工业萘中的杂质主要是与萘沸点较接近的四氢萘、硫杂?、二甲酚等。如萘的沸点(218℃)和硫?的沸点（219℃）相差不到2℃，因此为了制造纯度更高的精萘，就要利用萘与这些杂质熔点不同的物理性质进行分离，或者利用化学方法来改变它们的化学组成。当前精萘的生产方法，有加氢精制法、酸洗蒸熘法、升华法、结晶法等。

The impurities in industrial naphthalene are mainly tetrahydronaphthalene and sulfur impurities, which have boiling points close to naphthalene Dimethylphenol, etc. Like the boiling point of naphthalene (218 ℃) and sulfur? The boiling point (219 ℃) of naphthalene is less than 2 ℃, so in order to produce higher purity refined naphthalene, it is necessary to separate naphthalene from these impurities by utilizing their different physical properties with different melting points, or use chemical methods to change their chemical composition. The current production methods for refined naphthalene include hydrogenation refining, acid washing and steaming, sublimation, crystallization, etc.

酸洗蒸熘法应用较早，但由千酸洗带来严重腐蚀，萘损失率高，且废酸难以处理，所以正趋于淘汰。

The acid washing and steaming method was applied earlier, but it is being phased out due to severe corrosion caused by thousand acid washing, high naphthalene loss rate, and difficulty in treating waste acid.

加氢精制法，萘的催化加氢多采用ai-co-mo催化剂，也有采用ai-ni-mo催化剂的。使萘中的硫?、苯甲腈、?、酚等杂质转化成易于除去的物质加以分离。需指出的是在萘加氢净化过程中，不希望生产四氢化萘，选择适当的加氢净化制度可以将四氢化萘的生成限制在0.3％以下（占加氢精萘）。萘的加氢精制主要用于生产低硫萘，这种萘用于流化床生产邻苯二甲酸酐，可避免催化剂中毒，另外也适用千生产二萘酚、甲萘胺、h酸及苯胺染料中间体等化主产品，投资大、危险性大。

In the hydrogenation refining method, the catalytic hydrogenation of naphthalene is mostly carried out using ai co mo catalysts, and there are also cases where ai ni mo catalysts are used. Make sulfur in naphthalene Benzonitrile Phenols and other impurities are converted into easily removable substances for separation. It should be pointed out that in the process of naphthalene hydrogenation purification, it is not desired to produce tetrahydronaphthalene. Choosing an appropriate hydrogenation purification system can limit the generation of tetrahydronaphthalene to below 0.3% (accounting for hydrogenated naphthalene). The hydrogenation refining of naphthalene is mainly used to produce low sulfur naphthalene, which is used in fluidized bed production of phthalic anhydride to avoid catalyst poisoning. In addition, it is also suitable for the production of main chemical products such as naphthalene, methylnaphthylamine, H-acid, and aniline dye intermediates, with high investment and high risk.

升华法，萘在远低千沸点时已具有较高的蒸汽压。蔡蒸汽冷却时可不经过液相直接凝结成固体。利用此性质，使原料中的萘与高沸点油类杂质分离，而得到纯度高的升华萘，此法在现实生产中采用较少。

Sublimation method, naphthalene already has a high vapor pressure at a much lower boiling point. When Cai steam is cooled, it can directly condense into a solid without going through the liquid phase. By utilizing this property, naphthalene in the raw material can be separated from impurities in high boiling oil to obtain high-purity sublimated naphthalene, which is less commonly used in practical production.

结晶法：结晶法分为熔融结晶法和溶剂结晶法。

Crystallization method: Crystallization method is divided into melt crystallization method and solvent crystallization method.

熔融结晶法是利用?与杂质在醇类中溶解度的差异使萘得到净化。溶剂结晶法使用的溶剂多数采用甲醇，甲醇足易燃易爆危险化学品，且有毒，危害很大，基本上很少采用熔融结晶法。

Is the melt crystallization method utilized? The difference in solubility between impurities and alcohols purifies naphthalene. The solvent used in solvent crystallization method mostly uses methanol, which is a flammable and explosive hazardous chemical and toxic, with great harm. Melt crystallization method is rarely used.

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