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[Chemical Knowledge]：Production process and preparation method of acetic anhydride (acetic anhydride)

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Acetic anhydride (acetic anhydride) is an important organic chemical raw material, widely used in dyes, pharmaceuticals and plastics industries. The production process and preparation method of acetic anhydride (acetic anhydride) will be described in detail below.

1. Production Process

Generally, acetic anhydride (acetic anhydride) is produced by catalytic oxidation of acetic acid. This catalytic oxidation method is a method of converting acetic anhydride (acetyl anhydride) by an oxidation reaction carried out in oxygen at an appropriate temperature using a suitable catalyst (such as metal tungsten, vanadium, chromium, etc.).

under the action of the catalyst, oxygen is taken from the air, and then reacts with acetic acid to form acetic anhydride. After acetic anhydride is produced, it is easily separated from the gas because it is lighter than acetic acid. At this point the anhydride gas is collected and purified to achieve a certain purity of the finished anhydride.

2. preparation methods

There are many methods for preparing acetic anhydride, and two more common methods are described below.

(1) Ethyl acetate method

Ethyl acetate as raw material, first in the role of suitable catalyst will be hydrolyzed into acetic acid and ethanol. The resulting ethanol and acetic acid are then combined together under dehydration conditions to produce acetic anhydride. The

reaction formula is:

C4H8O2 O2 ====> C4H6O3 H2O

(2) blast method

This method mainly uses the air and reaction powder in the blast furnace to play a catalytic role. Oxygen was introduced in a blast furnace to form chromium trioxide from the reaction powder. Next, chromium trioxide is reacted with oxygen and ethyl acetate in the gas phase to produce acetic anhydride.

reaction formula is:

C4H8O2 O2 3Cr2O3 ====> C4H6O3 6Cr2O2

Both of the above two methods have a problem, that is, they all need to use some environmentally unfriendly chemicals, such as compressed air in blast furnaces, oxygen, etc. Therefore, in order to better protect the environment, the first method is often used in industrial production for acetic anhydride production.

Generally speaking, acetic anhydride (acetic anhydride) is an organic chemical raw material widely used in the chemical industry, and its production process and preparation methods are also various. Enterprises can make reasonable choices according to the characteristics of the selected production process and preparation method and whether it meets the requirements of environmental protection, so as to reduce production costs and environmental pollution as much as possible.