Zeolite Framework Materials for Hydrogen Storage

Transcription

1 Zeolite Framework Materials for Hydrogen Storage Paul Anderson School of Chemistry The University of Birmingham

2 Zeolites aluminosilicates composed of cornersharing TO 4 tetrahedra Key: Silicon/ Aluminium Oxygen 4-ring (S4R) 6-ring (S6R)

3 Zeolites aluminosilicates composed of cornersharing TO 4 tetrahedra sodalite cage (β-cage)

4 Zeolites aluminosilicates composed of cornersharing TO 4 tetrahedra now possible to incorporate over one third of the elements of the periodic table into zeolite-like frameworks Sodalite (SOD structure type) Zeolite A (LTA) Zeolites X & Y (FAU)

5 Exchangeable cations general formula: Mx/n [(AlO2)x (SiO2)y].m H2O + = sodium zeolite A (Na-A) Zeolite Framework Materials for Hydrogen Storage Paul Anderson, H2

6 Zeolite uses Zeolites have found many important industrial uses including: Shape and size selective catalysis Cracking of hydrocarbons Ion exchange Zeolites have also been used in double glazing animal feed - pigs, hens and humans (coffee mate) also being marketed as alcohol adsorbents, foot odour destroyers and cat litter. Zeolite Framework Materials for Hydrogen Storage

7 Why zeolites for hydrogen storage? specific surface area up to 910m 2 g -1 crystalline solids well defined pores well defined adsorption sites ease of characterization ease of chemical modification low cost chemical stability not flammable in air not flammable in hydrogen Zeolite Framework Materials for Hydrogen Storage

8 Previous work on hydrogen in zeolites three temperature regimes low temperature 1.2 wt% for Na-X at 77K, 0.6 bar [Kazansky et al. Microporous and Mesoporous Materials 22, (1998).] room temperature 1.2 wt% for Na-A at 700 bar [Darkrim et al. Journal of Chemical Physics 112 (13), (2000).] high temperature 0.6 wt % for Cs-A at 300 C, 917 bar [Fraenkel & Shabtai, Journal of the American Chemical Society 99, (1977).] Zeolite Framework Materials for Hydrogen Storage

9 Systematic study four different zeolites: X, Y, A & Rho three different structure types: FAU, LTA & RHO three different Si/Al ratios: ~1, 2.4, K The Periodic Table of the Elements Zeolite Framework Materials for Hydrogen Storage

10 Zeolite X FAU structure type Si/Al = 1.2 Zeolite Framework Materials for Hydrogen Storage

11 Zeolite X 2.5 Hydrogen adsorption (wt.%) LiX ad s o rp t io n LiX desorption MgX adsorption MgX desorption AgX adsorption AgX desorption KX ad s o rp t io n KX d es o rp t io n Pressure (bar)

12 Zeolite X 2.5 Hydrogen adsorption (wt.%) R 2 = 0.8 AgX NiX SrX RbX CdX CsX CaX KX NaX MgX CoX ZnX LiX BET surface area (m 2 /g)

13 Zeolite Y also FAU structure type Si/Al = % fewer cations Zeolite Framework Materials for Hydrogen Storage

14 Zeolite Y 2 Hydrogen adsorption (wt.%) LiY KY CsY NaY RbY Pressure (bar) Zeolite Framework Materials for Hydrogen Storage

15 Zeolite Y 2.4 Hydrogen adsorption (wt.%) R 2 = CsY CrY BaY AgY MgY SrY NiY KY CaY NaY RbY ZnY CoY CuY CdY LiY BET surface area (m 2 /g)

16 Zeolites X & Y Cation Expected H 2 uptake (± 0.05 wt.%) X Expected H 2 uptake (± 0.05 wt.%) Li Na K Rb Cs Mg Ca Sr Co Ni Zn Ag Cd Y

17 Zeolites X & Y Cation Expected H 2 uptake (± 0.05 wt.%) X Observed H 2 uptake (± 0.05 wt.%) Expected H 2 uptake (± 0.05 wt.%) Y Observed H 2 uptake (± 0.05 wt.%) Li Na K Rb Cs Mg Ca Sr Co Ni Zn Ag Cd

18 Zeolites X & Y H 2 uptake (± 0.05 wt.%) H 2 uptake (molecules/unit cell) Cation X Y X Y Li Na K Rb Cs Mg Ca Sr Co Ni Zn Ag Cd

19 Zeolite A LTA structure type Si/Al = 1.0 Zeolite Framework Materials for Hydrogen Storage

20 Zeolite A Hydrogen adsorption (wt.%) MgA a dsorprt ion MgA desorption ZnA a dsorpt ion ZnA de sorpt ion CoA adsorption CoA desorption CaA adsorption CaA desorption Pressure (bar)

21 Zeolite A 2 Hydrogen adsorption (wt.%) LiA NaA KA RbA CsA Pressure (bar)

22 Zeolite A 1.8 Hydrogen adsorption (wt.%) % 9.4% 11.5% 12.5% 14.6% Pressure (bar)

23 Zeolite A Hydrogen adsorption (wt.%) AgA NaA HA R 2 = LiA KA RbA CsA CdA SrA NiA MgA CoA CaA ZnA BET surface area (m 2 /g)

24 Zeolite Rho RHO structure type Si/Al = 3.0 Zeolite Framework Materials for Hydrogen Storage

25 Zeolite Rho Hydrogen adsorption (wt.%) CoRho NiRho CuRho ZnRho AgRho CdRho (2) CdRho (1) NaCsRho Pressure (bar)

26 Zeolite Rho 2 Hydrogen adsorption (wt.%) ZnRho CuRho CoRho BaRho HRho NiRho AgRho LiRho CdRho (2) NaRho NaCsRho KRho RbRho CaRho SrRho CdRho (1) MgRho BET surface area (m 2 /g)

27 Langmuir model p n = 1 n b + p m n m n is the specific amount of gas adsorbed at equilibrium pressure p n m is the monolayer capacity b is the adsorption coefficient Pressure / weight percent H 2 (bar/wt.%) BaRho (R-squared =0.9995) MgRho (R-squared = ) NiRho (R-squared = ) HRho (R-squared = ) Pressure (bar)

28 Langmuir model Zeolite Measured H 2 uptake (± 0.05 wt.%) n m (± 0.01 wt.%) b (bar -1 ) LiX ± 0.05 NaX ± 0.38 CaX ± 0.04 CoX ± 0.07 ZnX ± 0.02 KY ± 0.26 RbY ± 0.09 SrY ± 0.08 NiY ± 0.04 NaA ± 0.15 CaA ± 0.10 CoA ± 0.05 AgA ± 0.23 CdA ± 0.20 MgRho ± 0.09 NiRho ± 0.05 HRho ± 0.09

29 Langmuir model SA LAN = nm N Aσ RMM n m is the monolayer capacity N A is Avogadro s number σ is the area occupied by a hydrogen molecule on the surface RMM is the relative molecular mass of hydrogen (H 2 ) Zeolite SA LAN from H 2 uptake (m 2 /g) SA BET from N 2 uptake (m 2 /g) LiX NaX CaX CoX ZnX KY RbY SrY NiY NaA 576 CaA CoA AgA 612 CdA MgRho NiRho HRho

30 Comparison with activated carbons Hydrogen adsorption (wt.%) Zeolite X Zeolite Y Zeolite A Zeolite Rho Carbo n materials BET surface area (m 2 /g) Zeolite Framework Materials for Hydrogen Storage

31 Comparison with activated carbons 4 wt.% H 2 per 1000 m 2 /g material

32 Comparison with activated carbons 35 Volumetric hydrogen storage capacity (kgh 2 /m 3 )

33 Possible advantages of zeolites in stationary hydrogen stores low cost lower gravimetric but higher volumetric capacity than carbon not flammable in air or in H 2 chemically tunable to trap hydrogen at room temperature and above?

34 Acknowledgments EU FP5 FUCHSIA Project The Carbon Trust EPSRC UK SHEC Henrietta Langmi Ian Gameson, Rex Harris, John Speight, David Book, Allan Walton, Malek Al-Mamouri Peter Edwards