The purity of industrial naphthalene is required to be more than 95.5%, which is not acceptable if it is lower. Generally, refined naphthalene is used as raw material for phthalic anhydride produced by naphthalene process, which is more than 97%.

上世纪80年代开始由德国BASF公司开发的工业萘流化床法制苯酐，后来又开发出了邻二甲苯法制苯酐。萘法逐渐被取代，直到近几年，由于邻二甲苯价格高，原料不易采购，而工业萘原料充足，价格较低，加之新的工艺及专用催化剂的研制，使萘法苯酐工艺又热门起来！

In the 1980s, the industrial naphthalene fluidized bed process for phthalic anhydride was developed by BASF in Germany, and then the o-xylene process for phthalic anhydride was developed. Naphthalene process is gradually replaced. Until recent years, due to the high price of o-xylene, raw materials are not easy to purchase, while industrial naphthalene raw materials are abundant and low in price. In addition, new processes and the development of special catalysts have made naphthalene phthalic anhydride process popular again!

萘法苯酐，普遍采用的是固定床空气催化氧化法。催化剂有BASF的04-29专用催化剂和大连龙翔的催化剂。

Naphthalene phthalic anhydride generally adopts fixed bed air catalytic oxidation method. The catalysts include BASF's 04-29 special catalyst and Dalian Longxiang's catalyst.

工艺流程简单说有：

The process flow simply includes:

1、粗制苯酐：工业萘汽化，空气压缩，氧化反应，切换冷凝，尾气处理；

1. Crude phthalic anhydride: industrial naphthalene vaporization, air compression, oxidation reaction, switching condensation, tail gas treatment;

2、苯酐精制：预热，熟化，脱轻，苯酐精制，残渣处理；

2. Phthalic anhydride refining: preheating, maturing, delignification, phthalic anhydride refining, residue treatment;

3、锅炉系统：蒸汽系统和凝液系统。

3. Boiler system: steam system and condensate system.

4、还有苯酐结片包装等

4. Phthalic anhydride flake packaging

工业萘生产苯酐的方法，包括如下步骤：

The method for producing phthalic anhydride from industrial naphthalene includes the following steps:

1）工业萘在汽化器中加热完全汽化；

1) The industrial naphthalene is heated in the vaporizer and vaporized completely;

2）汽化的萘通过文丘里管进入萘－空气混合器，与反应空气充分混合；

2) The vaporized naphthalene enters the naphthalene air mixer through a venturi tube and is fully mixed with the reaction air;

3）充分混合的萘－空气混合气进入固定床气相催化反应器进行反应，得到苯酐。

3) The fully mixed naphthalene air mixture enters a fixed bed gas-phase catalytic reactor for reaction to obtain phthalic anhydride.