A promoter-enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol.

Abstract

This invention provides an auxiliary-enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol, belonging to the field of organic synthesis technology. This invention prepares an auxiliary-enhanced supported metal catalyst in which hydroxy fatty acid esters and hydrogen undergo a continuous hydrogenation reduction reaction to obtain 1,2-hexanediol. Compared with the traditional hexene route, the 1,2-hexanediol obtained by this invention has excellent purity, and odor impurities in the 1,2-hexanediol product can be removed, resulting in a product with extremely low odor, suitable for use in high-end cosmetics.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to an auxiliary enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol. Background Technology

[0002] 1,2-Hexanediol, also known as DL-1,2-hexanediol or DL-1,2-hexanediol, is a multifunctional organic compound widely used in various fields. As a chemical raw material, it is used to prepare polymer materials such as plastics, fibers, advanced coatings, high-grade adhesives, and binders. It is also an organic synthesis intermediate, used to manufacture downstream products such as 1,2-adipic acid and amino alcohols. Simultaneously, it plays an important role in the refrigeration, pharmaceutical, food, and cosmetic industries. In the pharmaceutical field, 1,2-hexanediol is used as a synthetic raw material. In the cosmetics industry, it acts as a moisturizer, solvent, and antimicrobial agent. In high-end cosmetics, it can act as a preservative and antiperspirant, adding deodorizing, bactericidal, and moisturizing effects to products.

[0003] Current research focuses on providing an economical, efficient, safe, and feasible continuous production method for 1,2-hexanediol to address its high price. Most current research uses 1-hexene as a starting material, involving epoxidation with an oxidant and hydrolysis to produce 1,2-hexanediol. Existing technologies mostly use H₂O₂ as the oxidant to oxidize organic acids into peroxy acids, which then react with 1-hexene to yield 1,2-hexanediol and its formate ester. Finally, hydrolysis under alkaline conditions yields 1,2-hexanediol. However, the product after alkaline hydrolysis requires a series of processing steps, including neutralization, extraction, drying, and distillation, to obtain the target product. This results in low product yields and generates high-salt wastewater containing sodium formate. Furthermore, controlling substances like peroxy acids is extremely challenging; improper control could lead to explosions, posing a serious threat to production safety. Market feedback indicates that 1,2-hexanediol, synthesized from 1-hexene through epoxidation and hydrolysis, has an unpleasant, herbal odor and cannot be directly used in the cosmetics market. This is mainly due to byproducts such as incomplete oxidation, excessive oxidation, or incomplete hydrolysis during the synthesis of 1,2-hexanediol.

[0004] To obtain odorless 1,2-hexanediol, the current industrial method involves multiple distillations to achieve a very high purity product, typically reaching 99.99%. However, this production method involves significant losses, resulting in low yields, which makes 1,2-hexanediol expensive for direct use in the cosmetics industry.

[0005] Therefore, there is an urgent need to develop a continuous production method for cosmetic-grade 1,2-hexanediol that is simple in process, low in cost, safe and reliable, and has low odor. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide an additive-enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol. This invention uses an additive-enhanced supported metal catalyst to prepare 1,2-hexanediol via a hydrogenation reduction reaction, enabling continuous production of low-odor cosmetic-grade 1,2-hexanediol. The process is simple and inexpensive.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing an additive-enhanced supported metal catalyst, comprising the following steps:

[0009] The silica sol, TiO2, ZrO2, Al2O3, water and alcohol dispersant were ultrasonically mixed to obtain a carrier precursor suspension.

[0010] Soluble copper salt, soluble zinc salt, complexing agent and water are mixed, and the pH of the resulting mixture is adjusted to 6.5~7.0. The mixture is then heated, stirred and allowed to stand for aging to obtain a metal sol-gel solution.

[0011] The carrier precursor suspension and K2CO3 solution were added to the metal sol-gel solution, and co-impregnation and loading were carried out under stirring. After removing excess solvent, a semi-solid gel product was obtained.

[0012] The semi-solid gel product was subjected to freeze-drying, granulation and gradient temperature drying in sequence to obtain the catalyst precursor;

[0013] The catalyst precursor was calcined and activated with hydrogen to obtain an additive-enhanced supported metal catalyst.

[0014] Preferably, the mass ratio of TiO2, ZrO2, and Al2O3 is 2~4:1:1;

[0015] The mass ratio of the silica sol to TiO2 is 2~5:1;

[0016] The mass of the alcohol dispersant is 10-30% of the mass of water.

[0017] Preferably, the Cu / Zn molar ratio of the soluble copper salt and the soluble zinc salt is 1~2:2~3;

[0018] The complexing agent is one or more of sodium citrate, ethylenediaminetetraacetic acid and tartaric acid;

[0019] In the mixture of soluble copper salt, soluble zinc salt, complexing agent and water, the concentration of the complexing agent is 0.1~0.3 mol / L.

[0020] Preferably, the heating and stirring temperature is 70~90℃, and the time is 0.5~1.5h;

[0021] The static aging time is 10~14h.

[0022] Preferably, the volume ratio of the carrier precursor suspension, K2CO3 solution, and metal sol-gel solution is 1:(0.2~0.5):(1.5~2.0).

[0023] The concentration of the K2CO3 solution is 0.05~0.2 mol / L;

[0024] The temperature of the co-impregnation load is 50~70℃, and the time is 2~4h.

[0025] Preferably, the gradient temperature drying includes drying at 50~70℃ for 4~8 hours and drying at 100~140℃ for 10~14 hours.

[0026] The calcination temperature is 280~320℃, and the holding time is 1.5~2.5h;

[0027] The hydrogen activation temperature is 480~520℃, and the holding time is 3.5~4.5h.

[0028] This invention provides an additive-enhanced supported metal catalyst prepared by the above preparation method.

[0029] This invention provides the application of the above-mentioned additive-enhanced supported metal catalyst in the production of 1,2-hexanediol.

[0030] This invention provides a method for continuous production of 1,2-hexanediol, comprising the following steps:

[0031] Hydroxy fatty acid esters and hydrogen undergo a continuous hydrogenation reduction reaction in the presence of a catalyst to yield 1,2-hexanediol;

[0032] The catalyst includes the aforementioned additive-enhanced supported metal catalyst.

[0033] Preferably, the continuous hydrogenation reduction reaction is carried out at a temperature of 140~200℃ and a pressure of 6~25MPa;

[0034] The space velocity of the continuous hydrogenation reduction reaction is 50-200 h⁻¹. -1 ;

[0035] The feed flow rate of the hydroxy fatty acid ester is 0.1~0.5 mL / min;

[0036] The molar ratio of the hydroxy fatty acid ester to hydrogen is 1:40~200;

[0037] The mass ratio of the hydroxy fatty acid ester to the catalyst is 100~600:1.

[0038] This invention provides a method for preparing an additive-enhanced supported metal catalyst. The method involves ultrasonically mixing silica sol, TiO2, ZrO2, Al2O3, water, and an alcohol dispersant to obtain a carrier precursor suspension. A soluble copper salt, a soluble zinc salt, a complexing agent, and water are mixed, and the pH of the resulting mixture is adjusted to 6.5-7.0. The mixture is then subjected to heating, stirring, and static aging to obtain a metal sol-gel solution. The carrier precursor suspension and a K2CO3 solution are added to the metal sol-gel solution, and co-impregnation and loading are performed under stirring. After removing excess solvent, a semi-solid gel product is obtained. The semi-solid gel product is then subjected to freeze-drying, granulation, and gradient temperature drying to obtain a catalyst precursor. Finally, the catalyst precursor is calcined and activated with hydrogen to obtain an additive-enhanced supported metal catalyst, specifically a K-additive-enhanced Cu-Zn / SiO2 catalyst. This invention uses SiO2 as a catalyst support. By introducing TiO2, ZrO2, and Al2O3 into the support, the structural stability of the support can be enhanced, the acid-base properties of the catalyst can be adjusted, and the dispersion and anti-sintering ability of the active metal can be improved. The addition of an alcohol dispersant can further improve the dispersion effect. Specifically, this invention employs a sol-gel method combined with a co-impregnation method to prepare the catalyst, ensuring that the Cu and Zn active components are uniformly loaded on the SiO2 support, improving the specific surface area and pore structure controllability of the catalyst, thereby enhancing catalytic activity and lifespan. Furthermore, calcination and hydrogen activation are used to form a catalyst with Cu... 0 -Cu + Synergistic active centers. This invention utilizes freeze-drying combined with gradient temperature drying to avoid catalyst precursor particle shrinkage and structural damage. By introducing a K₂CO₃ promoter (K ​​promoter), which exists in the catalyst as an alkali metal oxide or carbonate, the surface basicity of the catalyst is adjusted, enhancing the reducibility and catalytic activity of Cu species while suppressing side reactions, thus improving catalyst activity and selectivity. Furthermore, the introduction of TiO₂, ZrO₂, and Al₂O₃ enhances the stability of the support and metal anchoring, preventing the sintering and loss of Cu and Zn, ultimately forming a structurally stable and highly active catalyst system. The promoter-enhanced supported metal catalyst provided by this invention exhibits excellent reactivity and selectivity when used to produce 1,2-hexanediol, with minimal byproducts and a very low odor in the resulting 1,2-hexanediol product, meeting the requirements for cosmetic-grade 1,2-hexanediol.

[0039] This invention provides a continuous method for producing 1,2-hexanediol. In this method, hydroxy fatty acid esters and hydrogen undergo a continuous hydrogenation reduction reaction under the action of a catalyst to obtain 1,2-hexanediol. Compared with the traditional hexene route, this invention has the following significant advantages: minimal byproduct formation; the obtained 1,2-hexanediol has excellent purity; and odor impurities in the 1,2-hexanediol product are removed, resulting in a product with extremely low odor, suitable for use in high-end cosmetics. This invention successfully solves the problems of purity and odor in 1,2-hexanediol. The process is simple, low-cost, safe, and reliable, providing an efficient and feasible continuous production method for 1,2-hexanediol. This innovative method is expected to be widely used in the chemical industry, providing important technical support for the production of high-quality 1,2-hexanediol. Detailed Implementation

[0040] This invention provides a method for preparing an additive-enhanced supported metal catalyst, comprising the following steps:

[0041] The silica sol, TiO2, ZrO2, Al2O3, water and alcohol dispersant were ultrasonically mixed to obtain a carrier precursor suspension.

[0042] Soluble copper salt, soluble zinc salt, complexing agent and water are mixed, and the pH of the resulting mixture is adjusted to 6.5~7.0. The mixture is then heated, stirred and allowed to stand for aging to obtain a metal sol-gel solution.

[0043] The carrier precursor suspension and K2CO3 solution were added to the metal sol-gel solution, and co-impregnation and loading were carried out under stirring. After removing excess solvent, a semi-solid gel product was obtained.

[0044] The semi-solid gel product was subjected to freeze-drying, granulation, and gradient temperature drying in sequence to obtain a catalyst precursor.

[0045] The catalyst precursor was calcined and activated with hydrogen to obtain an additive-enhanced supported metal catalyst.

[0046] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0047] This invention involves ultrasonically mixing silica sol, TiO2, ZrO2, Al2O3, water, and an alcohol dispersant to obtain a carrier precursor suspension. In this invention, the TiO2, ZrO2, and Al2O3 are preferably in powder form, with a particle size preferably between 20 and 50 nm. The mass ratio of TiO2, ZrO2, and Al2O3 is preferably 2 to 4:1:1, more preferably 3:1:1. By adjusting the ratio of TiO2, ZrO2, and Al2O3 and reducing the Al2O3 content, this invention improves the surface properties of the catalyst. In this invention, improving the surface properties of the catalyst not only increases the dispersion of the metal and the number of active sites but also optimizes acid-base characteristics, enhances stability, and improves mass transfer efficiency, ultimately improving the overall activity and selectivity of the catalyst.

[0048] In this invention, the mass ratio of silica sol to TiO2 is preferably 2 to 5:1, specifically 2:1, 3:1, 4:1, or 5:1. In this invention, the water is preferably deionized water, and the mass ratio of silica sol to water is preferably 1:3.

[0049] In this invention, the alcohol dispersant is preferably ethanol. The mass of the alcohol dispersant is preferably 10-30% of the mass of water, specifically 10%, 15%, 20%, 25%, or 30%. By adding an alcohol dispersant, this invention can improve the dispersion effect of TiO2, ZrO2, and Al2O3.

[0050] In this invention, the power of the ultrasonic mixing is preferably 200~600 W, more preferably 300~500 W; the time is preferably 20~40 min, more preferably 30 min.

[0051] This invention involves mixing a soluble copper salt, a soluble zinc salt, a complexing agent, and water, adjusting the pH of the resulting mixture to 6.5-7.0, and then sequentially heating, stirring, and allowing it to stand for aging to obtain a metal sol-gel solution. In this invention, the soluble copper salt is preferably one or more of copper nitrate, copper acetate, copper sulfate, and copper chloride, and the soluble zinc salt is preferably one or more of zinc nitrate, zinc acetate, zinc sulfate, and zinc chloride. In this invention, the Cu / Zn molar ratio of the soluble copper salt and the soluble zinc salt is preferably 1-2:2-3, more preferably 2:3.

[0052] In this invention, the complexing agent is preferably one or more of sodium citrate, ethylenediaminetetraacetic acid, and tartaric acid; the mass ratio of the soluble copper salt to water is preferably 1:5 to 1:15, more preferably 1:10. In this invention, in the mixture of the soluble copper salt, soluble zinc salt, complexing agent, and water, the concentration of the complexing agent is preferably 0.1 to 0.3 mol / L, more preferably 0.2 mol / L. In this invention, the complexing agent functions to stabilize metal ions, regulate the precipitation rate, and optimize the structure of metal oxides.

[0053] In this invention, K₂CO₃ is preferably used to adjust the pH value to 6.5-7.0. In this invention, the heating and stirring temperature is preferably 70-90°C, more preferably 80°C, and the time is preferably 0.5-1.5 h, more preferably 1 h. Through the heating and stirring, this invention can form a metal sol-gel system.

[0054] In this invention, the preferred temperature for static aging is room temperature, and the preferred time is 10-14 hours, more preferably 12 hours. Through this static aging process, a uniform metal sol-gel structure is obtained.

[0055] After obtaining the carrier precursor suspension and the metal sol-gel solution, the present invention adds the carrier precursor suspension and K2CO3 solution to the metal sol-gel solution, and performs co-impregnation loading under stirring conditions. After removing excess solvent, a semi-solid gel product is obtained. In the present invention, the addition method is preferably dropwise; in the present invention, the volume ratio of the carrier precursor suspension, K2CO3 solution and metal sol-gel solution is preferably 1:(0.2~0.5):(1.5~2.0). In the present invention, the concentration of the K2CO3 solution is preferably 0.05~0.2 mol / L, more preferably 0.1~0.15 mol / L. The present invention uses K2CO3 solution as an auxiliary agent, which on the one hand can maintain the uniform distribution of the mixture, and on the other hand can improve the activity and selectivity of the catalyst.

[0056] In this invention, the stirring rate during co-impregnation loading is preferably 300~800 rpm, more preferably 500 rpm; the temperature of the co-impregnation loading is preferably 50~70℃, more preferably 60℃, and the time is preferably 2~4h, more preferably 3h.

[0057] In this invention, the method for removing excess solvent is preferably rotary evaporation, which is preferably carried out under vacuum conditions.

[0058] After obtaining the semi-solid gel product, the present invention sequentially freeze-dries, granulates, and performs gradient temperature drying on the semi-solid gel product to obtain a catalyst precursor. In the present invention, the freeze-drying temperature is preferably -45~-30℃, and the time is preferably 18~30h, more preferably 20~25h; the present invention avoids particle shrinkage and structural damage to the catalyst through freeze-drying.

[0059] In this invention, the granulation is preferably performed by pressing, and the shape of the granulated particles is preferably flake-shaped, spherical, or powder-shaped, more preferably spherical particles. The particle size is preferably 10~200μm, more preferably 50~150μm.

[0060] In this invention, the gradient temperature drying preferably includes drying at 50-70°C for 4-8 hours and then drying at 100-140°C for 10-14 hours. This gradient temperature drying method avoids particle shrinkage and structural damage to the catalyst precursor.

[0061] After obtaining the catalyst precursor, the present invention calcines and activates the catalyst precursor with hydrogen to obtain an additive-enhanced supported metal catalyst. In this invention, the calcination is preferably carried out in a tube furnace, and the calcination atmosphere is preferably nitrogen; the calcination temperature is preferably 280~320℃, more preferably 300℃, and the holding time is preferably 1.5~2.5h, more preferably 1h; in this invention, the heating rate to the calcination temperature is preferably 4~6℃ / min, more preferably 5℃ / min. By calcining at a relatively low temperature (280~320℃), this invention can improve the dispersibility and catalytic performance of the active metals Cu and Zn.

[0062] In this invention, the hydrogen activation atmosphere is preferably a mixture of hydrogen and nitrogen, wherein the volume fraction of hydrogen in the mixture is preferably 8-12%, more preferably 10%. In this invention, the hydrogen activation temperature is preferably 480-520°C, more preferably 500°C, and the activation time is preferably 3.5-4.5 hours, more preferably 4 hours. By controlling the hydrogen activation atmosphere and activation temperature, this invention can improve the dispersibility and catalytic performance of the active metals Cu and Zn in the catalyst.

[0063] After activation by hydrogen, the present invention preferably cools the obtained auxiliary-enhanced supported metal catalyst to room temperature, and the cooling is preferably carried out in an inert atmosphere.

[0064] This invention provides an additive-enhanced supported metal catalyst obtained by the above preparation method. This invention employs a sol-gel method combined with co-impregnation and loading technology, where Cu and Zn are uniformly dispersed on a SiO2 support, and then activated by calcination and hydrogen to form a catalyst with Cu... 0-Cu + Synergistic active centers. The K promoter, existing in the form of alkali metal oxides or carbonates, adjusts the surface basicity of the catalyst, enhancing the reducing power and catalytic activity of Cu species while suppressing side reactions. Furthermore, the introduction of TiO2, ZrO2, and Al2O3 enhances the stability of the support and the metal anchoring effect, preventing the sintering and loss of Cu and Zn, ultimately forming a structurally stable and highly active catalyst system.

[0065] This invention provides the application of the above-mentioned additive-enhanced supported metal catalyst in the production of 1,2-hexanediol.

[0066] This invention provides a method for continuous production of 1,2-hexanediol, comprising the following steps:

[0067] Hydroxy fatty acid esters and hydrogen undergo a continuous hydrogenation reduction reaction in the presence of a catalyst to yield 1,2-hexanediol;

[0068] The catalyst includes the above-mentioned additive-enhanced supported metal catalyst.

[0069] In this invention, the hydroxy fatty acid ester is preferably methyl 2-hydroxyhexanoate.

[0070] In this invention, the molar ratio of the hydroxy fatty acid ester to hydrogen is preferably 1:40 to 200, specifically 1:40, 1:60, 1:80, 1:100, 1:50, or 1:200. In this invention, the mass ratio of the hydroxy fatty acid ester to the catalyst is preferably 100 to 600:1, more preferably 200 to 400:1.

[0071] In this invention, the feed flow rate of the hydroxy fatty acid ester is preferably 0.1~0.5 mL / min, more preferably 0.2 mL / min.

[0072] In this invention, the temperature of the continuous hydrogenation reduction reaction is preferably 140-200°C, more preferably 160-190°C, and even more preferably 185-190°C; the pressure of the continuous hydrogenation reduction reaction is preferably 6-25 MPa, more preferably 12-15 MPa. In this invention, the space velocity of the continuous hydrogenation reduction reaction is preferably 50-200 h⁻¹. -1 More preferably 100~120 h -1 .

[0073] In this invention, after the hydrogenation reduction reaction, the resulting hydrogenation reduction product is preferably subjected to post-processing, which preferably includes the following steps:

[0074] The resulting hydrogenation reduction reaction product was subjected to steam distillation, adsorption purification, and rectification.

[0075] In this invention, the steam distillation temperature is preferably 110-120℃, and the time is preferably 2-6 h, more preferably 3-5 h; in this invention, the adsorbent for adsorption purification is preferably activated carbon and / or diatomaceous earth. In this invention, the distillation temperature is preferably 130-180℃, and the pressure is preferably 8-20 mmHg.

[0076] The following detailed description, in conjunction with embodiments, illustrates the additive-enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0077] Example 1

[0078] The preparation of the additive-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 additive)) adopts the following steps:

[0079] (1) Preparation of carrier precursor solution

[0080] Weigh 300 g of silica sol (Qingdao Ocean Chemical Co., Ltd. product, SW-30 type) and 100 g of powdered TiO2, 33.3 g of powdered ZrO2, and 33.3 g of powdered Al2O3 (mass ratio 3:1:1), add them to 500 g of deionized water, and add 100 g of ethanol to improve the dispersion effect. Place the resulting mixture in an ultrasonic cleaner and sonicate for 30 minutes to obtain a carrier precursor suspension.

[0081] (2) Preparation of metal sol-gel solution

[0082] 30.2 g of copper nitrate pentahydrate (Cu(NO3)2·5H2O) and 43.1 g of zinc nitrate tetrahydrate (Zn(NO3)2·4H2O) were weighed out and dissolved in 300 g of deionized water at a Cu / Zn molar ratio of 2:3. 18 g of sodium citrate was added as a complexing agent to stabilize the metal ions. The resulting solution was transferred to a three-necked flask, heated and stirred at 80 °C, and ammonia was added dropwise to adjust the pH to 6.5, simultaneously forming a metal sol-gel system. After stirring for 1 hour, the mixture was allowed to stand for 12 hours to age.

[0083] (3) Co-impregnation load

[0084] 200 mL of the carrier precursor suspension was added dropwise to 300 mL of the metal sol-gel solution, with 50 mL of 0.1 mol / L K₂CO₃ solution added as an auxiliary agent to maintain a uniform distribution of the mixture. The mixture was stirred at 500 rpm at 60 °C and maintained at this temperature for 3 hours. Subsequently, the mixture was transferred to a rotary evaporator, where excess solvent was removed under vacuum to obtain a semi-solid gel product.

[0085] (4) Molding and drying

[0086] The obtained semi-solid gel product was subjected to freeze-drying, granulation, and gradient temperature drying sequentially to prepare the catalyst precursor. First, freeze-drying was performed at -30℃ for 25 hours to avoid particle shrinkage and catalyst structural damage. Subsequently, granulation was carried out by pressing to obtain spherical particles with a particle size controlled between 50 and 150 μm. Finally, a gradient temperature drying process was used, first drying at 50℃ for 4 hours, then at 100℃ for 14 hours, to ensure the structural stability of the catalyst precursor and avoid particle shrinkage and damage.

[0087] (5) Calcination and activation

[0088] The dried product was placed in a tube furnace and heated to 300°C at a rate of 5°C / min under a nitrogen atmosphere, and calcined for 2 hours to form a preliminary structure. Then, the gas was switched to a hydrogen / nitrogen mixture (hydrogen component 10%), and the temperature was further increased to 500°C and calcined for 4 hours to reduce the metal oxide and enhance the active sites.

[0089] (6) Post-processing

[0090] After the calcined product is cooled to room temperature, it is sieved to obtain uniform catalyst particles, which are then stored in a sealed container for later use.

[0091] Example 2

[0092] The preparation of the additive-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 additive)) adopts the following steps:

[0093] (1) Preparation of carrier precursor solution

[0094] Weigh 250 g of silica sol (SW-30 type), 85 g of powdered TiO2, 28.3 g of powdered ZrO2, and 28.3 g of powdered Al2O3 (mass ratio 3:1:1), add them to 450 g of deionized water, and add 85 g of ethanol to improve the dispersion effect. Place the resulting mixture in an ultrasonic cleaner and sonicate for 30 minutes to obtain a carrier precursor suspension.

[0095] (2) Preparation of metal sol-gel solution

[0096] Weigh 25.1 g of copper nitrate pentahydrate (Cu(NO3)2·5H2O) and 35.5 g of zinc nitrate tetrahydrate (Zn(NO3)2·4H2O), dissolve them in 250 g of deionized water at a Cu / Zn molar ratio of 2:3, and add 15 g of complexing agent sodium citrate. Transfer the resulting solution to a three-necked flask, heat and stir at 75°C, adjust the pH to 6.8 by adding ammonia dropwise, continue stirring for 1 hour, and then let it stand for 12 hours to age.

[0097] (3) Co-impregnation load

[0098] 180 mL of the carrier precursor suspension was added dropwise to 270 mL of the metal sol-gel solution, followed by 45 mL of 0.1 mol / L K₂CO₃ solution as an auxiliary agent to maintain a uniform distribution of the mixture. The mixture was stirred at 500 rpm for 3 hours at 60 °C. Subsequently, the mixture was transferred to a rotary evaporator, and excess solvent was removed under vacuum to obtain a semi-solid gel product.

[0099] (4) Molding and drying

[0100] The resulting gel product was freeze-dried at -45°C for 24 hours, and then pressed into sheets with a particle size controlled between 50 and 150 μm. A gradient temperature drying method was used, first drying at 60°C for 6 hours, and then drying at 120°C for 12 hours to remove residual moisture.

[0101] (5) Calcination and activation

[0102] The dried catalyst precursor was placed in a tube furnace and calcined at 290°C for 2 hours under a nitrogen atmosphere at a rate of 5°C / min. Subsequently, the temperature was switched to a hydrogen / nitrogen mixture (hydrogen fraction 10%) and calcined at 500°C for 4 hours to reduce the metal oxide and form active centers.

[0103] (6) Post-processing

[0104] Same as Example 1.

[0105] Example 3

[0106] The preparation of the additive-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 additive)) adopts the following steps:

[0107] (1) Preparation of carrier precursor solution

[0108] Weigh 350 g of silica sol (SW-30 type), 115 g of powdered TiO2, 38.3 g of powdered ZrO2, and 38.3 g of powdered Al2O3 (mass ratio 3:1:1), add them to 550 g of deionized water, and add 120 g of ethanol to improve the dispersion effect. Place the resulting mixture in an ultrasonic cleaner and sonicate for 30 minutes to obtain a carrier precursor suspension.

[0109] (2) Preparation of metal sol-gel solution

[0110] Weigh 35.3 g of copper nitrate pentahydrate (Cu(NO3)2·5H2O) and 49.9 g of zinc nitrate tetrahydrate (Zn(NO3)2·4H2O), dissolve them in 350 g of deionized water at a Cu / Zn molar ratio of 2:3, and add 21 g of complexing agent sodium citrate. Transfer the resulting solution to a three-necked flask, heat and stir at 85°C, adjust the pH to 6.7 by adding ammonia dropwise, continue stirring for 1 hour, and then let it stand for 12 hours to age.

[0111] (3) Co-impregnation load

[0112] 220 mL of the carrier precursor suspension was added dropwise to 330 mL of the metal sol-gel solution, followed by 55 mL of 0.1 mol / L K₂CO₃ solution as an auxiliary agent to maintain a uniform distribution of the mixture. The mixture was stirred at 600 rpm for 2.5 hours at 65 °C. Subsequently, the mixture was transferred to a rotary evaporator, and excess solvent was removed under vacuum to obtain a semi-solid gel product.

[0113] (4) Shaping and drying

[0114] The resulting gel product was freeze-dried at -50°C for 22 hours, and then pressed into spherical particles with a particle size controlled between 50 and 150 μm. A gradient temperature drying method was used, first drying at 55°C for 5 hours, and then drying at 110°C for 14 hours to remove residual moisture.

[0115] (5) Calcination and activation

[0116] The dried catalyst precursor was placed in a tube furnace and calcined at 310°C for 2.5 hours under a nitrogen atmosphere at a rate of 5°C / min. Subsequently, the temperature was switched to a hydrogen / nitrogen mixture (10% hydrogen) and calcined at 520°C for 4 hours to reduce the metal oxide and form active centers.

[0117] (6) Post-processing

[0118] Same as Example 1.

[0119] Comparative Example 1

[0120] The catalyst was prepared according to the same steps and conditions as in Example 1, except that the promoter K2CO3 was not added, and a K-supported catalyst without promoter K was prepared.

[0121] Comparative Example 2

[0122] The catalyst was prepared according to the same steps and conditions as in Example 1, except that the promoter K2CO3 was replaced with 0.1 mol / L Na2CO3 to prepare a Cu-Zn / SiO2 supported catalyst containing Na promoter.

[0123] Comparative Example 3

[0124] The catalyst was prepared according to the same steps and conditions as in Example 1, except that the promoter K2CO3 was replaced with 0.1 mol / L Li2CO3 to prepare a Cu-Zn / SiO2 supported catalyst containing Li promoter.

[0125] Comparative Example 4

[0126] The difference from Example 1 is as follows:

[0127] (1) Preparation of carrier precursor suspension

[0128] Weigh 300 g of silica sol (SW-30 type, Qingdao Ocean Chemical Co., Ltd.) and 200 g of TiO2, 50 g of ZrO2, and 25 g of Al2O3 (mass ratio 8:2:1), add them to 500 g of deionized water, and add 100 g of ethanol to improve the dispersion effect. Place the resulting mixture in an ultrasonic cleaner and sonicate for 30 minutes to obtain a carrier precursor suspension.

[0129] The other steps are the same as in Example 1.

[0130] Comparative Example 5

[0131] The difference from Example 1 is as follows:

[0132] (2) Preparation of metal sol-gel solution

[0133] 50.4 g of copper nitrate pentahydrate (Cu(NO3)2·5H2O) and 9.5 g of zinc nitrate tetrahydrate (Zn(NO3)2·4H2O) were weighed and dissolved in 300 g of deionized water at a Cu / Zn molar ratio of 5:1. 18 g of sodium citrate complexing agent was added to stabilize the metal ions. The resulting solution was heated and stirred at 80℃, while ammonia was added dropwise to adjust the pH to 6.5–7.0. After stirring for 1 hour, the solution was allowed to stand for 12 hours to age, yielding a metal sol-gel solution.

[0134] The other steps are the same as in Example 1.

[0135] Comparative Example 6

[0136] The difference from Example 1 is as follows:

[0137] (5) Calcination and activation

[0138] Calcination: Under a nitrogen atmosphere, the temperature is increased to 350℃ at a rate of 5℃ / min and held for 2 hours.

[0139] Hydrogen activation: Switch to a hydrogen / nitrogen mixture (hydrogen component 10%), continue heating to 550℃, and calcine for 4 hours.

[0140] The other steps are the same as in Example 1.

[0141] Application Example 1

[0142] 200g of the catalyst obtained in the examples or comparative examples and 100g of catalyst additive SiO2 were packed into a hydrogenation reactor with a diameter of 40mm and a length of 1800mm. The temperature inside the reactor was maintained at 185℃, and the hydrogen pressure was maintained at 12.5 MPa. Hydrogen gas entered the hydrogenation reactor from the bottom, and methyl 2-hydroxyhexanoate was also entered from the bottom. The feed flow rate of methyl 2-hydroxyhexanoate was controlled at 0.2 mL / min, the hydrogen flow rate was 180 mL / min, and the hydrogen / catalyst volume hourly space velocity was 108 h⁻¹. -1 The products of the hydrogenation reaction flow out from the top of the hydrogenation reactor. After being cooled to 50°C by a condenser, the effluent is transferred to a distillation unit for post-processing. First, unreacted substances and low-boiling impurities are removed by steam distillation at 110-120°C to improve product purity. Subsequently, activated carbon or diatomaceous earth is used for adsorption purification to effectively remove pigments, trace by-products, and catalyst residues, ensuring product stability. Finally, rectification is carried out under low-pressure conditions of 130-180°C and 8-20 mmHg to separate high-boiling by-products, thereby increasing the purity of the final product to over 99.7%.

[0143] The feed conversion rates of methyl 2-hydroxyhexanoate and the selectivity of the resulting 1,2-hexanediol for different catalysts are shown in Table 1. Feed conversion rates and target alcohol selectivity were analyzed by gas chromatography (GC). First, feed and post-reaction product samples were collected, and the molar or mass concentrations of the feed and product were determined by GC. Feed conversion rates were obtained by calculating the change in feed concentration before and after the reaction, while the target alcohol selectivity was calculated by the concentration ratio of the target product to all products.

[0144] Table 1. Feed conversion and alcohol selectivity of different catalysts

[0145]

[0146] Table 1 shows that different catalysts have a significant impact on the feed conversion rate and alcohol selectivity. Example 1 (Cu-Zn / SiO2, K2CO3 promoter) performed best, achieving a feed conversion rate of 99.96% and an alcohol selectivity of 99.76%. In contrast, Comparative Example 1 (Cu-Zn / SiO2) without promoters showed poor performance, with a feed conversion rate of only 73.47% and an alcohol selectivity of 70.58%, indicating that the addition of promoters can significantly improve the catalyst activity and selectivity. Furthermore, different alkali metal promoters showed varying catalytic effects, with K2CO3 promoter generally performing better, while Na2CO3 and Li2CO3 promoters showed slightly inferior catalytic effects. This suggests that K2CO3 promoter plays an important role in this catalytic system, contributing to improved reaction efficiency and target product selectivity.

[0147] Application Example 2

[0148] Referring to Application Example 1, the additive-enhanced supported metal catalyst of Example 1 was used as the catalyst for the continuous hydrogenation reduction reaction. The feed rate was fixed at 0.2 mL / min, the hydrogen flow rate at 180 mL / min, and the bed pressure at 12.5 MPa. The core temperature of the reaction bed was controlled to vary from 160 to 200 °C. The feed conversion rate of methyl 2-hydroxyhexanoate and the selectivity of the resulting 1,2-hexanediol at different temperatures are shown in Table 2.

[0149] Table 2. Feed conversion rate and alcohol selectivity at different temperatures

[0150]

[0151] As shown in Table 2, the optimal core reaction temperature is 180-190℃. With decreasing temperature, the feed conversion rate gradually decreases, and the alcohol selectivity declines significantly. When the core reaction temperature is 180-185℃, the feed conversion rate reaches 99.92%, and the alcohol selectivity is 98.81%. After the core reaction temperature reaches 190℃, the alcohol selectivity decreases significantly with further increases in temperature.

[0152] Application Example 3

[0153] Referring to Application Example 1, the additive-enhanced supported metal catalyst of Example 1 was used as the catalyst for the continuous hydrogenation reduction reaction. The feed rate was fixed at 0.2 mL / min, the hydrogen flow rate at 180 mL / min, and the core reaction temperature at 180–185 °C. The bed pressure was controlled to vary from 6 to 15 MPa. The feed conversion rate of methyl 2-hydroxyhexanoate and the selectivity of the resulting 1,2-hexanediol under different pressures are shown in Table 3.

[0154] Table 3. Feed conversion rate and alcohol selectivity under different pressures

[0155]

[0156] As shown in Table 3, the feed conversion rate and alcohol selectivity gradually increase with increasing bed pressure. When the reaction bed pressure is 12-13 MPa, the feed conversion rate reaches 99.96% and the alcohol selectivity is 98.96%. Subsequently, with further increases in pressure, the feed conversion rate and alcohol selectivity do not change significantly.

[0157] Application Example 4

[0158] Referring to Application Example 1, the additive-enhanced supported metal catalyst of Example 1 was used as the catalyst for the continuous hydrogenation reduction reaction. The hydrogen flow rate was fixed at 180 mL / min, the core reaction temperature was 180~185℃, and the pressure was 12.5 MPa. The feed flow rate was controlled to vary from 0.10~0.50 mL / min. The feed conversion rate of methyl 2-hydroxyhexanoate and the selectivity of the resulting 1,2-hexanediol under different feed flow rates are shown in Table 4.

[0159] Table 4. Feed conversion rate and alcohol selectivity at different feed flow rates

[0160]

[0161] As shown in Table 4, when the feed flow rate is 0.20 mL / min, the feed conversion rate and alcohol selectivity are both high. Taking the feed flow rate of 0.20 mL / min as the threshold, the feed conversion rate decreases and the alcohol selectivity decreases as the feed flow rate increases. As the feed flow rate decreases, the feed conversion rate >99.94% remains stable, but the alcohol selectivity decreases.

[0162] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an additive-enhanced supported metal catalyst, characterized in that, Includes the following steps: The silica sol, TiO2, ZrO2, Al2O3, water, and alcohol dispersant were ultrasonically mixed to obtain a carrier precursor suspension; the mass ratio of TiO2, ZrO2, and Al2O3 was 2~4:1:

1. Soluble copper salt, soluble zinc salt, complexing agent and water are mixed, and the pH of the resulting mixture is adjusted to 6.5~7.

0. The mixture is then heated, stirred and allowed to stand for aging to obtain a metal sol-gel solution. The Cu / Zn molar ratio of the soluble copper salt and soluble zinc salt is 1~2:2~3. The carrier precursor suspension and K2CO3 solution were added to the metal sol-gel solution, and co-impregnation and loading were carried out under stirring. After removing excess solvent, a semi-solid gel product was obtained. The semi-solid gel product was subjected to freeze-drying, granulation, and gradient temperature drying in sequence to obtain a catalyst precursor. The catalyst precursor was calcined and activated with hydrogen to obtain an additive-enhanced supported metal catalyst; the calcination temperature was 280~320℃ and the holding time was 1.5~2.5h; the hydrogen activation temperature was 480~520℃ and the holding time was 3.5~4.5h.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the silica sol to TiO2 is 2~5:1; The mass of the alcohol dispersant is 10-30% of the mass of water.

3. The preparation method according to claim 1, characterized in that, The complexing agent is one or more of sodium citrate, ethylenediaminetetraacetic acid and tartaric acid; In the mixture of soluble copper salt, soluble zinc salt, complexing agent and water, the concentration of the complexing agent is 0.1~0.3 mol / L.

4. The preparation method according to claim 1 or 2, characterized in that, The heating and stirring temperature is 70~90℃, and the time is 0.5~1.5h; The static aging time is 10~14h.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the carrier precursor suspension, K2CO3 solution, and metal sol-gel solution is 1:(0.2~0.5):(1.5~2.0). The concentration of the K2CO3 solution is 0.05~0.2 mol / L; The temperature of the co-impregnation load is 50~70℃, and the time is 2~4h.

6. The preparation method according to claim 1, characterized in that, The gradient temperature drying process includes drying at 50-70℃ for 4-8 hours and drying at 100-140℃ for 10-14 hours.

7. The additive-enhanced supported metal catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The use of the additive-enhanced supported metal catalyst of claim 7 in the production of 1,2-hexanediol.

9. A method for continuous production of 1,2-hexanediol, characterized in that, Includes the following steps: Hydroxy fatty acid esters and hydrogen undergo a continuous hydrogenation reduction reaction in the presence of a catalyst to yield 1,2-hexanediol; The catalyst includes the additive-enhanced supported metal catalyst of claim 7.

10. The method according to claim 9, characterized in that, The continuous hydrogenation reduction reaction is carried out at a temperature of 140~200℃ and a pressure of 6~25MPa. The space velocity of the continuous hydrogenation reduction reaction is 50-200 h⁻¹. -1 ; The feed flow rate of the hydroxy fatty acid ester is 0.1~0.5 mL / min; The molar ratio of the hydroxy fatty acid ester to hydrogen is 1:40~200; The mass ratio of the hydroxy fatty acid ester to the catalyst is 100~600:1.

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