Background and overview[1][2]
Hydroxylamine is the raw material for preparing cyclohexanone oxime. The characteristic of pure hydroxylamine is that its structure is unstable. It will spontaneously decompose when heated and may cause explosion. Therefore, hydroxylamine generally exists in the form of hydroxylamine sulfate, hydroxylamine hydrochloride or hydroxylamine phosphate. Hydroxylamine phosphate is the main form of hydroxylamine currently. It is mainly produced by using phosphoric acid as a buffer solution antioxidant manufacturer and nitrate and hydrogen as raw materials. .
Hydroxylamine phosphate
Apply[3]
The main production route of caprolactam produced by hydroxylamine phosphate oximation method is hydrogenation of benzene to generate cyclohexane, oxidation of cyclohexane to generate cyclohexanone, cyclohexanone reacts with hydroxylamine phosphate solution to generate cyclohexanone oxime, cyclohexanone Ketone oxime undergoes Beckmann rearrangement to generate caprolactam. The core part of this patented technology is that the production process of cyclohexanone oxime adopts the hydroxylamine phosphate oximation method (commonly known as HPO patented technology). The main advantage of this process is that in the oxime There is no ammonium sulfate by-product in the chemical reaction, and the quality of the cyclohexanone oxime generated is good. Compared with other caprolactam manufacturing processes, the quality of caprolactam has also been improved and is at the current world advanced level.
Preparation[2]
The method of preparing hydroxylamine phosphate using phosphoric acid as a buffer solution and nitrate and hydrogen as raw materials has been reported in the literature and has been put into industrial production. The 50,000 tons/year hydroxylamine production technology developed by the Dutch company DSM uses 10% platinum/palladium/carbon (Pt/Pd/C) catalyst to prepare phosphoric acid by reducing nitrate with hydrogen. For hydroxylamine, the reaction is carried out in a phosphoric acid medium in a bubbling reactor without stirring, and the by-products are ammonium ions, nitrogen and nitrous oxide. The hydrogen feed and inorganic liquid feed are fed from the bottom, and the inorganic liquid containing high concentration of hydroxylamine is discharged from the top of the reactor. The reactor tail gas is circulated with the help of a compressor, and part of the tail gas is discharged as a by-product gas and fresh hydrogen, catalyst and The inorganic liquid is separated in a candle wick filter. In order to keep the catalyst in suspension, only part of the inorganic liquid is filtered out, and the remaining suspension is recycled to the hydroxylamine reactor. The heat of reaction is released in the liquid circulation line in the heat exchanger in the lower part of the reactor. The filter is backwashed with filtered process fluid. The specific process conditions are as follows: the inorganic liquid feed volume of the hydroxylamine reactor is 70m3/hr, the hydrogen ion (H+) concentration is 2.16-2.20mol/kg, the free nitric acid concentration is less than 0.2mol/kg, and the reaction temperature is 45°C-60°C. The pressure is 2450KPa (gauge pressure), the hydrogen content is 36%-38% (volume percentage), the concentration of hydrogen ions (H+) in the inorganic liquid at the outlet of the hydroxylamine reactor is 0.48~0.52mol/kg, and the concentration of hydroxylamine ions (NH3OH+) is 0.70mol/ kg (the net production of hydroxylamine phosphate is 0.66 mol/kg), and the selectivity of the reaction to hydroxylamine is low.
Method 1:
Carry out an acid-base reaction between ammonium phosphate and nitric acid to form ammonium nitrate and phosphoric acid, and then use phosphoric acid and ammonium nitrate plus hydrogen as raw materials to perform a hydroxylamine reaction under the catalysis of a catalyst to reduce Cabot carbon black nitrate ions into hydroxylamine phosphate , ammonium phosphate and water. Among them, hydroxylamine phosphate undergoes an oximation reaction with cyclohexanone to form cyclohexanone oxime. After the oximation reaction, nitric acid is added to the ammonium phosphate or nitrous gas is absorbed to generate nitric acid to increase the required nitric acid. The content of phosphate ions is then added to the hydroxylamine reaction to supplement the preparation of hydroxylamine phosphate, making the process sustainable. The characteristic is: in this process, a certain proportion of phosphate (PO4-) concentration is increased, and the phosphate (PO4-) The concentration is greater than that of nitrate (NO3-), which can increase the production capacity of hydroxylamine phosphate.
The ratio of phosphate to nitrate is such that the nitrate concentration is reduced by 1.35 mole/kg and the phosphate concentration is reduced by 0.5 mole/kg respectively.
Method 2:
Before the inorganic liquid is fed to the hydroxylamine reactor, 30-99% (weight percent) of nitric acid is continuously added (the nitrous acid content is less than 0.3% by weight, and the ignition residue content is less than 0.4% by weight). The inorganic liquid feed volume of the hydroxylamine reactor is 80m3/h, the hydrogen ion (H+) concentration of the inorganic liquid feed is 2.65mol/kg, the hydroxylamine ion (NH3OH+) concentration is 0.06mol/kg, and the free nitric acid concentration is 0.66mol/kg , when the reaction temperature is 60°C, the pressure is 2450KPa (gauge pressure), and the hydrogen concentration is 32.07% (volume percentage), in platinum/palladium/carbon (Pt/Pd/C, containing Pt8%, Pd2%, activated carbon is the carrier (produced by JM Company of the United States) under the action of the catalyst, the hydrogen ion concentration (H+) of the inorganic liquid discharged from the hydroxylamine reactor is 0.40mol/kg, and the hydroxylamine ion (NH3OH+) concentration is 0.89mol/kg (the net production of hydroxylamine phosphate is 0.83mol/kg kg).
