Ru-sn catalyst for hydro synthesis of chdm from dmcd, synthesis method and application thereof

Abstract

The application discloses a RuSn catalyst for synthesizing 1,4-cyclohexane dimethanol CHDM by hydrogenating 1,4-cyclohexane dimethyl ester DMCD. The application adopts an active component with a Ru3Sn7 crystal phase alloy as a core, and through the synergistic effect of Ru dissociation H2 and Sn regulation of Ru electron density, the ester group hydrogenation activity is improved, and a (Mg-Zn) Al2O4 carrier modified by Mg and Zn is matched to reduce side reactions. The catalyst can efficiently convert DMCD under mild conditions of 180-220 DEG C and 4-8 MPa, and the activity, selectivity and stability are superior to those of the prior art, and the problems that the ester group hydrogenation and the reaction conditions and selectivity are difficult to be considered are solved, thereby providing support for efficient and green synthesis of CHDM.

Description

Technical Field

[0001] This invention belongs to the field of hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate, specifically relating to a RuSn catalyst, its synthesis method, and its application in the hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate to 1,4-cyclohexanediethanol. Background Technology

[0002] 1,4-Cyclohexanediethanol (CHDM) is an important polymer monomer, especially as a key raw material for the preparation of high-performance polyester materials (such as PETG and PCT), and its market demand continues to grow. Industrially, CHDM is mainly synthesized by the catalytic hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate (DMCD).

[0003] However, the presence of two ester groups (-COO-) in the DMCD molecule, which are difficult to hydrogenate directly, poses a significant challenge to this synthesis reaction. While the hydrogenation of ester groups is thermodynamically a slightly exothermic or near-equilibrium process, it presents a very high energy barrier kinetically, requiring the breaking of strong C=O bonds and multiple hydrogenation steps. Therefore, it typically demands extremely harsh reaction conditions (such as temperatures above 200°C and hydrogen pressures exceeding 10 MPa). This not only places stringent requirements on the reaction equipment but also results in enormous energy consumption.

[0004] Currently, this process route still faces a core bottleneck: a lack of efficient and stable catalysts. Traditional hydrogenation catalysts (such as supported Cu and Ni-based catalysts) often exhibit insufficient activity in this reaction, requiring higher temperatures and pressures, and are prone to side reactions such as over-hydrogenation and cracking, leading to reduced selectivity for the target product CHDM. While some noble metal catalysts (such as Ru and Pd) possess certain activation capabilities for C=O bonds, their excessive adsorption of reaction intermediates can easily lead to catalyst poisoning or deactivation, making it difficult to achieve efficient and highly selective conversion of DMCD.

[0005] Therefore, developing a novel catalyst that can combine high activity, high selectivity, and excellent stability under relatively mild process conditions has become an urgent need to promote the technological advancement and industrial upgrading of DMCD hydrogenation to CHDM. Summary of the Invention

[0006] To address the problems of low activity and difficulty in scaling up preparation methods in existing catalysts used for the hydrogenation synthesis of CHDM from DMCD, this invention provides a RuSn catalyst for the hydrogenation synthesis of CHDM from DMCD, its synthesis method, and its applications. The technical solution adopted in this invention is as follows:

[0007] The first aspect of this invention provides a RuSn catalyst for the hydrogenation synthesis of CHDM from DMCD, characterized in that the RuSn catalyst comprises a RuSn active component and a (Mg-Zn)Al2O4 spinel support, wherein: the atomic ratio of Ru to Sn in the RuSn active component is 1:(2.0-3.0), and the active component contains a Ru3Sn7 crystalline alloy; and the atomic ratio of Mg, Zn, and Al in the (Mg-Zn)Al2O4 spinel support is (0.4-0.6):(0.4-0.6):2.

[0008] Furthermore, the total loading of Ru and Sn in the catalyst is 5-15 wt%; and the particle size of the Ru3Sn7 crystalline alloy is 1-5 nm.

[0009] Furthermore, the (Mg-Zn)Al2O4 spinel support has a specific surface area of ​​80-200 m² / g and a pore size of 5-20 nm.

[0010] Furthermore, the catalyst is prepared by the following method, the preparation steps of which include:

[0011] (1) Preparation of (Mg-Zn)Al2O4 spinel support: Using aluminum isopropoxide, zinc nitrate and magnesium nitrate as raw materials, the precursor was synthesized by sol-gel method according to the atomic ratio of Mg, Zn and Al as (0.4-0.6):(0.4-0.6):2. The precursor was then calcined at 800-1000℃ for 4-6 hours to obtain (Mg-Zn)Al2O4 spinel support;

[0012] (2) Loading and alloying of active components: RuCl3・3H2O and SnCl2・2H2O were dissolved in ethylene glycol at an atomic ratio of 1:(2.0-3.0), and the (Mg-Zn)Al2O4 spinel support prepared in step (1) was added. The reaction was carried out at 120-150℃ for 4-8h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered and collected as solid product. The solid product was washed alternately with deionized water and ethanol until neutral, and dried at 110-130℃ for 8-12h to obtain the precursor solid.

[0013] (3) Reduction and annealing: The dried precursor solid was reduced at 400-500℃ for 2-3h in a hydrogen atmosphere, and then annealed at 500-600℃ for 1-2h in an inert atmosphere. After cooling, the RuSn catalyst was obtained.

[0014] The second aspect of the present invention provides the application of the RuSn catalyst described in any of the first aspects in the hydrogenation reaction of DMCD to CHDM.

[0015] Furthermore, in application, the reaction conditions include: a mass ratio of RuSn catalyst to DMCD of 1:(10-100); a reaction temperature of 180-220℃; and a hydrogen pressure of 4-8MPa.

[0016] Compared with existing technologies, this invention creatively solves the fundamental problem of low activity in direct hydrogenation of ester groups through the synergistic design of "Ru3Sn7 alloy active phase" and "(Mg-Zn)Al2O4 composite support", enabling the difficult reaction of hydrogenation of DMCD to CHDM to be carried out efficiently and selectively under mild conditions of 180-220℃ and 4-8MPa.

[0017] Specifically, it has the following beneficial effects:

[0018] (1) Precise design of active sites and excellent catalytic performance: This invention limits the atomic ratio of Ru to Sn to 1:(2.0-3.0) to ensure the formation of a Ru3Sn7 alloy with a specific structure, which is the key to highly active hydrogenation sites. The alloy can work synergistically: Ru is responsible for the activation and dissociation of H2, and Sn regulates the electron density of Ru, weakening the excessive adsorption of oxygen-containing intermediates. This promotes the hydrogenation reaction and inhibits side reactions, solving the problem of ester hydrogenation at the molecular level.

[0019] (2) The surface properties of the carrier can be adjusted to suppress side reactions: The (Mg-Zn)Al2O4 spinel carrier can be adjusted to have a moderate surface acidity and alkalinity by adjusting the ratio of Mg / Zn / Al. This can activate the reactants without causing side reactions (such as cracking, polymerization, etc.) due to excessive acidity or alkalinity. This is conducive to the selective hydrogenation of DMCD molecules to generate CHDM and improve the purity of the product.

[0020] (3) Stable support structure, providing strong metal-support interaction: The (Mg-Zn)Al2O4 spinel support is used as the support. It has a thermodynamically stable spinel structure and good crystallinity after high-temperature calcination. It is not prone to phase transformation or structural collapse under the high temperature and high pressure conditions of hydrogenation reaction, which ensures the long-term stability of the catalyst. At the same time, the spinel support can form a strong interaction (SMSI) with the active components Ru and Sn, which effectively anchors the metal nanoparticles and prevents them from migrating and sintering. This allows the Ru3Sn7 alloy nanoparticles to be uniformly dispersed in an ultra-small size of 1-5 nm (dispersion ≥80%) and remain stable.

[0021] (4) The preparation method has good repeatability and is suitable for large-scale production: The spinel support is prepared by sol-gel method, which can achieve uniform mixing of MgAl2O4 spinel phase and ZnAl2O4 spinel phase at the molecular level, ensuring the uniformity of the support composition. The subsequent hydrothermal loading, reduction and annealing steps have mild process conditions, good repeatability and easy control, which is suitable for the large-scale production of catalysts.

[0022] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention.

[0024] Figure 1 XRD patterns of RuSn catalysts in examples and comparative examples with different Mg / Zn / Al ratios.

[0025] Figure 2 XRD patterns of RuSn catalysts in examples and comparative examples with different Ru / Sn ratios.

[0026] Figure 3 The results show the characterization of the RuSn catalyst and the hydrogenation reaction of DMCD in the examples and comparative examples. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0029] Measurement methods used in the examples:

[0030] DMCD conversion rate = (molar amount of DMCD in the reaction solution before the hydrogenation reaction - molar amount of DMCD in the reaction solution after the hydrogenation reaction) / molar amount of DMCD in the reaction solution before the hydrogenation reaction × 100%;

[0031] CHDM selectivity = molar amount of CHDM in the reaction solution after the hydrogenation reaction / (molar amount of DMCD in the reaction solution before the hydrogenation reaction - molar amount of DMCD in the reaction solution after the hydrogenation reaction) × 100%.

[0032] Example 1

[0033] <Synthesis of RuSn catalyst>:

[0034] (1) Preparation of (Mg-Zn)Al2O4 spinel support: Weigh aluminum isopropoxide, zinc nitrate, and magnesium nitrate according to Mg:Zn:Al = 0.6:0.4:2 and dissolve them in isopropanol - deionized water (1:1); stir at 70 °C for 3 h to form a sol, and age at 80 °C for 18 h to form a gel; dry at 120 °C for 12 h and calcine at 900 °C for 5 h to obtain the support (containing MgAl2O4 and ZnAl2O4 double spinel phases; specific surface area 155 m² / g, pore diameter 12 nm).

[0035] (2) Loading and alloying of active components: Add 5.0 g of the above (Mg-Zn)Al2O4 support to an autoclave. Dissolve RuCl3·3H2O and SnCl2·2H2O in ethylene glycol according to Ru / Sn = 1:2.33 and pour it into the autoclave; react at 130 °C for 6 h under nitrogen protection, filter after cooling, wash with water - ethanol until neutral, and dry at 120 °C for 10 h to obtain the precursor solid.

[0036] (3) Reduction and annealing: Reduce the precursor in hydrogen at 450 °C for 2.5 h and anneal in nitrogen at 550 °C for 1.5 h, and cool to obtain the RuSn catalyst (Ru + Sn loading 10 wt%; Ru3Sn7 particle size 3 nm).

[0037] <DMCD hydrogenation reaction>: Add 1.0 g of DMCD, 0.1 g of the catalyst, and 20 mL of isopropanol to a reaction kettle, replace with nitrogen 3 times and then introduce hydrogen to 5.0 MPa; stir and react at 180 °C and 500 r / min for 4 h. Gas chromatography analysis: DMCD conversion rate 99%, CHDM selectivity 96%.

[0038] <Cyclic Stability Test>: The catalyst was recovered by centrifugation, washed with isopropanol, and dried at 120 °C for 6 h. The hydrogenation reaction was repeated 5 times. For the 5th cycle: the conversion rate of DMCD was 96%, the selectivity of CHDM was 92%, there was no obvious sintering of Ru3Sn7, and the double spinel phase of the (Mg-Zn)Al2O4 support remained stable.

[0039] Examples 2-3

[0040] In <RuSn Catalyst Synthesis>, the ratio of Mg:Zn:Al atomic ratio in the preparation step of the (Mg-Zn)Al2O4 spinel support was changed, and the rest was the same as in Example 1.

[0041] The reaction conditions in <DMCD Hydrogenation Reaction> and <Cyclic Stability Test> were the same as in Example 1, and the reaction results are shown in Figure 3 .

[0042] Examples 4-5

[0043] In <RuSn Catalyst Synthesis>, the ratio of Ru / Sn atomic ratio in the active component loading and alloying step was changed, and the rest was the same as in Example 1.

[0044] The reaction conditions in <DMCD Hydrogenation Reaction> and <Cyclic Stability Test> were the same as in Example 1, and the reaction results are shown in Figure 3 .

[0045] Examples 6-7

[0046] In <RuSn Catalyst Synthesis>, the total loading of Ru+Sn in the active component loading and alloying step was changed, and the rest was the same as in Example 1.

[0047] The reaction conditions in <DMCD Hydrogenation Reaction> and <Cyclic Stability Test> were the same as in Example 1, and the reaction results are shown in Figure 3 .

[0048] Comparative Examples 1-2

[0049] In <RuSn Catalyst Synthesis>, the ratio of Mg:Zn:Al in the preparation step of the (Mg-Zn)Al2O4 spinel support was changed, and the rest was the same as in Example 1.

[0050] The reaction conditions in <DMCD Hydrogenation Reaction> and <Cyclic Stability Test> were the same as in Example 1, and the reaction results are shown in Figure 3 .

[0051] Comparative Examples 3-4

[0052] In <RuSn Catalyst Synthesis>, the ratio of Ru / Sn in the active component loading and alloying step was changed, and the rest was the same as in Example 1.

[0053] The reaction conditions in <DMCD hydrogenation reaction> and <cyclic stability test> are the same as those in Example 1. The reaction results are shown in Figure 3 .

[0054] Comparative Example 5

[0055] <Synthesis of RuSn catalyst>: (1) Preparation of (Mg-Zn)Al2O4 spinel support and (2) Loading and alloying of active components are the same as those in Example 1. (3) Reduction and annealing: After the precursor is reduced in hydrogen at 450 °C for 2.5 h, it is directly cooled without going through the annealing step to obtain the RuSn catalyst.

[0056] <DMCD hydrogenation reaction>: Under the same reaction conditions as in Example 1, gas chromatography analysis: DMCD conversion rate is 95%, and CHDM selectivity is 92%.

[0057] <Cyclic stability test>: The reaction is repeated 5 times. In the 5th cycle: DMCD conversion rate is 88%, and CHDM selectivity is 86%.

[0058] Figure 1 XRD patterns of the RuSn catalysts in Examples 1-3 and Comparative Examples 1-2. It can be seen that in Examples 1-3, by limiting the ratio of Mg:Zn:Al atomic ratio in the preparation step of (Mg-Zn)Al2O4 spinel support within (0.4-0.6):(0.4-0.6):2, the (Mg-Zn)Al2O four-spinel support of the RuSn catalyst has relatively clean MgAl2O4 and ZnAl2O4 crystal phases; while in Comparative Example 1 and Comparative Example 2, when the ratio of Mg:Zn:Al atomic ratio is outside (0.4-0.6):(0.4-0.6):2, MgO or ZnO impurities are likely to appear in the (Mg-Zn)Al2O4 spinel support of the RuSn catalyst.

[0059] Combined with Figure 3The results of the DMCD hydrogenation reaction and cycle stability in Examples 1-3 and Comparative Examples 1-2 show that in Examples 1-3, when the ratio of Mg:Zn:Al atomic ratio in the preparation step of (1) (Mg-Zn)Al2O4 spinel support is limited to (0.4-0.6):(0.4-0.6):2, the (Mg-Zn)Al2O4 spinel support of the RuSn catalyst has relatively clean MgAl2O4 and ZnAl2O4 crystal phases, thus performing well in the DMCD hydrogenation to CHDM synthesis reaction. Conversely, in Comparative Examples 1-2, the reaction efficiency of DMCD hydrogenation to CHDM synthesis is greatly reduced due to the influence of MgO or ZnO impurities; the cycle stability of the catalyst is also poor.

[0060] Figure 2 The XRD patterns of the RuSn catalysts in Examples 1, 3-4, and Comparative Examples 3-5 are shown. It can be seen that in Examples 1 and 4-5, by limiting the ratio of Ru / Sn atomic ratio in the active component loading and alloying step (2) to within 1:(2.0-3.0), the active component in the prepared RuSn catalyst is a relatively clean Ru3Sn7 crystalline phase. However, in Comparative Examples 3-4, because the Ru / Sn atomic ratio is outside 1:(2.0-3.0), Ru elemental or SnO2 oxide impurities easily appear in the active component of the RuSn catalyst, thus affecting the reaction efficiency of DMCD hydrogenation to CHDM. From the XRD pattern of Comparative Example 5, it can be seen that because the catalyst was not annealed during preparation, the prepared RuSn catalyst does not contain the Ru3Sn7 crystalline phase, but only Ru and SnO2.

[0061] Combination Figure 3 From the results of the first hydrogenation reaction and the cycle reaction of DMCD in Examples 1 and 4-5, and Comparative Examples 3-4, it can be seen that in Examples 1 and 4-5, when the ratio of Ru / Sn atomic ratio in the active component loading and alloying step is limited to 1:(2.0-3.0), the active component in the prepared RuSn catalyst is a relatively clean Ru3Sn7 crystalline phase, which performs well in the DMCD hydrogenation to CHDM reaction. In contrast, in Comparative Examples 3-4, since the active component of the RuSn catalyst contains not only the Ru3Sn7 phase, but also Ru elemental or SnO2 oxide impurities, it performs poorly in the DMCD hydrogenation to CHDM reaction. In Comparative Example 5, since the prepared RuSn catalyst does not contain the Ru3Sn7 crystalline phase, but only Ru and SnO2, it performs poorly in the DMCD hydrogenation to CHDM reaction.

[0062] By comparison Figure 3The reaction results of the RuSn catalysts in Examples 1-7 and Comparative Examples 1-5 for the hydrogenation of DMCD to CHDM show that the RuSn catalyst of the present invention, through the synergistic advantages of the Ru3Sn7 crystal phase alloy and the (Mg-Zn)Al2O4 double spinel phase support, has excellent catalytic activity and cycle stability in the hydrogenation of DMCD to CHDM reaction.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A RuSn catalyst for the hydrogenation of DMCD to CHDM, characterized in that, The RuSn catalyst comprises a RuSn active component and a (Mg-Zn)Al2O4 spinel support, wherein: the RuSn active component contains a Ru3Sn7 crystal phase alloy, and the atomic ratio of Ru to Sn in the RuSn active component is 1:(2.0-3.0); the (Mg-Zn)Al2O4 spinel support comprises MgAl2O4 and ZnAl2O4 crystal phases, and the atomic ratio of Mg, Zn and Al is Mg:Zn:Al = (0.4-0.6):(0.4-0.6):

2.

2. The RuSn catalyst according to claim 1, characterized in that, The total loading of Ru and Sn in the catalyst is 5-15 wt%; and the particle size of the Ru3Sn7 crystalline alloy is 1-5 nm.

3. The RuSn catalyst according to claim 1, characterized in that, The (Mg-Zn)Al2O4 spinel support has a specific surface area of ​​80-200 m² / g and a pore size of 5-20 nm.

4. The RuSn catalyst according to claim 1, characterized in that, The catalyst is prepared by the following method, the preparation steps of which include: (1) Preparation of (Mg-Zn)Al2O4 spinel support: Using aluminum isopropoxide, zinc nitrate and magnesium nitrate as raw materials, the precursor was synthesized by sol-gel method according to the atomic ratio of Mg, Zn and Al: Mg: Zn:Al = (0.4-0.6): (0.4-0.6):

2. The precursor was then calcined at 800-1000℃ for 4-6 hours to obtain (Mg-Zn)Al2O4 spinel support; (2) Loading and alloying of active components: RuCl3·3H2O and SnCl2·2H2O were dissolved in ethylene glycol at an atomic ratio of Ru / Sn = 1:(2.0-3.0), and the (Mg-Zn)Al2O4 spinel support prepared in step (1) was added. The reaction was carried out at 120-150℃ for 4-8h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered and collected as solid product. The solid product was washed alternately with deionized water and ethanol until neutral, and dried at 110-130℃ for 8-12h to obtain the precursor solid. (3) Reduction and annealing: The dried precursor solid was reduced at 400-500℃ for 2-3h in a hydrogen atmosphere, and then annealed at 500-600℃ for 1-2h in an inert atmosphere. After cooling, the RuSn catalyst was obtained.

5. The application of the RuSn catalyst according to any one of claims 1-4 in the hydrogenation of DMCD to CHDM reaction.

6. The application according to claim 5, characterized in that, When applying this method, the reaction conditions include: a mass ratio of RuSn catalyst to DMCD of 1:(10-100); a reaction temperature of 180-220℃; and a hydrogen pressure of 4-8MPa.

Images