Phthalic Anhydride CAS 85-44-9

The primary response is received the number, additionally, benzoic acid, maleic anhydride, and so on are additionally produced by side reactions. The response is highly exothermic, so choice of appropriate stimulants (high activity as well as selectivity) and also removal of the warmth of response to reduce deep oxidation reactions are essential to commercial procedures. As a result, several production methods have been established. The commercial production method usually utilizes vanadium pentoxide-based vanadium-based drivers (see steel oxide catalysts) to accomplish the gas-phase oxidation of o-xylene. In 1974, a vanadium-based stimulant with a high-load surface layer was created, and the driver provider was inert non-porous ceramic balls, diamond balls as well as silicon carbide balls. The stimulant is prepared by using a ring service provider. This unique catalyst can minimize the deep oxidation reaction triggered by internal diffusion, consequently enhancing the return, selectivity as well as driver loading of phthalic anhydride. Most of the reactors utilize a tubular set bed.

The common process is that the filteringed system dust-free air is compressed and also preheated, blended with the evaporated o-xylene vapor, and after that enters the activator, and the oxidation response is performed at 400 ~ 460 ℃, and the feed area rate is 2000 ~ 3000h-1, the concentration of o-xylene airborne is 40 ~ 60g/m3 (standard), as well as the response warmth is brought out by the molten salt distributing outside television. The response product goes into the vapor generator, as well as the cooled reaction gas is further cooled down to recoup unrefined phthalic anhydride. The tail gas is washed with water to recover maleic anhydride and after that vented, or detoxified by catalytic combustion method and after that aired vent. Crude phthalic anhydride is rectified under vacuum to separate low-boiling maleic anhydride, methyl maleic anhydride as well as benzoic acid from the top of the tower; the bottom product is subjected to vacuum rectification to get phthalic anhydride items.

Naphthalene oxidation takes place at the α position, as well as under moderate problems, naphthalene is oxidized to create quinone. Under severe conditions, naphthalene is oxidized to develop phthalic anhydride. Side responses create naphthoquinone, maleic anhydride and so forth. The driver used is also a vanadium-based driver. The procedure is similar to o-xylene oxidation. There are 2 kinds of activators for naphthalene oxidation: tubular fixed bed and also fluidized bed. The heat of reaction in the fluidized bed reactor is removed by cooling pipelines inside the reactor. The particle dimension of the fluidized bed stimulant requires an ideal range, typically 40 ~ 300μm. The benefit of using a fluidized bed is that the reactor can be operated at a reasonably uniform temperature and a greater feed-air ratio, and also the item is less complicated to capture.

Refine of fluidized bed technique: First, naphthalene is merged fluid with steam, and then pumped right into the bottom of the oxidation heater having 0402 driver (V-K-Si collection), and the temperature is raised to 320 ~ 340 ° C, naphthalene is gasified and distributed. To the whole bed, the filtered and also detoxified air is fed right into all-time low of the reactor by the blower at a rate of 6000m3/h to ensure that the driver is in a fluidized state, as well as naphthalene is oxidized by air in the temperature level series of 360 ~ 385 ℃ to create phthalic anhydride. Gas, the air mixture consisting of phthalic anhydride gas is cooled by the condenser \ hot-melt condenser, the fluid gets in the unrefined phthalic anhydride tank, and also the obtained unrefined phthalic anhydride is heated up in a purification tower, treated with sulfuric acid, neutralized by sodium carbonate, and after that vacuum cleaner rectified as well as condensed., phase separation, crystallization and tableting to get the ended up item of pure phthalic anhydride, with a content of ≥ 99.7%.