METHOD FOR CONTINUOUS SYNTHESIS OF 4-NITROSOPHENOL Russian patent published in 2021 - IPC C07C201/00 C07C207/04 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for the continuous synthesis of 4-nitrosophenol by the interaction of sodium nitrite, phenol and sulfuric acid in an aqueous medium. The method includes the following stages a) -j). At stage a) by mixing in a turbulent mixer without air access, a reaction mixture is prepared containing the following components: liquid phenol, which is a liquid mixture of water and phenol containing 92.2 wt.% С₆Н₅ОН phenol and 7.8 wt.% Н₂О water; 75-85 wt.% solution of sulfuric acid H₂SO₄, and the amount of supplied H₂SO₄is 0.7-0.9 mol per 1 mol of supplied C₆H₅OH; working solution containing sodium nitrite NaNO₂, supplied from stage k), wherein the total amount of С₆Н₅ОН in the specified feed circulating solution is 3.0-4.0 mol of NaNO₂per 1 mol of fed С₆Н₅ОН. In step b), the reaction mixture obtained in step a) is fed into a reactor. At stage c) nitrosation of phenol is carried out in a reactor in an inert gas atmosphere at an inert gas overpressure of 20-50 kPa, a temperature of 0-5°C and pH = 3.9-4.4. At stage d) the reaction mixture formed during nitrosation at stage c) containing crystals of 4-nitrosophenol is continuously fed into an ascending stream of purified, deoxygenated and cooled to 0-5°С water, in which crystals of 4-nitrosophenol are washed from occluded impurities, and the washed crystals of 4-nitrosophenol are separated from the first liquid phase, which is a mixture of said mother liquor and washing solution. At stage e), the first liquid phase from stage d) is passed through a layer of a sorbent, which is a mesoporous material containing cavities or channels with a diameter in the range from 2 to 50 nm, to purify the solution from reaction by-products to obtain a purified solution. At stage f) the purified solution from stage e) with pH = 3.9-4.4 is neutralized with caustic soda to pH = 6-9 to obtain a neutralized solution. In step g), the neutralized solution from step f) is fed into a crystallizer. At stage h), solid sodium nitrite is dissolved in said neutralized solution in said neutralized solution, supplied in a stoichiometric amount at the rate of 1 mol of NaNO₂ per 1 mol of phenol С₆Н₅ОН supplied in stage a), and the dissolution is carried out in an atmosphere of inert gas at 0-5°C and pH = 6-9 with salting out the crystals of mirabilite Na₂SO₄⋅10H₂O. At stage i) the suspension formed during the dissolution of sodium nitrite at stage h) containing crystals of mirabilite Na₂SO₄⋅10H₂O in mother liquor is continuously fed into the ascending stream of purified water cooled to 0-5°C, in which crystals of Na₂SO₄⋅10H₂O are washed from occluded impurities; then washed crystals of Glauber's salt are separated from the second liquid phase, which is a mixture of the specified mother liquor and washing solution. At stage j) the second liquid phase from stage i) with sodium nitrite dissolved in it is continuously fed as a circulating solution to stage a).

EFFECT: proposed method allows to synthesize 4-nitrosophenol with a high degree of purity and high yield, to reduce consumption factors for raw materials, to reduce the amount of waste, and also to obtain a valuable by-product of the reaction - Glauber's salt - with high purity.

14 cl, 2 tbl, 2 dwg, 2 ex