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

• Applicants: Professor Dr.-Ing. Malte Kaspereit; Dr.-Ing. Hannes Richter; Professor Dr. Wilhelm Schwieger
• Subject Area: Technical Chemistry ; Chemical and Thermal Process Engineering
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265847141

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)'.

• DFG Programme: Research Grants