Phthalate dimethyl ether (Diphenyl Ether) is a commonly used raw material for the production of chemicals, which is widely used in the fields of plastics, paints, spices, pharmaceuticals and so on. Its manufacturing methods are mainly as follows:
1. Sulfonation method
Sulfonation is one of the classic methods for manufacturing phthalic ether. The raw materials of this method are phthalic acid and sulfuric acid, and phthalic acid disulfonic acid is obtained through sulfonation reaction, and then phthalic dimethyl ether is obtained through esterification reaction with phenolic compounds. The specific steps are as follows:
(1) Mix phthalic acid with sulfuric acid and heat to 140-160°C for sulfonation reaction to produce phthalic acid disulfonic acid.
(2) Mix phthalic acid disulfonic acid with phenolic compounds (e.g., phenol), and heat to 180-220°C for esterification reaction to generate phthalic dimethyl ether.
The advantages of the sulfonation method are that the raw materials are readily available, the reaction conditions are milder, and the yield is higher. However, this method requires the use of a large amount of sulfuric acid, serious corrosion of equipment, large wastewater discharge, and greater pressure on environmental protection.
2. Catalytic oxidation method
Catalytic oxidation method is a relatively new method of manufacturing o-phthalic dimethyl ether. The raw material of this method is phthalonitrile, through catalytic oxidation reaction to get phthalic acid, and then with phenolic compounds for esterification reaction to get phthalic ether. The specific steps are as follows:
(1) Mix phthalonitrile with a solvent (e.g., acetic acid), add a catalyst (e.g., cobalt salt), and carry out a catalytic oxidation reaction at 120-150° C. to generate phthalic acid.
(2) Mix phthalic acid with a phenolic compound (e.g., phenol), add a catalyst (e.g., sulfuric acid), and carry out an esterification reaction at 180-220°C to produce phthalic ether. The advantages of the
catalytic oxidation method are milder reaction conditions, higher yields, and less wastewater discharge. However, this method requires the use of catalysts, higher requirements for equipment, and the price of raw material phthalonitrile is higher.
3. Etherification
Etherification is a direct synthesis method of phthalic dimethyl ether. The raw materials of this method are phenol and formaldehyde, and the phthalate dimethyl ether is obtained by etherification reaction. The specific steps are as follows:
(1) Mix phenol and formaldehyde in a certain proportion, add catalyst (such as hydrochloric acid or sulfuric acid), and carry out the etherification reaction at 80-120°C to generate o-anisodimethyl ether.
The advantages of the etherification method are that the raw materials are easy to obtain and the reaction steps are simple, but the yield is low, a large amount of catalyst is needed, and the wastewater generated contains formaldehyde and other harmful substances, so the pressure on environmental protection is high.
In summary, sulfonation method, catalytic oxidation method and etherification method are all methods for manufacturing o-anisole, and each method has its advantages and disadvantages. In the actual production, the suitable method can be chosen according to the specific situation. Meanwhile, in order to reduce the pressure of environmental protection and improve economic benefits, further research and improvement of manufacturing methods are needed to improve the yield and product quality.
