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    Home > Chemicals Industry > Chemical Technology > Product performance and technical formula of salicylic acid

    Product performance and technical formula of salicylic acid

    • Last Update: 2021-08-15
    • Source: Internet
    • Author: User
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    Salicylic acid (salicylic acid), also known as 2-hydroxybenzoic acid (2-hydroxyl benzoic acid), salicylic acid , salicylic acid , Shali Xi acid, sprinkle acid, of the formula C .
    7
    H .
    6
    O .
    3
    , a molecular weight of 138.
    1 , The structural formula is

    1.
    Product performance

    White needle-like crystal or crystalline powder, with a spicy taste; melting point 158~161℃, boiling point 211℃ (2.
    6664kPa), sublimation at 76℃; relative density (d
    4 20 ) 1.
    443; flammable; low toxicity; in air It is stable in medium, but gradually changes color when exposed to light; slightly soluble in water, soluble in acetone, turpentine,
    ethanol , ether , benzene and chloroform, its aqueous solution is acidic; it produces a special purple color with aqueous ferric chloride solution
    .

    2.
    Production principle

    After phenol and caustic soda form a salt, it undergoes carboxylation reaction with carbon dioxide , and then acidifies to obtain salicylic acid
    .

    3.
    Process flow

    4.
    Technical formula (kg/t)


    5.
    Main equipment

    Salt carboxylated gold, water separator, acid precipitation pot, sublimation kettle, condenser, cooling tower, centrifuge, refining kettle (stainless steel)
    .

    6.
    Production process

    (1) Salt formation and carboxylation
    .
    Put 100kg of phenol (98%) into the cast iron reactor and stir, add 86kg of 50% sodium hydroxide solution, and take samples after 0.
    5h reaction

    .
    The measured free base should be 1% (if the free base exceeds 1%, it needs to be supplemented to balance)

    .
    Distill water at atmospheric pressure for 2h, stir, and then dehydrate under reduced pressure at 170℃/(20~160)×133.
    3Pa for 1~1.
    5h, and then add 100kg of phenol as a solvent for azeotropic dehydration

    .
    When the internal temperature rises to 128°C/160×133.
    3Pa, the reduced pressure azeotropic dehydration is completed

    .
    Sodium phenate was carboxylated in 100 kg of solvent phenol, and CO
    2 was introduced for 3 hours, and the internal temperature was raised from 128°C to 200°C
    .
    When the temperature drops, start to recover phenol under reduced pressure, pass CO
    2 for the second time after 2 to 3 hours , carboxylate for 2 hours, then recover phenol under reduced pressure for 1 to 2 hours, and the carboxylation is completed
    .
    Add water to dissolve, get 50% sodium salicylate solution

    .

    (2) Acid precipitation
    .
    Under stirring, add about 1000 kg of 7% to 8% sulfuric acid solution to the 50% sodium salicylate solution generated above to make the pH 1-2

    .
    After cooling to below 30°C, centrifugal filtration and vacuum drying, 63kg of crude salicylic acid was obtained

    .

    (3) Sublimation
    .
    The crude salicylic acid is added to the sublimation tank, and the sublimation is carried out at 150~170℃/20×133.
    3Pa under reduced pressure

    .
    The sublimation tower is cooled by atmospheric pressure water, and the salicylic acid vapor enters the tower for cooling, and 60kg of sublimation salicylic acid is obtained

    .

    (4) Refined
    .
    Put 60kg of sublimated salicylic acid, 360L of water, and 0.
    36kg of phosphoric acid into a stainless steel refining tank in turn, stir and raise the temperature to 90°C, keep it for 1h, lower the temperature to 35°C, filter, and vacuum dry to obtain 58kg of salicylic acid

    .

    7.
    Laboratory preparation method

    Dissolve 47 g of phenol in 20.
    5 g of NaOH and 30 mL of water in a nickel evaporating dish, and heat on an asbestos net to prepare powdered sodium phenate

    .
    Add the powdered sodium phenate to a 250mL three-necked bottle, heat the oil bath to 110°C, and start to pass in the CO
    2 after being washed by the sulfuric acid bottle and the silica gel column .
    The CO
    2 tube should be directly connected to the surface of the sodium phenate
    .
    After ventilation for 1 hour, the temperature was gradually increased, and the temperature rose to 190°C within 4 hours

    .
    Heat at 200°C for another 2h

    .
    After the reaction product is cooled, it is dissolved by adding water, and then 1 g of activated carbon is added

    .
    Heat at 60°C for 15 min and then hot filter

    .
    Concentrated hydrochloric acid was added to the filtrate to precipitate salicylic acid

    .
    Crystallize in an ice-salt bath and filter with suction to obtain a crude product

    .
    Then recrystallize with water

    .
    The pure product has a melting point of 156°C

    .

     

     

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