# Presentation: 122322

## An Overview of Chemical HydridesORNL Hydrogen Storage WorkshopMay 7-8, 2003

- Brian D. James
- Directed Technologies Inc.
- 3601 Wilson Blvd., Suite 650
- Arlington, VA 22201
- (703) 243-3383
- Brian_James@DirectedTechnologies.com

## Presentation Outline

- Overview
- Technical Targets for FCV’s
- Challenges
- Science & Chemistry
- What are Chemical Hydrides?
- Some Examples
- Conclusions

## Short List of Desirable Attributes

- Weight: High System H2 Mass Fraction (>=10%)
- Volume: High Volumetric Density
- Cost: Low Cost H2  **(<$1000 capital cost,**** ****<= $1.50/kg)**
- Low Operating Temperature
- Pure H2 evolution (no diluents/FC poisons)
- Safe Storage/Handling/Non-Pyrophoric
- Liquid (for ease of metering & handling)
- Complete, vigorous reaction (but not explosive)
- Easily handled waste products

## Fuel Cell

- Reformate
- (H2+ Diluent Gases)

- Pure H2
- (including water vapor)

- ATR

- POX/
- CPOX

- SMR

- Thermal
- Decomposition

- Carbon
- Storage

- Metal
- Hydrides

- Chemical
- Hydrides

- Compr.
- Gas

- Thermal
- Decomposition

- Water
- Reaction

**Hydrogen Production Pathways**

- Hydrocarbon
- (Diesel,gasoline,propane, methanol, ethanol)

- (Ammonia)

## What defines a Chemical Hydride?

- For our purposes, a chemical hydride is any compound which reacts with water to evolve hydrogen
- A few examples:
- Millenium Cell Sodium Borohydride
- Powerball
- Iron Reduction
- Aluminum Reduction
- But there are actually many possibilities...

## Chemical Hydride Options

## Chemical Hydride Options, continued

## Chemical Hydride Options, continued

## Chemical Hydride Options, continued

_**Chemical Hydride Options, continued**_

## Millennium Cell’s Sodium Borohydride

- The *Hydrogen On Demand **TM* System

-  NaBH4 “fuel” is a room temperature, 1 atm liquid
-  Waste product is a warm solution
-  Resulting H2 is pure and at 100% relative humidity

- On-board Reaction:

- ~30% NaBH4 solution water, stabilized with ~1-3% NaOH

- Borax waste product stays dissolved in water

- Proprietary catalyst achieves instantaneous hydrogen production

**NaBH****4****     +   2 H****2****O        ********               NaBO****2****     +        4 H****2    ****+        300kJ**** **

- Pure humidified H2 delivered to Fuel Cell

- Exothermic Reaction      Energy

## Millennium Cell’s Sodium Borohydride

- Borohydride in Water

- H2 Gas

- Borax In Water

*Hydrogen On Demand **TM* Catalyst System

- Pump

**On-board Components**

**Off-board Borax Regeneration**

- Heat Rejection

- Chrysler Natrium Fuel Cell Vehicle, 2001, 300 mile range

| Theoretical H2 Wt % | 21% (hydride alone)
6.3% (hydride @ 30% slurry) |
| --- | --- |
| System H2 Wt % 
(@ 30% slurry) | ~4-5% |
| Onboard System Cost | <$1000 |
| System Vol. Density | 35-45 kg H2/m3 |

## Millennium Cell: Key Elements- OnBoard

-  5-30% w.w. water solution of sodium borohydride (but also considering lithium borohydride, potassium borohydride, ammonium borohydride, tetramethyl ammonium borohydride, and mixtures thereof)
-   Stabilizing agent typically 1-3% sodium hydroxide (but also considering lithium hydroxide, potassium hydroxide, sodium sulfide, thiourea, carbon disulfide, sodium zincate, sodium gallate, and mixtures thereof)
-  Transition metal catalyst typically Ru/Ni (but also considering iron, cobalt, copper, manganese, rhodium, rhenium, platinum, palladium, chromium, silver, osmium, iridium, borides thereof alloys thereof, and mixtures thereof)

_**Millennium Cell: Key Elements- OnBoard**_
**(From Patent No. 6,534,033)**

## Millennium Cell: Key Elements- OffBoard

**(From Patent No. ****6,524,542**** ****)**

**3 NaBO****2**** +  6 C +  6 H****2****O ********  3 NaBH****4****  +  6 CO****2****     Net Reaction**

**	****4NaBO****2**** + 4CO****2**** + 2H****2****O ******** 4NaHC + 2B****2****O****3****       -126 BTU****	**** (-133 kJ) **
**	****	****4NaHCO****3****  ********  2Na****2****O + 4CO****2**** + 2H****2****O     2254 BTU (2378 kJ) **
**	****	****  ****12HBr      ********   6H****2**** + 6Br****2**** ****	****           2476 BTU (2612 kJ)**
** ****	****2B****2****O****3**** + 6C + 6Br****2****  ********  4BBr****3**** + 6CO ****	****           2285 BTU (2411 kJ) **
**	****        ****6CO + 6H****2****O    ********  6H****2**** + 6CO****2****                      -571 BTU (-602 kJ)**
** ****	****         ****4BBr****3**** +12H****2****   ********  2B****2****H****6**** + 12HBr                 1746 BTU (1842 kJ)**
** ****	****     ****2Na****2****O + 2B****2****H****6****   ********  3NaBH****4**** + NaBO****2****            -2730 BTU (-2880 kJ)**
**           ****3NaBO****2**** + 6C + 6H****2****O ********  3NaBH****4**** + 6CO****2****               8761 BTU (9243 kJ) **

**Millennium Cell claims 53%-65% recycle efficiency**
**(H****2**** LHV/energy input)**

## Problems:

**On-board **
-  Needs wt/vol optimization
-  Requires exotherm management
-  Requires waste
-    management/flushing
**Off-board**
-  Have not demonstrated economical
-    recycling method
-  H2 cost is not competitive

**Advantages:**

-  Liquid storage is safe, low pressure
-  Relatively long shelf life (~yr half-life)
-  Potentially compact system
-  Waste product is harmless

_**Millennium Cell’s Sodium Borohydride**_

**All engineering issues, not “science” problems**

**Fundamental chemistry issues to resolve/demo**

**Development Level:**

- On-board: moderately well-developed
- Off-Board: Poor/Fair
- Most Developed of all chemical hydride systems

## Power Ball’s Sodium Hydride

**On-board Reaction:  NaH (solid) + H****2****O (liquid) --> NaOH (liquid) + H****2**** (gas)**
**Off-board Recycle: 2NaOH + CH****4**** + O****2**** ******** 2NaH + CO****2**** + 2H****2****O**

**Catalyst:**

**Temperature:** **350C demonstrated, potentially 100-200C**

| Theoretical H2 Wt % | 8.3% (hydride alone) |
| --- | --- |
| System H2 Wt % 
(with half stoic. Water) | ~4.3% |
| H2 Production Efficiency | 25% (~4kWh/kWhH2) |
| Onboard System Cost | ~$400 |
| H2 Cost | $4.1-$5/kg H2 |
| System Vol. Density | 47 kg H2/m3 |

- Based on 1999 Energetics Report (DiPietro)

** ****Dry NaH powder in plastic balls**
** ****Pneumatic splitter opens balls and drops into liquid water**
** ****Maintains 120-150 psi H****2**** in tank**

## Problems:

-  Moderately Heavy System
-  Unproven(?) recycling feasibility
-    and economics
-  High H2 cost
-  Exothermic reaction requires heat
-    removal

**Advantages:**

-  Compact system
-  Onboard system low cost
-  Particularly good in early days of FCV
-    introduction when FCV are geographically
-    dispersed

_**Power Ball’s Sodium Hydride**_

** ****References:**
** ****www.PowerBall.net**
** ****US Patent 5,817,157**
** ****US Patent 5,728,464**

**Development Level:**

- On-board: moderate/well
- Off-Board: Poor/Fair

## Iron Oxidation

**Proposed by H-Power in early 1990’s**
**Recent experiments by ****Kiyoshi Otsuka of the Tokyo Institute of Technology **

**Onboard Reaction:    3Fe + 4 H****2****O --> Fe****3****O****4****  + 4H****2**
**Offboard Recycle: 4(H****2**** or CO)  + Fe****3****O****4**** --> 3 Fe  +  4 (H****2****O or CO****2****)**

**Catalyst: ****aluminum, gallium, chromium or molybdenum catalyst  on magnetite**

**Temperature:** **350C demonstrated, potentially 100-200C**

|  | H2 % |
| --- | --- |
| Theoretical | 4.8% |
| System w/o water | <=3.6% |
| System with Stoic. Water | <=2.7% |

- Based on H-Power calculations.

## Problems:

**Problems:**

-  Inherently heavy system (fatal)
-  Only feasible if FC waste heat is
-    sufficient for reaction
-  Awkward (at best) refueling

**(Potential)**** Advantages:**

-  Iron is cheap
-  $0.50-1.00/kg H2 (based on H-Power
-    estimates)

**Development Level:**

- On-board: Poor/Low
- Off-Board: Poor/Low

## Aluminum

** ****Proposed by Global Hydrofuels ****based on work of Asok Chaklader (Univ. of BC)**
** ****Mechanical mixture of Al metal and Al-oxide(s)/Hydroxide(s)**
** ****Oxides suppress Al passivation and allow 40-70% reaction in 4<pH<9**

**On-board Reaction:    2Al + 6 H****2****O --> 2Al(OH)****3****  +  3H****2**
**Off-board Recycle:  similar to Hall Process ****(conv. Electrolytic Al ore process)**

** ****Pelletized Reactants**
** ****Al metal (99% pure, 80 micron particle size)**
** ****Calcined boehmite (AlOOH)**
** ****50%/50% Al/boehmite wt fraction**
** ****Water must be carried**
** ****10C to 90C Operating Temperature**
** ****~28% expected Energy Efficiency**
**   ****(~13.2 KWh/kg Al reprocessing electricity required)**
**          ****=> ~$6/kg @ $0.05/kWh**

|  | H2 % |
| --- | --- |
| Theoretical (Al only, 100% reaction) | 11.2% |
| With 50%/50% Al/Oxide mixture
(70% reaction) | 3.9% |
| With 50%/50% Al/Oxide mixture + 50% FC water recovery (70% reaction) | 2.6% |
| With 50%/50% Al/Oxide mixture + 50% FC water recovery +
System Components | <2.3% |

## Problems:

**Problems:**

-  Inherently heavy system
-  Low Recycle Energy Efficiency
-  High H2 cost
-  Water must be carried
-  Awkward (at best) refueling

**Advantages:**

-  Reactants & Products non-hazardous
-  Near neutral pH

** ****References:**
** **www.globalhydrofuel.com
-   www.hydrogenvcc.com
-  US Patent 6,440,385
-    (August 2002 “Hydrogen generation
-      from water split reaction”)

**Development Level:**

- On-board: Low/Lab only
- Off-Board: Low but similar to
- 	    commercial process

## Conclusions

**  ****Considerable Chemical Hydride activity in last 5 years**
**  ****Some Ventures have led to **_**mechanically**_** successful**
**    ****in-vehicle demo’s**
**  ****But Commercialization has not yet been prove**
**     ****Need both :     On-Board System commercialization**
**	****	****AND**
**	****      ****Off-Board Recycling commercialization**
** ****Must compete against the leading contender for onboard**
**   ****storage: **
**	****Compressed H****2**** (at 5-10 kpsi):**
**  ****5-8% H****2**** by weight **
** ****<= $2/kg delivered to the tank ****($3-$4/kg in early/small stations)**