A catalyst for preparing methyl acetate or ethanol by hydrolyzing dimethyl oxalate and a preparation method and application thereof

Abstract

The application discloses a catalyst for preparing methyl acetate or ethanol by hydrogenation of dimethyl oxalate and a preparation method thereof. The catalyst comprises an active component, an auxiliary component and a carrier. The active component is a single substance or an oxide of Cu, the auxiliary component is a single substance or an oxide of W, the high active site is a Cu-W alloy interface and single Cu and W metals, and the carrier is one or more than two of silicon dioxide, aluminum oxide, zirconium oxide, zinc oxide, magnesium oxide and cerium oxide. The copper-tungsten alloy catalyst provided by the application has the advantages of structural stability, high mechanical strength, good heat conduction performance, high substrate conversion rate and high product selectivity. The preparation method is simple in steps, easy in raw material acquisition, low in cost, green in pollution, good in preparation repeatability and easy in scale production. The catalyst has extremely high stability and catalytic activity in the reaction of preparing methyl acetate or ethanol by hydrogenation of dimethyl oxalate, high ethanol or methyl acetate yield and high active component utilization rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthesis of methyl acetate or ethanol, and particularly relates to a catalyst for regulating selective hydrogenation of dimethyl oxalate to prepare methyl acetate or ethanol, a preparation method and application thereof. BACKGROUND

[0002] Methyl acetate (MA) is also known as methyl acetate, which is an organic solvent and chemical raw material commonly used in industry, and is widely used in paint and coating, textile, perfume, medicine and food industries. It is commonly used as an extractant for oil and fat, a fast-drying solvent for cellulose acetate, and high-purity methyl acetate can be used to synthesize acetic acid, anhydride, methyl acrylate, vinyl acetate, etc. In recent years, with the continuous development of C1 chemical industry, the demand for methyl acetate is increasing. Due to its certain properties similar to acetone, it is also used as a substitute for acetone. At the same time, methyl acetate is an important intermediate product of coal processing industry, and is an important raw material for carbonylation of acetic anhydride.

[0003] At present, the common preparation methods of methyl acetate mainly include methanol dehydrogenation synthesis, methanol carbonylation, methanol esterification and dimethyl ether carbonylation. Due to the source of raw materials and production process conditions, among these methods, the method of directly esterifying methyl acetate and acetic acid is the most common. The catalyst widely used in the direct esterification reaction of acetic acid and methyl alcohol is concentrated sulfuric acid. This strong acid catalyst has high catalytic performance, but it can also cause side reactions, reduce the selectivity of methyl acetate, and produce a large amount of waste acid and wastewater, making the separation of reaction products more difficult. In recent years, with the concept of green chemistry being deeply rooted in people's hearts, less energy consumption and less waste discharge in the production process have attracted more and more attention. The traditional preparation method is gradually difficult to meet the development requirements of the new era. Therefore, in recent years, the reaction of preparing methyl acetate from dimethyl oxalate hydrogenation has attracted people's attention. However, this reaction is a continuous and complex reaction. Dimethyl oxalate is first subjected to incomplete hydrogenation to obtain methyl glycolate, and then further hydrogenation to obtain ethylene glycol or methyl acetate. Deep hydrogenation can obtain ethanol. Since methyl acetate is easily hydrogenated to obtain ethanol, it is necessary to seek a new catalyst with high catalytic activity and selectivity and to explore the reaction conditions to obtain the intermediate product methyl acetate, which has become a hot research field.

[0004] Ethanol (EtOH) is an important chemical raw material and clean energy, widely used in solvent, disinfectant, food, fuel and other industries, also can be used to manufacture beverages, dyes, essence and ethanol gasoline, etc. Ethanol as a fuel without pollution, can be added to gasoline in a certain proportion, improve the octane number of gasoline, make ethanol gasoline combustion more fully, reduce the emission of CO, hydrocarbons and other pollutants, reduce air pollution, while can reduce the use of gasoline, reduce the dependence on oil resources in China, in line with the national conditions of China's more coal, less oil, poor gas, so the demand for ethanol in China also increased. Efficient synthesis of ethanol process attracts widespread attention of researchers.

[0005] The main methods of industrial production of ethanol are biological fermentation, ethylene hydration, synthesis gas, etc. Among them, biological fermentation is the most commonly used method for preparing ethanol. This method mainly uses corn, sugarcane and other food crops as raw materials to obtain ethanol by fermentation, but the price of food is high, and there may be a situation of competing with people for food, which is not conducive to the global food supply. In addition to fermentation, the preparation of ethanol by ethylene hydration requires a large amount of petroleum resources, and the cost of producing ethanol is high due to the high price of oil. The economic efficiency is not good. In addition, this method requires the use of concentrated sulfuric acid with strong corrosion, high equipment material requirements and high investment cost. In the economic environment of China, there is no obvious competitiveness. Direct synthesis of ethanol from synthesis gas, although this method requires fewer process steps, but the conversion rate of synthesis gas and the selectivity of ethanol are low, so the preparation of ethanol by this method needs to explore better catalysts to realize large-scale production. There are mainly three methods for the preparation of ethanol by indirect synthesis gas: 1. Synthesis gas is first made into methanol, methanol is carbonylated to obtain acetic acid, and acetic acid is further hydrogenated to obtain ethanol. This method will produce a lot of by-products such as acetaldehyde or ethyl acetate, and the catalyst used is generally a noble metal catalyst such as Pt, Pd, Rh, etc., which greatly increases the cost and is not conducive to large-scale industrial production. 2. Acetic acid is prepared from synthesis gas, and esterification is carried out to obtain methyl acetate, which is further hydrogenated to obtain ethanol. Researchers have done a lot of research on the catalyst for this reaction, and currently copper-based catalysts are mainly used, but the reaction temperature is high, and copper-based catalysts tend to agglomerate and sinter, leading to deactivation. 3. The technology of synthesis gas catalytic coupling to obtain dimethyl oxalate is basically mature, and dimethyl oxalate hydrogenation to prepare ethanol. Because dimethyl oxalate contains two ester functional groups, it is not easy to obtain alcohol hydroxyl group by hydrogenation, so it is also necessary to develop a catalyst with high conversion rate and high ethanol selectivity.

[0006] Patent CN101830776B reported a method for synthesizing ethanol, first using Pd-based catalyst to prepare dimethyl oxalate, and then using Cu-based catalyst for dimethyl oxalate hydrogenation to generate ethanol. In a fixed bed reactor, the selectivity of ethanol is up to 85%. Patent CN106563480A discloses a kind of molybdenum carbide catalyst for dimethyl oxalate hydrogenation to prepare methyl acetate and ethanol, and when the conversion rate of dimethyl oxalate is 100%, the selectivity of ethanol is up to 83%. The selectivity of methyl acetate is very low. In addition, there is no report on the stability of the catalyst in the patent.

[0007] Current research shows that Cu / SiO2 catalyst is commonly used in dimethyl oxalate hydrogenation. However, Cu / SiO2 catalyst shows poor selectivity and poor stability in dimethyl oxalate hydrogenation system. In addition, since methyl acetate can be easily further hydrogenated to prepare ethanol, there are few reports on the high selectivity of dimethyl oxalate hydrogenation to prepare methyl acetate. In the reaction of dimethyl oxalate hydrogenation to prepare ethanol, a variety of metal-modified copper-based catalysts are reported, but the overall selectivity of ethanol is low, and the reaction conditions are harsh. Therefore, how to design a catalytic system with high activity, high selectivity and high stability for dimethyl oxalate hydrogenation to prepare methyl acetate or ethanol under mild conditions is still a problem to be solved. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a catalyst for dimethyl oxalate hydrogenation to prepare methyl acetate or ethanol, a preparation method and application thereof. By adjusting the mass ratio of copper and tungsten, the catalyst is prepared by a specific method, and the reaction conditions are controlled to ensure high conversion rate of dimethyl oxalate and selective generation of methyl acetate or ethanol, so as to solve the problems of the prior art.

[0009] The present application first discloses a catalyst for dimethyl oxalate hydrogenation to prepare methyl acetate or ethanol, which comprises an active component, an auxiliary component and a carrier. The active component is elemental Cu or oxide, the auxiliary component is elemental W or oxide, the high active site is Cu-W alloy interface and single Cu and W metal, and the carrier is one or more than two of silicon dioxide, aluminum oxide, zirconium oxide, zinc oxide, magnesium oxide and cerium oxide.

[0010] The catalyst is prepared by the following steps:

[0011] (I) mixing soluble copper salt, deionized water, ammonia water and carrier to prepare a mixture, so that the pH of the mixture is 8-12;

[0012] (II) ultrasonic treatment of the mixture obtained in step (I) at room temperature for 3-5 h, and then aging at 25-45℃ with vigorous stirring at 1000-2000 rpm for 3-5 h;

[0013] (III) heating and evaporating the mixture treated in step (II) at 70-90℃ until the pH of the mixture is 6-7, and then putting it into a hydrothermal reactor to be treated at 120-180℃ for 3-8h;

[0014] (IV) filtering and washing the mixture treated in step (III) with deionized water to obtain a solid;

[0015] (V) drying the solid obtained in step (IV) at 120-150℃ for 6-24h, and then calcining it at 300-600℃ for 2-10h to obtain a Cu / support precursor; a solution of a soluble salt of W is atomized into micron-sized W salt droplets by an ultrasonic atomizer, and the micron-sized W salt droplets are adsorbed on the Cu / support precursor by electrostatic force between the Cu / support precursor and the micron-sized W salt droplets to obtain a loaded material;

[0016] (VI) naturally air-drying the loaded material obtained in step (V) for 24-48h to obtain a loaded solid;

[0017] (VII) drying the loaded solid obtained in step (VI) at 100-150℃ for 6-24h, and then calcining it at 300-650℃ for 2-12h to obtain a catalyst Cu-W / support.

[0018] Further, when the catalyst is used for selectively preparing methyl acetate, the content of the first active component is 1-30% by mass of Cu element; the content of the second active component is 5%-20% by mass of W element; and the rest is the support.

[0019] Further, when the catalyst is used for selectively preparing ethanol, the content of the first active component is 5-30% by mass of Cu element; the content of the second active component is 0.05%-3% by mass of W element; and the rest is the support.

[0020] Further, the soluble salt of copper in step (I) is one or two or more of copper nitrate, copper chloride, copper sulfate or copper acetate.

[0021] Further, the soluble salt of tungsten in step (V) is one or two or more of ammonium tungstate, ammonium metatungstate, sodium tungstate, cobalt tungstate or ferrous tungstate.

[0022] The application also discloses a preparation method of the aforementioned catalyst for preparing methyl acetate or ethanol from dimethyl oxalate by hydrogenation,

[0023] The preparation method comprises the following steps:

[0024] (I) mixing a soluble salt of copper, deionized water, ammonia water and a support to prepare a mixture, so that the pH of the mixture is 8-12;

[0025] (II) ultrasonic treatment of the mixture obtained in step (I) at room temperature for 3-5 h, followed by vigorous stirring at 1000-2000 rpm at 25-45℃ for 3-5 h;

[0026] (III) heating and evaporating the mixture treated in step (II) at 70-90℃ until the pH of the mixture is 6-7, and then placing it in a hydrothermal reactor and treating it at 120-180℃ for 3-8 h;

[0027] (IV) filtering and washing the mixture treated in step (III) with deionized water to obtain a solid;

[0028] (V) drying the solid obtained in step (IV) at 120-150℃ for 6-24 h, and then calcining it at 300-600℃ for 2-10 h to obtain a Cu / support precursor; atomizing a solution of a soluble salt of W into micron-sized W salt droplets by an ultrasonic atomizer, and adsorbing the micron-sized W salt droplets on the Cu / support precursor by electrostatic force between the two to obtain a loaded material;

[0029] (VI) naturally air-drying the loaded material obtained in step (V) for 24-48 h to obtain a loaded solid material;

[0030] (VII) drying the loaded solid material obtained in step (VI) at 100-150℃ for 6-24 h, and then calcining it at 300-650℃ for 2-12 h to obtain a catalyst Cu-W / support.

[0031] Further, the soluble salt of copper in step (I) is one or more of copper nitrate, copper chloride, copper sulfate, or copper acetate; and the soluble salt of tungsten in step (V) is one or more of ammonium tungstate, ammonium metatungstate, sodium tungstate, cobalt tungstate, or ferrous tungstate.

[0032] The application also discloses an application of the aforementioned catalyst in the hydrogenation of dimethyl oxalate to produce methyl acetate or ethanol,

[0033] In the production of methyl acetate, the catalyst is first loaded into a reaction tube, and then the entire reaction tube is filled with quartz sand; the catalyst is activated in hydrogen or a hydrogen-inert gas mixture before use; after the activation is completed, the specified reaction conditions are adjusted, dimethyl oxalate or a mixture of dimethyl oxalate and methyl alcohol solvent is pumped in, and the reaction conditions are as follows: the temperature is 120-350℃, the pressure is 0.3-6.0 MPa, the liquid hourly space velocity of dimethyl oxalate is 0.01-6.0 h -1 , and the molar ratio of hydrogen to dimethyl oxalate is 5:1-800:1.

[0034] In the preparation of ethanol, the catalyst is first filled in a reaction tube, then the whole reaction tube is filled with quartz sand, the catalyst is activated in hydrogen or hydrogen-inert gas mixture before use, after the activation is completed, the specified reaction conditions are adjusted, dimethyl oxalate or dimethyl oxalate and methanol solvent mixture is pumped in, and the reaction conditions are as follows: the temperature is 250-350℃, the pressure is 3.0-6.0Mpa, the liquid hourly space velocity of dimethyl oxalate is 0.01-2h -1 , the molar ratio of hydrogen to dimethyl oxalate is 400:1-800:1; the preferred reaction conditions for preparing methyl acetate are as follows: the temperature is 120-280℃, the pressure is 0.3-2.0Mpa, the liquid hourly space velocity of dimethyl oxalate is 2-6h -1 , the molar ratio of hydrogen to dimethyl oxalate is 5:1-300:1.

[0035] Further, the catalyst activation conditions are as follows: the pressure is 0.1-0.5MPa, the gas space velocity is 10-300h -1 , the activation temperature is 160-300℃, the heating rate is 0.1-20℃ / min, and the activation time is 0.5-8h.

[0036] The beneficial effects of the present application are as follows:

[0037] The bimetallic nanometer alloy heterogeneous catalyst prepared by the present application first uses ammonia to load the active component copper on the carrier, and through long-time vigorous stirring, the copper is uniformly distributed on the surface of the carrier; then the strong electric force between the micron-level mist droplets of ultrasonic atomization and the Cu / carrier precursor is used to uniformly disperse the second active component tungsten on the surface of the copper catalyst obtained in the previous step, and the second component tungsten is modified on the surface of the copper component to form a copper-tungsten alloy structure of the active component. Then, in the post-processing process such as calcination and reduction, the bimetallic alloy catalyst with a nano structure is formed in situ. The interface structure of the formed bimetallic alloy has better catalytic performance. In addition, due to the existence of the typical alloy structure, there is a strong electronic effect between the two metals in the catalyst and a strong interaction between the active component and the carrier, which can significantly improve the stability of the catalyst.

[0038] Compared with the traditional copper catalyst, (1) the activity of the catalyst and the selectivity of the target product can be improved: by adjusting the ratio of copper to tungsten, the selective generation of methyl acetate or ethanol from dimethyl oxalate hydrogenation is controlled, when the content of the second active component W is not less than 5%, the selectivity of methyl acetate can reach more than 70%, and when the content of the second active component W is not higher than 3%, the selectivity of ethanol can reach more than 90%; (2) the reaction of dimethyl oxalate hydrogenation to prepare methyl acetate or ethanol can be realized under relatively mild conditions; (3) the stability of the catalytic system is effectively improved, and the stability is ≥1000h.

[0039] In summary, the copper-tungsten alloy catalyst provided by the present application has the advantages of structural stability, high mechanical strength, good heat conduction performance, high substrate conversion rate and product selectivity, and the preparation method has the advantages of simple steps, easy-to-obtain raw materials, low cost, green and pollution-free, good preparation repeatability, and easy realization of large-scale production. In the reaction of catalyzing dimethyl oxalate to prepare methyl acetate or ethanol, the copper-tungsten alloy catalyst has extremely high stability and catalytic activity, high yield of ethanol or methyl acetate, and high utilization rate of active components. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is the ball difference electron microscope element analysis spectrum of the copper-tungsten catalyst of example 1, the upper left corner is the original electron microscope graph of the catalyst, and the rest are Cu element analysis graph, O element analysis graph and W element analysis graph;

[0041] Figure 2 is the physical adsorption curve of the copper-tungsten catalyst of example 1;

[0042] Figure 3 is the TEM graph of the copper-tungsten catalyst of example 1;

[0043] Figure 4a is the performance stability test graph of the copper-tungsten catalyst of example 1;

[0044] Figure 4b is the performance stability test graph of the copper-tungsten catalyst of example 2. DETAILED DESCRIPTION

[0045] The present application will be further explained in combination with examples. The following examples are only used to illustrate the present application, but not used to limit the implementation scope of the present application.

[0046] Example 1

[0047] A copper nitrate solution was prepared by dissolving 7.55 g of copper nitrate trihydrate in 100 mL of deionized water at room temperature. A certain amount of ammonia water and 7 g of silicon dioxide were added to the copper nitrate solution to make the pH 8-12, and the resulting mixture was ultrasonically treated at room temperature for 3 h, followed by vigorous stirring at 1000 rpm for 4 h at 35 °C. The temperature was then raised to 80 °C until the pH reached 7. The resulting mixture was placed in a hydrothermal reactor and treated at 120 °C for 3 h, then filtered and washed with deionized water to obtain a solid, which was then dried at 150 °C for 12 h and calcined at 450 °C for 5 h to obtain a Cu / SiO2 precursor. An ammonium metatungstate solution was prepared by dissolving 1.34 g of ammonium metatungstate in 50 mL of deionized water, which was atomized by an ultrasonic atomizer, and then mixed with the Cu / SiO2 precursor to adsorb and load the ammonium metatungstate component by strong electrostatic attraction between the two. The mixture was then left to stand at room temperature for 48 h to obtain a loaded solid. The loaded solid was then dried at 150 °C for 12 h, and then calcined at 550 °C for 4 h in a muffle furnace to obtain a catalyst 20Cu-10W / SiO2.

[0048] The catalyst 20Cu-10W / SiO2 prepared in this example, as shown in FIG. 1, Figures 1-3 Figure 1 shows that the Cu and W elements are uniformly distributed at the microscale, and the perfect fit of the Cu and W element mapping images indicates that the Cu and W are closely combined into an alloy phase at the nanoscale, which proves that it is a copper-tungsten nanometer alloy catalyst. Figure 2 shows that the catalyst has a large specific surface area (up to 394.8 m 2 / g) and exhibits a clear mesoporous structure distribution. Figure 3 shows that the active component nanoparticles on the surface of the catalyst are uniformly distributed, and the statistical particle size by TEM confirms that the copper-tungsten catalyst prepared is a nanometer catalyst.

[0049] The above catalyst 1.0 g was loaded into a fixed bed reaction tube, which was filled with quartz sand throughout the reaction tube, and the catalyst was reduced. The reduction gas was a H2 / Ar mixed gas with a H2 content of 5% v / v, the mixed gas gas space velocity was 150 h -1 , the reduction pressure was 0.5 MPa, the reduction temperature was 230 °C, the heating rate was 2 °C / min, and the reduction time was 2 h. After reduction, the gas was switched to H2, and the pressure was increased to 1.5 MPa. A 20% mass fraction of dimethyl oxalate (DMO) in methanol solution was pumped in using a flat pump, the DMO liquid space velocity was 1.0 h -1 , the molar ratio of H2 / DMO was 20:1, and the reaction temperature was 260 °C. The conversion of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 71.0%.

[0050] Example 2 ​

[0051] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7.95 g of silica were added to the copper nitrate solution to adjust the pH to 8-12. The resulting mixture was ultrasonically treated at room temperature for 3 h, followed by vigorous stirring at 1200 rpm for 3 h at 35 °C. The temperature was then raised to 90 °C until the pH reached 7. The resulting mixture was placed in a hydrothermal reactor and treated at 120 °C for 3 h, then filtered and washed with deionized water to obtain a solid. The solid was then dried at 150 °C for 24 h and calcined at 450 °C for 5 h. 0.067 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / SiO2 precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h to obtain the loaded solid. The loaded solid was then dried at 150 °C for 24 h. Then, the catalyst was calcined in a muffle furnace at 550°C for 4 hours to obtain the catalyst 20Cu-0.5W / SiO2.

[0052] 1.0 g of the above catalyst was loaded into a fixed-bed reaction tube, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with a H2 content of 5% v / v and a gas space velocity of 200 h⁻¹. -1 The reduction pressure was 0.5 MPa, the reduction temperature was 280℃, the heating rate was 5℃ / min, and the reduction time was 8 h. After reduction, the gas was switched to H2, the pressure was increased to 5.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump at a DMO liquid hourly space velocity (LISH) of 0.8 h⁻¹. -1 The molar ratio of H2 / DMO was 400:1, and the reaction temperature was 280℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 94.0%.

[0053] Example 3

[0054] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7.8 g of zinc oxide were added to the copper nitrate solution to adjust the pH to 8-12. The resulting mixture was ultrasonically treated at room temperature for 3 h, followed by vigorous stirring at 1500 rpm for 5 h at 45 °C. The temperature was then increased to 80 °C until the pH reached 7. The resulting mixture was placed in a hydrothermal reactor and treated at 150 °C for 3 h, then filtered and washed with deionized water to obtain a solid. The solid was then dried at 150 °C for 12 h and calcined at 450 °C for 5 h. 0.268 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / ZnO precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h to obtain the loaded solid. The loaded solid was then dried at 150 °C for 24 h. The catalyst 20Cu-2W / ZnO was then calcined in a muffle furnace at 550°C for 6 hours to obtain the catalyst.

[0055] 1.0 g of the above catalyst was loaded into a fixed-bed reaction tube, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with a H2 content of 5% v / v and a gas space velocity of 100 h⁻¹. -1 The reduction pressure was 0.5 MPa, the reduction temperature was 300℃, the heating rate was 10℃ / min, and the reduction time was 6 h. After reduction, the gas was switched to H2, the pressure was increased to 6.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump at a DMO liquid hourly space velocity (LISH) of 2.0 h⁻¹. -1 The molar ratio of H2 / DMO was 20:1, and the reaction temperature was 260℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 60.3%.

[0056] In this embodiment, all other conditions are the same, but the liquid hourly space velocity of DMO is 0.8 h⁻¹. -1 The molar ratio of H2 / DMO was 300:1, and the reaction temperature was 320℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 93.6%.

[0057] Example 4

[0058] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7.5 g of zirconium oxide were added to the copper nitrate solution to adjust the pH to 8-12. The resulting mixture was ultrasonically treated at room temperature for 3 h, followed by vigorous stirring at 1800 rpm for 3.5 h at 35 °C. The temperature was then increased to 90 °C until the pH reached 6.5. The resulting mixture was placed in a hydrothermal reactor and treated at 140 °C for 3 h, then filtered and washed with deionized water to obtain a solid. The solid was then dried at 150 °C for 12 h and calcined at 450 °C for 5 h. 0.67 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / ZrO2 precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h to obtain the loaded solid. The loaded solid was then dried at 150 °C for 8 h. Then, the catalyst was calcined in a muffle furnace at 550°C for 4 hours to obtain the catalyst 20Cu-5W / ZrO2.

[0059] 1.0 g of the above catalyst was loaded into a fixed-bed reaction tube, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with a H2 content of 5% v / v and a gas space velocity of 100 h⁻¹. -1 The reduction pressure was 0.5 MPa, the reduction temperature was 230 °C, the heating rate was 2 °C / min, and the reduction time was 2 h. After reduction, the gas was switched to H2, the pressure was increased to 4.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump. The liquid hourly space velocity (LISH) of the DMO was 2.5 h⁻¹. -1 The molar ratio of H2 / DMO was 30:1, the reaction temperature was 230℃, the conversion rate of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 70%.

[0060] In this embodiment, all other conditions are the same, but the liquid hourly space velocity of DMO is 0.8 h⁻¹. -1 The molar ratio of H2 / DMO was 350:1, and the reaction temperature was 310℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 71.2%.

[0061] Example 5

[0062] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7.8 g of cerium oxide were added to the copper nitrate solution to adjust the pH to 8-12. The resulting mixture was ultrasonically treated at room temperature for 5 h, followed by vigorous stirring at 1300 rpm for 5 h at 35 °C. The temperature was then raised to 80 °C until the pH reached 7. The resulting mixture was placed in a hydrothermal reactor and treated at 140 °C for 3 h, then filtered and washed with deionized water to obtain a solid. The solid was then dried at 130 °C for 12 h and calcined at 450 °C for 5 h. 0.268 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / CeO2 precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h to obtain the loaded solid. The loaded solid was then dried at 150 °C for 12 h. Then, the catalyst was calcined in a muffle furnace at 550°C for 4 hours to obtain the catalyst 20Cu-2W / CeO2.

[0063] 1.0 g of the above catalyst was loaded into a fixed-bed reaction tube, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with an H2 content of 5% v / v and a gas space velocity of 50 h⁻¹. -1 The reduction pressure was 0.5 MPa, the reduction temperature was 230 °C, the heating rate was 2 °C / min, and the reduction time was 2 h. After reduction, the gas was switched to H2, the pressure was increased to 3.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump at a liquid hourly space velocity (LISH) of 2.5 h⁻¹. -1 The molar ratio of H2 / DMO was 50:1, and the reaction temperature was 250℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 61.2%.

[0064] In this embodiment, all other conditions are the same, but the liquid hourly space velocity of DMO is 1.0 h⁻¹. -1 The molar ratio of H2 / DMO was 500:1, and the reaction temperature was 300℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 92.8%.

[0065] Example 6

[0066] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7.95 g of magnesium oxide were added to the copper nitrate solution to adjust the pH to 8-12. The resulting mixture was ultrasonically treated at room temperature for 4 h, followed by vigorous stirring at 1300 rpm for 4 h at 35 °C. The temperature was then raised to 80 °C until the pH reached 7. The resulting mixture was placed in a hydrothermal reactor and treated at 140 °C for 5 h, then filtered and washed with deionized water to obtain a solid. The solid was then dried at 150 °C for 12 h and calcined at 450 °C for 5 h. 0.067 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / MgO precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h to obtain the loaded solid. The loaded solid was then dried at 150 °C for 12 h. Then, the catalyst was calcined in a muffle furnace at 550°C for 4 hours to obtain the catalyst 20Cu-0.5W / MgO.

[0067] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with a H2 content of 5% v / v and a gas space velocity of 150 h⁻¹. -1 The reduction pressure was 0.5 MPa, the reduction temperature was 230℃, the heating rate was 2℃ / min, and the reduction time was 2 h. After reduction, the gas was switched to H2, the pressure was increased to 4.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump. The liquid hourly space velocity (LISH) of the DMO was 2.0 h⁻¹. -1 The molar ratio of H2 / DMO was 100:1, the reaction temperature was 220℃, the conversion rate of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 50.6%.

[0068] In this embodiment, all other conditions are the same, but the liquid hourly space velocity of DMO is 0.8 h⁻¹. -1 The molar ratio of H2 / DMO was 400:1, and the reaction temperature was 300℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 91.5%.

[0069] Example 7

[0070] 7.55 g of copper nitrate trihydrate was dissolved in 100 mL of deionized water at room temperature to prepare a copper nitrate solution. A certain amount of ammonia and 7 g of aluminum oxide were added to the copper nitrate solution to adjust the pH to 8-12, and the mixture was stirred at room temperature for 12 h. The temperature was then raised to 80 °C until the pH reached 7. The resulting mixture was centrifuged, filtered, and washed to obtain a solid. The solid was then dried at 150 °C for 12 h and calcined at 450 °C for 5 h. 1.34 g of ammonium metatungstate was dissolved in 50 mL of deionized water to prepare an ammonium metatungstate solution, which was atomized using an ultrasonic nebulizer. This solution was then mixed with a Cu / Al₂O₃ precursor, utilizing the strong electrostatic interaction between the two to load the ammonium metatungstate component. The mixture was then allowed to stand at room temperature and air-dried for 48 h. The resulting solid was then dried at 150 °C for 12 h. Finally, it was calcined in a muffle furnace at 550 °C for 4 h to obtain the catalyst 20Cu-10W / Al₂O₃.

[0071] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was then filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / Ar mixture with a H2 content of 5% v / v and a gas space velocity of 50 h⁻¹. -1 The reduction pressure was 0.3 MPa, the reduction temperature was 250 °C, the heating rate was 5 °C / min, and the reduction time was 4 h. After reduction, the gas was switched to H2, the pressure was increased to 2.0 MPa, and a methanol solution of 20% dimethyl oxalate (DMO) was injected using a horizontal flow pump. The liquid hourly space velocity (LISH) of the DMO was 4.0 h⁻¹. -1 The molar ratio of H2 / DMO was 30:1, the reaction temperature was 200℃, the conversion rate of dimethyl oxalate was 100%, and the selectivity of methyl acetate was 70.6%.

[0072] In this embodiment, all other conditions are the same, but the liquid hourly space velocity of DMO is 0.8 h⁻¹. -1 The molar ratio of H2 / DMO was 300:1, and the reaction temperature was 260℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 67.8%.

[0073] Example 8

[0074] The catalysts from Examples 1 and 2 were subjected to stability tests. Experiments showed that under the same reduction and reaction conditions in each example, catalyst performance analysis revealed no significant deactivation of the catalyst after 1000 hours of reaction. Figure 4a and 4b As shown in the figure. This demonstrates that both catalysts possess excellent catalytic stability.

[0075] Comparative Example 1

[0076] The 20Cu-10W / SiO2 catalyst was prepared using a traditional co-impregnation method, with the following specific steps: First, 7g of SiO2 was added to 21g of water, and it was observed that the SiO2 completely absorbed the water. Then, 7.55g of copper nitrate trihydrate and 1.34g of ammonium metatungstate were dissolved in 21g of water, and another 7g of SiO2 was added. After air-drying under natural conditions, the mixture was dried in an oven at 100℃ for 8 hours, and then calcined in a muffle furnace at 550℃ for 4 hours to obtain the 20Cu-10W / SiO2 catalyst. Its catalytic performance was tested under the reduction and reaction conditions of Example 1. The conversion rate of dimethyl oxalate was 100%, and the selectivity for methyl acetate was 50.8%.

[0077] Comparative Example 2

[0078] The 20Cu-0.5W / SiO2 catalyst was prepared using a traditional co-impregnation method, with the following specific steps: First, 7.95g of SiO2 was added to 23.85g of water, and it was observed that the SiO2 completely absorbed the water. Then, 7.55g of copper nitrate trihydrate and 0.067g of ammonium metatungstate were dissolved in 23.8g of water, followed by the addition of 7g of SiO2. After air-drying under natural conditions, the mixture was dried in an oven at 100℃ for 8 hours, and then calcined in a muffle furnace at 550℃ for 4 hours to obtain the 20Cu-0.5W / SiO2 catalyst. Its catalytic performance was tested under the reduction and reaction conditions of Example 2. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 60.5%.

[0079] 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 oxalate to methyl acetate or ethanol, characterized in that: The catalyst comprises an active component, an auxiliary component, and a support. The active component is elemental Cu or its oxide, and the auxiliary component is elemental W or its oxide. After activation, the highly active sites are the Cu-W alloy interface and individual Cu and W metals. The support is one or more of silica, alumina, zirconium oxide, zinc oxide, magnesium oxide, and cerium oxide. When the catalyst is used for the selective production of methyl acetate, the first active component, based on the mass of elemental Cu, comprises 1-30%; the second active component, based on the mass of elemental W, comprises 5%-20%; and the remainder is the support. When the catalyst is used for the selective production of ethanol, the first active component, based on the mass of elemental Cu, comprises 5-30%; the second active component, based on the mass of elemental W, comprises 0.05%-3%; and the remainder is the support. The catalyst was prepared by the following steps: (I) Prepare a mixture by mixing a soluble salt of copper, deionized water, ammonia water and a carrier, so that the pH of the mixture is between 8 and 12; (II) The mixture obtained in step (I) is ultrasonically treated at room temperature for 3-5 hours, and then vigorously stirred at 1000-2000 rpm for 3-5 hours at 25-45℃; (III) The mixture after step (II) is heated and evaporated at 70-90℃ until the pH of the mixture is 6-7, and then placed in a hydrothermal reactor and treated at 120-180℃ for 3-8 hours; (IV) The mixture after step (III) is filtered and then washed with deionized water to obtain a solid; (V) The solid obtained in step (IV) is dried at 120-150℃ for 6-24h and then calcined at 300-600℃ for 2-10h to obtain Cu / carrier precursor; the W soluble salt solution is atomized into micron-sized W salt droplets by an ultrasonic atomizer, and the micron-sized W salt droplets are adsorbed and loaded by the electrostatic force between the Cu / carrier precursor and the micron-sized droplets to obtain the loaded material; (VI) Allow the loaded material obtained in step (V) to air dry naturally for 24-48 hours to obtain the loaded solid material; (VII) The supported solid obtained in step (VI) is dried at 100-150℃ for 6-24h and then calcined at 300-650℃ for 2-12h to obtain the catalyst Cu-W / support.

2. The catalyst for the hydrogenation of dimethyl oxalate to methyl acetate or ethanol according to claim 1, characterized in that: In step (I), the soluble salt of copper is one or more of copper nitrate, copper chloride, copper sulfate, or copper acetate.

3. The catalyst for the hydrogenation of dimethyl oxalate to methyl acetate or ethanol according to claim 1, characterized in that: In step (V), the soluble salt of tungsten is one or more of ammonium tungstate, ammonium metatungstate, and sodium tungstate.

4. A method for preparing the catalyst for the hydrogenation of dimethyl oxalate to methyl acetate or ethanol as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (I) Prepare a mixture by mixing a soluble salt of copper, deionized water, ammonia water and a carrier, so that the pH of the mixture is between 8 and 12; (II) The mixture obtained in step (I) is ultrasonically treated at room temperature for 3-5 hours, and then vigorously stirred at 1000-2000 rpm for 3-5 hours at 25-45℃; (III) The mixture after step (II) is heated and evaporated at 70-90℃ until the pH of the mixture is 6-7, and then placed in a hydrothermal reactor and treated at 120-180℃ for 3-8 hours; (IV) The mixture after step (III) is filtered and then washed with deionized water to obtain a solid; (V) The solid obtained in step (IV) is dried at 120-150℃ for 6-24h and then calcined at 300-600℃ for 2-10h to obtain Cu / carrier precursor; the W soluble salt solution is atomized into micron-sized W salt droplets by an ultrasonic atomizer, and the micron-sized W salt droplets are adsorbed and loaded by the electrostatic force between the Cu / carrier precursor and the micron-sized droplets to obtain the loaded material; (VI) Allow the loaded material obtained in step (V) to air dry naturally for 24-48 hours to obtain the loaded solid material; (VII) The supported solid obtained in step (VI) is dried at 100-150℃ for 6-24h and then calcined at 300-650℃ for 2-12h to obtain the catalyst Cu-W / support.

5. The preparation method according to claim 4, characterized in that: In step (I), the soluble salt of copper is one or more of copper nitrate, copper chloride, copper sulfate, or copper acetate; in step (V), the soluble salt of tungsten is one or more of ammonium tungstate, ammonium metatungstate, or sodium tungstate.

6. The application of the catalyst according to any one of claims 1-3 in the hydrogenation of dimethyl oxalate to methyl acetate, characterized in that: First, the catalyst is loaded into a reaction tube, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is activated in hydrogen or a hydrogen-inert gas mixture. After activation, the reaction conditions are adjusted to the specified reaction conditions, and dimethyl oxalate or a mixture of dimethyl oxalate and methanol is pumped in. The reaction conditions are: temperature 120-350℃, pressure 0.3-6.0 MPa, and liquid hourly space velocity (LISH) of dimethyl oxalate 0.01-6.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-800:

1.

7. The application according to claim 6, characterized in that: The reaction conditions were: temperature 120-280℃, pressure 0.3-2.0 MPa, and dimethyl oxalate liquid hourly space velocity 2-6 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-300:

1.

8. The application of the catalyst according to any one of claims 1-3 in the hydrogenation of dimethyl oxalate to ethanol, characterized in that: First, the catalyst is loaded into a reaction tube, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is activated in hydrogen or a hydrogen-inert gas mixture. After activation, the reaction conditions are adjusted to the specified reaction conditions, and dimethyl oxalate or a mixture of dimethyl oxalate and methanol is pumped in. The reaction conditions are: temperature 250-350℃, pressure 3.0-6.0 MPa, and liquid hourly space velocity (LISH) of dimethyl oxalate 0.01-2 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 300:1-800:

1.

9. The application according to claim 6 or 8, characterized in that: The catalyst activation conditions are a pressure of 0.1-0.5 MPa and a gas space velocity of 10-300 h⁻¹. -1 The activation temperature is 160-300℃, the heating rate is 0.1-20℃ / min, and the activation time is 0.5-8h.

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