A catalyst for regulating selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol, and a preparation method and application thereof

Abstract

This invention discloses a catalyst for controlling the selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol. The catalyst is a bifunctional nano-heterogeneous catalyst comprising a first active component, a second active component, and a support. The first active component is Cu, the second active component is Nb, and the highly active reaction site is Cu. 0 -Cu + The interface is composed of -Nb₂O₅, and the support is one or more of silicon dioxide, alumina, and zirconium oxide. This invention also discloses its preparation method and applications. In the catalytic hydrogenation reaction of dimethyl oxalate, the bifunctional nano-heterogeneous catalyst of this invention can be easily controlled by adjusting reaction conditions such as reaction temperature, reaction pressure, and the molar ratio of hydrogen to dimethyl oxalate to regulate the product and synthesize ethylene glycol or ethanol with high selectivity. Furthermore, the catalyst exhibits extremely high stability and catalytic activity, and high utilization rate of the active component.

Description

Technical Field

[0001] This invention relates to the field of ethanol and ethylene glycol synthesis technology, specifically to a catalyst for controlling the selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol, its preparation method, and its application. Background Technology

[0002] Ethanol is a widely used chemical raw material, playing an important role in many industries such as preservatives, medicine, solvents, and food. Furthermore, as a clean energy source, ethanol can be added to gasoline in a certain proportion as an additive. The addition of ethanol can increase the octane rating of gasoline. The high oxygen content of ethanol itself allows for more complete combustion of ethanol gasoline, reducing emissions of pollutants such as CO and hydrocarbons, alleviating air pollution, and reducing gasoline consumption, thus decreasing dependence on petroleum resources. With the gradual phasing out of the previously widely used gasoline additive methyl tert-butyl ether (MTBE), the market for ethanol gasoline will further expand, and my country's demand for ethanol will increase accordingly. The efficient synthesis process of ethanol has attracted widespread attention from researchers. Currently, the main methods for producing ethanol include bio-fermentation, ethylene hydration, and syngas synthesis. Although bio-fermentation has a simple process and relatively low energy consumption and cost, given China's large population and limited land resources, my country has always adhered to the basic principle of "not competing with people for food and land" in energy development. Ethylene hydration refers to the process of mixing ethylene with water vapor under certain reaction conditions and then undergoing a catalytic hydration reaction to obtain ethanol. This method uses petroleum-based ethylene, resulting in high production costs, which is inconsistent with my country's energy structure characterized by abundant coal, scarce oil, and limited natural gas. The syngas-based ethanol production process includes one-step and multi-step methods. The one-step method involves directly generating high-value-added ethanol from syngas in the next step under the action of a catalyst; the steps are simple, but it suffers from low selectivity of the target product, high reaction temperature, and high cost, thus preventing large-scale industrial application. The multi-step syngas-based ethanol synthesis method involves first preparing methanol from syngas, then condensing methanol to prepare dimethyl ether, followed by carbonylation to prepare methyl acetate, and finally hydrogenating methyl acetate to obtain ethanol. Although this method has achieved large-scale industrial application, it still suffers from low selectivity and cumbersome steps.

[0003] Ethylene glycol is the simplest diol. It is colorless and odorless, toxic to animals, with a lethal dose for humans of approximately 1.6 g / kg. It is miscible with water and acetone. The main use of ethylene glycol is as a raw material in the polyester industry for synthesizing polyester resins, polyester plastics, and polyester fibers. For example, ethylene glycol can polymerize with terephthalic acid to form ethylene glycol terephthalate, i.e., PET plastic, which is widely used in daily life. Currently, the main methods for producing ethylene glycol are the ethylene oxide process and the dimethyl oxalate hydrogenation process. The ethylene oxide process has the advantage of high product purity, but it requires a large amount of petroleum-based raw materials, which is not suitable for my country's energy structure. The dimethyl oxalate hydrogenation process for producing ethylene glycol has achieved large-scale industrial application in my country, but problems such as poor purity of the produced ethylene glycol and poor catalyst stability still exist during its application.

[0004] Patent CN109433205B reports a radial Cu / SiO2 hydrogenation catalyst that achieves a dimethyl oxalate conversion >99% and an ethylene glycol selectivity >96% under high hydrogen-to-ester ratio (50:1). Patent CN101648134B reports a method for synthesizing a copper-silicon catalyst using an alcohol as a co-solvent, but the ethylene glycol selectivity does not exceed 96%. An article (Chem. Commun., 2017, 53, 5376) reports an Fe5C2 catalyst for the hydrogenation of dimethyl oxalate to ethanol, achieving a selectivity of 89.6%. Patent CN101830776B reports a method for synthesizing ethanol, first using a Pd-based catalyst to prepare dimethyl oxalate, then using a Cu-based catalyst for the hydrogenation of dimethyl oxalate to ethanol. In a fixed-bed reactor, the ethanol selectivity is only up to 85%. Patent CN106563480A discloses a molybdenum carbide catalyst for the hydrogenation of dimethyl oxalate to ethanol, achieving a selectivity of up to 83% for ethanol at a dimethyl oxalate conversion of 100%. The selectivity for methyl acetate is very low. Furthermore, the patent does not report results regarding catalyst stability.

[0005] Current research indicates that Cu / SiO2 catalysts are commonly used for the hydrogenation of dimethyl oxalate. However, Cu / SiO2 catalysts exhibit a greater tendency to produce ethylene glycol in this system, and suffer from poor selectivity and stability. There are few reports on the highly selective hydrogenation of dimethyl oxalate to ethanol. Therefore, designing a catalytic system that can achieve high activity, high selectivity, and high stability for the hydrogenation of dimethyl oxalate to ethylene glycol or ethanol 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 selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol, its preparation method and application, and to ensure a high conversion rate of dimethyl oxalate and selective production of ethylene glycol or ethanol by controlling the reaction conditions, thereby overcoming the shortcomings of the prior art.

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

[0008] A catalyst for selectively hydrogenating dimethyl oxalate to ethylene glycol or ethanol is disclosed. The catalyst is a bifunctional nano-heterogeneous catalyst comprising a first active component, a second active component, and a support. The first active component is Cu, the second active component is Nb, and the highly active reaction site is Cu. 0 -Cu + The interface is composed of -Nb2O5, and the carrier is one or more of silicon dioxide, alumina, and zirconium oxide;

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

[0010] (I) At room temperature, a mixture was prepared by mixing a soluble salt of Cu, a soluble salt of Nb, a bifunctional chelating ligand, a hydroxyl-functionalized nanocarrier, ammonia, and deionized water, such that the pH of the mixture was between 8 and 12.

[0011] (II) The mixture obtained in step (I) is ultrasonically treated at room temperature at 10-50 kHz for 3-5 h, and then vigorously stirred at 400-500 rpm at 25-35 °C for 3-5 h.

[0012] (III) Transfer the mixture obtained in step (II) to a sealed pressure-resistant hydrothermal reactor, heat it to 120-180℃ and treat it for 3-8 hours; after cooling to room temperature, open the sealed pressure-resistant hydrothermal reactor, reheat it to 120-180℃, and evaporate it until the mixture is gel-like.

[0013] (IV) The gelatinous solid obtained in step (III) is dried at 145-155℃ for 10-12h, and then calcined at 300-600℃ for 2-10h in an inert gas atmosphere to obtain the catalyst.

[0014] Furthermore, the first active component, based on the mass of Cu, has a content of 5-30%; the second active component, based on the mass of Nb, has a content of 0.1%-10%; the remainder is a carrier.

[0015] Furthermore, the first active component, based on the mass of Cu, has a content of 10-25%; the second active component, based on the mass of Nb, has a content of 3%-10%; the remainder is a carrier.

[0016] Further, in step (I), the soluble salt of Cu is one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate; the soluble salt of Nb is one or two of niobium oxalate and ammonium niobium oxalate; the bifunctional chelating ligand is one or more of ethanolamine, 3-propanolamine, 2-propanolamine, and hexanolamine; the molar ratio of the bifunctional chelating ligand to Cu and Nb metal ions is 1-10:1; and the hydroxyl-functionalized nanocarrier is one or more of hydroxyl-containing nano-silica, hydroxyl-containing nano-alumina, and hydroxyl-containing nano-zirconia.

[0017] A method for preparing a catalyst for selectively hydrogenating dimethyl oxalate to ethylene glycol or ethanol comprises the following steps:

[0018] (I) At room temperature, a mixture was prepared by mixing a soluble salt of Cu, a soluble salt of Nb, a bifunctional chelating ligand, a hydroxyl-functionalized nanocarrier, ammonia, and deionized water, such that the pH of the mixture was between 8 and 12.

[0019] (II) The mixture obtained in step (I) is ultrasonically treated at room temperature at 10-50 kHz for 3-5 h, and then vigorously stirred at 400-500 rpm at 25-35 °C for 3-5 h.

[0020] (III) Transfer the mixture obtained in step (II) to a sealed pressure-resistant hydrothermal reactor, heat it to 120-180℃ and treat it for 3-8 hours; after cooling to room temperature, open the sealed pressure-resistant hydrothermal reactor, reheat it to 120-180℃, and evaporate it until the mixture is gel-like.

[0021] (IV) The colloidal solid obtained in step (III) is dried at 145-155℃ for 10-12h, and then calcined at 300-600℃ for 2-10h under an inert gas atmosphere to obtain the catalyst;

[0022] The catalyst is a bifunctional nano-heterogeneous catalyst, comprising a first active component, a second active component, and a support. The first active component is Cu, the second active component is Nb, and the highly active reaction site is Cu. 0 -Cu + The interface is composed of -Nb2O5, and the carrier is one or more of silicon dioxide, alumina, and zirconium oxide.

[0023] Furthermore, the first active component, based on the mass of Cu, has a content of 5-30%; the second active component, based on the mass of Nb, has a content of 0.1%-10%; the remainder is a carrier.

[0024] Furthermore, the first active component, based on the mass of Cu, has a content of 10-25%; the second active component, based on the mass of Nb, has a content of 3%-10%; the remainder is a carrier.

[0025] Further, in step (I), the soluble salt of Cu is one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate; the soluble salt of Nb is one or two of niobium oxalate and ammonium niobium oxalate; the bifunctional chelating ligand is one or more of ethanolamine, 3-propanolamine, 2-propanolamine, and hexanolamine; the molar ratio of the bifunctional chelating ligand to Cu and Nb metal ions is 1-2:1; and the hydroxyl-functionalized nanocarrier is one or more of hydroxyl-containing nano-silica, hydroxyl-containing nano-alumina, and hydroxyl-containing nano-zirconia.

[0026] The application of the above-mentioned catalyst in the selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol includes the following steps: first, the catalyst is loaded into a fixed-bed reactor, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is reduced in hydrogen or a hydrogen-inert gas mixture under the following conditions: gas space velocity of 50-3000 h⁻¹. -1 The reduction pressure is 0.1-3.0 MPa, the reduction temperature is 200-350℃, the heating rate is 0.1-10℃ / min, and the reduction time is 0.5-18 h. After reduction, adjust to the specified reaction conditions, and pump in dimethyl oxalate or a mixture of dimethyl oxalate and methanol. The reaction conditions are: reaction temperature 120-350℃, reaction pressure 0.1-7.0 MPa, and liquid hourly space velocity (LISH) of dimethyl oxalate 0.01-5.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-1000:1;

[0027] The product, ethylene glycol or ethanol, can be controlled by varying the reaction temperature, reaction pressure, and the molar ratio of hydrogen to dimethyl oxalate.

[0028] Furthermore, the gas space velocity under catalytic reduction conditions is 50-500 h⁻¹. -1 The reduction pressure was 0.1-0.5 MPa, the reduction temperature was 200-300℃, the heating rate was 1-3℃ / min, and the reduction time was 3-6 h; the reaction conditions included a reaction temperature of 180-320℃, a reaction pressure of 0.1-5.0 MPa, and a dimethyl oxalate liquid hourly space velocity of 0.1-2.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-500:1.

[0029] The beneficial effects of this invention are:

[0030] 1. The Cu prepared by this invention 0 -Cu +A bifunctional nano-heterogeneous catalyst with a highly active reaction site composed of -Nb₂O₅ interfaces is used as a support for hydroxyl-functionalized nano-oxides (silicon oxide, aluminum oxide, zirconium oxide). First, the Cu component is anchored to form a SO-Cu-O (S as the support) structure by the binding of hydroxyl groups in the bifunctional chelating ligands with hydroxyl groups on the surface of the nano-oxides. Then, the Nb component is anchored using the -NH₂ group at the other end of the bifunctional chelating ligand, resulting in a precursor structure similar to SO-Cu-OC-Nb after loading. This not only allows the metal component to be highly dispersed on the support surface, forming a strong metal-support interaction, but also ensures close contact between the first and second active components. Furthermore, during subsequent calcination and reduction activation processes, Cu₂O₅ forms on the support surface. 0 -Cu + -Nb₂O₅ has a highly active interface. This not only promotes the adsorption and activation of both dimethyl oxalate and hydrogen, but also significantly improves the catalyst stability. Through the electronic interactions between the two components, the product is ethylene glycol at low temperature, low pressure, and low molar ratio of hydrogen to dimethyl oxalate, while the product is ethanol at high temperature, high pressure, and high molar ratio of hydrogen to dimethyl oxalate.

[0031] 2. Compared with traditional Cu-based catalysts, the present invention has Cu... 0 -Cu + The bifunctional nanoheterogeneous catalyst with highly active reaction sites at the interface composed of -Nb2O5 mainly exhibits Cu... 0 / Cu + The ratio can be flexibly adjusted according to the Nb content, and the Nb2O5 and Cu on the catalyst surface 0 Cu + The two components are coupled during the catalytic reaction, which improves the performance of the catalytic hydrogenation reaction. This achieves the following: (1) improving the activity of the catalyst and flexibly adjusting the preparation of the target product ethylene glycol or ethanol with high selectivity; (2) enabling the hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol under milder conditions; and (3) improving the stability of the catalytic system. The catalyst has excellent stability whether synthesizing ethanol or ethylene glycol.

[0032] 3. The bifunctional nano-heterogeneous catalyst of this invention can be easily controlled in the catalytic hydrogenation reaction of dimethyl oxalate by adjusting reaction conditions such as reaction temperature, reaction pressure, and the molar ratio of hydrogen to dimethyl oxalate (ethanol is generated under high temperature, high pressure, and high hydrogen / dimethyl oxalate ratio, and ethylene glycol is generated by lowering the pressure and temperature and hydrogen / dimethyl oxalate ratio). This allows for the high-selectivity synthesis of ethylene glycol or ethanol, with an ethylene glycol selectivity of up to 98.6% and an ethanol selectivity of 97.3%. Furthermore, the catalyst exhibits extremely high stability and catalytic activity, and high utilization rate of the active component.

[0033] 4. The bifunctional nano-heterogeneous catalyst of this invention has advantages such as structural stability, high mechanical strength, good thermal conductivity, high substrate conversion rate, and controllable product selectivity. The catalyst preparation method of this invention is simple, uses readily available raw materials, is low in cost, is environmentally friendly and pollution-free, has good reproducibility, and is easy to scale up for mass production. Attached Figure Description

[0034] Figure 1 The electron microscope (EM) elemental analysis images of the catalyst in Example 1 are as follows: original EEM image of the catalyst, Cu elemental analysis image, Nb elemental analysis image, and Si elemental analysis image.

[0035] Figure 2 This is the XPS plot of the catalyst from Example 1.

[0036] Figure 3 This is the XRD pattern of the catalyst in Example 1.

[0037] Figure 4 This is a TEM image of the catalyst from Example 1.

[0038] Figure 5 This is a performance stability test diagram of the catalyst in Example 8, whose reaction product is ethylene glycol.

[0039] Figure 6 This is a performance stability test diagram of the catalyst in Example 9, where the reaction product is ethanol. Detailed Implementation

[0040] 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.

[0041] Example 1

[0042] At room temperature, 7.55 g of copper nitrate trihydrate, 2.0 g of ammonium niobate oxalate, 4.0 g of 3-propanolamine, 7 g of hydroxyl-containing nano-silica, and 20 ml of ammonia water (an aqueous solution containing 25%–28% ammonia) were dissolved in 100 mL of deionized water and stirred until the pH was 8–12. The mixture was ultrasonically treated at 45000 Hz for 3 h at room temperature, followed by vigorous stirring at 450 rpm for 3 h at 30 °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 120 °C for 5 h. After cooling to room temperature, the sealed, pressure-resistant hydrothermal reactor was opened, and the mixture was reheated to 120 °C until it became gelatinous. The resulting gelatinous solid was dried at 150 °C for 12 h, and then calcined at 450 °C for 5 h under a nitrogen atmosphere. The resulting catalyst was named 1-Cu-Nb / SiO2.

[0043] The catalyst 1-Cu-Nb / SiO2 prepared in this embodiment, as shown in... Figure 1-4 As shown, Figure 1 This indicates that the active components Cu and Nb in the catalyst are uniformly distributed and tightly bonded on the catalyst surface. Figure 2 This indicates that the catalyst contains Cu. 0 and Cu + , Figure 1 Combination Figure 2 Confirmation that Cu forms on the surface of the catalyst support 0 -Cu + -Nb2O5 highly active interface. Figure 3 This indicates that the active component Cu in the catalyst is highly dispersed on the support surface and does not form obvious large particles. Figure 4 The catalyst surface shows that the active component Cu consists of highly active small particles of about 3-5 nm, which is consistent with... Figure 3 The XRD results are consistent with those in the original text, confirming that the prepared catalyst is a nanocatalyst.

[0044] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump. The liquid hourly space velocity (LHSV) of DMO was 0.4 h⁻¹. -1 The molar ratio of H2 / DMO was 25:1, and the reaction temperature was 200℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of ethylene glycol was 98.5%.

[0045] Example 2

[0046] At room temperature, 7.55 g of copper nitrate trihydrate, 1.0 g of ammonium niobate oxalate, 4.0 g of 3-propanolamine, 7 g of hydroxyl-containing nano-silica, and 20 ml of ammonia water (an aqueous solution containing 25%–28% ammonia) were dissolved in 100 mL of deionized water and stirred until the pH was 8–12. The mixture was ultrasonically treated at 45000 Hz for 3 h at room temperature, followed by vigorous stirring at 450 rpm for 3 h at 30 °C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (same as in Example 1) and heated to 120 °C for 5 h. After cooling to room temperature, the sealed, pressure-resistant hydrothermal reactor was opened, and the mixture was reheated to 120 °C until it became gelatinous. The resulting gelatinous solid was dried at 150 °C for 12 h and then calcined at 450 °C for 5 h under a nitrogen atmosphere. The resulting catalyst was named 2-Cu-Nb / SiO2.

[0047] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump. The liquid hourly space velocity (LHSV) of DMO was 0.35 h⁻¹. -1 The molar ratio of H2 / DMO was 40:1, and the reaction temperature was 200℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of ethylene glycol was 98.0%.

[0048] Example 3

[0049] At room temperature, 7.55 g of copper nitrate trihydrate, 2.0 g of niobium ammonium oxalate, 4.0 g of 3-propanolamine, 7 g of hydroxyl-containing nano-alumina, and 20 ml of ammonia water (an aqueous solution containing 25%–28% ammonia) were dissolved in 100 mL of deionized water and stirred until the pH was 8–12. The mixture was ultrasonically treated at 45000 Hz for 3 h at room temperature, followed by vigorous stirring at 450 rpm for 3 h at 30 °C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (same as in Example 1) and heated to 120 °C for 5 h. After cooling to room temperature, the sealed, pressure-resistant hydrothermal reactor was opened, and the mixture was reheated to 120 °C until it became gelatinous. The resulting gelatinous solid was dried at 150 °C for 12 h and then calcined at 450 °C for 5 h under a nitrogen atmosphere. The resulting catalyst was named 3-Cu-Nb / Al₂O₃.

[0050] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 h. After reduction, the gas was switched to H2, the pressure was increased to 2.0 MPa, and a 20% (w / w) methanol solution of dimethyl oxalate (DMO) was injected using a high-pressure plunger pump at a DMO liquid hourly space velocity (LISH) of 0.5 h⁻¹. -1 The molar ratio of H2 / DMO was 40:1, and the reaction temperature was 200℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of ethylene glycol was 98.6%.

[0051] Example 4

[0052] At room temperature, 7.55 g of copper nitrate trihydrate, 2.0 g of ammonium niobate oxalate, 4.0 g of 3-propanolamine, 7 g of nano-zirconia with hydroxyl groups, and 20 ml of ammonia water (an aqueous solution containing 25%–28% ammonia) were dissolved in 100 mL of deionized water and stirred to achieve a pH of 8–12. The mixture was ultrasonically treated at 45000 Hz for 3 h at room temperature, followed by vigorous stirring at 450 rpm for 3 h at 30 °C. The mixture was then transferred to a sealed, pressure-resistant hydrothermal reactor (same as in Example 1) and heated to 120 °C for 5 h. After cooling to room temperature, the sealed, pressure-resistant hydrothermal reactor was opened, and the mixture was reheated to 120 °C until it became gelatinous. The resulting gelatinous solid was dried at 150 °C for 12 h and then calcined at 450 °C for 5 h under a nitrogen atmosphere. The resulting catalyst was named 4-Cu-Nb / ZrO2.

[0053] 1.0 g of the above catalyst was loaded into a fixed-bed reactor, and the entire reaction tube was filled with quartz sand to reduce the catalyst. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump. The liquid hourly space velocity (LHSV) of DMO was 0.6 h⁻¹. -1 The molar ratio of H2 / DMO was 25:1, and the reaction temperature was 200℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity of ethylene glycol was 98.0%.

[0054] Example 5

[0055] 1.0 g of the catalyst from Example 1 was loaded into a fixed-bed reactor for reduction. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump at a liquid hourly space velocity (LISH) of 0.2 h⁻¹. -1 The molar ratio of H2 / DMO was 250:1, and the reaction temperature was 270℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 97%.

[0056] Example 6

[0057] 1.0 g of the catalyst from Example 3 was loaded into a fixed-bed reactor and reduced. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump. The liquid hourly space velocity (LHSV) of DMO was 0.25 h⁻¹. -1 The molar ratio of H2 / DMO was 250:1, and the reaction temperature was 270℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 97.2%.

[0058] Example 7

[0059] 1.0 g of the catalyst from Example 4 was loaded into a fixed-bed reactor for reduction. The reducing gas was an H2 / N2 mixture with an H2 content of 10% v / v and a gas space velocity of 500 h⁻¹. -1 The reduction pressure was 0.1 MPa, the reduction temperature was 280℃, the heating rate was 1℃ / min, and the reduction time was 3 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 high-pressure plunger pump at a liquid hourly space velocity (LISH) of 0.2 h⁻¹. -1 The molar ratio of H2 / DMO was 270:1, and the reaction temperature was 280℃. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 97.3%.

[0060] Example 8

[0061] The catalyst from Example 1 was subjected to an experimental stability test to produce ethylene glycol. The experiment revealed that under the same reduction and reaction conditions as in Example 1, catalyst performance analysis showed no significant deactivation of the catalyst after 800 hours of reaction. Figure 5 As shown in the figure. This indicates that the catalyst exhibits excellent stability when the product is ethylene glycol.

[0062] Example 9

[0063] The catalyst from Example 1 was subjected to an experimental stability test with ethanol as the product. The experiment revealed that under the same reduction and reaction conditions as in Example 5, catalyst performance analysis showed no significant deactivation of the catalyst after 800 hours of reaction. Figure 6 As shown in the figure. This indicates that the catalyst also exhibits excellent stability when the product is ethanol.

[0064] Comparative Example 1

[0065] The R1-Cu-Nb / SiO2 catalyst was prepared using a traditional co-impregnation method, with the following specific steps: 7.55 g of copper nitrate trihydrate and 2.0 g of ammonium niobate oxalate were dissolved in 15 ml of ammonia water (an aqueous solution containing 25%–28% ammonia). Then, 7 g of silicon dioxide (20-40 mesh) without hydroxyl groups was added. After air drying under natural conditions, the mixture was dried in an oven at 100°C for 8 hours, and then calcined in a muffle furnace at 450°C for 4 hours to obtain the R1-Cu-Nb / SiO2 catalyst. Its catalytic performance was tested under the reduction and reaction conditions of Example 1. The conversion rate of dimethyl oxalate was 89%, and the selectivity for ethylene glycol was 32.5%.

[0066] Comparative Example 2

[0067] The catalyst from Comparative Example 1 was used, and its catalytic performance was tested under the reduction and reaction conditions of Example 5. The conversion rate of dimethyl oxalate was 100%, and the selectivity for ethanol was 43.6%.

[0068] 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 controlling the selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol, characterized in that, The catalyst is a bifunctional nano-heterogeneous catalyst, comprising a first active component, a second active component, and a support. The first active component is Cu, and the second active component is Nb. Before use, the catalyst is reduced in a hydrogen-containing reducing atmosphere, after which the highly active reaction sites are Cu. 0 -Cu + The interface is composed of -Nb2O5, and the carrier is one or more of silicon dioxide, alumina, and zirconium oxide; The catalyst was prepared by the following steps: (I) At room temperature, a mixture is prepared by mixing a soluble salt of Cu, a soluble salt of Nb, a bifunctional chelating ligand, a hydroxyl-functionalized nanocarrier, ammonia, and deionized water, such that the pH of the mixture is between 8 and 12; wherein the bifunctional chelating ligand is one or more of ethanolamine, 3-propanolamine, 2-propanolamine, and hexanolamine. (II) The mixture obtained in step (I) is ultrasonically treated at room temperature at 10-50 kHz for 3-5 h, and then vigorously stirred at 400-500 rpm at 25-35 °C for 3-5 h. (III) Transfer the mixture obtained in step (II) to a sealed pressure-resistant hydrothermal reactor, heat it to 120-180℃ and treat it for 3-8 hours; after cooling to room temperature, open the sealed pressure-resistant hydrothermal reactor, reheat it to 120-180℃, and evaporate it until the mixture is gel-like. (IV) The gelatinous solid obtained in step (III) is dried at 145-155℃ for 10-12h, and then calcined at 300-600℃ for 2-10h under nitrogen to obtain the catalyst.

2. The catalyst for the selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 1, characterized in that, The first active component, based on the mass of Cu, has a content of 5-30%; the second active component, based on the mass of Nb, has a content of 0.1%-10%; the remainder is a carrier.

3. The catalyst for the selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 1, characterized in that, The first active component, based on the mass of Cu, has a content of 10-25%; the second active component, based on the mass of Nb, has a content of 3%-10%; the remainder is a carrier.

4. The catalyst for the selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 1, characterized in that, Step (I) The soluble salt of Cu is one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate; the soluble salt of Nb is one or two of niobium oxalate and ammonium niobium oxalate; the molar ratio of the bifunctional chelating ligand to Cu and Nb metal ions is 1-10:1; the hydroxyl-functionalized nanocarrier is one or more of hydroxyl-containing nano-silica, hydroxyl-containing nano-alumina, and hydroxyl-containing nano-zirconia.

5. A method for preparing a catalyst for selectively hydrogenating dimethyl oxalate to ethylene glycol or ethanol, characterized in that, The steps are as follows: (I) At room temperature, a mixture is prepared by mixing a soluble salt of Cu, a soluble salt of Nb, a bifunctional chelating ligand, a hydroxyl-functionalized nanocarrier, ammonia, and deionized water, such that the pH of the mixture is between 8 and 12; wherein the bifunctional chelating ligand is one or more of ethanolamine, 3-propanolamine, 2-propanolamine, and hexanolamine. (II) The mixture obtained in step (I) is ultrasonically treated at room temperature at 10-50 kHz for 3-5 h, and then vigorously stirred at 400-500 rpm at 25-35 °C for 3-5 h. (III) Transfer the mixture obtained in step (II) to a sealed pressure-resistant hydrothermal reactor, heat it to 120-180℃ and treat it for 3-8 hours; after cooling to room temperature, open the sealed pressure-resistant hydrothermal reactor, reheat it to 120-180℃, and evaporate it until the mixture is gel-like. (IV) The gelatinous solid obtained in step (III) is dried at 145-155℃ for 10-12h, and then calcined at 300-600℃ for 2-10h under nitrogen to obtain the catalyst; The catalyst is a bifunctional nano-heterogeneous catalyst, comprising a first active component, a second active component, and a support. The first active component is Cu, and the second active component is Nb. Before use, the catalyst is reduced in a hydrogen-containing reducing atmosphere, after which the highly active reaction sites are Cu. 0 -Cu + The interface is composed of -Nb2O5, and the carrier is one or more of silicon dioxide, alumina, and zirconium oxide.

6. The method for preparing the catalyst for selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 5, characterized in that, The first active component, based on the mass of Cu, has a content of 5-30%; the second active component, based on the mass of Nb, has a content of 0.1%-10%; the remainder is a carrier.

7. The method for preparing the catalyst for selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 5, characterized in that, The first active component, based on the mass of Cu, has a content of 10-25%; the second active component, based on the mass of Nb, has a content of 3%-10%; the remainder is a carrier.

8. The method for preparing the catalyst for selective hydrogenation of dimethyl oxalate to ethylene glycol or ethanol according to claim 5, characterized in that, Step (I) The soluble salt of Cu is one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate; the soluble salt of Nb is one or two of niobium oxalate and ammonium niobium oxalate; the molar ratio of the bifunctional chelating ligand to Cu and Nb metal ions is 1-2:1; the hydroxyl-functionalized nanocarrier is one or more of hydroxyl-containing nano-silica, hydroxyl-containing nano-alumina, and hydroxyl-containing nano-zirconia.

9. The use of the catalyst according to any one of claims 1-4 in controlling the selective hydrogenation of dimethyl oxalate to prepare ethylene glycol or ethanol, characterized in that, The process includes the following steps: First, the catalyst is loaded into a fixed-bed reactor, and the entire reaction tube is filled with quartz sand. Before use, the catalyst is reduced in hydrogen or hydrogen / nitrogen gas under the following conditions: gas space velocity of 50-3000 h⁻¹. -1 The reduction pressure is 0.1-3.0 MPa, the reduction temperature is 200-350℃, the heating rate is 0.1-10℃ / min, and the reduction time is 0.5-18 h. After reduction, adjust to the specified reaction conditions, and pump in dimethyl oxalate or a mixture of dimethyl oxalate and methanol. The reaction conditions are: reaction temperature 120-350℃, reaction pressure 0.1-7.0 MPa, and liquid hourly space velocity (LISH) of dimethyl oxalate 0.01-5.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-1000:1; The product, ethylene glycol or ethanol, can be controlled by varying the reaction temperature, reaction pressure, and the molar ratio of hydrogen to dimethyl oxalate.

10. The application according to claim 9, characterized in that, The gas space velocity under catalytic reduction conditions is 50-500 h⁻¹ -1 The reduction pressure was 0.1-0.5 MPa, the reduction temperature was 200-300℃, the heating rate was 1-3℃ / min, and the reduction time was 3-6 h; the reaction conditions included a reaction temperature of 180-320℃, a reaction pressure of 0.1-5.0 MPa, and a dimethyl oxalate liquid hourly space velocity of 0.1-2.0 h⁻¹. -1 The molar ratio of hydrogen to dimethyl oxalate is 5:1-500:1.

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