THE PROCESS

  • Continuous Hydrothermal Synthesis

    Nanomaterials are formed by the continuous mixing of a superheated flow of water against a flow of water containing dissolved metal salts

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  • Hydrolysis

    The metal ions form hydroxides

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  • Dehydration

    The hydroxides are dehydrated to form an oxide

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  • Particle nucleation

    The particles form from the clustering of 100s to 1000s of atoms

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  • Particle Growth

    The particles are formed and carried away in suspension

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The Shyman Process

The Shyman Project was focussed on the scale up of the hydrothermal synthesis process.

This process is an alternative route to manufacture that offers unique opportunities for the synthesis of high quality nanoparticles and their formulation.

Hydrothermal synthesis presents a significant number of advantages since it:

  1. Does not tend to use noxious chemicals – with water soluble precursors and water as a solvent.
  2. Uses relatively simple chemistry – generally following hydrolysis and dehydration stages.
  3. Allows straightforward downstream processing - the process is dispersion based.
  4. Uses relatively cheap chemical precursors – acetates, nitrates and phosphates.
  5. Can produce stoichiometric compounds.
  6. Can produce non-stoichiometric materials where precise alloying or doping can be achieved.
  7. Can avoid agglomeration - the dispersed materials can be stabilised with additives, in situ.
  8. Size and shape distribution can be narrow and well controlled.
Making the process continuous

Continuous hydrothermal synthesis produces nanoparticulate materials by mixing superheated/supercritical water with a solution of a metal salt. i.e. rather than slowly heating the entire contents of a batch vessel, two fluids are continuously mixed together.

When water is heated towards its critical point (374oC, 218 atm.), the ionic product [H+][OH-] increases and the superheated fluid is technically supercritical, rather than near-critical.

The enhanced levels of OH- were first exploited for continuous nanoparticle production by Adschiri and Arai, in 1992, who showed that under these conditions hydrolysis of metal salts (MLx) is immediately followed by a dehydration step.


The step from batch to continuous hydrothermal synthesis has been held back by engineering issues around mixing the heated fluid and the aqueous metal salt flow. T piece reactors  were originally used but these are now, generally accepted as problematic.

The project was designed to scale up the system used by Promethean Particles (www.prometheanparticles.co.uk) from its current scale of 1-10 tons per year to over 100 tons per year. 

In the end we designed, built and commissioned a plant capable of producing more than 1000 tons per year. This was run in 2016 for the first time and the plant is now fully commissioned and operational. For further information contact Promethean Particles






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