The Preparation Of Mixed Matrix Membranes PEBA2533 Loaded With 4A Zeolites And The Study Of The Separation Performance

The gas membrane separating process has drawn much attention, for it has the advantages of low energy consumption and capital cost, and easy operation. Generally, the permeability and selectivity of the membranes changes to the opposite direction. Improving the permeability and selectivity simultaneously is the expection of researcher.In this thesis, with a block copolymer–polyether block copolyamide(PEBA2533) as the organic matrix and 4A zeolites as the inorganic filler particles, a series ofPEBA2533 loaded with 4A zeolites mixed matrix membranes(MMMs) were prepared by physical blending. The effect of the preparation parameters, including the content of 4A zeolites in the membrane and the thickness of the membrane, on the structure and performance of the membranes were investigated. The membranes were characterized by Scanning Electron Microscopy(SEM), Fourier Transform-Infrared Spectroscopy(FT-IR) and Thermo-gravimetric Analysis(TGA) method. The separation performance of the membranes to ethylene/propylene mixture was investigated. The details are as follows:1. The effect of the temperature and pressure on the separation performance. For the pure PEBA2533 membrane and MMMs(3wt% of 4A content), the effects of temperature(20℃ ~-35℃) and pressure(0.2 MPa ~ 0.4 MPa) on its separation performance were investigated. Separation performance of two kinds of membranes as a function of pressure variations showed the similar trend: the separation factor increases with the decrease of pressure, permeability decrease with the decrease of pressure. The variation with temperature is different: pure PEBA2533 membrane separation factor increase with temperature decrease and permeability decrease with temperature decrease; while the permeability of the MMMs decreases to the minimum value at-15℃in the process of temperature decreasing and the permeability increase with further temperature decrease, and reaching the biggest value at-35℃. The separation performance of MMMs is superior to pure PEBA2533 membrane. Under optimum separation conditions:-35℃, 0.2 MPa, its separation factor α propylene/ethylene equals to 5.15, permeability PC2H4 equals to 1829 Barrer, PC3H6 equals to 9410 Barrer.2. The effect of 4A zeolites content on the microstructure and membrane separation performance. The 4A zeolites is completely wrapped and dispersed better in the organic matrix when the 4A zeolites content(0wt% ~ 15wt%) is low. Some4 A zeolites are exposed on the surface of the MMMs and poorly coated by the organic matrix when the 4A zeolites content(25wt% ~ 35wt%) is high. The MMMs with 3wt% amount of 4A zeolites shows the highest separation performance at-35℃, 0.2 MPa among the membranes as synthesized.3. The effect of membrane thickness on the microstructure and membrane separation performance. For MMMs with different thickness, with 15wt% and 25wt% of 4A zeolites, increasing the thickness of the MMMs made the organic matrix coated the 4Azeolites better. The separation performance of MMMs with 25wt% of 4A zeolites wasn’t improved obviously when the thickness change from 110 μm to 190 μm. The membrane with the thickness of 110 μm showed the best separation performance at-35℃, 0.2 MPa among the membranes: separation factor α propylene/ethylene equals to 6.05, permeance JC2H4 equals to 9 GPU, JC3H6 equals to 54 GPU.4. The effect of the composition of the gas mixture on the separation performance. The membrane with 25wt% zeolites and 110 μm thickness was used in the separating process. At-35℃ and 0.2 MPa, the separation factor increased from 1.62 to 19.3, and permeability of propylene increased from 1960 Barrer to 12043 Barrer, when the propylene concentration(mole fraction) in the mixture increased from 10% to 90%. The separation factor and permeability increased simultaneously with the increase of the concentration of propylene.