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[Chemical Knowledge]：Production process and preparation method of acrylonitrile

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Acrylonitrile is an important organic chemical raw material with wide application and market demand. Its main uses include the manufacture of synthetic fibers, synthetic resins, coatings, rubber, adhesives, etc., so the production process and preparation method of acrylonitrile in industrial production is particularly important.

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At present, the production process of acrylonitrile mainly includes propylene cyanide method and propylene oxidation method. Among them, the propylene oxidation method mainly converts propylene into acrylonitrile through oxidation reaction, while the propylene cyanidation method is to react propylene with cyanide in the presence of sodium hydroxide to produce acrylonitrile. Below we will introduce the production process and preparation method of these two kinds of acrylonitrile respectively.

1. propylene oxidation
propylene oxidation method is the oxidation reaction of propylene and ammonia in the presence of a catalyst to produce acrylonitrile. The catalyst is usually a copper-chromium-aluminum catalyst, the reaction temperature is about 250 ° C., and the reaction time is several hours.
The specific reaction mechanism is as follows:
propylene is first partially oxidized to acrolein or acrylic acid under the action of a catalyst. Then, ammonia gas is fed into the reaction system, and the ammonia gas reacts with acrolein or acrylic acid to produce the corresponding amide compound. Finally, the amide reacts further and dehydration occurs to form acrylonitrile.
The process of propylene oxidation is relatively simple, and the purity of the reaction product is high, but the reaction conditions are relatively harsh, and the catalyst, temperature and pressure of the reaction need to be strictly controlled. In addition, the propylene oxidation method has certain requirements on the reaction equipment, and it is necessary to use materials with high corrosion resistance, such as stainless steel, titanium alloy, etc.

2. propylene cyanidation
propylene cyanidation process is the direct conversion of propylene to acrylonitrile through cyanidation reaction. Reaction conditions are generally propylene and cyanide in alkaline medium reaction, the formation of ammonium cyanide propylene, and then after heating decomposition of ammonia to obtain acrylonitrile.
The main reaction equation of propylene cyanidation method is:
CH2 = CHCNH2OH → CH2 = CHCNH2CN + H2O
CH2=CHCNH2CN → CH2=CHCN + NH3
the mass ratio of propylene, ammonium cyanide and sodium hydroxide in the reaction is 1:1.4:1.4, the reaction temperature is 70-80 ° C., and the reaction time is 6-8 hours.
The propylene cyanidation method has the advantages of easy access to reactants, low production cost, and large-scale industrial production, but the purity of the product is low, and further purification is required. At the same time, the reaction needs to heat the reactor and strictly control the reaction conditions.

The production process and preparation methods of acrylonitrile are varied, of which propylene oxidation and propylene cyanide are the two most commonly used processes. Different production processes and preparation methods have different requirements for product purity and production capacity, and manufacturers should choose flexibly according to demand.

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