Molecular Hydrogen Storage in Novel Binary Clathrate Hydrates at - - PowerPoint PPT Presentation

Molecular Hydrogen Storage in Novel Binary Clathrate Hydrates at Near-Ambient Temperatures and Pressures

Colorado School of Mines Center for Hydrate Research Golden, CO

L.J. Rovetto, T.A. Strobel, K.C. Hester, S.F. Dec, C.A. Koh, K.T. Miller, E.D. Sloan 2006 DOE H2 Program Review May 16 -19th, 2006

Agenda

Introduction & Motivation H2/THF Binary Hydrate Measurements H2/Cyclohexanone Binary Hydrate Measurements H2 Storage in Semi-Clathrate Materials Hydrotropes Effect on H2 Hydrate Formation Future Work

Accomplishments

H2 hydrate pressure reduced by 2 orders of magnitude with THF

H2 is enclathrated in sII hydrate

Storage capacity confirmed

Up to one H2 per 512 of sII binary clathrate H2 storage independent of xTHF (at tested conditions)

Accomplishments

H2 can stabilize a hydrate structure

• therwise unstable

H2/cyclohexanone hydrate

First semi-clathrate formed with H2 No thermo promotion from hydrotropes

INTRODUCTION & MOTIVATION

What are Clathrate Hydrates…?

sH sI sII

512 51262 51264 51268 435663 512 512

2/cell 6/cell 16/cell 8/cell 3/cell 2/cell 1/cell

46 H2O 136 H2O 34 H2O

+ +

+

Cubic Cubic Hexagonal

Molecular Sizes and Hydrate Structures

512, 51262 [sI] 51262 [sI] 51264 [sII] 51268 [sH]

435663 [sH] 512 [sII, sH] 4 Å 5 Å 6 Å 7 Å 8 Å 4 Å 5 Å 6 Å 7 Å 8 Å

N2 O2 CH4 CO2 C2H6 CF4

O

C3H8 O O

CH3 O 3 Å

Ne Kr

512, 51264 [sII]

Ar Xe He H2

Diameter

Gas Clathrate Hydrates

Encapsulate small gas molecules (CH4, C2H6, etc.)

Cause of pipeline blockage in natural gas/oil production Potential future energy source (CH4)

Concentrate large volume of gas sII ~170 m3 of gas (STP) per m3 of hydrate

H2 in Hydrates

’83 – Holder et al.: H2 Rich Gases

H2 too small to contribute to hydrate stability

’84 – Ng & Robinson: < 40% H2 in gas

predicted H2 enters the hydrate structure

’99 – Dyadin: H2 and noble gases

experimental hydrate decomposition P = 100-360 MPa

’00 – Guo et al.: H2 and gas mixtures

Assumes H2 to be a hydrate non former

Clathrate Hydrates Can Store H2

2002 - Mao W. et al.: Pure H2 hydrate

P=200 MPa T=280 K

5.0 wt% ~ 460 m3gas(STP)/m3

2 H2 512 4 H2 51264

Potential storage medium for hydrogen

H2O only by-product H2 is not bonded to the hydrate structure No need of chemical reaction for gas release Complete reversible Fast Kinetics (formation and decomposition) Extreme formation pressures

. Science 2002, 297, 2247.

THF/H2 Hydrate Stable at Much Lower P than Pure H2 Hydrate

P=6 MPa T=280 K

1.0 wt% ~ 115 m3gas(STP)/m3 Science 2004, 306, 469.

2004 - Florusse L. et al.: Binary THF-H2 hydrate

1 H2 512 1 THF 51264

Pressure reduction 2 orders of magnitude

1 10 100 1000 270 275 280 285 290 295 300

Pressure (MPa) Temperature (K) H2/THF Hydrates Stable

Pure H2

Hydrates Melt

Pure THF H2/THF

Scientific Impact

Discrepancy on cage occupancy

1 2 3 4 M a

• ,

W . L . ( 2 2 ) P a t c h k

• v

s k i i , S . ( 2 3 ) L

• k

s h i n , K . A . ( 2 4 ) S l u i t e r , M . H . ( 2 5 ) A l a v i , S . ( 2 5 ) L e e , H . ( 2 5 ) Binary H2/THF hydrate (SMALL) Pure H2 hydrate Binary H2/THF hydrate (LARGE)

BINARY CLATHRATE HYDRATE RESULTS

Gas Release Measurements Confirms H2 Storage in Hydrates

1 wt.% H2 in binary hydrate THF/H2

0.0 0.2 0.4 0.6 0.8 1.0 1.2 10 20 30 40 50 60

Initial Formation Pressure (MPa) wt% Hydrogen

Crushed THF Hydrate 45 microns Crushed THF Hydrate 250 microns NMR

0.0 0.2 0.4 0.6 0.8 1.0 100 200 300 400 500 Hydrogen Fugacity (MPa) Fractional Occupancy of H2 in 512 Cage

Crushed THF Hydrate 45 microns Crushed THF Hydrate 250 microns Udachin (1994) Best Fit Langmuir Isotherm

1 H2 / 512cage

Strobel et al. J. Phys. Chem. B (Submitted)

THF THF H H H H H

f C f C f C

small small small Small

+ + =

2 2 2 2 2

1 θ

High Resolution Neutron Diffraction Confirms Single Occupancy of 512 Cages

Normalized Intensity 1a THF-d8 sII hydrate D-spacing ( Å) D- 1b D2 + THF-d8 sII hydrate

2

wRp=0.031, χ2=6.212 wRp=0.035, χ2=3.6 Hester et al. Phys. Rev. Lett. (Submitted)

Guest Occupancies D2 512 (Spherical harmonics) – 1.003 ±.02 D2 512 (Single atom) – 0.998 ± 0.02 THF 51264 - unity

Formed at 70 MPa Measured at 0.1 MPa and 20 K

Manipulation of Cavity Occupancy

Can H2 storage be increased by decreasing concentration of THF? Can large cage THF occupancy be substituted for multiple H2 molecules?

All large cages filled with THF Some large cages filled with THF, balance filled with 4 H2

H2 Storage is Independent of xTHF

Gas release measurements

0.0 0.1 0.2 0.3 0.4 0.5 0.01 0.02 0.03 0.04 0.05 0.06 mole fraction THF wt% H2 in Hydrate 13.8 MPa T cycled 265-270 K One week

Strobel et al. J. Phys. Chem. B (Submitted)

THF remains favorable guest in large cage H2 only occupies small cages

No known pure CHone hydrate

Requires a second guest, cf. cyclohexane, benzene

Neutron diffraction studies on the binary Cyclohexanone-H2 hydrate

Confirm structure (sII or sH?) Hydrogen occupancy

Cyclohexanone - Another Promoter Molecule

O

Neutron Diffraction Confirms CHone-H2 sII hydrate Structure & Occupancy

wRp=0.0536, χ2=4.566

Guest Occupancies

D2 512 (Single atom) – 0.54

CHone 51264 - unity

Formed at 70 MPa Measured at 0.1 MPa and 20 K

Implication of H2 Stabilization Effect

H2 shown to stabilize sII lattice (otherwise unstable) Implication of hydrogen stabilizing other lattices that require a second guest, e.g. sH

+ Promoter +H2

51268 435663 512 3/cell 2/cell 1/cell 34 H2O

+ + Higher storage capacity

TBAB-H2O Phase Diagram and Structure

1TBAB:38 H2O Empty small cages available for H2

TBAB-B semiclathrate – orthorhombic

4X.6Y.4Z X=51262, Y=512, Z=51263

Tetra-n-butylammonium bromide

Shimada et al., Acta Cryst. (2005),C61, 65-66 Lipowski et al., J Supramol. Chem., (2002), 2, 435-439

The First Semiclathrate H2 Hydrate Discovered

0.000 0.100 0.200 0.300 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

mole% TBAB wt% H 2 in Hydrate

13.8 MPa 6.3°C 1 day Preformed crushed hydrate – 250 μm, pressurized to 13.8 MPa w/ H2

Gas release measurements for different hydration numbers

H2 storage is NOT limited to the classical hydrate structures Wide variety of inclusion compounds for H2 storage

Accomplishments

H2 hydrate pressure reduced by 2 orders of magnitude with THF

H2 is enclathrated in sII hydrate

Storage capacity confirmed

Up to one H2 per 512 of sII binary clathrate H2 storage independent of xTHF (at tested conditions)

Accomplishments

H2 can stabilize a hydrate structure

• therwise unstable

H2/cyclohexanone hydrate

First semi-clathrate formed with H2 No thermo promotion from hydrotropes

Publications

• T.A. Strobel, C.J. Taylor, K.C. Hester, S.F. Dec, C.A. Koh, K.T. Miller, E.D.

Sloan Jr. Molecular Hydrogen Storage in Binary THF-H2 Clathrate

• Hydrates. J. Phys. Chem. B. Accepted
• K.C. Hester, T.A. Strobel, A. Huq, A.J. Schultz, E.D. Sloan, C.A. Koh.

Molecular Hydrogen Occupancy in Binary THF-H2 Clathrate Hydrates by High Resolution Neutron Diffraction. Phys. Rev. Letters. Submitted

• L.J. Rovetto, T.A. Strobel, C.A. Koh, E.D. Sloan Jr. Is gas hydrate

formation thermodynamically promoted by hydrotrope molecules? Fluid Phase Equilibria. Submitted

• Neutron

diffraction studies

• f

binary hydrates with H2 and

• cyclohexanone. In preparation
• Hydrogen storage in semiclathrates

with Tetra-n-butylammonium

• bromide. In preparation

Future Work…

High Pressure Raman facility

Pure H2 Hydrate

Formation and dissociation mechanism Occupancy dependence on pressure

Search for new promoters

sII and sH gas hydrates Other structures

Self Preservation Studies

Slow dissociation rates of hydrates outside the stability region

Acknowledgements

Ashfia Huq Arthur Shultz Jim Richardson

Questions? / Comments

Extra Slides

Overview

Timeline

9/1/05 - 8/31/08 20 % Complete

Budget

Funding received 9/05

$ 250,000

3 years

Interactions /Collaborations

Technical University of Delft Argonne National Laboratory

IPNS

Work and Facilities

Our Approach to Study H2 Hydrates

Microscopic

NMR Raman

60,000 psi

Neutron diffraction

Macroscopic

Gas evolution Phase equilibria HP cell

Modeling

In house model

H+L+V H+I+V

Stability of Gas Hydrates

Additives as Inhibitors or Promoters

Additives May Shift Stability To Higher Temperatures

Hydrates stable Temperature Pressure

Additives Reduce Required Pressure Additives May Shift Stability To Lower Temperatures

Binary THF/H2 Hydrate Confirmed Using Spectroscopy

H2 shown to occupy sII hydrate cages

15 10 5

• 5 -10

ppm Raman Spectroscopy 1H MAS NMR Spectroscopy

H2 is enclathrated

THF-d8 / D2O THF-d8 / D2O / H2

Florusse, L. J. et al, Science 2004, 306, 469.

Scientific Impact

Discrepancy on cage occupancy

Mao, W. L.; Science 2002, 297, p 2247 5.0 wt % Raman

• bservations and

phase volume ratio ~2k bar 234 K Pure H2 Hydrate 2 H2/small 4 H2/large cage Patchkovskii, S. et al, PNAS 2003, 100, p 14645 DFT calculations Neutron scattering Sluiter, M.H., et.at. Materials Transactions, 2004, pp 1452 AB initio calculations Pure H2 Hydrate 2 H2/small 4 H2/large cage Alavi, S., et.al. J.Chem.Phys, 2005, 123, p 024507 Molecular dynamic calculations 2.5k bar 100 K Pure H2 Hydrate 1 H2/small 4 H2/large cage Alavi, S., et.al. J.Chem.Phys, 2005, 124, p 014704 Molecular dynamic calculations 120 bar 273 K THF/H2 Hydrate Similar Energy for 1 or 2 H2/small Lee,H. and Ripmeester, J. et.al, Nature, 2005, 434, p 743 > 4 wt % Raman, NMR, gas evolution 120 bar 270 K THF/H2 Hydrate 2 H2/small Decreased THF -> 4 H2 in some large cages Pure H2 Hydrate 2 H2/small cage 3.96 H2/ large cage Lokshin, K. A. et al,

• Phys. Rev. Lett, 2004, p 125503

3.8 wt % 2k bar 250 K Pure H2 Hydrate 1 H2/small 2- 4 H2/large cage 2k bar 180 K

Hydrotropes and Gas Hydrates

P-TSA (para-Toluene Sulfonic Acid)

2

ln( )

T P L w w w w w T

H V dT dP a RT RT RT RT μ μ Δ Δ Δ Δ = − + −

∫ ∫

Increase water activity through self aggregation

Natural Gas Mixture Gnanendran et al., FPE, (2004), 221, 175-187

Apply to pure H2 hydrate Reduce formation pressure w/o compromising storage ?

Reported to promote hydrate equilibrium

Hydrotropes Do Not Promote Gas Hydrate Formation

3 4 5 6 7 275 276 277 278 279 280 281 282

Temperature [K] Pressure [MPa]

pure CH4 Hydrate-Sloan 1998 CH4+p-TSA 2000ppm CH4+p-TSA 4000ppm CH4+p-TSA 62000ppm* CH4+p-TSA 138000ppm

Methane Natural gas mixture

1 2 3 4 5 6 7 8 9 282 284 286 288 290 292 294 Temperature [K] Pressure [MPa] natural gas mixture-Jager 2001 natural gas mixture-this w ork natural gas mixture+5000ppm p-TSA

Rovetto et al. Fluid Phase Eq. (Submitted)

No thermodynamic promotion with hydrotropes No feasibility for H2 hydrate