| Summary: |
Carbon molecular sieve membranes (CMSM), also known as ultrananoporous carbon membranes, are a promising gas separation technology for the near future [1,2,3]. Compared to the polymeric membranes, CMSM are more selective and permeable and possible of fine-tuning of the pore size [1], they are also heat and corrosion resistant [3]. CMSM have a very narrow pore size distribution, with pores in the range between 0.3 and 0.6 nm. These extraordinary properties make this field one of the fastest growing among membrane research [3].
The development of molecular sieve membranes, started about two decades ago, with the pioneering work by Soffer (carbon molecular sieve membranes) and by Barrer and Suzuki (zeolite membranes) [2]. So far, zeolite membranes have reached higher commercial impact than carbon molecular sieves. Zeolite membranes can be easily functionalised with catalysts or fixed site carriers. However, they are difficult to produce defect free and are not pore size tuneable. On the other hand, CMSM production leads to limited reproducibility in terms of the membranes properties. In addition, these materials lose performance in presence of oxygen [2,11].
CMSM research is still mainly focused on experimenting new precursors and tuning each production step using an empirical approach [3,4]. A more systematic work is urgently needed. Recent works in our lab led to the determination of the ultramicropore size distribution of a CMSM for the first time [7]. This pioneer study brought sound experimental evidences to the long ago proposed model for the pore system, which considers pores with constrictions with a very narrow size distribution [12]. It was even possible to determine the average constrictions size and its volume fraction related to the ultramicropore system. Other methods were employed to characterise CMSM and better understand the mass transport mechanism [1]. The objective of the present project is to apply the characterisation methods available at ou  |
Summary
Carbon molecular sieve membranes (CMSM), also known as ultrananoporous carbon membranes, are a promising gas separation technology for the near future [1,2,3]. Compared to the polymeric membranes, CMSM are more selective and permeable and possible of fine-tuning of the pore size [1], they are also heat and corrosion resistant [3]. CMSM have a very narrow pore size distribution, with pores in the range between 0.3 and 0.6 nm. These extraordinary properties make this field one of the fastest growing among membrane research [3].
The development of molecular sieve membranes, started about two decades ago, with the pioneering work by Soffer (carbon molecular sieve membranes) and by Barrer and Suzuki (zeolite membranes) [2]. So far, zeolite membranes have reached higher commercial impact than carbon molecular sieves. Zeolite membranes can be easily functionalised with catalysts or fixed site carriers. However, they are difficult to produce defect free and are not pore size tuneable. On the other hand, CMSM production leads to limited reproducibility in terms of the membranes properties. In addition, these materials lose performance in presence of oxygen [2,11].
CMSM research is still mainly focused on experimenting new precursors and tuning each production step using an empirical approach [3,4]. A more systematic work is urgently needed. Recent works in our lab led to the determination of the ultramicropore size distribution of a CMSM for the first time [7]. This pioneer study brought sound experimental evidences to the long ago proposed model for the pore system, which considers pores with constrictions with a very narrow size distribution [12]. It was even possible to determine the average constrictions size and its volume fraction related to the ultramicropore system. Other methods were employed to characterise CMSM and better understand the mass transport mechanism [1]. The objective of the present project is to apply the characterisation methods available at our lab to drive the optimisation of CMSM in a systematic way.
Design of Experiment (DOE) is a statistical methodology, recently made available in software applications, which allows for the structured determination of the relationship between factors affecting a process and the output of that process [5]. This methodology allows obtention of an interpolation model of a multivariable system and finding local optima values, minimising the number of experimental runs and maximising the model's sensitivity.
Starting from a CMSM precursor, the pre-treatment, pyrolysis, chemical vapour deposition (CVD) and activation steps will be performed within this project. For each step the membranes will be characterised using the developed characterisation methods and experiments conducted using the DoE methodology [e.g. 13]. CMSM membranes will be optimised for the O2/N2 separation. Blue Membranes in Germany [10], with whom we have collaborating for two years, will supply the membranes precursor. |