Hydroxyl Radicals Reactivity

Hydroxyl radicals are an ultimate oxidation tool — able to attack any molecule in their vicinity in order to balance their unpaired electron configuration.

Hydroxyl radicals can break double bonds (C=C, N=N), degrade hydrocarbons, cause epoxidation and aromatic ring opening, radical polymerization, formation of secondary radicals and many other types of reactions.

Production of hydroxyl radicals is therefore the most powerful way to access oxidation reactions.

Catalytic decomposition of hydrogen peroxide is a straightforward and extremely efficient method to produce hydroxyl radicals when used with Hydrogen Link's proprietary catalyst. Being heterogenous, the catalyst does not interfere directly with the reaction of other components with the hydroxyl radicals.

Formation of the hydroxyl radicals is illustrated below by the reaction with methylene blue — a known hydroxyl radical.The treatment with H2O2 with a very small amount of our catalyst results with decoloration of concentrated methylene blue within several minutes, completed by full mineralization.

               

While hydroxyl radicals are not selective, their reactions can be in practice highly controllable through the following:

  • engineering of the reaction path by the choice of components to be exposed to the the hydroxyl reactivity (formation of other radicals, stepwise introduction of the components, chain reactions etc.)
  • controlled rate of the formation of radicals (through the precise amount of the H2O2 and the catalyst to achieve the required amount of the radicals)
  • the use of radical sinks, scavengers and quenching of the reaction at any required moment

The use of the technology relates not only to homogeneous reactions (where the reagents are soluble in water solutions of H2O2) but also in a variety of heterogeneous reactions, where the oxidized substance is in another phase, e.g. gas or a hydrophobic chemical. This includes oxidation of greenhouse gases such as CO or NOx being oxidized in a catalyzed hydrogen peroxide bath.


Another example of the heterogeneous oxidation is shown below in a reaction of the oxidation of coumarin. Although coumarin is not soluble in the hydrogen peroxide, when in contact with the catalyzed decomposition of H2O2it undergoes instant hydroxylation, as demonstrated by the formation of highly UV-fluorescent hydroxycoumarins. If the reaction is carried out even further, full demineralization of coumarin is achieved.

       


Hydroxyl radicals are capable of full decomposition of cellulose through a series of decomposition stages into more and more degraded stages.

 

         

Degradation of Cellulose by Catalyzed Hydrogen Peroxide


Methylene Blue discoloration evidencing the hydroxyl radicals formation

 


Please contact us with inquires related to  our catalyst and oxygen generators at contact@hydrogenlink.com


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