A preparation method of hydroxylamine sulfate

Abstract

The invention discloses a method for preparing hydroxylamine sulfate, which comprises the following steps: S1: decomposing 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 with an extractant, conveying the caprolactam organic solution as the extraction phase to a caprolactam device for treatment, and conveying the raffinate phase, a sulfuric acid aqueous solution or a hydroxylamine sulfate + sulfuric acid aqueous solution, to step S2; S2: adding ketoxime and the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution to undergo a hydrolysis reaction to generate a hydroxylamine sulfate aqueous solution and a ketone, and conveying the ketone to a ketoxime preparation device after separation; S3: stripping and separating the hydroxylamine sulfate aqueous solution, conveying unreacted ketoxime to step S2 to participate in the hydrolysis reaction, and subjecting the hydroxylamine sulfate aqueous solution to concentration, crystallization, centrifugal filtration, and drying and dehydration to obtain hydroxylamine sulfate; and S4: returning part of the hydroxylamine sulfate residual liquid after centrifugal filtration to step S1 for decomposing caprolactam sulfate, and subjecting the remaining hydroxylamine sulfate residual liquid to an oximation reaction with the ketone.

Description

Technical Field

[0001] The invention relates to the technical field of hydroxylamine sulfate, and in particular to a method for preparing hydroxylamine sulfate by hydrolyzing a translocated ester. Background Art

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

[0003] The primary caprolactam production process is the hydroxylamine-cyclohexanone process. Benzene is prepared through cyclohexanone, followed by oximation of cyclohexanone. Cyclohexanone oxime is then rearranged under the catalysis of fuming sulfuric acid to produce caprolactam. The rearrangement product, also known as a transposition ester, is caprolactam sulfate. Due to the chemical bond between caprolactam and sulfuric acid, separation is difficult. Industrially, caprolactam sulfate is almost always neutralized with ammonia to produce caprolactam and ammonium sulfate, which are then separated. This process has been widely used in caprolactam production, but its drawbacks include the high consumption of highly economically valuable ammonia and fuming sulfuric acid and the production of less economically valuable ammonium sulfate. For every ton of caprolactam produced, 1.6 to 1.8 tons of ammonium sulfate are produced, resulting in a net loss of 200 to 600 yuan per ton. This high level of ammonium sulfate byproduct increases caprolactam production costs. Improving the production process and reducing ammonium sulfate production have become key challenges in caprolactam production.

[0004] In order to reduce the by-production of ammonium sulfate in the caprolactam production process, Japan's Sumitomo Corporation has developed a caprolactam production technology without the by-product of ammonium sulfate, namely, gas-phase rearrangement. Cyclohexanone oxime undergoes a rearrangement reaction at high temperature under the action of a molecular sieve catalyst and a solvent, converting cyclohexanone oxime into caprolactam. This process does not produce ammonium sulfate as a by-product, but the reaction conditions are harsh and the caprolactam selectivity is significantly lower than that of fuming sulfuric acid rearrangement. Although this process does not produce ammonium sulfate as a by-product, it also has no cost advantage.

[0005] Hydroxylamine sulfate, also known as hydroxylamine sulfate or hydroxylamine sulfate, is an important intermediate used in pesticide and pharmaceutical intermediates, as well as as a mineral processing agent. It also has extensive applications in the oil and fat, industrial corrosion protection, photography, dyes, and rubber industries. Global hydroxylamine production capacity (including hydroxylamine sulfate and hydroxylamine hydrochloride) is approximately 88 kt / a. Major manufacturers include Jinhua, Aqua, BASF, Ube Japan, and Zhejiang Sheng'an. Hydroxylamine sulfate is used in a variety of applications, such as pharmaceuticals, agrochemicals, and photography. Due to increasing demand from these industries, the global market for hydroxylamine sulfate is expected to grow significantly over the forecast period. China is one of the largest consumers of hydroxylamine sulfate, holding a significant share of the global market. The Chinese market has been growing rapidly due to increasing demand from the pharmaceutical and agrochemical industries.

[0006] Prior art disclosed solid hydroxylamine sulfate synthesis routes and processes, both domestically and internationally, primarily include the nitromethane route, natural gas (methane) nitration route, acetone oxime route, disulfonate ammonium salt hydrolysis method, nitric oxide reduction method, and the production of hydroxylamine sulfate using trimethoprim wastewater. However, the nitromethane route has a low product yield, produces a wide variety of byproducts, and requires significant investment in separation equipment; the acetone oxime route has a complex process, requires a wide variety of raw materials, consumes a large amount of raw materials, and is costly; the disulfonate hydrolysis method, while mature, is only suitable for large-scale production in large factories and requires significant investment. The yields of the other process routes are relatively low. In summary, the high investment, wide variety of raw materials, high costs, low yield, and low product purity hinder the competitiveness of high-purity solid hydroxylamine sulfate.

[0007] Patent CN202310237385 proposes a method for the co-production of caprolactam and hydroxylamine sulfate. The method comprises the following steps: (1) ammonia oximation reaction: ketone is reacted with ammonia and hydrogen peroxide at a certain temperature under the action of a titanium silicon catalyst to produce an oxime solution; (2) a hydrolysis reaction: caprolactam sulfate is added with an appropriate amount of desalted water, stirred, and the hydrolysis temperature is controlled to carry out a hydrolysis reaction to obtain a hydrolysis reactant caprolactam sulfuric acid solution; (3) a co-production reaction of caprolactam and hydroxylamine sulfate: oxime solution is added to the caprolactam sulfuric acid solution, and the reaction is carried out at a certain temperature and pressure to obtain caprolactam and hydroxylamine sulfate solution; (4) physical separation: the reactants in step (3) are layered, the upper layer is a light phase, which is an organic solvent containing ketone, and the lower layer is a heavy phase, which is an aqueous phase containing hydroxylamine sulfate and caprolactam; (5) the organic solvent containing ketone is returned to step (1) for ammonia oximation reaction, or after the solvent is removed, it is returned to step (1) for ammonia oximation 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, with the highest in the examples being only 61%. Furthermore, the reaction temperature for the co-production of caprolactam and hydroxylamine sulfate is between 98 and 120°C, and the reaction time is 4-6 hours. Because the corrosiveness of the caprolactam-sulfuric acid solution increases sharply with increasing temperature, the equipment material requirements are extremely high, resulting in high equipment investment. The low single-pass yield of hydroxylamine sulfate also leads to high material and energy consumption. The high reaction temperature for the co-production of caprolactam-sulfuric acid solution also causes hydrolysis of the caprolactam, resulting in a decrease in the caprolactam yield. The added organic solvent needs to be recovered, which also increases the energy consumption of the equipment.

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

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

[0011] To achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing hydroxylamine sulfate, comprising the following steps: S1: decomposing caprolactam sulfate with water or an aqueous solution of hydroxylamine sulfate to obtain an aqueous solution of caprolactam sulfuric acid; extracting and separating caprolactam from the aqueous solution of caprolactam sulfuric acid with an extractant to obtain an aqueous solution of sulfuric acid or hydroxylamine sulfate + aqueous solution of sulfuric acid and an organic solution of caprolactam in an extract phase, the organic solution of caprolactam being transported to a caprolactam device for treatment, and the aqueous solution of sulfuric acid or hydroxylamine sulfate + aqueous solution of sulfuric acid entering step S2; S2: the aqueous solution of sulfuric acid or hydroxylamine sulfate + aqueous solution of sulfuric acid obtained in step S1 is separated into a mixture of the aqueous solution of sulfuric acid or hydroxylamine sulfate + aqueous solution of sulfuric acid. Ketoxime is added to the acid aqueous solution, and the ketoxime undergoes a hydrolysis reaction with the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution to generate a hydroxylamine sulfate aqueous solution and a ketone. The generated ketone is separated in a separator and sent to a ketoxime preparation device for recycling. S3: The hydroxylamine sulfate aqueous solution obtained in step S2 is stripped to separate a small amount of unreacted ketoxime, which is sent to step S2 to participate in the hydrolysis reaction. The hydroxylamine sulfate aqueous solution is concentrated, crystallized, centrifuged, filtered, and dried and dehydrated to obtain the product hydroxylamine sulfate. S4: Part of the hydroxylamine sulfate residue after centrifugation in step S3 is returned to step S1 for the resolution of caprolactam sulfate, and the remaining hydroxylamine sulfate residue is subjected to an oximation reaction with the ketone.

[0012] Furthermore, 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 recycled into step S1 as an extractant to extract caprolactam from the caprolactam sulfuric acid aqueous solution.

[0013] Furthermore, in step S1, the hydrolysis conditions of caprolactam sulfate are: temperature of 40-50° C., 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%.

[0014] Furthermore, the ketone oxime added in step S2 is butanone oxime, 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 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.

[0015] Furthermore, in step S2, the hydrolysis reaction of butanone oxime and sulfuric acid is carried out at a temperature of 70-90° C. and an absolute pressure of 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] Furthermore, the ketoxime 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, which is used as a raw material for producing caprolactam or recycled to step S2.

[0017] Furthermore, in step S4, 30-90% by mass of the hydroxylamine sulfate residue after centrifugation is returned to step S1 for resolution of caprolactam sulfate, and the remaining hydroxylamine sulfate residue is transported to an oximation reactor for oximation reaction with ketone.

[0018] Furthermore, in the oximation reactor, hydroxylamine sulfate and ketone undergo oximation reaction to generate ketoxime and ammonium sulfate, which are then separated by a separator.

[0019] Furthermore, a small amount of aqueous ammonia 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 separates into layers. The oily ketoxime is sent to a ketoxime preparation device for purification, and the aqueous phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, which is sent to the ammonium sulfate unit of a caprolactam device for treatment.

[0020] Furthermore, 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.

[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, using ketoxime and caprolactam sulfate as raw materials, and obtaining caprolactam sulfuric acid aqueous solution after caprolactam sulfate is first parsed with water or an aqueous solution of hydroxylamine sulfate, and then extracting and separating caprolactam and sulfuric acid aqueous solution, caprolactam can be separated out in advance at a lower temperature, thereby avoiding the hydrolysis side reaction of caprolactam at high temperature, thereby improving the caprolactam yield. Ketoxime reacts with sulfuric acid aqueous solution to prepare hydroxylamine sulfate, without the need for additional sulfuric acid, and the separated ketone is sent to the ketoxime preparation device for recycling application, combining caprolactam production with hydroxylamine sulfate production, reducing ammonium sulfate by-product, and simultaneously producing caprolactam and hydroxylamine sulfate, establishing a resource recycling and comprehensive utilization industry chain of caprolactam-ketoxime-co-production of hydroxylamine sulfate, improving the comprehensive competitiveness of caprolactam products, and at the same time, by first separating caprolactam and recycling ketoxime, the sulfuric acid aqueous solution can fully react, improving the yield of hydroxylamine sulfate, and reducing production costs. In addition, the preparation of ketoxime does not require a high conversion rate in the conversion process of ketone to oxime, and the unconverted ketone can be recycled back to the oximation reactor for oximation reaction with the residual hydroxylamine sulfate. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0024] Figure 3 Schematic diagram of a device for treating hydroxylamine sulfate residual liquid in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and examples.

[0026] See Figure 1 This embodiment provides a method for preparing hydroxylamine sulfate, comprising the following steps:

[0027] S1: At a temperature of 40-50°C and atmospheric pressure, caprolactam sulfate is subjected to hydrolysis with water or aqueous hydroxylamine sulfate to obtain aqueous caprolactam sulfate. Caprolactam is then extracted and separated from the aqueous caprolactam sulfate using an extractant, yielding a raffinate aqueous sulfuric acid phase or a hydroxylamine sulfate + aqueous sulfuric acid phase and an organic caprolactam solution phase. The organic caprolactam solution is then transported to a caprolactam unit for processing, and the aqueous sulfuric acid phase or the hydroxylamine sulfate + aqueous sulfuric acid phase proceeds to step S2. Caprolactam sulfate is an ester compound containing the structural portion of caprolactam and sulfate groups. Sulfate groups are highly reactive. Under hydrolysis conditions, water molecules react with the sulfate groups to hydrolyze, breaking the ester bond and producing caprolactam and aqueous sulfuric acid. In one embodiment, aqueous hydroxylamine sulfate is preferably used for hydrolysis. Sulfuric acid, due to its strong polarity, makes the extraction process of caprolactam extremely difficult. The presence of hydroxylamine sulfate can break the binding force between caprolactam and sulfuric acid through a salting-out effect, making the caprolactam easier to extract, shortening the extraction time, improving production efficiency, and increasing the yield of caprolactam. Furthermore, hydroxylamine sulfate is the target product prepared by the present invention and does not introduce new impurities. Furthermore, the mass ratio of the hydroxylamine sulfate aqueous solution to the caprolactam sulfate is 1-10, preferably 2-6, 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%.

[0028] The extractant is preferably benzene. After extraction, a mixed solution of benzene and caprolactam is formed and enters the caprolactam unit to recover the caprolactam product. The separated benzene is refined and then recycled into step S1 as an extractant to extract caprolactam from the caprolactam sulfuric acid aqueous solution. This step can be achieved using three liquid-liquid extraction towers, namely a sulfur extraction tower, a hexane extraction tower, and a residual extraction tower. Each extraction tower includes a top, an extraction section, and a bottom from top to bottom. Both the top and bottom of the tower are provided with a feed port and a discharge port. The sulfur extraction tower is used to extract caprolactam from the sulfuric acid aqueous solution containing caprolactam. The solvent is benzene. Please refer to Figure 2Benzene-hexyl liquor (a mixed solution of benzene and caprolactam) forms at the top of the sulfur extraction tower, while aqueous sulfuric acid forms at the bottom. This aqueous sulfuric acid solution is used for the ketoxime hydrolysis reaction in step S2. The benzene solvent in the benzene-hexyl liquor at the top of the sulfur extraction tower is recovered and recycled. The benzene-hexyl liquor at the top of the sulfur extraction tower can be sent to the hexyl extraction tower of an existing caprolactam plant for treatment. Specifically, the aqueous sulfuric acid solution of caprolactam enters the extraction section of the sulfur extraction tower through the top feed port of the sulfur extraction tower, and the extractant benzene enters the extraction section of the sulfur extraction tower through the bottom feed port of the sulfur extraction tower. After extraction and separation, the extract phase, benzene-hexyl liquor, exiting the top discharge port of the sulfur extraction tower, enters the extraction section of the hexyl extraction tower through the bottom feed port of the hexyl extraction tower. Simultaneously, the crude caprolactam oil generated by neutralization with ammonia enters the extraction section of the hexyl extraction tower through the top feed port of the hexyl extraction tower, performing the primary extraction of the crude caprolactam oil. The total benzene flow rate used in the sulfur extraction tower and the hexyl extraction tower is the same as the benzene usage of the existing hexyl extraction tower. The benzene-hexyl liquid overflowing from the top discharge port of the hexyl extraction tower is sent to the benzene-hexyl pump tank for refining in the existing caprolactam post-process. Benzene is recovered through post-process treatment and recycled for the sulfur extraction tower and the hexyl extraction tower. The hexyl extraction residue at the bottom of the hexyl extraction tower contains a higher amount of caprolactam and needs further extraction to reduce the loss of caprolactam. The hexyl extraction residue coming out of the bottom discharge port of the hexyl extraction tower is sent to the top feed port of the residual extraction tower to the extraction section of the residual extraction tower. Fresh benzene from the caprolactam device is used to extract the extraction section of the residual extraction tower from the bottom feed port of the residual extraction tower. The benzene-hexyl liquid overflowing from the top discharge port of the residual extraction tower has a lower caprolactam content and is returned to the bottom feed port of the hexyl extraction tower to the extraction section of the hexyl extraction tower. It is used together with the benzene-hexyl liquid coming out of the top discharge port of the sulfur extraction tower for the extraction of caprolactam crude oil. The extraction residue coming out of the bottom discharge port of the residual extraction tower is sent to the existing caprolactam post-process for treatment.

[0029] If caprolactam is not separated in advance, the caprolactam sulfuric acid solution will react with the ketoxime hydrolysis reaction simultaneously. Since caprolactam will also undergo a hydrolysis side reaction to produce aminocaproic acid under the conditions of the ketoxime hydrolysis reaction, not only will caprolactam be wasted, but the hydrolysis product will also affect the quality of the caprolactam and hydroxylamine sulfate products. Therefore, in step S1 of the present invention, caprolactam can be extracted and separated at a lower temperature of 40-50°C, thereby avoiding the hydrolysis side reaction of caprolactam at high temperature, thereby improving the yield of caprolactam and product quality.

[0030] S2: adding ketoxime to the aqueous sulfuric acid solution or the aqueous hydroxylamine sulfate + sulfuric acid solution prepared in step S1 to undergo a hydrolysis reaction with the aqueous sulfuric acid solution or the aqueous hydroxylamine sulfate + sulfuric acid solution to produce an aqueous hydroxylamine sulfate solution and ketone, the reaction temperature being 70-90° C., the absolute pressure being 20-40 kPa, and the hydrolysis reaction time being 0.5-3.5 h; the produced ketone is separated in a separator and sent to a ketoxime preparation device for recycling, and the ketone is reacted with ammonia and hydrogen peroxide at a certain temperature under the action of a titanium silicon catalyst to produce ketoxime; the added ketoxime is a low-carbon ketoxime, preferably butanone oxime or cyclohexanone oxime. In one embodiment, the added ketoxime is butanone oxime, and the hydrolysis reaction produces butanone, which is sent to a butanone oxime device to produce butanone oxime, and the butanone oxime is recycled back to step S2 to undergo a hydrolysis reaction with the aqueous sulfuric acid solution or the aqueous hydroxylamine sulfate + sulfuric acid solution to produce hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1-1.3. In one specific embodiment, the feed composition by mass 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 ketone produced after the hydrolysis reaction is cyclohexanone. The cyclohexanone is fed to the ammoximation unit of the caprolactam plant to produce cyclohexanone oxime, which is used as a raw material for caprolactam production or is recycled back to step S2.

[0031] In this step, the ketoxime and the sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution can be subjected to a hydrolysis reaction in a reaction distillation tower, wherein the reaction distillation tower includes a tower top, a tower body, a tower bottom, a reflux system, a vacuum system, a temperature control system, multiple feed ports at the tower top and the tower bottom, and multiple discharge ports. The multiple feed ports of the reaction distillation tower are respectively connected to the bottom discharge port of the sulfur extraction tower and the discharge port of the ketoxime device. The sulfuric acid aqueous solution or the hydroxylamine sulfate + sulfuric acid aqueous solution discharged from the bottom discharge port of the sulfur extraction tower and the ketoxime discharged from the discharge port of the ketoxime device enter the reaction zone of the tower body from the feed port of the reaction distillation tower for hydrolysis reaction. The reaction temperature in the tower body is controlled to be 70-90° C. by a temperature control system, the absolute pressure in the tower body is controlled to be 20 kPa-40 kPa by a vacuum system, and the reflux ratio at the top of the tower is controlled to be 0.2-4 by a reflux system. After a hydrolysis reaction of 0.5 h to 3.5 h, a hydroxylamine sulfate aqueous solution and a ketone are generated. The ketone is discharged from the top discharge port of the reaction distillation tower and enters the reflux tank. After condensation and separation in the reflux tank, the water is refluxed into the reaction distillation tower, the ketone is discharged and enters the ketone oxime device, and the hydroxylamine sulfate aqueous solution is discharged from the bottom discharge port of the reaction distillation tower and enters the stripping tower for stripping and separation of a small amount of unreacted ketone oxime.

[0032] 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 significantly reduces the corrosiveness of the sulfuric acid solution caused by the increase in temperature and lowers the requirements for equipment materials, thereby reducing production costs.

[0033] S3: The hydroxylamine sulfate aqueous solution obtained in step S2 is stripped to separate 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 concentrated, crystallized, centrifugally filtered, and dried to obtain the product hydroxylamine sulfate. Specifically, crystallization can be performed in a crystallizer, followed by centrifugal separation in a centrifuge, and then dehydration in a dryer.

[0034] S4: After centrifugation, part of the hydroxylamine sulfate residue is sent to step S1 for hydrolysis of caprolactam sulfate. Preferably, 30-90% by mass of the hydroxylamine sulfate residue after centrifugation is returned to step S1 for hydrolysis of caprolactam sulfate, and the remaining hydroxylamine sulfate residue is sent to the oximation reactor for oximation reaction with ketone for recovery. Figure 3 The hydroxylamine sulfate residue after centrifugation in step S3 is reacted with ketone in an oximation reactor at a mass percentage of 10-70% by mass to produce ketone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 40-70°C and the pressure is atmospheric pressure. A small amount of aqueous ammonia is added to increase the oximation conversion rate. The reaction pH is adjusted to 3-6 before entering a separator for separation. The reaction mixture overflows from the top of the oximation reactor and enters the separator. In the separator, the reaction mixture naturally settles and separates into layers. The upper oil phase ketone oxime is sent to the ketone oxime preparation unit for purification, and the lower aqueous phase, the aqueous ammonium sulfate solution containing impurities and having the hydroxylamine sulfate removed, is sent to the ammonium sulfate unit of the caprolactam unit 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 ammonium sulfate solution is 0.5-2.5.

[0035] Caprolactam sulfate contains small amounts of organic and inorganic impurities. Organic impurities can be removed during the benzene extraction of caprolactam in step S1 and fed into the caprolactam unit. Inorganic impurities are water-soluble and accumulate with the hydroxylamine sulfate mother liquor. When they reach a certain concentration, they can affect the quality of the hydroxylamine sulfate product and require removal. The majority of the hydroxylamine sulfate residue (39% by mass at 30°C) containing accumulated impurities is recycled back to step S1 in step S4 to dilute the caprolactam sulfate. A separate stream is fed to the oximation reactor for impurity treatment. Example 1

[0036] S1: At 40°C and atmospheric pressure, 100 g of caprolactam sulfate is dissolved with 100 g of a 15% by mass aqueous solution of hydroxylamine sulfate to produce an aqueous solution of caprolactam sulfuric acid. Caprolactam is then extracted from the aqueous solution of caprolactam sulfuric acid with 800 g of benzene, yielding a raffinate phase of hydroxylamine sulfate and aqueous sulfuric acid and an extract phase of caprolactam organic solution. The organic solution is then transferred to a caprolactam unit for processing, yielding 48.5 g of caprolactam. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the aqueous solution of caprolactam sulfuric acid. The raffinate phase of hydroxylamine sulfate and aqueous sulfuric acid proceeds to step S2.

[0037] S2: 87 g of butanone oxime is added to the raffinate phase hydroxylamine sulfate + sulfuric acid aqueous solution. The butanone oxime undergoes a hydrolysis reaction with the hydroxylamine sulfate + sulfuric acid aqueous solution to produce the hydroxylamine sulfate aqueous solution and ketone. The reaction temperature is 70°C and the pressure is 20 kPa. The resulting butanone is separated in a separator and sent to the butanone oxime preparation unit. The butanone is then recycled back to step S2 to undergo a hydrolysis reaction with the hydroxylamine sulfate + sulfuric acid aqueous solution to produce hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1.

[0038] S3: After stripping the hydroxylamine sulfate aqueous solution obtained in step S2, 9 grams of unreacted ketoxime are separated and sent to step S2 to participate in the hydrolysis reaction. The hydroxylamine sulfate aqueous solution is concentrated, crystallized, centrifuged, filtered, and dried to obtain 73.5 grams of hydroxylamine sulfate product.

[0039] S4: 80% of the hydroxylamine sulfate residue after centrifugation and filtration in step S3 is reacted with a ketone in an oximation reactor to produce ketone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 40°C and the pressure is atmospheric pressure. A small amount of aqueous ammonia is added to adjust the reaction pH to 3. The reaction mixture then enters a separator for separation. The reaction mixture overflows from the top and enters the separator, where it naturally settles and separates. The upper oil phase, ketone oxime, is sent to the ketone oxime preparation unit for purification. The lower aqueous phase, ammonium sulfate aqueous solution containing impurities and free of hydroxylamine sulfate, is sent to the ammonium sulfate unit of the caprolactam unit for treatment. The molar ratio of ketone to hydroxylamine sulfate is 1, and the mass ratio of the oil phase to the aqueous phase is 0.5.

[0040] The caprolactam yield and hydroxylamine sulfate yield of this example are shown in Table 1.

[0041] Table 1

[0042] Example 2

[0043] S1: At 45°C and atmospheric pressure, 100 grams of caprolactam sulfate is dissolved in 500 grams of aqueous solution to produce a caprolactam sulfuric acid aqueous solution. Caprolactam is extracted from the caprolactam sulfuric acid aqueous solution using 3600 grams of benzene, yielding a raffinate phase of sulfuric acid aqueous solution and an extract phase of caprolactam organic solution. The caprolactam organic solution is then transferred to a caprolactam unit for processing, yielding 47.8 grams of caprolactam. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the caprolactam sulfuric acid aqueous solution. The raffinate phase of sulfuric acid aqueous solution enters step S2.

[0044] S2: 104.4 g of butanone oxime is added to the aqueous sulfuric acid solution in the raffinate phase. The butanone oxime undergoes a hydrolysis reaction with the aqueous sulfuric acid solution to produce an aqueous hydroxylamine sulfate solution and ketone. The reaction temperature is 80°C and the pressure is 35 kPa. The resulting butanone is separated in a separator and sent to the butanone oxime preparation unit. The product is then recycled back to step S2 for a hydrolysis reaction with the aqueous sulfuric acid solution to produce hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid is 1.2.

[0045] S3: After stripping the hydroxylamine sulfate aqueous solution obtained in step S2, 17.4 g of unreacted ketoxime was separated and sent to step S2 for hydrolysis reaction. The hydroxylamine sulfate aqueous solution was concentrated, crystallized, centrifuged, filtered, and dried to obtain 76.3 g of hydroxylamine sulfate product.

[0046] S4: 85% of the hydroxylamine sulfate residue after centrifugation and filtration in step S3 is reacted with a ketone in an oximation reactor to produce ketone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 55°C and the pressure is atmospheric pressure. A small amount of aqueous ammonia is added to adjust the reaction pH to 5. The reaction mixture then enters a separator for separation. The reaction mixture overflows from the top into the separator, where it naturally settles and separates. The upper oil phase, ketone oxime, is sent to the ketone oxime preparation unit for purification. The lower aqueous phase, ammonium sulfate aqueous solution containing impurities and free of hydroxylamine sulfate, 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.

[0047] The caprolactam yield and hydroxylamine sulfate yield of this example are shown in Table 2.

[0048] Table 2

[0049] Example 3

[0050] S1: At 50°C and atmospheric pressure, 100 g of caprolactam sulfate is dissolved with 1000 g of a 35% by mass aqueous solution of hydroxylamine sulfate to produce a caprolactam-sulfuric acid aqueous solution. Caprolactam is then extracted from the aqueous solution with 5000 g of benzene, yielding a raffinate phase consisting of hydroxylamine sulfate and aqueous sulfuric acid, and an extract phase consisting of an organic caprolactam solution. The organic caprolactam solution is then transferred to a caprolactam unit for processing, yielding 48.7 g of caprolactam. The separated benzene is refined and recycled to step S1 as an extractant to extract caprolactam from the aqueous solution of caprolactam-sulfuric acid. The raffinate phase consisting of hydroxylamine sulfate and aqueous sulfuric acid proceeds to step S2.

[0051] S2: 113.1 g of cyclohexanone oxime was added to the raffinate phase, and the butanone oxime and the hydroxylamine sulfate and sulfuric acid aqueous solution underwent a hydrolysis reaction to produce the hydroxylamine sulfate aqueous solution and butanone. The reaction temperature was 90°C and the pressure was 50 kPa. The resulting butanone was separated in a separator and sent to the butanone oxime preparation unit. The product was then recycled back to step S2 to undergo a hydrolysis reaction with the hydroxylamine sulfate and sulfuric acid aqueous solution to produce hydroxylamine sulfate. The molar ratio of butanone oxime to sulfuric acid was 1.3.

[0052] S3: The hydroxylamine sulfate aqueous solution obtained in step S2 is stripped to separate 34 g of unreacted ketoxime, which is sent to step S2 to participate in the hydrolysis reaction. The hydroxylamine sulfate aqueous solution is concentrated, crystallized, centrifuged, filtered, and dried to obtain 79 g of hydroxylamine sulfate product.

[0053] S4: 90% of the hydroxylamine sulfate residue after centrifugation and filtration in step S3 is reacted with a ketone in an oximation reactor to produce ketone oxime and an aqueous ammonium sulfate solution. The reaction temperature is 70°C and the pressure is atmospheric pressure. A small amount of aqueous ammonia is added to adjust the reaction pH to 6. The reaction mixture then enters a separator for separation. The reaction mixture overflows from the top and enters the separator, where it naturally settles and separates. The upper oil phase, ketone oxime, is sent to the ketone oxime preparation unit for purification. The lower aqueous phase, ammonium sulfate aqueous solution containing impurities and free of hydroxylamine sulfate, is sent to the ammonium sulfate unit of the caprolactam unit for treatment. The molar ratio of ketone to hydroxylamine sulfate is 1.2, and the mass ratio of the oil phase to the aqueous phase is 2.5.

[0054] The caprolactam yield and hydroxylamine sulfate yield of this example are shown in Table 3.

[0055] Table 3

[0056]

[0057] In summary, the preparation method of hydroxylamine sulfate provided in the present embodiment, with ketoxime and caprolactam sulfate as raw materials, is first parsed by caprolactam sulfate with water or an aqueous solution of hydroxylamine sulfate to obtain caprolactam sulfuric acid aqueous solution, then extracts and separates caprolactam and sulfuric acid aqueous solution, caprolactam can be separated out in advance at a lower temperature, thereby avoiding causing caprolactam to hydrolyze side reactions at high temperatures, and improving caprolactam yield and quality. Ketoxime reacts with sulfuric acid aqueous solution to prepare hydroxylamine sulfate, and there is no need to add sulfuric acid. At the same time, the separated ketone is circulated and applied, and caprolactam production is combined with hydroxylamine sulfate production to reduce ammonium sulfate by-products. Caprolactam and hydroxylamine sulfate are produced simultaneously, and a resource recycling and comprehensive utilization industry chain of caprolactam-ketoxime-co-production hydroxylamine sulfate is established to improve the comprehensive competitiveness of caprolactam products. At the same time, by first separating caprolactam, and recycling ketoxime, sulfuric acid aqueous solution is enabled to fully react, improve the yield of hydroxylamine sulfate, and reduce production costs. In addition, the preparation of ketoxime does not require a high conversion rate in the conversion process of ketone to oxime, and the unconverted ketone can be recycled back to the oximation reactor for oximation reaction with the residual hydroxylamine sulfate.

[0058] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the definition of the claims.

Claims

1. A method for preparing hydroxylamine sulfate, characterized in that: The steps include: S1: caprolactam sulfate is resolved with water or hydroxylamine sulfate aqueous solution to obtain caprolactam sulfuric acid aqueous solution; caprolactam is extracted and separated from the caprolactam sulfuric acid aqueous solution with an extractant to obtain a raffinate sulfuric acid aqueous solution or hydroxylamine sulfate + sulfuric acid aqueous solution and an extract phase 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; 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 recycled into step S1 as an extractant to extract caprolactam from the caprolactam sulfuric acid aqueous solution; this step uses a sulfur extraction tower, a hexane extraction tower and a residual extraction tower, the sulfur extraction tower is used to remove caprolactam in the sulfuric acid aqueous solution containing caprolactam. Amine is extracted, and benzene-hexyl liquid is formed at the top of the sulfur extraction tower, and sulfuric acid aqueous solution is formed at the bottom of the tower. The sulfuric acid aqueous solution is used for the ketoxime hydrolysis reaction in step S2; the benzene solvent in the benzene-hexyl liquid at the top of the sulfur extraction tower is recovered and recycled, the extract phase benzene-hexyl liquid coming out of the top of the sulfur extraction tower enters the hexyl extraction tower, the existing caprolactam crude oil enters the hexyl extraction tower, and the caprolactam crude oil is initially extracted, the benzene-hexyl liquid coming out of the hexyl extraction tower is sent to the benzene-hexyl pump tank to be refined in the existing caprolactam post-process, and benzene is recovered after post-process treatment, and the benzene is recycled for the sulfur extraction tower and the hexyl extraction tower. The hexyl extraction residue coming out of the hexyl extraction tower is sent to the residual extraction tower, and fresh benzene from the caprolactam device is used to extract the residual extraction tower. The benzene-hexyl liquid overflowing the residual extraction tower returns to the hexyl extraction tower and is used together with the benzene-hexyl liquid coming out of the sulfur extraction tower for extraction of the caprolactam crude oil. The extraction residue coming out of the residual extraction tower is sent to the existing caprolactam post-process for treatment; S2: adding ketoxime to the aqueous sulfuric acid solution or the aqueous solution of hydroxylamine sulfate + sulfuric acid solution obtained in step S1; hydrolyzing the ketoxime with the aqueous sulfuric acid solution or the aqueous solution of hydroxylamine sulfate + sulfuric acid solution to produce an aqueous solution of hydroxylamine sulfate and a ketone; and separating the produced ketone in a separator and sending it 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, centrifuged, filtered, and dried to obtain the product hydroxylamine sulfate; S4: returning part of the hydroxylamine sulfate residue after centrifugation and filtration in step S3 to step S1 for the resolution of caprolactam sulfate, and subjecting the remaining hydroxylamine sulfate residue to an oximation reaction with a ketone.

2. 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%.

3. 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 a hydroxylamine sulfate + sulfuric acid aqueous solution to prepare hydroxylamine sulfate.

4. The preparation method according to claim 3, characterized in that In step S2, during the hydrolysis reaction of butanone oxime and sulfuric acid, the temperature is 70-90° C., the pressure is 20-40 kPa absolute pressure, and the hydrolysis reaction time is 0.5-3.5 h; and the molar ratio of butanone oxime to sulfuric acid is 1-1.

3.

5. The preparation method according to claim 1, characterized in that The ketoxime 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, which is used as a raw material for producing caprolactam or recycled to step S2.

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

7. The preparation method according to claim 6, characterized in that In the oximation reactor, hydroxylamine sulfate and ketone undergo oximation reaction to generate ketoxime and ammonium sulfate, which are then separated by a separator.

8. The preparation method according to claim 7, 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. The reaction mixture overflows from the top of the oximation reactor into a separator, where the reaction mixture naturally settles and separates into layers. The oil phase ketoxime is sent to a ketoxime preparation device for purification, and the aqueous phase is an ammonium sulfate aqueous solution containing impurities and from which hydroxylamine sulfate has been removed, which is sent to the ammonium sulfate unit of a caprolactam device for treatment.

9. The preparation method according to claim 8, characterized in that In step S4, the oximation reaction temperature of the hydroxylamine sulfate residue and the ketone is 40-70° C. and the pressure is normal pressure; the molar ratio of the ketone to the hydroxylamine sulfate is 1-1.2, and the mass ratio of the oil phase ketoxime to the aqueous ammonium sulfate solution is 0.5-2.5.

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