Process for the preparation of cyclododecanone oxime, a preparation device and a process for the preparation of cyclododecanolactam

Abstract

The present application relates to the technical field of organic synthesis, and particularly relates to a preparation method and a preparation device of cyclododecanone oxime and a preparation method of dodecanolactam. The preparation method of cyclododecanone oxime comprises a first oximation stage and a second oximation stage which are cyclically performed. The first oximation stage comprises the following steps: after the mixture in the first oximation reactor meets the first condition, a first oximation reaction is performed, a first phase separation is performed, an oil phase and an aqueous phase are collected, and cyclododecanone oxime is separated from the oil phase. The second oximation stage comprises the following steps: the aqueous phase collected in the first oximation stage is transported to a second oximation reactor, the mixture in the second oximation reactor is adjusted to meet the second condition, a second oximation reaction is performed, a second phase separation is performed, an oil phase is collected, the oil phase is transported to the first oximation reactor, and the steps of the first oximation stage are repeated. The preparation method can improve the conversion rate and selectivity of cyclododecanone, improve the yield and purity of cyclododecanone oxime, and further realize the efficient production of dodecanolactam.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing cyclododecanone oxime, a preparation apparatus, and a method for preparing dodecyl lactam. Background Technology

[0002] Polydodecanoic acid (also known as nylon 12) is an engineering plastic that, in addition to the advantages of traditional polyamide materials, also possesses outstanding toughness, low-temperature resistance, low water absorption, high chemical stability, wear resistance, and lightweight properties. Currently, this material is mainly used in automotive fuel and gas pipelines, land and marine oil and gas transportation pipelines, high-end sports equipment, precision injection-molded wear-resistant parts, and advanced weapon components—applications requiring high-performance raw materials. Furthermore, it can be processed into ultrafine nylon powder through special processes for use in high-end powder coatings. The cured coating exhibits corrosion resistance and wear resistance, making it widely applicable in food contact applications, coastal protection, and outdoor equipment coatings.

[0003] However, the entire industrial chain for the preparation of Nylon 12 is lengthy, with harsh reaction conditions, involving various corrosive materials and complex reactors and separation operations. It typically uses cyclododecanetriene as a raw material, undergoing oxidation-hydrogenation and oxime rearrangement to obtain the polymer monomer dodecyllactam. The synthesis of dodecyllactam is a crucial step. Dodecyllactam usually uses cyclododecanone as a raw material, undergoing oxime reaction to generate cyclododecanone oxime, followed by rearrangement to obtain dodecyllactam. Although the chemical reaction forms of the preparation of dodecyllactam from cyclododecanone and cyclohexanone are similar, the significant differences in the physicochemical properties of cyclododecanone and its corresponding derivatives increase the technical difficulty of dodecyllactam production. Specifically, cyclododecanone is slightly soluble in water, while hydroxylamine is water-soluble but oil-insoluble, causing the oxime reaction to proceed in a liquid-liquid two-phase reaction, making mass transfer efficiency a critical issue. The oxime reaction is initially controlled by mass transfer, but in the final stage, it is jointly controlled by mass transfer and reaction, requiring high levels of process and engineering expertise. Poor mixed mass transfer results in low cyclododecanone conversion, numerous side reaction impurities, and a high risk of carbonization during subsequent rearrangement reactions, leading to pipeline blockage and reaction termination. Therefore, the synthesis of cyclododecanone oximes is a key factor restricting the entire industrial chain.

[0004] Patent document CN114787128A discloses a method for preparing dodecanolactam and its synthesis apparatus, a dodecanolactam composition prepared therefrom, and a method for preparing polydodecanolactam using the composition. It employs a catalytic system of cyanuric chloride and zinc chloride to rearrange cyclododecanone oxime to synthesize dodecanolactam, and then purifies the product using recrystallization. This catalytic system suffers from stability issues, and the dodecanolactam tends to agglomerate during recrystallization, making it difficult to implement in engineering and unsuitable for large-scale production. Patent document CN113769683A discloses a short-process continuous preparation system and method for dodecanolactam. However, due to the fast reaction and slow tailing characteristics of oxime reactions, this short-process method struggles to simultaneously achieve high conversion rates of cyclododecanone and hydroxylamine. High residual cyclododecanone levels can easily lead to carbonization and blockage in subsequent systems; high residual hydroxylamine levels can cause decomposition and gas generation in subsequent systems, resulting in overpressure and posing safety risks. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, one or more embodiments of the present invention provide a method for preparing cyclododecanone oxime, a preparation apparatus, and a method for preparing dodecanolactam. This preparation method can improve the conversion rate and selectivity of cyclododecanone, increase the yield and purity of cyclododecanone oxime, and thus achieve efficient production of dodecanolactam.

[0006] The technical solution of the present invention includes the following contents:

[0007] A first aspect of the present invention provides a method for preparing cyclododecanone oxime, comprising a first oxime phase and a second oxime phase carried out in cycles;

[0008] The first oxime phase includes the following steps:

[0009] After adjusting the mixture in the first oxime reactor to meet the first condition, the first oxime reaction is carried out to obtain the first reaction solution;

[0010] The first condition includes conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; and (iii) the pH is 6-7.5.

[0011] After the first reaction solution is subjected to a first phase separation, the oil phase and the aqueous phase are collected; cyclododecanone oxime is obtained from the oil phase;

[0012] The second oxime stage includes the following steps:

[0013] The aqueous phase collected in the first oxime stage is transported to the second oxime reactor, and after the mixture in the second oxime reactor is adjusted to meet the second conditions, the second oxime reaction is carried out to obtain the second reaction solution.

[0014] The second condition includes conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone to hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4;

[0015] After the second reaction solution undergoes a second phase separation, the oil phase is collected.

[0016] The oil phase collected in the second oxime stage is transported to the first oxime reactor, and the steps of the first oxime stage are repeated.

[0017] The mixture in the first oxime reactor and the second oxime reactor satisfies the following condition: the molar ratio of cyclododecanone to hydroxylamine is 1:(1-1.2).

[0018] In some embodiments, the mixture in the first oxime reactor and the second oxime reactor each independently further includes a first catalyst.

[0019] In some embodiments, the first catalyst includes one or more of dodecanoic acid, methylbenzenesulfonic acid, and aminododecanoic acid.

[0020] In some embodiments, the mass ratio of the first catalyst to cyclododecane in the mixture in the first oxime reactor is (0.1-2):100.

[0021] In some embodiments, the mass ratio of the first catalyst to hydroxylamine in the mixture in the second oxime reactor is (0.1-2):100.

[0022] In some embodiments, before performing the first phase separation on the first reaction solution, the pH of the first reaction solution is adjusted to 8-10.

[0023] In some embodiments, the pH of the aqueous phase collected in the first oxime stage is adjusted to 1-4 before being transported to the second oxime reactor.

[0024] In some embodiments, the volume ratio of water to organic solvent in the mixture in the first oxime reactor is 1:(0.5-1.5).

[0025] In some embodiments, the volume ratio of water to organic solvent in the mixture in the second oxime reactor is 1:(0.5-1.5).

[0026] In some embodiments, the organic solvent in the mixture in the first oxime reactor includes saturated cycloalkanes.

[0027] In some embodiments, the organic solvent in the mixture in the second oxime reactor includes saturated cycloalkanes.

[0028] In some embodiments, the saturated cycloalkane includes one or more of methylcyclohexane, ethylcyclohexane, and isopropylcyclohexane.

[0029] In some embodiments, adjusting the mixture in the first oxime reactor to satisfy condition (i) of the first condition includes supplying hydroxylamine to the first oxime reactor.

[0030] In some embodiments, adjusting the mixture in the second oxime reactor to meet condition (iv) of the first condition includes feeding cyclododecanone into the second oxime reactor.

[0031] In some embodiments, the molar ratio of the hydroxylamine delivered to the first oxime reactor and the cyclododecanone delivered to the second oxime reactor is 1:(1-1.2).

[0032] In some embodiments, the first oxime reaction is carried out under stirring; the stirring speed is 900 rpm-1000 rpm.

[0033] In some embodiments, the conditions for the first oxime reaction include: a reaction temperature of 80°C-100°C, a reaction pressure of 0.1 MPa-0.5 MPa, and a reaction time of 0.5 h-2 h.

[0034] In some embodiments, the second oxime reaction is carried out under stirring; the stirring speed is 900 rpm-1000 rpm.

[0035] In some embodiments, the conditions for the second oxime reaction include: a reaction temperature of 80°C-100°C, a reaction pressure of 0.1 MPa-0.5 MPa, and a reaction time of 0.5 h-2 h.

[0036] A second aspect of the present invention provides an apparatus for preparing cyclododecanone oxime, comprising a first oximation reactor, a first phase separator, a second oximation reactor, and a second phase separator connected in sequence by a delivery pipe;

[0037] The first oxime reactor has an input end and an output end;

[0038] The first phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal;

[0039] The second oxime reactor has an input end and an output end;

[0040] The second phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal;

[0041] The output end of the first oxime reactor and the input end of the first phase separator, the aqueous phase output end of the first phase separator and the input end of the second oxime reactor, the output end of the second oxime reactor and the input end of the second phase separator, and the oil phase output end of the second phase separator and the input end of the first oxime reactor are respectively connected by the conveying pipe;

[0042] The first oxime reactor is used to adjust the mixture in the first oxime reactor to meet the first conditions, and then carry out the first oxime reaction to obtain the first reaction solution; the first conditions include conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; (iii) the pH is 6-7.5;

[0043] The first phase separator is used to separate the first reaction liquid into two phases and output the oil phase and the water phase respectively;

[0044] The second oxime reactor is used to transport the aqueous phase collected in the first oxime stage to the second oxime reactor, and after adjusting the mixture in the second oxime reactor to meet the second conditions, carry out the second oxime reaction to obtain the second reaction solution; the second conditions include conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone and hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4;

[0045] The second phase separator is used to separate the second reaction liquid into two phases, and output the oil phase and the water phase respectively.

[0046] In some embodiments, a first mixer is further provided between the first oxime reactor and the first phase separator;

[0047] The first mixer is used to mix the reaction solution output from the first oxime reactor with alkali and adjust the pH of the resulting mixture to 8-10.

[0048] In some embodiments, a second mixer is further provided between the second phase separator and the second oxime reactor;

[0049] The second mixer is used to mix the aqueous phase output from the second phase separator with acid, and adjust the pH of the resulting mixture to 1-4.

[0050] A third aspect of the present invention provides a method for preparing dodecanolactam, wherein cyclododecanone oxime is prepared using the preparation method or the preparation apparatus described above;

[0051] The dodecanolide was subjected to a Beckmann rearrangement reaction to obtain the dodecanolactam.

[0052] In some embodiments, the Beckmann rearrangement reaction is carried out in the presence of a second catalyst.

[0053] In some embodiments, the second catalyst comprises one or more of sulfuric acid, polyphosphoric acid, phosphorus pentachloride, phosphorus trichloride, benzenesulfonyl chloride, and thionyl chloride.

[0054] In some embodiments, the conditions for the Beckmann rearrangement reaction include: a reaction temperature of 60°C-150°C, a reaction pressure of 0.2 MPa-1 MPa, and a reaction time of 0.5 min-30 min.

[0055] The beneficial effects of this invention include:

[0056] The method for preparing cyclododecanone oxime of the present invention employs a cyclic first oximation stage and a second oximation stage. The first oximation stage is carried out in a first oximation reactor, adjusting the molar ratio of hydroxylamine to cyclododecanone to (1-10):1, using an oil-water mixture as the solvent environment, with a pH of 6-7.5. The hydroxylamine compound (e.g., hydroxylamine sulfate) can rapidly release free hydroxylamine, and the high activity of hydroxylamine promotes rapid reaction. Hydroxylamine is relatively in excess at the reaction center, thereby improving the conversion rate and reaction efficiency of cyclododecanone. After the first oximation reaction, the resulting first reaction solution undergoes a first phase separation, collecting the oil phase and the aqueous phase. The oil phase is used to prepare the product cyclododecanone oxime; the aqueous phase contains unreacted hydroxylamine and is collected for the second oximation stage. The second oximation stage is carried out in a second oximation reactor, to which the first oximation reaction stage is fed. After recovering the aqueous phase, the molar ratio of cyclododecanone and hydroxylamine is adjusted to (1-10):1, the solvent environment is an oil-water mixture, the pH is 1-4, and the hydroxylamine compound (e.g., hydroxylamine sulfate) exists in salt form, avoiding decomposition, while slowly releasing free hydroxylamine. Cyclododecanone is relatively in excess at the reaction center, thus completely consuming the hydroxylamine remaining in the aqueous phase. After the second oximation reaction, the resulting second reaction solution undergoes a second phase separation, and the oil phase is collected, which contains the product cyclododecanone oxime and unreacted cyclododecanone. This oil phase is then transported to the first oximation reactor, where cyclododecanone is recovered and reused. Furthermore, the product cyclododecanone oxime is combined with the product cyclododecanone oxime continuously generated in the first oximation reactor, and together they are output as the oil phase of the first oximation stage, achieving a single output end and multi-step recovery and reuse of raw materials. The above-mentioned continuous two-stage oxime process significantly improves the conversion rate and selectivity of cyclododecanone to cyclododecanone oxime, increases the yield and purity of cyclododecanone oxime, and reduces hydroxylamine residue. In addition, during the continuous reaction process, the sum of the mixtures in the first and second oxime reactors is controlled to meet the following condition: the molar ratio of cyclododecanone to hydroxylamine is 1:(1-1.2). This ensures that cyclododecanone is almost completely converted while minimizing the excess of hydroxylamine, reducing raw material waste, alleviating wastewater treatment pressure, and improving the purity of the final product.

[0057] The apparatus for preparing cyclododecanone oxime of the present invention can continuously carry out the first oximation stage and the second oximation stage. The apparatus can continuously output high-purity cyclododecanone oxime, realize the continuous production of cyclododecanone oxime, improve production efficiency, and reduce operating costs.

[0058] The method for preparing dodecanolactam of the present invention uses the same method or apparatus for preparing cyclododecanone oxime as described in the present invention, enabling a continuous output of high-purity cyclododecanone oxime. The efficient preparation of dodecanolactam is achieved through a Beckmann rearrangement reaction of the cyclododecanone oxime. This method can produce high-purity dodecanolactam monomers. Attached Figure Description

[0059] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0060] Figure 1 This is a process flow diagram of cyclododecanone oxime according to an embodiment of the present invention.

[0061] Figure 2 This is a process flow diagram of dodecyl lactam according to an embodiment of the present invention. Detailed Implementation

[0062] The present invention will be further described below with reference to embodiments and examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the protection scope of the appended claims.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0064] The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations encompass any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this invention, the technical solution undoubtedly includes solutions connected using "logical AND," and also undoubtedly includes solutions connected using "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0065] In this article, terms such as "preferred," "better," and "more preferred" are merely descriptions of implementation methods or examples that achieve better results, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0066] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0067] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0068] In this invention, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, optional numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval points to an integer within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0069] In this invention, weight can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.

[0070] A first aspect of the present invention provides a method for preparing cyclododecanone oxime, comprising a first oxime phase and a second oxime phase carried out in cycles;

[0071] The first oxime stage includes the following steps:

[0072] After adjusting the mixture in the first oxime reactor to meet the first condition, the first oxime reaction is carried out to obtain the first reaction solution;

[0073] The first condition includes conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; and (iii) the pH is 6-7.5.

[0074] After the first reaction solution was subjected to the first phase separation, the oil phase and the aqueous phase were collected; cyclododecanone oxime was obtained from the oil phase.

[0075] The second oxime stage includes the following steps:

[0076] The aqueous phase collected in the first oxime stage is transported to the second oxime reactor, and after the mixture in the second oxime reactor is adjusted to meet the second conditions, the second oxime reaction is carried out to obtain the second reaction solution.

[0077] The second condition includes conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone to hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4;

[0078] After the second reaction solution undergoes a second phase separation, the oil phase is collected.

[0079] The oil phase collected in the second oxime stage is transferred to the first oxime reactor, and the steps of the first oxime stage are repeated.

[0080] The mixture in the first oxime reactor and the second oxime reactor satisfies the following condition: the molar ratio of cyclododecanone to hydroxylamine is 1:(1-1.2).

[0081] In some embodiments, the molar ratio of hydroxylamine to cyclododecanone in the mixture in the first oxime reactor is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0082] In some embodiments, the molar ratio of cyclododecanone to hydroxylamine in the mixture in the second oxime reactor is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0083] The method for preparing cyclododecanone oxime of the present invention employs a cyclic first oximation stage and a second oximation stage. The first oximation stage is carried out in a first oximation reactor, adjusting the molar ratio of hydroxylamine to cyclododecanone to (1-10):1, using an oil-water mixture as the solvent environment, with a pH of 6-7.5. The hydroxylamine compound (e.g., hydroxylamine sulfate) can rapidly release free hydroxylamine, and the high activity of hydroxylamine promotes rapid reaction. Hydroxylamine is relatively in excess at the reaction center, thereby improving the conversion rate and reaction efficiency of cyclododecanone. After the first oximation reaction, the resulting first reaction solution undergoes a first phase separation, collecting the oil phase and the aqueous phase. The oil phase is used to prepare the product cyclododecanone oxime; the aqueous phase contains unreacted hydroxylamine and is collected for the second oximation stage. The second oximation stage is carried out in a second oximation reactor, to which the first oximation reaction stage is fed. After recovering the aqueous phase, the molar ratio of cyclododecanone and hydroxylamine is adjusted to (1-10):1, the solvent environment is an oil-water mixture, the pH is 1-4, and the hydroxylamine compound (e.g., hydroxylamine sulfate) exists in salt form, avoiding decomposition, while slowly releasing free hydroxylamine. Cyclododecanone is relatively in excess at the reaction center, thus completely consuming the hydroxylamine remaining in the aqueous phase. After the second oximation reaction, the resulting second reaction solution undergoes a second phase separation, and the oil phase is collected, which contains the product cyclododecanone oxime and unreacted cyclododecanone. This oil phase is then transported to the first oximation reactor, where cyclododecanone is recovered and reused. Furthermore, the product cyclododecanone oxime is combined with the product cyclododecanone oxime continuously generated in the first oximation reactor, and together they are output as the oil phase of the first oximation stage, achieving a single output end and multi-step recovery and reuse of raw materials. The above-mentioned two-stage oxime process significantly improved the conversion rate and selectivity of cyclododecanone to cyclododecanone oxime, increased the yield and purity of cyclododecanone oxime, and reduced hydroxylamine residue.

[0084] In some embodiments, the conversion of cyclododecanone to cyclododecanone oxime is ≥99.80%, the selectivity is ≥99.90%, and the residual hydroxylamine content is ≤0.15%.

[0085] In some embodiments, the mixtures in the first oxime reactor and the second oxime reactor each independently further include a first catalyst. The first catalyst is used to catalyze the oxime reaction of hydroxylamine and cyclododecanone.

[0086] In some embodiments, the mass ratio of the first catalyst to cyclododecanone in the mixture in the first oxime reactor is (0.1-2):100, for example, it can be 0.1:100, 0.2:100, 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, etc.

[0087] In some embodiments, the mass ratio of the first catalyst to hydroxylamine in the mixture in the second oxime reactor is (0.1-2):100, for example, it can be 0.1:100, 0.2:100, 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, etc.

[0088] In some embodiments, the first catalyst includes one or more of dodecanoic acid, methylbenzenesulfonic acid, and aminododecanic acid. Using the above-mentioned first catalyst enables its recycling. Taking dodecanoic acid as an example, in an oil-water two-phase mixed solvent, dodecanoic acid is mainly distributed in the oil phase under acidic conditions and mainly distributed in the aqueous phase under alkaline conditions. Therefore, by adjusting the pH value, dodecanoic acid can be recycled in the oxime reaction system. Specifically, before the first phase separation of the first reaction solution, the pH of the first reaction solution is adjusted to an alkaline environment (e.g., pH 8-10) to transfer dodecanoic acid to the aqueous phase. The aqueous phase is recovered not only from hydroxylamine but also from dodecanoic acid, and the recovered aqueous phase is then used in the second oxime reaction stage, allowing the second oxime reaction stage to require little or no addition of new catalyst. After the second oxime reaction, the pH of the reaction solution remains essentially unchanged, maintaining an acidic state (pH approximately 1-4). After the second phase separation, dodecanoic acid is transferred to the oil phase. The oil phase is recovered not only from cyclododecanone and the product cyclododecanone oxime but also from dodecanoic acid, and the recovered oil phase is then used in the first oxime reaction stage, allowing the first oxime reaction stage to require little or no addition of new catalyst. Through the above steps, the recycling of the first catalyst is achieved.

[0089] In some embodiments, the pH of the first reaction solution is adjusted to 8-10 before the first phase separation is performed.

[0090] In some embodiments, the step of adjusting the pH of the first reaction solution to 8-10 includes: adding an alkali to the first reaction solution and mixing. Optionally, the alkali includes one or more of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0091] In some embodiments, the pH of the aqueous phase collected in the first oxime stage is adjusted to 1-4 before being transferred to the second oxime reactor.

[0092] In some embodiments, the step of adjusting the pH of the aqueous phase to 1-4 includes adding an acid mixture to the aqueous phase. Optionally, the acid includes one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0093] In some embodiments, the volume ratio of water to organic solvent in the mixture in the first oxime reactor is 1:(0.5-1.5), for example, it can be 1:0.5, 1:1, 1:1.5, etc.

[0094] In some embodiments, the volume ratio of water to organic solvent in the mixture in the second oxime reactor is 1:(0.5-1.5), for example, it can be 1:0.5, 1:1, 1:1.5, etc.

[0095] Using a suitable water-to-oil ratio (volume ratio of hydrated organic solvent) can allow hydroxylamine and cyclododecone to dissolve simultaneously, improving the mass transfer efficiency of the reaction, thereby increasing the reaction efficiency and conversion rate.

[0096] In some embodiments, the organic solvent in the mixture in the first oxime reactor includes saturated cycloalkanes.

[0097] In some embodiments, the organic solvent in the mixture in the second oxime reactor includes saturated cycloalkanes;

[0098] In some embodiments, saturated cycloalkane includes one or more of methylcyclohexane, ethylcyclohexane, and isopropylcyclohexane.

[0099] In some embodiments, adjusting the mixture in the first oxime reactor to satisfy condition (i) of the first condition includes supplying hydroxylamine to the first oxime reactor.

[0100] In some embodiments, adjusting the mixture in the first oxime reactor to meet condition (ii) of the first condition includes feeding an aqueous solution containing hydroxylamine and an organic solution containing cyclododecanone into the first oxime reactor.

[0101] In some embodiments, adjusting the mixture in the first oxime reactor to meet condition (iii) of the first condition includes supplying an alkali mixture to the first oxime reactor to adjust the pH value. Optionally, the alkali includes one or more of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0102] In some embodiments, the first oxime reaction is carried out under stirring; the stirring speed is 900 rpm-1000 rpm. A suitable stirring speed can promote sufficient contact between the water and organic solvent phases, improve the mass transfer efficiency of the reaction, and thus improve the reaction efficiency and conversion rate.

[0103] In some embodiments, the conditions for the first oxime reaction include: a reaction temperature of 80°C-100°C, a reaction pressure of 0.1 MPa-0.5 MPa, and a reaction time of 0.5 h-2 h.

[0104] In some embodiments, adjusting the mixture in the second oxime reactor to meet condition (iv) of the second condition includes feeding cyclododecanone into the second oxime reactor.

[0105] In some embodiments, adjusting the mixture in the second oxime reactor to meet condition (v) of the second condition includes feeding an aqueous solution containing hydroxylamine and an organic solution containing cyclododecanone into the first oxime reactor.

[0106] In some embodiments, adjusting the mixture in the second oxime reactor to meet condition (vi) of the second condition includes supplying an acid mixture to the first oxime reactor to adjust the pH value. Optionally, the acid includes one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0107] In some embodiments, the second oxime reaction is carried out under stirring; the stirring speed is 900 rpm-1000 rpm.

[0108] In some embodiments, the conditions for the second oxime reaction include: a reaction temperature of 80°C-100°C, a reaction pressure of 0.1 MPa-0.5 MPa, and a reaction time of 0.5 h-2 h.

[0109] A second aspect of the present invention provides an apparatus for preparing cyclododecanone oxime, comprising a first oximation reactor, a first phase separator, a second oximation reactor, and a second phase separator connected in sequence by a delivery pipe;

[0110] The first oxime reactor has an input end and an output end;

[0111] The first phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal;

[0112] The second oxime reactor has an input end and an output end;

[0113] The second phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal;

[0114] The output end of the first oxime reactor and the input end of the first phase separator, the aqueous phase output end of the first phase separator and the input end of the second oxime reactor, the output end of the second oxime reactor and the input end of the second phase separator, and the oil phase output end of the second phase separator and the input end of the first oxime reactor are respectively connected by conveying pipes;

[0115] The first oxime reactor is used to adjust the mixture in the first oxime reactor to meet the first conditions, and then carry out the first oxime reaction to obtain the first reaction solution; the first conditions include conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; (iii) the pH is 6-7.5.

[0116] The first phase separator is used to separate the first reaction liquid into two phases and output the oil phase and the water phase respectively;

[0117] The second oxime reactor is used to transport the aqueous phase collected in the first oxime stage to the second oxime reactor, and after adjusting the mixture in the second oxime reactor to meet the second conditions, the second oxime reaction is carried out to obtain the second reaction solution; the second conditions include conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone and hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4;

[0118] The second phase separator is used to separate the second reaction liquid into oil and water phases, respectively.

[0119] In some embodiments, a first mixer is further provided between the first oxime reactor and the first phase separator;

[0120] The first mixer is used to mix the reaction solution output from the first oxime reactor with alkali and adjust the pH of the resulting mixture to 8-10.

[0121] Dodecanoic acid can be recycled in the oxime reaction system by adjusting the pH value. Specifically, after the first reaction liquid is output from the first oximation reactor, it is first sent to the first mixer to adjust the pH of the first reaction liquid to an alkaline environment (e.g., pH 8-10), causing dodecanoic acid to transfer to the aqueous phase. Then, it is sent to the first phase separator. The output aqueous phase includes not only unreacted hydroxylamine but also the first catalyst. This aqueous phase is then sent to the second oximation reactor, allowing for minimal or no addition of new catalyst. After the second reaction liquid is output from the second oximation reactor, since its pH is maintained at an acidic level (approximately pH 1-4), the first catalyst is present in the oil phase. This oil phase can be directly input into the second phase separator for second phase separation. The output oil phase includes not only the product generated in the second oximation reactor and the reacted cyclododecanone but also the catalyst dodecanoic acid. This oil phase is then returned to the first oximation reactor, allowing for minimal or no addition of new catalyst. Through these steps, the first catalyst is recycled.

[0122] In some embodiments, a second mixer is further provided between the second phase separator and the second oxime reactor;

[0123] The second mixer is used to mix the aqueous phase output from the second phase separator with acid, and adjust the pH of the resulting mixture to 1-4.

[0124] The apparatus for preparing cyclododecanone oxime of the present invention can continuously carry out the first oximation stage and the second oximation stage. The apparatus can continuously output high-purity cyclododecanone oxime, realize the continuous production of cyclododecanone oxime, improve production efficiency, and reduce operating costs.

[0125] In some embodiments, the step of continuous production of cyclododecanone oxime using the above-described apparatus includes:

[0126] Preparation of cyclododecanone solution: The solvent includes one or more saturated cycloalkanes such as methylcyclohexane, ethylcyclohexane, and isopropylcyclohexane; the solute includes cyclododecanone and a first catalyst; the mass content of cyclododecanone is 0.1%-50%, preferably 20%-30%; the first catalyst is preferably dodecanoic acid; the mass ratio of the first catalyst to cyclododecanone is (0.1-2):100, preferably (0.1-0.5):100;

[0127] Preparation of hydroxylamine solution: The solvent is water, and the hydroxylamine source includes one or more of hydroxylamine sulfate and hydroxylamine hydrochloride, preferably hydroxylamine sulfate; the mass content of hydroxylamine is 0.1%-50%, preferably 10%-20%;

[0128] Bottom-laying reaction: Appropriate amounts of cyclododecanone solution and hydroxylamine solution are introduced into the first oxime reactor for bottom-laying reaction until the cyclododecanone conversion rate is ≥99.80%; appropriate amounts of cyclododecanone solution and hydroxylamine solution are then introduced into the second oxime reactor for bottom-laying reaction until the residual hydroxylamine content is ≤0.15%;

[0129] First-stage oximation reaction: Hydroxylamine solution is continuously fed into the first oximation reactor at a suitable rate. After the pH value is maintained within a suitable range by supplying alkali, the first oximation reaction is carried out to obtain the first reaction solution. The first reaction solution is fed into the first mixer. After the pH value is maintained within a suitable range by supplying alkali, the resulting mixture is fed into the first phase separator for the first phase separation. The resulting oil phase (first oil phase) is fed into the rearrangement reactor for subsequent rearrangement reaction, while the aqueous phase is fed into the second mixer.

[0130] Second stage oximation reaction: Acid is supplied to the second mixer to maintain the pH value within a suitable range. The resulting mixture is then supplied to the second oximation reactor. At the same time, the cyclododecanone solution is continuously supplied to the second oximation reactor at a suitable rate to carry out the second oximation reaction and obtain the second reaction solution.

[0131] Recycled: The second reaction liquid is sent to the second phase separator for the second phase separation. The resulting oil phase (second oil phase) is sent to the first oxime reactor to repeat the first oxime reaction steps. The aqueous phase (second aqueous phase) enters the water treatment system.

[0132] In some embodiments, in addition to conventional thermometers, pressure gauges, level gauges, nitrogen pipelines, tail gas pipelines, safety valves, etc., the first and second oxime reactors are also equipped with online pH meters. The reactors are internally divided into axial flow and high-speed multi-stage stirring paddles with a stirring speed of 900 rpm-1000 rpm, which can realize the rapid mixing of two-phase materials to achieve an emulsified state.

[0133] In some embodiments, the molar ratio of hydroxylamine to cyclododecanone, based on the total input, is (1-1.2):1, preferably (1.01-1.05):1.

[0134] In some embodiments, both the first and second phase separators are designed with coalescers, which can control the phase separation interface at a suitable position, such as 30%-50%, to ensure that the oil and water phases have appropriate residence time and avoid mutual entrainment.

[0135] In some embodiments, the appropriate dwell time is 10 min-60 min, preferably 20 min-30 min.

[0136] A third aspect of the present invention provides a method for preparing dodecanolactam, wherein cyclododecanone oxime is prepared using the preparation method or the preparation apparatus described above;

[0137] The dodecanolide was subjected to a Beckmann rearrangement reaction to obtain the dodecanolactam.

[0138] The method for preparing dodecanolactam of the present invention uses the same method or apparatus for preparing cyclododecanone oxime as described in the present invention, enabling a continuous output of high-purity cyclododecanone oxime. The efficient preparation of dodecanolactam is achieved through a Beckmann rearrangement reaction of the cyclododecanone oxime. This method can produce high-purity dodecanolactam monomers.

[0139] In some embodiments, the Beckmann rearrangement reaction is carried out in the presence of a second catalyst.

[0140] In some embodiments, the conditions for the Beckmann rearrangement reaction include: a reaction temperature of 60°C-150°C, a reaction pressure of 0.2 MPa-1 MPa, and a reaction time of 0.5 min-30 min, preferably 3 min-10 min.

[0141] In some embodiments, the second catalyst comprises one or more of sulfuric acid, polyphosphoric acid, phosphorus pentachloride, phosphorus trichloride, benzenesulfonyl chloride, and thionyl chloride.

[0142] In some embodiments, the second catalyst is concentrated sulfuric acid or fuming sulfuric acid with a mass fraction ≥96%, and the mass ratio of the catalyst to cyclododecanone oxime is (0.5-2):1.

[0143] In some embodiments, after performing the Beckmann rearrangement reaction on cyclododecanone oxime, the resulting rearrangement reaction solution is neutralized with ammonia to a pH of 8-12, preferably 9-10. After neutralization, the phases are separated, and the oil phase is fed into a water washing system. The oil phase is washed with pure water until the pH is around 7. After phase separation, a solution containing dodecyl lactam is obtained.

[0144] In some embodiments, the solution containing dodecyl lactam obtained after phase separation is subjected to distillation. The solvent removal operation pressure is 5-35 kPaA, the operation temperature is 100-250°C, and the theoretical plate number is 4-10. The product separation distillation operation pressure is 0.5 kPaA-1 kPaA (kilopascal absolute pressure), the operation temperature is 150°C-300°C, and the theoretical plate number is 5-20.

[0145] In some embodiments, the purity of the dodecanoic acid obtained after distillation is ≥99.90%, and the transmittance of the standard solution is ≥95%.

[0146] The following are some specific examples.

[0147] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this invention document, or consult experimental manuals or other experimental methods known in the art, or refer to the manufacturer's recommended experimental conditions. Raw materials and reagents not mentioned can be obtained commercially, or can be prepared by those skilled in the art using known methods.

[0148] The raw materials used in the following examples or comparative examples are from the following sources:

[0149] Cyclododecone (≥99.5%), CAS: 830-13-7, purchased from Wanhua Chemical Group Co., Ltd.

[0150] Ethylcyclohexane (≥99%), CAS: 1678-91-7, purchased from Beijing Innocare Technology Co., Ltd.;

[0151] Methylcyclohexane (≥99%), CAS: 108-87-2, purchased from Beijing Innocare Technology Co., Ltd.

[0152] Cyclododecanone oxime (≥98%), CAS: 946-89-4, purchased from Wanhua Chemical Group Co., Ltd.

[0153] Ammonia water (25%), CAS: 1336-21-6, purchased from Wanhua Chemical Group Co., Ltd.

[0154] Hydroxylamine sulfate (99%), CAS: 10039-54-0, purchased from Wanhua Chemical Group Co., Ltd.

[0155] Sulfuric acid (98%), CAS: 7664-93-9, purchased from Beijing Innocare Technology Co., Ltd.

[0156] Fuming sulfuric acid (105%), CAS: 7664-93-9, purchased from Beijing Innocare Technology Co., Ltd.

[0157] Dodecanoic acid (99%), CAS: 693-23-2, purchased from Beijing Innocare Technology Co., Ltd.;

[0158] Anhydrous ethanol (AR), CAS: 64-17-5, purchased from Beijing Innocare Technology Co., Ltd.

[0159] Cyclododecylimine reference standard, CAS: 2954116-57-3, purchased from Wanhua Chemical Group Co., Ltd.

[0160] Example 1

[0161] In this embodiment, the preparation of cyclododecanone oxime is carried out using apparatus 1 and rearrangement reaction apparatus 2.

[0162] like Figure 1 The apparatus 1 for preparing cyclododecanone oxime includes a first oxime reactor 11, a first mixer 12, a first phase separator 13, a second mixer 14, a second oxime reactor 15, and a second phase separator 16.

[0163] The output end of the first oxime reactor 11 and the input end of the first mixer 12 are connected by a delivery pipe 31;

[0164] The output of the first mixer 12 and the input of the first phase splitter 13 are connected by a delivery pipe 32;

[0165] The water phase output terminal of the first phase separator 13 and the input terminal of the second mixer 14 are connected by a delivery pipe 33.

[0166] The output end of the second mixer 14 and the input end of the second oxime reactor 15 are connected by a delivery pipe 34;

[0167] The output end of the second oxime reactor 15 and the input end of the second phase separator 16 are connected by a delivery pipe 35.

[0168] The oil phase output end of the second phase separator 16 and the input end of the first oxime reactor 11 are connected by a delivery pipe 36.

[0169] like Figure 2 The rearrangement reaction apparatus 2 includes a rearrangement reactor 21, a neutralization phase separator 22, a water washing vessel 23, and a distillation system 24;

[0170] The oil phase output end of the first phase separator 13 and the input end of the rearrangement reactor 21 are connected by a delivery pipe 41;

[0171] The output end of the rearrangement reactor 21 and the input end of the neutralization reactor 22 are connected by a conveying pipe 42;

[0172] The output end of the neutralization reactor 22 and the input end of the water washing vessel 23 are connected by a conveying pipe 43;

[0173] The output end of the water washing vessel 23 and the input end of the distillation system 24 are connected by a delivery pipe 44.

[0174] The preparation steps are as follows:

[0175] (1) Preparation of raw materials and base

[0176] Raw material A: Take 458.8 kg of hydroxylamine sulfate and add 2599.9 kg of water to prepare a 15% hydroxylamine sulfate aqueous solution.

[0177] Raw material B: Take 1000.0 kg of cyclododecanone, dissolve it in 2333.3 kg of ethylcyclohexane, add 3.0 kg of dodecanoic acid (first catalyst), and dissolve it with ultrasonic assistance until it is clear, so as to prepare a cyclododecanone solution with a mass fraction of 30%.

[0178] Base reaction:

[0179] 1) 15.3 kg of raw material A and 8.4 kg of raw material B are transported to the first oxime reactor 11 and mixed. The stirring speed is adjusted to 900 rpm. Ammonia water is added until the online pH meter shows about 7. The reaction temperature is controlled at 90±2℃ and the pressure is 0.2 MPa. The mixture is reacted and samples are taken periodically until the cyclododecanone conversion rate is ≥99.80%.

[0180] 2) 7.7 kg of raw material A and 16.7 kg of raw material B are transported to the second oxime reactor 15 and mixed. The stirring speed is adjusted to 900 rpm. Sulfuric acid is added until the pH meter shows a range of 2-3. The reaction temperature is controlled at 90±2℃ and the pressure is 0.2 MPa. The mixture is mixed and reacted. Samples are taken periodically until the residual hydroxylamine is ≤0.15%.

[0181] (2) Continuous oxime reaction

[0182] First stage of oxime reaction:

[0183] like Figure 1 Raw material A (an aqueous solution of hydroxylamine) is continuously fed into the first oxime reactor 11 at a rate of 30.6 kg / h. Ammonia water (alkali) is fed to maintain the pH value at about 7. The reaction temperature is controlled at about 90℃, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the first reaction solution.

[0184] The first reaction solution is delivered to the first mixer 12, and ammonia (alkali) is delivered to maintain the pH value at around 8.5;

[0185] The resulting mixture is fed to the first phase separator 13 for the first phase separation, with the oil-water interface controlled at 50% and the residence time at 20 minutes. The resulting oil phase (first oil phase) is then fed to the rearrangement reactor 21 (see...). Figure 2The aqueous phase (second aqueous phase) is transported to the second mixer 14.

[0186] Second stage of oxime reaction:

[0187] Sulfuric acid (acid) is fed into the second mixer 14 to maintain the pH value at 2-3. The resulting mixture is then fed into the second oxime reactor 15. At the same time, raw material B (an organic solvent solution of cyclododecanone) is continuously fed into the second oxime reactor 15 at a rate of 33.4 kg / h. The reaction temperature is controlled at about 90°C, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the second reaction solution.

[0188] The second reaction liquid is sent to the second phase separator 16 for the second phase separation, the oil-water interface is controlled at 50%, the residence time is 20 minutes, and the resulting oil phase (second oil phase) is sent to the first oxime reactor 11 to repeat the steps of the first oxime reaction. The aqueous phase (second aqueous phase) enters the water treatment system.

[0189] (3) Rearrangement reaction

[0190] The oil phase (first oil phase), ethylcyclohexane, and concentrated sulfuric acid (second catalyst) output from the first phase separator 13 are fed into the rearrangement reactor 21 at rates of 34.5 kg / h, 34.5 kg / h, and 10.8 kg / h, respectively, for mixing and rearrangement reaction. The rearrangement reaction temperature is 130°C, the reaction pressure is 0.3 MPa, and the residence time is 10 min, resulting in a third reaction solution of 79.8 kg / h.

[0191] The third reaction solution is fed into the neutralization phase separator 22 at a rate of 79.8 kg / h. After ammonia water (alkali) is fed to maintain the pH value at 9-10, the third phase is separated to obtain the third aqueous phase and the third oil phase.

[0192] The third oil phase is transferred to the water washing tank 23, and water is added for washing. After the pH of the resulting mixture is about 7, the fourth phase is separated to obtain the fourth aqueous phase and the fourth oil phase. The third and fourth aqueous phases are then combined and enter the water treatment system.

[0193] The fourth oil phase is fed to the distillation system. First, it enters the desolventizing column with 5 theoretical plates, a distillation pressure of 15 kPa, and a temperature of 180°C. Then, the bottom product enters the product column with 12 theoretical plates, a distillation pressure of 800 Pa, and a temperature of 190°C, outputting dodelactam.

[0194] Example 2

[0195] This embodiment uses the same apparatus as Example 1 to prepare dodecalactam, and the preparation steps are basically the same. The difference lies in the continuous oxime reaction conditions in step (2), which are shown below:

[0196] First stage of oxime reaction:

[0197] Raw material A is continuously fed into the first oxime reactor 11 at a rate of 30.0 kg / h. Ammonia water is fed to maintain the pH value at about 7. The reaction temperature is controlled at about 90℃, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the first reaction solution.

[0198] The first reaction solution is delivered to the first mixer 12, and ammonia water is delivered to maintain the pH value at around 8.5;

[0199] The resulting mixture is sent to the first phase separator 13 for the first phase separation, with the oil-water interface controlled at 50% and the residence time at 20 minutes. The resulting oil phase is sent to the rearrangement reactor 21, and the water phase is sent to the second mixer 14 for later use.

[0200] Second stage of oxime reaction:

[0201] Sulfuric acid is fed into the second mixer 14 to maintain the pH value at 2-3. The resulting mixture is then fed into the second oxime reactor 15. At the same time, raw material B is continuously fed into the second oxime reactor 15 at a rate of 33.4 kg / h. The reaction temperature is controlled at about 90°C, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the second reaction solution.

[0202] The second reaction liquid is transported to the second phase separator 16 for the second phase separation, the oil-water interface is controlled at 50%, the residence time is 20 minutes, and the resulting oil phase is transported to the first oxime reactor 11 to repeat the steps of the first oxime reaction.

[0203] Example 3

[0204] This embodiment uses the same apparatus as Example 1 to prepare dodecalactam, and the preparation steps are basically the same. The difference lies in the continuous oxime reaction conditions in step (2), which are shown below:

[0205] First stage of oxime reaction:

[0206] Raw material A is continuously fed into the first oxime reactor 11 at a rate of 36.0 kg / h. Ammonia water is fed to maintain the pH value at about 7. The reaction temperature is controlled at about 90℃, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the first reaction solution.

[0207] The first reaction solution is delivered to the first mixer 12, and ammonia water is delivered to maintain the pH value at around 8.5;

[0208] The resulting mixture is sent to the first phase separator 13 for the first phase separation, with the oil-water interface controlled at 50% and the residence time at 20 minutes. The resulting oil phase is sent to the rearrangement reactor 21, and the water phase is sent to the second mixer 14 for later use.

[0209] Second stage of oxime reaction:

[0210] Sulfuric acid is fed into the second mixer 14 to maintain the pH value at 2-3. The resulting mixture is then fed into the second oxime reactor 15. At the same time, raw material B is continuously fed into the second oxime reactor 15 at a rate of 33.4 kg / h. The reaction temperature is controlled at about 90°C, the reaction residence time is 40 min, the reaction pressure is 0.2 MPa, and the stirring speed is 900 rpm to obtain the second reaction solution.

[0211] The second reaction liquid is transported to the second phase separator 16 for the second phase separation, the oil-water interface is controlled at 50%, the residence time is 20 minutes, and the resulting oil phase is transported to the first oxime reactor 11 to repeat the steps of the first oxime reaction.

[0212] Comparative Example 1

[0213] Dodecyl lactam was prepared in the same manner as in Example 1, except that the total molar ratio of hydroxylamine in the first-stage oxime reaction feed to cyclododecanone in the second-stage oxime reaction feed was adjusted to 1:0.5.

[0214] Comparative Example 2

[0215] Dodecyl lactam was prepared in the same manner as in Example 1, except that the total molar ratio of hydroxylamine in the first-stage oxime reaction feed to cyclododecanone in the second-stage oxime reaction feed was adjusted to 1:2.

[0216] Comparative Example 3

[0217] Dodecyl lactam was prepared in the same manner as in Example 1, except that the pH of the mixture in the first reactor was adjusted to 2, and the pH of the mixture in the second reactor was adjusted to 2.

[0218] Comparative Example 4

[0219] Dodecyl lactam was prepared in the same manner as in Example 1, except that the pH of the mixture in the first reactor was adjusted to 8, and the pH of the mixture in the second reactor was adjusted to 8.

[0220] Comparative Example 5

[0221] Dodecyl lactam was prepared in the same manner as in Example 1, except that the total molar ratio of hydroxylamine in the first-stage oxime reaction feed to cyclododecanone in the second-stage oxime reaction feed was adjusted to 1.3:1.

[0222] Comparative Example 6

[0223] Dodecyl lactam was prepared in the same manner as in Example 1, except that the total molar ratio of hydroxylamine in the first-stage oxime reaction feed to cyclododecanone in the second-stage oxime reaction feed was adjusted to 0.9:1.

[0224] After the continuous reaction proceeded smoothly in the above embodiments and comparative examples, the output liquids of the first oximeization stage, the second oximeization stage, and the distillation stage were tested, wherein:

[0225] Cyclododecanone conversion rate = (Cyclododecanone content / (Cyclododecanone content + Cyclododecanone oxime content + Imine content) × 100%;

[0226] Cyclododecanone oxime selectivity = cyclododecanone oxime content / (cyclododecanone oxime content + imine content) × 100%;

[0227] The contents of cyclododecanone, cyclododecanone oxime, imine, and the purity of the dodecyl lactam distillate were all determined by gas chromatography. Instrument model: Shimadzu GC2010; Column: DB-5 (30×0.32×0.25); Column temperature: programmed temperature rise (50℃ for 4 min, then increased to 100℃ at a rate of 5℃ / min, then increased to 300℃ at a rate of 25℃ / min and held for 5 min); Injector temperature: 230℃; FID temperature: 300℃; N2 flow rate: 1 mL / min; H2 flow rate: 40 mL / min; Septum purge (N2) flow rate: 3 mL / min; Carrier gas (N2) flow rate: 1 mL / min; Split injection, split ratio: 20; Injection volume: 0.5 μL.

[0228] Hydroxylamine residue: The mass percentage of hydroxylamine was determined according to the group standard T / CIESC 94-2025.

[0229] Solution transmittance: After dilution with anhydrous ethanol solvent, the ultraviolet transmittance was measured at a wavelength of 270 nm using a spectrophotometer under the specified optical path.

[0230] Table 1 Preparation results of the examples

[0231]

[0232] According to Table 1, the cyclododecanone conversion rate of Examples 1-3 is ≥99.90%, the cyclododecanone oxime selectivity is ≥99.90%, the hydroxylamine residue in the aqueous phase during the second oxime stage is ≤0.08%, the gas phase purity of the dodecylamine distillate is ≥99.94%, and the solution transmittance is ≥98%. This indicates that the preparation method of the present invention has the advantages of high conversion rate, high selectivity, low hydroxylamine residue, high product purity, and good color.

[0233] Table 2. Preparation results of the comparative examples

[0234]

[0235] According to Table 2, in Comparative Example 1, compared to Example 1, the total molar ratio of hydroxylamine to cyclododecanone was adjusted to 1:0.5 (hydroxylamine was in relative excess), resulting in a high residual amount of hydroxylamine in the aqueous phase of the second oxime stage (6.78%), and a decrease in the gas phase purity of dodecanoic acid to 98.23%, indicating that excess hydroxylamine would cause raw material waste and affect the purity of the final product; in Comparative Example 2, compared to Example 1, the total molar ratio was adjusted to 1:2 (cyclododecanone was in relative excess), resulting in a cyclododecanone conversion rate of only 49.04% in the aqueous phase of the second oxime stage and a gas phase purity of 98.15%, indicating that excess cyclododecanone would lead to incomplete reaction in the second stage, reducing yield and purity; in Comparative Example 3, compared to Example 1... In Example 1, adjusting the pH of the first reactor to 2 (which should be weakly alkaline 6-7.5) resulted in a decrease in the selectivity of cyclododecanone oxime in the oil phase to 88.82% during the first oxime stage, with a residual hydroxylamine content of 5.06% and a gas phase purity of 97.68%. This indicates that excessive acidity in the first stage inhibits hydroxylamine activity and significantly reduces selectivity. In Comparative Example 4, compared to Example 1, adjusting the pH of the second reactor to 8 (which should be acidic 1-4) resulted in a decrease in the conversion rate of cyclododecanone in the oil phase to 86.93% during the first oxime stage, with a selectivity of 95.67% and a gas phase purity of only 95.88%. This indicates that failure to provide an acidic environment in the second stage leads to hydroxylamine decomposition or incomplete reaction, severely impairing conversion rate and purity.

[0236] The technical features of the above-described embodiments and examples can be combined in any suitable manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0237] The embodiments described above merely illustrate several implementations of the present invention and should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Furthermore, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention, and the equivalent forms obtained also fall within the protection scope of the present invention. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing cyclododecanone oxime, characterized in that, It includes a cyclical first oxime phase and a second oxime phase; The first oxime phase includes the following steps: After adjusting the mixture in the first oxime reactor to meet the first condition, the first oxime reaction is carried out to obtain the first reaction solution; The first condition includes conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; and (iii) the pH is 6-7.

5. After the first reaction solution is subjected to a first phase separation, the oil phase and the aqueous phase are collected; cyclododecanone oxime is obtained from the oil phase; The second oxime phase includes the following steps: The aqueous phase collected in the first oxime stage is transported to the second oxime reactor, and after the mixture in the second oxime reactor is adjusted to meet the second conditions, the second oxime reaction is carried out to obtain the second reaction solution. The second condition includes conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone to hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4; After the second reaction solution undergoes a second phase separation, the oil phase is collected. The oil phase collected in the second oxime stage is transported to the first oxime reactor, and the steps of the first oxime stage are repeated. The mixture in the first oxime reactor and the second oxime reactor is controlled to meet the following condition: the molar ratio of cyclododecanone to hydroxylamine is 1:(1-1.2).

2. The preparation method according to claim 1, characterized in that, The mixtures in the first oxime reactor and the second oxime reactor each independently also include a first catalyst; The first catalyst is used to catalyze the oxime reaction of hydroxylamine and cyclododecanone; and / or, The first catalyst comprises one or more of dodecanoic acid, methylbenzenesulfonic acid, and aminododecanoic acid.

3. The preparation method according to claim 2, characterized in that, In the mixture in the first oxime reactor, the mass ratio of the first catalyst to cyclododecanone is (0.1-2):100; and / or, In the mixture in the second oxime reactor, the mass ratio of the first catalyst to hydroxylamine is (0.1-2):

100.

4. The preparation method according to any one of claims 1-3, characterized in that, Before performing the first phase separation on the first reaction solution, adjust the pH of the first reaction solution to 8-10; and / or, Before the aqueous phase collected in the first oxime stage is transported to the second oxime reactor, the pH of the aqueous phase is adjusted to 1-4.

5. The preparation method according to any one of claims 1-3, characterized in that, One or more of the following conditions must be met: (1) In the mixture in the first oxime reactor, the volume ratio of water to organic solvent is 1:(0.5-1.5); (2) In the mixture in the second oxime reactor, the volume ratio of water to organic solvent is 1:(0.5-1.5); (3) The organic solvent in the mixture in the first oxime reactor includes saturated cycloalkanes; (4) The organic solvent in the mixture in the second oxime reactor includes saturated cycloalkanes; (5) The molar ratio of the hydroxylamine delivered to the first oxime reactor and the cyclododecanone delivered to the second oxime reactor is 1:(1-1.2); (6) The first oxime reaction was carried out under stirring; the stirring speed was 900 rpm-1000 rpm; (7) The conditions for the first oxime reaction include: the reaction temperature is 80℃-100℃, the reaction pressure is 0.1MPa-0.5MPa, and the reaction time is 0.5h-2h; (8) The second oxime reaction is carried out under stirring; the stirring speed is 900 rpm-1000 rpm; (9) The conditions for the second oxime reaction include: the reaction temperature is 80℃-100℃, the reaction pressure is 0.1MPa-0.5MPa, and the reaction time is 0.5h-2h.

6. An apparatus for preparing cyclododecanone oxime, characterized in that, The first oxime reactor, the first phase separator, the second oxime reactor, and the second phase separator are connected in sequence by a conveying pipe; The first oxime reactor has an input end and an output end; The first phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal; The second oxime reactor has an input end and an output end; The second phase splitter has an input terminal, a water phase output terminal, and an oil phase output terminal; The output end of the first oxime reactor and the input end of the first phase separator, the aqueous phase output end of the first phase separator and the input end of the second oxime reactor, the output end of the second oxime reactor and the input end of the second phase separator, and the oil phase output end of the second phase separator and the input end of the first oxime reactor are respectively connected by the conveying pipe; The first oxime reactor is used to adjust the mixture in the first oxime reactor to meet the first conditions, and then carry out the first oxime reaction to obtain the first reaction solution; the first conditions include conditions (i) to (iii): (i) the molar ratio of hydroxylamine to cyclododecanone is (1-10):1; (ii) the solvent is a mixture of water and organic solvent; (iii) the pH is 6-7.5; The first phase separator is used to separate the first reaction liquid into two phases and output the oil phase and the water phase respectively; The second oxime reactor is used to transport the aqueous phase collected in the first oxime stage to the second oxime reactor, and after adjusting the mixture in the second oxime reactor to meet the second conditions, carry out the second oxime reaction to obtain the second reaction solution; the second conditions include conditions (iv) to (vi): (iv) the molar ratio of cyclododecanone and hydroxylamine is (1-10):1; (v) the solvent is a mixture of water and organic solvent; (vi) the pH is 1-4; The second phase separator is used to separate the second reaction liquid into two phases, and output the oil phase and the water phase respectively.

7. The preparation apparatus according to claim 6, characterized in that, A first mixer is also provided between the first oxime reactor and the first phase separator; The first mixer is used to mix the reaction solution output from the first oxime reactor with alkali and adjust the pH of the resulting mixture to 8-10.

8. The preparation apparatus according to claim 6 or 7, characterized in that, A second mixer is also provided between the second phase separator and the second oxime reactor; The second mixer is used to mix the aqueous phase output from the second phase separator with acid, and adjust the pH of the resulting mixture to 1-4.

9. A method for preparing dodecanolactam, characterized in that, Cyclododecanoic acid oxime is prepared using the preparation method according to any one of claims 1-5 or the preparation apparatus according to any one of claims 6-8; The dodecanolide was subjected to a Beckmann rearrangement reaction to obtain the dodecanolactam.

10. The preparation method according to claim 9, characterized in that, The Beckmann rearrangement reaction is carried out in the presence of a second catalyst; The second catalyst comprises one or more of sulfuric acid, polyphosphoric acid, phosphorus pentachloride, phosphorus trichloride, benzenesulfonyl chloride, and thionyl chloride; and / or, The conditions for the Beckmann rearrangement reaction include: a reaction temperature of 60℃-150℃, a reaction pressure of 0.2MPa-1MPa, and a reaction time of 0.5min-30min.

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