Preparation method of 4,4'-diaminodicyclohexylmethane with controllable anti / anti stereoisomer ratio

Abstract

This invention relates to a method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratios. The method involves sequentially passing a mixture of 4,4'-diaminodiphenylmethane and a solvent through a first reactor and a second reactor connected in series for catalytic hydrogenation to generate 4,4'-diaminodicyclohexylmethane. The first and second reactors are respectively packed with phosphorus-modified platinum group supported C3N4 catalysts. In the first reactor, reaction parameters are adjusted according to a first characteristic formula to control the mass fraction of cis-diaminomonocyclohexylmonophenylmethane in the product. In the second reactor, reaction parameters are adjusted according to a second characteristic formula to control the mass fraction of trans / trans stereoisomers in the product. This invention allows for the immediate and flexible preparation of 4,4'-diaminodicyclohexylmethane with the target trans / trans stereoisomer content.

Description

Technical Field

[0001] This invention relates to the technical field of alicyclic amine compound production, and in particular to a method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio. Background Technology

[0002] 4,4'-Diaminodicyclohexylmethane (H12MDA) is an important alicyclic amine organic intermediate, existing in three stereoisomers with different thermodynamic properties: trans-trans, cis-trans, and cis-cis. Among these, the trans / trans stereoisomer exhibits the highest thermodynamic stability. At equilibrium, the mass fraction distribution of the three is as follows: trans / trans stereoisomer 4,4'-diaminodicyclohexylmethane (t,t-H12MDA) accounts for 50%, cis / trans stereoisomer 4,4'-diaminodicyclohexylmethane (t,c-H12MDA) accounts for 43%, and cis / cis stereoisomer 4,4'-diaminodicyclohexylmethane (c,c-H12MDA) accounts for 7%. However, in practical applications, H12MDA products with lower t,t-H12MDA content are more widely used. For example, products with a t,t-H12MDA mass fraction below 24% (PACM20) can be used to prepare high-performance, anti-aging polyurethane dicyclohexylmethane diisocyanate (H12MDI). This type of isocyanate is suitable for preparing lightweight, stable polyurethane coatings and paints. H12MDA products with a t,t-H12MDA mass fraction below 16% are mainly used in fields with extreme requirements for material purity, processing fluidity, and optical properties. Furthermore, H12MDA with low t,t-H12MDA content is also commonly used as a curing agent for epoxy resins.

[0003] For the preparation of H12MDA with low t,t-H12MDA content, various traditional techniques have been proposed. For example, CN117658824A discloses a method using 4,4'-diaminodiphenylmethane (MDA) and diaminomonocyclohexylmonophenylmethane (H6MDA) as raw materials, and controlling the t,t-H12MDA content within a small range by controlling the heating rate and selecting different catalysts and supports. CN119822967A proposes to achieve high reaction yield and low t,t-H12MDA content of 13% to 15% by pretreating the catalyst and optimizing the reaction process. However, this method uses a batch reactor, which makes it difficult to achieve continuous production and cannot flexibly adjust the t,t-H12MDA ratio in the H12MDA product according to market demand. US5196594A discloses a continuous MDA hydrogenation process using supported ruthenium as a catalyst, achieving an H12MDA yield of up to 93.7%. However, the mass fraction of the trans-trans stereoisomer in the product is greater than 20%, which is insufficient to meet the demand for low-content t,t-H12MDA.

[0004] This demonstrates that different application areas have varying requirements for the t,t-H12MDA ratio in H12MDA products. To meet diverse market demands, production needs to be capable of preparing H12MDA products with various t,t-H12MDA ratios. However, the aforementioned traditional technologies are limited to preparing H12MDA products with specific low t,t-H12MDA contents, and cannot flexibly adjust the t,t-H12MDA ratio in H12MDA products according to changes in market demand. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for preparing H12MDA with a controllable t,t-H12MDA ratio to address the above problems. This method can switch between preparing H12MDA products with different t,t-H12MDA contents in real time and flexibly during the production process to meet diverse application needs.

[0006] A method for preparing H12MDA with controllable t,t-H12MDA ratio involves passing a mixture of 4,4'-diaminodiphenylmethane and a solvent sequentially through a first reactor and a second reactor connected in series for catalytic hydrogenation to generate 4,4'-diaminodicyclohexylmethane. The first reactor and the second reactor are respectively packed with phosphorus-modified platinum group supported C3N4 catalysts. The mass fraction of t,t-H12MDA in the product is controlled by adjusting the reaction parameters of the first reactor and the second reactor.

[0007] In the first reactor, the mass fraction Y of cis-diaminomonocyclohexylmonophenylmethane in the product is controlled according to the first characteristic formula: Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)} 2 / 225+ (lnW1-ln1.35) 2 / 0.64]} ×100%, where W1 is the mass hourly space velocity of the first reactor, T1 is the reaction temperature of the first reactor, and P1 is the reaction pressure of the first reactor;

[0008] In the second reactor, the mass fraction Z of t,t-H12MDA in the product is controlled according to the second characteristic formula: Z={0.06+ 0.05× exp(-4×(Y-0.6))× [1+((T2-120) / 40)} 2 +4×((W2-0.85) / 0.84) 2 W2 × (1.2-0.1×P2)} ×100%, where W2 is the mass hourly space velocity of the second reactor, T2 is the reaction temperature of the second reactor, and P2 is the reaction pressure of the second reactor.

[0009] In one embodiment, the mass hourly space velocity (MSV) of the first reactor is 0.1 h⁻¹. -1 ~1.35h -1 .

[0010] In one embodiment, the reaction temperature of the first reactor is 110°C to 155°C.

[0011] In one embodiment, the reaction pressure of the first reactor is 3 MPa to 7 MPa.

[0012] In one embodiment, the mass hourly space velocity (MSV) of the second reactor is 0.2 h⁻¹. -1 ~0.85h -1 .

[0013] In one embodiment, the reaction temperature of the second reactor is 120°C to 160°C.

[0014] In one embodiment, the reaction pressure of the second reactor is 4 MPa to 10 MPa.

[0015] In one embodiment, the phosphorus-modified platinum group supported C3N4 catalyst has a graphite phase as its crystalline phase.

[0016] And / or, in the phosphorus-modified platinum group supported C3N4 catalyst, the platinum group metals are selected from Ru and Rh.

[0017] In one embodiment, the phosphorus-modified platinum group supported C3N4 catalyst has phosphorus at a mass of 1% to 20% of the C3N4 mass.

[0018] And / or, based on the total mass of the phosphorus-modified platinum group supported C3N4 catalyst, the mass fraction of Ru is 0.1%~2% and the mass fraction of Rh is 0.1%~2%.

[0019] In one embodiment, the mass ratio of the solvent to the MDA is 1:1 to 8:1.

[0020] In this invention, the phosphorus-modified platinum group supported C3N4 catalyst exhibits high selectivity for cis-H6MDA (c-H6MDA). Based on this, and combined with a series reactor process, the MDA material is first fed into a first reactor packed with the phosphorus-modified platinum group supported C3N4 catalyst. The reaction conditions are adjusted according to a first characteristic formula to directionally obtain c-H6MDA intermediates with different proportions. Subsequently, the reaction liquid from the first reactor is introduced into a second reactor packed with the phosphorus-modified platinum group supported C3N4 catalyst. The reaction conditions are adjusted according to a second characteristic formula to achieve deep hydrogenation of H6MDA, producing H12MDA products with specific t,t-H12MDA content.

[0021] The preparation method of this invention combines the high selectivity of the catalyst with the segmented and precise control of the characteristic formula to effectively control the occurrence of the isomerization reaction from the source of the reaction. Therefore, the process conditions can be switched in real time during the production process according to the needs, and H12MDA products with different t,t-H12MDA contents can be prepared easily and quickly without interrupting the reaction, thereby meeting diverse application needs. Detailed Implementation

[0022] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0023] 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 specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all the related listed items.

[0024] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0025] Studies have found that in traditional methods for producing H12MDA via the hydrogenation catalytic reaction of MDA, Al2O3 is the primary catalyst support. However, the use of Al2O3 supports presents two problems: Firstly, polycyclic cyclic amines are generated as byproducts during the reaction. These byproducts easily adhere to the catalyst surface, clogging active sites and leading to catalyst deactivation. Secondly, because Al2O3 possesses both acidic and basic properties, its weakly acidic sites can release H+ through proton interactions (i.e., acidic sites release H+). + The amino group (-NH2) on the c-H6MDA molecule is pulled. Since the two amino groups of c-H6MDA are located on the same side of the molecule, H... +The pulling effect disrupts the bond angle balance within the molecule, forcing the amino group to twist to the opposite side, thus transforming it into trans-H6MDA (t-H6MDA). Consequently, the content of t,t-H12MDA becomes difficult to control effectively during subsequent deep hydrogenation processes.

[0026] In addition, during the catalytic hydrogenation reaction, process parameters such as mass hourly space velocity (MHSV), reaction temperature, and reaction pressure all have a significant impact on the ratio of t and t-H12MDA in the H12MDA product: (1) Influence of mass hourly space velocity (MHSV): MDA needs to go through three steps to generate c-H6MDA: "adsorption at hydrogenation sites → activation of the benzene ring and π bond breakage → hydrogen dissociation followed by addition". Therefore, the MHSV determines the degree of reaction of H6MDA on the catalyst surface. When the MHSV is too high, the residence time is too short, and a large amount of unreacted MDA enters the next stage reactor, skipping the H6MDA generation step and directly undergoing excessive hydrogenation or deammoniation side reactions of the dibenzene ring, generating non-target impurities; when the MHSV is too low, the residence time is too long, and some c-H6MDA may be converted into t-H6MDA under the action of catalyst isomerization sites. (2) Effect of reaction temperature: Increased temperature favors the conversion of H12MDA isomers to the more thermodynamically stable trans-trans configuration. Therefore, considering only temperature variables, the higher the temperature, the higher the t,t-H12MDA content in the H12MDA product. (3) Effect of reaction pressure: Increasing the reaction pressure is beneficial to increasing the rate of benzene ring hydrogenation reaction, while inhibiting the conversion of H12MDA cis isomers to trans isomers.

[0027] In summary, to achieve controllable preparation of H12MDA products with different t,t-H12MDA contents, it is necessary to comprehensively consider the selection of catalyst support and optimization of process parameters, and establish a synergistic regulation mechanism among various parameters.

[0028] Based on this, the present invention provides a method for preparing H12MDA with controllable t,t-H12MDA ratio. The method first involves loading phosphorus-modified platinum group supported C3N4 catalysts into a first reactor and a second reactor connected in series.

[0029] The phosphorus-modified platinum group supported C3N4 catalyst used in this invention does not contain active sites that lead to the isomerization of H6MDA, thus exhibiting high selectivity for the catalytic hydrogenation of MDA to c-H6MDA. In addition, the phosphorus modification of the catalyst and the use of C3N4 as a support can provide abundant anchoring sites for the supported platinum group metals, thereby enhancing the catalytic hydrogenation capability of the phosphorus-modified platinum group supported C3N4 catalyst.

[0030] Furthermore, in the phosphorus-modified platinum group supported C3N4 catalyst, the platinum group metal can be selected from at least one of Ru, Rh, Pd, Pt, and Ir, preferably Ru and / or Rh; the catalyst can use only one platinum group metal, or two, three, or four platinum group metals can be used simultaneously, preferably two platinum group metals; more preferably, in the phosphorus-modified platinum group supported C3N4 catalyst, the platinum group metal is selected from Ru and Rh, represented as Ru-Rh-P-C3N4 catalyst. This catalyst can achieve high hydrogenation activity through bimetallic synergy, and can catalyze the MDA hydrogenation reaction without high temperature conditions, thereby effectively reducing the reaction temperature and reducing the content of t,t-H12MDA in the H12MDA product.

[0031] In the phosphorus-modified platinum group supported C3N4 catalyst, the mass of phosphorus is preferably 1% to 20% of the mass of C3N4, for example, any value or a range between 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% or 20%, so that the mass ratio of phosphorus can provide more sufficient anchoring of active sites of platinum group metals such as rhodium.

[0032] In the phosphorus-modified platinum group supported C3N4 catalyst, the crystalline phase of C3N4 is preferably graphite, denoted as g-C3N4 (graphite carbon nitride). This is because the g-C3N4 framework contains abundant pyridine nitrogen and pyrrole nitrogen atoms, which can generate strong coordination and anchoring abilities with platinum group metals such as ruthenium, thereby enhancing the loading capacity of the C3N4 support for active metals.

[0033] Based on the total mass of the phosphorus-modified platinum group supported C3N4 catalyst, the mass fraction of Ru loading is preferably 0.1% to 2%, and can be selected from any one of 0.1%, 0.5%, 1.0%, 1.5%, or 2%, or any range between two values; the mass fraction of Rh loading is preferably 0.1% to 2%, and can be selected from any one of 0.1%, 0.5%, 1.0%, 1.5%, or 2%, or any range between two values. Using this preferred range, the Ru-Rh-P-C3N4 catalyst can achieve better catalytic activity.

[0034] It should be noted that the Ru-Rh-P-C3N4 catalyst can be obtained by the following preparation methods: impregnating g-C3N4 in an aqueous solution of a ruthenium compound and reducing it under hydrogen to obtain Ru-g-C3N4; impregnating Ru-g-C3N4 in an aqueous solution of a phosphorus-containing compound and calcining it under an inert atmosphere to obtain phosphorus-modified Ru-Pg-C3N4; impregnating Ru-Pg-C3N4 in an aqueous solution of a rhodium compound and reducing it under hydrogen to obtain the Ru-Rh-P-C3N4 catalyst; and forming the Ru-Rh-P-C3N4 catalyst into microspheres using an inclined disk granulator and calcining them to obtain Ru-Rh-P-C3N4 catalyst particles.

[0035] Then, the mixture of MDA and solvent is passed sequentially through a first reactor and a second reactor connected in series for catalytic hydrogenation to generate H12MDA. The mass fraction of t,t-H12MDA in the product is controlled by adjusting the reaction parameters of the first reactor and the second reactor.

[0036] In some embodiments, the mass ratio of solvent to MDA in the solvent-MDA mixture is preferably 1:1 to 8:1, and can be selected as any ratio of 1:1, 2:1, 4:1, 6:1 or 8:1. The solvent is preferably at least one of n-butanol, tetrahydrofuran, methanol, ethanol, isopropanol or diethyl ether.

[0037] Specifically, in the step of passing the mixture of MDA and solvent into the first reactor packed with a phosphorus-modified platinum group supported C3N4 catalyst, the mass fraction Y of c-H6MDA in the product is controlled according to the first characteristic formula: Y={0.6+0.3×(0.2P1-0.4) ×1 / exp[(T1-110)} 2 / 225+(lnW1-ln1.35) 2 / 0.64]}× 100%, where W1 is the mass hourly space velocity (h) of the first reactor. -1 T1 is the reaction temperature of the first reactor, in °C; P1 is the reaction pressure of the first reactor, in MPa. By adjusting the reaction conditions according to the first characteristic formula, c-H6MDA intermediates with different mass fractions can be obtained directionally.

[0038] Optionally, the mass hourly space velocity (MSV) of the first reactor is preferably 0.1 h⁻¹. -1 ~1.35h -1 0.1h is an option. -1 0.3h -1 0.5h -1 0.7h -1 0.9h -1 1.1h -1 1.2h-1 1.3h -1 Or 1.35h -1 The value at any point in the range or any range between the two can effectively control the amount of c-H6MDA generated, which is beneficial for the subsequent preparation of H12MDA with a specific t,t-H12MDA content.

[0039] Optionally, the reaction temperature of the first reactor is preferably 110℃~155℃, and can be any point or range between 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃ or 155℃. Within this range, the amount of c-H6MDA generated can be effectively controlled, which is beneficial for the subsequent preparation of H12MDA with a specific t,t-H12MDA content.

[0040] Optionally, the reaction pressure of the first reactor is preferably 3MPa to 7MPa, and can be any value among 3MPa, 4MPa, 5MPa, 6MPa or 7MPa or any range between two of them. Within this range, the amount of c-H6MDA generated can be effectively controlled, which is beneficial for the subsequent preparation of H12MDA with a specific t,t-H12MDA content.

[0041] Specifically, in the step of introducing the reaction liquid from the first reactor into the second reactor packed with a phosphorus-modified platinum group supported C3N4 catalyst, the mass fraction Z of t,t-H12MDA in the product is controlled according to the second characteristic formula: Z={0.06+0.05×exp(-4×(Y-0.6))×[1+((T2-120) / 40)} 2 +4×((W2-0.85) / 0.84) 2 W2 is the mass hourly space velocity (W2) of the second reactor, expressed as W2 × (1.2 - 0.1 × P2) × 100%, where W2 is the mass hourly space velocity (H2) of the second reactor. -1 T2 is the reaction temperature of the second reactor, in °C; P2 is the reaction pressure of the second reactor, in MPa; Y is the mass fraction of c-H6MDA calculated by the first characteristic formula. The reaction conditions are adjusted according to the second characteristic formula to achieve deep hydrogenation of H6MDA, producing H12MDA products with a specific t,t-H12MDA content. Specifically, the mass fraction of t,t-H12MDA in the H12MDA product can be adjusted to a range of 6% to 24%. For example, the mass fraction of t,t-H12MDA can be adjusted to any value among 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, or 24%, or any value between any two, depending on the requirements.

[0042] Optionally, the mass hourly space velocity (MSV) of the second reactor is preferably 0.2 h⁻¹. -1 ~0.85h -1 0.2h is an option. -1 0.3h -1 0.4h -1 0.5h -1 0.6h -1 0.7h -1 or 0.85h -1 Any point value in the range or any range between the two can more effectively achieve the controllable production of H12MDA products with the target t,t-H12MDA content.

[0043] Optionally, the reaction temperature of the second reactor is preferably 120℃~160℃, and can be any point or range between 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃ or 160℃. Within this range, the controllable production of H12MDA products with the target t,t-H12MDA content can be achieved more effectively.

[0044] Optionally, the reaction pressure of the second reactor is preferably 4MPa to 10MPa, and can be any value among 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa or any range between two of them. Within this range, the controllable production of H12MDA products with the target t,t-H12MDA content can be achieved more effectively.

[0045] The preparation method of this invention combines the high selectivity of the catalyst with the segmented and precise control of the characteristic formula to effectively control the occurrence of the isomerization reaction from the source of the reaction. Therefore, the process conditions can be switched in real time during the production process according to the needs, and H12MDA products with the target t,t-H12MDA content can be prepared easily and quickly without interrupting the reaction, thereby meeting diverse application needs.

[0046] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0047] Example 1

[0048] Equal amounts of Ru-Rh-P-C3N4 catalyst were loaded into a primary fixed-bed reactor and a secondary fixed-bed reactor, respectively. In the Ru-Rh-P-C3N4 catalyst, the Ru loading was 1%, the Rh loading was 1%, and the mass of phosphorus was 8% of the mass of g-C3N4.

[0049] After the catalyst was loaded, the primary fixed-bed reactor was purged three times with N2 at 0.6 MPa, followed by three purgings with H2 at 1 MPa. After the purgings, the pressure was increased to 6 MPa with H2, and the primary fixed-bed reactor was heated to 110 °C. A premix of n-butanol and MDA at a mass ratio of 4:1 was introduced into the primary fixed-bed reactor, with a controlled mass hourly space velocity (HHSV) of 1.35 h⁻¹. -1 The above process parameters, namely mass hourly space velocity W1 = 1.35 h, are used. -1 Substituting the reaction temperature T1 = 110℃ and the reaction pressure P1 = 6MPa into the first characteristic formula Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)}, we get Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)}}. 2 / 225+(lnW1-ln1.35) 2 The theoretical value of the mass fraction Y of c-H6MDA is 84.00% (calculated by 0.64]} ×100%. Gas chromatography analysis was performed on the reaction liquid from the primary fixed-bed reactor, and the results are shown in Table 1.

[0050] Table 1

[0051]

[0052] The secondary fixed-bed reactor was purged three times with N2 at 0.6 MPa, followed by three times with H2 at 1 MPa. After purging, the pressure was increased to 4 MPa with H2, and the secondary fixed-bed reactor was heated to 120 °C. The reaction solution from the primary fixed-bed reactor was then introduced into the secondary fixed-bed reactor, with a mass hourly space velocity (WHSV) of 0.30 h⁻¹. -1 The above process parameters and the theoretical value of the mass fraction of c-H6MDA, i.e., mass hourly space velocity W2 = 0.30 h⁻¹, are then used. -1 Substituting the reaction temperature T2 = 120℃, reaction pressure P2 = 4MPa, and the mass fraction of c-H6MDA Y = 84.00%, into the second characteristic formula Z = {0.06 + 0.05 × exp(-4 × (Y - 0.6)) × [1 + ((T2 - 120) / 40)}, we get Z = {0.06 + 0.05 × exp(-4 × (Y - 0.6)) × [1 + ((T2 - 120) / 40)} ... 2 +4 ×((W2-0.85) / 0.84) 2 The theoretical value of the mass fraction Z of t,t-H12MDA was calculated as 10.16% by multiplying 1.2 by (1.2-0.1×P2) by 100%. Gas chromatography analysis was performed on the reaction liquid from the two-stage fixed-bed reactor, and the results are shown in Table 2.

[0053] Table 2

[0054]

[0055] Example 2

[0056] Example 2 aims to prepare H12MDA with a mass fraction of 8.1% (t,t-H12MDA). Based on the second characteristic formula, and building upon Example 1, only the mass hourly space velocity (MSV) of the secondary fixed-bed reactor was adjusted to 0.6 h⁻¹. -1 Other reaction conditions and operations were the same as in Example 1. The reaction liquid from the two-stage fixed-bed reactor was analyzed by gas chromatography, and the results are shown in Table 3.

[0057] Table 3

[0058]

[0059] Example 3

[0060] Example 3 aimed to prepare H12MDA with a mass fraction of 8.1% (t,t-H12MDA). Based on the second characteristic formula, and building upon Example 1, only the reaction pressure of the secondary fixed-bed reactor was adjusted to 8 MPa; all other reaction conditions and operations remained the same as in Example 1. The reaction liquid from the secondary fixed-bed reactor was analyzed by gas chromatography, and the results are shown in Table 4.

[0061] Table 4

[0062]

[0063] Example 4

[0064] Example 4 aimed to prepare H12MDA with a mass fraction of 11.7% (t,t-H12MDA). Based on the second characteristic formula, and building upon Example 1, only the reaction temperature of the two-stage fixed-bed reactor was adjusted to 160°C; all other reaction conditions and operations remained the same as in Example 1. The reaction liquid from the two-stage fixed-bed reactor was analyzed by gas chromatography, and the results are shown in Table 5.

[0065] Table 5

[0066]

[0067] Example 5

[0068] Example 5 aimed to prepare H12MDA with a mass fraction of 14.2% (t,t-H12MDA). Based on the first and second characteristic formulas, and building upon Example 1, only the mass hourly space velocity (MSV) of the primary fixed-bed reactor was adjusted to 0.56 h⁻¹. -1Other reaction conditions and operations were the same as in Example 1. The theoretical value of the mass fraction Y of c-H6MDA was 67.16%. The reaction liquid from the primary fixed-bed reactor was analyzed by gas chromatography, and the results are shown in Table 6.

[0069] Table 6

[0070]

[0071] The reaction liquid from the secondary fixed-bed reactor of this embodiment was analyzed by gas chromatography, and the results are shown in Table 7.

[0072] Table 7

[0073]

[0074] Example 6

[0075] Example 6 aimed to prepare H12MDA with a mass fraction of 12.0% (t,t-H12MDA). Based on the first and second characteristic formulas, and building upon Example 1, only the reaction pressure of the primary fixed-bed reactor was adjusted to 4.5 MPa; all other reaction conditions and operations remained the same. The theoretical value of the mass fraction Y of c-H6MDA was 75.00%. Gas chromatography analysis was performed on the reaction liquid from the primary fixed-bed reactor, and the results are shown in Table 8.

[0076] Table 8

[0077]

[0078] The reaction liquid from the secondary fixed-bed reactor of this embodiment was subjected to gas chromatography analysis, and the results are shown in Table 9.

[0079] Table 9

[0080]

[0081] Example 7

[0082] Example 7 aimed to prepare H12MDA with a mass fraction of 16.2% (t,t-H12MDA). Based on the first and second characteristic formulas, and building upon Example 1, only the reaction temperature of the primary fixed-bed reactor was adjusted to 135°C; all other reaction conditions and operations remained the same. The theoretical value of the mass fraction Y of c-H6MDA was 61.49%. Gas chromatography analysis was performed on the reaction liquid from the primary fixed-bed reactor, and the results are shown in Table 10.

[0083] Table 10

[0084]

[0085] The reaction liquid from the secondary fixed-bed reactor of this embodiment was analyzed by gas chromatography, and the results are shown in Table 11.

[0086] Table 11

[0087]

[0088] Comparative Example 1

[0089] A Ru-K / α-Al₂O₃ catalyst was loaded into a primary fixed-bed reactor. The Ru-K / α-Al₂O₃ catalyst had a Ru loading of 5% and a K loading of 0.5%. An Rh-La / γ-Al₂O₃ catalyst of the same mass as the Ru-K / α-Al₂O₃ catalyst was loaded into a secondary fixed-bed reactor. The Rh-La / γ-Al₂O₃ catalyst had a Rh loading of 2% and a La loading of 0.1%.

[0090] After catalyst loading, the primary fixed-bed reactor was purged three times with N2 at 0.6 MPa, followed by three purgings with H2 at 1 MPa. After purging, the pressure was increased to 6 MPa with H2, and the primary fixed-bed reactor was heated to 80°C. A premixed mixture of n-butanol and MDA at a mass ratio of 4:1 was introduced into the primary fixed-bed reactor, with a controlled mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The above process parameters, namely mass hourly space velocity W1 = 1h, are used. -1 Substituting the reaction temperature T1 = 80℃ and the reaction pressure P1 = 6MPa into the first characteristic formula Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)}, we get Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)}}. 2 / 225+(lnW1-ln1.35) 2 The theoretical value of the mass fraction Y of c-H6MDA is 60.38% (calculated by multiplying the mass fraction by 0.64%). Gas chromatography analysis was performed on the reaction liquid from the primary fixed-bed reactor, and the results are shown in Table 12.

[0091] Table 12

[0092]

[0093] The secondary fixed-bed reactor was purged three times with N2 at 0.6 MPa, followed by three times with H2 at 1 MPa. After the purging was complete, the pressure was increased to 6 MPa with H2, and the secondary fixed-bed reactor was heated to 140 °C. The reaction solution from the primary fixed-bed reactor was then introduced into the secondary fixed-bed reactor, with a mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The above process parameters and the theoretical value of the mass fraction of c-H6MDA, i.e., mass hourly space velocity W2 = 1 h, are used. -1Substituting the reaction temperature T2 = 140℃, reaction pressure P2 = 6MPa, and the mass fraction of c-H6MDA Y = 60.38% into the second characteristic formula Z = {0.06 + 0.05 × exp(-4 × (Y - 0.6)) × [1 + ((T2 - 120) / 40)}, we get Z = {0.06 + 0.05 × exp(-4 × (Y - 0.6)) × [1 + ((T2 - 120) / 40)}}. 2 +4×((W2-0.85) / 0.84) 2 The theoretical value of the mass fraction Z of t,t-H12MDA was calculated as 10.07% by multiplying 100% by (1.2-0.1 ×P2) by 100%. Gas chromatography analysis was performed on the reaction liquid from the two-stage fixed-bed reactor, and the results are shown in Table 13.

[0094] Table 13

[0095]

[0096] As can be seen from the test data of the above embodiments, in the first reactor, using the Ru-Rh-P-C3N4 catalyst for catalytic hydrogenation of MDA, the target content of c-H6MDA can be obtained according to the first characteristic formula; in the second reactor, using the Ru-Rh-P-C3N4 catalyst for catalytic hydrogenation of MDA, the target content of t,t-H12MDA can be obtained according to the second characteristic formula.

[0097] As can be seen from the test data of Comparative Example 1, in the first reactor, using a catalyst containing Al2O3, the target content of c-H6MDA could not be obtained according to the first characteristic formula; in the second reactor, using a catalyst containing Al2O3, the target content of t,t-H12MDA could not be obtained according to the second characteristic formula.

[0098] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments 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.

[0099] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. 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. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio, characterized in that, A mixture of 4,4'-diaminodiphenylmethane and a solvent is passed sequentially through a first reactor and a second reactor connected in series for catalytic hydrogenation to produce 4,4'-diaminodicyclohexylmethane. The first reactor and the second reactor are respectively packed with phosphorus-modified platinum group supported C3N4 catalysts. The mass fraction of the trans / trans stereoisomer in the product is controlled by adjusting the reaction parameters of the first reactor and the second reactor. In the first reactor, the mass fraction Y of cis-diaminomonocyclohexylmonophenylmethane in the product is controlled according to the first characteristic formula: Y = {0.6 + 0.3 × (0.2P1 - 0.4) × 1 / exp[(T1 - 110)} 2 / 225+ (lnW1-ln1.35) 2 / 0.64]} ×100%, where W1 is the mass hourly space velocity of the first reactor, T1 is the reaction temperature of the first reactor, and P1 is the reaction pressure of the first reactor; In the second reactor, the mass fraction Z of the trans / trans stereoisomer in the product is controlled according to the second characteristic formula: Z = {0.06 + 0.05 × exp(-4 × (Y - 0.6)) × [1 + ((T2 - 120) / 40)} 2 +4×((W2-0.85) / 0.84) 2 W2 × (1.2-0.1×P2)} ×100%, where W2 is the mass hourly space velocity of the second reactor, T2 is the reaction temperature of the second reactor, and P2 is the reaction pressure of the second reactor.

2. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1, characterized in that, The mass hourly space velocity (MSV) of the first reactor is 0.1 h⁻¹. -1 ~1.35h -1 .

3. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1 or 2, characterized in that, The reaction temperature of the first reactor is 110℃~155℃.

4. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 3, characterized in that, The reaction pressure of the first reactor is 3MPa~7MPa.

5. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1, characterized in that, The mass hourly space velocity (MSV) of the second reactor is 0.2 h⁻¹. -1 ~0.85h -1 .

6. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1 or 5, characterized in that, The reaction temperature of the second reactor is 120℃~160℃.

7. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 6, characterized in that, The reaction pressure of the second reactor is 4 MPa to 10 MPa.

8. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1, characterized in that, In the phosphorus-modified platinum group supported C3N4 catalyst, the crystalline phase of C3N4 is the graphite phase; And / or, in the phosphorus-modified platinum group supported C3N4 catalyst, the platinum group metals are selected from Ru and Rh.

9. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 8, characterized in that, The phosphorus-modified platinum group supported C3N4 catalyst has a phosphorus content of 1% to 20% of the C3N4 mass. And / or, based on the total mass of the phosphorus-modified platinum group supported C3N4 catalyst, the mass fraction of Ru is 0.1%~2% and the mass fraction of Rh is 0.1%~2%.

10. The method for preparing 4,4'-diaminodicyclohexylmethane with controllable trans / trans stereoisomer ratio according to claim 1, characterized in that, The mass ratio of the solvent to the 4,4'-diaminodiphenylmethane is 1:1 to 8:1.

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