Zhang Xiongfu

Synthesis and characterization of Fe-MFI zeolite membrane on a porous α-Al2O3 tube

Fe-MFI and MFI membranes have been prepared by in-situ hydrothermal treatment on porous α-Al 2 O 3 tubes. It has been shown by XRD, IR, SEM and single gas permeation measurements that the crack-free Fe-MFI zeolite membrane are formed and Fe species are incorporated into the framework of zeolite. The permeation rate of H 2 and separation factor (H 2 /C 3 H 8 ) for the synthesized Fe-MFI zeolite membrane are 3.0x10 -6 mol/s.m 2 .Pa and 25.8, respectively. About 15% conversion increase of ethylbenzene to styrene using the membrane as a reactor is achieved over the fixed-bed reactor. The reactivity of the Fe-MFI membrane is better than that of the Al-ZSM-5 membrane. The reason may be that the Fe-ZSM-5 preferentially adsorbs the ethylbenzene, which may be beneficial to the conversion of ethylbenzene, and the adsorption amount of styrene on Fe-ZSM-5 is much less than that on Al-ZSM-5, which may favorably prevent carbon deposition on the Fe-ZSM membrane and result in a higher conversion of ethylbenzene.

Factors affecting the formation of zeolite seed layers and the effects of seed layers on the growth of zeolite silicalite-1 membranes

The present study investigates the formation of silicalite-1 seed layers on a porous carbon support of 0.5 μm pore size and α-A12O3 supports with different pore sizes (0.1 μm and 4 μm) via the slip-casting technique. The effects of support property, seed size and solvent on the formation of seed layers were investigated in detail. The growth of silicalite-1 membranes on different seeded supports by hydrothermal synthesis was also evaluated. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations indicate that a continuous seed layer can be obtained on the smooth support of 0.1 μm pore size by using any seed of 100 nm, 600 nm or 2.2 μm in size, whereas, on the coarse supports with either 0.5 μm or 4 μm pore size, a continuous seed layer cannot be formed using the above seed sizes and the same seeding time. At a longer contact time, a seed layer can also be formed using 100 nm seed on the supports with larger pore size. However, the layer is not uniform and smooth. For a hydrophobic porous carbon support, seeding ethanol suspension, which has weak polarity, favors the formation of a continuous seed layer. The seed layers and membranes grown from the smaller seed are more uniform and continuous and possess smoother surfaces than those from the larger seed. The seed layer and respective grown membrane formed from nanosized seed (100 nm) are the most uniform and compact. With this method of seeded secondary synthesis of zeolite membranes, the quality of a membrane mainly depends on the quality of the seed layer.

预涂晶种诱导法在α-Al 2 O 3 陶瓷管载体上合成ZIF-8膜

以纳米级ZIF-8晶体粒子为晶种, 利用晶种诱导二次生长法在α-Al 2 O 3 陶瓷管载体上制备出连续的ZIF-8膜, 并详细考察了晶种涂层液中晶种含量、成膜温度和添加剂PEI、甲酸钠用量等参数对ZIF-8成膜的调控影响. 经SEM、XRD和气体渗透分析结果表明: 制备的ZIF-8纳米粒子的粒径约为100~150 nm, 粒度分布较均匀, 适宜作为成膜的晶种; 在晶种液中添加适量的PEI作为偶联剂有利于连续ZIF-8晶种层及膜的形成; 在成膜液中添加适量的甲酸钠能有效阻止载体表面晶种层的溶解脱落. SEM显示所得ZIF-8膜的晶体粒径均一、晶粒间连接紧密且无明显裂痕, 膜层厚度约为18 μm. 单组分气体渗透测试可知, H 2 /CO 2 的分离因数为5.4, H 2 /CH 4 的分离因数为2.56, 气体通过ZIF-8膜均属于努森扩散范围.以纳米级ZIF-8晶体粒子为晶种, 利用晶种诱导二次生长法在α-Al 2 O 3 陶瓷管载体上制备出连续的ZIF-8膜, 并详细考察了晶种涂层液中晶种含量、成膜温度和添加剂PEI、甲酸钠用量等参数对ZIF-8成膜的调控影响. 经SEM、XRD和气体渗透分析结果表明: 制备的ZIF-8纳米粒子的粒径约为100~150 nm, 粒度分布较均匀, 适宜作为成膜的晶种; 在晶种液中添加适量的PEI作为偶联剂有利于连续ZIF-8晶种层及膜的形成; 在成膜液中添加适量的甲酸钠能有效阻止载体表面晶种层的溶解脱落. SEM显示所得ZIF-8膜的晶体粒径均一、晶粒间连接紧密且无明显裂痕, 膜层厚度约为18 μm. 单组分气体渗透测试可知, H 2 /CO 2 的分离因数为5.4, H 2 /CH 4 的分离因数为2.56, 气体通过ZIF-8膜均属于努森扩散范围.