Carbon integrated zeolite membranes (CiZM): Defect blocking with carbon for high selective and thermal stable membranes

理想的沸石膜在石油炼制/石化和精细化工工业中具有广泛的兴趣。沸石分子筛膜在工业气体分离过程中有着巨大的应用潜力，因而受到人们的广泛关注。具有LTA、CH 4、FAU、莫尔比、FER和CHA型骨架结构的分子筛膜由于其特殊的孔结构而得到了广泛的研究。然而，尽管在沸石膜上进行了令人印象深刻的工作，但仍然没有在工业气体分离过程中大规模使用它们，尽管在渗透蒸发膜过程中的技术应用是成功的。一个理想的沸石膜需要两个组成部分：一个完美的致密沸石层，提供分离性能和支持，提供机械强度的系统，而不影响分离和传输行为。多晶沸石层的厚度和均匀性与膜的通量和选择性性能直接相关。因此，需要在大孔载体上具有可忽略的晶间缺陷的致密层来生产具有高生产率和选择性的膜。为了生产理想的沸石膜，应避免晶间空隙或将其减少到可忽略的量。然而，由于例如具有相同晶体表面电荷的单晶的不完美共生行为或由于沸石晶体和载体的热膨胀差异，不能总是避免晶间孔（裂纹、空隙）的形成。这些晶间孔被称为导致膜分离过程中非选择性传输的缺陷。与沸石一样，碳分子筛是热稳定的和微孔的。它们可以通过有机前体的热解获得。小的有机化合物，如苯，也被用作制备多孔材料的碳前体。因此，通常使用化学气相沉积技术，然后进行热处理来生产微孔碳层。然而，到目前为止，还没有获得具有规则微孔结构的连续碳膜。因此，我们提出了一种新的途径，以一个完全规则的微孔膜，通过整合灵活的碳纳米结构到空隙的共生沸石晶体堆栈。根据我们的建议，规则的沸石孔网络将是膜的主要骨架，其中碳将填充不规则的缺陷。这导致了通常适用的产生缺陷阻塞的“碳集成沸石膜（CiZM膜）”。

Ideal zeolite membranes have widespread interest in the petroleum refining/petrochemical and fine chemical industries. Nowadays enormous interests are shown on the zeolite membranes as these membranes have huge potential for practical applications in industrial gas separation processes. Zeolite membranes with LTA, BEA, FAU, MOR, FER and CHA type frameworks have been studied intensively due to their special pore geometry. However, despite the impressive work done on zeolite membranes, there are still no large-scale uses of them in industrial gas separation processes although there is a success for the technical application in pervaporation membrane processes. An ideal zeolite membrane requires two components: a perfect dense zeolite layer which provides the separation properties and a support which provides the mechanical strength for the system without affecting the separation and transport behavior. The thickness and uniformity of the polycrystalline zeolite layer is directly related with the membrane performance in terms of flux and selectivity. As a consequence, ultrathin and dense layers with negligible intercrystalline defects onto a macro porous support are required to produce a membrane with high productivity and selectivity. To produce ideal zeolite membranes intercrystalline voids should be avoided or reduced to negligible quantity. However, the formation of the intercrystalline pores (cracks, voids) due to e.g. the imperfect intergrowing behavior of single crystals with the same crystal surface charge or due to the differences of the thermal expansion of the zeolite crystals and the supports cannot always be avoided. These intercrystalline pores are termed as defects leading to non-selective transport in the membrane separation processes. Like zeolites, carbon molecular sieves are thermally stable and microporous. They can be obtained by pyrolysis of an organic precursor. Also small organic compounds, like benzene, have been used as carbon precursor for the preparation of porous materials. Thus, chemical vapour deposition technique followed by a thermal treatment had been often utilized producing microporous carbon layers. However, a continuous carbon film of regular microporous structure is not achieved up till now. Therefore, we are proposing a new pathway to a totally regular microporous membrane by integrating flexible carbon nanostructures into the voids of the intergrown zeolite crystal stacks. According to our proposal, the regular zeolite pore network will be primary backbone of the membrane where the carbon will fill the irregular defects. This results in a generally applicable defect blocking - producing 'Carbon integrated zeolite membranes (CiZM)'.