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Chemisorption

Chemisorption For Catalysts Characterisation


Chemisorption is a specific type of adsorption characterised by a strong interaction between the adsorbate (this could be any gas that adsorbs on to the surface of the material) and the surface of the material (adsorbent).
In physisorption weak Van der Waals forces attract the adsorbate to the adsorbent while in chemisorption these bonds are ionic or covalent, depending on the nature of the material.
Characteristics of chemisorption include:

  • formation of strong chemical bond between adsorbate and chemically active surface sites
  • often have a high activation energy
  • generally irreversible except at high temperatures
  • due to the high adsorption energy the assumption of monolayer adsorption works well, although some multilayer adsorption or spillover is possible

Chemisorption is widely used in catalysts characterisation for investigating:

  • active metal surface area, particularly in heterogeneous catalysis where transition metals are used
  • characterisation of metal dispersion
  • acid site distribution
  • crystallite size
  • heats of adsorption
  • adsorption kinetics

Related technologies such as Temperature programmed Reduction (TPR), temperature programmed desorption (TPD) and temperature programmed oxidation (TPO) can be used to gain further information about both chemisorption and physisorption processes.

 

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Find out more about our range of chemisorption scientific equipment:

ChemStar TPx
ChemStar TPx

Autosorb iQ-C
Autosorb-iQ-C

ChemBET PULSAR TPR/TPD
ChemBET PULSAR TPR/TPD