Synthesis And Applications Of Small Pore Molecular Sieve Membranes And The Palladium Composite Membranes

As a kind of green energy, hydrogen attracts lots of attention in today’s life. However, hydrogen is a kind of secondary energy, which need prepared through the method of oil thermal-cracking and so on. But these methods also produce CO2, N2 and some carbon by-products. For this reason, the research on hydrogen purification becomes crucial. Zeolite molecular sieve membranes are new types of inorganic membrane materials, which become a hot research topic in the field of gas separation.Generally, zeolites can be classified into small, medium and large pore materials according to pore structure and pore size. Some small pore structure meterals like SAPO-34 (0.38×0.38 nm) and DDR (0.36×0.44 nm) can be used in the separation of small size gase moleculars due to their small pore sizes and the thermal stabilities. In addition, palladium membrane as known shows excellent selectivity in the field of hydrogen separation, which make it be the research focus for a long time. In this work, some new strategies were proposed aiming at the preparation of small pore size molecular sieve membranes and the palladium composite membranes using in the gas separation. Some major contents can be found as follows:(1) Preparation high-quality SAPO-34 molecular membranes on the low-cost macro-porous α-Al2O3 support using the steam-assisted seeding method. This method could increase the bonding force between the seed layer and supports. The small seeds were coating on the large pore support without getting into the depth. The as-synthesized membranes were used in gas separation at room temperature and the ideal separation factors of H2/CO2, H2/N2, H2/CH4, H2/C3H8 and H2/i-C4Hio were 1.813,7.479,14.337,27.445 and 54.226, respectively, with the H2 permeance of 6.724x10"6 mol·m-2s-1Pa-1(2) SAPO-34 zeolite membranes show low selectivity when being used in the field of separation small size gas from small size gases. In this work, a Pd/SAPO-34 composite membrane was prepared to solve the problem mentioned above. The composite membrane was used in gas separation at 573K and the ideal separation factors of H2/CO2, H2/N2 and H2/CH4 were 65,96,182, moreover, the H2 permeance was 8.29×10-7 mol·m-2s-1Pa-1. In addition, the data of separation achieve best when the test temperature was 873K, and the ideal separation factor of H2/CO2, H2/N2 and H2/CH4 were 182,215,377, moreover, the H2 permeance was 3.04×10-6 mol·m-2s-1Pa-1 in the final test.(3) Research on preparing a palladium composite membrane on the other small pore size zeolite membrane such as DDR type zeolite molecular membrane. Shorten the time of normal reaction in case of being conversion during the preparation under a high temperature. The precursor will be prepared during this process, which also has a separation performance. Electroless Plating method used to prepare a Pd/DDR-precursor composite membrane, and the gas separation performance achieve the best when the test temperature was 873K. The ideal separation factor of H2/CO2, H2/N2 and H2/CH4 were 170,185,305, additionally, the H2 permeance was 1.91×10-6 mol·m-s-1Pa-1.