小晶粒NaX沸石膜的制备与表征

Preparation and Characterization of Ultrafine Crystal NaX Membrane

分别以硅溶胶和异丙醇铝为硅源和铝源,采用预涂晶种的方式,用水热合成法在氧化铝载体上合成出小晶粒NaX分子筛膜.各组分配比为:SiO2:A12O3=3.85～4.2,Na2O:SiO2=1.2～1.5,H2O:Na2O=40～60,用扫描电镜、X射线衍射等手段对沸石膜进行了表征,可以看到分子筛膜生长的晶粒细小,沸石晶体的大小在500～800 nm,生长致密良好,覆盖完全,膜厚约为10 μm.小晶粒NaX沸石膜的H2渗透率为2.45×10-6 mol·m2/(s·Pa),H2/N2的理想分离系数达到4.21,H2/C3H8的理想分离系数达到7.56,超过对应的努森扩散值3.74和4.69.

Continuous ultrafine crystal NaX membrane was synthesized hydrothermally on the outer surface of α-alumina tube support（12 mm o.d., 8 mm i.d.）. Surface-modified tubes were seeded with ultrafine zeolite X crystals prior to the membrane synthesis. The molar composition of the starting gel of NaX membrane was SiO2：Al2O3=3.85～4.2, Na2O：SiO2=1.2～1.5, H2O：Na2O=40～60. The outer surface of the tube was completely covered with zeolite crystals, which were about 500～800 nm in size and about 10 μm in thickness of the membrane as judged by a scanning electron microscope （SEM）. The tests on permeation of H2, N2 and C3H8 were carried out to get the ideal separation selectivity of H2/N2 and H2/C3H8 systems. The measured permeability of H2 was about 2.45×10^-6 mol·m2/（s·Pa）and the ideal selectivity of H2/N2 and H2/C3H8 was 4.21 and 7.56, which are higher than the respective Knudsen diffusion ratios of 3.74 and 4.69.