sapo34分子筛膜的制备及气体分离性能研究-preparation and gas separation performance of sapo 34 molecular sieve membrane.docx

ABSTRACTThe separation and removal of CO2 using membrane technology is one of the most important subjects worldwide. The separation of CO2 from CH4 is critical for methane transportation and storage because the existence of CO2 reduces the energy content and causes the corrosion of equipment and pipelines in the presence of water which needs to be prevented. The most widely used technologies for CO2 removal include the processes of absorption and polymeric membrane separation. But the absorption equipment is complex and not cost-effective. Besides, the high partial pressure of CO2 can plasticize polymeric membranes and decrease their separation performances. Compared with the traditional polymeric membranes, molecular sieve membranes exhibit a favorable application potential in purification of CH4 from CO2/CH4 gas mixture due to their corrosion-resistant abilities with very good mechanical and thermal stabilities, especially at high pressure of CO2.The membranes constructed with small, medium and large pore-sized molecularsieves can be used to separate CO2 from gas mixtures. However, the membranes of medium and large pore-sized molecular sieves are not efficient for separation of gas mixtures with small molecules of similar kinetic diameters such as CO2 and CH4, the kinetic diameter of which are 0.33 and 0.38 nm respectively. In contrast, small pore-sized molecular sieve membranes such as zeolite T(0.36×0.51 nm), DDR (0.36×0.44 nm), and SAPO-34 (0.38 nm) have shown high CO2/CH4 selectivities due to the combination of molecular sieving and competitive adsorption because pore sizes are similar in size to CH4 (0.38 nm) but larger than CO2 (0.33 nm).In the present work, SAPO-34 molecular sieve membranes were fabricated with 10μm layers on porous α-Al2O3 substrates by in-situ hydrothermal synthesis. The effects of pH and water content of the starting reaction solution, and crystallization temperature on SAPO-34 membranes were investigated. As the substrate surface was un