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Steamed Zeolites for Heat Pump Applications and Solar Driven Thermal Adsorption Storage
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 48 (2014) 380 – 383
SHC 2013, International Conference on Solar Heating and Cooling for Buildings and Industry September 23-25, 2013, Freiburg, Germany
Steamed zeolites for heat pump applications and solar driven thermal adsorption storage Thomas H. Herzoga, Jochen Jänchena, Eythymius M. Kontogeorgopoulosb, Wolfgang Lutzc* a
TH Wildau - Technical University of Applied Science,Bahnhofstraße 1,15745 Wildau,Germany b InvenSor GmbH, Gustav-Meyer-Allee 25,13355 Berlin, Germany c BTU – Brandenburg University of Technology, Volmerstraße 13, 12489 Berlin, Germany
Abstract The influence of the dealumination degree of NaY with respect to the water adsorption properties was investigated by infrared spectroscopy, thermogravimetry and isotherm measurements. The modification of the samples is a result of a steaming process at different temperatures in dependence of time. It was found that dealumination controls the hydrophilic behavior of NaY and contributes to defined low desorption temperatures. Similar to microporous SAPO’s steamed Y-zeolites can be used for low temperature applications of heat transformation and thermal adsorption storage. © 2014The TheAuthors. Authors. Published by Elsevier © 2014 Published by Elsevier Ltd. Ltd. Selection andpeer peerreview review scientific conference committee SHCunder 2013responsibility under responsibility Selection and byby thethe scientific conference committee of SHCof2013 of PSE AGof PSE AG. Keywords: dealumination; water adsorption; zeolites;adsorption heat pump; thermal adsorption storage
1. Introduction In recent years new materials have been developed which are better adapted for applications in solar driven heat pumps or thermal adsorption storage processes. Materials such as silicoaluminophosphates (SAPO) or dealuminated
* Corresponding author. Tel.: +49-30-63922573; fax: +49-30-63922573. E-mail address: [email protected].
1876-6102 © 2014 The Authors. Published by Elsevier Ltd.
Selection and peer review by the scientific conference committee of SHC 2013 under responsibility of PSE AG doi:10.1016/j.egypro.2014.02.044
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
381
Y-type zeolites [1, 2, 3] have been suggested for thermal adsorption storage or adsorption heat pumps to be dependent upon low-temperature heat for charging. It is well known from the catalysis that a post-synthesis modification of zeolites by an easy to perform hydrothermal treatment [4] reduces the lattice aluminum concentration and improves the stability and catalytic performance. A partial dealumination of the zeolite Y by steaming reduces the hydrophilic character of the potential storage or heat transforming material as well and leads to a lower desorption temperature for water as found for the more expensive SAPO’s. The aim of this contribution is therefore to investigate in more detail the steaming process and its influence on the water adsorption properties with respect to optimized adsorption heat pumps and thermal adsorption storages. 2. Methods and materials The adsorption properties of the potential storage materials have been studied by different thermogravimetric methods (TG) on a Netzsch STA 409 apparatus as well as by gravimetric isotherm measurements using a McBainBakr quartz spring balance [5]. Dealuminated Y samples (DAY) were obtained by an optimized steam treatment at 1 bar water vapor pressure, well selected temperatures between 600 K to 1000 K and adjusted treatment time. The parent zeolite NaY with a framework Si/Al ratio of 2.7 was introduced into the active NH 4Y modification by a standard ion-exchange. The resulting framework Si/Al ratios were characterized by infrared spectroscopic measurements [6]. 3. Results and discussions Table 1 shows an overview of the chemical composition and adsorption capacity of the dealuminated samples, found after the modification process of the zeolite Y. For comparison the data of the parent NaY and a SAPO-34 are included. A moderate dealumination of up to Si/Al=3.2 does not reduce the adsorption capacity, which is comparable with that of SAPO-34. An increasing Si/Al-ratio, however, reduces the adsorption capacity, as found for higher desorption temperatures up to 250°C. A stronger dealumination is accompanied by partial losses of the zeolitic structure affecting the water adsorption capacity. Focusing on a lower desorption temperature, for instance 80°C as applied in the heat pump, the steaming process improves the desorption capability of the modified Y-type zeolites, as can be concluded from Figure 1. This figure shows the desorption profiles of the samples under discussion for an isothermal desorption interval at 80°C. Remarkable is the rising loss of water from the strong hydrophilic parent zeolite to the medium hydrophilic DY2. Table 1. Si/Al-ratio and water adsorption capacity of 48h in RH=33% conditioned samples, desorbed up to250°C. Sample
Si/Al
Adsorption capacity in (g/g)
SAPO-34
-
0,30
DY1
3,0
0,30
DY2
3,2
0,29
DY3
3,4
0,26
DY4
3,7
0,27
DY5
6,0
0,18
NaY
2,7
0,28
100
250
95
200
90
150
85
100
80
50
75
temperature in °C
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
mass decrease in %
382
0 0
50
100
150
time in min
NaY
SAPO34
DY1
DY2
DY5
temperature profil
Fig. 1. Thermogravimetric profiles (left hand Y-axis) of the parent NaY-zeolite, the partially dealuminated forms and the zeotype SAPO-34.
adsorbed amount in g/g
0,40
0,30
0,20
0,10
0,00 0,00001
0,0001
0,001
0,01
0,1
1
p/p0 NaY
DY2
SAPO34
Fig. 2 water isotherms of zeolite NaY and the dealuminated form of a Y-type zeolite are measured at T=298 K and the zeotype SAPO-34 is measured at T=293 K.
Despite the remaining difference of the desorption level that is accessible at 80°C between DY2 & SAPO-34, the desorption kinetics of DY2 seems to be better compared to SAPO-34, due to the steeper slope of the TG-curve at the
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
beginning. This is not surprising because of the significant differences in the window openings of the faujasite structure (about 0.7 nm) and the chabazite like window sizes of the SAPO-34 (approximately 0.4 nm). Finally the adsorption isotherms (Figure 2) of DY2 & SAPO-34 show a similar beneficial steep rise because of the dealumination of the Y zeolite. The Figure 2 gives also information about the position of the water isotherms of the dealuminated zeolite and the SAPO-34 compared with the parent NaY. As can be seen the DY2 isotherm is shifted towards the SAPO isotherm into the pressure interval between 0.01-0.3 mbar as the heat pump needs for low temperature application. 4. Conclusions The new optimized steaming process seems to be a powerful tool to adjust the hydrophilic character of Y-type zeolites to the special needs of low temperature driven heat pumps and thermal adsorption storages.
Acknowledgements We thank H. Toufar (Clariant, former Süd-Chemie Inc.) for supply of the SAPO-34. The financial support by the German Federal Ministry of Economics and Technology, grant number KF2014142AB2, is acknowledged. References [1] Kakiuchi H., Takewaki T. et al. (2002). Adsorption heat pump, and use of adsorption material as adsorption material for adsorption heat pump. 2002. European Patent Application, EP 1 363 085 A1. [2] Jänchen J, Ackermann D, Stach H.. Adsorption properties of aluminophosphate molecular sieves – potential applications for low temperature heat utilization. In: Wang, R.Z., Editor, SHPC 2002, Int. Sorp. Heat Pump Con., Shanghai, 2002; 635-638. [3] Jänchen J, Stach H, Hellwig U. Water sorption in faujasite- and chabazite type zeolites of varying lattice composition for heat storage applications. In: Gédéon A, Massiani P, F. Babonneau F, editors. Proceedings of 4th International FEZA Conference on Zeolites and Related Materials, 2-6 Sep 2008, Paris, France, Studies in Surface Science and Catalysis, Elsevier, 2008; 174: 599-602. [4] McDaniel, C.W.& Maher, P.K. New ultrastable form of faujasite. In: Molecular Sieves, Soc. Chem. Ind., London, 1968; 186-194.; [5] McBain JW, Bakr AM, A new sorption balance. J. Am. Chem. Soc., 1926, 48, 690. [6] C.H. Rüscher, J.-Chr. Buhl, W. Lutz, in: A. Galarneau, F. DiRenzo, F. Fajula, J. Vedrine (eds.), Stud. Surf. Sci. Cat., vol. 135, Elsevier, Amsterdam, 2001, pp. P13-P15, p.l.
383
ScienceDirect Energy Procedia 48 (2014) 380 – 383
SHC 2013, International Conference on Solar Heating and Cooling for Buildings and Industry September 23-25, 2013, Freiburg, Germany
Steamed zeolites for heat pump applications and solar driven thermal adsorption storage Thomas H. Herzoga, Jochen Jänchena, Eythymius M. Kontogeorgopoulosb, Wolfgang Lutzc* a
TH Wildau - Technical University of Applied Science,Bahnhofstraße 1,15745 Wildau,Germany b InvenSor GmbH, Gustav-Meyer-Allee 25,13355 Berlin, Germany c BTU – Brandenburg University of Technology, Volmerstraße 13, 12489 Berlin, Germany
Abstract The influence of the dealumination degree of NaY with respect to the water adsorption properties was investigated by infrared spectroscopy, thermogravimetry and isotherm measurements. The modification of the samples is a result of a steaming process at different temperatures in dependence of time. It was found that dealumination controls the hydrophilic behavior of NaY and contributes to defined low desorption temperatures. Similar to microporous SAPO’s steamed Y-zeolites can be used for low temperature applications of heat transformation and thermal adsorption storage. © 2014The TheAuthors. Authors. Published by Elsevier © 2014 Published by Elsevier Ltd. Ltd. Selection andpeer peerreview review scientific conference committee SHCunder 2013responsibility under responsibility Selection and byby thethe scientific conference committee of SHCof2013 of PSE AGof PSE AG. Keywords: dealumination; water adsorption; zeolites;adsorption heat pump; thermal adsorption storage
1. Introduction In recent years new materials have been developed which are better adapted for applications in solar driven heat pumps or thermal adsorption storage processes. Materials such as silicoaluminophosphates (SAPO) or dealuminated
* Corresponding author. Tel.: +49-30-63922573; fax: +49-30-63922573. E-mail address: [email protected].
1876-6102 © 2014 The Authors. Published by Elsevier Ltd.
Selection and peer review by the scientific conference committee of SHC 2013 under responsibility of PSE AG doi:10.1016/j.egypro.2014.02.044
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
381
Y-type zeolites [1, 2, 3] have been suggested for thermal adsorption storage or adsorption heat pumps to be dependent upon low-temperature heat for charging. It is well known from the catalysis that a post-synthesis modification of zeolites by an easy to perform hydrothermal treatment [4] reduces the lattice aluminum concentration and improves the stability and catalytic performance. A partial dealumination of the zeolite Y by steaming reduces the hydrophilic character of the potential storage or heat transforming material as well and leads to a lower desorption temperature for water as found for the more expensive SAPO’s. The aim of this contribution is therefore to investigate in more detail the steaming process and its influence on the water adsorption properties with respect to optimized adsorption heat pumps and thermal adsorption storages. 2. Methods and materials The adsorption properties of the potential storage materials have been studied by different thermogravimetric methods (TG) on a Netzsch STA 409 apparatus as well as by gravimetric isotherm measurements using a McBainBakr quartz spring balance [5]. Dealuminated Y samples (DAY) were obtained by an optimized steam treatment at 1 bar water vapor pressure, well selected temperatures between 600 K to 1000 K and adjusted treatment time. The parent zeolite NaY with a framework Si/Al ratio of 2.7 was introduced into the active NH 4Y modification by a standard ion-exchange. The resulting framework Si/Al ratios were characterized by infrared spectroscopic measurements [6]. 3. Results and discussions Table 1 shows an overview of the chemical composition and adsorption capacity of the dealuminated samples, found after the modification process of the zeolite Y. For comparison the data of the parent NaY and a SAPO-34 are included. A moderate dealumination of up to Si/Al=3.2 does not reduce the adsorption capacity, which is comparable with that of SAPO-34. An increasing Si/Al-ratio, however, reduces the adsorption capacity, as found for higher desorption temperatures up to 250°C. A stronger dealumination is accompanied by partial losses of the zeolitic structure affecting the water adsorption capacity. Focusing on a lower desorption temperature, for instance 80°C as applied in the heat pump, the steaming process improves the desorption capability of the modified Y-type zeolites, as can be concluded from Figure 1. This figure shows the desorption profiles of the samples under discussion for an isothermal desorption interval at 80°C. Remarkable is the rising loss of water from the strong hydrophilic parent zeolite to the medium hydrophilic DY2. Table 1. Si/Al-ratio and water adsorption capacity of 48h in RH=33% conditioned samples, desorbed up to250°C. Sample
Si/Al
Adsorption capacity in (g/g)
SAPO-34
-
0,30
DY1
3,0
0,30
DY2
3,2
0,29
DY3
3,4
0,26
DY4
3,7
0,27
DY5
6,0
0,18
NaY
2,7
0,28
100
250
95
200
90
150
85
100
80
50
75
temperature in °C
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
mass decrease in %
382
0 0
50
100
150
time in min
NaY
SAPO34
DY1
DY2
DY5
temperature profil
Fig. 1. Thermogravimetric profiles (left hand Y-axis) of the parent NaY-zeolite, the partially dealuminated forms and the zeotype SAPO-34.
adsorbed amount in g/g
0,40
0,30
0,20
0,10
0,00 0,00001
0,0001
0,001
0,01
0,1
1
p/p0 NaY
DY2
SAPO34
Fig. 2 water isotherms of zeolite NaY and the dealuminated form of a Y-type zeolite are measured at T=298 K and the zeotype SAPO-34 is measured at T=293 K.
Despite the remaining difference of the desorption level that is accessible at 80°C between DY2 & SAPO-34, the desorption kinetics of DY2 seems to be better compared to SAPO-34, due to the steeper slope of the TG-curve at the
Thomas H. Herzog et al. / Energy Procedia 48 (2014) 380 – 383
beginning. This is not surprising because of the significant differences in the window openings of the faujasite structure (about 0.7 nm) and the chabazite like window sizes of the SAPO-34 (approximately 0.4 nm). Finally the adsorption isotherms (Figure 2) of DY2 & SAPO-34 show a similar beneficial steep rise because of the dealumination of the Y zeolite. The Figure 2 gives also information about the position of the water isotherms of the dealuminated zeolite and the SAPO-34 compared with the parent NaY. As can be seen the DY2 isotherm is shifted towards the SAPO isotherm into the pressure interval between 0.01-0.3 mbar as the heat pump needs for low temperature application. 4. Conclusions The new optimized steaming process seems to be a powerful tool to adjust the hydrophilic character of Y-type zeolites to the special needs of low temperature driven heat pumps and thermal adsorption storages.
Acknowledgements We thank H. Toufar (Clariant, former Süd-Chemie Inc.) for supply of the SAPO-34. The financial support by the German Federal Ministry of Economics and Technology, grant number KF2014142AB2, is acknowledged. References [1] Kakiuchi H., Takewaki T. et al. (2002). Adsorption heat pump, and use of adsorption material as adsorption material for adsorption heat pump. 2002. European Patent Application, EP 1 363 085 A1. [2] Jänchen J, Ackermann D, Stach H.. Adsorption properties of aluminophosphate molecular sieves – potential applications for low temperature heat utilization. In: Wang, R.Z., Editor, SHPC 2002, Int. Sorp. Heat Pump Con., Shanghai, 2002; 635-638. [3] Jänchen J, Stach H, Hellwig U. Water sorption in faujasite- and chabazite type zeolites of varying lattice composition for heat storage applications. In: Gédéon A, Massiani P, F. Babonneau F, editors. Proceedings of 4th International FEZA Conference on Zeolites and Related Materials, 2-6 Sep 2008, Paris, France, Studies in Surface Science and Catalysis, Elsevier, 2008; 174: 599-602. [4] McDaniel, C.W.& Maher, P.K. New ultrastable form of faujasite. In: Molecular Sieves, Soc. Chem. Ind., London, 1968; 186-194.; [5] McBain JW, Bakr AM, A new sorption balance. J. Am. Chem. Soc., 1926, 48, 690. [6] C.H. Rüscher, J.-Chr. Buhl, W. Lutz, in: A. Galarneau, F. DiRenzo, F. Fajula, J. Vedrine (eds.), Stud. Surf. Sci. Cat., vol. 135, Elsevier, Amsterdam, 2001, pp. P13-P15, p.l.
383