Method for recovering and reusing selective homogeneous hydrogenation catalysts

Abstract

The present invention relates to a method for recovering and reusing a selective homogeneous hydrogenation catalyst, which comprises synthesizing cyclododecene by selectively hydrogenating a first reaction solution containing cyclododecatriene, triphenylphosphine, formaldehyde, and ruthenium chloride, and then recovering the selective homogeneous hydrogenation catalyst from a second reaction solution after the synthesis of cyclododecene is completed, the method comprising the steps of producing a selective homogeneous hydrogenation catalyst from the triphenylphosphine, formaldehyde, and ruthenium chloride during the selective hydrogenation of the first reaction solution, synthesizing cyclododecene, mixing a solvent containing cyclododecanone with the first reaction solution, and distilling and separating the second reaction solution after the synthesis of cyclododecene to recover the selective homogeneous hydrogenation catalyst.

Description

[Technical field]

[0001] The present invention relates to a method for recovering and reusing a selective homogeneous hydrogenation catalyst. [Background technology]

[0002] The synthesis of cyclododecene (CDEN) by selective hydrogenation of cyclododecatriene (CDT) has been frequently described in the literature, and various studies have been carried out to improve the yield of cyclododecene.

[0003] For the selective hydrogenation reaction, a metal-ligand catalyst known as Wilkinson catalyst has been used, that is, a catalyst in which a metal such as rubidium (Ru), rhodium (Rh), cobalt (Co), or nickel (Ni) is combined with a ligand such as triphenylphosphine (TPP) or CO and a halogen element.

[0004] Generally, catalysts are substances that do not react themselves in a reaction system but activate the overall reaction so that it proceeds quickly, and are essential to the chemical industry. Generally, catalysts are present in small amounts in a reaction system to perform their role, but as the chemical industry develops, their usage has increased, and the amount of waste catalysts generated has also increased sharply. With no natural resources at all, South Korea is completely dependent on imports for all of its precious metal-related industrial raw materials, and so there is an urgent need to recover precious metals from waste catalysts and recycle them as industrial raw materials.

[0005] Methods for recovering the catalyst after the selective hydrogenation reaction are disclosed depending on the state and condition of the catalyst.

[0006] As an example, US4413118 discloses a technology for separating a catalyst in which triphenylphosphine and a halogen element are bound to a group 8 metal by a ligand by interacting with a substance containing a C=S bond. However, the interaction process takes a long time, and the process has the disadvantage of needing to be cooled to around 0°C.

[0007] US3715405 discloses that when the [Co(CO)3P(n-C4H9)3]2 catalyst is used in a selective hydrogenation reaction to produce cyclododecene from cyclododecatriene, the catalyst can be recovered by phase separation without a separate separation technique after the reaction. However, the process efficiency is poor because a large amount of catalyst is required and a highly accurate and complicated separation process is required to completely remove the solvent after phase separation. In order to solve the problems of the prior art, Korean Patent Publication No. 10-2020-0076301, which the applicant has already applied for, confirms that the product and catalyst can be separated through a distillation device and the recovered catalyst can be reused. However, the volume ratio of the catalyst is low, making it difficult to maintain the operation of the distillation separation device, and the product cyclododecene (CDEN) remains, and as it is reused, the production ratio of the by-product cyclododecane (CDAN) increases. In addition, there is an inconvenience that a temperature of 80°C or higher must be maintained to maintain high fluidity.

[0008] Therefore, the present inventors have conducted extensive research into efficient methods for recovering and reusing the selective hydrogenation catalyst, and as a result have found that, when an appropriate solvent is used, the selective hydrogenation catalyst can be separated and recovered in a simple manner, the design and operation and maintenance of the distillation separation apparatus is simple, and even when a solvent is added, both the conversion rate of cyclododecatriene and the selectivity of cyclododecene can be maintained at high levels, thereby completing the present invention. Summary of the Invention [Problem to be solved by the invention]

[0009] In order to solve the above problems, the present invention aims to provide a method for recovering and reusing a selective homogeneous hydrogenation catalyst, which can separate and recover the selective homogeneous hydrogenation catalyst in a short process time and in a relatively simple manner, and which is easy to design and operate and maintain a distillation separation apparatus, and which can maintain both the conversion of cyclododecatriene and the selectivity of cyclododecene at a high level. [Means for solving the problem]

[0010] The method for recovering a selective homogeneous hydrogenation catalyst of the present invention is a method for synthesizing cyclododecene by selectively hydrogenating a first reaction solution containing cyclododecatriene, triphenylphosphine, formaldehyde and ruthenium chloride, and then recovering a selective homogeneous hydrogenation catalyst from a second reaction solution after synthesis of the cyclododecene is completed, the method including the steps of: producing a selective homogeneous hydrogenation catalyst from the triphenylphosphine, formaldehyde and ruthenium chloride during the selective hydrogenation reaction of the first reaction solution, synthesizing cyclododecene, mixing a solvent containing cyclododecanone with the first reaction solution, and distilling and separating the second reaction solution after synthesis of cyclododecene to recover the selective homogeneous hydrogenation catalyst.

[0011] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the solvent may be cyclododecanone dissolved in cyclododecatriene.

[0012] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the distillation separation is performed by a distillation column, and the distillation column includes an upper column from which a product containing cyclododecene is discharged and a lower column from which the selective homogeneous hydrogenation catalyst and a solvent are separated. During the distillation separation, the pressure of the upper column may be 0.1 bar or less and the temperature may be 100°C to 200°C, and the pressure of the lower column may be 0.1 bar or less and the temperature may be 150°C to 250°C.

[0013] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the molar ratio of ruthenium chloride:triphenylphosphine:formaldehyde may be 1:100-300:150-500.

[0014] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the selective hydrogenation reaction may be carried out in a stirred tank reactor equipped with a gas-induced hollow-type agitator.

[0015] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, hydrogen gas present in a gas phase at the top of the stirred tank reactor can be supplied to the reaction solution through the hollow of the gas-inducing hollow-type agitator.

[0016] In the method for recovering a homogeneous hydrogenation catalyst according to an embodiment of the present invention, the first reaction solution may further include a catalyst activator including acetic acid.

[0017] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the catalyst activator may be added in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of cyclododecatriene.

[0018] In the method for recovering a homogeneous hydrogenation catalyst according to one embodiment of the present invention, the selective hydrogenation reaction may be carried out under conditions of a temperature of 100 to 200° C. and a pressure of 10 to 80 bar.

[0019] The method for reusing the recovered selective homogeneous hydrogenation catalyst of the present invention includes the steps of re-introducing the selective homogeneous hydrogenation catalyst recovered by the above-mentioned method into a third reaction solution containing cyclododecatriene, and subjecting it to a second selective hydrogenation reaction to synthesize cyclododecene. Effect of the Invention

[0020] The method for recovering and reusing the selective homogeneous hydrogenation catalyst according to the present invention can separate unreacted cyclododecatriene and cyclododecadiene, the product cyclododecene, the selective homogeneous hydrogenation catalyst, and excess triphenylphosphine simply by adding a solvent containing cyclododecanone (CDON) to the reactants and then separating the solvent by evaporation. The separated and recovered selective homogeneous hydrogenation catalyst and excess triphenylphosphine can be used directly in the next selective hydrogenation reaction without any additional post-treatment.

[0021] In addition, by using a solvent containing cyclododecanone (CDON), an intermediate product in the laurolactam manufacturing process, the quality of the product is not affected even if cyclododecanone is present in the product. This eliminates the need for highly precise and complicated processes to completely separate the product from the solvent, and the catalyst containing cyclododecanone, the solvent, can be immediately added to the process, allowing for efficient recovery and reuse of the catalyst.

[0022] Furthermore, when the recovered selective homogeneous hydrogenation catalyst is reused, there is an advantage that both the conversion of cyclododecatriene and the selectivity of cyclododecene can be maintained at a high level.

[0023] Even if an effect is not explicitly mentioned in the present invention, the effects described in the specification and their inherent effects expected from the technical features of the present invention are treated as being the same as those described in the specification of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the method for recovering and reusing the selective homogeneous hydrogenation catalyst according to the present invention will be described in detail. Unless otherwise defined, the technical and scientific terms used herein have the meanings that are commonly understood by those having ordinary knowledge in the technical field to which the present invention belongs, and the description of known functions and configurations that may make the gist of the present invention unclear from the following description will be omitted.

[0025] In addition, in this specification, terms such as 1st, 2nd, A, B, (a), (b), etc. may be used to describe components according to the present invention. Such terms are used to distinguish the components from other components, and do not limit the essence, order, or sequence of the components.

[0026] Additionally, as used herein, the singular forms of the terms "a," "an," and "the" may be construed as including the plural forms as well, unless otherwise indicated.

[0027] In this specification, the unit of % used without special reference means % by weight unless otherwise defined.

[0028] Since rare, low-yield, and expensive precious metals are used as catalysts in the selective hydrogenation reaction to produce cyclododecene from cyclododecatriene, Korea, which relies entirely on imports for precious metal-related industrial raw materials, is in an urgent situation to recover precious metals from waste catalysts and reuse them as industrial raw materials. In order to solve such problems in the prior art, Korean Patent Publication No. 10-2020-0076301, which the applicant has already filed, confirms that it is possible to separate the product and catalyst through a distillation device and reuse the recovered catalyst, but the volume ratio of the catalyst is low, making it difficult to maintain the operation of the distillation separation device, and the product cyclododecene (CDEN) remains and is reused, resulting in a high production ratio of the by-product cyclododecane (CDAN). In addition, there is an inconvenience that a temperature of 80°C or higher must be maintained continuously to maintain high fluidity.

[0029] Therefore, the present inventors further use an appropriate solvent for the catalyst, so that the selective homogeneous hydrogenation catalyst can be easily separated and recovered, and the design and operation maintenance of a distillation separation apparatus can be made easy. Furthermore, the present inventors provide a method for recovering and reusing a selective homogeneous hydrogenation catalyst, which can maintain both the conversion rate of cyclododecatriene and the selectivity of cyclododecene at high levels when the recovered selective homogeneous hydrogenation catalyst is reused.

[0030] In detail, the method for recovering a selective homogeneous hydrogenation catalyst according to the present invention is a method for synthesizing cyclododecene (CDEN) by selectively hydrogenating a first reaction solution containing cyclododecatriene (CDT), triphenylphosphine (TPP), formaldehyde and ruthenium chloride (RhCl3), and then recovering a selective homogeneous hydrogenation catalyst from a second reaction solution after the synthesis of cyclododecene is completed, the method comprising the steps of: producing a selective homogeneous hydrogenation catalyst from triphenylphosphine, formaldehyde and ruthenium chloride during the selective hydrogenation reaction of the first reaction solution, synthesizing cyclododecene, mixing a solvent containing cyclododecanone (CDON) with the first reaction solution, and distilling and separating the second reaction solution after the synthesis of cyclododecene to recover the selective homogeneous hydrogenation catalyst.

[0031] In this way, unreacted cyclododecatriene and cyclododecadiene, and the product cyclododecene, the selective homogeneous hydrogenation catalyst, and excess triphenylphosphine can be separated simply by the method of distillation (evaporation) separation, and the separated and recovered selective homogeneous hydrogenation catalyst and excess triphenylphosphine can be used as they are in the next selective hydrogenation reaction without any additional post-treatment.

[0032] In addition, by using a solvent containing cyclododecanone (CDON), an intermediate product in the laurolactam manufacturing process, as a catalyst, even if cyclododecanone is contained in the product, it does not affect the quality of the product. Therefore, there is no need to perform a highly precise and complicated process to completely separate the product from the solvent, and the catalyst containing cyclododecanone, which is the solvent, can be immediately added to the process, making it possible to efficiently recover and reuse the catalyst.

[0033] In addition, when using a recovered selective homogeneous hydrogenation catalyst, the induction period can be shortened and productivity can be further increased, compared to when a selective hydrogenation reaction is carried out by first using a catalyst containing triphenylphosphine, formaldehyde and ruthenium chloride and forming a selective homogeneous hydrogenation catalyst during the reaction.

[0034] In addition, when the recovered selective homogeneous hydrogenation catalyst is reused, it is advantageous in that both the conversion of cyclododecatriene and the selectivity of cyclododecene can be maintained at high levels.

[0035] The method for recovering a selective homogeneous hydrogenation catalyst according to the present invention will be described in detail below.

[0036] First, a step of synthesizing cyclododecene by selectively hydrogenating a first reaction solution containing cyclododecatriene, triphenylphosphine, formaldehyde and ruthenium chloride, during which a selective homogeneous hydrogenation catalyst is produced from the triphenylphosphine, formaldehyde and ruthenium chloride to synthesize cyclododecene, can be carried out. Here, it goes without saying that hydrogen gas (H2) is introduced in a conventional manner for the selective hydrogenation reaction.

[0037] This step is for synthesizing cyclododecene, and cyclododecene can be synthesized by the method described below or a conventionally known method.

[0038] In particular, in the step of synthesizing cyclododecene, the selective hydrogenation reaction can be carried out in a stirred tank reactor equipped with a gas-induced hollow stirrer. In this way, when the reaction is carried out using a gas-induced hollow stirrer, reactivity can be ensured even without an organic solvent that is usually used to enhance reactivity, and the reaction time can be significantly reduced.

[0039] More specifically, in the step of synthesizing cyclododecene, the gas-inducing hollow stirrer rotates and stirs to carry out the reaction, and hydrogen gas present in the gas phase at the top of the stirred tank reactor is supplied to the reaction solution through the hollow of the gas-inducing hollow stirrer, thereby supplying hydrogen to cyclododecatriene. The gas-inducing hollow stirrer has a hollow passage formed therein, and hydrogen gas flows in through the hollow passage and contacts cyclododecatriene to carry out a selective hydrogenation reaction.

[0040] Alternatively, cyclododecene can be synthesized by a conventionally known method.

[0041] Meanwhile, during the selective hydrogenation reaction, a selective homogeneous hydrogenation catalyst is prepared from the triphenylphosphine, formaldehyde and ruthenium chloride to synthesize cyclododecene, and the selective homogeneous hydrogenation catalyst, homogeneous composite catalyst, can be RuH(PPh3)3(CO)Cl or Ru(PPh3)2(CO)2Cl2, or both.

[0042] Specifically, the triphenylphosphine and formaldehyde form a complex with the ruthenium chloride, and act as a catalyst for the selective hydrogenation reaction.

[0043] As a preferred example, the molar ratio of the ruthenium chloride: triphenylphosphine: formaldehyde can be 1:100-300:150-500, more preferably, the molar ratio of the ruthenium chloride: triphenylphosphine: formaldehyde can be 1:130-250:200-400, and even more preferably, the molar ratio of the ruthenium chloride: triphenylphosphine: formaldehyde can be 1:170-230:250-350. In the above range, the conversion rate and selectivity can be significantly improved. However, this is a preferred example, and it goes without saying that the present invention is not limited thereto.

[0044] In addition, in one embodiment of the present invention, the first reaction solution may further include a catalyst activator including acetic acid. When acetic acid is added, the reaction of the ruthenium chloride-triphenylphosphine complex compound catalyst can be further activated, and the conversion rate and selectivity can be further improved. As a preferred example, acetic acid may be added in an amount of 0.01 to 2 parts by weight per 100 parts by weight of cyclododecatriene, more preferably 0.05 to 1.5 parts by weight per 100 parts by weight of cyclododecatriene, and even more preferably 0.1 to 1 part by weight per 100 parts by weight of cyclododecatriene. However, this is a preferred example, and it goes without saying that the present invention is not limited thereto.

[0045] In one embodiment of the present invention, the amount of the catalyst containing triphenylphosphine, formaldehyde and ruthenium chloride used may be sufficient to allow the reaction of the reactants to proceed sufficiently, and preferably, the catalyst containing triphenylphosphine, formaldehyde and ruthenium chloride may be added in an amount of 1 to 20 parts by weight relative to 100 parts by weight of cyclododecatriene, more preferably, the catalyst containing triphenylphosphine, formaldehyde and ruthenium chloride may be added in an amount of 1 to 10, and even more preferably, 1 to 7 parts by weight. However, this is a preferred example for improving the conversion rate and selectivity, and it goes without saying that the present invention is not limited thereto.

[0046] In one example of the present invention, the selective hydrogenation reaction can be carried out under conditions of a temperature of 100 to 200°C and a pressure of 10 to 80 bar, more preferably under conditions of a temperature of 140 to 180°C and a pressure of 20 to 60 bar, and further preferably under conditions of a temperature of 150 to 175°C and a pressure of 20 to 40 bar. However, this is a preferred example for improving the conversion rate and selectivity, and it goes without saying that the present invention is not limited thereto.

[0047] Next, a step of mixing a solvent containing cyclododecanone (CDON) with the first reaction solution can be performed. Here, the solvent can be added after the selective homogeneous hydrogenation catalyst is formed by the triphenylphosphine, formaldehyde, and ruthenium chloride of the first reaction solution, but can also be added before the catalyst is formed.

[0048] In one embodiment of the present invention, the solvent may be cyclododecanone itself or may further contain cyclododecatriene. Preferably, cyclododecanone dissolved in cyclododecatriene may be used. Here, the amount of cyclododecanone in the solvent is not limited as long as it can be dissolved in cyclododecatriene. As such a solvent is used, a solvent in which cyclododecanone (CDON), an intermediate product in the manufacturing process of laurolactam, is dissolved, so that even if cyclododecanone is contained in the product, it does not affect the quality of the product, and there is no need to perform a highly accurate and complicated process to completely separate the product and the solvent, and since the catalyst containing cyclododecanone, which is the solvent, can be immediately added to the process, efficient recovery and reuse of the catalyst is possible. In addition, cyclodecatriene in which cyclododecanone is dissolved is a substance that participates in the present reaction, does not affect the catalytic activity, and there is no problem in reusing it even if it remains in the recovered catalyst.

[0049] Next, the first reaction solution is subjected to a selective hydrogenation reaction, and the second reaction solution in which the synthesis of cyclododecene has been completed is separated by distillation to separate unreacted cyclododecatriene and cyclododecadiene and the product cyclododecene, and the selective homogeneous hydrogenation catalyst and the solvent can be recovered.

[0050] As described above, unreacted cyclododecatriene and cyclododecadiene, the product cyclododecene, the selective homogeneous hydrogenation catalyst, and excess triphenylphosphine can be separated simply by the method of adding a solvent containing cyclododecanone and then separating by distillation (evaporation), and the separated and recovered selective homogeneous hydrogenation catalyst and excess triphenylphosphine can be used as they are in the next selective hydrogenation reaction without any additional post-treatment.

[0051] Furthermore, since the solvent containing cyclododecanone of the present invention has good fluidity at the melting point of cyclododecanone, which is a relatively low temperature, the temperature of the process line can be maintained lower than when distillation separation is performed without adding a solvent, which enables energy saving and more efficient recovery of the catalyst.

[0052] In one embodiment of the present invention, the distillation separation may be carried out through a distillation column, in which the distillation column is divided into an upper column from which a product containing cyclodecene is discharged and a lower column from which a selective homogeneous hydrogenation catalyst and a solvent are separated. The distillation separation may be carried out under the conditions of a pressure of 0.3 bar or less and a temperature of 100 to 200°C in the upper column, more preferably, a temperature of 130 to 170°C and a pressure of 0.1 bar or less, but is not limited thereto. The pressure of the lower column may be 0.3 bar or less and a temperature of 150 to 250°C, more preferably, a pressure of 0.1 bar or less and a temperature of 180 to 230°C. Furthermore, the reflux ratio in the distillation column may be 0.5 to 5, specifically, 1 to 2, and the boilup ratio may be 1 to 8, specifically, 4 to 5, but is not limited thereto. However, within the above range, unreacted cyclododecatriene and cyclododecadiene, and the product cyclododecene can be effectively separated by distillation.

[0053] In one embodiment of the present invention, the selective homogeneous hydrogenation catalyst may be recovered under conditions of a temperature of 10 to 30° C. and a pressure of 0.1 bar or less or a nitrogen atmosphere. That is, the temperature increased by the distillation separation process is cooled to room temperature to recover the selective homogeneous hydrogenation catalyst.

[0054] The present invention also relates to a method for reusing the recovered selective homogeneous hydrogenation catalyst, comprising the steps of: reintroducing the recovered selective homogeneous hydrogenation catalyst into a third reaction solution containing cyclododecatriene, and subjecting the catalyst to a second selective hydrogenation reaction to synthesize cyclododecene.

[0055] Here, the method for recovering the selective homogeneous hydrogenation catalyst is the same as the method for recovering the selective homogeneous hydrogenation catalyst described above, so a duplicated description will be omitted.

[0056] Then, when the distillation separation and recovery of the selective homogeneous hydrogenation catalyst are completed, the recovered selective homogeneous hydrogenation catalyst is re-introduced into the third reaction solution containing cyclododecatriene, and a second selective hydrogenation reaction is carried out to synthesize cyclododecene.

[0057] Here, the secondary selective hydrogenation reaction for synthesizing cyclododecene can be carried out by a conventionally known method.

[0058] As a specific example, the third reaction solution may further contain a solvent containing ethanol in addition to cyclododecatriene. Since the ethanol has a high dielectric constant, it can further activate the reaction of the reactants in the selective hydrogenation reaction, thereby improving the conversion rate and selectivity. The amount of ethanol used may be such that hydrogen can be selectively hydrogenated to cyclododecatriene, and preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight may be added relative to 100 parts by weight of cyclododecatriene. However, this is a preferred example, and it goes without saying that the present invention is not limited thereto.

[0059] In one example of the present invention, the secondary selective hydrogenation reaction may be carried out under conditions of a temperature of 120 to 200°C and a pressure of 10 to 80 bar, more preferably under conditions of a temperature of 140 to 180°C and a pressure of 20 to 60 bar, and further preferably under conditions of a temperature of 150 to 175°C and a pressure of 20 to 40 bar. However, this is a preferred example for improving the conversion rate and selectivity, and it goes without saying that the present invention is not limited thereto.

[0060] The method for recovering and reusing the selective homogeneous hydrogenation catalyst according to the present invention will be described in more detail with reference to the following examples. However, the following examples are merely a reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be realized in various forms.

[0061] In addition, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The terms used in the description in this application are merely for the purpose of effectively describing specific embodiments and are not intended to limit the present invention. In addition, the unit of additives not specifically described in the specification may be % by weight.

[0062] Example 1 Cyclododecatriene (CDT): ruthenium chloride (RuCl3): triphenylphosphine (TPP): formaldehyde was added in a molar ratio of 7500: 1: 110: 220, and 80 parts by weight of cyclododecanone (CDON) was added to 100 parts by weight of cyclododecatriene (CDT). Here, the mixture was heated at 70°C under nitrogen conditions to dissolve cyclododecanone (CDON). Next, the reaction solution was heated to 140°C while stirring at 1600 rpm under 6 bar of hydrogen. Next, a selective hydrogenation reaction was carried out at a temperature of 180°C under conditions of maintaining a hydrogen pressure of 20 bar, where the reaction was carried out in a stirred tank reactor equipped with a gas-induced hollow stirrer.

[0063] After the selective hydrogenation reaction, the second reaction solution was cooled to 30° C. or less under nitrogen conditions, and then the second reaction solution was recovered.

[0064] The second reaction solution was then charged into a distillation column for distillation, where the internal pressure of the upper column was -0.9 bar and the temperature was 155.9°C, and the internal pressure of the lower column was -0.85 bar and the temperature was 203.5°C. Upon completion of the distillation, the solution was cooled to below 30°C under a nitrogen atmosphere to recover the selective homogeneous hydrogenation catalyst.

[0065] The recovered catalyst was then re-added to the reaction solution to carry out the selective hydrogenation reaction again, and then re-recovered, where cyclododecatriene (CDT):recovered selective homogeneous hydrogenation catalyst was added in a molar ratio of 7500:1.

[0066] Example 2 In the selective homogeneous hydrogenation catalyst recovery method of Example 1, the selective hydrogenation reaction was carried out at a temperature of 170°C instead of 180°C, and the selective homogeneous hydrogenation catalyst was recovered and reused in the same manner as in Example 1.

[0067] Comparative Example 1 In the selective homogeneous hydrogenation catalyst recovery method of Example 1, except that cyclododecatriene (CDT) was further added in the amount of cyclododecanone (CDON) added in Example 1 instead of cyclododecanone (CDON), the selective homogeneous hydrogenation catalyst was recovered and reused in the recovery method of Example 1.

[0068] [Experimental Example 1] <Evaluation of conversion rate and selectivity> The reaction time, conversion rate, and selectivity yield of Example 1, Example 2, and Comparative Example were calculated and are shown in Table 1 below.

[0069] The conversion was calculated by the following formula 1, the selectivity by the following formula 2, and the yield by the following formula 3.

[0070] [Formula 1] Conversion rate (%) = (CDT0-CDT1-CDDN1) / CDT0 x 100

[0071] In the formula 1, CDT0 is the moles of cyclododecatriene introduced, CDT1 is the moles of cyclododecatriene after the reaction, and CDDN1 is the moles of cyclododecatriene. Here, cyclododecadiene (CDDN) is a product of incomplete hydrogenation in which only one of the three double bonds of cyclododecatriene is hydrogenated and two double bonds remain.

[0072] [Formula 2] Selectivity (%) = CDEN1 / (CDEN1+CDAN1) x 100

[0073] In the above calculation formula 2, CDEN1 is the number of moles of cyclododecene produced, and CDAN1 is the number of moles of cyclododecane, which is a by-product, produced.

[0074] [Formula 3] Yield (%) = Conversion rate x Selectivity

[0075] [Table 1]

[0076] As a result, as shown in Table 1, it was confirmed that the present invention can maintain both the conversion rate of cyclododecatriene and the selectivity of cyclododecene at a high level, as in the comparative example, and that the catalyst can be recovered at a high yield. Furthermore, the present invention prevents the difficulty in maintaining the operation of the distillation separation apparatus due to the low volume ratio of the catalyst caused by the addition of a solvent, and is advantageous for continuous production since the operation of the distillation separation apparatus is easy to maintain. In addition, there is no risk of the product cyclododecene (CDEN) remaining and being reused. Furthermore, in order to maintain high fluidity, it is only necessary to maintain a temperature of about 60°C or higher, and therefore has the advantage that the process maintenance is very advantageous compared to the comparative example.

[0077] The present invention has been described above using specific details and limited examples, but these are provided to facilitate a more general understanding of the present invention. The present invention is not limited to the above examples, and various modifications and variations can be made from such descriptions by those having ordinary knowledge in the field to which the present invention pertains.

[0078] Therefore, the concept of the present invention should not be limited to the above-described embodiments, and it can be said that not only the scope of the claims described below, but also all modifications that are equivalent or equivalent to the scope of the claims fall within the scope of the concept of the present invention.

Claims

1. A method for synthesizing cyclododecene by selectively hydrogenating a first reaction solution containing cyclododecatriene, triphenylphosphine, formaldehyde and ruthenium chloride, and recovering a selective homogeneous hydrogenation catalyst from a second reaction solution in which synthesis of cyclododecene has been completed, comprising: During the selective hydrogenation reaction of the first reaction solution, a selective homogeneous hydrogenation catalyst is produced from the triphenylphosphine, formaldehyde and ruthenium chloride, and cyclododecene is synthesized; mixing the first reaction solution with a solvent containing cyclododecanone; and recovering the selective homogeneous hydrogenation catalyst by distilling and separating the second reaction solution after completion of the synthesis of cyclododecene.

2. 2. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 1, wherein the solvent is cyclododecanone dissolved in cyclododecatriene.

3. The distillative separation is carried out by a distillation column; The distillation column comprises an upper column in which a product containing cyclododecene is discharged, and a lower column in which the selective homogeneous hydrogenation catalyst and the solvent are separated, 2. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 1, wherein during the distillation separation, the pressure of the upper column is 0.1 bar or less and the temperature is 100° C. to 200° C., and the pressure of the lower column is 0.1 bar or less and the temperature is 150° C. to 250° C.

4. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 1, wherein the molar ratio of ruthenium chloride:triphenylphosphine:formaldehyde is 1:100-300:150-500.

5. 2. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 1, wherein the selective hydrogenation reaction is carried out in a stirred tank reactor equipped with a gas-induced hollow-type agitator.

6. 6. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 5, wherein hydrogen gas present in gas phase at the top of the stirred tank reactor is supplied to the reaction solution through the hollow of the gas-inducing hollow stirrer.

7. The method for recovering a selective homogeneous hydrogenation catalyst according to claim 1, wherein the selective hydrogenation reaction is carried out under conditions of a temperature of 100 to 200° C. and a pressure of 10 to 80 bar.

8. A method for reusing the selective homogeneous hydrogenation catalyst recovered by the method according to any one of claims 1 to 7, comprising the steps of: reintroducing the selective homogeneous hydrogenation catalyst recovered by the method according to any one of claims 1 to 7 into a third reaction solution containing cyclododecatriene, and subjecting the catalyst to a second selective hydrogenation reaction to synthesize cyclododecene.

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