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

理想沸石膜在石油炼制/石化和精细化工等领域有着广泛的应用前景。沸石膜在工业气体分离过程中具有巨大的实际应用潜力，引起了人们极大的兴趣。具有LTA， BEA， FAU， MOR， FER和CHA型框架的沸石膜由于其特殊的孔隙几何结构而得到了广泛的研究。然而，尽管沸石膜在工业气体分离过程中取得了令人印象深刻的成就，尽管在渗透蒸发膜过程中技术应用取得了成功，但在工业气体分离过程中仍未大规模使用沸石膜。理想的沸石膜需要两个组成部分：提供分离性能的完美致密沸石层和为系统提供机械强度而不影响分离和运输行为的支撑。多晶沸石层的厚度和均匀性直接关系到膜的通量和选择性性能。因此，需要在宏观多孔载体上具有可忽略不计的晶间缺陷的超薄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，应避免或减少晶间空隙到可以忽略不计的数量。然而，由于具有相同晶体表面电荷的单晶的不完美的共生行为或由于沸石晶体和载体的热膨胀不同而形成的晶间孔（裂纹、空隙）的形成总是不能避免的。这些晶间孔被称为在膜分离过程中导致非选择性输运的缺陷。与沸石一样，碳分子筛具有热稳定性和微孔性。它们可以通过有机前驱体的热解得到。此外，小的有机化合物，如苯，已被用作制备多孔材料的碳前驱体。因此，通常采用化学气相沉积技术，然后进行热处理来制备微孔碳层。然而，目前还没有制造出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，通过将柔性碳纳米结构集成到交错生长的沸石晶体堆的空隙中，从而形成完全规则的微孔膜。根据我们的建议，规则的沸石孔网络将成为膜的主要骨干，碳将填补不规则的缺陷。这导致了一种普遍适用的缺陷阻塞——产生“碳集成沸石膜（CiZM）”。

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)'.