time is3-5min; BPA and TMC concentrations are3%(wt.%) and0.68%(wt.%); SDS concentration is0.03-0.10%(wt.%); the reaction times is twice; the heat treatment time is10-15min. The permeation flux of O2and N2of the composite carbon membrane prepared under the optimum conditions are11.03GPU and3.45GPU separately, the O2/N2separation factor up to3.12.