3. Production from hydrocacbon
Steam methane reforming(SMR):
• This is today's most efficient method for the production of synthesis
gas CO + H2. With raw material is natural gas should be applied in
the gas sources such as the U.S., Saudi Arabia. In addition, the
source of naphtha is to be used in Europe.
• The reactions:
Besides natural gas, naphtas are also used as raw materials:
• Generally, a nickel catalyst is used for the reaction, loaded to an
alumina base material at 10–15 wt%. Besides nickel, platinum and
ruthenium are also used as catalysts.
5. Production from hydrocarbon
Partial Oxidation (POX):
This process can be used with diverse materials, from gases, liquids and even solids
such as coal.
The reactions:
POX can easily be performed without the presence of a catalyst. High temperatures
of 1200–1450 C and pressures of 3 –7.5 MPa (Texaco process) are needed to
ensure high conversion rates.
The catalytic partial oxidation (CPO) reaction, however, can take place at lower
temperatures and may lead to a significantly enhanced H2 yield from the fuel
6. Production from hydrocarbon
Coal Gasification
During World War II, the syngas is produced by this
method for the production of gasoline. At present,
hardly used due to its high price. However in some
coal-rich countries such as South Africa, it was
maintained.
The reactions:
Then CO is converted to CO2 and H2:
7. LOGO Water Electrolysis
Electrolysis of water is the decomposition of water (H2O) into oxygen
(O2) and hydrogen gas (H2) due to an electric current being passed through
the water.
Electrical energy input
∆G = 237.13 kJ
Perry's Chemical Engineers' Handbook, Section 2.Physical and Chemical Data
Energy exchange the
processes for one mole
of water ∆H = 285.83 kJ
Energy from
environment
T∆S = 48.7 kJ
8. Alkaline electrolysis
- Alkaline electrolyte electrolyzers represent a
very mature technology that is the current
standard for large-scale electrolysis.
Common electrolyte: aqueous potassium
hydroxide (KOH) at 30% concentration
Operation Conditions: 70-100oC and 1- 30bar
Operational voltage: 1.7-2.2 V
Current density: 0.2-0.6 A/cm2
Electricity Consumption: 4.2 – 5.6 kWh/Nm3
Can utilize cost effective electrode
materialsDiaphragm often asbestos
Efficiency: 70-80% (based on hydrogen HHV) [1]
Russell H. Jones & George J. Thomas, “Materials for the
Hydrogen economy”, 2008, p.40
9. PEM Electrolysis [1]
Polymer electrolyte water
Operational principle electrolysis (PEWE) uses a
The water flows from the plate to the polymer electrolyte membrane as
anode through the current collector, and a medium of ion transfer instead of
reacts to make protons. solution electrolyte in AWE. This
Current collectors are porous conductors method is often called polymer
that allow electrons to transfer from electrolyte membrane or proton
electrode to outer circuit and allow reactant exchange membrane (PEM) water
gas from bipolar plate to electrode. electrolysis, too.
The protons are transported through the
PEM to cathode side, and hydrogen is
generated at the cathode.
The PEM also works as a separator of
product gases.
[1] Seiji Kasahara et al., “Water electrolysis” in
“ Nuclear hydrogen production handbook”, 2011
10. PEM Electrolysis
Advantages Disadvantages
Corrosive liquid Components should
electrolyte is not be corrosion
required resistant due to
strong acidity of the
PEM.
Construction of Uniform contact
facility is easy between the PEM
and the electrodes
should be achieved
No electric Cost of the PEM,
resistance by gas electrodes and
bubbles between current collectors is
electrodes can be high
made.
Purity of product gas
is high
11. Steam electrolysis[1]
The process of the high-temperature electrolysis (HTE) of steam is a reverse reaction of the
solid-oxide fuel cell (SOFC): an oxygen ionic conductor is usually used as a solid-oxide
electrolyte.
The electrical energy demand, ΔG, decreases with increasing temperature. The ratio of ΔG to
ΔH is about 93% at 100 C and about 70% at 1000 C
An assembly unit consisting of 15 cells
Outer diameter: 12mm
Active area: 75 cm2
Hydrogen production rate: 100 NL/h.
Operation Conditions: 800oC
Operational voltage: 1.3 V
Current density: 0.45 A/cm2
[1] Seiji Kasahara et al., “Steam electrolysis” in
“ Nuclear hydrogen production handbook”, 2011
12. Photoelectrolysis
Photoelectrolysis involves splitting water directly into hydrogen (H2) and oxygen (O2) using the
energy of sunlight.
The reactive decomposition occurs at 1.23 V, so the minimum bandgap for successful water
splitting is 1.23 eV, corresponding to light of 1008nm. [2]
Operational principle [3]
TiO2 electrode electrowas irradiated with light
consisting of wavelengths shorter than 415 nm (3.0
eV), photocurrent flowed from the Pt electrode to the
TiO2 de through the external circuit.
The direction of the current revealed that the
oxygen occurs at the TiO2 electrode and the
hydrogen occurs at the Pt electrode.
This observation shows that water can be
decomposed, using UV light, without the application
of an external voltage.
13. Photoelectrolysis
This GaInP2
/GaAs multiple-
band-gap
photoelectrochemi
cal cell uses only
illumination and
can generate
hydrogen at
greater than 12%
conversion
efficiency.
Technical Target: Photoelectrochemical Hydrogen Production *
Characteristics Unit 2003 Status 2006 Status 2013 Target 2018 Target
Usable semiconductor
eV 2.8 2.8 2.3 2.0
bandgap
Chemical conversion process
% 4 4 10 12
efficiency (EC)
Plant solar-to-hydrogen
% Not availble Not availble 8 10
efficiency (STH)
Plant durability Hr Not availble Not availble 1000 5000
* Todd G. Deutsch & John A. Turner , Semiconductor Materials for Photoelectrolysis , May 16th, 2012 , p.3
14. Photobiological hydrogen
Microalgae and cyanobacteria are photoautotrophic organisms because they
can use light as the energy source and the carbon dioxide as carbon source
Under anaerobic conditions, microalgae can produce H2, by water photolysis,
using light as the energy source. The catalyst is a hydrogenase, an enzyme that
is extremely sensitive to oxygen, a by-product of photosynthesis.
15. Photobiological hydrogen
• The photosynthetically active radiation
(400–700 nm for green algae, and 400–
950 nm for purple bacteria) or on the full
solar irradiance (all wavelengths).
• In the Netherlands, 420 h would be
needed for the production of 1 GJ of
hydrogen per year. In southern Spain,
this would be 250h.
16. LOGO
Hydrogen Storage
An application-specific issue.
18. Compressed
•Volumetric and Gravimetric densities are inefficient, but
the technology is simple, so by far the most common in
small to medium sized applications.
•3500, 5000, 10,000 psi variants.
19. Liquid (Cryogenic)
•Compressed, chilled, filtered, condensed
•Boils at 22K (-251 C).
•Slow “waste” evaporation •Gravimetrically and volumetrically efficient
•Kept at 1 atm or just slightly over. but very costly to compress
20. Metal Hydrides (sponge)
•Sold by “Interpower” in Germany
•Filled with “HYDRALLOY” E60/0
(TiFeH2)
•Technically a chemical reaction,
but acts like a physical storage
method
•Hydrogen is absorbed like in a
sponge.
•Operates at 3-30 atm, much
lower than 200-700 for
compressed gas tanks
•Comparatively very heavy, but
with good volumetric efficiency,
good for small storage, or where
weight doesn’t matter
21.
22. Carbon Nanofibers
Complex structure
presents a large surface
area for hydrogen to
“dissolve” into
Early claim set the
standard of 65 kgH2/m2
and 6.5 % by weight as a
“goal to beat”
The claim turned out not
to be repeatable
Research continues…
23. Methanol
Broken down by reformer, yields CO, CO2, and
H2 gas.
Very common hydrogen transport method
Distribution infrastructure exists – same as
gasoline
24. Ammonia
Slightly higher volumetric efficiency than methanol
Must be catalyzed at 800-900 deg. C for hydrogen
release
Toxic
Usually transported as a liquid, at 8 atm.
Some Ammonia remains in the catalyzed hydrogen
stream, forming salts in PEM cells that destroy the
cells
Many drawbacks, thus Methanol considered to be a
better solution
25. Alkali Metal Hydrides
“Powerball” company, makes
small (3 mm) coated NaH
spheres.
“Spheres cut and exposed to
water as needed”
H2 gas released
Produces hydroxide solution
waste
26. Sodium Borohydrate
Sodium Borohydrate is the most popular of many
hydrate solutions
Solution passed through a catalyst to release H2
Commonly a one-way process (sodium metaborate
must be returned if recycling is desired.)
Some alternative hydrates are too expensive or toxic
The “Millennium Cell” company uses Sodium
Borohydrate technology
27. Amminex
•Essentially an Ammonia storage method
•Ammonia stored in a salt matrix, very stable
•Ammonia separated & catalyzed for use
•Likely to have non-catalyzed ammonia in hydrogen
stream
•Ammonia poisoning contraindicates use with PEM
fuel cells,
but compatible with alkaline fuel cells.
28. Amminex
•High density, but relies on ammonia production for fuel.
•Represents an improvement on ammonia storage,
which still must be catalyzed.
•Ammonia process still problematic.
29. Diammoniate of Diborane (DADB)
So far, just a computer
simulation.
Compound discovered
via exploration of
Nitrogen/Boron/Hydrogen
compounds (i.e. similar to
Ammonia Borane)
Thermodynamic
properties point towards
spontaneous hydrogen
re-uptake – would make
DADB reusable (vs. other
borohydrates)
30. Solar Zinc production
Isreli research effort
utilizes solar furnace to
produce pure Zinc
Zinc powder can be
easily transported
Zinc can be combined
with water to produce H2
Alternatively could be
made into Zinc-Air
batteries (at higher
energy efficiency)
31. Alkaline metal hydride slurry
SafeHydrogen, LLC
Concept proven with Lithium
Hydride, now working on
magnesium hydride slurry
Like a “PowerBall” slurry
Hydroxide slurry to be re-
collected to be “recycled”
Competitive efficiency to Liquid
H2
32. Storage Method Comparison
Sodium Hydride slurry .9 1.0 Must reclaim used slurry
DADB .1 - .2 .09-.1 (numbers for plain “diborane”and sodium
borohydride, should be similar)
Amminex 9.1 .081
Zinc powder unsure
US DOE goal 9.0 .081
