Method and device for preparing adiponitrile

A method for preparing adiponitrile, the method comprising:

• step 1:
• subjecting hydrocyanic acid and butadiene to a first hydrocyanation reaction in the presence of a first catalyst to form a first stream comprising 3-pentenenitrile (3PN), 2-methyl-3-butenenitrile (2M3BN), the first catalyst, and butadiene, detecting the concentration of the hydrocyanic acid in the system, and enabling a residual amount of the hydrocyanic acid in the final first stream to be less than 10 ppm and a molar ratio of a total amount of the hydrocyanic acid to the amount of butadiene in the first hydrocyanation reaction to be 0.75 to 1.0 by regulating a ratio of raw materials, a reaction temperature, a reaction residence time, or a combination of the above modes;
• step 2:
• subjecting the first stream obtained in step 1 to an isomerization reaction to obtain a second stream comprising a mononitrile containing 2-pentenenitrile (2PN), 3-pentenenitrile (3PN), and 4-pentenenitrile (4PN), an unreacted 2-methyl-3-butenenitrile (2M3BN), the first catalyst, and butadiene, detecting the amounts of 3-pentenenitrile (3PN) and 2-methyl-3-butenenitrile (2M3BN) in the reaction system, and enabling the ratio of 3-pentenenitrile (3PN) in the second stream to the mononitrile containing 2-pentenenitrile (2PN), 3-pentenenitrile (3PN), and 4-pentenenitrile (4PN) to be 0.8 or more by regulating the amount of the first catalyst, the reaction temperature, the reaction residence time, or the combination of the above modes;
• then, obtaining a stream containing 3-pentenenitrile (3PN) by a post-treatment step;
• step 3:
• subjecting the hydrocyanic acid, the stream containing 3-pentenenitrile (3PN) obtained in step 2, a second catalyst and a promoter to a second hydrocyanation reaction to obtain a third stream containing the 3-pentenenitrile (3PN), the second catalyst, the promoter, and a dinitrile component containing adiponitrile (ADN), 2-methylglutaronitrile (MGN), and 2-ethylsuccinonitrile (ESN), detecting the amounts of the second catalyst, the hydrocyanic acid residue and/or 3-pentenenitrile (3PN) residue in the system, and enabling a conversion rate of 3-pentenenitrile (3PN) to be 60% or more and the molar ratio of the total amount of the hydrocyanic acid to 3-pentenenitrile (3PN) in the second hydrocyanation reaction to be 0.60 to 1.0 by regulating the ratio of raw materials, the reaction temperature, the reaction residence time, or the combination of the above modes;
• and, obtaining an adiponitrile product by the post-treatment step;
• wherein an online Raman spectroscopy detection is adopted for the above detection;
• the first catalyst and the second catalyst are each independently selected from zero-valent nickel complexes containing phosphorus ligands and/or free phosphorus ligands;
• and
• the promoter is a Lewis acid.