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Uses and synthesis of Phthalic anhydride powder

Phthalic anhydride powder, abbreviated as phthalic anhydride, is an important chemical raw material. The most important use of phthalic anhydride in China is to produce phthalate plasticizers, followed by the production of alkyd resin and amino resin coatings; Phthalic anhydride powder can be used in the production of unsaturated polyester, and is used in the dyestuffs industry for the synthesis of anthraquinone.

Phthalic anhydride CAS 85-44-9 is an important organic chemical raw material for natural rubber, isoprene rubber, maleic rubber, styrene-butadiene rubber and nitrile rubber general-purpose anti-scorching agent, which can prevent scorching and improve the safety of operation. It has little effect on the positive vulcanization time and the aging performance of the products. Particularly effective in systems containing thiazole-guanidine and thiazole-tyulam accelerators and rubbers equipped with alkaline accelerators, but not applicable to tyulam sulfur-free vulcanization systems. Easily dispersed, no spray frost, not much pollution, but white rubber will also have a slight discoloration when exposed to light, generally should not be used for white rubber.Phthalic anhydride CAS 85-44-9 and sodium carbonate together with the high-promotion sponge products used in rubber, can increase the role of the foam.Phthalic anhydride Raw Materials the biggest uses The most important use of Phthalic anhydride Raw Materials is as an organic intermediate in the production of plasticizers, coatings and unsaturated polyester resins.

Applications / Functions of Phthalic anhydride powder

1. Phthalic anhydride powder is one of the most important organic chemical materials used in the production of plasticizers, alkyd resins, unsaturated polyester resins, dyes and pigments, pharmaceuticals and pesticides.
2. Phthalic anhydride Raw Materials is the intermediate of fungicide Sterilizer, insecticide Imidophos and herbicide Methomyl.
3. Phthalic anhydride CAS 85-44-9 is one of the most important organic chemical materials, its main derivatives are dibutyl phthalate, dioctyl phthalate and diisobutyl phthalate, etc. It is used as a plasticizer for PVC, etc. Phthalic anhydride CAS 85-44-9 is also used in the production of unsaturated polyester resins, alkyd resins, dyestuffs and pigments, It can also be used in the production of unsaturated polyester resins, alkyd resins, dyestuffs and pigments, many kinds of paints, food additives, phenolphthalein as laxative in pharmaceuticals, imidophos in pesticides, methomyl in pesticides and sodium saccharin.
4. Phthalic anhydride raw materials are used as analytical reagents and in organic synthesis.

Physicochemical Property of Phthalic anhydride powder

Phthalic anhydride Raw Materials Appearance is white needle crystal, relative density is 1.527, melting point is not less than 131.61℃, boiling point is 295.1℃. Can sublimate. Soluble in acetone, ethanol, slightly soluble in benzene and ether, insoluble in gasoline and water. It is converted to phthalic acid when it meets boiling water or acts with water for a long time. Stable in storage. Combustible. Dust-air mixtures are explosive, the lower limit of combustion mass concentration is 12.6g/cm3. deposited dust is fire hazard. Combustion temperature of the aerosol is 160°C, spontaneous combustion temperature 545°C. Toxic, limit allowable mass concentration is 1mg/m3.

Phthalic anhydride powder is white needle crystal with slight odor. Slightly soluble in hot water and ether, soluble in ethanol, benzene and pyridine.

production methodprocess of Phthalic anhydride powder

At present, there are two raw material routes of phthalic anhydride in industrial production, i.e. o-xylene method (referred to as o-phthalene method) and naphthalene method. There are three production processes: fixed-bed oxidation, fluidized-bed gas-phase oxidation and liquid-phase. The world phthalic anhydride production is dominated by the fixed-bed oxidation technology of o-phthalic anhydride, accounting for more than 80% of the total capacity of phthalic anhydride production.

1. o-Xylene oxidation method generally adopts vanadium catalyst based on vanadium pentoxide for the gas-phase oxidation of o-Xylene, and most of the reactors are tube-type fixed bed. The filtered dust-free gas is compressed, preheated, and mixed with gasified o-xylene vapor into the reactor at 400-460 ℃ for the oxidation reaction, the feed air velocity 2000-3000h-1, the concentration of o-xylene in the air is 40-60g/m2 (standard), and the heat of the reaction is carried out by the molten salt circulating outside the tube. The reaction product enters the vapor generator, and the cooled reaction gas is further cooled to recover crude phthalic anhydride. The tail gas is washed with water to recover maleic anhydride and then vented. The crude phthalic anhydride is distilled under reduced pressure, and low boiling point maleic anhydride, methyl maleic anhydride and benzoic acid are separated from the tower; the bottom material is distilled under vacuum to get Phthalic anhydride powder.Raw material consumption quota: o-xylene (98%) 1138kg/t.
2. Naphthalene catalytic oxidation method naphthalene melting gasification and air in the boiling bed or fixed-bed reactor, in the presence of catalyst vanadium pentoxide, catalytic oxidation of phthalic anhydride gas generated by condensation and hot melting of crude anhydride, through thermal treatment and then distillation under reduced pressure, condensation, separation of fine phthalic anhydride. Raw material consumption quota: naphthalene (more than 95%) 11250kg/t.

Its preparation method is catalytic oxidation by naphthalene or o-xylene, now most of the domestic has been used o-xylene oxidation, is described as follows.

• (1) Naphthalene oxidation method has a boiling bed and fixed bed method, the main domestic use of boiling bed. The process is: hot air into the boiling bed oxidizer equipped with vanadium catalyst (V2O5) to 300 ~ 340 ℃, the catalyst activation for several hours, and then the air into the oxidizer, the melted naphthalene sprayed into the oxidizer catalytic layer, the reaction temperature of 360 ~ 380 ℃, the reaction of phthalic anhydride produced by the top of the boiling bed of the filtration tube filtered out of the catalyst after the condenser multi-stage condensation, the exhaust gas and then by the water spray tower. Tail gas is then absorbed by the water spray tower, the hot oil will be sent to the finned tube of the hot melt condenser, phthalic anhydride melted into liquid, flowing into the storage tank that is crude, respectively, treated with concentrated sulfuric acid, sodium carbonate neutralization, and then distilled Phthalic anhydride CAS 85-44-9.
• (2) Phthalic anhydride oxidation method This method is divided into fixed bed method and boiling bed method (fluidized bed method).

① Fluidized bed method with vanadium a potassium an antimony oxide as the active component, with expanded silica gel as the carrier, made of powder catalyst, oxidation reaction in the fluidized bed, o-xylene and air in the gasifier mixed into the fluidized bed reactor, the reaction temperature of 365 ~ 380 ℃ under the reaction temperature.

② Fixed-bed method with vanadium pentoxide as the main vanadium catalyst, in the column tube fixed bed. The filtered dust-free air is compressed, preheated and mixed with gasified o-xylene vapor into the reactor, and the oxidation reaction is carried out at 400～460℃, the feed air velocity is 2000～3000h-1, the concentration of o-xylene in the air is 40～60g/m2, and the heat of the reaction is carried out by the circulating molten salt outside the tube. The reaction product enters the vapor generator, the cooled reaction gas is further cooled to recover the crude phthalic anhydride, the tail gas is washed to recover the maleic anhydride, the crude phthalic anhydride is roughly distilled by decompression, the top of the tower is fractionated out of the low-boiling maleic anhydride and so on, and the bottom of the tower materials are then distilled under vacuum to obtain the phthalic anhydride Phthalic anhydride CAS 85-44-9.

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