- Email: [email protected]
Design of multilayered ceramic MIEC membranes
Desalination 199 (2006) 299–301
Design of multilayered ceramic MIEC membranes Vladimir V. Zyryanova*, Vladislav A. Sadykovb a
Institute of Solid State Chemistry SB RAS, Kutateladze 18, Novosibirsk, Russia email: [email protected] b Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia Received 20 October 2005; accepted 1 March 2006
1. Introduction This work is aimed at development of tubular multilayered ceramic and cermet membranes with mixed ionic-electronic conductivity (MIEC) for the catalytic processes of the high-temperature (HT) partial oxidation of methane (POM) [1], and high-purity hydrogen generation from water, air and hydrocarbons [2]. Conventional processes for the production of syngas are based on steam reforming and/or partial oxidation of methane. Steam reforming is energy-intensive due to highly endothermic nature of reaction. The most significant cost associated with partial oxidation is that of an oxygen plant. Membrane technologies make it possible to integrate oxygen separation, steam reforming and partial oxidation in a single reactor. The main advantage of HT membrane technology for high-pure hydrogen production is that it does not require purification of hydrocarbon feedstock from sulfur compounds. 2. Results and discussion The application of MIEC membranes is limited by some disadvantages of existing materials: low stability in reduced atmosphere, poor *Corresponding author.
mechanical properties, too high temperature of sintering Ts, instability to steam. Another group of membrane materials called the dual-phase composites is comprised of the mixture of an oxide ionic conductor and an electronically conducting phase [3,4]. In composites the regulation of mixed conductivity is possible by adjusting the fraction of constituents. Some rules for the choice of compatible composites are formulated in [4]. Architecture of multilayered membrane, Fig. 1, is cost efficient and possesses promising features. MIEC layer with gradient porosity and thin gas-tight layer provide maximal flux of oxygen under condition of mixed control of the surface exchange kinetics and bulk diffusion. Porous layer from MIEC compositions, as well as dense layers from ceramic or ceramic-metal alloy composites may be produced by mechanochemical ceramic technique [1,5]. Optimal benches 10–15 g of ready for sintering powders with complex compositions were obtained for 5–30 min of mechanical treatment at room T. Fractions of agglomerates comprising from ~30 nm crystallites were separated in electro-mass-classifier technique (EMC). For production of gas-tight and porous MIEC ceramic layers, the submicron and coarse fractions of powders were used. The density of crystallites derived by mechanosynthesis is
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.176
300
V.V. Zyryanov, V.A. Sadykov / Desalination 199 (2006) 299–301 Air or steam 1 2 H + CO or 2 H2O + CO2 6
4 3 Hot
Ts, K
CH4 5
1800
For 7 fluorites r = 0.858
1600
1400
For 18 perovskites r = 0.733
Cold
Fig. 1. Tubular CMR with multilayered membrane. 1, Porous modified porcelain; 2, buffer layer; 3, porous MIEC layer; 4, dense MIEC layer; 5, protective thin film; 6, finely dispersed catalyst.
~91% only [5]. This peculiarity allows obtaining different layers of membrane with negligible misfit in shrinkage. The geometry of dead-end tubular membrane, fabricated by conventional casting technology, is optimal for researches due to no problems related to sealing. Such approach provides the fast and correct testing of catalytic membrane reactors (CMR) developed from compatible materials with different supported catalysts. However, in such a way there are many difficulties in the preparation of compatible materials [3,4], optimization of chemical compositions and operations parameters. The new strategy to development of multilayered membranes, proposed in [1], demands many efforts, mainly concerning the material for protective film with MIEC and catalytic properties on the internal side of membrane, and fabrication of nanopowders possessing simultaneously high conducting properties and required Ts to eliminate the misfit in shrinkage values between different layers, which leads to a cracking of membrane. To provide a compatibility of materials in multilayered membrane, it is necessary to scan novel complex compositions with unknown ‘melting’ point Tm and unpredictable Ts. For synthesis of fluorites and perovskites with required Ts, it is necessary to find a simple empirical rule for its estimation. To solve this problem, a sintering of nanopowders, derived by
1200 1600
1800
2000
2200
2400
2600
2800
Tm, K
Fig. 2. Linear fit for dependence of Ts on calculated Tm for complex oxides. Open circles – fluorites, squares – perovskites.
mechanosynthesis at similar conditions, was studied in 32 systems, including potential membrane materials. Linear shrinkage value 12% was taken as an optimal parameter of sintering for relative comparing studied systems. Ts for sintering up to 12% linear shrinkage were estimated by extrapolation of experimental data obtained at 4 different temperatures. After elimination of all extraneous factors, influencing on sintering of ceramics [5], a plausible linear correlation between Ts and calculated average Tm was obtained for complex fluorites and perovskites AxBy… (Tm= x·TmA +y·TmB +…), Fig. 2. Tens reactors with 30 cm2 gas-tight membrane were successfully fabricated at Ts = 1350–1400° C from compatible complex perovskites, fluorites and composites developed according to formulated rules. Testing of CMR’s for optimization of many operation parameters and compositions of the used materials and catalysts is in progress. Usual procedure of separate testing of membrane materials for following development of CMR is not correct enough due to inevitable chemical interaction between components during sintering. In a report, primary results of membrane HT technology for methane conversion will be presented.
V.V. Zyryanov, V.A. Sadykov / Desalination 199 (2006) 299–301
3. Conclusions New approaches to preparation of compatible materials are proposed and successfully realized in development of sophisticated multilayered CMR for the methane conversion. Acknowledgments
[2]
[3]
[4]
This work is supported by ISTC and RFBR, 06-03-32131. References [5] [1]
V.V. Zyryanov, N.F. Uvarov, V.A. Sadykov, et al, Mechanosynthesis of complex oxides and preparation of mixed conducting nanocomposites for catalytic membrane reactors, Catalysis Today, 104 (2005) 114–119.
301
U. Balachandran, T.H. Lee, S. Wang and S.E. Dorris, Use of mixed conducting membranes to produce hydrogen by water dissociation, Int. J. Hydrogen Energy 29 (2004) 291–296. V.V. Kharton, A.V. Kovalevsky, A.P. Viskup, et al, Oxygen permeability Ce0.8Gd0.2O2-xLa0.7Sr0.3MnO3-x composite membranes, J. Electrochem. Soc., 147 (2000) 2814–2821. V.V. Zyryanov, V.A. Sadykov, N.F. Uvarov, et al, Mechanosynthesis of complex oxides with fluorite and perovskite-related structures and their sintering into nanocomposites with mixed ionic-electronic conductivity, Solid State Ionics, 176 (2005) 2813– 2818. V.V. Zyryanov, Mechanism of mechanochemical synthesis of complex oxides and peculiarities of their nanostructurization determining sintering, Sci. Sintering, 37 (2005) 77–92.
Design of multilayered ceramic MIEC membranes Vladimir V. Zyryanova*, Vladislav A. Sadykovb a
Institute of Solid State Chemistry SB RAS, Kutateladze 18, Novosibirsk, Russia email: [email protected] b Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia Received 20 October 2005; accepted 1 March 2006
1. Introduction This work is aimed at development of tubular multilayered ceramic and cermet membranes with mixed ionic-electronic conductivity (MIEC) for the catalytic processes of the high-temperature (HT) partial oxidation of methane (POM) [1], and high-purity hydrogen generation from water, air and hydrocarbons [2]. Conventional processes for the production of syngas are based on steam reforming and/or partial oxidation of methane. Steam reforming is energy-intensive due to highly endothermic nature of reaction. The most significant cost associated with partial oxidation is that of an oxygen plant. Membrane technologies make it possible to integrate oxygen separation, steam reforming and partial oxidation in a single reactor. The main advantage of HT membrane technology for high-pure hydrogen production is that it does not require purification of hydrocarbon feedstock from sulfur compounds. 2. Results and discussion The application of MIEC membranes is limited by some disadvantages of existing materials: low stability in reduced atmosphere, poor *Corresponding author.
mechanical properties, too high temperature of sintering Ts, instability to steam. Another group of membrane materials called the dual-phase composites is comprised of the mixture of an oxide ionic conductor and an electronically conducting phase [3,4]. In composites the regulation of mixed conductivity is possible by adjusting the fraction of constituents. Some rules for the choice of compatible composites are formulated in [4]. Architecture of multilayered membrane, Fig. 1, is cost efficient and possesses promising features. MIEC layer with gradient porosity and thin gas-tight layer provide maximal flux of oxygen under condition of mixed control of the surface exchange kinetics and bulk diffusion. Porous layer from MIEC compositions, as well as dense layers from ceramic or ceramic-metal alloy composites may be produced by mechanochemical ceramic technique [1,5]. Optimal benches 10–15 g of ready for sintering powders with complex compositions were obtained for 5–30 min of mechanical treatment at room T. Fractions of agglomerates comprising from ~30 nm crystallites were separated in electro-mass-classifier technique (EMC). For production of gas-tight and porous MIEC ceramic layers, the submicron and coarse fractions of powders were used. The density of crystallites derived by mechanosynthesis is
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.176
300
V.V. Zyryanov, V.A. Sadykov / Desalination 199 (2006) 299–301 Air or steam 1 2 H + CO or 2 H2O + CO2 6
4 3 Hot
Ts, K
CH4 5
1800
For 7 fluorites r = 0.858
1600
1400
For 18 perovskites r = 0.733
Cold
Fig. 1. Tubular CMR with multilayered membrane. 1, Porous modified porcelain; 2, buffer layer; 3, porous MIEC layer; 4, dense MIEC layer; 5, protective thin film; 6, finely dispersed catalyst.
~91% only [5]. This peculiarity allows obtaining different layers of membrane with negligible misfit in shrinkage. The geometry of dead-end tubular membrane, fabricated by conventional casting technology, is optimal for researches due to no problems related to sealing. Such approach provides the fast and correct testing of catalytic membrane reactors (CMR) developed from compatible materials with different supported catalysts. However, in such a way there are many difficulties in the preparation of compatible materials [3,4], optimization of chemical compositions and operations parameters. The new strategy to development of multilayered membranes, proposed in [1], demands many efforts, mainly concerning the material for protective film with MIEC and catalytic properties on the internal side of membrane, and fabrication of nanopowders possessing simultaneously high conducting properties and required Ts to eliminate the misfit in shrinkage values between different layers, which leads to a cracking of membrane. To provide a compatibility of materials in multilayered membrane, it is necessary to scan novel complex compositions with unknown ‘melting’ point Tm and unpredictable Ts. For synthesis of fluorites and perovskites with required Ts, it is necessary to find a simple empirical rule for its estimation. To solve this problem, a sintering of nanopowders, derived by
1200 1600
1800
2000
2200
2400
2600
2800
Tm, K
Fig. 2. Linear fit for dependence of Ts on calculated Tm for complex oxides. Open circles – fluorites, squares – perovskites.
mechanosynthesis at similar conditions, was studied in 32 systems, including potential membrane materials. Linear shrinkage value 12% was taken as an optimal parameter of sintering for relative comparing studied systems. Ts for sintering up to 12% linear shrinkage were estimated by extrapolation of experimental data obtained at 4 different temperatures. After elimination of all extraneous factors, influencing on sintering of ceramics [5], a plausible linear correlation between Ts and calculated average Tm was obtained for complex fluorites and perovskites AxBy… (Tm= x·TmA +y·TmB +…), Fig. 2. Tens reactors with 30 cm2 gas-tight membrane were successfully fabricated at Ts = 1350–1400° C from compatible complex perovskites, fluorites and composites developed according to formulated rules. Testing of CMR’s for optimization of many operation parameters and compositions of the used materials and catalysts is in progress. Usual procedure of separate testing of membrane materials for following development of CMR is not correct enough due to inevitable chemical interaction between components during sintering. In a report, primary results of membrane HT technology for methane conversion will be presented.
V.V. Zyryanov, V.A. Sadykov / Desalination 199 (2006) 299–301
3. Conclusions New approaches to preparation of compatible materials are proposed and successfully realized in development of sophisticated multilayered CMR for the methane conversion. Acknowledgments
[2]
[3]
[4]
This work is supported by ISTC and RFBR, 06-03-32131. References [5] [1]
V.V. Zyryanov, N.F. Uvarov, V.A. Sadykov, et al, Mechanosynthesis of complex oxides and preparation of mixed conducting nanocomposites for catalytic membrane reactors, Catalysis Today, 104 (2005) 114–119.
301
U. Balachandran, T.H. Lee, S. Wang and S.E. Dorris, Use of mixed conducting membranes to produce hydrogen by water dissociation, Int. J. Hydrogen Energy 29 (2004) 291–296. V.V. Kharton, A.V. Kovalevsky, A.P. Viskup, et al, Oxygen permeability Ce0.8Gd0.2O2-xLa0.7Sr0.3MnO3-x composite membranes, J. Electrochem. Soc., 147 (2000) 2814–2821. V.V. Zyryanov, V.A. Sadykov, N.F. Uvarov, et al, Mechanosynthesis of complex oxides with fluorite and perovskite-related structures and their sintering into nanocomposites with mixed ionic-electronic conductivity, Solid State Ionics, 176 (2005) 2813– 2818. V.V. Zyryanov, Mechanism of mechanochemical synthesis of complex oxides and peculiarities of their nanostructurization determining sintering, Sci. Sintering, 37 (2005) 77–92.