Naphthalene Powder CAS 91-20-3

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Naphthalene powder, the simplest condensed aromatic hydrocarbon, with the formula C10H8, is composed of two benzene rings sharing two adjacent carbon atoms. White crystalline powder, easy to volatilize, with mild aromatic smell, and crude naphthalene has coal tar odor. Insoluble in water, but soluble in absolute ethanol, ether and benzene. It is soluble in most organic solvents such as benzene, toluene, xylene, acetic acid, tetrahydronaphthalene, ether, acetone, carbon tetrachloride, carbon disulfide, methanol, ethanol, etc. Molten naphthalene is an excellent solvent for various organic compounds. Dyes such as indigo blue and nitroalizarin blue that are insoluble in organic solvents at room temperature can be soluble in molten naphthalene. Naphthalene dissolves most compounds containing phosphorus, sulfur and iodine. The solubility of naphthalene in water is very low. Naphthalene is widely used as raw material for preparing dyes, resins, solvents, etc., and also as insect repellent.

Uses of naphthalene powder:

[Purpose 1]

Synthetic medicine, insecticide, spice, dye, rubber antioxidant

[Purpose 2]

It is mainly used for the production of phthalic anhydride, as well as raw materials for the production of dyes, medicines, etc

[Purpose 3]

It is mainly used for the production of phthalic anhydride, as well as the basic raw materials for the preparation of dyes, pharmaceuticals, plastics, etc. It can be used to manufacture dye intermediates, dispersants, water reducing agents, etc

[Purpose 4]

Used as solvent and analytical reagent, also used in organic synthesis

[Purpose 5]

It is used to prevent mildew and corrosion of leather.

[Purpose 6]

Naphthalene is a raw material in the production of pesticides, which can be manufactured into naphthol and naphthol, or oxidized into phthalic anhydride to further generate phthalimide, or with chloroacetic acid to generate naphthylacetic acid. It can be used as an intermediate of insecticides such as imifos and carbaryl, herbicides such as herbicides such as methimaxone and chlorhexidine, and plant growth regulators such as naphthylacetic acid and naphthoxyacetic acid.

[Purpose 7]

It is the most important polycyclic hydrocarbon in industry. It is mainly used to produce phthalic anhydride, various naphthols, naphthylamines, etc. It is also the raw material for the production of synthetic resins, plasticizers, intermediates of dyes, surfactants, synthetic fibers, coatings, pesticides, medicines, spices, rubber additives and pesticides. The distribution of naphthalene use varies from country to country. It is used to produce 70% phthalic anhydride, 15% dye intermediates and rubber auxiliaries, 6% pesticides and 4% tanning agents. A large proportion of pesticides are produced in the United States, mainly for the production of carbaryl. Various intermediates can be prepared from naphthalene through sulfonation, nitration, reduction, amination, hydrolysis and other unit operations. The application of refined naphthalene is still expanding. The new product "super plastic material", namely naphthalene sulfonate formaldehyde condensate, can be used as cement additive to increase the plastic deformation of concrete without reducing its strength. In the next few years, the demand will increase by 5-10%.

[Purpose 8]

Solvent used for crystallization of insoluble dyes in organic analysis. Determination of molecular weight. Colorimetric standard. Standard for the determination of carbon and hydrogen by organic microanalysis. Crystal organic scintillator in liquid scintillation counting. Calibrate the thermometer. Organic synthesis.

Preparation of naphthalene powder:

1. It is separated from coal tar. Naphthalene accounts for about 8% - 12% of high temperature coal tar. Distill the coal tar, cut the kerosene, remove phenol and quinoline, and distill to obtain finished naphthalene. Each ton of naphthalene consumes 10t coal tar.

2. Prepared from petroleum hydrocarbons: catalytic heavy reforming oil, catalytic cracking light circulating oil, tar by-product from cracking to ethylene, etc.

3. Refined naphthalene is obtained by refining crude naphthalene with clay.

4. In the static fractional crystallization method, the raw industrial naphthalene is loaded into the crystallization box for rapid cooling, and then it is cooled down to 82 ℃, then it is cooled down evenly, and then it is cooled down to 60 ℃ at a cooling rate of 2 ℃/h, and the first crystallization naphthalene oil rich in sulfindene is discharged as the middle distillate for post-processing. Then, the materials in the crystallization box are heated at the rate of 4 ℃/h, sampled once every 0.5h, and their crystallization points are measured. According to the different crystallization points, they are discharged into the corresponding distillate tanks, so that 3-4 fractional crystallization can be carried out to obtain high-purity refined naphthalene.

5. The production process of falling film fractional crystallization is composed of product production process system, energy system, nitrogen sealing system and computer control system. The production process system takes the big cycle as the production cycle. Each big cycle includes four small cycles, and each small cycle includes 4-6 segments. Each segment consists of three steps: crystallization, partial melting and full melting. Example of falling film crystallization process: the liquid industrial naphthalene sent from the industrial naphthalene unit is sent into the distillate tank. When the fourth stage of crystallization operation is carried out, the feed liquid in the tank is pumped into the dynamic crystallizer collection tank. Uncrystallized naphthalene oil and sweat liquor are put into the distillate tank with lower purity, and the whole melt can be used as the raw material of the fifth stage. The refined naphthalene can be obtained after six stages of crystallization refining according to the predetermined procedure. In order to improve the extraction rate of naphthalene, the fraction rich in thioindene can be sent to the static crystallizer for treatment, and the products obtained from the static crystallizer will be returned to the corresponding distillate tank of the dynamic crystallization system, and the residual liquid can be sold as a water reducer. Since the device uses both dynamic and static crystallizers, it can not only ensure higher naphthalene recovery, but also reduce energy consumption.

Chemical properties of naphthalene:

1. Oxidation of naphthalene

A mild oxidant yields quinone, and a strong oxidant yields anhydride. Naphthalene ring is easier to be oxidized than side chain, so naphthoic acid cannot be prepared by side chain oxidation. The rings with high electron cloud density are easy to be oxidized. for example α- Nitro naphthalene is oxidized to 3-nitrophthalic anhydride, α- Naphthylamine is oxidized to phthalic anhydride (the ring of amino group is oxidized).

2. Reduction reaction (addition reaction) of naphthalene

Naphthalene can be added with 5 hydrogen to form decalin.

3. Electrophilic substitution of naphthalene

Naphthalene α- Bit ratio β- The electrophilic substitution reaction is more likely to take place in the. α- Both of the two resonances have complete benzene rings. β- There is only one resonance type with complete benzene ring.

The electrophilic substitution mainly occurs on the naphthalene ring, which is the same as the benzene ring (easy to replace, difficult to add), but is more active than the benzene ring.

Start from the C next to the two symmetrical C in the middle (the two carbon in the middle are not numbered). Among them, carbon 1, 4, 5 and 8 have the same activity (called α Carbon), No. 2, 3, 6 and 7 carbon have the same properties (called β Carbon).

Normally, α Carbon activity greater than β Carbon, substituent in α This is controlled by dynamics. When the temperature is high naphthalene powder. α The substituents on the carbon will be transferred to β On carbon.

However, the Friedel Crafts acylation reaction of naphthalene generates α Bitsum β A mixture of bits. If nitromethane is used as solvent, it mainly generates β Acylation products.

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