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%.

上世紀80年代開始由德國BASF公司開發的工業萘流化床法制苯酐，后來又開發出了鄰二甲苯法制苯酐。萘法逐漸被取代，直到近幾年，由于鄰二甲苯價格高，原料不易采購，而工業萘原料充足，價格較低，加之新的工藝及專用催化劑的研制，使萘法苯酐工藝又熱門起來！

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氣催化氧化法。催化劑有BASF的04-29專用催化劑和大連龍翔的催化劑。

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.

工藝流程簡單說有：

The process flow simply includes:

1、粗制苯酐：工業萘汽化，空氣壓縮，氧化反應，切換冷凝，尾氣處理；

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

2、苯酐精制：預熱，熟化，脫輕，苯酐精制，殘渣處理；

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

3、鍋爐系統：蒸汽系統和凝液系統。

3. Boiler system: steam system and condensate system.

4、還有苯酐結片包裝等

4. Phthalic anhydride flake packaging

工業萘生產苯酐的方法，包括如下步驟：

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

1）工業萘在汽化器中加熱完全汽化；

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

2）汽化的萘通過文丘里管進入萘－空氣混合器，與反應空氣充分混合；

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－空氣混合氣進入固定床氣相催化反應器進行反應，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.