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How is the peroxide in Tetrahydrofuran(THF) produced and removed - part 1

Views: 5     Author: Site Editor     Publish Time: 2022-04-27      Origin: Site

The dangers of peroxide

Peroxides have strong oxidability and are flammable and explosive compounds. Peroxides all contain peroxygens (-O-O-). Due to the weak bonding force of the peroxygens, the energy required for fracture is not large. The peroxygens are extremely unstable structures, which are very sensitive to heat, vibration, impact or friction. If the heat release rate of the reaction exceeds the heat dissipation rate of the surrounding environment, the temperature rises under the action of the reaction heat of decomposition, and the reaction accelerates and develops to an explosion.

The order of stability of organic peroxides is: ketone peroxides < diacetyl peroxides < ether < dihydrocarbyl peroxides. The lowerTetrahydrofuran for sale - YuanfarChemicals congeners of all kinds of peroxides are more sensitive to mechanical action than the higher congeners and more explosive risk. Peroxide interacts with organic matter to form explosive mixtures under certain conditions. Under the action of variable metal salts and amines, concentrated peroxides decompose rapidly when mixed with strong acids, causing explosions. Hydrogen peroxide and formaldehyde have caused explosions in the past. Acetone peroxide derivatives are accumulated in the residue of the still and explode in the presence of acid. Many explosion and fire accidents occurred when acetone peroxide derivatives containing polyester resin mixed with cobalt naphthenate solution. Solid inorganic peroxide and organic matter contact will also cause oxidation and fire, such as barium peroxide and hemp bag contact occurred spontaneous combustion accident.

Tetrahydrofuran Peroxide detection and removal

Tetrahydrofuran, ether long-term storage is easy to produce peroxide, be careful when using, be sure to detect the peroxide content in the solution first. If more than 0.05% peroxides are present, the peroxides must be removed prior to distillation. If the peroxide content is 1% or higher, THF must be disposed of by incineration and cannot be used again.

Leukocyte peroxidase test:

First, qualitative detection

Method 1: prepare 10%KI (potassium iodide) aqueous solution, add a small amount of starch, and then add 10 ml of Tetrahydrofuran, shake, place for about 3~5min, turn yellow, indicating the presence of peroxide, the darker the color, the more peroxide, otherwise no peroxide, can be safely used.

Method 2: Determine whether the starch - potassium iodide test paper changes color.

Method 3: use 5mLTetrahydrofuran plus 1mL 10% potassium iodide solution, shake for 1min, if there is peroxide, free iodine is released, the water layer is yellow brown or add 4 drops of 0.5% starch solution, the water layer is blue.

Method 4: Put 2~3 drops of concentrated sulfuric acid, 1ml of 2% potassium iodide solution (if potassium iodide solution has been oxidized by air, dilute sodium sulfite solution can be dropped to yellow and disappear) and 1~2 drops of starch solution in a clean test tube, mix evenly and add Tetrahydrofuran, blue or purple indicate the presence of peroxide.

Two, quantitative detection:

Add 6 mL acetic acid +4 ml chloroform +1 g potassium iodide to 50 ml Tetrahydrofuran, place in the dark for 5 minutes, titrate with 0.1 N sodium thiosulfate solution until colorless, peroxide percentage is: NXVX0.7/G where, N and V are the equivalent concentration and volume of sodium thiosulfate respectively (ml), and G is the weight of Tetrahydrofuran (G).

Peroxides formed in solution

Elimination of peroxide in Tetrahydrofuran

1. Tetrahydrofuran peroxide can be removed by mixing with sodium hydroxide and Tetrahydrofuran. If you use alkaloids, use 5 grams of alkaloids for every 100 grams of THF. If using a 73% sodium hydroxide solution, use 15 grams for every 100 grams of THF. However, if the peroxide content is greater than 0.5%, sodium hydroxide should be added slowly to prevent violent reactions and temperature surges. The destruction of peroxides by sodium hydroxide has been successfully applied in practice. Laboratory use of Tetrahydrofuran without peroxide can be made by adding ketone chloride, ferrous sulfate, or other reducing agent and then distillation under lithium aluminium hydroxide. Peroxides decompose rapidly in the presence of a base. The process is an elimination reaction that depends on the presence or absence of hydrogen atoms at the α -carbon atoms.

2. The peroxide can be removed by a newly prepared dilute solution of ferrous sulfate (prepared by FeSO4 H2O60g, 100mL water and 6mL concentrated sulfuric acid). Wash 100mLTetrahydrofuran and 10mL newly prepared ferrous sulfate solution several times in a separating funnel until no peroxide is found. (Dosage is 20% of Tetrahydrofuran volume).

3. Pass THF through activated alumina to remove peroxide.

4. Neutralize and reduce with 10% sodium sulfite.

5. Once the drums of Tetrahydrofuran are opened, the storage life will be shortened, even if recharged with nitrogen protection. Therefore, THF left in the drum should be used as soon as possible.

6. Adding antioxidant such as 2,6, 2t-butylp-cresol to Tetrahydrofuran can effectively inhibit the formation of peroxide. The mechanism of action is that such antioxidants can combine with the active group to form a more stable compound, thus stopping the chain reaction.

7. Storing peroxides in a container with a rough surface speeds their decomposition. Such as 38% hydrogen peroxide in the polished platinum dish heated to 60℃ still does not decompose, and there are many scratches on the inner surface of the platinum dish will decompose at room temperature. These are just a few ways to remove peroxide. Preparation methods of several laboratory anhydrous solvents.

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