RU2257340C1 - Hydroxylamine sulfate preparation process - Google Patents

Abstract

FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to preparation of hydroxylamine sulfate used in caprolactam production. Process consists in catalytic steam-oxygen oxidation of ammonia and synthesis of hydroxylamine sulfate both carried out under elevated pressure (above 0.25 MPa), pressure in the steam-oxygen oxidation stage being higher than then in hydroxylamine sulfate synthesis stage by a value equal to aerodynamic resistance of equipment and pipelines installed between the two stages. Nitrose gas obtained after steam-oxygen oxidation stage is concentrated by condensing water vapors and freed of nitrogen dioxide, after which mixed with hydrogen for synthesis of hydroxylamine sulfate in dilute sulfuric acid solution. Nitric acid concentrate with 7-8.5% nitric acid releasing during concentration of nitrose gas is subjected to liquid-phase hydrogenation on platinum catalyst. Thus obtained pure nitrogen dioxide in mixture with hydrogen is sent to hydroxylamine sulfate synthesis stage and hydrogenation product containing up to 0.45% nitric acid is used to dilute concentrated sulfuric acid thereby providing wasteless technology.

EFFECT: simplified process flowsheet and automated process control, and reduced investment expenses of ammonia oxidation stage (by 65-70%).

3 cl, 2 dwg, 1 tbl

Description

The invention relates to the chemical industry, and in particular to a method for producing hydroxylamine sulfate (GAS) used in the production of caprolactam.

A known method of producing a HAS, including the preparation of a reaction mixture of ammonia, oxygen and water vapor, catalytic vapor-oxygen oxidation of ammonia, mixing the obtained nitrous gas with hydrogen, stabilization of nitrous gas by hydrogenation of excess oxygen in the presence of a silver-manganese catalyst, its two-stage concentration by condensation of water vapor, mixing concentrated nitrogen monoxide with hydrogen and the synthesis of hydroxylamine sulfate in dilute sulfuric acid. The condensate of the second stage of concentration of nitrous gas is hydrogenated with hydrogen in the presence of a platinum catalyst in the liquid phase. The resulting pure nitric oxide (II) is used for the synthesis of HAS, and the hydrogenation product with a mass fraction of nitric acid up to 0.45% together with the condensate of the first stage is used to dilute concentrated sulfuric acid, thereby ensuring a waste-free technology [EPO application No. 0945401, IPC ⁶ C 01 B 21/14, 1999].

The advantage of this method is the production of concentrated nitric oxide (II) and the disposal of industrial waste in the form of dilute solutions of nitric acid.

However, when the composition of nitrous gas is stabilized by hydrogenation of excess oxygen on a silver-manganese catalyst, nitrous oxide (II) is irretrievably lost and nitrogen and nitric oxide (I) are formed, which reduce the efficiency of the GAS synthesis stage.

The closest to the claimed invention in technical essence and the achieved effect is a method comprising preparing a reaction mixture of ammonia, oxygen and water vapor, catalytic vapor-oxygen oxidation of ammonia, mixing the obtained nitrous gas with hydrogen, stabilization of nitrous gas by hydrogenation of excess oxygen on a silver-manganese catalyst on 70-75%, its two-stage concentration by condensation of water vapor, the mixing of concentrated nitric oxide (II) with hydrogen and the synthesis of hydro ilaminsulfata in dilute sulfuric acid medium.

A significant difference between this method of producing GAS from the above is that at the stage of stabilization of nitrous gas, excess oxygen is hydrogenated by 70-75% instead of 90%. As a result of this, a condensate is formed in the second stage of concentration of nitrous gas, containing 1.5-2.5 times more nitric acid than in the above method. During its liquid-phase hydrogenation, correspondingly, more pure nitric oxide (II) is formed. In addition, when hydrogenation of excess oxygen by 70-75% during the stabilization of nitrous gas, nitric oxide (II) is practically not lost, and, therefore, additional inert impurities are not formed, and the volume fraction of nitric oxide (II) in concentrated nitrous gas is 2 , 3-2.5% more than in the above method [declaration patent of Ukraine No. 50681A, IPC ⁷ C 01 B 21/14, 2002].

A common drawback of both of the above methods is the complexity of the scheme as a whole, which includes both the stage of stabilization of the composition of nitrous gas by hydrogenation of a part of the excess oxygen and the stage of liquid-phase hydrogenation of the condensate of the second stage of concentration of nitrous gas. In addition, the scheme is characterized by a strict relationship between the stages of ammonia oxidation and synthesis of HAC, due to the need to compress nitric oxide (II), which complicates the automatic process control.

In order to eliminate the stage of compression of nitrous gas, the catalytic oxidation of ammonia is carried out at elevated pressure up to 0.4 MPa [Atroshchenko V.I., Cherkashin V.N., Ushakova N.M., Kleschev N.F. Izv. University of the USSR. “Chemistry and chemical technology”, 1978, v.21, issue 6, p.868-870]. This simplifies the coordination of the stages of the oxidation of ammonia and the synthesis of GAS and automatic process control, significantly reduced capital costs.

However, in the case of vapor-oxygen catalytic oxidation of ammonia under increased pressure to 0.4 MPa, the yield of nitric oxide (II) decreases by 1-1.5% and accordingly, more inert impurities are formed, which increases the cost of raw materials for the manufacture of the product and reduces the performance of the GAS synthesis stage.

The aim of the present invention is to improve the method of producing GAS by changing the parameters of the process and technological scheme so as to reduce capital and specific costs for the manufacture of the product, as well as to simplify the regulation and control of the process.

The problem is solved in that in the method of producing hydroxylamine sulfate, including the preparation of a reaction mixture of ammonia, oxygen and water vapor, according to the invention, the catalytic vapor-oxygen oxidation of ammonia and the synthesis of HAC are carried out under increased pressure of more than 0.25 MPa, while the pressure of the ammonia oxidation stage exceeds the pressure of the HAS synthesis stage by an amount equal to the aerodynamic resistance of the equipment and pipelines of the gas path between the stages, the nitrous gas is concentrated by condensation and water vapor purified of impurities of nitrogen oxide (IV), mixed with hydrogen and synthesize hydroxylamine in dilute sulfuric acid medium, HAS synthesis performed under pressure above 0.25 MPa. The nitric acid condensate released during the concentration of nitrous gas, with a mass fraction of nitric acid of 7-8.5%, is subjected to liquid-phase hydrogenation in the presence of a platinum catalyst. The resulting pure nitric oxide (II) in a mixture with hydrogen is sent to the GAS synthesis stage, and the hydrogenation product with a mass fraction of nitric acid up to 0.45% is used to dilute concentrated sulfuric acid, thereby providing a waste-free technology.

The method is as follows.

The reaction mixture of ammonia, oxygen and water vapor prepared in mixer 1 is sent to reactor 2, where ammonia is oxidized with oxygen to nitric oxide (II) under a pressure of more than 0.25 MPa (for example, 0.3-0.35 MPa). The heat of the ammonia oxidation reaction is used to produce steam by cooling the nitrous gas in the boiler part of the reactor 2. The obtained nitrous gas is concentrated by condensing water vapor in the heat exchanger 3, it is cleaned of nitrogen oxide (IV) impurities, washing with a portion of the nitric acid condensate in the apparatus 4, is mixed with hydrogen in the mixer 5 and sent to the cascade of reactors 6, where in a medium of diluted sulfuric acid, GAS is synthesized under a pressure of more than 0.25 MPa. The nitric acid condensate with a mass fraction of nitric acid of 7-8.5% is sent to the reactor 7, where in the presence of a platinum catalyst hydrogenated with hydrogen. The resulting mixture of pure nitric oxide (II) and hydrogen is mixed with the main stream of concentrated nitric oxide (II). The hydrogenation product with a mass fraction of nitric acid up to 0.45% is sent to a mixer 8 for dilution of concentrated sulfuric acid. Waste gases from the cascade of reactors 6 for the synthesis of gas are sent to a regenerative and ecological installation 9.

The inventive method of producing a GAS is illustrated by the scheme shown in figure 1, and, for comparison, figure 2 presents a diagram of a GAS of the prototype.

The table shows data illustrating the operation of the installation according to the claimed method and, for comparison, the prototype.

From the above data, it follows that despite a decrease in the degree of oxidation of ammonia to nitric oxide (II) and an increased formation of inert impurities at the stage of ammonia oxidation, the total fraction of nitric oxide (II) in the gas entering the stage of synthesis of HAC decreases slightly, and accordingly, slightly decreases the performance of the stage of synthesis of GAS. But at the same time, the process scheme and automatic regulation are significantly simplified, and the capital costs at the stage of ammonia oxidation are reduced by 65-70%.

Claims (3)

1. A method of producing hydroxylamine sulfate (GAS), including the preparation of a reaction mixture of ammonia, oxygen and water vapor, catalytic oxidation of ammonia, concentration of nitrous gas by condensation of water vapor, hydrogenation of nitric acid condensate, purification of concentrated nitrous gas from impurities of nitric oxide (IV), mixing it with hydrogen, a mixture of sulfuric acid, water and a hydrogenation product of nitric acid condensate, the synthesis of hydroxylamine sulfate, characterized in that the catalytic vapor-oxygen Ammonia oxidation and hydroxylamine sulfate synthesis are carried out under a pressure of more than 0.25 MPa, while the pressure of the ammonia oxidation stage exceeds the pressure of the HAS synthesis stage by an amount equal to the aerodynamic resistance of the equipment and pipelines of the gas path between the stages. 2. The method according to claim 1, characterized in that the concentration of nitrous gas is carried out in one stage, using all excess oxygen to produce nitric acid. 3. The method according to claim 2, characterized in that the nitric acid condensate is subjected to liquid phase hydrogenation in the presence of a platinum catalyst, the resulting pure nitric oxide (II) is used to produce HAC, and the hydrogenation product with a mass fraction of nitric acid up to 0.45% is used for dilution concentrated sulfuric acid.

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