Device and process for preparing ethylene glycol and co-producing methanol from carbon dioxide source ethylene carbonate under mild conditions

Abstract

The invention provides a device and a process for preparing ethylene glycol and co-producing methanol from carbon dioxide source ethylene carbonate under mild conditions. The device comprises an ethylene carbonate rectifying tower, a reaction tower, a gas-liquid separator, an ethylene glycol rectifying tower, a cooling tower, a methanol recovery tower, an electrolysis tower and a liquefaction tower. The process comprises the following steps of: feeding ethylene carbonate and hydrogen into a reaction tower according to a ratio, and carrying out catalytic hydrogenation reaction with a solid catalyst at a relatively mild reaction temperature to generate a reaction crude product; after the crude ethylene glycol, gaseous methanol and unreacted hydrogen pass through a gas-liquid separator, the crude ethylene glycol is refined through an ethylene glycol rectifying tower to obtain an ethylene glycol product, after the gaseous methanol and the hydrogen are separated through a cooling tower, methanol enters a methanol recovery tower to be refined to obtain a methanol product, and excessive hydrogen enters a reaction tower to react again. The production scheme provided by the invention has the advantages of relatively high production efficiency, capability of obtaining various industrial products, relatively mild reaction conditions and the like.

Description

Technical Field

[0001] The present invention designs a method for preparing ethylene glycol and co-producing methanol, and particularly relates to an apparatus and process for producing ethylene glycol and co-producing methanol from ethylene carbonate as a carbon dioxide source under mild conditions. Background Art

[0002] With the development of modern industry, the world's demand for energy has been continuously climbing. Although the research and utilization of clean energy are constantly developing, fossil fuels represented by coal, petroleum, and natural gas still play a crucial role in the current energy system. According to the statistics of the International Energy Agency (IEA) in July 2020, 38% of the global electricity supply comes from coal.

[0003] Now the content of CO 2 in the atmosphere is much higher than before, which will have a very adverse impact on the climate and environment. Therefore, directly or indirectly converting CO 2 into useful energy and materials is of great significance for reducing CO 2 in the air.

[0004] However, at the same time, carbon dioxide, as a carbonaceous compound with rich reserves, is a stable and inexpensive carbon resource. Therefore, CO 2 as a cheap, non-toxic and rich in reserves C1 resource, through effective CO 2 capture and conversion means, synthesizing high-value-added chemicals, is one of the most promising ways to solve both energy problems and environmental problems at the same time. Converting carbon dioxide resources into high-value chemicals has important resource, environmental and economic significance for realizing the reuse of carbon resources. For this reason, a process flow for further hydrogenating ethylene carbonate as an organic intermediate to produce organic chemicals ethylene glycol and methanol under mild conditions is designed - a method for producing ethylene glycol and co-producing methanol from ethylene carbonate as a carbon dioxide source under mild conditions.

[0005] The main products of the technical route of the present invention are ethylene glycol and methanol:

[0006] Ethylene Glycol (EG), C 2 H 6 O 2 , with a molecular weight of 62.07 and a purity > 99.9%. Melting point -13°C, boiling point 197.5°C, flash point 108.2°C, relative density (water = 1) 1.1 g / cm 3(20℃), relative vapor density (air=1) 2.1. It is an important organic chemical raw material, commonly used in the production of polyester, polyester, antifreeze, surfactants, polyester resins, plasticizers, pesticides and pharmaceutical intermediates, etc. More than 90% of these downstream products are used in the polyester industry. In recent years, due to the rapid development of the textile industry and the strong demand for polyester, the market demand for ethylene glycol has also been high. In addition, ethylene glycol is also used as an antifreeze agent for engines, a gas dehydrating agent, and a component of cosmetics and explosives.

[0007] At present, the more mature production method of ethylene glycol on an industrial scale is to produce ethylene glycol by liquid phase hydration of ethylene oxide and water in a tubular reactor under pressure (2.23MPa) and 190-200℃. 2 The technology for producing ethylene glycol is also an urgent, feasible, green and economical route.

[0008] Currently CO 2 The production of ethylene glycol is mainly divided into two steps: first, CO 2 Cycloaddition to synthesize ethylene carbonate, followed by further hydrolysis of ethylene carbonate to generate CO 2 and ethylene glycol, which is the Omega process developed by Shell. Obviously, this process produces CO 2 Therefore, the hydrolysis of ethylene carbonate is replaced by hydrogenation reaction, using CO 2 The industrial step of cycloaddition synthesis of ethylene carbonate can theoretically achieve CO 2 Ethylene glycol production technology without CO generation 2 , atomic utilization rate is 100%, and it has great application potential.

[0009] Methanol, CH 4 O, molecular weight 32.042, purity > 99.9%, melting point -98 ° C, boiling point 48.1 ° C, flash point 11.1 ° C, relative density (water = 1) 0.8 g / cm 3 (20℃), relative vapor density (air=1) 1.11. It is an important organic chemical raw material, widely used in many fields such as fine chemicals, plastics, automotive fuels and high-power battery raw materials. It is also widely used in the fields of national defense industry, dyes, coatings, organic synthesis, medicine, pesticides, etc. As a good organic solvent, it is widely used as a reaction medium in medicine and organic synthesis. Methanol has a wide range of uses and considerable production economic benefits.

[0010] Meanwhile, as one of the most important and widely traded chemical commodities, the demand for methanol is growing rapidly. The compound annual growth rate from 2016 to 2020 was 4.5%, mainly due to its important applications in industry and energy. There are various high-value-added chemical products downstream of methanol. Among them, methanol-to-olefins (MTO) is the most important application of methanol. Producing ethylene and propylene from methanol instead of petroleum resources is an important way to reduce dependence on petroleum. Secondly, formaldehyde is also a major chemical product produced from methanol. The global demand exceeds 30 million tons per year. It is an important basic chemical for producing thermosetting polymers, dyes, resins, and adhesives. Methyl tert-butyl ether (MTBE) synthesized from methanol through etherification reaction is widely used as a gasoline additive. In addition, acetic acid, dimethyl ether, and chloromethane are also important chemicals downstream of methanol. With the progress of technology, the consumption structure of methanol is developing towards more valuable methyl methacrylate, polyoxymethylene dimethyl ether, and p-xylene. In the context of the current global energy shortage, methanol is expected to become a substitute for fossil fuels and is one of the most promising renewable energy sources.

[0011] The methods for producing methanol industrially mainly include fixed-bed methanol synthesis process, membrane reaction process, supercritical-phase medium methanol synthesis process, trickle-bed methanol synthesis process, and slurry-bed methanol synthesis process, etc. These methods have their own advantages and disadvantages. For example, the high-pressure method has been basically phased out due to high requirements for equipment materials, large device investment, high energy consumption, and many side reactions. Currently, the methanol synthesis process in industrial operation is mainly gas-phase synthesis method. According to the operating pressure, it is divided into high-pressure method (20 - 30 MPa), medium-pressure method (10 - 20 MPa), and low-pressure method (5 - 10 MPa). The liquid-phase method is mainly divided into slurry-bed method and trickle-bed method.

[0012] In industrial production, the main process of the traditional electrocatalytic production of ethylene glycol and methanol from low-concentration carbon dioxide is to use an electrolytic cell to convert low-concentration carbon dioxide (<1000 ppm) into hydrogen-rich gas (>95% H 2 ). Then, the obtained hydrogen-rich gas is converted into methanol and ethylene glycol under catalysis. Specifically, the conversion rate of CO2 is usually between 80% and 90%; the conversion rate of methanol is generally higher than 75%, and the conversion rate of ethylene glycol is about 90%.

[0013] In this process, CO 2First, it is converted into carbonate. Generally, the hydrogenation process of carbonate involves ethylene carbonate (such as vinyl acetate or dimethyl carbonate) as an intermediate. However, different types of catalysts and operating conditions may affect the yield of the final product. Taking the use of copper-based catalysts as an example, in the hydrogenation process of ethylene carbonate, the preparation method of copper catalysts (such as impregnation method, co-precipitation method, and electrochemical reduction method), promoters (such as carbonates, alumina, sulfides, etc.), and reaction conditions (such as temperature, current density, and time) will all affect the selectivity of methanol.

[0014] The traditional industrial production of ethylene glycol and methanol by electrocatalytic reduction of low-concentration carbon dioxide has obvious advantages in terms of yield and environmental protection. Although this industrial method has a high yield, it is accompanied by high energy consumption, and the high cost of catalysts may limit its large-scale promotion. In addition, the existing process also includes multiple steps, which increases the equipment investment and operating costs, thus reducing the overall economy.

[0015] At this stage, while 2 significant progress has been made in the design and synthesis of catalysts for the direct hydrogenation of CO 2 to ethylene glycol, due to the difficulty in activating CO 2 as a thermodynamically stable molecule, direct hydrogenation often requires relatively high reaction pressures and temperatures. And due to its exothermic reaction characteristics, the equilibrium conversion rate is relatively low at high temperatures. These reasons jointly limit the further application of the reaction of direct hydrogenation of CO 2 to ethylene glycol. Therefore, the addition of CO 2 with ethylene oxide to form ethylene carbonate, and then the further hydrogenation of ethylene carbonate to produce ethylene glycol and methanol, provides a new route for the indirect conversion and utilization of CO 2 . The addition reaction of CO 2 with ethylene oxide as a method for industrial production of ethylene carbonate has a relatively mature process, and this route has an atomic economy of 100%, mild reaction conditions, high conversion rate and product selectivity, and is one of the most promising routes for the utilization of CO

[0016] Copper-based catalysts have excellent selective hydrogenation ability for C=O / C-O bonds and have been widely studied in the hydrogenation reaction of ethylene carbonate. Cu 0The synergistic mechanism of dissociative hydrogen adsorption and Cu⁺-activated C=O bond adsorption has been widely recognized. In-depth research has also been carried out on catalyst supports, promoters, and morphologies. However, current copper-based catalysts for ethylene carbonate hydrogenation still have problems such as too high a hydrogen-ester ratio and poor stability, which are urgent problems to be solved. Existing copper-silicon catalysts for ethylene carbonate hydrogenation often require a high hydrogen-ester ratio above 180 during the reaction. In industrial applications, too high a reaction hydrogen-ester ratio will lead to an increase in equipment costs and power costs.

[0017] To achieve large-scale applications of the green economy, efforts should focus on developing more efficient catalysts and optimizing reaction conditions, as well as exploring new reaction paths and improving catalyst stability. Therefore, the present invention provides a more environmentally friendly and economically viable production solution. Summary of the Invention

[0018] In view of the above-mentioned defects in the prior art, the present invention provides a device and process for producing ethylene glycol and co-producing methanol from carbon dioxide source ethylene carbonate under mild conditions. In this method, a porous-structured supported Cu-based solid catalyst modified with B is loaded in the reaction tower. 2 O 3 This process does not produce solid waste and can co-produce a variety of industrial products, with advantages such as mild conditions, high production efficiency, few by-products, and low costs.

[0019] To solve the above technical problems, the present invention adopts the following technical solutions:

[0020] A device for producing ethylene glycol and co-producing methanol from carbon dioxide source ethylene carbonate under mild conditions, comprising an ethylene carbonate rectification tower and an electrolysis tower. The bottom of the ethylene carbonate rectification tower is connected to the top of the reaction tower, the top of the electrolysis tower is connected to the bottom of the reaction tower, the bottom of the reaction tower is connected to a gas-liquid separator through a pipeline, the bottom of the gas-liquid separator is connected to an ethylene glycol rectification tower, and the top of the gas-liquid separator is connected to a cooling tower. The cooling tower is connected to a methanol recovery tower.

[0021] Furthermore, the bottom of the electrolysis tower is connected to a liquefaction tower, and the cooling tower is connected to the bottom of the reaction tower through a pipeline.

[0022] A process for producing ethylene glycol and co-producing methanol from carbon dioxide source ethylene carbonate under mild conditions using the above device, comprising the following steps:

[0023] a. Ethylene carbonate EC generated by the reaction of carbon dioxide in flue gas with ethylene oxide is rectified in the ethylene carbonate rectification tower. Green electricity is used to electrolyze water in the electrolysis tower to electrolyze oxygen and hydrogen. After separation, the oxygen enters the liquefaction tower for recovery, while the hydrogen enters the reaction tower.

[0024] b. The rectified ethylene carbonate and hydrogen enter the reaction tower, and a supported Cu-based solid catalyst modified with B is installed in the reaction tower. 2 O3 Under the catalysis of the modified supported Cu-based catalyst, a catalytic addition reaction occurs;

[0025] c. After the reaction product in step b is separated in the gas-liquid separator, the initially obtained crude ethylene glycol and gaseous methanol are obtained. The crude ethylene glycol is further purified in the ethylene glycol distillation column; in this process, the refined ethylene glycol is extracted as a product through the side line of the column body;

[0026] d. The gaseous methanol and unreacted hydrogen enter the cooling tower for cooling. The liquid methanol obtained after gas-liquid separation enters the methanol recovery column, and the remaining hydrogen is recycled into the reaction tower to participate in the reaction again.

[0027] Further, in step b, the hydrogen / ester ratio (H 2 / EC molar ratio) is 10 - 30, the hydrogen pressure is 2 - 4 MPa, the hydrogen flow rate is 40 - 80 ml / min, the liquid hourly space velocity (LHSV) of ethylene carbonate is 0.1 - 0.9 h -1 , the reaction temperature is 140 - 200 °C, the reaction time is 4 - 8 h, and the top operating reflux ratio of the reaction tower is (1 - 3):1. With B 2 O 3 The filling volume percentage of the modified supported Cu-based catalyst in the reaction tower is 10 - 50%. Preferably, the optimal reaction conditions are: reaction temperature 180 °C, hydrogen / ester ratio 20, hydrogen pressure 3 MPa, hydrogen flow rate 60 ml / min, liquid hourly space velocity (LHSV) of ethylene carbonate 0.6 h -1 , time 6 h. Under these conditions, the conversion rate of ethylene carbonate reaches 99.9%, the selectivity of ethylene glycol reaches 99.8%, and the selectivity of methanol reaches 71.0%.

[0028] Further, the catalyst in step b is prepared by the precipitation gel method to prepare catalyst additive manufacturing powder and a catalyst with a highly selective geometry is manufactured by selective laser sintering technology. The structural general formula of the catalyst is Cu-M / X-PG, where M is the promoter boron oxide, X is the carrier silica, PG is the preparation method of the precipitation gel method. The mass percentage content of metallic Cu in the catalyst is 5 - 75%, preferably 10 - 70%, the mass percentage content of the promoter M is 0.1 - 16%, preferably 0.5 - 11%, and the rest is the carrier; the particle size of metallic Cu in the catalyst additive manufacturing powder is 8 - 10 nm, the surface area of metallic Cu in the catalyst additive manufacturing powder is 65.5 - 79.8 m 2 / g, the specific surface area of Cu in the catalyst is 168 - 223 m 2 / g, the dispersion degree of Cu in the catalyst is 11.1 - 13.4%, and the surface area of zero-valent copper Cu 0 in the catalyst is 72.1 - 86.9 m2 / g.

[0029] Further, the preparation method of the catalyst in step b is as follows:

[0030] (1) Stir and mix the copper precursor salt with pure water to obtain a copper precursor salt solution;

[0031] (2) Drop the alkaline agent into the copper precursor salt solution obtained in (1) at a constant speed and stir vigorously until the pH value is greater than 10 to form a copper precursor salt suspension;

[0032] (3) Add the silicon source to the copper precursor salt suspension obtained in step (2) to disperse and stabilize the precipitate colloids in the copper precursor salt suspension to form a gel-like mixture;

[0033] (4) Cure, filter the gel-like mixture obtained in step (3), wash it thoroughly with hot water, dry it thoroughly, and then calcine it in an air atmosphere to obtain a catalyst precursor;

[0034] (5) Pre-calcine the catalyst precursor obtained in step (4) and then impregnate it in an aqueous solution of boric acid (H 3 BO 3 ), and then grind and screen it to obtain a catalyst powder;

[0035] (6) Put the catalyst powder obtained in step (5) into the powder cylinder of a selective sintering 3D printer, and evenly spread the catalyst powder on the printing build platform for preheating;

[0036] (7) Selectively sinter and cool the catalyst powder in step (6) according to the three-dimensional model established by the modeling software;

[0037] (8) Take out the finished catalyst product in step (7), and carry out powder removal, surface cleaning, grinding treatment and quality inspection.

[0038] Further, the catalyst can be activated before use: reduce it in a hydrogen atmosphere at 277 - 447 °C for 3 - 5 h, and the flow rate of the reducing gas is 20 - 60 ml / min to obtain an active catalyst.

[0039] Further, in order to improve the separation efficiency and product purity in step c, the ethylene glycol rectification is carried out under vacuum conditions, and the residual pressure inside the ethylene glycol rectification tower is controlled within the range of 0 - 5 KPa.

[0040] Further, the cooling temperature in step d is 50 - 60 °C.

[0041] The ethylene carbonate used as the carbon dioxide source in the present invention is obtained by the cycloaddition reaction of carbon dioxide and ethylene oxide. The carbon dioxide source is carbon dioxide in the industrial production flue gas after capture and purification, or carbon dioxide (CO2 with a purity of 90% or more). Ethylene oxide (EO) and carbon dioxide (CO 2 ) to prepare ethylene carbonate has formed a mature industrial system. For example, Chinese patents CN117599706A, CN117643857A, CN117463280A, and CN115385888A provide a variety of excellent industrial production devices; such as CN117299230A and CN117567437A, which provide a variety of recyclable and easily prepared reaction catalysts. Thus, it provides a carbon dioxide source and ethylene carbonate raw materials for the subsequent process.

[0042] Advantages of the present invention: In the present invention, ethylene carbonate as a carbon dioxide source and hydrogen produced by electrolyzing water with green electricity enter the reaction tower. Under the action of a solid catalyst, Cu 0 promotes the dissociation of hydrogen, and Cu + adsorbs and activates the ester carbonyl group in the ethylene carbonate molecule to carry out catalytic hydrogenation reaction. The crude ethylene glycol, gaseous methanol, and hydrogen are respectively fed into the ethylene glycol rectification tower and the cooling tower to obtain high-quality ethylene glycol and methanol products. The optimal reaction conditions are: reaction temperature 180 °C, hydrogen-to-ester ratio 20, hydrogen pressure 3 MPa, hydrogen flow rate 60 ml / min, and liquid hourly space velocity (LHSV) of ethylene carbonate 0.6 h -1 , time 6 h. Under these conditions, the conversion rate of ethylene carbonate reaches 99.9%, the selectivity of ethylene glycol reaches 99.8%, and the selectivity of methanol reaches 71.0%. The production method provided by the present invention has the advantages of mild conditions, high production efficiency, few by-products, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0044] Figure 1 is a schematic diagram of the device structure of this process flow.

[0045] Figure 2 is the reaction flow chart of this process flow.

[0046] Figure 3 is a broken line graph of the selectivity of ethylene glycol.

[0047] Figure 4 is a broken line graph of the selectivity of methanol.

[0048] Figure 5It is a comparison chart with the existing process flow (conversion rate of ethylene carbonate, selectivity of ethylene glycol, selectivity of methanol).

[0049] Figure 6 It is a comparison chart with the existing process flow (catalyst consumption, solid waste generation).

[0050] Figure 7 It is a comparison chart with the existing process flow (catalyst cost, solid waste treatment cost).

[0051] Appendix Figure 1 Markings: 1. Ethylene carbonate rectification tower, 2. Reaction tower, 3. Gas-liquid separator, 4. Ethylene glycol rectification tower, 5. Cooling tower, 6. Methanol recovery tower, 7. Electrolysis tower, 8. Liquefaction tower. Detailed implementation mode

[0052] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The purpose is to deepen the understanding rather than limit the protection scope. Parameters such as mass, reaction conditions, process parameters, etc. are only examples. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The experimental methods without specific conditions in the embodiments are usually carried out according to the conventional conditions and the conditions described in the manuals. General equipment, materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0053] Embodiment 1

[0054] As Figure 1 shown, a device for producing ethylene glycol and co-producing methanol from a carbon dioxide source of ethylene carbonate under mild conditions includes an ethylene carbonate rectification tower 1 and an electrolysis tower 7. The bottom of the ethylene carbonate rectification tower 1 is connected to the top of the reaction tower 2, the top of the electrolysis tower 7 is connected to the bottom of the reaction tower 2, the bottom of the reaction tower 2 is connected to the gas-liquid separator 3 through a pipeline, the bottom of the gas-liquid separator 3 is connected to the ethylene glycol rectification tower 4, the top of the gas-liquid separator 3 is connected to the cooling tower 5, the cooling tower 5 is connected to the methanol recovery tower 6, the bottom of the electrolysis tower 7 is connected to the liquefaction tower 8, and the cooling tower 5 is connected to the bottom of the reaction tower 2 through a pipeline.

[0055] Embodiment 2

[0056] As Figure 1 and Figure 2 shown, a process for producing ethylene glycol and co-producing methanol under mild conditions includes the following steps:

[0057] a. The ethylene carbonate EC generated by the reaction of carbon dioxide in the flue gas with ethylene oxide is rectified in the ethylene carbonate rectification tower 1. Green electricity is used in the electrolysis tower 7 to electrolyze water to electrolyze oxygen and hydrogen. After separation, the oxygen enters the liquefaction tower 8 for recovery, and the hydrogen enters the reaction tower 2;

[0058] b. The ethylene carbonate after rectification and hydrogen enter the reaction tower 2 at a molar ratio of 1:20. In the reaction tower 2, a supported Cu-based catalyst modified with B 2 O 3 undergoes a catalytic addition reaction under the catalysis of the modified supported Cu-based catalyst. Hydrogen is continuously introduced into the reaction tower at 2 MPa and a hydrogen flow rate of 60 ml / min, while ethylene carbonate enters the reaction tower 2 at a liquid hourly space velocity (LHSV) of 0.6 h -1 and reacts with the catalyst at 135 - 205 °C, specifically at 140, 160, 180, and 200 °C. The supported Cu-based catalyst modified with B 2 O 3 has a filling volume percentage of 30% in the reaction tower 2. The typical composition of the bottom of the tower is 60 - 80% ME and 20 - 40% EG;

[0059] c. After the reaction products in step b are separated in the gas-liquid separator 3, the initially obtained crude ethylene glycol and gaseous methanol are obtained. The crude ethylene glycol is further purified in the ethylene glycol rectification tower 4; during this process, the refined ethylene glycol is extracted as a product through the side line of the tower body;

[0060] d. The gaseous methanol and unreacted hydrogen enter the cooling tower 5 for cooling. The liquid methanol obtained after gas-liquid separation enters the methanol recovery tower 6, and the remaining hydrogen is recycled into the reaction tower 2 to participate in the reaction again.

[0061] In the reaction tower 2, the packing used is wire mesh structured packing with a pore size of 500 μm made of stainless steel to achieve efficient mass transfer between gas and liquid. Between these packing layers, a catalyst loading package with an entrained porous structure made of 316L stainless steel metal is installed to ensure the uniform distribution of catalyst particles and provide the necessary mechanical stability. The number of theoretical plates is maintained within the range of 40 - 60 to achieve the expected separation efficiency.

[0062] The glycol distillation column 4 is also filled with wire mesh structured packing with a pore size of 500 μm made of stainless steel, and the number of theoretical plates is 40 - 60. The bottom temperature of the column is controlled at 120 - 140 °C to ensure the best effect of the reaction and separation process. Preferably, the optimal temperature range for operation is 122 - 130 °C. The reflux ratio at the top of the column is adjusted within the range of 1 - 3. Preferably, the optimal reflux ratio range is 1.2 - 2.5 to improve the separation efficiency and product purity and achieve efficient component recovery. In normal operation, the reflux ratio at the top of the column is set to 1.5 to ensure the separation efficiency while optimizing the energy consumption and operating cost. To maintain suitable reflux and rectification conditions, the pressure at the top of the column is controlled at 1.2 KPa to achieve effective evaporation and separation of components. The pressure at the bottom of the column is higher, set at 3.6 kPa, to ensure sufficient driving force for liquid circulation and heat transfer and prevent potential safety problems caused by excessive pressure in the column.

[0063] The outlet temperature of the cooling tower 5 is controlled at 60 °C, and a spiral plate heat exchanger is used. For the methanol recovery column 6, wire mesh structured packing with a pore size of 500 μm made of stainless steel is also used to maintain consistent mass transfer efficiency. The designed number of theoretical plates of this column is between 20 - 30. The top temperature of the column is maintained within the range of 50 - 60 °C, and the bottom temperature is controlled at 130 - 140 °C, which is conducive to promoting the reaction in the column and the effective separation of components. At the bottom of the column, the typical composition of the material is 5.2% ME and 94.8% EG, ensuring the effective separation of the material and the high purity of the product and achieving a high-efficiency and high-selectivity separation effect.

[0064] In this embodiment, using B 2 O 3 The preparation process of the modified supported Cu-based solid catalyst is as follows: Weigh 15.00 g of copper nitrate trihydrate and dissolve it in 125 ml of distilled water in a beaker to obtain a copper nitrate solution. Slowly add 15 wt% NaOH solution dropwise and stir until pH > 10. After obtaining a suspension, add 12.40 g of 20% silica sol by mass to disperse and stabilize the precipitate particles, and then heat to 80 °C for aging for 3 h. Dry at 120 °C for 12 h, calcine in a muffle furnace at 550 °C in a nitrogen stream for 3 h, grind and sieve (60 - 80 mesh) to obtain a calcined sample.

[0065] Weigh 0.18 g of boric acid, add a certain amount of distilled water to make a solution, impregnate 4.30 g of the sieved calcined sample in equal volume, dry at 120 °C for 12 h, reduce and activate in a hydrogen atmosphere at 400 °C for 3 h to obtain a basic powder. Conduct additive manufacturing using selective sintering technology, establish a three-dimensional model with modeling software. After cooling the porous cube (side length 30 cm, porosity 65%, average pore diameter 3.5 cm), perform surface powder treatment and surface cleaning to obtain the catalyst.

[0066] Example 3

[0067] In the method for producing ethylene glycol and co-producing methanol from ethylene carbonate as a carbon dioxide source in this embodiment under mild conditions, the preparation device is the same as that in Example 1, and the difference in its preparation process from Example 2 is only that the ethylene carbonate and hydrogen after rectification enter Reaction Tower 2, and the hydrogen pressure for the catalytic addition reaction under the catalysis of the supported Cu-based catalyst modified with B 2 O 3 is 3 MPa, and other steps are the same as those in Example 2.

[0068] In Example 3, the preparation of the supported Cu-based catalyst modified with B 2 O 3 is the same as that in Example 2.

[0069] Example 4

[0070] In the method for producing ethylene glycol and co-producing methanol from ethylene carbonate as a carbon dioxide source in this embodiment under mild conditions, the preparation device is the same as that in Example 1, and the difference in its preparation process from Example 2 is only that the ethylene carbonate and hydrogen after rectification enter Reaction Tower 2, and the hydrogen pressure for the catalytic addition reaction under the catalysis of the supported Cu-based catalyst modified with B 2 O 3 is 4 MPa, and other steps are the same as those in Example 2.

[0071] In Example 4, the preparation of the supported Cu-based catalyst modified with B 2 O 3 is the same as that in Example 2.

[0072] The catalytic hydrogenation reactions in Examples 2, 3, and 4 were all carried out under the condition that the reaction time was 6 h. By regulating the reaction temperature and hydrogen pressure and conducting repeated experiments under the condition that the catalyst activity met the requirements, and taking the average value, the following results were obtained: See Appendix Figure 3 、 4 。

[0073] The calculation of the conversion rate of ethylene carbonate and the selectivities of ethylene glycol and methanol is based on the following formulas:

[0074]

[0075] Among them, n 0 (EC) is the molar amount of EC added before the reaction, n(EC) is the molar amount of EC remaining after the reaction, n(MeOH) is the molar amount of methanol produced by the reaction, and n(EG) is the molar amount of ethylene glycol produced by the reaction.

[0076] The experimental results show that the conversion rate of ethylene carbonate is greater than 99.5%, and reaches the highest 99.9% at 3 MPa and 180 °C. This indicates that the catalyst exhibits excellent catalytic activity and selectivity for the catalytic hydrogenation of ethylene carbonate, and is very beneficial to the separation and purification of products. Attached Figure 3 and 4 are the selectivity linear diagrams of ethylene glycol and methanol. The results show that appropriate high temperature and high pressure conditions are conducive to improving the selectivity of ethylene glycol and methanol. When the hydrogen pressure is 3 MPa and the temperature reaches 180 °C, the selectivity of ethylene glycol reaches the highest 99.8%, and the selectivity of methanol reaches 71.0%. This shows that appropriate high temperature and high pressure conditions are more conducive to the hydrogenation of ethylene carbonate to produce ethylene glycol and methanol. After 180 °C, the selectivity of ethylene glycol and methanol both decreases, which may be caused by the influence of temperature on the catalyst activity. When the hydrogen is increased to 4 MPa, although the selectivity of ethylene glycol and methanol both increases compared with 2 MPa, it slightly decreases compared with 180 °C. It is speculated that the possible reason is that the increase in hydrogen pressure intensifies other side reactions.

[0077] Taking the process flow of 40,000 tons of ethylene glycol produced annually as an example, the comparison of the technical route of the present invention with the process flow effect of the prior art is attached Figure 5 and 6 Figure 7. Process 1 is the process flow of the present invention; Process 2 is the process flow of the prior art. Specifically, the main method process for the traditional electrocatalytic production of ethylene glycol and methanol from low-concentration carbon dioxide in industrial production is to use an electrolytic cell to convert low-concentration carbon dioxide (<1000 ppm) into hydrogen-rich gas (>95% H 2 ). Then the obtained hydrogen-rich gas is converted into methanol and ethylene glycol under catalysis. Specifically, the conversion rate of CO 2 is usually between 80% and 90%; the conversion rate of methanol is generally higher than 75%, and the conversion rate of ethylene glycol is about 90%.

[0078] The production process provided by the present invention has the advantages of higher production efficiency, obtaining multiple industrial products at the same time, milder reaction conditions, etc., and also has the advantages of no solid waste generation, few by-products, and low cost. Combining Figures Figure 5 and 6 Figure 7, in the process flow of the present invention, the conversion rate of ethylene carbonate increases slightly, while the selectivity of ethylene glycol and methanol both increases significantly.

[0079] At the same time, the consumption of the catalyst used also decreases significantly, and the generation amount of solid waste decreases significantly. Except for the catalyst, basically no solid waste is generated. As a result, the consumption cost of the catalyst is greatly reduced, and the treatment cost of solid waste is also greatly reduced, which greatly reduces the treatment cost of the process flow.

[0080] In addition, the advantages of the solid catalyst used in the present invention compared with general homogeneous catalysts in aspects such as device construction, material storage, material transportation, etc. will not be elaborated here.

[0081] As described above, only some preferred embodiments of the present invention are provided. Any person skilled in the art may modify the technical solutions described above or modify them into equivalent technical solutions. Therefore, any simple modification or equivalent replacement made according to the technical solutions of the present invention falls within the scope of protection required by the present invention.

Claims

1. A device for producing ethylene glycol and methanol from ethylene carbonate as a carbon dioxide source under mild conditions, characterized in that: The invention comprises an ethylene carbonate distillation tower (1) and an electrolysis tower (7), wherein the bottom of the ethylene carbonate distillation tower (1) is connected to the top of a reaction tower (2), the top of the electrolysis tower (7) is connected to the bottom of the reaction tower (2), the bottom of the reaction tower (2) is connected to a gas-liquid separator (3) through a pipeline, the bottom of the gas-liquid separator (3) is connected to an ethylene glycol distillation tower (4), the top of the gas-liquid separator (3) is connected to a cooling tower (5), and the cooling tower (5) is connected to a methanol recovery tower (6).

2. The device for producing ethylene glycol and methanol from ethylene carbonate as a carbon dioxide source under mild conditions according to claim 1, characterized in that: The bottom of the electrolysis tower (7) is connected to the liquefaction tower (8), and the cooling tower (5) is connected to the bottom of the reaction tower (2) via a pipeline.

3. A process for producing ethylene glycol and methanol under mild conditions using the device according to claim 1 or 2, characterized in that The following steps are involved: a. Ethylene carbonate EC generated by the reaction of carbon dioxide in the flue gas with ethylene oxide is distilled in an ethylene carbonate distillation tower (1), and green electricity is used in an electrolysis tower (7) to electrolyze water to produce oxygen and hydrogen. After separation, the oxygen enters a liquefaction tower (8) for recovery, while the hydrogen enters a reaction tower (2); b. The ethylene carbonate and hydrogen after distillation enter the reaction tower (2), and a catalytic addition reaction occurs under the catalytic action of a supported Cu-based catalyst modified with B2O3 placed in the reaction tower (2); c. After the reaction product of step b is separated in the gas-liquid separator (3), crude ethylene glycol and gaseous methanol are initially obtained, and the crude ethylene glycol is further purified in the ethylene glycol distillation tower (4); in this process, refined ethylene glycol is extracted as a product through the side line of the tower body; d. The gaseous methanol and unreacted hydrogen enter the cooling tower (5) for cooling. The liquid methanol obtained after gas-liquid separation enters the methanol recovery tower (6). The remaining hydrogen circulates into the reaction tower (2) to participate in the reaction again.

4. The process for producing ethylene glycol and methanol under mild conditions according to claim 3, characterized in that: In step b, the hydrogen-to-ester ratio (H2 / EC molar ratio) is 10-30, the hydrogen pressure is 2-4 MPa, the hydrogen flow rate is 40-80 ml / min, and the ethylene carbonate liquid hourly space velocity (LHSV) is 0.1-0.9 h -1 , reaction temperature is 140-200°C, reaction time is 4-8h, the top operating reflux ratio of the reaction tower is (1-3):1, and the loading volume percentage of the supported Cu-based catalyst modified with B2O3 in the reaction tower is 10-50%.

5. The process for producing ethylene glycol and methanol under mild conditions according to claim 4, characterized in that: The optimal reaction conditions are: reaction temperature 180℃, hydrogen ester ratio 20, hydrogen pressure 3MPa, hydrogen flow rate 60ml / min, ethylene carbonate liquid hourly space velocity (LHSV) 0.6h -1 , time 6h, under this condition, the ethylene carbonate conversion rate reached 99.9%, the ethylene glycol selectivity reached 99.8%, and the methanol selectivity reached 71.0%.

6. The process for producing ethylene glycol and methanol under mild conditions according to claim 3, characterized in that: In the step b, the catalyst is prepared by a precipitation gel method to prepare a catalyst additive manufacturing powder and a catalyst with a highly selective geometric shape is manufactured by a selective laser sintering technology. The general structural formula of the catalyst is Cu-M / X-PG, where M is an auxiliary agent boron oxide, X is a carrier silica, and PG is a preparation method by a precipitation gel method. The mass percentage of metal Cu in the catalyst is 5-75%, the mass percentage of the auxiliary agent M is 0.1-16%, and the rest is a carrier; the metal Cu particle size in the catalyst additive manufacturing powder is 8-10nm, the surface area of ​​the metal Cu in the catalyst additive manufacturing powder is 65.5-79.8m² / g, the specific surface area of ​​Cu in the catalyst is 168-223m² / g, the dispersion of Cu in the catalyst is 11.1-13.4%, and the zero-valent copper Cu in the catalyst is 1.3%. 0 The surface area is 72.1~86.9m² / g.

7. The process for producing ethylene glycol and methanol under mild conditions according to claim 6, characterized in that: The preparation method of the catalyst in step b is as follows: (1) stirring and mixing a copper precursor salt and pure water to obtain a copper precursor salt solution; (2) adding an alkaline agent dropwise to the copper precursor salt solution obtained in (1) at a constant rate and stirring vigorously until the pH value is greater than 10 to form a copper precursor salt suspension; (3) adding a silicon source to the copper precursor salt suspension obtained in step (2) to disperse and stabilize the precipitated colloidal particles in the copper precursor salt suspension to form a gel-like mixture; (4) aging and filtering the gelatinous mixture obtained in step (3), washing it with hot water, and then drying it and calcining it in an air atmosphere to obtain a catalyst precursor; (5) Pre-calcining the catalyst precursor obtained in step (4) and immersing it in an aqueous solution of boric acid (H3BO3), and then grinding and sieving to obtain a catalyst powder; (6) placing the catalyst powder obtained in step (5) into a powder cylinder of a selective sintering 3D printer, and evenly spreading the catalyst powder on the printer build platform for preheating; (7) selectively sintering and cooling the catalyst powder of step (6) by establishing a three-dimensional model according to a modeling software; (8) Take out the finished catalyst product obtained in step (7), remove the powder, clean the surface, polish it, and inspect its quality.

8. The process for producing ethylene glycol and methanol under mild conditions according to claim 6, characterized in that: The catalyst can be activated before use: reduction in a hydrogen atmosphere at 277-447°C for 3-5 hours with a reducing gas flow rate of 20-60 ml / min to obtain an active catalyst.

9. The process for producing ethylene glycol and methanol under mild conditions according to claim 3, characterized in that: In order to improve the separation efficiency and product purity, the ethylene glycol distillation in step c is performed under vacuum conditions, and the residual pressure inside the ethylene glycol distillation tower is controlled within the range of 0 to 5 KPa.

10. The process for producing ethylene glycol and methanol under mild conditions according to claim 3, characterized in that: The cooling temperature in step d is 50-60°C.

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