| CO2 is the main greenhouse gases and valuable carbon resources, so capture and separation of CO2 become an important research subject at present. Compared with the traditional absorption and adsorption separation technology, membrane separation of CO2 has many advantages, such as low energy consumption, simple process, less investment, easy operation and environment friendly etc.. Membrane is the core of the membrane separation technology. Because of the limitation of solution-diffusion mechanism, traditional organic gas separation membrane is difficult to break through "Robeson up limit", and the membrane with high CO2 permeation rate and selectivity is unable to be prepared. In order to fundamentally get rid of "Robeson up limit", we have to use facilitated transport membrane that does not rely on solution-diffusion mechanism. Fixed carrier membranes attracts widespread attention because of both high permeation rate and selectivity and stable carrier, etc. Membrane preparation conditions have a great influence on the separation performance of membrane, but the optimization of the traditional membrane preparation conditions is to use single factor optimization method, so it does not take into account the interaction relationship between the parameters, and which needs many test times. In this thesis, on the carrier of amino, the amino of chitosan (CS) was selected as membrane material, then CS/PVDF composite membrane separation of CO2/N2 was prepared, and the response surface method (RSM) was used to optimize the preparation conditions of the composite membrane.First, CS molecular weight, concentration of CS, solvent evaporation temperature, solvent evaporation relative humidity, and blending triethanolamine additive (TEA) concentration of 5 membrane preparation conditions was selected as the influence factors, TEA concentration of them represents the TEA mass fraction in the total quality of the CS and TEA (the same below). CO2 permeate rate, CO2/N2 selectivity and separation performance of membrane were regarded as response values, and Box-Behnken Design was used to design 46 sets of the different experiment conditions in Design-Expert 7.1.3 software.Second, ultrafiltration membrane of PVDF was prepared as porous support by L-S method, and hydrophilic modification was carried out at 0.5 wt.% of PVA water solution. Then CS/PVDF composite membranes were prepared by the roller coating method under the different conditions, and separation performances of membranes were obtained using the membrane test device. The experimental results represent good correlation by analysis of variance and response surface analysis, and quadratic model equations for the membrane of CO2 permeate rate, CO2/N2 selectivity and separation performance were obtained.Finally, the membrane preparation conditions were optimized and validated by experiments. Considering respectively the membrane CO2 permeate rate and CO2/N2 selectivity or singlely considering integrated separation performance of membrane, we got the same optimal membrane preparation conditions:CS molecular weight is 300000, CS concentration is 1.4 wt.%, solvent evaporation temperature 30 ?, solvent evaporation relative humidity is 20%, the concentration of the TEA is 15 wt.%. Under the optimal conditions, CO2 permeation rate, CO2/N2 selectivity and separation performance of prediction of the CS/PVDF composite membrane reached 59 GPU,54.3 and 75.5, respectively. And the test experiments were carried out under the optimal conditions of membrane preparation, average relative error between predicted values and the experiment for the permeability of membrane CO2 permeation rate, CO2/N2 selectivity and separation performance were 10.01%,5.46% and 5.82%, respectively. |
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