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Solvent Peroxides : Formation and disposal

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Peroxide Forming Compounds

Chemicals that are sensitive to peroxide formation can be broken into three categories
as shown in the following table. (Jackson, J. Chem. Ed., 1970)

List A
Peroxides from Storage
List B
Peroxides from Concentration
List C
Peroxides from Polymerization

Butadiene *
Chloroprene *
Divinyl acetylene
Isopropyl ether
Potassium amide
Potassium metal
Sodium amide
Tetrafluoroethylene *
Vinyldiene chloride

* Indicates a peroxide former when stored as a liquid monomer.

List A
chemicals should be tested for peroxide formation before using, or discarded after 3 months.

Benzyl alcohol
Cumene (isopropylbenzene)
Decahydronaphthalene (decalin)
Diacetylene (butadiyne)
Diethylene glycol dimethyl ether (diglyme)
Ethyl ether
Methyl acetylene
Methyl-isobutyl ketone
Tetrahydronaphth alene
Vinyl ethers
Other secondary alcohols

List B
chemicals should be tested for peroxides before distillation or evaporation and tested for peroxide formation, or discarded after 1 year.

Butadiene **
Chloroprene **
Tetrafluoroethylene **
Vinyl acetate
Vinyl acetylene
Vinyl chloride
Vinyl pyridine
Vinyldiene chloride

** Can form explosive levels of peroxides if stored as a liquid. When stored as gas, peroxide accumulation may cause autopoly- merization.

List C
chemicals should be tested for peroxide formation, or discard liquids aftter 6 months; and gases after 1 year.

The materials in group A are particularly hazardous and are capable of forming peroxides that may explode even without undergoing distillation or evaporation. One of the more dangerous is isopropyl ether, which decomposes rapidly on storage so that crystals of peroxides accumulate in the threads under the cap. This condition is extremely dangerous and the container should not be opened - friction may initiate detonation.
The chemicals in groups B and C should be discarded or tested for peroxide formation after 12 months. If the age of any of these compounds is unknown, or is suspected to be greater than these recommended time frames, the container should not be opened.

Test for Peroxides

Test for peroxide using freshly prepared KI solution based on the oxidation of iodide ion to iodine. Dissolve 1 gram of KI or sodium iodide in 10 mls glacial acetic acid, and add 1 ml test substance to 1 ml reagent :
Yellow color = low concentration of peroxide
Brown color = high cncentration of peroxide
This test is sensitive to the formation of hydroperoxides (ROOH), which is the principal hazard associated with peroxide-forming solvents, but does not detect difficult to reduce peroxides such as dialkyl peroxides (ROOR).
This type of peroxide can be detected by a reagent consisting of 3 g of sodium iodide dissolved in 50 mL of glacial acetic acid and adding 2 mL of 37% hydrochloric acid.
More recently, test strips have been developed that will test for the presence of peroxides.

Disposal of Peroxides

Liquids :

Dilution and Inceneration.
For small quantities of both refrigerated and ambient storage organic peroxides. Dilute peroxide to 1 % active oxygen or less than 10 % by weight (whichever is lower) in common hydrocarbons which are readily soluble with organic peroxides. The hydrocarbon solvent should be the same temperature as the peroxide being diluted, so that the heat contribution from the peroxide will be negligible. The mixture is then incinerated in a chemical incinerator.
Note : This procedure is NOT reccommended for solid peroxides.

Solids :

Solids are disposed of 'as is' or as water wet mixtures by the process of inceneration.
Inceneration not only gives rapid and complete decomposition, but also eliminates the decomposition products. Direct inceneration has become the accepted means of disposal of all types of peroxides.


Disposal of Methyl Ethyl Ketone Peroxide (MEKP) :

1.Harden with polyester resin, and dispose in landfill.
2.Hydrolysis :
Incremental addition of MEKP to a rapidly stirred, cold 5 - 10 % sodium hydroxide solution. Reaction requires adequate agitation and temperature control between 30 to 40 °C. Note : NEVER add the caustic to the MEKP.

This procedure converts the MEKP to water soluble salts which can be disposed of as non hazardous waste.

References :
1. Safety Guidelines for Peroxidizable Organic Chemicals, Jackson, J. Chem. Ed., 1970

Signature: Dhanlal De Lloyd, Chem. Dept, The University of The West Indies, St. Augustine campus
The Republic of Trinidad and Tobago.
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