Synthesis Of SAPO-34-based Zeolite Composite Membranes And Application In Gas Separation

The SAPO-34 molecular sieve membrane and carbon membrane,as a new type of gas separation membrane material,have developed nano-scale microporous structures capable of sieving gas molecular size,and also have high chemical stability and thermal stability.Therefore,based on the SAPO-34 zeolite molecular sieve,it is of great significance to prepare SAPO-34 molecular sieve membrane and SAPO-34/carbon composite membrane with excellent structure and gas separation performance for gas separation.Cube-shaped SAPO-34 molecular sieves were prepared using a traditional hydrothermal synthesis method.With tetraethylammonium hydroxide as the template,the initial molar ratio of the gel was:Al₂O₃:P₂O₅:SiO₂:TEAOH:H₂O=1:1:0.6:2:70,the synthesis temperature was 200°C,and the hydrothermal crystallization time was 24h.The SAPO-34 molecular sieve prepared under this condition has a cubic crystal form with an average size of about 350 nm and a typical type I adsorption isotherm.The average pore volume is 0.195 cm³/g and the specific surface area is 527.8 m²/g.The SAPO-34molecular sieve membrane was prepared by a secondary growth method using tetraethylammonium hydroxide and di-n-propylamine as a double template and the surface was modified with an ion solution.Finally,the scanning electron microscopy and single gas permeation characterization showed that the surface of the SAPO-34 molecular sieve membrane was smooth,continuous and dense with no intercrystalline pore defects.The SAPO-34/carbon composite membrane was prepared by introducing SAPO-34molecular sieve crystal into the carbon membrane.In the precursor liquid molecular sieve mass fraction of 2%,phenolic resin content of 30%,in the alumina carrier tube vacuum level of 0.05MPa after two lifts after high-temperature carbonization of the composite film surface prepared without obvious defects.The gas separation performance test showed that the separation factor of SAPO-34 to H₂/CO₂ is 6.76,the permeability of H₂ and CO₂ is 5.5×10^-77 mol/m²sPa and0.81×10^-7mol/m²sPa at 298K.By introducing SAPO-34 seeds into the phenolic resin solution,the separation factor of H₂/N₂ for the SAPO-34/carbon composite membranes prepared by high-temperature carbonization reached 26.46.The permeabilities of H₂ and N₂ are 1.88×10^-77 mol/m^-2s^-1Pa^-11 and 3.19×10^-88 mol/m^-2s^-1Pa,respectively.