Auxiliary agent enhanced supported metal catalyst, preparation method thereof and application in production of 1, 2-hexanediol

Abstract

The invention provides an assistant enhanced supported metal catalyst, a preparation method thereof and application of the assistant enhanced supported metal catalyst in production of 1, 2-hexanediol, and belongs to the technical field of organic synthesis. According to the invention, an assistant enhanced supported metal catalyst is prepared, and hydroxyalkanoate and hydrogen are subjected to a continuous hydrogenation reduction reaction under the action of the catalyst to obtain 1, 2-hexanediol. Compared with a traditional hexene route, the obtained product 1, 2-hexanediol has excellent purity, odor impurities in the 1, 2-hexanediol product can be removed, the odor of the 1, 2-hexanediol product is extremely low, and the 1, 2-hexanediol product can be used for high-grade cosmetics.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and in particular to an auxiliary agent-enhanced supported metal catalyst, a preparation method thereof, and application thereof in the production of 1,2-hexanediol. Background Art

[0002] 1,2-Hexanediol, also known as DL-1,2-hexanediol or DL-1,2-hexanediol, is a versatile organic compound widely used in various fields. As a chemical raw material, it is used in the preparation of polymer materials such as plastics, fibers, advanced coatings, advanced glues, and adhesives. It is also an organic synthesis intermediate, used to manufacture downstream products such as 1,2-hexanediol and amino alcohols. It also plays a vital role in the refrigeration, pharmaceutical, food, and cosmetics industries. In the pharmaceutical field, 1,2-hexanediol is used as a synthetic raw material. In the cosmetics industry, it acts as a humectant, solvent, and antimicrobial agent. In high-end cosmetics, it acts as a preservative and antiperspirant, adding deodorizing, antibacterial, and moisturizing properties.

[0003] The current research focus is on providing a cost-effective, safe, and feasible continuous production method for 1,2-hexanediol to address its high price. Currently, the most studied method uses 1-hexene as the starting material, and produces 1,2-hexanediol through two processes: epoxidation with an oxidant and hydrolysis. Existing technologies mostly use H2O2 as the oxidant to oxidize organic acids into peracids, which then catalyze the reaction with 1-hexene to produce 1,2-hexanediol and its formate ester, which is then hydrolyzed under alkaline conditions to obtain 1,2-hexanediol. However, the product after alkaline hydrolysis needs to undergo a series of processing steps, including neutralization, extraction, drying, and distillation, to obtain the target product. This results in low product yields and produces high-salt wastewater containing sodium formate. In addition, the control of substances such as peracids is extremely challenging. If not properly controlled, it may cause explosions, posing a serious threat to production safety. Market feedback indicates that 1,2-hexanediol, a product synthesized by epoxidation and hydrolysis of 1-hexene with an oxidant, has an unpleasant odor similar to that of traditional Chinese medicine 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 method used in industry is to perform multiple distillations to obtain a very high-purity product, typically reaching a purity level of 99.99%. However, this production method has significant losses and therefore low yields, which makes 1,2-hexanediol directly used in the cosmetics industry expensive.

[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 light of this, the present invention aims to provide an additive-enhanced supported metal catalyst, its preparation method, and its application in the production of 1,2-hexanediol. The present invention utilizes an additive-enhanced supported metal catalyst to produce 1,2-hexanediol via a hydrogenation reduction reaction, enabling the continuous production of low-odor, cosmetic-grade 1,2-hexanediol with a simple process and low cost.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing an additive-enhanced supported metal catalyst, comprising the following steps: Ultrasonic mixing of silica sol, TiO2, ZrO2, Al2O3, water and alcohol dispersant to obtain a carrier precursor suspension; A soluble copper salt, a soluble zinc salt, a complexing agent and water are mixed, the pH value of the resulting mixture is adjusted to 6.5-7.0, and heating and stirring and standing for aging are sequentially performed to obtain a metal sol-gel solution; Adding the support precursor suspension and K2CO3 solution to the metal sol-gel solution, performing co-impregnation loading under stirring, and removing excess solvent to obtain a semi-solid gel product; The semi-solid gel product is freeze-dried, granulated and dried in a gradient temperature-increasing manner to obtain a catalyst precursor; The catalyst precursor is calcined and hydrogen activated to obtain a promoter-enhanced supported metal catalyst.

[0008] Preferably, the mass ratio of TiO2, ZrO2, and Al2O3 is 2-4:1:1; 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.

[0009] Preferably, the Cu / Zn molar ratio of the soluble copper salt to the soluble zinc salt is 1-2:2-3; The complexing agent is one or more of sodium citrate, ethylenediaminetetraacetic acid and tartaric acid; In the mixed solution of the soluble copper salt, the soluble zinc salt, the complexing agent and water, the concentration of the complexing agent is 0.1-0.3 mol / L.

[0010] Preferably, the heating and stirring temperature is 70-90°C and the time is 0.5-1.5h; The static aging time is 10 to 14 hours.

[0011] Preferably, the volume ratio of the support 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 co-impregnation load is carried out at a temperature of 50-70° C. and for a time of 2-4 hours.

[0012] Preferably, the gradient temperature drying comprises drying at 50-70°C for 4-8 hours and drying at 100-140°C for 10-14 hours; The calcination temperature is 280-320°C and the holding time is 1.5-2.5h; The temperature of the hydrogen activation is 480-520° C., and the holding time is 3.5-4.5 hours.

[0013] The present invention provides an additive-enhanced supported metal catalyst prepared by the above preparation method.

[0014] The present invention provides the use of the above-mentioned auxiliary agent-enhanced supported metal catalyst in the production of 1,2-hexanediol.

[0015] The present invention provides a method for continuously producing 1,2-hexanediol, comprising the following steps: Hydroxy fatty acid ester and hydrogen undergo continuous hydrogenation reduction reaction under the action of catalyst to obtain 1,2-hexanediol; The catalyst includes the above-mentioned promoter-enhanced supported metal catalyst.

[0016] Preferably, the temperature of the continuous hydrogenation reduction reaction is 140-200° C. and the pressure is 6-25 MPa; The space velocity of the continuous hydrogenation reduction reaction is 50~200 h -1 ; The feed 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.

[0017] The invention provides a method for preparing an additive-enhanced supported metal catalyst. The method comprises the following steps: ultrasonically mixing silica sol, TiO2, ZrO2, Al2O3, water and an alcohol dispersant to obtain a support precursor suspension; mixing a soluble copper salt, a soluble zinc salt, a complexing agent and water, adjusting the pH value of the obtained mixed solution to 6.5-7.0, heating and stirring the mixed solution and allowing the mixed solution to stand for aging to obtain a metal sol-gel solution; adding the support precursor suspension and a K2CO3 solution to the metal sol-gel solution, co-impregnating and loading the mixed solution under stirring, and removing excess solvent to obtain a semi-solid gel product; freeze-drying, granulating and gradient drying the semi-solid gel product to obtain a catalyst precursor; and calcining and hydrogen-activating the catalyst precursor to obtain an additive-enhanced supported metal catalyst, i.e., a K-additive-enhanced Cu-Zn / SiO2 catalyst. The present invention uses SiO2 as a catalyst carrier. By introducing TiO2, ZrO2, and Al2O3 into the carrier, the structural stability of the carrier 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. By adding an alcohol dispersant, the dispersion effect can be improved. Specifically, the present invention adopts a sol-gel method combined with a co-impregnation method to prepare the catalyst, which can ensure that the Cu and Zn active components are evenly loaded on the SiO2 carrier, increase the specific surface area and pore structure controllability of the catalyst, thereby improving the catalytic activity and service life; and through roasting and hydrogen activation, a Cu 0 -Cu + Synergistic active centers. The present invention can avoid catalyst precursor particle shrinkage and structural damage by combining freeze-drying with gradient temperature drying; by introducing a K2CO3 additive (K additive), the K additive exists in the catalyst in the form of an alkali metal oxide or carbonate, which adjusts the surface alkalinity of the catalyst, improves the reducibility and catalytic activity of the Cu species, and inhibits the occurrence of side reactions, thereby achieving the effect of improving the activity and selectivity of the catalyst. In addition, the introduction of TiO2, ZrO2 and Al2O3 enhances the stability of the carrier and the metal anchoring effect, prevents the sintering and loss of Cu and Zn, and ultimately forms a catalyst system with stable structure and excellent activity. When the additive-enhanced supported metal catalyst provided by the present invention is used to produce 1,2-hexanediol, it has excellent reaction activity and selectivity, and the resulting by-products are extremely small. The resulting 1,2-hexanediol product has an extremely low odor, meeting the requirements of cosmetic-grade 1,2-hexanediol.

[0018] The present invention provides a method for the continuous production of 1,2-hexanediol. In this method, a hydroxy fatty acid ester and hydrogen undergo a continuous hydrogenation reduction reaction in the presence of the aforementioned catalyst to produce 1,2-hexanediol. Compared to the traditional hexene route, the present invention has the following notable features: minimal byproduct generation, excellent purity of the resulting 1,2-hexanediol product, and the removal of odorous impurities from the 1,2-hexanediol product, resulting in an extremely low odor, suitable for use in high-end cosmetics. The present invention successfully addresses the issues of 1,2-hexanediol purity and odor, offering a simple, low-cost, safe, and reliable process and 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 DESCRIPTION

[0019] The present invention provides a method for preparing an additive-enhanced supported metal catalyst, comprising the following steps: Ultrasonic mixing of silica sol, TiO2, ZrO2, Al2O3, water and alcohol dispersant to obtain a carrier precursor suspension; A soluble copper salt, a soluble zinc salt, a complexing agent and water are mixed, the pH value of the resulting mixture is adjusted to 6.5-7.0, and heating and stirring and standing for aging are sequentially performed to obtain a metal sol-gel solution; Adding the support precursor suspension and K2CO3 solution to the metal sol-gel solution, performing co-impregnation loading under stirring, and removing excess solvent to obtain a semi-solid gel product; The semi-solid gel product is freeze-dried, granulated and dried in a gradient temperature-increasing manner to obtain a catalyst precursor; The catalyst precursor is calcined and hydrogen activated to obtain a promoter-enhanced supported metal catalyst.

[0020] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0021] The present invention ultrasonically mixes silica sol, TiO2, ZrO2, Al2O3, water, and an alcohol dispersant to obtain a carrier precursor suspension. In the present invention, the TiO2, ZrO2, and Al2O3 are preferably in powder form, with a particle size of preferably 20 to 50 nm. In the present invention, 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, the present invention can improve the surface properties of the catalyst. In the present invention, improving the surface properties of the catalyst not only increases the metal dispersion and the number of active sites, but also optimizes the acid-base properties, enhances stability, and improves mass transfer efficiency, ultimately increasing the overall activity and selectivity of the catalyst.

[0022] In the present invention, the mass ratio of the silica sol to TiO2 is preferably 2 to 5:1, specifically 2:1, 3:1, 4:1 or 5:1. In the present invention, the water is preferably deionized water, and the mass ratio of the silica sol to water is preferably 1:3.

[0023] In the present invention, the alcohol dispersant is preferably ethanol. In the present invention, the mass of the alcohol dispersant is preferably 10-30% of the mass of water, specifically 10%, 15%, 20%, 25%, or 30%. The addition of the alcohol dispersant can improve the dispersion of TiO2, ZrO2, and Al2O3.

[0024] In the present 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.

[0025] The present invention comprises mixing a soluble copper salt, a soluble zinc salt, a complexing agent, and water, adjusting the pH value of the resulting mixture to 6.5-7.0, and sequentially performing heating and stirring and static aging to obtain a metal sol-gel solution. In the present 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 the present 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.

[0026] In the present 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 the present invention, the concentration of the complexing agent in the mixture of the soluble copper salt, soluble zinc salt, complexing agent, and water is preferably 0.1 to 0.3 mol / L, more preferably 0.2 mol / L. In the present invention, the complexing agent functions to stabilize metal ions, regulate precipitation rate, and optimize the structure of the metal oxide.

[0027] The present invention preferably uses K2CO3 to adjust the pH to 6.5-7.0. In the present invention, the heating and stirring temperature is preferably 70-90°C, more preferably 80°C, and the time is preferably 0.5-1.5 hours, more preferably 1 hour. The present invention can form a metal sol-gel system through the heating and stirring.

[0028] In the present invention, the temperature of the static aging is preferably room temperature, and the time is preferably 10 to 14 hours, more preferably 12 hours. The present invention obtains a uniform metal sol-gel structure through the static aging.

[0029] After obtaining the support precursor suspension and metal sol-gel solution, the present invention adds the support precursor suspension and K2CO3 solution to the metal sol-gel solution, performs co-impregnation loading under stirring, and removes excess solvent to obtain a semisolid gel product. In the present invention, the addition method is preferably dropwise addition. In the present invention, the volume ratio of the support 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. Using the K2CO3 solution as an additive in the present invention not only maintains a uniform distribution of the mixed solution, but also improves the activity and selectivity of the catalyst.

[0030] In the present invention, the stirring rate during the co-impregnation loading is preferably 300-800 rpm, more preferably 500 rpm; in the present invention, the temperature of the co-impregnation loading is preferably 50-70°C, more preferably 60°C, and the time is preferably 2-4h, more preferably 3h.

[0031] In the present invention, the method for removing excess solvent is preferably rotary evaporation, and the rotary evaporation is preferably performed under vacuum conditions.

[0032] After obtaining the semi-solid gel product, the present invention sequentially freeze-dries, granulates, and then 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 to -30°C, and the drying time is preferably 18 to 30 hours, more preferably 20 to 25 hours. The freeze-drying method can prevent particle shrinkage and structural damage to the catalyst.

[0033] In the present invention, the granulation is preferably pressing, and the shape of the particles obtained after the granulation is preferably flake, spherical or powdery, more preferably spherical particles, and the particle size of the particles is preferably 10-200 μm, more preferably 50-150 μm.

[0034] In the present invention, the gradient temperature drying preferably includes drying at 50-70° C. for 4-8 hours and drying at 100-140° C. for 10-14 hours. The present invention can avoid catalyst precursor particle shrinkage and structural damage through the gradient temperature drying.

[0035] After obtaining the catalyst precursor, the present invention calcines and hydrogen activates it to produce a promoter-enhanced supported metal catalyst. In the present invention, the calcination is preferably performed in a tube furnace, and the calcination atmosphere is preferably nitrogen. The calcination temperature is preferably 280-320°C, more preferably 300°C, and the holding time is preferably 1.5-2.5 hours, more preferably 1 hour. In the present invention, the heating rate to the calcination temperature is preferably 4-6°C / min, more preferably 5°C / min. By calcining at a lower temperature (280-320°C), the present invention can improve the dispersibility and catalytic performance of the active metals Cu and Zn.

[0036] In the present invention, the hydrogen activation atmosphere is preferably a mixture of hydrogen and nitrogen. The volume fraction of hydrogen in the hydrogen and nitrogen mixture is preferably 8-12%, more preferably 10%. In the present 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, the present invention can improve the dispersibility and catalytic performance of the catalyst active metals Cu and Zn.

[0037] After the hydrogen activation, the present invention preferably cools the obtained promoter-enhanced supported metal catalyst to room temperature, and the cooling is preferably performed in an inert atmosphere.

[0038] The present invention provides an additive-enhanced supported metal catalyst obtained by the above preparation method. The present invention adopts a sol-gel method combined with a co-impregnation loading technology to uniformly disperse Cu and Zn on a SiO2 carrier, and forms a Cu-rich supported metal catalyst by calcination and hydrogen activation. 0-Cu + The K additive, present in the form of an alkali metal oxide or carbonate, modulates the surface alkalinity of the catalyst, enhancing the reducibility and catalytic activity of the 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.

[0039] The present invention provides the use of the above-mentioned auxiliary agent-enhanced supported metal catalyst in the production of 1,2-hexanediol.

[0040] The present invention provides a method for continuously producing 1,2-hexanediol, comprising the following steps: Hydroxy fatty acid ester and hydrogen undergo continuous hydrogenation reduction reaction under the action of catalyst to obtain 1,2-hexanediol; The catalyst includes the above-mentioned promoter-enhanced supported metal catalyst.

[0041] In the present invention, the hydroxy fatty acid ester is preferably methyl 2-hydroxyhexanoate.

[0042] In the present 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 the present 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.

[0043] In the present invention, the feed flow rate of the hydroxy fatty acid ester is preferably 0.1 to 0.5 mL / min, more preferably 0.2 mL / min.

[0044] In the present invention, the temperature of the continuous hydrogenation reduction reaction is preferably 140-200°C, more preferably 160-190°C, and further preferably 185-190°C; the pressure of the continuous hydrogenation reduction reaction is preferably 6-25 MPa, more preferably 12-15 MPa. In the present invention, the space velocity of the continuous hydrogenation reduction reaction is preferably 50-200 h -1 , more preferably 100~120 h -1 .

[0045] In the present invention, after the hydrogenation reduction reaction, the present invention preferably performs post-treatment on the obtained hydrogenation reduction product, and the post-treatment preferably includes the following steps: The obtained hydrogenation reduction reaction product is subjected to steam distillation, adsorption purification and rectification.

[0046] In the present invention, the steam distillation temperature is preferably 110-120°C, and the time is preferably 2-6 hours, more preferably 3-5 hours. In the present invention, the adsorbent for the adsorption purification is preferably activated carbon and / or diatomaceous earth. In the present invention, the rectification temperature is preferably 130-180°C, and the pressure is preferably 8-20 mmHg.

[0047] The adjuvant-enhanced supported metal catalyst provided by the present invention, its preparation method and its application in the production of 1,2-hexanediol are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1 The preparation of the promoter-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 promoter)) was carried out by the following steps: (1) Preparation of carrier precursor solution Weigh 300 g of silica sol (SW-30, manufactured by Qingdao Ocean Chemical Co., Ltd.) along with 100 g of powdered TiO₂, 33.3 g of powdered ZrO₂, and 33.3 g of powdered Al₂O₃ (mass ratio 3:1:1) and add them to 500 g of deionized water. Add 100 g of ethanol to enhance dispersion. The resulting mixture is ultrasonically treated in an ultrasonic bath for 30 minutes to obtain a carrier precursor suspension.

[0049] (2) Preparation of metal sol-gel solution 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 and dissolved in 300 g of deionized water at a Cu / Zn molar ratio of 2:3. 18 g of sodium citrate, a complexing agent, was added to stabilize the metal ions. The resulting solution was transferred to a three-necked flask and heated with stirring at 80°C. Ammonia was added dropwise to adjust the pH to 6.5, simultaneously forming a metal sol-gel system. The solution was stirred for 1 hour and then aged for 12 hours.

[0050] (3) Co-impregnation loading 200 mL of the support precursor suspension was added dropwise to 300 mL of the metal sol-gel solution. 50 mL of a 0.1 mol / L K₂CO₃ solution was added as an additive to maintain uniform distribution of the mixture. The mixture was stirred at 60°C and 500 rpm for 3 hours. The mixture was then transferred to a rotary evaporator and the excess solvent was removed under vacuum to obtain a semisolid gel product.

[0051] (4) Molding and drying The resulting semisolid gel product was freeze-dried, granulated, and then dried in a gradient drying process to prepare a catalyst precursor. First, freeze-dried at -30°C for 25 hours to prevent particle shrinkage and damage to the catalyst structure. Subsequently, granulated by pressing, the resulting particles were spherical and had a particle size of 50-150μm. Finally, a gradient drying process was used, first at 50°C for 4 hours and then at 100°C for 14 hours, to ensure the structural stability of the catalyst precursor and prevent particle shrinkage and damage.

[0052] (5) Calcination and activation The dried product was placed in a tube furnace and gradually heated to 300°C at a rate of 5°C / min under a nitrogen atmosphere. The temperature was then maintained at 300°C for 2 hours to form a preliminary structure. The atmosphere was then switched to a hydrogen / nitrogen mixture (10% hydrogen volume fraction), and the temperature was further increased to 500°C and calcined for 4 hours to reduce the metal oxides and enhance the active sites.

[0053] (6) Post-processing After the calcined product is cooled to room temperature, it is sieved to obtain uniform catalyst particles, which are stored in a sealed container for future use.

[0054] Example 2 The preparation of the promoter-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 promoter)) was carried out by the following steps: (1) Preparation of carrier precursor solution Weigh 250 g of silica sol (SW-30), 85 g of powdered TiO₂, 28.3 g of powdered ZrO₂, and 28.3 g of powdered Al₂O₃ (mass ratio 3:1:1) and add them to 450 g of deionized water. 85 g of ethanol was added to improve dispersion. The resulting mixture was ultrasonically treated in an ultrasonic bath for 30 minutes to obtain a carrier precursor suspension.

[0055] (2) Preparation of metal sol-gel solution Weigh 25.1 g of copper nitrate pentahydrate (Cu(NO₃)₂·5H₂O) and 35.5 g of zinc nitrate tetrahydrate (Zn(NO₃)₂·4H₂O) and dissolve them in 250 g of deionized water at a Cu / Zn molar ratio of 2:3. Add 15 g of sodium citrate as a complexing agent. Transfer the resulting solution to a three-necked flask and heat with stirring at 75°C. Ammonia water was added dropwise to adjust the pH to 6.8. Stirring was continued for 1 hour, followed by aging for 12 hours.

[0056] (3) Co-impregnation loading 180 mL of the support precursor suspension was added dropwise to 270 mL of the metal sol-gel solution. Subsequently, 45 mL of a 0.1 mol / L KCO solution was added as an additive to maintain a uniform distribution of the mixture. The mixture was stirred at 500 rpm and 60°C for 3 hours. The mixture was then transferred to a rotary evaporator and the excess solvent was removed under vacuum to obtain a semisolid gel product.

[0057] (4) Molding and drying The resulting gel product was freeze-dried at -45°C for 24 hours and then pressed into sheets with a particle size of 50-150 μm. A gradient drying process was used, initially at 60°C for 6 hours and then at 120°C for 12 hours, to remove any residual moisture.

[0058] (5) Calcination and activation The dried catalyst precursor was placed in a tube furnace and heated at 5°C / min to 290°C under a nitrogen atmosphere for 2 hours. The mixture was then switched to a hydrogen / nitrogen mixture (10% hydrogen) and heated to 500°C for another 4 hours to reduce the metal oxides and form active centers.

[0059] (6) Post-processing Same as Example 1.

[0060] Example 3 The preparation of the promoter-enhanced supported metal catalyst (Cu-Zn / SiO2 (K2CO3 promoter)) was carried out by the following steps: (1) Preparation of carrier precursor solution Weigh 350 g of silica sol (SW-30), 115 g of powdered TiO₂, 38.3 g of powdered ZrO₂, and 38.3 g of powdered Al₂O₃ (mass ratio 3:1:1) and add them to 550 g of deionized water. 120 g of ethanol was added to improve dispersion. The resulting mixture was ultrasonically treated in an ultrasonic bath for 30 minutes to obtain a carrier precursor suspension.

[0061] (2) Preparation of metal sol-gel solution Weigh 35.3 g of copper nitrate pentahydrate (Cu(NO₃)₂·5H₂O) and 49.9 g of zinc nitrate tetrahydrate (Zn(NO₃)₂·4H₂O) and dissolve them in 350 g of deionized water at a Cu / Zn molar ratio of 2:3. Add 21 g of sodium citrate as a complexing agent. Transfer the resulting solution to a three-necked flask and heat with stirring at 85°C. Ammonia water was added dropwise to adjust the pH to 6.7. Stirring was continued for 1 hour, followed by aging for 12 hours.

[0062] (3) Co-impregnation loading 220 mL of the support precursor suspension was added dropwise to 330 mL of the metal sol-gel solution. Subsequently, 55 mL of a 0.1 mol / L KCO solution was added as an additive to maintain a uniform distribution of the mixture. The mixture was stirred at 600 rpm and 65°C for 2.5 hours. The mixture was then transferred to a rotary evaporator and the excess solvent was removed under vacuum to obtain a semisolid gel product.

[0063] (4) Molding and drying The resulting gel product was freeze-dried at -50°C for 22 hours and then pressed into spherical particles with a particle size of 50-150 μm. A gradient drying process was used, initially at 55°C for 5 hours and then at 110°C for 14 hours, to remove any residual moisture.

[0064] (5) Calcination and activation The dried catalyst precursor was placed in a tube furnace and heated at 5°C / min to 310°C under a nitrogen atmosphere for 2.5 hours. The mixture was then switched to a hydrogen / nitrogen mixture (10% hydrogen) and heated to 520°C for another 4 hours to reduce the metal oxides and form active centers.

[0065] (6) Post-processing Same as Example 1.

[0066] Comparative Example 1 The catalyst was prepared according to the same steps and conditions as in Example 1, except that the additive K2CO3 was not added, and a Cu-Zn / SiO2 supported catalyst without K additive was prepared.

[0067] Comparative Example 2 The catalyst was prepared according to the same steps and conditions as in Example 1, except that the auxiliary agent K2CO3 was replaced by 0.1 mol / L Na2CO3 to prepare a Cu-Zn / SiO2 supported catalyst containing Na as the auxiliary agent.

[0068] Comparative Example 3 The catalyst was prepared according to the same steps and conditions as in Example 1, except that the auxiliary agent K2CO3 was replaced by 0.1 mol / L Li2CO3 to prepare a Li-auxiliary Cu-Zn / SiO2 supported catalyst.

[0069] Comparative Example 4 The difference from Example 1 is: (1) Preparation of carrier precursor suspension Weigh 300 g of silica sol (SW-30, Qingdao Ocean Chemical Co., Ltd.) along with 200 g of TiO₂, 50 g of ZrO₂, and 25 g of Al₂O₃ (mass ratio 8:2:1) and add them to 500 g of deionized water. 100 g of ethanol was added to improve dispersion. The resulting mixture was ultrasonically treated in an ultrasonic bath for 30 minutes to obtain a carrier precursor suspension.

[0070] Other steps are the same as in Example 1.

[0071] Comparative Example 5 The difference from Example 1 is: (2) Preparation of metal sol-gel solution 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 was added as a complexing agent to stabilize the metal ions. The resulting solution was heated and stirred at 80°C. Ammonia was added dropwise to adjust the pH to 6.5–7.0. After stirring for 1 hour, the solution was allowed to age for 12 hours to obtain a metal sol-gel solution.

[0072] Other steps are the same as in Example 1.

[0073] Comparative Example 6 The difference from Example 1 is: (5) Calcination and activation Calcination: In a nitrogen atmosphere, heat up to 350°C at a rate of 5°C / min and keep at this temperature for 2 hours.

[0074] Hydrogen activation: switch to a hydrogen / nitrogen mixture (hydrogen volume fraction 10%), continue heating to 550°C, and calcine for 4 hours.

[0075] Other steps are the same as in Example 1.

[0076] Application Example 1 200 g of the catalyst obtained in the embodiment or comparative example and 100 g of the catalyst auxiliary material SiO2 were filled in a hydrogenation reactor with a diameter of 40 mm and a length of 1800 mm. The temperature in the reactor was maintained at 185° C., the hydrogen pressure was maintained at 12.5 MPa, hydrogen entered the hydrogenation reactor from the lower end, 2-hydroxyhexanoic acid methyl ester entered the hydrogenation reactor from the lower end, the feed flow rate of 2-hydroxyhexanoic acid methyl ester was controlled at 0.2 mL / min, the hydrogen flow rate was 180 mL / min, and the hydrogen / catalyst volume space velocity was 108 h -1The hydrogenation reaction product flows out of the upper end of the hydrogenation reactor, is cooled to 50°C in a condenser, and then transferred to a distillation unit for post-processing. First, unreacted products and low-boiling impurities are removed through steam distillation at 110-120°C to improve product purity. Subsequently, adsorption purification using activated carbon or diatomaceous earth effectively removes pigments, trace byproducts, and catalyst residues, ensuring product stability. Finally, rectification is carried out at 130-180°C and a low pressure of 8-20 mmHg to separate high-boiling byproducts, bringing the final product purity to over 99.7%.

[0077] Table 1 shows the feed conversion rates for methyl 2-hydroxyhexanoate and the selectivity for the resulting 1,2-hexanediol using different catalysts. The feed conversion rates and selectivity for the target alcohol were analyzed using gas chromatography (GC). First, samples of the feed and reaction product were collected, and the molar or mass concentrations of the feed and products were determined by GC. The feed conversion rate was calculated by calculating the change in feed concentration before and after the reaction, while the selectivity for the target alcohol was calculated by the concentration ratio of the target product to all products.

[0078] Table 1 Feedstock conversion and alcohol selectivity of different catalysts

[0079] Table 1 shows that different catalysts have a significant impact on feedstock conversion and alcohol selectivity. Example 1 (Cu-Zn / SiO2, K2CO3 promoter) performed best, achieving a feedstock conversion of 99.96% and an alcohol selectivity of 99.76%. In comparison, the unpromoted comparative example 1 (Cu-Zn / SiO2) catalyst performed poorly, achieving a feedstock conversion of only 73.47% and an alcohol selectivity of 70.58%, demonstrating that the addition of promoters significantly improved catalyst activity and selectivity. Furthermore, different alkali metal promoters exhibited varying catalytic effects, with K2CO3 promoter performing better overall, while Na2CO3 and Li2CO3 promoters were slightly less effective. This demonstrates that the K2CO3 promoter plays a significant role in this catalytic system, contributing to improved reaction efficiency and target product selectivity.

[0080] Application Example 2 Referring to Application Example 1, the promoter-enhanced supported metal catalyst of Example 1 was used as the catalyst for a continuous hydrogenation reduction reaction. The feed rate was fixed at 0.2 mL / min, the hydrogen flow rate was 180 mL / min, and the bed pressure was 12.5 MPa. The bed temperature was controlled to vary from 160°C to 200°C. The feed conversion of methyl 2-hydroxyhexanoate and the selectivity for 1,2-hexanediol obtained at different temperatures are shown in Table 2.

[0081] Table 2 Raw material conversion and alcohol selectivity at different temperatures

[0082] As can be seen from Table 2, the optimal bed core reaction temperature is 180-190°C. As the temperature decreases, the feedstock conversion rate gradually decreases and the alcohol selectivity decreases significantly. When the bed core reaction temperature is 180-185°C, the feedstock conversion rate reaches 99.92% and the alcohol selectivity is 98.81%. After the bed core reaction temperature reaches 190°C and gradually increases, the alcohol selectivity decreases significantly.

[0083] Application Example 3 Referring to Application Example 1, the promoter-enhanced supported metal catalyst of Example 1 was used as the catalyst for a continuous hydrogenation reduction reaction. The feedstock feed rate was fixed at 0.2 mL / min, the hydrogen flow rate was 180 mL / min, and the bed core reaction temperature was 180-185°C. The bed pressure was controlled to vary from 6 to 15 MPa. The feedstock conversion of methyl 2-hydroxyhexanoate and the selectivity for 1,2-hexanediol obtained at different pressures are shown in Table 3.

[0084] Table 3 Raw material conversion and alcohol selectivity at different pressures

[0085] As can be seen from Table 3, with increasing bed pressure, the feed conversion rate gradually increases, and the alcohol selectivity also increases. When the reaction bed pressure is 12-13 MPa, the feed conversion rate reaches 99.96% and the alcohol selectivity reaches 98.96%. With subsequent increases in pressure, the feed conversion rate and alcohol selectivity do not change much.

[0086] Application Example 4 Referring to Application Example 1, the promoter-enhanced supported metal catalyst of Example 1 was used as the catalyst for a continuous hydrogenation reduction reaction. The hydrogen flow rate was fixed at 180 mL / min, the bed temperature was 180-185°C, and the pressure was 12.5 MPa. The feedstock flow rate was controlled to vary from 0.10 to 0.50 mL / min. The feedstock conversion of methyl 2-hydroxyhexanoate and the selectivity for 1,2-hexanediol obtained at different feedstock flow rates are shown in Table 4.

[0087] Table 4 Raw material conversion and alcohol selectivity at different raw material flow rates

[0088] Table 4 shows that when the feed rate is 0.20 mL / min, the feed conversion rate and alcohol selectivity are high. Taking the feed rate of 0.20 mL / min as the node, the feed conversion rate decreases with increasing feed rate, and the alcohol selectivity decreases. As the feed rate decreases, the feed conversion rate remains stable at >99.94%, while the alcohol selectivity decreases.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an additive-enhanced supported metal catalyst, characterized in that: The following steps are involved: Ultrasonic mixing of silica sol, TiO2, ZrO2, Al2O3, water and alcohol dispersant to obtain a carrier precursor suspension; A soluble copper salt, a soluble zinc salt, a complexing agent and water are mixed, the pH value of the resulting mixture is adjusted to 6.5-7.0, and heating and stirring and standing for aging are sequentially performed to obtain a metal sol-gel solution; Adding the support precursor suspension and K2CO3 solution to the metal sol-gel solution, performing co-impregnation loading under stirring, and removing excess solvent to obtain a semi-solid gel product; The semi-solid gel product is freeze-dried, granulated and dried in a gradient temperature-increasing manner to obtain a catalyst precursor; The catalyst precursor is calcined and hydrogen activated to obtain a promoter-enhanced supported metal catalyst.

2. The preparation method according to claim 1, characterized in that The mass ratio of TiO2, ZrO2, and Al2O3 is 2-4:1:1; 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 Cu / Zn molar ratio of the soluble copper salt and the soluble zinc salt is 1-2:2-3; The complexing agent is one or more of sodium citrate, ethylenediaminetetraacetic acid and tartaric acid; In the mixed solution of the soluble copper salt, the soluble zinc salt, the 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°C and the time is 0.5-1.5h; The static aging time is 10 to 14 hours.

5. The preparation method according to claim 1, characterized in that The volume ratio of the support 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 co-impregnation load is carried out at a temperature of 50-70° C. and for a time of 2-4 hours.

6. The preparation method according to claim 1, characterized in that The gradient temperature drying includes drying at 50-70°C for 4-8 hours and drying at 100-140°C for 10-14 hours; The calcination temperature is 280-320°C and the holding time is 1.5-2.5h; The temperature of the hydrogen activation is 480-520° C., and the holding time is 3.5-4.5 hours.

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

8. Use of the promoter-enhanced supported metal catalyst according to claim 7 in the production of 1,2-hexanediol.

9. A method for continuous production of 1,2-hexanediol, characterized in that: The following steps are involved: Hydroxy fatty acid ester and hydrogen undergo continuous hydrogenation reduction reaction under the action of catalyst to obtain 1,2-hexanediol; The catalyst comprises the promoter-enhanced supported metal catalyst according to claim 7.

10. The method according to claim 9, characterized in that The temperature of the continuous hydrogenation reduction reaction is 140-200°C and the pressure is 6-25 MPa; The space velocity of the continuous hydrogenation reduction reaction is 50~200 h -1 ; The feed 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.

Images