Liquid Hydrogen Storage Materials

Anthony Burrell

Los Alamos National Laboratory

5/13/2011Project ID # ST040

This presentation does not contain any proprietary, confidential, or otherwise restricted information

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• Project start date: 1st Oct 2010• Project end date: 31st Sept 2011• Percent complete: 50%

• Total project funding– DOE share: $400

– Contractor share: $0

• Funding for FY11: $400

Timeline

Budget

• University of Pennsylvania• LANL

Partners

Overview

Barriers• Weight and Volume• Flow Rate• Energy Efficiency• Cost• Regeneration Process

Slide 3

Relevance - Objectives

• Develop liquid ammonia-borane (AB) fuels and increase rate and extent of hydrogen release– Liquid before and after hydrogen release– >10 Wt% H2

– Maximum liquid range for both fuel and product– Thermal stability at 50 C– Compatible with hydrazine regen– Low cost

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• Determine design criteria for Ionic Liquids as supports for ammonia– What cations are suitable?– What anions are suitable?– What is a suitable viscosity?– What is maximum liquid range?

• Assess compatibility of “fuel” with known ammonia borane regen process• Determine maximum ammonia borane mix in “fuel”• Determine kinetics for thermal release• Discover catalyst to improve cold start

Approach

Establish thermal stability limits for cations and anionsDSC, TGA, TGA-MS etc

Determine chemical compatibilities of cations and anions with ammonia boraneNMR, TGA, burette measurements

Liquid Properties of ionic liquid and ammonia borane : Ionic LiquidDSC, viscosity, etc

• Validated fluid-phase CH reactor• Designed, built, assembled, and validated modular fluid-phase CH system

test bed equipped with analytics• Reactors • Gas-liquid separator• Hydrogen purification

80 90 100 110 120 130 140 150 160 170 180 1900

15

30

45

60

75

90

105

120

135

150

Plot of Hydrogen Volumetirc Flow Rate as a function of Reactor Setpoint Temperature (oC) and Space Time (min)

H2 V

olum

etric

Flo

w Ra

te (m

L/m

in)

Temperature Setpoint (C)

tau =0.6 min tau = 1.04 min tau =2.78 min tau = 10.42 min

Collaboration with

No significant progress without strong interaction between materials and engineering

Summary – LANL and UPenn Down Selects for 2010 (AMR 2010)

Slide 6

Conclusion from AMR 2010

Ionic Liquid systems with catalysts look promising but need to tailor catalyst and ionic liquids combination - continued

AB Ionic Liquids

State of the art was Penn ionic liquids

Basic feature of BmimCl

• name: 1-Buthyl-3-methylimidazolium chloride

• chemical formula: C8H15CIN2

• density: 1.08 g/cm3

• heat capacity: 322-330 J/mol K

• molecular weight: 174.67

• decomposition: 250°C

• melting point: ~70°C

• glass transition: -76°C

• eutectic by mixing AB at RT (mixture at RT: liquid phase)

Structure of BmimCl

Collaboration HSECoE helped determine what properties of IL are most important for effective fuel.

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On-board System Configuration

Volume exchange tank design for storing fresh and spent fuel

Adiabatic vs. non-adiabatic dehydrogenation reactor

Buffer hydrogen tank

Heat transfer system (FCS HT and LT coolants)

Gas liquid separator (coalescing filter)

Startup reactor (electrical)

Spent Fuel

Recycle

GLS

AB/IL Fuel

Spent Fuel

LTC: Low Temperature CoolantHTC: High Temperature CoolantPLV: Pressure Letdown ValveGLS: Gas-Liquid Separator

Startup Reactor

To LT Radiator Dehydrogenation

Reactor

To HT Radiator

H2

H2

H2 Buffer Tank

GateValve

LTC

HTC

PLV

H2-LTHX

H2-HTHX

SAB-LTHX

SAB-HTHX

ANL analysis indicates on board system is possible

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Preliminary System Weight and Volume

Startup reactor, incremental W and V of FCS radiators to be included

W (kg) V (L)Fuel Tank (full, 5.6 kg H2 usable) 84.7 80.6H2 Buffer Tank (20 g H2 capacity at 20 atm) 2.0 15.2Dehydrogenation Reactor 5.0 1.1High Temperature H2 Cooler 1.6 2.1Low Temperature H2 Cooler 1.0 1.2High Temperature Recuperator 2.9 3.0Low Temperature Recuperator 0.9 0.8Pump 1.5 1.0Startup Heater 2.0 2.0Gas/Liquid Separator 1.0 1.0BOP Check Valves 0.6 0.2 Manual Valve 0.2 0.1 Excess Flow Valve 0.2 0.1 Service Vent Valve 0.2 0.1 Shutoff Valves 1.8 1.3 Relief Valves 0.6 0.2 Pressure Transducer 0.1 0.0 Temperature Transducer 0.1 0.0 Pressure Regulator 0.5 0.3 Pressure Relief Device 1.0 0.6 Pipings/Fittings 4.0 1.0 Fill System Control Module 1.0 1.0 Miscellaneous 2.0 0.5

System Total 114.9 113.1Gravimetric Capacity, wt% 4.9Volumetric Capacity, g H2/L 49.5

Weight Distribution

12%

6%

19%

63%

Medium

Tank

CDS

BOP

Volume Distribution

5%

3%

13%

79%

ANL analysis indicates reasonable initial Gravimetric capacity

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.002468

1012141618202224262830

2010 Target (4.5 H2 wt%)sys

2015 Target (5.5 H2 wt%)sys

Ultimate Target (7.5 H2 wt%)sys

Wt%

H2 o

f Med

ia

Hardware Mass Fraction ( )( )

( )( ) ( )

hardware hardware

total hardware media

Mass MassMass Mass Mass

= =+

Plot of the H2 wt% of Media versus the Hardware Mass Fraction Required to meet the DOE Gravimetric Target

materials that will never achieve DOE system targets

Requirements for fuel Based upon Engineering Analysis

Required:Liquid before and after hydrogen release>10 Wt% H2Maximum liquid rangeThermal stability at 50 CCompatible with hydrazine regenLow cost

Desirable: Compatible with stainless steelStable in airCatalytic hydrogen release demonstrated

Based upon HSECoE analysis at 50:50 materials : balance of plant balance require that materials have >10 Wt% hydrogen to meet 2015 targets (material independent)

Thermal stability of ionic liquids is a critical issue

Thermal stability of the ionic liquids we have looked at appears to be dominated by choice of cation

Isothermal TGA Plots of Ionic liquids under N2

Decomposition rates will help determine limits for reactor contact times. These are examples of poor performers

Ionic Liquids with Good Thermal Stability

We have identified IL’s that have good thermal stability

Low Temperature DSC used for determining phase changes in mixed IL:AB systems

-200 -100 0

-60

-30

0

30

60

-57°C

Heat

Flo

w (W

/mol

sam

ple)

Temperature (°C)

9°C

Freezing: 9°C, Melting: -57°C → strange?Unusual phase change behavior in mixed ionic liquid ammonia borane materials may have

impact on storage life and must be considered when choosing an IL

Hydrogen Release in IL system

0.0

0.5

1.0

1.5

2.0

2.5

0 1000.0

0.5

1.0

1.5

2.0

0 50 100 150

50°C 60°C 70°C 80°C 90°C 100°C 110°C

AB

Yiel

d (m

ol H

2/AB)

Time (min)

AB + BmimCl AB + BmimCl +Pt

Platinum catalysts no longer show the significant improvements in kinetics observed in organic solves. Therefore for ionic liquid systems initial reactor kinetics, in collaboration

with HSECoE, will involve simple thermal release

TGA-IR-RGA

50 100 15050 100 150

-60

-40

-20

0

-60

-40

-20

0

50 100 150-60

-40

-20

0

110°C

ABRGA

80°C

110°C

AB-BmimCl

Inte

nsity

(Arb

. uni

ts)

2 15 16 17 18 28 50

51 52 53 56 62 63 76 77 78 79 80 81

75°C

110°C

AB-BmimCl+Pt

48 49 50

RGA(zoom)

Temperature (°C)

TG

57%

31%

Wei

ght l

oss

(mas

s %

)30%

• main impurity: borazine• IL decreased impurities observed in gas phase and we believe catalysis will further improve hydrogen purity

IR

3500

1500

2500

500

3500

1500

2500

5003500

1500

2500

500

Wav

elen

gth

(cm

-1)

IR (3D)

borazine

Borazine

Borazine

Compatibility with hydrazine regen

Ionic liquid can produce impurities in some cases! Yet another down select requirement.

Impurity involves reaction of regen BH3with cation of IL

Mixing IL’s can change viscosity

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90 100

Viscosity (cP) vs. %EMIIm

31.7°C

Overall viscosity can be manipulated. Need to think about cost (mixed IL’s) versus pump requirements (balance of plant)

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– Catalyst development

– Identify materials with NO PHASE CHANGES in operating temperature region

– Determine the limits of Wt% H2 in an all liquid IL system?

Proposed Future Work

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Collaborations

– Cations have been identified that do not interfere with regeneration chemistry

– Anion selection rules understood

– No “volatile” solvents permitted

– Viscosity range (less than 2500 cP) determined in collaboration with

– Liquid systems testing underway

– Catalysts development ongoing

Mandatory Summary Slide