O-xylene (OX) is an important chemical raw material, widely used in the production of phthalic anhydride, polyester fiber, unsaturated polyester resin and other fields. The following are several common manufacturing methods of o-xylene:
1. Toluene Disproportionation
Toluene disproportionation is a commonly used method to produce o-xylene, which involves disproportionation of toluene to form benzene and xylene under the action of an acidic catalyst, and then o-xylene is obtained by separation. Commonly used acid catalysts include alumina, silicoaluminate, and aluminum phosphate. The method has a high reaction temperature, which needs to be carried out at 350-450°C, and factors such as reactor pressure and air velocity need to be controlled to ensure that the reaction proceeds and the selectivity of the products. The advantage of toluene disproportionation method is that the raw material is easy to obtain and the operation is simple, but the selectivity of o-xylene is low, and it needs to be purified by distillation and other means of separation.
2. o-Xylene selective oxidation
O-Xylene selective oxidation is a method of producing phthalic anhydride by direct oxidation of o-Xylene, which is based on the principle of oxidizing o-Xylene with air or oxygen to produce phthalic anhydride and water in the presence of a catalyst. Commonly used catalysts for this method include vanadium, titanium, zirconium and other metal oxide catalysts. The reaction temperature is generally between 350-450°C and the reaction pressure is 0.1-1.0 MPa. The advantage of this method is that the phthalic anhydride product can be obtained directly, avoiding the step of separation and purification, but the activity and selectivity of the catalyst have a large influence on the reaction, and the catalyst needs to be replaced periodically.
3. Aromatic conversion method
Aromatic conversion method is a method to produce o-xylene through aromatic conversion reaction. The method involves the conversion of aromatic compounds (e.g., ethylbenzene, propylbenzene, etc.) to products such as o-xylene under high temperature, high pressure, and a catalyst. Commonly used catalysts include molecular sieves, alumina, and aluminum phosphate. The reaction temperature is generally between 400-600°C and the reaction pressure is 2-10 MPa. The advantage of this method is that it can produce high-value o-xylene from low-value aromatic compounds, but the reaction conditions and catalysts are more demanding and need to be strictly controlled.
Regardless of which method is used to manufacture o-xylene, there is a need to strictly follow safe production practices to ensure the normal operation of the reactor and the health and safety of employees. It is also necessary to pay attention to environmental protection and take effective measures for exhaust gas and wastewater treatment to reduce the pollution to the environment.
