Hydrogen purification

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Hydrogen purification is any technology used to purify hydrogen. The impurities in hydrogen gas depend on the source of the H2, e.g., petroleum, coal, electrolysis, etc. The required purity is determined by the application of the hydrogen gas. For example, ultra-high purified hydrogen is needed for applications like proton exchange membrane fuel cells. [1]

Contents

Purification technologies

Low temperature methods

The default large-scale purification of H2 produced in oil refineries exploits its very low boiling point of −253 °C. Most impurities have boiling points well above this temperature. Low temperature methods can be complemented by scrubbing to remove particular impurities. [1]

Palladium membrane hydrogen purifiers

Hydrogen can be purified by passing through a membrane composed of palladium and silver. Permeability of the former to hydrogen was discovered back in the 1860s. [2] An alloy with a ca. 3:1 ratio for Pd:Ag is more structural robust than pure Pd, which is the active component that allows the selective diffusion of H2 through it. Diffusion is faster near 300 °C. This method has been used for purification of hydrogen on a laboratory scale, but not in industry. Silver-palladium membranes are unstable toward alkenes and sulfur-containing compounds. [1]

Dense thin-metal membrane purifiers are compact, relatively inexpensive and simple to use. [3] [4]

Pressure swing adsorption

Pressure swing adsorption is used for the removal of carbon dioxide (CO2) as the final step in the large-scale commercial synthesis of hydrogen. It can also remove methane, carbon monoxide, nitrogen, moisture and in some cases, argon, from hydrogen.

Applications

Metalorganic vapour phase epitaxy

Hydrogen purifiers are used in metalorganic vapour phase epitaxy reactors for LED production. [5]

PEM fuel cells

Fuel cell electric vehicles commonly use polymer electrolyte membrane fuel cells (PEMFC) that are susceptible to a range of impurities. Impurities impact PEMFC using a range of mechanisms, these may include poisoning the anode hydrogen oxidation reaction catalysts, reducing the ionic conductivity of the ionomer and membrane, altering wetting behaviour of components or blocking porosity in diffusion media. The impact of some impurities like carbon monoxide, formic acid, or formaldehyde is reversible with PEMFC performance recovering once the supply of impurity is removed. Other impurities, for example sulphurous compounds, may cause irreversible degradation. [6] The permissible limits of hydrogen impurities are shown below.

Fuel Quality Specification For Gasseous Hydrogen Supplied to PEMFC Road Vehicles [7]
Maximum Permissible Concentration / μmol mol−1
Total non-hydrogen gasses300
Water5
Total Hydrocarbons Except Methane [Carbon atom basis]2
Methane100
Oxygen5
Helium300
Nitrogen300
Argon300
Carbon Dioxide2
Carbon Monoxide0.2
Total Sulphur Compounds [Sulphur atom basis]0.004
Formaldehyde0.2
Formic Acid0.2
Ammonia0.1
Halogenated Compounds [Halogen ion basis]0.05
Maximum Particulate Concentration1 mg kg−1

Efforts to assess the compliance of hydrogen supplied by hydrogen refuelling stations against the ISO-14687 standard have been performed. [8] [9] [10] While the hydrogen was generally found to be 'good' [8] violations of the standard have been reported, most frequently for nitrogen, water and oxygen.

Combustion engines and appliances

Combustion applications are generally more tolerant of hydrogen impurities than PEFMC, as such the ISO-14687 standard for permissible impurities is less strict. [11] This standard has itself been criticised with revisions proposed to make it more lenient and therefore suitable for hydrogen distributed through a repurposed gas network. [12]

Fuel Quality Specification For Gaseous Hydrogen Supplied to Combustion Engines and Appliances [13]
ImpurityMaximum Permissible Concentration / μmol mol−1
Total non-hydrogen gasses20 000
WaterNon-condensing
Total Hydrocarbons [Carbon atom basis]100
Carbon Monoxide1
Sulphur [Sulphur atom basis]2
Combined water, oxygen, nitrogen, argon19 000
Permanent ParticulatesShall not contain an amount sufficient to cause damage.

Sources of impurities

The presence of impurities in hydrogen depends on the feedstock and the production process. Hydrogen produced by electrolysis of water may routinely include trace oxygen and water. Hydrogen produced by reforming of hydrocarbons contains carbon dioxide and carbon monoxide as well as sulphur compounds. [12] Some impurities may be added deliberately, for example odorants to aid detection of gas leaks. [14]

Methods for analysis

As the permissible concentrations for many impurities are very low this sets stringent demands on the sensitivity of the analytical methods. Moreover, the high reactivity of some impurities requires use of a properly passivated sampling and analytical systems. [15] Sampling of hydrogen of is challenging and care must be taken to ensure that impurities are not introduced to the sample and that impurities do not absorb on or react within the sampling equipment, there are currently different methods for sampling but rely on filling a gas cylinder from the refuelling nozzle of a refuelling station. [16] Efforts are underway to standardise and compare sampling strategies. [17] [18] A combination of different instruments is needed to assess hydrogen samples for all of the components listed in ISO 14687-2. [19] Techniques suitable for individual impurities are indicated in the table below.

Example Analytical Methods for Asessing The Concentration of Impurities in Hydrogen [20] [21]
ImpurityPossible Analytical MethodsDetection Limits
Total non-hydrogen gasses
WaterQuartz crystal microbalance

or CRDS

1.3 or 0.030
Total Hydrocarbons Except Methane [Carbon atom basis]GC-Methaniser-FID0.1
MethaneGC-Methaniser-FID, GC-EPD0.1
OxygenGC-PDHID, GC-EPD0.3
HeliumGC-TCD10
NitrogenGC-PDHID, GC-EPD1
ArgonGC-PDHID, GC-EPD0.3
Carbon DioxideGC-Methaniser-FID, GC-EPD0.02
Carbon MonoxideGC-Methaniser-FID, GC-EPD0.02
Total Sulphur Compounds [Sulphur atom basis]GC-SCD, GC-EPD0.001
FormaldehydeGC-Methaniser-FID0.1
Formic AcidFTIR0.2
AmmoniaGC-MS or UV-visible spectroscopy or FTIR1 or 0.03 or 0.1
Halogenated Compounds (Halogen Ion Equivalent)TD-GC-MS0.016

Techniques such as electrochemical sensors [22] [23] and mass spectrometry. [24]

See also

Related Research Articles

<span class="mw-page-title-main">Fuel cell</span> Device that converts the chemical energy from a fuel into electricity

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

A regenerative fuel cell or reverse fuel cell (RFC) is a fuel cell run in reverse mode, which consumes electricity and chemical B to produce chemical A. By definition, the process of any fuel cell could be reversed. However, a given device is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Standard fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as with high-pressure electrolysers, regenerative fuel cells, solid-oxide electrolyser cells and unitized regenerative fuel cells.

<span class="mw-page-title-main">Proton-exchange membrane fuel cell</span> Power generation technology

Proton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity. They are a leading candidate to replace the aging alkaline fuel-cell technology, which was used in the Space Shuttle.

<span class="mw-page-title-main">Steam reforming</span> Method for producing hydrogen and carbon monoxide from hydrocarbon fuels

Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen production. The reaction is represented by this equilibrium:

A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton-exchange membrane fuel cell or of a proton-exchange membrane electrolyser: separation of reactants and transport of protons while blocking a direct electronic pathway through the membrane.

<span class="mw-page-title-main">Electrolysis of water</span> Electricity-induced chemical reaction

Electrolysis of water is using electricity to split water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, but must be kept apart from the oxygen as the mixture would be extremely explosive. Separately pressurised into convenient 'tanks' or 'gas bottles', hydrogen can be used for oxyhydrogen welding and other applications, as the hydrogen / oxygen flame can reach approximately 2,800°C.

Formic acid fuel cells (direct formic acid fuel cells or DFAFCs) are a subcategory of direct liquid-feed fuel cells (DLFCs), in which the liquid fuel is directly oxidized (electrochemically) at the anode instead of reforming to produce hydrogen. Formic acid-based fuel cells represent a promising energy supply system in terms of high volumetric energy density, theoretical energy efficiency, and theoretical open-circuit voltage. They are also able to overcome certain problems inherent to traditional hydrogen (H2) feed fuel cells such as safe handling, storage, and H2 transportation.

<span class="mw-page-title-main">Protonic ceramic fuel cell</span>

A protonic ceramic fuel cell or PCFC is a fuel cell based around a ceramic, solid, electrolyte material as the proton conductor from anode to cathode. These fuel cells produce electricity by removing an electron from a hydrogen atom, pushing the charged hydrogen atom through the ceramic membrane, and returning the electron to the hydrogen on the other side of the ceramic membrane during a reaction with oxygen. The reaction of many proposed fuels in PCFCs produce electricity and heat, the latter keeping the device at a suitable temperature. Efficient proton conductivity through most discovered ceramic electrolyte materials require elevated operational temperatures around 400-700 degrees Celsius, however intermediate temperature (200-400 degrees Celsius) ceramic fuel cells and lower temperature alternative are an active area of research. In addition to hydrogen gas, the ability to operate at intermediate and high temperatures enables the use of a variety of liquid hydrogen carrier fuels, including: ammonia, and methane. The technology shares the thermal and kinetic advantages of high temperature molten carbonate and solid oxide fuel cells, while exhibiting all of the intrinsic benefits of proton conduction in proton-exchange membrane fuel cells (PEMFC) and phosphoric acid fuel cells (PAFC). PCFCs exhaust water at the cathode and unused fuel, fuel reactant products and fuel impurities at the anode. Common chemical compositions of the ceramic membranes are barium zirconate (BaZrO3), barium cerate (BaCeO3), caesium dihydrogen phosphate (CsH2PO4), and complex solid solutions of those materials with other ceramic oxides. The acidic oxide ceramics are sometimes broken into their own class of protonic ceramic fuel cells termed "solid acid fuel cells".

<span class="mw-page-title-main">Hydrogen storage</span> Methods of storing hydrogen for later use

Several methods exist for storing hydrogen. These include mechanical approaches such as using high pressures and low temperatures, or employing chemical compounds that release H2 upon demand. While large amounts of hydrogen are produced by various industries, it is mostly consumed at the site of production, notably for the synthesis of ammonia. For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. The overarching challenge is the very low boiling point of H2: it boils around 20.268 K (−252.882 °C or −423.188 °F). Achieving such low temperatures requires expending significant energy.

Hydrogen technologies are technologies that relate to the production and use of hydrogen as a part hydrogen economy. Hydrogen technologies are applicable for many uses.

<span class="mw-page-title-main">Reformed methanol fuel cell</span> Fuel Cell Type

Reformed Methanol Fuel Cell (RMFC) or Indirect Methanol Fuel Cell (IMFC) systems are a subcategory of proton-exchange fuel cells where, the fuel, methanol (CH3OH), is reformed, before being fed into the fuel cell.

<span class="mw-page-title-main">Hydrogen infrastructure</span>

A hydrogen infrastructure is the infrastructure of hydrogen pipeline transport, points of hydrogen production and hydrogen stations for distribution as well as the sale of hydrogen fuel, and thus a crucial prerequisite before a successful commercialization of fuel cell technology.

Electromethanogenesis is a form of electrofuel production where methane is produced by direct biological conversion of electrical current and carbon dioxide.

<span class="mw-page-title-main">Proton exchange membrane electrolysis</span> Technology for splitting water molecules

Proton exchange membrane(PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the issues of partial load, low current density, and low pressure operation currently plaguing the alkaline electrolyzer. It involves a proton-exchange membrane.

Alkaline water electrolysis is a type of electrolysis that is characterized by having two electrodes operating in a liquid alkaline electrolyte. Commonly, a solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH) at 25-40 wt% is used. These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions (OH−) from one electrode to the other. A recent comparison showed that state-of-the-art nickel based water electrolysers with alkaline electrolytes lead to competitive or even better efficiencies than acidic polymer electrolyte membrane water electrolysis with platinum group metal based electrocatalysts.

Ethanoligenens harbinense is a strictly anaerobic bacterium. It is Gram-positive, non-spore-forming, mesophilic and motile, its cells being regular rods. Its type strain is YUAN-3T. This hydrogen producing, fermenting bacteria shows potential for bio-related application.

Liquid organic hydrogen carriers (LOHC) are organic compounds that can absorb and release hydrogen through chemical reactions. LOHCs can therefore be used as storage media for hydrogen. In principle, every unsaturated compound can take up hydrogen during hydrogenation. The sequence of endothermal dehydrogenation followed by hydrogen purification is considered as the main drawback which limits the overall efficiency of the storage cycle. LOHC shipping without heat recycling has an energy efficiency of 60-70%, depending on the dehydrogenation rate, which is equivalent to liquid hydrogen shipping. With heat recycling, the energy efficiency increase to 80-90%.

Sorption enhanced water gas shift (SEWGS) is a technology that combines a pre-combustion carbon capture process with the water gas shift reaction (WGS) in order to produce a hydrogen rich stream from the syngas fed to the SEWGS reactor.

High Temperature Proton Exchange Membrane fuel cells (HT-PEMFC), also known as High Temperature Polymer Electrolyte Membrane fuel cells, are a type of PEM fuel cells which can be operated at temperatures between 120 and 200°C. HT-PEM fuel cells are used for both stationary and portable applications. The HT-PEM fuel cell is usually supplied with hydrogen-rich gas like reformate gas formed by reforming of methanol, ethanol, natural gas or LPG.

Hydrogen evolution reaction (HER) is a chemical reaction that yields H2. The conversion of protons to H2 requires reducing equivalents and usually a catalyst. In nature, HER is catalyzed by hydrogenase enzymes. Commercial electrolyzers typically employ supported platinum as the catalyst at the anode of the electrolyzer. HER is useful for producing hydrogen gas, providing a clean-burning fuel. HER, however, can also be an unwelcome side reaction that competes with other reductions such as nitrogen fixation, or electrochemical reduction of carbon dioxide or chrome plating.

References

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  2. ↑ Sammells, Anthony F.; Mundschau, Michael V. (2006-12-13). Nonporous Inorganic Membranes: For Chemical Processing. John Wiley & Sons. ISBN   978-3-527-60858-4.
  3. ↑ Hydrogen purification membranes
  4. ↑ Dense metal membranes for hydrogen purifying
  5. ↑ "Hydrogen purifiers proving vital to LED production". III-Vs Review. 19 (5): 19. June 2006. doi: 10.1016/S0961-1290(06)71698-2 .
  6. ↑ X. Cheng, Z. Shi, N. Glass, L. Zhang, J. Zhang, D. Song, Z.-S. Liu, H. Wang and J. Shen (2007). "A review of PEM hydrogen fuel cell contamination:Impacts, mechanisms, and mitigation". Journal of Power Sources. 165 (2): 739–756. Bibcode:2007JPS...165..739C. doi:10.1016/j.jpowsour.2006.12.012. S2CID   95246225.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ↑ "ISO 14687:2019" . Retrieved 2021-10-18.
  8. 1 2 Aarhaug, Thor Anders; Kjos, Ole; Bacquart, Thomas; Valter, Vladimir; Optenhostert, Thomas (2021-08-18). "Assessment of hydrogen quality dispensed for hydrogen refuelling stations in Europe". International Journal of Hydrogen Energy. HYDROGEN ENERGY SYSTEMS. 46 (57): 29501–29511. Bibcode:2021IJHE...4629501A. doi: 10.1016/j.ijhydene.2020.11.163 . hdl: 11250/3025287 . ISSN   0360-3199. S2CID   230535934.
  9. ↑ Aarhaug, Thor A.; Kjos, Ole S.; Ferber, Alain; Hsu, Jong Pyong; Bacquart, Thomas (2020). "Mapping of Hydrogen Fuel Quality in Europe". Frontiers in Energy Research. 8: 307. doi: 10.3389/fenrg.2020.585334 . hdl: 11250/2770289 . ISSN   2296-598X.
  10. ↑ "HYDRAITE public report D3.1 | HYDRAITE" . Retrieved 2021-10-18.
  11. ↑ "ISO 14687:2019" . Retrieved 2021-10-18.
  12. 1 2 "WP2 Report Hydrogen Purity". Hy4Heat. Retrieved 2021-10-18.
  13. ↑ "ISO 14687:2019" . Retrieved 2021-10-18.
  14. ↑ "Hydrogen Odorant and Leak Detection Project Closure Report" (PDF).
  15. ↑ Bacquart, Thomas; Moore, Niamh; Hart, Nick; Morris, Abigail; Aarhaug, Thor A.; Kjos, Ole; Aupretre, Fabien; Colas, Thibault; Haloua, Frederique; Gozlan, Bruno; Murugan, Arul (2020-02-14). "Hydrogen quality sampling at the hydrogen refuelling station – lessons learnt on sampling at the production and at the nozzle". International Journal of Hydrogen Energy. 22nd World Hydrogen Energy Conference. 45 (8): 5565–5576. Bibcode:2020IJHE...45.5565B. doi:10.1016/j.ijhydene.2019.10.178. hdl: 11250/2689927 . ISSN   0360-3199. S2CID   213820032.
  16. ↑ Arrhenius, Karine; Aarhaug, Thor; Bacquart, Thomas; Morris, Abigail; Bartlett, Sam; Wagner, Lisa; Blondeel, Claire; Gozlan, Bruno; Lescornez, Yann; Chramosta, Nathalie; Spitta, Christian (2021-10-11). "Strategies for the sampling of hydrogen at refuelling stations for purity assessment". International Journal of Hydrogen Energy. 46 (70): 34839–34853. Bibcode:2021IJHE...4634839A. doi: 10.1016/j.ijhydene.2021.08.043 . hdl: 11250/3010363 . ISSN   0360-3199. S2CID   239636011.
  17. ↑ Practice for Sampling of High Pressure Hydrogen and Related Fuel Cell Feed Gases, ASTM International, doi:10.1520/d7606-17 , retrieved 2021-11-01
  18. ↑ DIN ISO/TS 22002-3:2017-09 , retrieved 2021-11-01
  19. ↑ Murugan, Arul; Brown, Andrew S. (2015-03-22). "Review of purity analysis methods for performing quality assurance of fuel cell hydrogen". International Journal of Hydrogen Energy. 40 (11): 4219–4233. Bibcode:2015IJHE...40.4219M. doi:10.1016/j.ijhydene.2015.01.041. ISSN   0360-3199.
  20. ↑ "Hydrogen purity". NPLWebsite. Retrieved 2021-10-18.
  21. ↑ Bacquart, Thomas; Arrhenius, Karine; Persijn, Stefan; Rojo, Andrés; Auprêtre, Fabien; Gozlan, Bruno; Moore, Niamh; Morris, Abigail; Fischer, Andreas; Murugan, Arul; Bartlett, Sam (2019-12-31). "Hydrogen fuel quality from two main production processes: Steam methane reforming and proton exchange membrane water electrolysis". Journal of Power Sources. 444: 227170. Bibcode:2019JPS...44427170B. doi: 10.1016/j.jpowsour.2019.227170 . ISSN   0378-7753. S2CID   208754564.
  22. ↑ Mukundan, Rangachary (2020). "Development of an Electrochemical Hydrogen Contaminant Detector". Journal of the Electrochemical Society. 167 (14): 147507. Bibcode:2020JElS..167n7507M. doi: 10.1149/1945-7111/abc43a . S2CID   226341724.
  23. ↑ Noda, Z.; Hirata, K.; Hayashi, A.; Takahashi, T.; Nakazato, N.; Saigusa, K.; Seo, A.; Suzuki, K.; Ariura, S.; Shinkai, H.; Sasaki, K. (2017-02-02). "Hydrogen pump-type impurity sensors for hydrogen fuels". International Journal of Hydrogen Energy. 42 (5): 3281–3293. Bibcode:2017IJHE...42.3281N. doi:10.1016/j.ijhydene.2016.12.066. ISSN   0360-3199.
  24. ↑ "HydrogenSense". www.vandf.com. Retrieved 2021-10-27.[ permanent dead link ]
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