Classification of Co-Catalysts
Classification of Co-Catalysts:
(1) Structural cocatalyst
(2) Electronic co-catalyst:
(3) Lattice defect type co-catalyst: Disorder the atomic arrangement of the crystal plane of the active material and increase the concentration of lattice defects to improve the catalytic activity of the catalyst.
Classes (2) and (3) are also collectively referred to as modulating co-catalysts
Structural Co-catalyst:
Function: Improve the dispersibility and thermal stability of active components.
Principle: It can reduce the particle size of catalytic active substances, increase the surface area, prevent or delay the reduction of activity due to sintering, etc. The industrial catalytic process is usually carried out under the conditions of several hundred degrees, and the originally unstable crystallites are easily sintered, which leads to the degradation of the catalyst. activity decreased. The addition of co-catalyst can prevent or slow down the growth rate of crystallites, thereby prolonging the service life of the catalyst. For example: iron catalyst for ammonia synthesis, adding a small amount of Al2O3
Electronic Co-catalyst:
Function: Change the structure and chemical composition of catalyst active substances, and promote the selectivity of catalytic activity.
Principle: The empty d orbital of the active component of the catalyst can accept the electrons provided by the cocatalyst, which changes the electronic structure of the active component and improves the activity and selectivity of the catalyst; it may generate a new crystal phase, or it may also generate or increase the catalyst. The number of mesocrystalline phases or active interfaces between crystallites. Thereby increasing activity or selectivity.
For example: Adding K2O to Fe-Al2O3
