| Composite hollow fiber membrane separation is widely applied to separating VOCs from air. It has many advantages such as few investment, less energy consumption, simple operation and control,no pollution, outstanding technical advantages and promising application prospects.Here, some composite membranes were made, n-heptane recovery process from the mixture of N2 and n-heptane or air and n-heptane was studied. The minisize hollow fiber membrane subassembly was prepared and the experiment equipment for determining the performance in separating VOCs from air was assembled.Firstly, the silicone rubber / polysulfone hollow fiber composite membranes were prepared by dip-coating method, by choosing 4 hollow fibers as base membrane and 4 silicone rubbers as coat. The effects of some factors, including concentration of the silicone rubber, catalyst and cross-linker, on gas separation performance of composite membranes also were discussed. The membrane of silicon oil/PS-I has the best performance of them.Secondly, the heating treatment on the base membrane was applied to enhance the separation performance of composite membrane. The effects of some factors, including the temperature of heat treatment and the time of heat treatment, were discussed,in order to find the best heat treatment condition. The structure of silicone rubber, hollow base membranes and hollow fiber composite membranes were analyzed by SEM method. The functional group of the membrane was analyzed by IR method.Finally, the composite membrane RTV-107/PVDF whose base membrane was heated on best heat treatment condition was in study. The influences of feed flow rate, feed pressure, and the concentration of n-heptane in permeate gas on gas permeability and selectivity of hollow fiber composite membranes were studied and the reasonable operating conditions were decided. On the same condition, the n-heptane/ N2 system and the n-heptane/gas system have the similar trend in the change of separation performance.
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