Introduction Important environmental challenges, such as the reduction of greenhouse gas emission, involve the treatment of large gas volumes. Membrane processes based on highly permeable high free volume polymers may represent a valid alternative to traditional separation processes used. Among high free-volume polymers, commercial glassy perfluoropolymers such as Teflon AF and Hyflon AD satisfy requirements of high chemical stability and resistance to corrosive gases. More recently, novel high free-volume polymers of intrinsic microporosity, like PIM-1, or polymers based on silicon-containing polynorbornene analogs, were designed and synthesised [1, 2]. They combine good thermal and chemical stability with a solubility controlled permeation and are recognized as being among the most interesting materials nowadays available for membrane gas separation. Figure 1. High free volume polymers used for the fabrication of composite membranes. Practical applications at high pressure require composite membranes with a highly permeable thin selective dense layer applied onto a porous and mechanically stable support [3]. The achievement of defect-free samples requires an optimal choice of both polymer and support and of the coating conditions, such as polymer concentration, solvent type, etc. [4]. This work presents the preparation and characterization of composite membranes based on PIM-1, addition-type poly(tricyclononene)s and glassy perfluoropolymers (Fig. 1). The membranes were prepared by coating hollow fibers and flat sheet supports with a dilute polymer solution, followed by solvent evaporation. Highly fluorinated Fluoroplast-42 membranes with different pore sizes were used as flat sheet support, while PVDF and PAN-based hollow fibres were used as support with a higher surface/volume ratio. Morphology and pore size distribution of the porous supports were investigated and the coating method was optimized. Permeability measurements were carried out with pure gases and gas mixtures. Dense films were also prepared and tested as a reference for the gas permeation properties. Results and Discussion Defect-free composite samples were obtained for all systems under the appropriate coating conditions (coating method, solvent type and polymer concentration). Figure 2 presents the cross section of some representative samples. Figure 2. SEM micrographs of a cross-section of some composite membranes. (a) Hyflon AD60X on a PAN hollow fibre; (b) PIM-1 on a PAN hollow fibre; (c) Poly(3,4-TCNSi2) on F-42 (50 nm) flat support. These membranes present a high CO2 permeance, up to 5 m3 m-2 h-1 bar-1. The resulting values of CO2/N2 selectivity, relevant for the CO2 capture from flue gas, were 24 for PIM-1, 9 in the case of addition poly(tricyclononene), 8 in the case of Hyflon AD 60X and 5 for Teflon AF 2400. Besides CO2 and nitrogen, different gas pairs will be studied. The best results achieved will be used as a guide for the production of membrane modules for large scale application tests. Acknowledgements The European Community's Seventh Framework Programme (FP7/2007-2013) is acknowledged for funding this work under the agreement no. NMP3-SL-2009-228631, project DoubleNanoMem. JSC STC "Vladipor" (Russia) is gratefully acknowledged for supplying the flat sheet supports. References [1]P.M. Budd, N.B. McKeown, Highly permeable polymers for gas separation membranes, Polym. Chem. 1 (2010) 63-68. [2]M. Gringolts, M. Bermeshev, Yu. Yampolskii, L. Starannikova, V. Shantarovich, E. Finkelshtein, New high permeable addition poly(tricyclononenes) with Si(CH3)3 side groups. Synthesis, gas permeation parameters and free volume, Macromolecules 43 (2010) 7165-7172. [3]I. Pinnau, J.G. Wijmans, I. Blume, T. Kuroda, K.-V. Peinemann, Gas permeation through composite membranes, J. Membr. Sci. 37 (1988) 81-88. [4]F. Bazzarelli, P. Bernardo, F. Tasselli, G. Clarizia, J.C. Jansen, Multilayer composite SBS membranes for pervaporation and gas separation, Sep. Purif. Technol. 80/3 (2011) 635-642.
Composite membranes based on high free volume polymers for gas separation
F Bazzarelli;P Bernardo;F Tasselli;G Clarizia;JC Jansen;
2012
Abstract
Introduction Important environmental challenges, such as the reduction of greenhouse gas emission, involve the treatment of large gas volumes. Membrane processes based on highly permeable high free volume polymers may represent a valid alternative to traditional separation processes used. Among high free-volume polymers, commercial glassy perfluoropolymers such as Teflon AF and Hyflon AD satisfy requirements of high chemical stability and resistance to corrosive gases. More recently, novel high free-volume polymers of intrinsic microporosity, like PIM-1, or polymers based on silicon-containing polynorbornene analogs, were designed and synthesised [1, 2]. They combine good thermal and chemical stability with a solubility controlled permeation and are recognized as being among the most interesting materials nowadays available for membrane gas separation. Figure 1. High free volume polymers used for the fabrication of composite membranes. Practical applications at high pressure require composite membranes with a highly permeable thin selective dense layer applied onto a porous and mechanically stable support [3]. The achievement of defect-free samples requires an optimal choice of both polymer and support and of the coating conditions, such as polymer concentration, solvent type, etc. [4]. This work presents the preparation and characterization of composite membranes based on PIM-1, addition-type poly(tricyclononene)s and glassy perfluoropolymers (Fig. 1). The membranes were prepared by coating hollow fibers and flat sheet supports with a dilute polymer solution, followed by solvent evaporation. Highly fluorinated Fluoroplast-42 membranes with different pore sizes were used as flat sheet support, while PVDF and PAN-based hollow fibres were used as support with a higher surface/volume ratio. Morphology and pore size distribution of the porous supports were investigated and the coating method was optimized. Permeability measurements were carried out with pure gases and gas mixtures. Dense films were also prepared and tested as a reference for the gas permeation properties. Results and Discussion Defect-free composite samples were obtained for all systems under the appropriate coating conditions (coating method, solvent type and polymer concentration). Figure 2 presents the cross section of some representative samples. Figure 2. SEM micrographs of a cross-section of some composite membranes. (a) Hyflon AD60X on a PAN hollow fibre; (b) PIM-1 on a PAN hollow fibre; (c) Poly(3,4-TCNSi2) on F-42 (50 nm) flat support. These membranes present a high CO2 permeance, up to 5 m3 m-2 h-1 bar-1. The resulting values of CO2/N2 selectivity, relevant for the CO2 capture from flue gas, were 24 for PIM-1, 9 in the case of addition poly(tricyclononene), 8 in the case of Hyflon AD 60X and 5 for Teflon AF 2400. Besides CO2 and nitrogen, different gas pairs will be studied. The best results achieved will be used as a guide for the production of membrane modules for large scale application tests. Acknowledgements The European Community's Seventh Framework Programme (FP7/2007-2013) is acknowledged for funding this work under the agreement no. NMP3-SL-2009-228631, project DoubleNanoMem. JSC STC "Vladipor" (Russia) is gratefully acknowledged for supplying the flat sheet supports. References [1]P.M. Budd, N.B. McKeown, Highly permeable polymers for gas separation membranes, Polym. Chem. 1 (2010) 63-68. [2]M. Gringolts, M. Bermeshev, Yu. Yampolskii, L. Starannikova, V. Shantarovich, E. Finkelshtein, New high permeable addition poly(tricyclononenes) with Si(CH3)3 side groups. Synthesis, gas permeation parameters and free volume, Macromolecules 43 (2010) 7165-7172. [3]I. Pinnau, J.G. Wijmans, I. Blume, T. Kuroda, K.-V. Peinemann, Gas permeation through composite membranes, J. Membr. Sci. 37 (1988) 81-88. [4]F. Bazzarelli, P. Bernardo, F. Tasselli, G. Clarizia, J.C. Jansen, Multilayer composite SBS membranes for pervaporation and gas separation, Sep. Purif. Technol. 80/3 (2011) 635-642.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
