Method for preparing ethylene oxide by coupling methane oxidative coupling reaction and ethylene epoxidation reaction

Abstract

The invention relates to the technical field of methane oxidative coupling and ethylene epoxidation, and discloses a method for preparing ethylene oxide by coupling a methane oxidative coupling reaction and an ethylene epoxidation reaction, the method comprises the following steps: in the presence of an oxidative coupling catalyst, methane is subjected to an oxidative coupling reaction to obtain a first gas-phase product containing ethylene, CO2 and CO; (2) contacting the first gas-phase product with an oxidant to enable CO in the first gas-phase product to be subjected to oxidation reaction to generate CO2, and then removing at least part of CO2 to obtain a second gas-phase product; wherein the volume content ratio of carbon dioxide to ethylene in the second gas-phase product is (0.1-0.3): 1; and (3) contacting the second gas-phase product with a catalyst, so that ethylene in the second gas-phase product is subjected to epoxidation reaction. According to the method, the additional value of the final product is improved, the step of separating the product of the methane oxidative coupling reaction is omitted, and the energy consumption and the cost of separation are greatly reduced.

Description

Technical Field

[0001] This invention relates to the fields of methane oxidative coupling and ethylene epoxidation, specifically, to a method for preparing ethylene oxide by coupling a methane oxidative coupling reaction with an ethylene epoxidation reaction. Background Technology

[0002] The oxidative coupling of methane to produce ethylene and ethane is one of the most challenging and closely watched research topics in the field of catalysis due to its academic significance and potential for enormous economic value. Since its initial report in 1982 by Keller and Bhasin, it has been a focus of attention in catalysis, the chemical industry, and the oil and gas sector. Methane oxidative coupling is an exothermic reaction, producing mainly ethylene, ethane, and water, along with carbon monoxide and carbon dioxide from further oxidation. This technology is characterized by its good atom economy and environmental friendliness, making it a target of intense research by scientific researchers and major corporations for the past four decades. The separation of the products, such as ethylene, ethane, and methane, typically employs physical methods, which are difficult and costly.

[0003] Ethylene oxide (EO) is one of the simplest cyclic ethers, belonging to the heterocyclic class of compounds, and is an important petrochemical product. Ethylene oxide is a colorless, transparent liquid at low temperatures. It is the second-generation chemical disinfectant after formaldehyde and is currently one of the most important components of the four major low-temperature sterilization technologies (low-temperature plasma, low-temperature formaldehyde vapor, ethylene oxide, and glutaraldehyde). Summary of the Invention

[0004] The purpose of this invention is to overcome the high separation cost of methane oxidative coupling reaction products in existing technologies. It organically combines the methane oxidative coupling reaction with the ethylene epoxidation to produce ethylene oxide. This reduces separation process operations and lowers the cost of separating methane oxidative coupling reaction products. Furthermore, it allows for the direct use of methane oxidative coupling reaction products for ethylene epoxidation to produce ethylene oxide, increasing the added value of the product. The inventors have also discovered that removing CO from the methane oxidative coupling reaction products while controlling the CO2 concentration within a specific range can promote the ethylene epoxidation reaction, resulting in higher ethylene conversion and ethylene oxide selectivity.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing ethylene oxide by coupling a methane oxidative coupling reaction with an ethylene epoxidation reaction, the method comprising the following steps:

[0006] (1) In the presence of an oxidative coupling catalyst, methane undergoes an oxidative coupling reaction to obtain a first gaseous product containing ethylene, CO2 and CO.

[0007] (2) The first gaseous product is contacted with an oxidant to oxidize the CO in the first gaseous product to generate CO2, and then at least part of the CO2 is removed to obtain the second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.1-0.3:1;

[0008] (3) The second gaseous product is brought into contact with the catalyst to cause the ethylene in the second gaseous product to undergo an epoxidation reaction.

[0009] The above technical solution has achieved the following beneficial effects:

[0010] This invention organically combines the methane oxidative coupling reaction with the ethylene oxidation reaction to prepare ethylene oxide, which not only increases the added value of the final product, but also saves the product separation step of the methane oxidative coupling reaction, greatly reducing the energy consumption and cost of separation.

[0011] This invention promotes the ethylene epoxidation reaction by removing CO from the products of the methane oxidative coupling reaction and controlling the CO2 concentration within a specific range, thereby achieving a higher ethylene conversion rate and ethylene oxide selectivity.

[0012] In a preferred embodiment, the present invention employs a silver-supported catalyst with a rod-like structure, which can effectively reduce the reaction temperature of ethylene epoxidation and obtain higher ethylene conversion and ethylene oxide selectivity. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The first aspect of this invention provides a method for preparing ethylene oxide by coupling a methane oxidative coupling reaction with an ethylene epoxidation reaction, the method comprising the following steps:

[0015] (1) In the presence of an oxidative coupling catalyst, methane undergoes an oxidative coupling reaction to obtain a first gaseous product containing ethylene, CO2 and CO.

[0016] (2) The first gaseous product is contacted with an oxidant to oxidize the CO in the first gaseous product to generate CO2, and then at least part of the CO2 is removed to obtain the second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.1-0.3:1;

[0017] (3) The second gaseous product is brought into contact with the catalyst to cause the ethylene in the second gaseous product to undergo an epoxidation reaction.

[0018] This invention does not specifically limit the catalyst for ethylene epoxidation; it can be any catalyst commonly used in the field for ethylene epoxidation, such as a supported catalyst in step (3). Preferably, the supported catalyst comprises Ag and a support, and the Ag has a rod-like structure. The inventors of this invention have further discovered that using an Ag-supported catalyst with a rod-like structure not only improves ethylene conversion and ethylene oxide selectivity but also further reduces the reaction temperature of ethylene epoxidation. More preferably, the length of the rod-like structure is 10-200 nm, more preferably 50-200 nm; and the diameter is 2-10 nm, more preferably 2-8 nm.

[0019] According to the present invention, in order to further improve the ethylene conversion rate and the selectivity of ethylene oxide, preferably, the content of Ag is 5-30% by weight, more preferably 13-25% by weight, based on the total weight of the supported catalyst. In the present invention, the content of Ag in the supported catalyst is calculated by the amount of feed.

[0020] According to the present invention, preferably, the support in the supported catalyst is alumina.

[0021] According to the present invention, in order to further improve the ethylene conversion rate and the selectivity of ethylene oxide, preferably, the supported catalyst further includes an alkaline earth metal promoter; more preferably, the alkaline earth metal promoter includes at least one selected from Mg, Ca, Sr, and Ba; even more preferably, the content of the alkaline earth metal promoter is 0.001-0.05% by weight, more preferably 0.003-0.04% by weight, based on the total weight of the supported catalyst. The content of the alkaline earth metal promoter in the supported catalyst is calculated by the feed amount.

[0022] This invention also provides a method for preparing a supported catalyst, the method comprising the following steps:

[0023] (a) Preparation of rod-shaped silver nanoparticles: A suspension containing sucrose, sodium chloride, ammonia, silver precursor and optional polyvinylpyrrolidone was subjected to a hydrothermal reaction.

[0024] (b) Loading of the active component: The impregnation solution containing the hydrothermal reaction product (silver nanorods) is brought into contact with the support, then dried under vacuum, and then calcined. Preferably, the amount of hydrothermal reaction product (silver nanorods) is 0.1-0.5 g relative to each gram of support.

[0025] According to the preparation method of the supported catalyst of the present invention, preferably, in step (a), the amount of sucrose used is 4000-8000g, the amount of sodium chloride is 0.1-0.8mol, the amount of ammonia is 2000-5000g, and the amount of polyvinylpyrrolidone is 3000-7000g, relative to each mole of silver precursor.

[0026] According to the preparation method of the supported catalyst of the present invention, preferably, in step (a), the hydrothermal reaction conditions include: a temperature of 150-200°C and a time of 40-60 h.

[0027] According to the preparation method of the supported catalyst of the present invention, preferably, in step (a), the suspension containing sucrose, sodium chloride, ammonia, silver precursor, and optionally polyvinylpyrrolidone is obtained by: mixing sucrose, optionally polyvinylpyrrolidone, and water to obtain a mixture; then adding an aqueous sodium chloride solution dropwise to the mixture, followed by adding an aqueous ammonia solution and an aqueous silver precursor solution. The order of adding the aqueous ammonia solution and the aqueous silver precursor solution is not particularly limited; for example, the aqueous ammonia solution and the aqueous silver precursor solution can be added simultaneously, or the ammonia solution can be added first followed by the aqueous silver precursor solution, or the aqueous silver precursor solution can be added first followed by the ammonia solution. The concentration of the aqueous sodium chloride solution can be 0.01-0.05 mol / L. The concentration of the ammonia solution can be 10-30 wt%. The concentration of the aqueous silver precursor solution can be 0.01-0.05 mol / L. The silver precursor can be silver nitrate.

[0028] According to the method for preparing the supported catalyst of the present invention, preferably, step (a) further includes: separating the solid-liquid mixture obtained by the hydrothermal reaction to obtain a solid, and washing and drying the solid. After drying, nanorod-shaped silver is obtained. The washing agent used is water and / or ethanol; the drying conditions include: a temperature of 100-120°C and a time of 20-50 h.

[0029] According to the preparation method of the supported catalyst of the present invention, preferably, in step (b), the impregnation solution further includes an alkali metal promoter precursor, polyvinylpyrrolidone, and a monohydric alcohol. Specifically, relative to each gram of support, the amount of alkaline earth metal promoter precursor is 0.00001-0.01 g, the amount of polyvinylpyrrolidone is 0.05-0.2 g, and the amount of monohydric alcohol is 0.01-0.05 g.

[0030] According to the method for preparing the supported catalyst of the present invention, preferably, in step (b), the impregnation solution is obtained by mixing nanorod-shaped silver, an optional alkaline earth metal promoter precursor, an optional polyvinylpyrrolidone, and an optional monohydric alcohol with water to prepare the impregnation solution. More preferably, in step (b), the amount of water used is 1-3 g relative to each gram of support. The alkaline earth metal promoter precursor can be at least one of the alkaline earth metal nitrates, sulfates, chlorides, and carbonates, as long as it can provide an alkaline earth metal element.

[0031] According to the present invention, preferably, in step (3), the conditions for the epoxidation reaction of ethylene include: a temperature of 220-250°C, a pressure of 1-2.1 MPa, and a space velocity (HV) of ethylene of 7000-10000 h⁻¹. -1 .

[0032] According to the present invention, preferably, step (3) further includes introducing oxygen, wherein the volume ratio of oxygen to ethylene is 0.2-0.5:1.

[0033] According to the present invention, preferably, step (3) further includes: mixing the second gaseous product with the inhibitor and then contacting it with the catalyst.

[0034] According to the present invention, the inhibitor can be a commonly used inhibitor in the art, preferably, the inhibitor is dichloroethane. More preferably, the volume ratio of the inhibitor to ethylene is 0.002-0.005:1.

[0035] In this invention, methane can act as a stabilizing gas in the ethylene epoxidation reaction. When the methane content in the first product is low, the method may further include: adding methane in step (3). Typically, the amount of methane added is such that the molar ratio of ethylene to methane in the ethylene epoxidation reaction system is 1:3-40.

[0036] According to the present invention, the type of oxidative coupling catalyst is not particularly limited, and can be a methane oxidative coupling catalyst commonly used in the art. Preferably, the oxidative coupling catalyst includes at least one selected from NaWMn / SiO2, NaWMn / TiO2, NaWMn / BaTiO3, lanthanum oxide, lanthanum oxycarbonate, and lanthanum hydroxide. The source of the oxidative coupling catalyst is not particularly limited; for example, it can be prepared according to methods described in the literature or obtained by purchase. The embodiments of the present invention are illustrated by way of NaWMn / SiO2, lanthanum oxide, and lanthanum oxycarbonate, but the present invention is not limited thereto. For example, the NaWMn / SiO2 catalyst is prepared according to the method in CN112536029A. For example, in the NaWMn / SiO2 catalyst, the content of Na2WO4 is 1-6% based on the weight of silica, and the content of manganese oxide (calculated as Mn) is 0.1-6%. The NaWMn / SiO2 catalyst may also include samarium oxide, and the content of samarium oxide is 0.001-10% by weight based on the weight of silica. For example, the lanthanum oxycarbonate catalyst is prepared according to the method in CN113797949A. For example, this lanthanum oxycarbonate catalyst has a rod-shaped nanostructure; the length of the lanthanum oxycarbonate catalyst is 120-160 nm, preferably 125-160 nm; the diameter is 18-25 nm, preferably 20-25 nm; the aspect ratio of the lanthanum oxycarbonate catalyst is 2-10, preferably 4-8; and the specific surface area is 50-500 m². 2 / g, preferably 65-300m 2 / g; pore volume is 0.3-1.5ml / g, preferably 0.5-1ml / g; pore size is 10-20nm, preferably 13-18nm.

[0037] According to the present invention, preferably, the conditions for the oxidative coupling reaction include: a temperature of 450-900°C, a molar ratio of methane to oxygen of 3-8:1, and a reaction space velocity of 10000-100000 ml / gh based on methane.

[0038] According to the present invention, preferably, the ethylene content in the first gaseous product is 2-5% by volume, and the CO content is 2-10% by volume.

[0039] According to the present invention, preferably, the first gaseous product further includes methane, ethane and CO2; wherein the content of methane in the first gaseous product is 50-90% by volume, the content of ethane is 2-10% by volume, and the content of CO2 is 4-25% by volume.

[0040] According to the present invention, preferably, step (1) further includes: cooling the product of the oxidative coupling reaction of methane to remove water.

[0041] In this invention, the product obtained by the oxidative coupling reaction of methane may also contain small amounts of propane, propylene, etc., which can be removed by cooling.

[0042] In this invention, the first gaseous product may also include oxygen, with an oxygen content of less than 0.5% by volume.

[0043] According to the present invention, the oxidant can be any oxidant capable of causing CO to undergo an oxidation reaction, but preferably, under the action of the oxidant, methane, ethane, and ethylene in the first gas phase product do not undergo an oxidation reaction. Preferably, the oxidant is copper oxide.

[0044] According to the present invention, preferably, the conditions for contacting the first gaseous product with the oxidant include: a temperature of 200-500°C, and a molar ratio of carbon monoxide to oxidant in the first gaseous product of 1:1-1.2.

[0045] According to the present invention, preferably, the method further includes: separating the ethylene oxide generated in step (3) and returning the unreacted ethylene to step (3).

[0046] According to the present invention, preferably, the method further includes: separating the ethylene oxide generated in step (3) and returning the unreacted methane to step (1).

[0047] The present invention will be described in detail below through embodiments. In the following embodiments,

[0048] The NaWMn / SiO2 catalyst was prepared according to the method of Comparative Example 1 in CN112536029A;

[0049] Lanthanum oxide is a commercially available product of Puyang Jinxiang Industrial Co., Ltd., CAS1312-81-8;

[0050] The nano-lanthanum oxycarbonate was prepared according to Example 1 in CN113797949A.

[0051] The method for calculating ethylene conversion rate is as follows:

[0052] Ethylene conversion rate = Amount of ethylene consumed in the reaction / Initial amount of ethylene × 100%;

[0053] The method for calculating the selectivity of ethylene oxide is as follows:

[0054] Ethylene oxide selectivity = Amount of ethylene consumed to produce ethylene oxide / Total amount of ethylene consumed × 100%.

[0055] Preparation Example 1

[0056] This preparation example illustrates the preparation method of supported catalysts.

[0057] (1) Weigh 18g of sucrose and 15g of polyvinylpyrrolidone (PVP, molecular weight 58000), add 40g of deionized water and mix until the solution is clear; add 40ml of 0.03mol / L sodium chloride aqueous solution to the clear solution and stir at high speed for 1h, then add 10g of 20wt% ammonia water, and then add 150ml of 0.03mol / L silver nitrate aqueous solution to the solution at a rate of 5ml / min to obtain a milky white suspension. Transfer the suspension to a hydrothermal reactor lined with polytetrafluoroethylene and keep it at 180℃ for 48h. After cooling to room temperature, separate the solid by high-speed centrifugation. Wash the solid 3 times with deionized water and 3 times with anhydrous ethanol, place it in an oven and keep it at 120℃ for 24h to prepare nanorod-shaped silver.

[0058] (2) Add 2g of polyvinylpyrrolidone, 0.002g of barium nitrate, 50g of deionized water, 1g of ethanol, and 5g of the nanorod-shaped silver obtained in step (1) to a stirred glass flask to prepare an impregnation solution for later use. Thoroughly mix 25g of the alumina support with the impregnation solution and place it in a vacuum-capable container. Evacuate the container to a vacuum level below 5mmHg and maintain the temperature at 120℃. Continue evacuation and stirring for 5 hours. Heat the dried solid in an air stream at 300℃ for 10 minutes, then cool it to obtain the rod-shaped silver-supported catalyst.

[0059] Preparation Example 2

[0060] This preparation example illustrates the preparation method of supported catalysts.

[0061] (1) Weigh 18g of sucrose and 15g of polyvinylpyrrolidone (PVP, molecular weight 58000), add 80g of deionized water and stir until clear. Add 30ml of 0.05mol / L sodium chloride aqueous solution dropwise to the clear solution and stir at high speed for 1h. Then add 10g of 20wt% ammonia water, and then add 125ml of 0.02mol / L silver nitrate aqueous solution dropwise at a rate of 4ml / min until a milky white suspension is obtained. Transfer the suspension to a hydrothermal reactor lined with polytetrafluoroethylene and keep it at 160℃ for 60h. After cooling to room temperature, separate the solid by high-speed centrifugation. Wash the solid three times with deionized water and three times with anhydrous ethanol, and place it in an oven at 100℃ for 48h. Nanorod-shaped silver is prepared.

[0062] (2) Prepare an impregnation solution by adding 2g of polyvinylpyrrolidone, 0.006g of strontium nitrate, 50g of deionized water, 1g of ethanol, and 6g of silver nanorods to a stirred glass flask. Mix 25g of alumina support with the impregnation solution and place the mixture in a vacuum-supported container. Evacuate the container to a vacuum level below 5mmHg and maintain the temperature at 120℃. Continue evacuation and stirring for 5 hours. Heat the dried solid in a 300℃ air stream for 10 minutes, then cool to obtain the silver nanorod-supported catalyst.

[0063] Preparation Example 3

[0064] This preparation example illustrates the preparation method of supported catalysts.

[0065] (1) Weigh 18g of sucrose and 16g of polyvinylpyrrolidone (PVP, molecular weight 58000), add 75g of deionized water and stir until clear. Add 40ml of 0.03mol / L sodium chloride aqueous solution dropwise to the clear solution and stir at high speed for 1h. Then add 10g of 20wt% ammonia water and add 100ml of 0.03mol / L silver nitrate aqueous solution dropwise at a rate of 2ml / min to obtain a milky white suspension. Transfer the suspension to a hydrothermal reactor lined with polytetrafluoroethylene and keep it at 200℃ for 48h. After cooling to room temperature, separate the solid by high-speed centrifugation. Wash the solid three times with deionized water and three times with anhydrous ethanol, and place it in an oven at 120℃ for 24h. Nanorod-shaped silver is prepared.

[0066] (2) Prepare an impregnation solution by adding 4g of polyvinylpyrrolidone, 0.06g of magnesium nitrate, 60g of deionized water, 1g of ethanol, and 4.5g of nanorod-shaped silver to a stirred glass flask. Mix 30g of alumina support with the impregnation solution and place the mixture in a vacuum-supported container. Evacuate the container to a vacuum level below 5mmHg and maintain the temperature at 120℃. Continue evacuation and stirring for 5 hours. Heat the dried solid in a 300℃ air stream for 10 minutes, then cool to obtain the rod-shaped silver-supported catalyst.

[0067] Preparation Example 4

[0068] This preparation example illustrates the preparation method of supported catalysts.

[0069] (1) Weigh 18g of sucrose and 16g of polyvinylpyrrolidone (PVP, molecular weight 58000), add 80g of deionized water and stir until clear. Add 40ml of 0.03mol / L sodium chloride aqueous solution dropwise to the clear solution and stir at high speed for 1h. Then add 10g of 20wt% ammonia water and add 100ml of 0.03mol / L silver nitrate aqueous solution dropwise at a rate of 2ml / min to obtain a milky white suspension. Transfer the suspension to a hydrothermal reactor lined with polytetrafluoroethylene and keep it at 160℃ for 48h. After cooling to room temperature, separate the solid by high-speed centrifugation. Wash the solid three times with deionized water and three times with anhydrous ethanol, and place it in an oven at 120℃ for 24h. Nanorod-shaped silver is prepared.

[0070] (2) Prepare an impregnation solution by adding 4g of polyvinylpyrrolidone, 0.06g of calcium nitrate, 60g of deionized water, 1g of ethanol, and 9g of silver nanorods to a stirred glass flask. Mix 30g of alumina support with the impregnation solution and place the mixture into a vacuum-supported container. Evacuate the container to a vacuum level below 5mmHg and maintain the temperature at 120℃. Continue evacuation and stirring for 5 hours. Heat the dried solid in a 300℃ air stream for 10 minutes, then cool to obtain the silver nanorod-supported catalyst.

[0071] Preparation Example 5

[0072] The procedure was carried out according to the method of Preparation Example 4, except that calcium nitrate was not added.

[0073] Preparation Example 6

[0074] Add 10g of silver nitrate, 10g of 20wt% ammonia, 4g of polyvinylpyrrolidone, 5g of ethanol, and an appropriate amount of deionized water to a stirred glass flask to prepare a 100g impregnation solution. Mix 30g of alumina support with the impregnation solution and place the mixture into a vacuum-supported container. Evacuate the container to a vacuum level below 5mmHg and maintain the temperature at 120℃. Continue evacuation and stirring for 5 hours. Heat the dried solid in a stream of air at 300℃ for 10 minutes, then cool to obtain the rod-shaped silver-supported catalyst.

[0075] Test Example 1

[0076] The structure of the nanorod-shaped silver used in the above supported catalyst was obtained by scanning electron microscopy (SEM). The average value was taken after measuring 5-7 samples in the SEM field of view. The length and diameter of the rod-shaped nanostructure are shown in Table 1.

[0077] Table 1

[0078]

[0079] Example 1

[0080] (1) Methane Oxidative Coupling Reaction: Methane and oxygen were introduced into a fixed-bed reactor packed with an oxidative coupling catalyst (NaWMn / SiO2) to carry out a methane oxidative coupling reaction to obtain the methane oxidative coupling reaction product. The reaction temperature was 830℃, the molar ratio of methane to oxygen was 3, and the reaction space velocity (USV) based on methane was 20000 ml / gh. The methane oxidative coupling reaction product was cooled to 4℃, and water was removed from the product to obtain the first gaseous product. The first gaseous product contained methane, ethane, ethylene, CO, and CO2. The contents of each component are shown in Table 2.

[0081] (2-1) Removal of CO: The first gaseous product is contacted with an oxidant (copper oxide) at 500°C to oxidize the CO in the first gaseous product to generate CO2. The molar ratio of CO to oxidant is 1:1.

[0082] (2-2) Removing at least part of CO2: The product obtained in step (2-1) is passed into an alkaline solution (1 mol / L sodium hydroxide solution) to remove at least part of the CO2, and water is removed by a condenser at 4°C to obtain a second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.1:1.

[0083] (3) Ethylene epoxidation reaction: The second gaseous product was mixed with an inhibitor (dichloroethane) and oxygen to obtain a mixed gas. The mixed gas was then contacted with the supported catalyst obtained in Preparation Example 1 to cause the ethylene in the second gaseous product to undergo an epoxidation reaction to generate ethylene oxide. The volume ratio of the inhibitor to ethylene was 0.005:1, the volume ratio of oxygen to ethylene was 0.2:1, and the conditions for the ethylene epoxidation reaction included: a temperature of 225°C, a pressure of 1 MPa, and a space velocity of 7000 h⁻¹ (based on ethylene). -1 The ethylene oxide produced by the epoxidation reaction of ethylene is collected after condensation. The methane in the collected product is returned to the methane oxidative coupling reaction in step (1), while the unreacted ethylene is returned to the ethylene epoxidation reaction in step (3). The conversion rate of ethylene and the selectivity of ethylene oxide are shown in Table 3.

[0084] Example 2

[0085] (1) Methane Oxidative Coupling Reaction: Methane and oxygen were introduced into a fixed-bed reactor packed with an oxidative coupling catalyst (lanthanum oxide) to carry out a methane oxidative coupling reaction to obtain the methane oxidative coupling reaction product. The reaction temperature was 750℃, the molar ratio of methane to oxygen was 4, and the reaction space velocity (USV) based on methane was 50,000 ml / gh. The methane oxidative coupling reaction product was cooled to 4℃, and water was removed from the product to obtain the first gaseous product. The first gaseous product contained methane, ethane, ethylene, CO, and CO2. The contents of each component are shown in Table 2.

[0086] (2-1) CO removal: The first gaseous product is contacted with an oxidant (copper oxide) at 400°C to oxidize the CO in the first gaseous product to generate CO2, thus obtaining the second gaseous product. The molar ratio of carbon monoxide to oxidant in the first gaseous product is 1:1.1.

[0087] (2-2) Removal of at least part of CO2: The product obtained in step (2-1) is passed into an alkaline solution (1 mol / L AMP (1-amino-2-methyl-2-propanol) solution) to remove at least part of the CO2, and water is removed by condensing in a 4°C condenser to obtain a second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.2:1.

[0088] (3) The second gaseous product was mixed with an inhibitor (dichloroethane) and oxygen to obtain a mixed gas. The mixed gas was then contacted with the supported catalyst obtained in Preparation Example 2 to cause the ethylene in the second gaseous product to undergo an epoxidation reaction to generate ethylene oxide. The volume ratio of the inhibitor to ethylene was 0.002:1, the volume ratio of oxygen to ethylene was 0.3:1, and the conditions for the epoxidation reaction of ethylene included: a temperature of 230°C, a pressure of 1.5 MPa, and a space velocity of 8000 h⁻¹ (based on ethylene). -1 The ethylene oxide produced by the epoxidation reaction of ethylene is collected after condensation. The methane in the collected product is returned to the methane oxidative coupling reaction in step (1), while the unreacted ethylene is returned to the ethylene epoxidation reaction in step (3). The conversion rate of ethylene and the selectivity of ethylene oxide are shown in Table 3.

[0089] Example 3

[0090] (1) Methane Oxidative Coupling Reaction: Methane and oxygen were introduced into a fixed-bed reactor packed with an oxidative coupling catalyst (nano-lanthanum oxycarbonate) to carry out the methane oxidative coupling reaction and obtain the methane oxidative coupling reaction product. The reaction temperature was 550℃, the molar ratio of methane to oxygen was 8, and the reaction space velocity (USV) based on methane was 200,000 ml / gh. The methane oxidative coupling reaction product was cooled to 4℃, and water was removed from the product to obtain the first gaseous product. The first gaseous product contained methane, ethane, ethylene, CO, and CO2. The contents of each component are shown in Table 2.

[0091] (2-1) CO removal: The first gaseous product is contacted with an oxidant (copper oxide) at 400°C to oxidize the CO in the first gaseous product to generate CO2, thus obtaining the second gaseous product. The molar ratio of carbon monoxide to oxidant in the first gaseous product is 1:1.

[0092] (2-2) Removing at least part of CO2: The product obtained in step (2-1) is passed into an alkaline solution (1 mol / L AMP solution) to remove at least part of the CO2, and water is removed by a condenser at 4°C to obtain a second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.3:1.

[0093] (3) The second product was mixed with an inhibitor (dichloroethane) and oxygen to obtain a mixed gas. The mixed gas was then contacted with the supported catalyst obtained in Preparation Example 1 to cause the ethylene in the second product to undergo an epoxidation reaction to generate ethylene oxide. The volume ratio of the inhibitor to ethylene was 0.002:1, the volume ratio of oxygen to ethylene was 0.5:1, and the conditions for the epoxidation reaction of ethylene included: a temperature of 235°C, a pressure of 2.1 MPa, and a space velocity of 10,000 h⁻¹ (based on ethylene). -1 The ethylene oxide produced by the epoxidation reaction of ethylene is collected after condensation. The methane in the collected product is returned to the methane oxidative coupling reaction in step (1), while the unreacted ethylene is returned to the ethylene epoxidation reaction in step (3). The conversion rate of ethylene and the selectivity of ethylene oxide are shown in Table 3.

[0094] Table 2

[0095]

[0096]

[0097] Example 4

[0098] The procedure was carried out according to Example 1, except that the supported catalyst obtained in Preparation Example 1 in step (3) was replaced with the supported catalyst obtained in Preparation Example 3.

[0099] Example 5

[0100] The procedure was carried out according to Example 1, except that the supported catalyst obtained in Preparation Example 1 in step (3) was replaced with the supported catalyst obtained in Preparation Example 4.

[0101] Example 6

[0102] The procedure was carried out according to Example 1, except that the supported catalyst obtained in Preparation Example 1 in step (3) was replaced with the supported catalyst obtained in Preparation Example 5.

[0103] Example 7

[0104] The procedure was carried out according to Example 1, except that the supported catalyst obtained in Preparation Example 1 in step (3) was replaced with the supported catalyst obtained in Preparation Example 6.

[0105] Comparative Example 1

[0106] The procedure is carried out according to Example 7, except that the CO removal process in step (2-1) is not included.

[0107] Comparative Example 2

[0108] The method is carried out according to Example 7, except that the process of removing at least part of the CO2 in step (2-2) is not included.

[0109] Comparative Example 3

[0110] The method was carried out according to Example 7, except that in step (2-2), the volume ratio of carbon dioxide to ethylene in the second gas phase product was 0.05:1.

[0111] Table 3

[0112] Ethylene conversion rate (%) Selectivity of ethylene oxide (%) Example 1 50.3 71.2 Example 2 54.3 68.5 Example 3 52.3 71.2 Example 4 51.3 67.8 Example 5 49.6 65.5 Example 6 48.3 63.2 Example 7 44.2 55 Comparative Example 1 33.2 43.5 Comparative Example 2 30.5 41.3 Comparative Example 3 29.5 40.2

[0113] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing ethylene oxide by coupling a methane oxidative coupling reaction with an ethylene epoxidation reaction, characterized in that, The method includes the following steps: (1) In the presence of an oxidative coupling catalyst, methane undergoes an oxidative coupling reaction to obtain a first gaseous product containing ethylene, CO2 and CO. (2) The first gaseous product is contacted with an oxidant to oxidize the CO in the first gaseous product to generate CO2, and then at least part of the CO2 is removed to obtain the second gaseous product; wherein the volume ratio of carbon dioxide to ethylene in the second gaseous product is 0.1-0.3:1; (3) The second gaseous product is brought into contact with the catalyst to cause the ethylene in the second gaseous product to undergo an epoxidation reaction.

2. The method according to claim 1, wherein, In step (3), the catalyst is a supported catalyst. Preferably, the supported catalyst includes Ag and a support, and the Ag has a rod-like structure. More preferably, the length of the rod-shaped structure is 10-200 nm, preferably 50-200 nm; and the diameter is 2-10 nm, preferably 2-8 nm.

3. The method according to claim 2, wherein, The content of Ag is 5-30% by weight, preferably 13-25% by weight, based on the total weight of the supported catalyst. And / or, the support in the supported catalyst is alumina.

4. The method according to claim 2, wherein, The supported catalyst further includes an alkaline earth metal promoter, preferably, the alkaline earth metal promoter includes at least one of Mg, Ca, Sr and Ba; more preferably, the content of the alkaline earth metal promoter is 0.001-0.05% by weight, preferably 0.003-0.04% by weight, based on the total weight of the supported catalyst.

5. The method according to claim 1, wherein, In step (3), the conditions for the epoxidation reaction of ethylene include: a temperature of 220-250℃, a pressure of 1-2.1 MPa, and a space velocity (HV) of 7000-10000 h⁻¹ (based on ethylene). -1 .

6. The method according to claim 1, wherein, Step (3) further includes: mixing the second gaseous product with an inhibitor and then contacting it with a catalyst, wherein the inhibitor is dichloroethane and the volume ratio of the inhibitor to ethylene is 0.002-0.005:

1.

7. The method according to claim 1, wherein, The oxidative coupling catalyst includes at least one of NaWMn / SiO2, NaWMn / TiO2, NaWMn / BaTiO3, lanthanum oxide, lanthanum oxycarbonate, and lanthanum hydroxide; And / or, the conditions for the oxidative coupling reaction include: a temperature of 450-900℃, a molar ratio of methane to oxygen of 3-8:1, and a reaction space velocity of 10000-100000 ml / gh based on methane.

8. The method according to claim 1, wherein, The first gaseous product contains 2-5% ethylene and 2-10% CO by volume. And / or, the first gaseous product further includes methane, ethane and CO2; wherein, the content of methane in the first gaseous product is 50-90% by volume, the content of ethane is 2-10% by volume, and the content of CO2 is 4-25% by volume. And / or, step (1) further includes: cooling the product of the oxidative coupling reaction of methane to remove water; And / or, the first gaseous product also includes oxygen, with an oxygen content of less than 0.5% by volume.

9. The method according to claim 1, wherein, The oxidant is copper oxide; And / or, the conditions for contact between the first gaseous product and the oxidant include: a temperature of 200-500°C, and a molar ratio of carbon monoxide to oxidant in the first gaseous product of 1:1-1.

2.

10. The method according to claim 1, wherein, The method further includes: separating the ethylene oxide generated in step (3) and returning the unreacted ethylene to step (3); And / or, the method further includes: separating the ethylene oxide generated in step (3) and returning the unreacted methane to step (1).

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