通过NH4+离子交换的方法获得了HMFI分子筛膜,采用在线化学气相沉积法(CVD)对其进行晶内孔道修饰,以提高其对H2的分离选择性.实验考察了四乙氧基硅烷(TEOS)、甲基二乙氧基硅烷(MDES)和三甲基乙氧基硅烷(TMES)3种不同尺寸修饰源对膜性能的影响.结果表明,尺寸较小的TMES更容易扩散进入分子筛膜的晶内孔道,从而获得了更优的H2/CO2分离性能,修饰后的膜在500℃下H2/CO2的分离因子可达45.9,H2的渗透性为1.43×10^-7 mol/(m2·s·Pa).同时,通过质谱(MS)分析了TMES在HMFI分子筛孔道中的裂解行为,探讨了硅烷修饰的的沉积机理.
On-stream chemical vapor deposition (CVD) method was carried out to modify HMFI zeolite membranes, which were obtained by NH4? ion exchange to improve their hydrogen selective separation performance. The influence of silane size on the separation performance was investigated by using tetraethoxysilane (TEOS), methyldiethoxysilane (MDES) and trimethylethoxysilane (TMES). The results indicated that TMES with smaller size could more easily diffuse into zeolitic pores. The membrane modified by TMES achieved much higher H2/CO2 separation factor up to 45.9 with H2 permeance about 1.43 × 10^-7 mol/(m-2 · s· Pa) at 500 ℃. Mass spectrometry (MS) was used to analyze the cracking products of TMES in HMFI zeolitic pores and deposition mechanism of modification with silane was discussed.