Recently, the use of zeolite framework as separation membranes, chemical sensors, catalysts in membrane reactors, protection or insulation layer has attracted increasing interest in both industrial and academic community [1]. For their high thermal and chemical stability (high resistance to chlorine, oxidants and solvents), zeolite membranes can be used where the polymeric membranes fail. However, the industrial application of zeolite membranes is limited by the costs and low reproducibility during the synthesis process. Up to date, their use at industrial level is only represented by LTA zeolite membranes for organic solvent dehydration by means of pervaporation and vapour permeation processes [2]. The most common procedures to prepare zeolite membranes are the in situ hydrothermal crystallization and the secondary growth method. The last one involves two steps: seeding of zeolite crystals on the support and crystals growth by hydrothermal treatment. This method allows to optimize the conditions of each step due to the possibility to decouple the nucleation from crystal growth. More controllable seeding involves the cross-flow filtration of a zeolite water suspension through a support [3]. To overcome the coverage uniformity problems that occur during the use of tubular supports a new seeding procedure was developed combining the support tilting and rotation with the cross-flow filtration [4]. In the present work for the first time, MFI zeolite membranes on tubular ?-Al2O3 supports were prepared by secondary growth method, using the new cross-flow seeding procedure. The influence of different seeding parameters on the membrane quality was investigated to optimize the seeding step. These parameters were: support pore size, zeolite slurry concentration and crystals size. Morphology of the zeolite layer and crystals topology were examined by scanning electron microscopy and X-ray diffractometry, respectively. The prepared membranes were also characterized in gas and liquid phases by permeation tests.
Preparation of MFI Zeolite Membranes for Water Treatment
C Algieri;L Donato;A Garofalo;E Drioli
2014
Abstract
Recently, the use of zeolite framework as separation membranes, chemical sensors, catalysts in membrane reactors, protection or insulation layer has attracted increasing interest in both industrial and academic community [1]. For their high thermal and chemical stability (high resistance to chlorine, oxidants and solvents), zeolite membranes can be used where the polymeric membranes fail. However, the industrial application of zeolite membranes is limited by the costs and low reproducibility during the synthesis process. Up to date, their use at industrial level is only represented by LTA zeolite membranes for organic solvent dehydration by means of pervaporation and vapour permeation processes [2]. The most common procedures to prepare zeolite membranes are the in situ hydrothermal crystallization and the secondary growth method. The last one involves two steps: seeding of zeolite crystals on the support and crystals growth by hydrothermal treatment. This method allows to optimize the conditions of each step due to the possibility to decouple the nucleation from crystal growth. More controllable seeding involves the cross-flow filtration of a zeolite water suspension through a support [3]. To overcome the coverage uniformity problems that occur during the use of tubular supports a new seeding procedure was developed combining the support tilting and rotation with the cross-flow filtration [4]. In the present work for the first time, MFI zeolite membranes on tubular ?-Al2O3 supports were prepared by secondary growth method, using the new cross-flow seeding procedure. The influence of different seeding parameters on the membrane quality was investigated to optimize the seeding step. These parameters were: support pore size, zeolite slurry concentration and crystals size. Morphology of the zeolite layer and crystals topology were examined by scanning electron microscopy and X-ray diffractometry, respectively. The prepared membranes were also characterized in gas and liquid phases by permeation tests.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
