Method and device for preparing phthalic anhydride by virtue of naphthalene method and prepared phthalic anhydride

Abstract

The invention provides a device for preparing phthalic anhydride by virtue of a naphthalene method, belonging to the technical field of fine chemical engineering. The device comprises a naphthalene evaporator, a vaporizer and a reactor, wherein the naphthalene evaporator is connected with the vaporizer, and the vaporizer is connected with the reactor. The invention further provides a method for phthalic anhydride by virtue of the naphthalene method. The method comprises the following steps: adding liquid-state naphthalene into the naphthalene evaporator, heating liquid-state naphthalene to generate vapor-state naphthalene, when deltaP is equal to Pevaporator-Pvaporizer, namely 5Kpa-30Kpa, respectively introducing liquid-state naphthalene and air into the vaporizer to be mixed, so as to generate vapor-state naphthalene-air mixed gas, wherein Pevaporator represents the pressure in the naphthalene evaporator, and Pvaporizer represents the pressure in the vaporizer; and introducing vapor-state naphthalene-air mixed gas into the reactor for reaction, so as to generate phthalic anhydride. According to the method, the feeding controllability is improved, and the safety risks are lowered. The invention further discloses phthalic anhydride prepared by virtue of the method.

Description

technical field [0001] The invention relates to the technical field of fine chemicals, in particular to a method and a device for preparing phthalic anhydride by a naphthalene method, and the prepared phthalic anhydride. Background technique [0002] Phthalic anhydride, referred to as phthalic anhydride, is a cyclic anhydride formed by intramolecular dehydration of phthalic acid. Phthalic anhydride is an important raw material in chemical production, often used in the production of plasticizers, unsaturated resins and coatings. [0003] The production methods of phthalic anhydride mainly include naphthalene method and o-diphenyl method. The naphthalene method is a method for preparing phthalic anhydride proposed by the German Baden Aniline Soda Ash Company (now BASF AG) in 1896. The naphthalene method uses naphthalene as a raw material, and the gaseous naphthalene is mixed with air and then passed into the reactor. Catalysts react to form phthalic anhydride. The o-dipheny...

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Problems solved by technology

[0005] This pressure-stabilized feeding method needs to discharge the gaseous naphthalene generated at the initial stage of heating liquid naphthalene to the naphthalene slag tank 140, which wastes raw materials and increases costs.

It needs to raise the temperature inside the naphthalene evaporator 100 to about 235°C, and then pass the gaseous naphthalene vapor into the vaporizer 110 to mix with air to form a gaseous naphthalene-air mixture, but at this time the naphthalene evaporator The pressure in the naphthalene evaporator 100 reaches about 65Kpa, and the pressure difference between the naphthalene evaporator 100 and the vaporizer 110 reaches 30Kpa, the pressure in the naphthalene evaporator 100 is much higher than the pressure in the vaporizer 110, and the gaseous naphthalene enters the vaporizer from the naphthalene evaporator 100 The instantaneous flow rate at 110 is extremely high, so that the naphthalene vapor enters the vaporizer 110 and enters the reactor 130 before it is evenly mixed with the compressed air, which will not only affect the progress of the reaction, but also reduce the yield of phthalic anhydride, and in serious cases will cause local reactions in the reactor 130 The heat release is too violent and the phenomenon of flying temperature occurs, which has great potential safety hazards

Simultaneously, because the reaction that naphthalene catalyzes to generate phthalic anhydride is an exothermic reaction, and the temperature of the gaseous naphthalene-air mixed gas that is passed into the reactor 130 is relatively high, it is easy to make the reaction hot spots in the reactor 130 rise rapidly, reducing the reaction rate. The service life of the catalyst in the device 130 and the reactor 130

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