Preparation method of hydroxylamine sulfate

Abstract

The invention discloses a hydroxylamine sulfate preparation method, which comprises: S1, carrying out analysis on caprolactam sulfate with water or a hydroxylamine sulfate aqueous solution to obtain a caprolactam sulfuric acid aqueous solution; extracting and separating the caprolactam sulfuric acid aqueous solution by using an extracting agent, conveying an extraction phase caprolactam organic solution to a caprolactam device for treatment, and entering a step S2 into a raffinate phase sulfuric acid aqueous solution or hydroxylamine sulfate and sulfuric acid aqueous solution; s2, adding ketoxime and a sulfuric acid aqueous solution or hydroxylamine sulfate and the sulfuric acid aqueous solution to generate a hydrolysis reaction to generate a hydroxylamine sulfate aqueous solution and ketone, and after ketone separation, sending the ketoxime to a ketoxime preparation device; s3, carrying out steam stripping separation on the hydroxylamine sulfate aqueous solution, sending unreacted ketoxime to the step S2 to participate in a hydrolysis reaction, and carrying out concentration crystallization, centrifugal filtration and drying dehydration on the hydroxylamine sulfate aqueous solution to obtain hydroxylamine sulfate; and S4, returning part of hydroxylamine sulfate raffinate subjected to centrifugal filtration to the step S1 for resolving caprolactam sulfate, and carrying out oximation reaction treatment on the residual hydroxylamine sulfate raffinate and ketone.

Description

Technical Field

[0001] The present invention relates to the technical field of hydroxylamine sulfate, and particularly relates to a method for preparing hydroxylamine sulfate by hydrolysis of transester. Background Art

[0002] Caprolactam is one of the important organic chemical raw materials. Its main use is to generate polyamide chips (usually called nylon-6 chips or polyamide-6 chips) through polymerization, which can be further processed into polyamide fibers, engineering plastics, and plastic films.

[0003] The main production process of caprolactam is the hydroxylamine-cyclohexanone method. Using benzene as the raw material, caprolactam is prepared through cyclohexanone preparation, cyclohexanone oximation, and rearrangement of cyclohexanone oxime under the catalysis of fuming sulfuric acid to generate caprolactam. The rearrangement product is also called transester, that is, caprolactam sulfate. Due to the chemical bond combination between caprolactam and sulfuric acid, it is difficult to separate. Industrially, caprolactam sulfate almost always uses ammonia neutralization to generate caprolactam and ammonium sulfate for separation. This process has been used in caprolactam production. Its disadvantage is the large consumption of ammonia and fuming sulfuric acid with relatively high economic value, and the by-product of ammonium sulfate with relatively low economic value. For every 1 ton of caprolactam produced, 1.6 - 1.8 tons of ammonium sulfate will be by-produced, and the net loss of each ton of ammonium sulfate is 200 - 600 yuan / ton. The large by-production of ammonium sulfate leads to an increase in the production cost of caprolactam. How to improve the production process and reduce the output of ammonium sulfate has become one of the main problems in caprolactam production.

[0004] In order to reduce the by-production of ammonium sulfate in the production process of caprolactam, Sumitomo Corporation of Japan developed a caprolactam production technology without by-product ammonium sulfate, that is, gas-phase rearrangement. Under the action of a molecular sieve catalyst and a solvent, cyclohexanone oxime undergoes a rearrangement reaction at high temperature to turn cyclohexanone oxime into caprolactam. This process has no by-product ammonium sulfate, but the reaction conditions are harsh, and the selectivity of caprolactam is significantly lower than that of rearrangement with fuming sulfuric acid. Although this process has no by-product ammonium sulfate, it also has no cost advantage.

[0005] Hydroxylamine sulfate, also known as hydroxylamine sulfate and hydroxylamine sulfate, is an important intermediate, and its application fields include pesticide intermediates, pharmaceutical intermediates, and ore dressing agents, etc. In addition, hydroxylamine sulfate has extensive application value in industries such as oils and fats, industrial anti-corrosion, photography, dyes, and rubber. The global production capacity of hydroxylamine (including hydroxylamine sulfate and hydroxylamine hydrochloride) is about 88 kt / a. The main production enterprises are Jinhua, Aikewei, BASF, Ube of Japan, Zhejiang Sheng'an, etc. Hydroxylamine sulfate can be used in a variety of applications, such as pharmaceuticals, agrochemicals, and photography. Due to the increasing demand in these industries, the global market for hydroxylamine sulfate is expected to grow at a significant rate during the forecast period. China is one of the largest consumers of hydroxylamine sulfate and occupies a large share in the global market. Due to the increasing demand in the pharmaceutical and agrochemical industries, the market for hydroxylamine sulfate in China has been growing rapidly.

[0006] The synthetic routes and processes of solid hydroxylamine sulfate disclosed in the prior art at home and abroad mainly include the nitro-methane route, the nitration route of natural gas (methane), the acetone oxime route, the hydrolysis method of ammonium disulfonate, the nitric oxide reduction method, the production of hydroxylamine sulfate using trimethoprim wastewater, etc. However, the nitro-methane route has a low product yield, many types of by-products, and a large investment in separation equipment; the acetone oxime route has a relatively complex process, many types of raw materials, high unit consumption, and high costs; the production process of the disulfonate hydrolysis method is mature, but it is only suitable for large-scale production in large factories with a large investment cost. The other process routes have relatively low yields. In summary, factors such as large investment, many types of raw materials, high costs, low yields, and low product purity relatively restrict the product competitiveness of high-purity solid hydroxylamine sulfate.

[0007] Patent CN202310237385 proposes a method for co-producing caprolactam and hydroxylamine sulfate. It includes: (1) Ammonoximation reaction: Reacting a ketone with ammonia and hydrogen peroxide at a certain temperature under the action of a titanium-silica catalyst to produce an oxime solution; (2) Hydrolysis reaction: Adding an appropriate amount of demineralized water to caprolactam sulfate ester, stirring, controlling the hydrolysis temperature, and carrying out the hydrolysis reaction to obtain a hydrolyzed reactant, caprolactam sulfate solution; (3) Co-production reaction of caprolactam and hydroxylamine sulfate: Adding the oxime solution to the caprolactam sulfate solution, and reacting at a certain temperature and pressure to obtain a solution of caprolactam and hydroxylamine sulfate; (4) Physical separation: The reactant in step (3) is layered. The upper light phase is an organic solvent containing ketone, and the lower heavy phase is an aqueous phase containing hydroxylamine sulfate and caprolactam; (5) The organic solvent containing ketone is returned to step (1) for the ammonoximation reaction, or after removing the solvent, it is returned to step (1) for the ammonoximation reaction; the lower layer is subjected to sedimentation, centrifugal separation, and drying to obtain a crude caprolactam solution and hydroxylamine sulfate salt.

[0008] The yield of hydroxylamine sulfate obtained by this method is relatively low, and the highest in the examples is only 61%. Moreover, the co-production reaction temperature of caprolactam and hydroxylamine sulfate is between 98 and 120 °C, and the reaction time is 4 - 6 h. Since the corrosiveness of the caprolactam sulfate solution increases sharply with the increase in temperature, the requirements for the equipment material are extremely high, and the device investment is relatively high. Due to the low single-pass yield of hydroxylamine sulfate, the material consumption and energy consumption of the device are relatively high; the high co-production reaction temperature of the caprolactam sulfate solution will also cause a hydrolysis side reaction of caprolactam, resulting in a decrease in the caprolactam yield. The addition of an organic solvent needs to be recovered, which will also increase the energy consumption of the device.

[0009] Therefore, it is necessary to provide a new method for preparing hydroxylamine sulfate, which can improve the yield of hydroxylamine sulfate and reduce the production cost. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for preparing hydroxylamine sulfate, which can improve the yield of hydroxylamine sulfate and reduce the production cost.

[0011] To achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing hydroxylamine sulfate, which includes the following steps: S1: Analyze caprolactam sulfate with water or an aqueous solution of hydroxylamine sulfate to obtain an aqueous solution of caprolactam sulfate; extract and separate caprolactam from the aqueous solution of caprolactam sulfate with an extractant to obtain an aqueous raffinate sulfate solution or a hydroxylamine sulfate + sulfuric acid aqueous solution and an organic solution of caprolactam in the extract. The organic solution of caprolactam is transported to the caprolactam device for treatment, and the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution enters step S2; S2: Add ketoxime to the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution prepared in step S1. The ketoxime reacts with the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution to generate an aqueous solution of hydroxylamine sulfate and a ketone. The generated ketone is separated by a separator and sent to the ketoxime preparation device for recycling; S3: Strip the aqueous solution of hydroxylamine sulfate obtained in step S2 to separate a small amount of unreacted ketoxime and send it to step S2 to participate in the hydrolysis reaction. The aqueous solution of hydroxylamine sulfate is concentrated, crystallized, centrifugally filtered, and dried and dehydrated to obtain the product hydroxylamine sulfate; S4: Return a part of the hydroxylamine sulfate residue after centrifugal filtration in step S3 to step S1 for the analysis of caprolactam sulfate, and perform an oximation reaction treatment on the remaining hydroxylamine sulfate residue and the ketone.

[0012] Further, in step S1, the extractant is benzene. After extraction, a mixed solution of benzene and caprolactam enters the caprolactam device to recover the caprolactam product. The separated benzene is refined and then recycled to step S1 as an extractant to extract caprolactam from the aqueous solution of caprolactam sulfate.

[0013] Further, in step S1, the hydrolysis conditions of caprolactam sulfate are: temperature is 40 - 50 °C, pressure is atmospheric pressure; the mass ratio of the aqueous solution of hydroxylamine sulfate to caprolactam sulfate is 1 - 10, and the mass percentage content of hydroxylamine sulfate in the aqueous solution of hydroxylamine sulfate is: greater than 0 and less than or equal to 35%.

[0014] Further, the ketoxime added in step S2 is butanone oxime, and the ketone generated after hydrolysis is butanone. The butanone is sent to the butanone oxime device to produce butanone oxime, and the butanone oxime is recycled and sent back to step S2 to react with the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate.

[0015] Further, in step S2, in the hydrolysis reaction of butanone oxime and sulfuric acid, the temperature is 70 - 90 °C, the pressure is absolute pressure 20 - 40 kPa; the hydrolysis reaction time is 0.5 - 3.5 h, and the molar ratio of butanone oxime to sulfuric acid is 1 - 1.3.

[0016] Further, the ketoxime added in step S2 is cyclohexanone oxime, and the ketone generated after hydrolysis is cyclohexanone. The cyclohexanone is sent to the ammoximation unit of the caprolactam device to produce cyclohexanone oxime, which is used as a raw material for producing caprolactam or recycled to step S2.

[0017] Further, in step S4, 30-90% of the hydroxylamine sulfate residue after centrifugal filtration is returned to step S1 for the resolution of caprolactam sulfate, and the remaining hydroxylamine sulfate residue is transported to the oximation reactor for oximation reaction treatment with a ketone.

[0018] Further, in the oximation reactor, hydroxylamine sulfate reacts with a ketone to form a ketoxime and ammonium sulfate, which are separated by a separator.

[0019] Further, a small amount of ammonia water is added to the oximation reactor to adjust the pH value of the reaction mixture to 3-6. The reaction mixture overflows from the top of the oximation reactor into the separator, where the reaction mixture naturally settles and layers. The oil-phase ketoxime is sent to the ketoxime preparation device for purification treatment, and the water phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, and is sent to the ammonium sulfate unit of the caprolactam device for treatment.

[0020] Further, in step S4, the temperature of the oximation reaction between the hydroxylamine sulfate residue and the ketone is 40-70°C, and the pressure is atmospheric pressure; the molar ratio of the ketone to hydroxylamine sulfate is 1-1.2, and the mass ratio of the oil-phase ketoxime to the water-phase ammonium sulfate aqueous solution is 0.5-2.5.

[0021] The present invention has the following beneficial effects compared with the prior art: The preparation method of hydroxylamine sulfate provided by the present invention uses ketoxime and caprolactam sulfate as raw materials. After the caprolactam sulfate is first resolved with water or an aqueous solution of hydroxylamine sulfate to obtain an aqueous solution of caprolactam sulfate, caprolactam and the sulfuric acid aqueous solution are then separated by extraction. Caprolactam can be separated first at a lower temperature, thus avoiding the hydrolysis side reaction of caprolactam at high temperature, thereby increasing the caprolactam yield. The ketoxime reacts with the sulfuric acid aqueous solution to prepare hydroxylamine sulfate without the need to additionally add sulfuric acid. At the same time, the separated ketone is sent to the ketoxime preparation device for recycling. The production of caprolactam and the production of hydroxylamine sulfate are combined, reducing the by-product of ammonium sulfate. At the same time, caprolactam and hydroxylamine sulfate are produced, establishing a resource circulation comprehensive utilization industrial chain of caprolactam-ketoxime-coproduction of hydroxylamine sulfate, improving the comprehensive competitiveness of caprolactam products. At the same time, by separating caprolactam first and recycling the ketoxime, the sulfuric acid aqueous solution can fully react, increasing the yield of hydroxylamine sulfate and reducing the production cost. In addition, in the preparation of ketoxime, there is no need for a high conversion rate during the conversion of ketone to oxime, and the unreacted ketone can be recycled back to the oximation reactor for oximation reaction with the hydroxylamine sulfate residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart for the preparation of hydroxylamine sulfate in an embodiment of the present invention.

[0023] Figure 2Schematic diagram of the production system of hydroxylamine sulfate in the embodiments of the present invention.

[0024] Figure 3 Schematic diagram of the treatment device for the residual liquid of hydroxylamine sulfate in the embodiments of the present invention. Detailed implementation manners

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Please refer to Figure 1 , this embodiment provides a preparation method of hydroxylamine sulfate, which includes the following steps: S1: At a temperature of 40 - 50 °C and under normal pressure, caprolactam sulfate is resolved with water or an aqueous solution of hydroxylamine sulfate to obtain an aqueous solution of caprolactam sulfate; caprolactam is extracted and separated from the aqueous solution of caprolactam sulfate with an extractant to obtain an aqueous sulfuric acid solution in the raffinate phase or an aqueous solution of hydroxylamine sulfate + sulfuric acid and an organic solution of caprolactam in the extract phase. The organic solution of caprolactam is transported to the caprolactam device for treatment, and the aqueous sulfuric acid solution or the aqueous solution of hydroxylamine sulfate + sulfuric acid enters step S2. Caprolactam sulfate is an ester compound, which contains the structural part of caprolactam and a sulfate group. The sulfate group has a high reactivity. Under hydrolysis conditions, water molecules react with the sulfate group to undergo hydrolysis, break the ester bond, and generate caprolactam and an aqueous sulfuric acid solution. In one embodiment, it is preferably resolved with an aqueous solution of hydroxylamine sulfate. Sulfuric acid makes the extraction process of caprolactam extremely difficult due to its strong polarity. The presence of hydroxylamine sulfate can disrupt the binding force between caprolactam and sulfuric acid through salting-out effect, making caprolactam easier to be extracted, shortening the extraction time, improving production efficiency, and increasing the yield of caprolactam. Moreover, hydroxylamine sulfate is the target product prepared in the present invention and will not introduce new impurities. Further, the mass ratio of the aqueous solution of hydroxylamine sulfate to caprolactam sulfate is 1 - 10, preferably 2 - 6, and the mass percentage content of hydroxylamine sulfate in the aqueous solution of hydroxylamine sulfate is greater than 0 and less than or equal to 35%.

[0027] The extractant is preferably benzene. After extraction, a mixed solution of benzene and caprolactam enters the caprolactam device to recover caprolactam products. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the aqueous solution of caprolactam sulfate. This step can be realized by using three liquid-liquid extraction towers, namely a sulfur extraction tower, a caprolactam extraction tower, and a residual extraction tower. Each extraction tower includes a tower top, an extraction section, and a tower bottom from top to bottom in sequence; both the tower top and the tower bottom are provided with feed inlets and discharge outlets. The sulfur extraction tower is used to extract caprolactam from the aqueous sulfuric acid solution containing caprolactam, and the solvent is benzene. Please refer to Figure 2, a benzene-caprolactam solution (a mixed solution of benzene and caprolactam) is formed at the top of the sulfur extraction column, and an aqueous sulfuric acid solution is at the bottom. The aqueous sulfuric acid solution is used for the ketoxime hydrolysis reaction in step S2. The benzene in the benzene-caprolactam solution at the top of the sulfur extraction column is recovered and recycled. The benzene-caprolactam solution at the top of the sulfur extraction column can be sent to the hexane extraction column of the existing caprolactam plant for treatment. Specifically, the aqueous caprolactam sulfate solution enters the extraction section of the sulfur extraction column from the top feed port of the sulfur extraction column, and the extraction agent benzene enters the extraction section of the sulfur extraction column from the bottom feed port of the sulfur extraction column. After extraction and separation, the extracted phase benzene-caprolactam solution coming out from the top discharge port of the sulfur extraction column enters the extraction section of the hexane extraction column from the bottom feed port of the hexane extraction column. At the same time, the existing crude caprolactam oil generated by ammonia neutralization enters the extraction section of the hexane extraction column from the top feed port of the hexane extraction column for primary extraction of the crude caprolactam oil. The total flow rate of benzene used in the sulfur extraction column and the hexane extraction column is the same as the benzene consumption of the original hexane extraction column. The benzene-caprolactam solution overflowing from the top discharge port of the hexane extraction column goes to the benzene-caprolactam pump tank for refining in the subsequent processes of the existing caprolactam plant. After treatment in the subsequent processes, benzene is recovered and supplied for recycling in the sulfur extraction column and the hexane extraction column. The hexane extraction residue at the bottom of the hexane extraction column contains a relatively high amount of caprolactam and needs further extraction to reduce caprolactam loss. The hexane extraction residue coming out from the bottom discharge port of the hexane extraction column is sent to the top feed port of the residue extraction column to the extraction section of the residue extraction column, and fresh benzene from the caprolactam plant is used for extraction from the bottom feed port to the extraction section of the residue extraction column. The benzene-caprolactam solution overflowing from the top discharge port of the residue extraction column contains a relatively low amount of caprolactam and is then returned to the bottom feed port of the hexane extraction column to the extraction section of the hexane extraction column to be used for extraction of the crude caprolactam oil together with the benzene-caprolactam solution coming out from the top discharge port of the sulfur extraction column. The extraction residue coming out from the bottom discharge port of the residue extraction column is sent to the subsequent processes of the existing caprolactam plant for treatment.

[0028] If caprolactam is not separated in advance, the caprolactam sulfuric acid solution reacts with the ketoxime hydrolysis reaction simultaneously. Since caprolactam will also undergo a hydrolysis side reaction to form 6-aminocaproic acid under the ketoxime hydrolysis reaction conditions, not only is caprolactam wasted, but also the hydrolysis product affects the product quality of caprolactam and hydroxylamine sulfate. Therefore, in step S1 of the present invention, caprolactam can be extracted and separated in advance at a relatively low temperature of 40 - 50 °C, thereby avoiding the hydrolysis side reaction of caprolactam at high temperature, and thus improving the yield and product quality of caprolactam.

[0029] S2: In the sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution obtained in step S1, add ketoxime. The ketoxime reacts with the sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution to undergo a hydrolysis reaction to generate an aqueous solution of hydroxylamine sulfate and a ketone. The reaction temperature is 70 - 90°C, the absolute pressure is 20 - 40 kPa, and the hydrolysis reaction time is 0.5 - 3.5 h. The generated ketone is separated by a separator and sent to the ketoxime preparation device for recycling. The ketone, ammonia, and hydrogen peroxide can produce ketoxime under the action of a titanium-silicon catalyst at a certain temperature. The added ketoxime is a low-carbon ketoxime, preferably butanone oxime or cyclohexanone oxime. In one embodiment, the added ketoxime is butanone oxime, and butanone is generated after the hydrolysis reaction. The butanone is sent to the butanone oxime device to produce butanone oxime, and the butanone oxime is recycled back to step S2 to react with the sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1 - 1.3. In a specific embodiment, the feed mass percentage composition is 17.37% butanone oxime, 64.5% water, 9.53% sulfuric acid, and 8.62% hydroxylamine sulfate, corresponding to a molar ratio of butanone oxime to sulfuric acid of 1.05. In another embodiment, the added ketoxime is cyclohexanone oxime, and the generated ketone after the hydrolysis reaction is cyclohexanone. The cyclohexanone is sent to the ammoximation unit of the caprolactam device to produce cyclohexanone oxime, which is used as a raw material for producing caprolactam or recycled back to step S2.

[0030] In this step, the hydrolysis reaction of ketoxime with the sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution can be carried out in a reactive distillation column. The reactive distillation column includes a top, a column body, a bottom, a reflux system, a vacuum system, a temperature control system, multiple feed inlets and multiple discharge outlets at the top and bottom. The multiple feed inlets of the reactive distillation column are respectively connected to the bottom discharge outlet of the sulfur extraction column and the discharge outlet of the ketoxime device. The sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution coming out of the bottom discharge outlet of the sulfur extraction column and the ketoxime coming out of the discharge outlet of the ketoxime device enter the reaction zone of the column body from the feed inlets of the reactive distillation column to carry out the hydrolysis reaction. The reaction temperature inside the column body is controlled at 70 - 90°C through the temperature control system, the absolute pressure inside the column body is controlled at 20 kPa - 40 kPa through the vacuum system, and the reflux ratio at the top of the column is controlled at 0.2 - 4 through the reflux system. After the hydrolysis reaction for 0.5 h - 3.5 h, an aqueous solution of hydroxylamine sulfate and a ketone are generated. The ketone exits from the top discharge outlet of the reactive distillation column and enters the reflux drum. After condensation and separation in the reflux drum, water flows back into the reactive distillation column, and the ketone is discharged and enters the ketoxime device. The aqueous solution of hydroxylamine sulfate exits from the bottom discharge outlet of the reactive distillation column and enters the stripping column to strip and separate a small amount of unreacted ketoxime.

[0031] In this step, the hydrolysis reaction temperature is 70 - 90°C, which is much lower than the reaction temperature of 98 - 120°C in the prior art. This greatly reduces the corrosiveness of the sulfuric acid solution caused by the increase in temperature and reduces the requirements for the equipment material. Thus, the production cost is reduced.

[0032] S3: Stripping the hydroxylamine sulfate aqueous solution obtained in step S2 to separate out a small amount of unreacted ketoxime. The unreacted ketoxime is recycled to step S2 to participate in the hydrolysis reaction. The hydroxylamine sulfate aqueous solution is obtained as the product hydroxylamine sulfate after concentration crystallization, centrifugal filtration, and drying dehydration. Specifically, crystallization can be carried out through a crystallizer, centrifugal separation is carried out through a centrifuge after crystallization, and dehydration and drying are carried out through a dryer after centrifugal separation.

[0033] S4: Part of the hydroxylamine sulfate residue after centrifugal filtration is sent to step S1 for the hydrolysis of caprolactam sulfate. Preferably, 30 - 90% by mass of the hydroxylamine sulfate residue after centrifugal filtration is returned to step S1 for the analysis of caprolactam sulfate, and the remaining hydroxylamine sulfate residue is transported to the oximation reactor to carry out an oximation reaction with ketone for recovery. Please refer to Figure 3 , 10 - 70% by mass of the hydroxylamine sulfate residue after centrifugal filtration in step S3 is subjected to an oximation reaction with ketone in the oximation reactor to generate ketoxime and an aqueous ammonium sulfate solution. The reaction temperature is 40 - 70°C, the pressure is atmospheric pressure, a small amount of ammonia water is added to increase the oximation conversion rate, and after adjusting the reaction pH value to 3 - 6, it enters the separator for separation. The reaction mixture overflows from the top of the oximation reactor into the separator, and in the separator, the reaction mixture naturally settles and layers. The upper oil phase ketoxime is sent to the ketoxime preparation device for purification treatment, and the lower aqueous phase is an ammonium sulfate aqueous solution containing impurities and with hydroxylamine sulfate removed, which is sent to the ammonium sulfate unit of the caprolactam device for treatment. The molar ratio of ketone to hydroxylamine sulfate is 1 - 1.2, and the mass ratio of the oil phase ketoxime to the aqueous phase ammonium sulfate solution is 0.5 - 2.5.

[0034] Caprolactam sulfate contains a small amount of organic and inorganic impurities. Among them, the organic impurities can be removed during the benzene extraction of caprolactam in step S1 and enter the caprolactam device; the inorganic impurities are water-soluble and accumulate with the hydroxylamine sulfate mother liquor circulation. After accumulating to a certain concentration, they will affect the quality of the hydroxylamine sulfate product, and the impurities need to be removed. The hydroxylamine sulfate residue with accumulated impurities (the mass percentage concentration of the hydroxylamine sulfate residue at 30°C is 39%) is mostly recycled back to step S1 in step S4 to dilute caprolactam sulfate, and another branch is sent to the oximation reactor for impurity treatment. Example 1

[0035] S1: At a temperature of 40 °C and atmospheric pressure, 100 g of caprolactam sulfate is resolved with 100 g of an aqueous hydroxylamine sulfate solution with a mass percentage content of 15% to obtain an aqueous caprolactam sulfate solution; after extracting and separating caprolactam from the aqueous caprolactam sulfate solution with 800 g of benzene, a raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution and an extract phase of caprolactam organic solution are obtained. The caprolactam organic solution is transported to a caprolactam device for treatment to obtain 48.5 g of caprolactam. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the aqueous caprolactam sulfate solution. The raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution enters step S2.

[0036] S2: 87 g of butanone oxime is added to the raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution. Butanone oxime undergoes a hydrolysis reaction with the hydroxylamine sulfate + sulfuric acid aqueous solution to generate an aqueous hydroxylamine sulfate solution and a ketone. The reaction temperature is 70 °C and the pressure is 20 kPa; the generated butanone is separated by a separator and sent to a butanone oxime preparation device; and then recycled back to step S2 to undergo a hydrolysis reaction with the hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1.

[0037] S3: The aqueous hydroxylamine sulfate solution obtained in step S2 is stripped to separate 9 g of unreacted ketone oxime and sent to step S2 to participate in the hydrolysis reaction. The aqueous hydroxylamine sulfate solution is concentrated, crystallized, centrifugally filtered, and dried and dehydrated to obtain 73.5 g of the product hydroxylamine sulfate.

[0038] S4: 80% of the hydroxylamine sulfate residue after centrifugal filtration in step S3 reacts with a ketone in an oximation reactor to generate butanone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 40 °C and the pressure is atmospheric pressure. A small amount of ammonia water is added to adjust the reaction pH value to 3 and then it enters a separator for separation. The reaction mixture overflows from the top and enters the separator. In the separator, the reaction mixture naturally settles and layers. The upper oil phase of butanone oxime is sent to a butanone oxime preparation device for purification treatment, and the lower aqueous phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, and is sent to the ammonium sulfate unit of the caprolactam device for treatment. The molar ratio of the ketone to hydroxylamine sulfate is 1, and the mass ratio of the oil phase to the aqueous phase is 0.5.

[0039] For the caprolactam yield and hydroxylamine sulfate yield of this example, see Table 1.

[0040] Table 1

[0041] Example 2

[0042] S1: At a temperature of 45°C and atmospheric pressure, 100 g of caprolactam sulfate is resolved with 500 g of aqueous solution to obtain an aqueous caprolactam sulfate solution; after extracting and separating caprolactam from the aqueous caprolactam sulfate solution with 3600 g of benzene, a raffinate aqueous sulfuric acid solution and an extract organic caprolactam solution are obtained. The organic caprolactam solution is transported to the caprolactam unit for treatment to obtain 47.8 g of caprolactam. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the aqueous caprolactam sulfate solution. The raffinate aqueous sulfuric acid solution enters step S2.

[0043] S2: 104.4 g of butanone oxime is added to the raffinate aqueous sulfuric acid solution. Butanone oxime reacts with the aqueous sulfuric acid solution to generate an aqueous hydroxylamine sulfate solution and ketone. The reaction temperature is 80°C and the pressure is 35 kPa; the generated butanone is separated by a separator and sent to the butanone oxime preparation unit; and then recycled back to step S2 to react with the aqueous sulfuric acid solution to prepare hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1.2.

[0044] S3: The aqueous hydroxylamine sulfate solution obtained in step S2 is stripped to separate 17.4 g of unreacted ketone oxime and sent to step S2 to participate in the hydrolysis reaction. The aqueous hydroxylamine sulfate solution is concentrated, crystallized, centrifugally filtered, and dried and dehydrated to obtain 76.3 g of the product hydroxylamine sulfate.

[0045] S4: 85% of the hydroxylamine sulfate residue after centrifugal filtration in step S3 reacts with ketone in an oximation reactor to generate ketone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 55°C and the pressure is atmospheric pressure. A small amount of ammonia water is added to adjust the reaction pH value to 5 and then it enters a separator for separation. The reaction mixture overflows from the top into the separator, and in the separator, the reaction mixture naturally settles and layers. The upper oil phase of ketone oxime is sent to the ketone oxime preparation unit for purification treatment, and the lower aqueous phase is an aqueous ammonium sulfate solution containing impurities and with hydroxylamine sulfate removed, which is sent to the ammonium sulfate unit of the caprolactam unit for treatment. The molar ratio of ketone to hydroxylamine sulfate is 1.1, and the mass ratio of the oil phase to the aqueous phase is 1.5.

[0046] For the caprolactam yield and hydroxylamine sulfate yield of this example, see Table 2.

[0047] Table 2

[0048] Example 3

[0049] S1: At a temperature of 50 °C and atmospheric pressure, 100 grams of caprolactam sulfate is resolved with 1000 grams of an aqueous hydroxylamine sulfate solution with a mass percentage content of 35% to obtain an aqueous caprolactam sulfate solution; after extracting and separating caprolactam from the aqueous caprolactam sulfate solution with 5000 grams of benzene, a raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution and an extraction phase of caprolactam organic solution are obtained. The caprolactam organic solution is transported to the caprolactam plant for treatment, and 48.7 grams of caprolactam is obtained. The separated benzene is refined and recycled to step S1 as an extraction agent to extract caprolactam from the aqueous caprolactam sulfate solution. The raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution enters step S2.

[0050] S2: 113.1 grams of cyclohexanone oxime is added to the raffinate phase of hydroxylamine sulfate + sulfuric acid aqueous solution. Butanone oxime and the hydroxylamine sulfate + sulfuric acid aqueous solution undergo a hydrolysis reaction to generate an aqueous hydroxylamine sulfate solution and butanone. The reaction temperature is 90 °C and the pressure is 50 kPa; the generated butanone is separated by a separator and sent to the butanone oxime preparation plant; and then recycled to step S2 to react with the hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1.3.

[0051] S3: After the aqueous hydroxylamine sulfate solution obtained in step S2 is stripped, 34 grams of unreacted ketoxime is separated and sent to step S2 to participate in the hydrolysis reaction. The aqueous hydroxylamine sulfate solution is concentrated, crystallized, centrifugally filtered, and dried and dehydrated to obtain 79 grams of the product hydroxylamine sulfate.

[0052] S4: 90% of the hydroxylamine sulfate residue after centrifugal filtration in step S3 reacts with a ketone in an oximation reactor to generate ketoxime and an aqueous ammonium sulfate solution. The reaction temperature is 70 °C and the pressure is atmospheric pressure. After adding a small amount of ammonia water to adjust the reaction pH value to 6, it enters a separator for separation. The reaction mixture overflows from the top into the separator, and in the separator, the reaction mixture naturally settles and layers. The upper oil phase of ketoxime is sent to the ketoxime preparation plant for purification treatment, and the lower water phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, and is sent to the ammonium sulfate unit of the caprolactam plant for treatment. The molar ratio of the ketone to hydroxylamine sulfate is 1.2, and the mass ratio of the oil phase to the water phase is 2.5.

[0053] For the caprolactam yield and hydroxylamine sulfate yield of this example, see Table 3.

[0054] Table 3

[0055]

[0056] In summary, the preparation method of hydroxylamine sulfate provided in this embodiment uses ketoxime and caprolactam sulfate as raw materials. First, caprolactam sulfate is resolved with water or an aqueous solution of hydroxylamine sulfate to obtain an aqueous solution of caprolactam sulfate, and then caprolactam and the sulfuric acid aqueous solution are separated by extraction. Caprolactam can be separated at a relatively low temperature first, thereby avoiding the hydrolysis side reaction of caprolactam at high temperature and improving the yield and quality of caprolactam. The reaction of ketoxime with the sulfuric acid aqueous solution to prepare hydroxylamine sulfate does not require the additional addition of sulfuric acid, and at the same time, the separated ketone is recycled. The production of caprolactam and the production of hydroxylamine sulfate are combined to reduce the by-product of ammonium sulfate. At the same time, caprolactam and hydroxylamine sulfate are produced, and a resource recycling comprehensive utilization industrial chain of caprolactam-ketoxime-coproduced hydroxylamine sulfate is established to improve the comprehensive competitiveness of caprolactam products. At the same time, by separating caprolactam first and recycling ketoxime, the sulfuric acid aqueous solution can fully react, improving the yield of hydroxylamine sulfate and reducing the production cost. In addition, in the preparation of ketoxime, a high conversion rate is not required during the conversion from ketone to oxime, and the unreacted ketone can be recycled back to the oximation reactor to carry out the oximation reaction with the residual liquid of hydroxylamine sulfate.

[0057] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the claims.

Claims

1. A method for preparing hydroxylamine sulfate, characterized in that: The steps include: S1: decomposing caprolactam sulfate with water or hydroxylamine sulfate aqueous solution to obtain caprolactam sulfuric acid aqueous solution; extracting and separating caprolactam from the caprolactam sulfuric acid aqueous solution with an extractant to obtain a raffinate phase of sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution and an extract phase of caprolactam organic solution, the caprolactam organic solution is transported to a caprolactam device for treatment, and the sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution enters step S2; S2: adding ketoxime to the aqueous sulfuric acid solution or the hydroxylamine sulfate + sulfuric acid solution obtained in step S1, and hydrolyzing the ketoxime with the aqueous sulfuric acid solution or the hydroxylamine sulfate + sulfuric acid solution to generate an aqueous hydroxylamine sulfate solution and ketones, and the generated ketones are separated by a separator and sent to a ketoxime preparation device for recycling; S3: stripping the hydroxylamine sulfate aqueous solution obtained in step S2 to separate a small amount of unreacted ketoxime, which is recycled to step S2 to participate in the hydrolysis reaction; the hydroxylamine sulfate aqueous solution is concentrated, crystallized, centrifugally filtered, and dried to obtain the product hydroxylamine sulfate; S4: returning part of the hydroxylamine sulfate residue after centrifugal filtration in step S3 to step S1 for the analysis of caprolactam sulfate, and subjecting the remaining hydroxylamine sulfate residue to oximation reaction with ketone.

2. The preparation method according to claim 1, characterized in that: In step S1, the extractant is benzene, and after extraction, a mixed solution of benzene and caprolactam is formed and enters the caprolactam device to recover the caprolactam product. The separated benzene is refined and then circulated into step S1 as an extractant to extract caprolactam from the caprolactam sulfuric acid aqueous solution.

3. The preparation method according to claim 1, characterized in that: In step S1, the hydrolysis conditions of caprolactam sulfate are: temperature of 40-50° C. and pressure of normal pressure; the mass ratio of hydroxylamine sulfate aqueous solution to caprolactam sulfate is 1-10, and the mass percentage content of hydroxylamine sulfate in the hydroxylamine sulfate aqueous solution is greater than 0 and less than or equal to 35%.

4. The preparation method according to claim 1, characterized in that: The ketone oxime added in step S2 is butanone oxime, and the ketone generated after the hydrolysis reaction is butanone. The butanone is sent to a butanone oxime device to produce butanone oxime, and the butanone oxime is recycled and sent back to step S2 to undergo a hydrolysis reaction with a sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate.

5. The preparation method according to claim 4, characterized in that: In the step S2, in the hydrolysis reaction of butanone oxime and sulfuric acid, the temperature is 70-90° C., the pressure is 20-40 kPa absolute pressure, the hydrolysis reaction time is 0.5-3.5 h; and the molar ratio of butanone oxime to sulfuric acid is 1-1.

3.

6. The preparation method according to claim 1, characterized in that: The ketone oxime added in step S2 is cyclohexanone oxime, and the ketone generated after the hydrolysis reaction is cyclohexanone. The cyclohexanone is sent to the ammoximation unit of the caprolactam device to produce cyclohexanone oxime as a raw material for producing caprolactam or recycled to step S2.

7. The preparation method according to claim 1, characterized in that: In step S4, 30-90% by mass of the residual hydroxylamine sulfate after centrifugal filtration is returned to step S1 for the resolution of caprolactam sulfate, and the remaining residual hydroxylamine sulfate is transported to the oximation reactor for oximation reaction with ketone.

8. The preparation method according to claim 7, characterized in that: In the oximation reactor, hydroxylamine sulfate and ketone undergo oximation reaction to generate ketone oxime and ammonium sulfate, which are then separated by a separator.

9. The preparation method according to claim 8, characterized in that: A small amount of ammonia water is added to the oximation reactor to adjust the pH value of the reaction mixture to 3-6, and the reaction mixture overflows from the top of the oximation reactor into a separator, where the reaction mixture naturally settles and layers, and the oil phase ketoxime is sent to a ketoxime preparation device for purification, and the water phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, and is sent to the ammonium sulfate unit of a caprolactam device for treatment.

10. The preparation method according to claim 9, characterized in that: In step S4, the oximation reaction temperature of the hydroxylamine sulfate residue and ketone is 40-70° C. and the pressure is normal pressure; the molar ratio of ketone to hydroxylamine sulfate is 1-1.2, and the mass ratio of the oil phase ketoxime to the aqueous phase ammonium sulfate solution is 0.5-2.5.

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