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What is it?

Membrane based ammonia synthesis is a method in which hydrogen gas is supplied on one side of a dense metallic membrane and nitrogen gas on the other. The structure of the membrane allows individual hydrogen atoms to pass through to the nitrogen gas side and react to form ammonia.

Why is it important?

Membrane based ammonia synthesis offers a near-term opportunity to achieve significant reductions in operating costs and carbon emissions compared to the traditional Haber-Bosch process.


  • Volumetric hydrogen density: High (10.7kg H2 / m3 at 10 bar and 25°C)
  • Gravimetric hydrogen density: High (17.8% by mass)
  • Storage conditions: Liquid at ambient temperature, 10-11 bar pressure


  • Low pressure ammonia synthesis – allows direct coupling of reactor to electrolyser and air separation unit
  • Less capital intensive than Haber-Bosch synthesis
  • Highest non-Haber-Bosch synthesis rate achieved
  • Fast switch-on/off times can accommodate intermittent energy sources
  • Centralised or decentralised ammonia production possible


  • Does not allow direct synthesis of ammonia from nitrogen and water

RD&D priorities

  • Improve conversion efficiency to ~15% (from ~4%)
  • Demonstrate use of lower-cost membranes
  • Improve production rate
  • Utilise lower-cost catalysts

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