Preparation method of copper-silicon catalyst for catalyzing hydrogenation of dimethyl oxalate to prepare ethylene glycol

Abstract

The invention provides a preparation method of a copper-silicon catalyst for catalyzing hydrogenation of dimethyl oxalate to prepare ethylene glycol. The method comprises the following steps: carrying out drying pretreatment on a carrier; the preparation method comprises the following steps: dissolving soluble copper salt and soluble metal salt used as an auxiliary agent in deionized water to obtain a precursor solution; and mixing the carrier with the precursor solution, adding an ammonia water solution, continuously stirring for a period of time, carrying out ion exchange, and carrying out ammonia distillation, washing, filtering, drying and roasting to obtain the copper-silicon catalyst. Through pretreatment of the carrier, the metal-carrier interaction on the surface of the carrier is changed, so that the copper-silicon catalyst obtains more high-activity Cu < + > in the hydrogen reduction process, and the hydrogenolysis capability and catalytic performance of the catalyst are improved; the copper-silicon catalyst prepared by the preparation method is used for catalyzing the reaction of preparing ethylene glycol by hydrogenation of dimethyl oxalate under the conditions of low temperature, low pressure and low hydrogen ester, and shows excellent catalytic performance and stability.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a method for preparing a copper silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol. Background Art

[0002] Ethylene glycol (EG) is a widely used basic chemical raw material, mainly used in the production of polyester, antifreeze, membranes, etc., and is also widely used in the pharmaceutical industry and other industries. In the past decade, the domestic demand growth rate has remained high, and the average growth rate of ethylene glycol consumption has exceeded 9.8%; as of 2020, the total demand has reached 19.293 million tons, and about 10.547 million tons of supply still rely on imports, with a self-sufficiency rate of only 45%. With the rapid development of the polyester industry, the demand for ethylene glycol will continue to increase.

[0003] The existing EG industrial production technology at home and abroad is mainly the direct hydration of ethylene oxide, that is, the oil-based ethylene glycol (OTEG) route. The technology of Shell and SD is the main one in China. As of 2018, the domestic market share of ethylene glycol produced by ethylene oxide accounted for 56%. This production process often requires a large amount of water to obtain higher EG selectivity, and it is highly dependent on petroleum resources, while my country's energy structure is characterized by more coal, less oil and less gas. Some new ethylene glycol production technologies have been developed at home and abroad. my country has taken the lead in the world in realizing the industrial production of coal-to-ethylene glycol (CO gas-phase catalytic synthesis of dimethyl oxalate and catalytic hydrogenation of dimethyl oxalate to synthesize ethylene glycol). The hydrogenation of dimethyl oxalate to prepare ethylene glycol is the key step in coal-to-ethylene glycol. The hydrogenation of dimethyl oxalate is a cascade reaction. The hydrogenation of dimethyl oxalate first obtains methyl glycolate, and methyl glycolate is further hydrogenated to obtain ethylene glycol, and ethylene glycol is deeply hydrogenated to obtain ethanol.

[0004] Since copper-silicon catalysts have good C=O / C–O bond selective hydrogenation activity and low cost, they are widely used in gas-phase ester hydrogenation reactions. At present, there is a consensus on the mechanism of action of copper-silicon catalysts in the hydrogenation reaction of dimethyl oxalate, namely, Cu + The weakly acidic and alkaline copper-silicon catalysts, especially the Cu / SiO2 prepared by the ammonia evaporation method, generally contain high levels of Cu + and Cu0 active specific surface area and suitable Cu + / Cu0 ratio, making it the preferred catalyst for hydrogenation of dimethyl oxalate to ethylene glycol.

[0005] The design of industrial catalysts must not only consider the activity and selectivity of the catalyst, but also the impact of the catalyst's stability and service life on the overall process economy. Usually, researchers build high-efficiency catalysts and increase the service life of catalysts by adding additives, morphology control, interface control, etc. These methods have improved the activity and stability of catalysts to a certain extent, but they still fail to fundamentally solve the problem of catalyst deactivation.

[0006] In the patent application of the inventor with the authorization announcement number CN11311768B, a high-humidity carrier is used, that is, the carrier is allowed to absorb moisture until the water content is 1% to 3% under constant temperature and humidity conditions of 20°C to 40°C and relative humidity of 50% to 80%, thereby obtaining a wet carrier for catalyst preparation. However, this high-humidity carrier has some problems in the reaction of hydrogenating dimethyl oxalate to prepare ethylene glycol, such as high hydrogen-ester ratio and poor catalyst stability.

[0007] In summary, if a copper-silicon catalyst with good catalytic activity under low temperature, low pressure and low hydrogen-ester ratio conditions is developed in the hydrogenation reaction of dimethyl oxalate, it will be of great significance to further improve the long-term stability of the copper-silicon catalyst and reduce the economic investment and operating costs in the application process. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing a copper silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol in view of the deficiencies of the prior art in the above-mentioned background technology. The copper silicon catalyst prepared by the method can efficiently catalyze the hydrogenation of dimethyl oxalate at low temperature, low pressure and during a long service life to obtain a higher dimethyl oxalate conversion rate and ethylene glycol selectivity.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol comprises: S1, pre-treating the carrier by drying; S2, dissolving a soluble copper salt and a soluble metal salt used as an additive in deionized water to obtain a precursor solution; S3, adding the dried carrier in S1 to the precursor solution of S2, and then adding a 25% to 28% ammonia aqueous solution at a rate of 1 to 5 mL / min, and then performing ion exchange at 20 to 70°C for 0.5h to 20h; S4, distilling ammonia to a pH value of 6 to 7 at 90° C. from the material after ion exchange in S3, washing and filtering, drying the obtained solid at 100 to 150° C. for 5 to 20 h, and then calcining at 300 to 700° C. for 4 to 8 h to obtain a copper silicon catalyst precursor; S5. The copper silicon catalyst precursor is reduced under certain hydrogen conditions to obtain a copper silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol.

[0011] As a preferred embodiment of the present invention, the drying pretreatment in S1 is to store the carrier for a long time under constant temperature and humidity conditions of -10 to 40°C and relative humidity of 2% to 30%.

[0012] As a preferred embodiment of the present invention, the drying pretreatment in S1 is to store the carrier under the condition of relative humidity of 30% to 80%, and then calcine at 400 to 800° C. for 4 to 8 hours.

[0013] As a preferred embodiment of the present invention, the carrier in S1 is silicon dioxide or other forms of pure silicon molecular sieves.

[0014] Preferably, the silicon dioxide is solid phase nano silicon dioxide, gas phase nano silicon dioxide, porous structure silicon dioxide or newly produced small particle size silica sol, and the pure silicon molecular sieve is MCM-41, SBA-15 or HZSM-5.

[0015] Preferably, the silicon dioxide is solid-phase nano-silicon dioxide and gas-phase nano-silicon dioxide with a particle size of 20 to 100 nm.

[0016] Preferably, the silicon dioxide is a newly produced small-particle silicon solution with a production storage time of 0 to 4 weeks and a particle size of 5 to 50 nm.

[0017] As a preferred embodiment of the present invention, the copper salt in S2 is at least one of copper nitrate, copper chloride, copper sulfate and copper acetate.

[0018] As a preferred embodiment of the present invention, the soluble metal salt used as an auxiliary agent in S2 includes but is not limited to metal salts of Cs, Be, Mg, Ca, Sr, Zn, La, and Ce.

[0019] Preferably, the usage ratio of the copper salt, the soluble metal salt used as an auxiliary agent, and deionized water described in S2 is (0.8-1.5) g: (0.0-50.2) g: 75 mL, and the usage of the copper salt and the soluble metal salt used as an auxiliary agent are both calculated as metal elements.

[0020] As a preferred embodiment of the present invention, the usage ratio of the carrier described in S3 to the copper salt, the soluble metal salt used as an auxiliary agent, deionized water and ammonia solution described in S2 is 3g: (0.8~1.5)g: (0.0~50.2)g: 75mL: (12~20)mL, and the usage of the copper salt and the soluble metal salt used as an auxiliary agent are both calculated as metal elements.

[0021] Preferably, in S3, force-enhanced stirring and / or ultrasonic dispersion are performed during the ion exchange process.

[0022] The present invention also provides an application of the copper silicon catalyst prepared by the above preparation method, wherein the copper silicon catalyst is used for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature and low pressure conditions, specifically comprising: The copper silicon catalyst precursor is placed in a fixed bed reactor, the hydrogen flow rate is set to 40 mL / min, the temperature is raised from room temperature to 280°C at a rate of 1.5°C / min, and the reduction is continued for 5 hours in a hydrogen atmosphere and under normal pressure. After the reduction, the copper silicon catalyst bed temperature is controlled at 160-170°C, and then the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen, the hydrogen space velocity is 30-300 mL / min, and the dimethyl oxalate is catalyzed at a pressure of 0.2-1 MPa and a reaction temperature of 160-170°C. The molar ratio of dimethyl oxalate to hydrogen in the hydrogenation reaction is 1:(30-150).

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention pre-dries the carrier. During the low-humidity storage of the carrier, the hydroxyl groups on the silicon surface spontaneously transform into isolated hydroxyl groups, or more isolated hydroxyl groups are exposed through high-temperature calcination and dehydration. By changing the storage environment and duration of the carrier or obtaining a dry carrier with low water content through high-temperature calcination, the relative content of isolated hydroxyl groups on the surface of the carrier is significantly increased. The hydroxyl group is the main functional group for ion exchange reaction with copper ions, thereby greatly improving the Cu obtained by ion exchange. + At the same time, the ammonia evaporation process produces a large amount of copper silicate, which can not only increase the amount of Cu + The content of copper particles is also improved, so that copper ions are well dispersed on the surface of the carrier; although the Cu-O-Si unit obtained by ion exchange is reduced + Relatively small, but the Cu obtained by ion exchange + The activity in the hydrogenation of dimethyl oxalate is much higher than that of Cu obtained by other methods. + ; Even if a small amount of Cu is obtained through ion exchange +It also greatly promotes the activity of the copper-silicon catalyst, so that the copper-silicon catalyst prepared by this method has the ability to efficiently catalyze the hydrogenation of dimethyl oxalate to ethylene glycol under low temperature, low pressure and low hydrogen-ester ratio conditions.

[0024] 2. In the copper-silicon catalyst prepared by the ammonia evaporation method of the present invention, the active site Cu + Derived from ion exchange and copper silicate, derived from Cu obtained by ion exchange phase reduction + It has higher activity, but the simple ion exchange method cannot meet the requirements of high-load catalyst preparation, so the ammonia distillation method is further used to increase the Cu + The content of hydroxyl groups on the surface of the specially treated silica carrier increases, which greatly improves the Cu obtained by ion exchange. + The amount of copper silicon catalyst prepared by this scheme has extremely high activity in the reaction of hydrogenating dimethyl oxalate to prepare ethylene glycol, further reducing the reaction temperature and pressure. The lower reaction temperature and pressure extend the service life of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 TEM image of the copper silicon catalyst in Example 3 of the present invention; Figure 2 This is a stability test diagram of the copper-silicon catalyst in Example 3 of the present invention; DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0027] This embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1. Store solid phase nano-silicon dioxide with a particle size of 50 nm in an environment of 0°C and a relative humidity of 2% to 10% for 2 months; S2, dissolving 3.8 g of copper nitrate trihydrate in 80 ml of distilled water to obtain a precursor solution; S3, adding 3g of the carrier obtained in S1 to the precursor solution obtained in S2, and then adding 14mL of ammonia solution with a mass fraction of 25% to 28% at a rate of 3mL / min, and then stirring at room temperature for 6h to perform ion exchange, during which force-enhanced stirring and ultrasonic dispersion are used for 2h; S4, distilling ammonia from the material after ion exchange in S3 at 90°C until the pH value is 6-7, then washing and filtering, drying the obtained solid at 100°C for 20h, and then calcining at 500°C for 5h to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0028] In this embodiment, the copper silicon catalyst generated in the fixed bed reactor is used to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under the conditions of low temperature, low pressure and low hydrogen-to-ester ratio. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 160°C and the pressure is 0.4 MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:120. Example 2

[0029] The present embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1. After storing solid-phase nano-silicon dioxide with a particle size of 50 nm in an environment of 30° C. and a relative humidity of 60% to 80% for 1 month, calcining at 700° C. for 5 hours; S2, dissolving 3.8 g of copper nitrate trihydrate in 80 ml of distilled water to obtain a precursor solution; S3, adding 3g of the carrier obtained in S1 to the precursor solution obtained in S2, and then adding 14mL of ammonia solution with a mass fraction of 25% to 28% at a rate of 2mL / min, and then stirring at room temperature for 6h to perform ion exchange, during which force-enhanced stirring and ultrasonic dispersion are used for 1h; S4, the material after ion exchange in S3 is evaporated with ammonia at a temperature of 90° C. until the pH value is 6-7, then washed and filtered, the obtained solid is dried at a temperature of 120° C. for 14 hours, and then calcined at a temperature of 500° C. for 5 hours to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0030] This embodiment uses a copper silicon catalyst generated on a fixed bed reactor to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature, low pressure and low hydrogen-to-ester ratio conditions. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 165°C and the pressure is 0.5 MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:90. Example 3

[0031] The present embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1, weighing 10g of silica sol with a particle size of 10nm and a silicon dioxide content of 30% which has been stored for 1 week after production as a carrier; S2, dissolving 3.8 g of copper nitrate trihydrate in 80 ml of distilled water to obtain a precursor solution; S3, adding the carrier obtained in S1 to the precursor solution obtained in S2, and then adding 14 mL of a 25% to 28% ammonia aqueous solution at a rate of 2 mL / min, and then stirring at room temperature for 4 hours to perform ion exchange, during which force-enhanced stirring is used; S4, the material after ion exchange in S3 is evaporated with ammonia at a temperature of 90° C. until the pH value is 6-7, then washed and filtered, the obtained solid is dried at a temperature of 120° C. for 14 hours, and then calcined at a temperature of 500° C. for 5 hours to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0032] In this embodiment, the copper silicon catalyst generated in the fixed bed reactor is used to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature, low pressure and low hydrogen-to-ester ratio conditions. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 165°C and the pressure is 0.5MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:80. Example 4

[0033] The present embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1. Weigh 10 g of silica sol with a particle size of 5 nm and a silicon dioxide content of 30% which has been stored for 1 week after production as a carrier.

[0034] S2, dissolving 3.8 g of copper nitrate trihydrate and 0.2 g of magnesium nitrate in 80 ml of distilled water to obtain a precursor solution; S3, adding the carrier obtained in S1 to the precursor solution obtained in S2, and then adding 15 mL of a 25% to 28% ammonia aqueous solution at a rate of 1 mL / min, and then stirring at room temperature for 4 hours, using a force-enhanced stirring process; S4, the material after ion exchange in S3 is evaporated with ammonia at a temperature of 90° C. to a pH value of 6 to 7, then washed and filtered, the obtained solid is dried at a temperature of 120° C. for 14 hours, and then calcined at a temperature of 450° C. for 5 hours to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0035] This embodiment uses a copper silicon catalyst generated on a fixed bed reactor to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature, low pressure and low hydrogen-to-ester ratio conditions. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 170°C and the pressure is 1 MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:50. Example 5

[0036] The present embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1. After storing the pure silicon analysis sieve MCM-41 in an environment of 25°C and a relative humidity of 60% to 80% for 1 month, calcining at 600°C for 8h; S2, dissolving 3.8 g of copper nitrate trihydrate in 80 ml of distilled water to obtain a precursor solution; S3, adding 3 g of the carrier obtained in S1 to the precursor solution obtained in S2, and then adding 14 mL of a 25% to 28% ammonia aqueous solution at a rate of 3 mL / min, and then stirring at room temperature for 6 h. During this process, amplified stirring and ultrasonic dispersion were used for 1 h; S4, the material after ion exchange in S3 is evaporated with ammonia at a temperature of 90° C. until the pH value is 6-7, then washed and filtered, the obtained solid is dried at a temperature of 120° C. for 14 hours, and then calcined at a temperature of 500° C. for 5 hours to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0037] This embodiment uses a copper silicon catalyst generated on a fixed bed reactor to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature, low pressure and low hydrogen-to-ester ratio conditions. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 165°C and the pressure is 0.8 MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:80. Example 6

[0038] The present embodiment provides a method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, and the specific steps are as follows: S1, pure silicon analysis sieve HZSM-5 was stored in an environment of 5°C and relative humidity of 30% to 80% for 3 months and then calcined at 700°C for 6h; S2. Dissolve 3.8 g of copper nitrate trihydrate / 0.2 g of nickel nitrate in 80 ml of distilled water to obtain a precursor solution.

[0039] S3, add 3g of the carrier obtained in S1 to the precursor solution obtained in S2, ultrasonically disperse for 1h, then add 14mL of ammonia solution with a mass fraction of 25% to 28% at a rate of 3mL / min, and then stir at room temperature for 6h, using amplified stirring during this process; S4, after the ion exchange of S3 is completed, ammonia is evaporated at a temperature of 90° C. until the pH value is 6-7, and then washed and filtered, the obtained solid is dried at a temperature of 120° C. for 14 hours, and then calcined at a temperature of 500° C. for 5 hours to obtain a copper silicon catalyst precursor; S5. Place the copper silicon catalyst precursor in a fixed bed reactor, set the hydrogen flow rate to 40 mL / min, increase the temperature from room temperature to 280°C at a rate of 1.5°C / min, and continue to reduce in a hydrogen atmosphere at normal pressure for 5 hours to obtain the copper silicon catalyst.

[0040] This embodiment uses a copper silicon catalyst generated on a fixed bed reactor to directly catalyze the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature, low pressure and low hydrogen-to-ester ratio conditions. Specifically, after the reduction is completed, the reaction temperature in the fixed bed reactor is set to 170°C and the pressure is 0.5 MPa. Then, the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen to enter the fixed bed reactor for hydrogenation reaction; the molar ratio of dimethyl oxalate to hydrogen is 1:60.

[0041] Catalytic performance test experiment After the copper silicon catalyst prepared in Examples 1 to 6 was run in the catalytic dimethyl oxalate hydrogenation reaction for 8 hours, the catalytic performance of the catalyst was tested under product stability conditions. The results are shown in Table 1, wherein DMO is dimethyl oxalate and MG is methyl glycolate.

[0042] Table 1 Catalytic performance of copper-silicon catalysts prepared in Examples 1 to 6 Example Reaction temperature℃ Reaction pressure MPa Hydrogen ester ratio (mol) DMO conversion rate % EG selectivity% Example 1 160 0.4 1：120 99.56 96.53 Example 2 165 0.5 1：90 99.38 96.47 Example 3 165 0.5 1：80 99.67 97.34 Example 4 170 1 1：50 99.83 97.43 Example 5 165 0.8 1：80 99.34 96.46 Example 6 170 0.5 1：60 99.78 96.96 Compared with patent CN113117686B, under the same reaction conditions, the catalytic results obtained are almost the same, but the required hydrogen is significantly reduced, and the base-hydrogen-ester ratio is significantly reduced. This situation has a very significant driving effect on industrial production in reducing energy consumption and operating costs.

[0043] Stability and life test experiments like Figure 1 The TEM image of the copper silicon catalyst of Example 3 is shown. The catalytic stability of the copper silicon catalyst of Example 3 in the hydrogenation of dimethyl oxalate to prepare ethylene glycol was tested. The results are shown in FIG. Figure 2 The copper-silicon catalyst activity of Example 3 did not show a significant decrease after running for 500 hours, while the catalyst life of patent CN113117686B was only 200 hours.

[0044] From Table 1 and Figure 2 It can be seen that in the dimethyl oxalate hydrogenation reaction, the conversion rate of dimethyl oxalate prepared by the copper silicon catalysts prepared in Examples 1-6 of the present invention is >99% and the ethylene glycol selectivity is >96% under low temperature, low pressure and relatively low hydrogen-ester ratio conditions, which indicates that the copper silicon catalysts prepared by the present invention have high catalytic activity under mild reaction conditions and good stability.

Claims

1. A method for preparing a copper-silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol, characterized in that: include: S1. Drying and pre-treating the carrier; the carrier is silicon dioxide or other forms of pure silicon molecular sieves; S2. Dissolving a soluble copper salt and a soluble metal salt for an auxiliary agent in deionized water to obtain a precursor solution; the copper salt is at least one of copper nitrate, copper chloride, copper sulfate, and copper acetate; the soluble metal salt for an auxiliary agent includes but is not limited to metal salts of Cs, Be, Mg, Ca, Sr, Zn, La, and Ce; S3, adding the dried carrier in S1 to the precursor solution of S2, and then adding a 25% to 28% ammonia aqueous solution at a rate of 1 to 5 mL / min, and then performing ion exchange at 20 to 70°C for 0.5h to 20h; S4, distilling ammonia to a pH value of 6 to 7 at 90° C. from the material after ion exchange in S3, washing and filtering, drying the obtained solid at 100 to 150° C. for 5 to 20 h, and then calcining at 300 to 700° C. for 4 to 8 h to obtain a copper silicon catalyst precursor; S5. The copper silicon catalyst precursor is reduced under certain hydrogen conditions to obtain a copper silicon catalyst for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol.

2. The preparation method according to claim 1, characterized in that: The drying pretreatment in S1 is to store the carrier for a long time under constant temperature and humidity conditions of -10 to 40° C. and relative humidity of 2% to 30%.

3. The preparation method according to claim 1, characterized in that: The drying pretreatment in S1 is to store the carrier under the condition of relative humidity of 30% to 80%, and then calcine at 400 to 800° C. for 4 to 8 hours.

4. The preparation method according to claim 1, characterized in that: The silicon dioxide is solid phase nano silicon dioxide, gas phase nano silicon dioxide, porous structure silicon dioxide or newly produced small particle size silica sol, and the pure silicon molecular sieve is MCM-41, SBA-15 or HZSM-5.

5. The preparation method according to claim 1, characterized in that: The silicon dioxide is solid phase nano silicon dioxide and / or gas phase nano silicon dioxide with a particle size of 20 to 100 nm.

6. The preparation method according to claim 1, characterized in that: The silicon dioxide is a newly produced small-particle silicon solution with a production storage time of 0 to 4 weeks and a particle size of 5 to 50 nm.

7. The preparation method according to claim 1, characterized in that: The usage ratio of the copper salt, the soluble metal salt used as an auxiliary agent, and the deionized water described in S2 is (0.8-1.5) g: (0.0-50.2) g: 75 mL, and the usage of the copper salt and the soluble metal salt used as an auxiliary agent are both calculated as simple metal.

8. The preparation method according to claim 1, characterized in that: The usage ratio of the carrier described in S3 to the copper salt, the soluble metal salt used as an auxiliary agent, deionized water and ammonia solution described in S2 is 3g: (0.8-1.5)g: (0.0-50.2)g: 75mL: (12-20)mL, and the usage of the copper salt and the soluble metal salt used as an auxiliary agent are both calculated as metal elements.

9. The preparation method according to claim 1, characterized in that: In S3, force-enhanced stirring and / or ultrasonic dispersion are performed during the ion exchange process.

10. Use of the copper silicon catalyst prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The copper silicon catalyst is used for catalyzing the hydrogenation of dimethyl oxalate to prepare ethylene glycol under low temperature and low pressure conditions, and specifically comprises: The copper silicon catalyst precursor is placed in a fixed bed reactor, the hydrogen flow rate is set to 40 mL / min, the temperature is raised from room temperature to 280°C at a rate of 1.5°C / min, and the reduction is continued for 5 hours in a hydrogen atmosphere and under normal pressure. After the reduction, the copper silicon catalyst bed temperature is controlled at 160-170°C, and then the methanol solution of dimethyl oxalate is vaporized and mixed with hydrogen, the hydrogen space velocity is 30-300 mL / min, and the dimethyl oxalate is catalyzed at a pressure of 0.2-1 MPa and a reaction temperature of 160-170°C. The molar ratio of dimethyl oxalate to hydrogen in the hydrogenation reaction is 1:(30-150).

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