Quantifying hydrogen uptake by porous materials Nuno Bimbo - PowerPoint PPT Presentation

Quantifying hydrogen uptake by porous materials Nuno Bimbo Postdoctoral Research Officer Department of Chemical Engineering University of Bath N.M.M.Bimbo@bath.ac.uk http://www.bath.ac.uk/chem-eng/people/bimbo MH 2014 Summer School Salford, 17 th July 2014

Outline • Hydrogen storage in porous materials • Experimental measurements • Absolute and excess adsorption • Critical points in supercritical adsorption • Quantifying hydrogen in porous systems • A model for supercritical gas adsorption • Fitting experimental data to the model • Parameters – adsorbed density, pore volume • Hydrogen densities • Constant density of adsorbate • Adsorptive hydrogen storage • Compression vs adsorption • Optimal conditions for adsorptive storage • Adsorbed hydrogen as an energy store • Thermodynamics of adsorption • The isosteric enthalpies of adsorption • Clapeyron and Clausius-Clapeyron • The virial equation

Motivation The energy, food and water nexus Food Water 60 % increase by 55 % increase 2050 2050 (in comparison with 2005/7) Sustainability of elements Energy 40 % increase by 2035 UN FAO - World Agriculture towards 2030/2050 (2012) UN Water - World Water Development Report (2014) IEA - World Energy Outlook 2011 tce, October 2011 issue, IChemE

Hydrogen storage Alternative ways of storage include: Metal hydrides Cryogenic adsorption Chemical hydrides Liquefaction (at 20 K and 1 bar) Sodium alanate AX-21 Ammonia borane Compression (at 298 K and 350 or 700 bar) David, WIF. Faraday Discuss (2011) 151 , 399-414 (adapted from DOE 2011 Annual Merit Review – Storage)

Hydrogen storage Eberle et al. Angewandte Chemie International Edition (2009) 48 , 6608-6630

Hydrogen storage in porous materials • Storage in porous materials can increase its volumetric density at higher temperatures than liquefaction and lower pressures than compression • Synthetic chemistry of highly porous materials has known tremendous developments and new materials include metal-organic frameworks and porous polymers 16000 Topic: metal-organic frameworks 14000 12000 10000 8000 NU-100 (6,100 m 2 g -1 ) 6000 4000 2000 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Furukawa, Yaghi et al . Science (2010), 329 , 5990 Farha, Hupp et al . Nat Chem (2010), 2 , 944 Yuan, Zhou et al. Adv Mat (2011), 23 , 3723 PPN-4 (6,400 m 2 g -1 ) MOF-210 (6,240 m 2 g -1 ) ISI Web of Knowledge

Hydrogen storage in porous materials Experimental measurements High-pressure adsorption in a porous material Micromeritics ASAP 2020 – 0.1 MPa range (volumetric) Hiden IGA – 2 MPa range (gravimetric) 2.5 H 2 excess gravimetric uptake / wt.% 2.0 1.5 1.0 86.53 K 100.78 K 120.16 K 0.5 150.14 K 200.16 K 0.0 0 2 4 6 8 10 12 14 absolute pressure P / MPa Hiden HTP-1 – 20 MPa range (volumetric) MAST TE7 Carbon beads H 2 isotherms in the 86 to 200 K range, up to 14 MPa

Hydrogen storage in porous materials Absolute and excess adsorption In a supercritical fluid, this difference is negligible at low pressures but becomes very significant with increasing pressures Experimental sorption techniques (volumetric and gravimetric) can only account for excess adsorption Because adsorptive storage of hydrogen will most likely occur above the critical temperature and at high pressures, understanding and quantifying absolute adsorption is critical

Hydrogen storage in porous materials Critical points in supercritical adsorption Critical points in high-pressure, supercritical adsorption max max max 0 n , n , P , P a e e e Absolute quantity is the excess quantity plus the bulk quantity in the potential field of the adsorbent   n n n a e b      n n V a e b a Excess reaches a maximum and then starts to decrease with increasing density in the bulk, until eventually reaching zero       0 b a P P e When the excess reaches a maximum, the gradient of the absolute adsorbed quantity is equal to the gradient of the bulk quantity       n n  P  max  a   b  when P e       P P T T Bimbo et al . Faraday Discussions (2011) 151 , 59

Hydrogen storage in porous materials Ideal vs real gas • Data for real gas equation taken from NIST database • Based on Leachman’s Equation of state for normal hydrogen Leachman et al . J Phys Chem Ref Data (2009) 38

Hydrogen storage in porous materials Ideal vs real gas   1 P   P , T H 2 Z RT   2 1 A P A P  1 2 Z ( P )   2 1 A P A P 3 4 • Leachman’s EOS is a complex equation • A rational fit at different temperatures is done to obtain the densities at different pressures

Quantifying hydrogen in porous materials A model for supercritical gas adsorption   n n n e a b n  max  n Absolute a a   n V Amount in bulk p b b 1 P 1 P    Density   b 2 1 A P A P Z RT RT 1 2   2 1 A P A P 3 4 max 1 P     max n n V    e p n n V b a e a p Z RT

Quantifying hydrogen in porous materials A model for supercritical adsorption max   n n a a T ó th (2) Langmuir (1) Jovanović -Freundlich (3) (1) Determined from fitting Sips (4) UNILAN (5) bP   1 IUPAC Type I equations ( θ ) Dubinin-Astakhov (6)  bP Each has different parameters Dubinin-Radushkevich (7) (2) (4) (3) bP     c c  bP ( bP ) 1      1 e   c      c  c 1 bP 1 bP     (7) (6) m   2   (5)   RT   RT   m     2              1 1 bP exp( c ) T P   P T           E E 0 ln     0 E E     e ln       e ln   2 c 1 bP exp( c ) P   P   Myers and Monson. Langmuir (2002) 18 , 10261; Leachman et al . J. Phys. Chem. Ref. Data (2009) 38 , 721; Langmuir. J Am Chem Soc (1918) 40 , 1361; Sips. J Chem Phys (1948) 16 , 490; Tóth, Acta Chim Acad Sci Hung (1962) 32 , 39; Honig and Reyerson, J Phys Chem (1952) 56 , 140; Quiñones and Guiochon, J Colloid Interface Sci (1996) 183 , 57; Dubinin and Astakhov, Izv Akad Nauk SSSR, Ser Khim (1971), 5 , 11; Dubinin and Astakhov, Russ Chem Bull (1971) 20 , 8; Bimbo et al . Faraday Discuss (2011) 151 , 59

Quantifying hydrogen in porous materials A model for supercritical adsorption max  1 P Non-linear fitting   n n V e a a Z RT n a   max n a 3.5 3.5 H 2 excess gravimetric uptake / wt.% H 2 excess gravimetric uptake / wt.% 3.0 3.0 2.5 2.5 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 absolute pressure P / MPa absolute pressure P / MPa Hydrogen Isotherm for MAST TE-7 carbon beads at 86 K Hydrogen Isotherms for MAST TE-7 carbon beads at 86 K Excess fitted with the T ó th equation Excess and absolute using the T ó th equation n , P Experimental points (dependent and independent variable, respectively) e max n , V Variable parameters (determined from the fitting) a a

Quantifying hydrogen in porous materials Fitting experimental data to the model Activated carbon TE7 Materials BET Surface Skeletal Micropore area density volume (m 2 g -1 ) (g cm -3 ) (cm 3 g -1 ) MAST TE7 810 1.94 0.43 carbon beads AX-21 2258 2.23 1.03* MIL-101 2886 1.69 1.51** Metal-organic framework MIL-101 Activated carbon AX-21 *Quirke and Tennison, Carbon (1996), 34, 1281-1286 **Streppel and Hirscher. Phys Chem Chem Phys (2011) 13 , 3220-3222

Quantifying hydrogen in porous materials Fitting experimental data to the model TE7 fitted with the Sips equation TE7 fitted with the UNILAN equation TE7 fitted with the Dubinin-Astakhov equation TE7 fitted with the Jovanović -Freundlich TE7 fitted with the Dubinin-Radushkevich TE7 fitted with the Tóth equation equation equation

Quantifying hydrogen in porous materials Parameters – TE7

Quantifying hydrogen in porous materials Parameters – AX-21

Quantifying hydrogen in porous materials Parameters – MIL-101

Quantifying hydrogen in porous materials Fitting experimental data to the model 4.0 H 2 excess gravimetric uptake / wt.% 3.5 3.0 Tóth Sips Langmuir 2.5 Jovanovic-Freundlich UNILAN Dubinin-Radushkevich Dubinin-Astakhov 2.0 0 10 20 30 40 absolute pressure P / MPa MAST TE7 carbon beads – extrapolation to higher pressures using the parameters from the multi-fit of different Type I isotherms at 100 K

Quantifying hydrogen in porous materials Verifying the model - NMR PEEK Carbons at 100 K 6 2 g -1 CO 2 -9-1 - 542 m 5 2 g -1 CO 2 -9-26 - 1027 m gravimetric uptake / wt.% 2 g -1 CO 2 -9-59 - 1986 m 4 2 g -1 CO 2 -9-80 - 3103 m 2 g -1 Steam-9-20 - 1294 m 3 2 g -1 Steam-9-35 - 981 m 2 g -1 Steam-9-70 - 1956 m 2 1 0 0 2 4 6 8 10 Anderson et al . J Am Chem Soc (2010) 132 , 8618 absolute pressure P / MPa