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Naphthalene: industrial naphthalene and refined naphthalene

Views: 12     Author: Site Editor     Publish Time: 2022-07-05      Origin: Site

What is naphthalene?


Basic information about naphthalene

Chemical formula C10H8
Molecular weight 128.174
CAS 91-20-3
EINECS 202-049-5


Physical properties of naphthalene

Appearance Colorless/white crystalline powder
Density 1.16 g/cm3
Melting point 80-82 ℃
Boiling point 217.9 ℃
Flash 78.9 ℃
Saturated vapor pressure 0.0131kPa (25℃)
Solubility Insoluble in water, soluble in anhydrous ethanol, ether, benzene



Chemical properties of naphthalene

1. Oxidation reaction of naphthalene

Mild oxidants yield quinones and strong oxidants yield anhydrides. Naphthalene is more easily oxidized than side chain, so side chain oxidation cannot be used to produce naphthalene formic acid. Rings with high electron cloud density are easily oxidized. For example, alpha-nitronaphthalene is oxidized to 3-nitrophthalic anhydride, and alpha-naphthalamine to phthalic anhydride (the ring in which the amino group is oxidized).

2. Reduction reaction of naphthalene (addition reaction)

Naphthalene can be added with 5 hydrogen to form decalin.

3. Electrophilic substitution reaction of naphthalene

The α- site of naphthalene is more prone to electrophilic substitution than the β- site. Both of the resonance formulas have complete benzene rings. Only one of the resonance forms of β -position substitutions has a complete benzene ring.

Electrophilic substitution mainly occurs on naphthalene rings, as with benzene rings (easy to replace, difficult to add), but more active than benzene rings.


The dangers of naphthalene


The toxicity of naphthalene


Invasion route: inhalation, ingestion, percutaneous absorption.

Health hazards

Naphthalene has stimulating effect, high concentration of hemolytic anemia and liver, kidney damage. Can lead to anemia or a significant reduction in the number of red blood cells, hemoglobin and blood cells. Naphthalene can cause some serious skin problems in people with sensitive skin.

Acute poisoning

When inhaling high concentration of naphthalene vapor or dust, eye and respiratory irritation, corneal opacity, headache, nausea, vomiting, loss of appetite, lumbago, frequent urination, protein and red and white cells in urine appear. Optic neuritis and retinitis can also occur. Toxic encephalopathy and liver damage can occur in severe cases. Oral poisoning mainly causes hemolysis, liver and kidney damage, and even acute renal failure and liver necrosis.

Chronic poisoning

Repeated exposure to naphthalene vapors may cause headache, fatigue, nausea, vomiting and damage to the blood system, can cause cataract, optic neuritis and retinopathy. Skin contact with naphthalene may cause dermatitis.


Chemical reaction and explosion

Naphthalene is flammable when it encounters open fire and high heat. When it burns, it emits a noxious, irritating smoke. Contact with strong oxidants such as chromic anhydride, chlorate and potassium permanganate can result in a violent reaction, resulting in combustion or explosion. Naphthalene powder can form an explosive mixture with air, and when it reaches a certain concentration, it will explode on contact with Mars.



What is industrial naphthalene?

Naphthalene products containing more than 95% of naphthalene by distillation may be referred to as industrial naphthalene. Industrial naphthalene is an important basic chemical raw material, mainly used in the production of water reducing agent, refined naphthalene, benzene anhydride, naphthalene phenol, naphthalene amine and other chemical products, is the production of synthetic fiber, synthetic resin, plasticizer, rubber antiaging agent, dye intermediates, pesticides and medicine raw materials. Industrial naphthalene is a very important product in the deep processing of coal tar, and the mass fraction of naphthalene in high-temperature coal tar accounts for about 10%.



Industrial naphthalene and refined naphthalene

High purity naphthalene can be obtained after further purification and desulfurization of industrial naphthalene.


How to make refined naphthalene

Tar naphthalene

Industrial naphthalene contains impurities thiolindene (1-3%), methyl naphthalene (1-2%) and a small amount of indene, tar-base and pyroic acid. After further pickling and distillation, refined naphthalene with sulfur content less than 0.1% and freezing point of 79℃ can be obtained. If further refining is required to reduce the sulfur content to less than 0.05%, hydrorefining is required.

Petroleum naphthalene

Petroleum naphthalene is derived from heavy aromatic components of catalytic reforming, catalytic cracking and hydrocarbon cracking. The content of methyl naphthalene in catalytic reforming oil is about 55%. First through extraction and adsorption, from the raw material distillate to separate a variety of naphthalene homology, and then using catalytic hydrogen dealkylation method, with Cr2O3-al2o3 as the catalyst, at 400-800℃ and 0.5-7 mpa under the hydrogen demethylation reaction, reaction products after cooling gas phase material, distillation to remove light components benzene, toluene, xylene, etc. Finally, petroleum naphthalene products can be obtained by further distillation. The product was purified by solvent absorption and solvent washing, and its purity reached 99.73%.


Conclusion

Industrial naphthalene is the basic chemical raw material, and refined naphthalene is the purified product of industrial naphthalene. Industrial naphthalene has different uses from refined naphthalene. Industrial naphthalene is mainly used in the production of water reducing agent, diffusion agent, is the production of synthetic resin, plasticizer, rubber anti-aging agent, surfactant, synthetic fiber, dye, medicine and spices and other raw materials. Naphthalene is used primarily as a fumigant in insecticides (e.g., mothballs).


Related links:

What is refined naphthalene?

Buy refined naphthalene - Product details page.


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