A catalyst for preparing 1,6-hexanediol by hydrogenation of dimethyl adipate, and a preparation method and application thereof

Abstract

This invention discloses a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol. The catalyst comprises an active component, a promoter component, and a support. The active component is Cu, the promoter component is Mg, the highly active reaction site is the interface between Cu and MgAl₂O₄, and the support is alumina. This invention also discloses its preparation method and applications. The high-performance Cu-based catalyst of this invention exhibits high activity and high selectivity under mild reaction conditions during the hydrogenation of dimethyl adipate. Furthermore, the construction of the microscopic spinel interface on the catalyst surface demonstrates extremely high stability; the catalyst remains stable for 800 hours without deactivation. The catalyst preparation method of this invention is simple, reproducible, and uses inexpensive raw materials. The catalyst exhibits high activity, excellent selectivity, and good stability, making it easy to scale up for production.

Description

Technical Field

[0001] This invention relates to the field of 1,6-hexanediol preparation technology, specifically to a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, its preparation method, and its application. Background Technology

[0002] 1,6-Hexanediol is an important diol with unique properties, holding a significant position in today's fine chemical raw material market. It can be mixed with a variety of organic chemicals in any proportion, is non-corrosive, and can derive a series of novel fine chemicals. It has increasingly wide applications in plasticizers, adhesives, polyurethanes, polyesters, coil coatings, and UV curing. In the materials field, 1,6-Hexanediol can improve the water and alkali resistance of materials, and enhance their elasticity and mechanical strength. It has wide applications in biodegradable polyesters, high-grade synthetic fibers, and high-end mechanical products such as automotive components. Therefore, 1,6-Hexanediol is a chemical product with enormous market potential.

[0003] Currently, the main methods for synthesizing 1,6-hexanediol include: hexynylene diol catalytic hydrogenation, epoxybutadiene method, hydroformylation, 1,2,6-hexanetriol catalytic conversion, 5-hydroxymethylfurfural catalytic conversion, adipic acid catalytic hydrogenation, sorbitol cracking, and dimethyl adipate catalytic hydrogenation. Among these, the hexynylene diol catalytic hydrogenation method has a long process route and high production cost; the epoxybutadiene method has too low a conversion rate and selectivity to meet production requirements; the hydroformylation method is technically difficult; the 1,2,6-hexanetriol catalytic conversion, 5-hydroxymethylfurfural catalytic conversion, and sorbitol cracking methods have low product yields and high costs; and the adipic acid catalytic hydrogenation method has high catalyst costs. Compared to the other methods, the dimethyl adipate catalytic hydrogenation method has many advantages, including fewer side reactions, high product selectivity, high product yield, ease of continuous production, and no equipment corrosion, making it a current research hotspot for the preparation of 1,6-hexanediol.

[0004] Patent CN102388009A discloses a hydrogenation catalyst for dimethyl adipate with a composition of CuO:ZnO:Al₂O₃ = 70:25:5 (weight ratio). The reaction pressure is as high as 22 MPa, indicating that the catalyst activity needs improvement. Patent CN101679157A discloses a method for hydrogenating alcohols in a batch reactor using a copper-zinc composite catalyst at 275°C and 25 MPa. This method involves harsh reaction conditions, increasing fixed equipment investment and operating costs. Patent CN110227470A discloses a CuZnAl catalyst prepared by precipitation, exhibiting excellent catalytic hydrogenation activity, but its stability is not disclosed.

[0005] Current research indicates that Cu-based catalysts are commonly used in the hydrogenation of dimethyl adipate. However, the activity, selectivity, and stability of Cu-based catalysts in this system require further improvement. Therefore, designing a catalytic system that can achieve high activity, high selectivity, and high stability for the hydrogenation of dimethyl adipate to 1,6-hexanediol under relatively mild conditions remains an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, its preparation method, and its application, which improves the catalytic hydrogenation activity, selectivity, and stability, thereby overcoming the shortcomings of the prior art.

[0007] The present invention adopts the following technical solution:

[0008] A catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, the catalyst comprising an active component, an auxiliary component, and a support, wherein the active component is Cu, the auxiliary component is Mg, the highly active reaction site is the interface formed by Cu and MgAl2O4, and the support is alumina; the active component, based on the mass of elemental Cu, comprises 15-45%; the auxiliary component, based on the mass of elemental Mg, comprises 10%-50%; and the remainder is the support;

[0009] The catalyst is prepared by the following steps:

[0010] (I) A certain amount of soluble salts of Cu, soluble salts of Mg, soluble salts of Al and polyhydroxy ligands are dissolved in a certain amount of water, and this solution is denoted as solution 1.

[0011] (II) A certain amount of Na2CO3 and NaOH are dissolved in a certain amount of water, wherein the molar ratio of Na2CO3 to NaOH is 1:2-3, and this solution is denoted as solution 2.

[0012] (III) Heat solutions 1 and 2 to 50-80℃ respectively. Under the condition of heat preservation, inject solutions 1 and 2 into a T-type mixer at the same flow rate of 0.5-3 ml / min using a horizontal flow pump. After mixing, the pH should be 8-10. Stir the resulting mixture vigorously at 400-500 rpm at 50-80℃ for 3-5 hours. Transfer the mixture to a sealed pressure-resistant hydrothermal reactor and heat it to 100-180℃ for 8-24 hours. Filter and wash the solid until the washed liquid is neutral. Place the washed solid in an oven at 100-180℃ and dry it for 10-14 hours.

[0013] (IV) The solid obtained in step (III) is crushed into small particles of less than 150 mesh and then calcined in a muffle furnace at 600-850℃ for 4-10 hours, with a calcination heating rate of 20-50℃ / min.

[0014] (V) The solid obtained in step (IV) is reduced and activated in a reduction and activation furnace at 300-450℃ for 10-12 hours. The reduction and activation heating rate is 20-50℃ / min. The reduction and activation gas is H2 or a mixture of H2 and inert gas, and the gas space velocity of the reduction and activation gas is 1000-3000 h⁻¹. -1 The reduction and activation pressure is atmospheric pressure; after reduction and activation, the pressure is lowered to room temperature, and a small amount of air is introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment is repeated 2-4 times, with an interval of 5-10 minutes between each passivation treatment, and nitrogen is continuously introduced during the process to obtain the catalyst.

[0015] Furthermore, the active component, based on the mass of Cu, has a content of 15-35%; the auxiliary component, based on the mass of Mg, has a content of 15%-45%; and the remainder is a carrier.

[0016] Further, in step (I), the soluble salt of Cu is one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate; the soluble salt of Mg is one or two of magnesium nitrate and magnesium chloride; the soluble salt of Al is one or two of aluminum nitrate and aluminum chloride; and the polyhydroxy ligand is glucose, citric acid, or salicylic acid. Further, in step (I), the molar ratio of the polyhydroxy ligand to Cu and Mg ions in solution 1 is 0.1-1:1, and the total molar concentration of the soluble salts of Cu, Mg, and Al is 1.5-2.5 mol / L; in step (II), the total molar concentration of Na₂CO₃ and NaOH in solution 2 is 4.5-5.5 mol / L; in step (III), the ratio of the total amount of soluble salts of Cu, Mg, and Al in solution 1 to the total amount of Na₂CO₃ and NaOH in solution 2 is 1:2.2-3.

[0017] A method for preparing a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol includes the following steps:

[0018] (I) A certain amount of soluble salts of Cu, soluble salts of Mg, soluble salts of Al and polyhydroxy ligands are dissolved in a certain amount of water, and this solution is denoted as solution 1.

[0019] (II) A certain amount of Na2CO3 and NaOH are dissolved in a certain amount of water, wherein the molar ratio of Na2CO3 to NaOH is 1:2-3, and this solution is denoted as solution 2.

[0020] (III) Heat solutions 1 and 2 to 50-80℃ respectively. Under the condition of heat preservation, inject solutions 1 and 2 into a T-type mixer at the same flow rate of 0.5-3 ml / min using a horizontal flow pump. After mixing, the pH should be 8-10. Stir the resulting mixture vigorously at 400-500 rpm at 50-80℃ for 3-5 hours. Transfer the mixture to a sealed pressure-resistant hydrothermal reactor and heat it to 100-180℃ for 8-24 hours. Filter and wash the solid until the washed liquid is neutral. Place the washed solid in an oven at 100-180℃ and dry it for 10-14 hours.

[0021] (IV) The solid obtained in step (III) is crushed into small particles of less than 150 mesh and then calcined in a muffle furnace at 600-850℃ for 4-10 hours, with a calcination heating rate of 20-50℃ / min.

[0022] (V) The solid obtained in step (IV) is reduced and activated in a reduction and activation furnace at 300-450℃ for 10-12 hours. The reduction and activation heating rate is 20-50℃ / min. The reduction and activation gas is H2 or a mixture of H2 and inert gas, and the gas space velocity of the reduction and activation gas is 1000-3000 h⁻¹. -1 The reduction and activation pressure is atmospheric pressure; after reduction and activation, the pressure is lowered to room temperature, and a small amount of air is introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment is repeated 2-4 times, with an interval of 5-10 minutes between each passivation treatment. Nitrogen gas is continuously introduced during the process to obtain the catalyst.

[0023] The catalyst comprises an active component, an auxiliary component, and a support. The active component is Cu, the auxiliary component is Mg, the highly active reaction site is the interface between Cu and MgAl2O4, and the support is alumina. The active component, based on the mass of Cu, has a content of 15-45%. The auxiliary component, based on the mass of Mg, has a content of 10%-50%. The remainder is the support.

[0024] Furthermore, the active component, based on the mass of Cu, has a content of 15-35%; the auxiliary component, based on the mass of Mg, has a content of 15%-45%; and the remainder is a carrier.

[0025] Further, in step (I), the soluble salt of Cu is one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate; the soluble salt of Mg is one or two of magnesium nitrate and magnesium chloride; the soluble salt of Al is one or two of aluminum nitrate and aluminum chloride; and the polyhydroxy ligand is one or more of glucose, citric acid, salicylic acid, and phytic acid.

[0026] Further, in step (I), the molar ratio of the polyhydroxy ligand in solution 1 to the two metal ions Cu and Mg is 0.1-1:1, and the total molar concentration of the soluble salts of Cu, Mg, and Al is 1.5-2.5 mol / L; in step (II), the total molar concentration of Na2CO3 and NaOH in solution 2 is 4.5-5.5 mol / L; in step (III), the ratio of the total amount of soluble salts of Cu, Mg, and Al in solution 1 to the total amount of Na2CO3 and NaOH in solution 2 is 1:2.2-3.

[0027] Application of the above catalyst in the selective hydrogenation of dimethyl adipate to prepare 1,6-hexanediol.

[0028] Further, the application includes the following steps: first, the catalyst is loaded into a packed bed reactor, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is reduced in H2 or an H2 / inert gas mixture under the following conditions: the gas space velocity of H2 or the H2 / inert gas mixture is 50-3000 h⁻¹. -1 The reduction pressure is 0.1-1.0 MPa, the reduction temperature is 250-350℃, the reduction heating rate is 0.1-10℃ / min, and the reduction time is 0.5-18 h. After the reduction is complete, the gas is switched to H2, and the reaction conditions are adjusted to the specified conditions. Dimethyl adipate or a mixture of 10-40 wt% dimethyl adipate and methanol is pumped in. The reaction conditions are: liquid hourly space velocity (LIHSV) of dimethyl adipate is 0.05-3.0 h⁻¹. -1 The molar ratio of H2 to dimethyl adipic acid is 5-300:1, the reaction temperature is 60-350℃, and the reaction pressure is 1.0-7.0MPa.

[0029] The beneficial effects of this invention are:

[0030] 1. The high-performance diester hydrogenation catalyst prepared in this invention activates H2 with highly dispersed Cu nanoparticles, enhances the adsorption and activation of ester groups through the interface composed of Cu and MgAl2O4, and utilizes the ultra-strong stability of MgAl2O4 to inhibit the sintering and growth of Cu nanoparticles during the reaction, thereby improving catalyst stability. In the catalyst preparation process, firstly, a polyhydroxy ligand is used to protect the Cu salt in the solution, preventing the formation of large particles during precipitation. Then, a T-type mixer is used to mix the metal salt solution and the alkaline solution. The T-type mixer allows for more thorough mixing of the solution, resulting in a more uniform and rapid reaction, while avoiding loss or waste. Further, the precipitate is dissolved and reconstructed under hydrothermal conditions to generate a multihydroxy organic ligand-doped hydrotalcite precursor. Subsequently, a highly dispersed Cu nanoparticle and MgAl2O4 phase is synthesized through rapid high-temperature calcination and in vitro reduction activation, constructing a high-performance catalyst precursor. Finally, in-situ reduction is used to construct an interface composed of Cu and MgAl2O4 at local locations to further enhance the catalyst's hydrogenation activity and stability. A spinel-encapsulated highly dispersed copper interface is constructed through a two-step reduction process. Highly dispersed Cu and the interface between Cu and MgAl2O4 not only promote the adsorption and activation of dimethyl adipic acid and H2 reactants, but also significantly improve the stability of the catalyst.

[0031] 2. The high-performance Cu-based catalyst of this invention exhibits high activity and selectivity under mild reaction conditions during the hydrogenation reaction of dimethyl adipate. Furthermore, the microscopic spinel interface on the catalyst surface demonstrates extremely high stability, remaining stable for 800 hours without deactivation. The catalyst preparation method of this invention is simple, reproducible, and uses inexpensive raw materials. The catalyst exhibits high activity, excellent selectivity, and good stability, making it easy to scale up for production. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a T-type mixer; a and b are the inlet fluid branch pipes, through which the liquid is transported, and c represents the outlet pipe, which flows out of the mixer.

[0033] Figure 2 This is a SEM image and elemental analysis diagram of the catalyst in Example 1.

[0034] Figure 3 This is a TEM image of the catalyst from Example 1.

[0035] Figure 4 This is the XRD pattern of the catalyst in Example 1.

[0036] Figure 5 This is a performance stability test graph of the catalyst in Example 1 when the product is 1,6-hexanediol. Detailed Implementation

[0037] The present invention will be further explained below with reference to embodiments and accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] Example 1

[0039] Dissolve 7.6 g copper nitrate trihydrate, 22.4 g magnesium nitrate hexahydrate, 33.1 g aluminum nitrate nonahydrate, and 4.0 g glucose in 100 mL of deionized water, and label this solution 1. Dissolve 12.6 g Na₂CO₃ and 14.3 g NaOH in 100 mL of deionized water, and label this solution 2. Heat solutions 1 and 2 separately to 65 °C. Under these conditions, use a horizontal flow pump to inject solutions 1 and 2 into a T-type mixer (e.g., [unclear]) at a flow rate of 2 mL / min. Figure 1 As shown below (the same applies below), after mixing, the pH was 9.5. The resulting mixture was vigorously stirred at 500 rpm for 3 hours in a beaker at 65℃. It was then transferred to a sealed pressure-resistant hydrothermal reactor (Shanghai Yanzheng Experimental Instrument Co., Ltd. hydrothermal reactor (YZHR-200-E)) and heated to 100℃ for 10 hours. The solid was filtered and washed until the washed liquid was neutral. The washed solid was then placed in an oven at 120℃ and dried for 12 hours. The resulting solid was crushed into particles smaller than 150 mesh and calcined in a muffle furnace at 620℃ for 5 hours at a calcination heating rate of 20℃ / min. The resulting solid was then reduced and activated in a reduction and activation furnace at 300℃ for 10 hours at a reduction and activation heating rate of 20℃ / min. The reduction and activation gas was H2 with a gas space velocity of 1500 h⁻¹. -1 The reduction and activation pressure was atmospheric pressure; after reduction and activation, the pressure was lowered to room temperature, and a small amount of air (about 40 ml) was introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment was repeated three times, with a 10-minute interval between each passivation treatment, during which nitrogen gas was continuously introduced to obtain the catalyst. The obtained catalyst was named 1-Cu / MgAlO.

[0040] The catalyst 1-Cu / MgAlO prepared in this embodiment, such as Figure 2-4 As shown, Figure 2 This shows that the active components Cu, Mg, and Al in the catalyst are uniformly distributed and tightly bonded on the catalyst surface. Figure 3 The catalyst surface shows that the Cu nanoparticles are uniformly distributed and small in size; Figure 4 This indicates that the catalyst surface simultaneously possesses highly dispersed Cu and MgAl2O4 species.

[0041] Take 1.0 g of the 1-Cu / MgAlO catalyst particles crushed to below 150 mesh and pack them into a packed bed reactor. Fill the entire reaction tube with quartz sand and reduce the catalyst. The reducing gas is an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 1500 h⁻¹. -1The reduction pressure was 0.3 MPa, the reduction temperature was 300℃, the reduction heating rate was 1℃ / min, and the reduction time was 4 h. After the reduction was completed, the gas was switched to H2, and the reaction conditions were adjusted to the specified conditions. Dimethyl adipate was pumped in using a high-pressure plunger pump, and the reaction conditions were: liquid hourly space velocity (LISH) of dimethyl adipate was 0.2 h⁻¹. -1 The molar ratio of H2 to dimethyl adipate was 60:1, the reaction temperature was 220℃, and the reaction pressure was 3.0 MPa. The conversion rate of dimethyl adipate was 100%, and the selectivity for 1,6-hexanediol was 98.8%.

[0042] Example 2

[0043] Dissolve 11.4 g of copper nitrate trihydrate, 22.4 g of magnesium nitrate hexahydrate, 25.6 g of aluminum nitrate nonahydrate, and 4.0 g of glucose in 100 mL of deionized water; this solution is labeled as solution 1. Dissolve 11.9 g of Na₂CO₃ and 13.4 g of NaOH in 100 mL of deionized water; this solution is labeled as solution 2. Solutions 1 and 2 were heated to 65°C and, under the holding condition, injected into a T-type mixer at a flow rate of 2 mL / min using a horizontal flow pump. After mixing, the pH was 9.5. The resulting mixture was then vigorously stirred at 500 rpm for 3 hours in a beaker at 65°C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (Shanghai Yanzheng Experimental Instrument Co., Ltd., hydrothermal reactor (YZHR-200-E)) and heated to 100°C for 10 hours. The solid was filtered and washed until the liquid was neutral. The washed solid was then dried in an oven at 120°C for 12 hours. The resulting solid was crushed into particles smaller than 150 mesh and calcined in a muffle furnace at 620°C for 5 hours at a heating rate of 20°C / min. The resulting solid was then reduced and activated in a reduction and activation furnace at 300°C for 10 hours at a heating rate of 20°C / min. The reducing and activation gas was H2 with a gas hourly space velocity (H2) of 1500 h⁻¹. -1 The reduction and activation pressure was atmospheric pressure. After reduction and activation, the pressure was lowered to room temperature, and a small amount of air (about 40 ml) was introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment was repeated three times, with a 10-minute interval between each passivation treatment, during which nitrogen gas was continuously introduced to obtain the catalyst. The obtained catalyst was named 2-Cu / MgAlO.

[0044] Take 1.0 g of the 2-Cu / MgAlO catalyst particles crushed to below 150 mesh and pack them into a packed bed reactor. Fill the entire reaction tube with quartz sand and reduce the catalyst. The reducing gas is an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 1500 h⁻¹. -1The reduction pressure was 0.3 MPa, the reduction temperature was 300℃, the reduction heating rate was 1℃ / min, and the reduction time was 4 h. After the reduction was completed, the gas was switched to H2, and the reaction conditions were adjusted to the specified conditions. Dimethyl adipate was pumped in using a high-pressure plunger pump, and the reaction conditions were: liquid hourly space velocity (LISH) of dimethyl adipate was 0.2 h⁻¹. -1 The molar ratio of H2 to dimethyl adipate was 60:1, the reaction temperature was 220℃, and the reaction pressure was 3.0 MPa. The conversion rate of dimethyl adipate was 100%, and the selectivity for 1,6-hexanediol was 98.0%.

[0045] Example 3

[0046] Dissolve 7.6g copper nitrate trihydrate, 22.4g magnesium nitrate hexahydrate, 33.1g aluminum nitrate nonahydrate, and 4.0g citric acid in 100mL of deionized water; this solution is labeled as solution 1. Dissolve 12.6g Na₂CO₃ and 14.3g NaOH in 100mL of deionized water; this solution is labeled as solution 2. Solutions 1 and 2 were heated to 65°C and, under the holding condition, injected into a T-type mixer at a flow rate of 2 mL / min using a horizontal flow pump. After mixing, the pH was 9.5. The resulting mixture was then vigorously stirred at 500 rpm for 3 hours in a beaker at 65°C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (Shanghai Yanzheng Experimental Instrument Co., Ltd., hydrothermal reactor (YZHR-200-E)) and heated to 100°C for 10 hours. The solid was filtered and washed until the liquid was neutral. The washed solid was then dried in an oven at 120°C for 12 hours. The resulting solid was crushed into particles smaller than 150 mesh and calcined in a muffle furnace at 620°C for 5 hours at a heating rate of 20°C / min. The resulting solid was then reduced and activated in a reduction and activation furnace at 300°C for 10 hours at a heating rate of 20°C / min. The reducing and activation gas was H2 with a gas hourly space velocity (H2) of 1500 h⁻¹. -1 The reduction and activation pressure was atmospheric pressure. After reduction and activation, the pressure was lowered to room temperature, and a small amount of air (about 40 ml) was introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment was repeated three times, with a 10-minute interval between each passivation treatment, during which nitrogen gas was continuously introduced to obtain the catalyst. The obtained catalyst was named 3-Cu / MgAlO.

[0047] Take 1.0 g of the 3-Cu / MgAlO catalyst particles crushed to below 150 mesh and pack them into a packed bed reactor. Fill the entire reaction tube with quartz sand and reduce the catalyst. The reducing gas is an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 1500 h⁻¹. -1The reduction pressure was 0.3 MPa, the reduction temperature was 300℃, the reduction heating rate was 1℃ / min, and the reduction time was 4 h. After the reduction was completed, the gas was switched to H2, and the reaction conditions were adjusted to the specified conditions. Dimethyl adipate was pumped in using a high-pressure plunger pump, and the reaction conditions were: liquid hourly space velocity (LISH) of dimethyl adipate was 0.2 h⁻¹. -1 The molar ratio of H2 to dimethyl adipate was 60:1, the reaction temperature was 220℃, and the reaction pressure was 3.0 MPa. The conversion rate of dimethyl adipate was 100%, and the selectivity for 1,6-hexanediol was 98.5%.

[0048] Example 4

[0049] Dissolve 7.6g copper nitrate trihydrate, 22.4g magnesium nitrate hexahydrate, 33.1g aluminum nitrate nonahydrate, and 4.0g salicylic acid in 100mL of deionized water, and label this solution 1. Dissolve 12.6g Na₂CO₃ and 14.3g NaOH in 100mL of deionized water, and label this solution 2. Solutions 1 and 2 were heated to 65°C and, under the holding condition, injected into a T-type mixer at a flow rate of 2 mL / min using a horizontal flow pump. After mixing, the pH was 9.5. The resulting mixture was then vigorously stirred at 500 rpm for 3 hours in a beaker at 65°C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (Shanghai Yanzheng Experimental Instrument Co., Ltd., hydrothermal reactor (YZHR-200-E)) and heated to 100°C for 10 hours. The solid was filtered and washed until the liquid was neutral. The washed solid was then dried in an oven at 120°C for 12 hours. The resulting solid was crushed into particles smaller than 150 mesh and calcined in a muffle furnace at 620°C for 5 hours at a heating rate of 20°C / min. The resulting solid was then reduced and activated in a reduction and activation furnace at 300°C for 10 hours at a heating rate of 20°C / min. The reducing and activation gas was H2 with a gas hourly space velocity (H2) of 1500 h⁻¹. -1 The reduction and activation pressure was atmospheric pressure. After reduction and activation, the pressure was lowered to room temperature, and a small amount of air (about 40 ml) was introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment was repeated three times, with a 10-minute interval between each passivation treatment, during which nitrogen gas was continuously introduced to obtain the catalyst. The obtained catalyst was named 4-Cu / MgAlO.

[0050] 1.0 g of the 4-Cu / MgAlO catalyst, crushed to below 150 mesh, was loaded into a packed bed reactor. The entire reaction tube was filled with quartz sand. The catalyst was then reduced using a H2 / N2 mixture with a H2 content of 10% v / v and a gas space velocity of 1500 h⁻¹. -1The reduction pressure was 0.3 MPa, the reduction temperature was 300℃, the reduction heating rate was 1℃ / min, and the reduction time was 4 h. After the reduction was completed, the gas was switched to H2, and the reaction conditions were adjusted to the specified conditions. Dimethyl adipate was pumped in using a high-pressure plunger pump, and the reaction conditions were: liquid hourly space velocity (LISH) of dimethyl adipate was 0.2 h⁻¹. -1 The molar ratio of H2 to dimethyl adipate was 60:1, the reaction temperature was 220℃, and the reaction pressure was 3.0 MPa. The conversion rate of dimethyl adipate was 100%, and the selectivity for 1,6-hexanediol was 98.2%.

[0051] Example 5

[0052] The stability test of the catalyst 1-Cu / MgAlO from Example 1 for the hydrogenation of dimethyl adipic acid to 1,6-hexanediol was conducted. The experiment showed that under the same reduction and reaction conditions as in Example 1, catalyst performance analysis indicated no significant deactivation of the catalyst after 800 hours of reaction. Figure 5 As shown in the figure, the blue arrow represents the conversion rate of dimethyl adipate, and the red arrow represents the selectivity of 1,6-hexanediol. This indicates that the catalyst has excellent stability when the product is 1,6-hexanediol.

[0053] Comparative Example 1

[0054] The R1-Cu / MgAlO catalyst was prepared using a traditional co-impregnation method. First, the MgAlO support was synthesized in-house. The specific steps are as follows: 28.0 g of magnesium nitrate hexahydrate, 41.4 g of aluminum nitrate nonahydrate, and 4.0 g of glucose were dissolved in 100 mL of deionized water, designated as solution 1. 13.4 g of Na₂CO₃ and 15.2 g of NaOH were dissolved in 100 mL of deionized water, designated as solution 2. Solutions 1 and 2 were heated to 65°C and, under the same holding conditions, injected into a T-type mixer at a flow rate of 2 mL / min using a horizontal flow pump. After mixing, the pH was 9.5. The resulting mixture was then vigorously stirred at 500 rpm for 3 hours in a beaker at 65°C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (Shanghai Yanzheng Experimental Instrument Co., Ltd., hydrothermal reactor (YZHR-200-E)) and heated to 100°C for 10 hours. The solid was filtered and washed until the liquid was neutral. The washed solid was then dried in an oven at 120°C for 12 hours. The resulting solid was then crushed into particles smaller than 150 mesh and calcined in a muffle furnace at 620°C. The calcination process was carried out for 5 hours at a heating rate of 20℃ / min to obtain a white solid MgAlO support. Then, metallic Cu was loaded onto it. The specific steps were as follows: 3.4 g of copper nitrate trihydrate was dissolved in 3 ml of deionized water, followed by the addition of 3 g of the prepared MgAlO support (below 150 mesh). The mixture was stirred evenly, air-dried under natural conditions, and then dried in an oven at 120℃ for 5 hours. It was then calcined in a muffle furnace at 620℃ for 5 hours at a heating rate of 20℃ / min. The resulting solid was then reduced and activated in a reduction and activation furnace at 300℃ for 10 hours at a heating rate of 20℃ / min. The reduction and activation gas was H2 with a gas space velocity of 1500 h⁻¹. -1 The reduction and activation pressure was atmospheric pressure. After reduction and activation, the pressure was lowered to room temperature, and a small amount of air (approximately 40 ml) was introduced under a nitrogen atmosphere for passivation. This passivation process was repeated three times, with a 10-minute interval between each passivation, during which nitrogen gas was continuously introduced to obtain the catalyst. The obtained catalyst was named R1-Cu / MgAlO. Catalytic performance was tested under the reduction and reaction conditions of Example 1. The conversion rate of dimethyl adipate was 37%, and the selectivity for 1,6-hexanediol was 30%.

[0055] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, characterized in that, The catalyst comprises an active component, an auxiliary component, and a support. The active component is Cu, the auxiliary component is Mg, the highly active reaction site is the interface between Cu and MgAl2O4, and the support is alumina. The active component, based on the mass of Cu, has a content of 15-45%; the auxiliary component, based on the mass of Mg, has a content of 10%-50%; and the remainder is the support. The catalyst is prepared by the following steps: (I) A certain amount of soluble salts of Cu, soluble salts of Mg, soluble salts of Al and polyhydroxy ligands are dissolved in a certain amount of water, and this solution is denoted as solution 1. (II) A certain amount of Na2CO3 and NaOH are dissolved in a certain amount of water, wherein the molar ratio of Na2CO3 to NaOH is 1:2-3, and this solution is denoted as solution 2. (III) Heat solutions 1 and 2 to 50-80℃ respectively. Under the condition of heat preservation, inject solutions 1 and 2 into a T-type mixer at the same flow rate of 0.5-3 ml / min using a horizontal flow pump. After mixing, the pH should be 8-10. The resulting mixture should be vigorously stirred at 400-500 rpm at 50-80℃ for 3-5 hours. Transfer it to a sealed pressure-resistant hydrothermal reactor and heat it to 100-180℃ for 8-24 hours. Filter and wash the solid until the washed liquid is neutral. Place the washed solid in an oven at 100-180℃ and dry for 10-14 hours. (IV) The solid obtained in step (III) is crushed into small particles of less than 150 mesh and then calcined in a muffle furnace at 600-850℃ for 4-10 hours, with a calcination heating rate of 20-50℃ / min. (V) The solid obtained in step (IV) is reduced and activated in a reduction and activation furnace at 300-450℃ for 10-12 hours. The reduction and activation heating rate is 20-50℃ / min. The reduction and activation gas is H2 or a mixture of H2 and inert gas, and the gas space velocity of the reduction and activation gas is 1000-3000 h⁻¹. -1 The reduction and activation pressure is atmospheric pressure; after reduction and activation, the pressure is lowered to room temperature, and a small amount of air is introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment is repeated 2-4 times, with an interval of 5-10 minutes between each passivation treatment, and nitrogen is continuously introduced during the process to obtain the catalyst.

2. The catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 1, characterized in that, The active component, based on the mass of Cu, has a content of 15-35%; the auxiliary component, based on the mass of Mg, has a content of 15%-45%; the remainder is a carrier.

3. The catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 1, characterized in that, In step (I), the soluble salt of Cu is one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate; the soluble salt of Mg is one or two of magnesium nitrate and magnesium chloride; the soluble salt of Al is one or two of aluminum nitrate and aluminum chloride; and the polyhydroxy ligand is one or more of glucose, citric acid, salicylic acid, and phytic acid.

4. The catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 1, characterized in that, In step (I), the molar ratio of the polyhydroxy ligand in solution 1 to the two metal ions Cu and Mg is 0.1-1:1, and the total molar concentration of the soluble salts of Cu, Mg, and Al is 1.5-2.5 mol / L; in step (II), the total molar concentration of Na2CO3 and NaOH in solution 2 is 4.5-5.5 mol / L; in step (III), the ratio of the total amount of soluble salts of Cu, Mg, and Al in solution 1 to the total amount of Na2CO3 and NaOH in solution 2 is 1:2.2-3.

5. A method for preparing a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol, characterized in that, Includes the following steps: (I) A certain amount of soluble salts of Cu, soluble salts of Mg, soluble salts of Al and polyhydroxy ligands are dissolved in a certain amount of water, and this solution is denoted as solution 1. (II) A certain amount of Na2CO3 and NaOH are dissolved in a certain amount of water, wherein the molar ratio of Na2CO3 to NaOH is 1:2-3, and this solution is denoted as solution 2. (III) Heat solutions 1 and 2 to 50-80℃ respectively. Under the condition of heat preservation, inject solutions 1 and 2 into a T-type mixer at the same flow rate of 0.5-3 ml / min using a horizontal flow pump. After mixing, the pH should be 8-10. The resulting mixture should be vigorously stirred at 400-500 rpm at 50-80℃ for 3-5 hours. Transfer it to a sealed pressure-resistant hydrothermal reactor and heat it to 100-180℃ for 8-24 hours. Filter and wash the solid until the washed liquid is neutral. Place the washed solid in an oven at 100-180℃ and dry for 10-14 hours. (IV) The solid obtained in step (III) is crushed into small particles of less than 150 mesh and then calcined in a muffle furnace at 600-850℃ for 4-10 hours, with a calcination heating rate of 20-50℃ / min. (V) The solid obtained in step (IV) is reduced and activated in a reduction and activation furnace at 300-450℃ for 10-12 hours. The reduction and activation heating rate is 20-50℃ / min. The reduction and activation gas is H2 or a mixture of H2 and inert gas, and the gas space velocity of the reduction and activation gas is 1000-3000 h⁻¹. -1 The reduction and activation pressure is atmospheric pressure; after reduction and activation, the pressure is lowered to room temperature, and a small amount of air is introduced under a nitrogen atmosphere for passivation treatment. The passivation treatment is repeated 2-4 times, with an interval of 5-10 minutes between each passivation treatment. Nitrogen gas is continuously introduced during the process to obtain the catalyst. The catalyst comprises an active component, an auxiliary component, and a support. The active component is Cu, the auxiliary component is Mg, the highly active reaction site is the interface between Cu and MgAl2O4, and the support is alumina. The active component, based on the mass of Cu, has a content of 15-45%. The auxiliary component, based on the mass of Mg, has a content of 10%-50%. The remainder is the support.

6. The method for preparing a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 5, characterized in that, The active component, based on the mass of Cu, has a content of 15-35%; the auxiliary component, based on the mass of Mg, has a content of 15%-45%; the remainder is a carrier.

7. The method for preparing a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 5, characterized in that, In step (I), the soluble salt of Cu is one or more of copper chloride, copper sulfate, copper nitrate, and copper acetate; the soluble salt of Mg is one or two of magnesium nitrate and magnesium chloride; the soluble salt of Al is one or two of aluminum nitrate and aluminum chloride; and the polyhydroxy ligand is one or more of glucose, citric acid, salicylic acid, and phytic acid.

8. A method for preparing a catalyst for the hydrogenation of dimethyl adipate to 1,6-hexanediol according to claim 5, characterized in that, In step (I), the molar ratio of the polyhydroxy ligand in solution 1 to the two metal ions Cu and Mg is 0.1-1:1, and the total molar concentration of the soluble salts of Cu, Mg, and Al is 1.5-2.5 mol / L; in step (II), the total molar concentration of Na2CO3 and NaOH in solution 2 is 4.5-5.5 mol / L; in step (III), the ratio of the total amount of soluble salts of Cu, Mg, and Al in solution 1 to the total amount of Na2CO3 and NaOH in solution 2 is 1:2.2-3.

9. The use of the catalyst according to any one of claims 1-4 in the selective hydrogenation of dimethyl adipate to prepare 1,6-hexanediol.

10. The application according to claim 9, characterized in that, The application includes the following steps: First, the catalyst is loaded into a packed bed reactor, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is reduced in H2 or an H2 / inert gas mixture under the following conditions: the gas space velocity of H2 or the H2 / inert gas mixture is 50-3000 h⁻¹. -1 The reduction pressure is 0.1-1.0 MPa, the reduction temperature is 250-350℃, the reduction heating rate is 0.1-10℃ / min, and the reduction time is 0.5-18 h. After the reduction is complete, the gas is switched to H2, and the reaction conditions are adjusted to the specified conditions. Dimethyl adipate or a mixture of 10-40 wt% dimethyl adipate and methanol is pumped in. The reaction conditions are: liquid hourly space velocity (LIHSV) of dimethyl adipate is 0.05-3.0 h⁻¹. -1 The molar ratio of H2 to dimethyl adipic acid is 5-300:1, the reaction temperature is 60-350℃, and the reaction pressure is 1.0-7.0MPa.

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