Method for producing phthallic anhydride
A technology of phthalic anhydride and ortho-xylene, which is applied in the field of gas-phase catalytic oxidation reaction for preparing phthalic anhydride, can solve the problems of decreased phthalic anhydride yield, increased content of irritating gas, and high content of ortho-xylene, and can reduce the The content of main impurity phthalide, the effect of overcoming irritation and improving product quality
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[0052] Example 1
[0053] It is a two-stage bed. The catalyst I and the catalyst III form a catalytic reaction system. In a reaction tube with an inner diameter of 25mm and a tube length of 4000mm, the upper bed is filled with catalyst I, the filling height is 1700mm, and the lower bed is filled with catalyst III. The filling height is 1500mm. The reaction heat is removed by forcing the molten salt in the outer jacket of the reaction tube to flow, and a multi-point thermocouple is used in the reaction tube to measure the reaction temperature.
[0054] The air flow is 4Nm 3 / h, the o-xylene concentration is 83g / Nm 3 When the salt bath temperature is 357°C, the yield of phthalic anhydride is 113%. The catalyst hot spot temperature is 430°C to 440°C, and the hot spot position is located at 500mm to 600mm from top to bottom in the catalyst bed. Through sampling and analysis, the content of phthalide in the reaction gas is 0.05%.
Example Embodiment
[0055] Example 2
[0056] It is a two-stage bed, and catalyst II and catalyst IV are combined to form a catalytic reaction system. The reaction device is the same as in Example 1. The upper bed is filled with catalyst I with a filling height of 1700 mm, and the lower bed is filled with catalyst III with a filling height of 1500 mm. The air flow is 4Nm 3 / h, the o-xylene concentration is 81g / Nm 3 When the salt bath temperature is 356°C, the yield of phthalic anhydride is 113%. The hot spot temperature of the catalyst is 430°C to 445°C, and the hot spot location is 500mm to 600mm from top to bottom in the catalyst bed. The phthalide content in the reaction gas is 0.05%.
Example Embodiment
[0057] Example 3
[0058]It is a three-stage bed, and catalyst I, catalyst II, and catalyst III are combined to form a catalytic system. The reaction device is the same as in Example 1. The upper bed is filled with catalyst I with a filling height of 1300 mm, the middle bed is filled with catalyst II with a filling height of 800 mm, and the lower bed is filled with catalyst III with a filling height of 1300 mm. The air flow is 4Nm 3 / h, the o-xylene concentration is 85g / Nm 3 When the salt bath temperature is 355°C, the yield of phthalic anhydride is 114%. The hot spot temperature of the catalyst is 440-450°C, and the hot spot is located at 500-600 mm from top to bottom in the catalyst bed. The phthalide content in the reaction gas is 0.05%.
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