Raw material pretreatment: Phthalic anhydride must have a purity ≥98% and a water content ≤0.5% to reduce side reactions. The raw material needs to be dried at 100-120℃ for 2-4 hours.
Chlorination reaction: Add the raw material to the reactor, purge the air with nitrogen, raise the temperature to 80-100℃, and slowly introduce chlorine gas. The chlorine flow rate should be controlled at 0.5-1.0 m³/h, and the reaction time is 4-6 hours. Continuous stirring (200-300 rpm) and monitoring of the pH of the reaction solution are necessary (usually maintained at 2-3).
Cyclization and dehydration: After chlorination, transfer the reaction solution to a high-temperature reactor, raise the temperature to 250-280℃, maintain a vacuum below -0.08 MPa, and dehydrate for 2-3 hours. Strict temperature control is required during this stage to prevent product decomposition.
Post-treatment: After the reaction is complete, cool to below 100°C, wash with dilute hydrochloric acid (concentration 5-10%), filter, wash with deionized water until neutral, and finally dry at 80°C to constant weight.
