Study On Preparation And CO₂ Separation Performances Of Large Size PVAm/PS Composite Membranes

Facilitated transport membranes with fixed carriers for carbon dioxide separation show good stability, high gas permeance and high selectivity. How to prepare large size membrane with acceptable performance is a key fator for its industrialization. In this work, a sealed cabin for preparing large size membrane was made and the preparing process of large size PVAm/PS composite membrane, which is a fixed carrier membrane developed by our research group, was investigated. Temperature and relative humidity of the sealed cabin with internal size of 2400mm×1400mm×2000mm could be regulated in the range of 20⁶0℃and 30⁶0% respectively.Several preparing conditions, including immersing time of substrates in ehylenediamine(EDA) solution, the thickness of the separation layer and the temperature and humidity for evaporating solvent were investigated intensively. The membrane performance was measured by using CO₂/N₂ (20vol% CO₂ and 80vol% N₂). Firstly, the PS substrates were immersed in the 5vol% EDA solution from 1 to 10 hours respectively. The membrane prepared from the PS substrate immersed 10 hours displayed the highest CO₂ permeance and CO₂/N₂ selectivity. Secondly, the performance of the membranes with wet coating thickness of 200μm and 300μm was studied. The results presented that decreasing the wet coating thickness would increase gas permeance and silghtly decrease selectivity. Finally, the effect of temperature and relative humidity for solvent evaporation was tested at 30 oC and 30%, 40% and 60% relative humidity. The results showed that the optimal evaporating condition was 40% relative humidity. Furthermore, evaporation experiment was carried out at 40% humidity and three different temperature of 20, 30 and 40oC。The results presented that the membrane dried in 20℃showed the highest CO₂/N₂ selectivity and the membrane dried in 30℃showed the highest CO₂ permeance.