Modified alpha-alumina carrier, preparation method thereof, supported silver catalyst and application

Abstract

The invention relates to the technical field of catalyst carriers, and relates to a modified alpha-alumina carrier, a preparation method thereof, a supported silver catalyst and application. The modified alpha-alumina carrier is an alpha-alumina carrier with a silane coupling structure on the surface, and silane is at least one of silane compounds containing 1-3-Si-O-C-structures and containing vinyl or amino. Preferably, the silane compound is selected from at least one of vinylmethoxysilane, 3-aminopropyltriethoxysilane and methylvinyldimethoxysilane. According to the modified alpha-alumina carrier, the silane solution is adopted to treat the alpha-alumina carrier, silane contains a-Si-O-C-structure, the group can form a relatively stable structure on the surface of the carrier after hydrolysis or dehydration condensation, and influence is generated for a long time in the use process of a silver catalyst, so that the performance of the catalyst is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst carriers, and more specifically, to a modified α-alumina carrier and a preparation method thereof, a loaded silver catalyst comprising the modified α-alumina carrier, and application of the loaded silver catalyst in the production of ethylene oxide by ethylene oxidation. Background Art

[0002] Silver catalyst is a catalyst widely used in chemical reactions. It has important commercial value in industrial production, especially in catalyzing ethylene epoxidation. Ethylene oxide, as a chemical product, is a major petrochemical product in demand among ethylene derivatives, second only to polyethylene. It can produce products such as ethylene glycol, polyester and surfactants. The process of catalyzing ethylene oxide with industrial silver catalyst is accompanied by the side reaction of complete oxidation of ethylene to produce carbon dioxide.

[0003] Silver catalysts usually use α-alumina as the main component of the carrier, on which the main active component silver is loaded, and a certain amount of additives and co-additives are added to improve the performance of the catalyst. In the actual production application of silver catalysts, activity, selectivity and stability are the three most important performance indicators. Activity refers to the amount of raw material reactants converted per unit volume (or mass) of catalyst per unit time under certain reaction conditions. For ethylene epoxidation reaction, the activity of the catalyst is often measured by the applicable space-time yield or the reaction temperature required at a certain space-time yield. The higher the applicable space-time yield or the lower the reaction temperature required at a certain space-time yield, the higher the activity of the silver catalyst. Selectivity refers to the comparison of the degree to which the same catalyst promotes different reactions in a reaction system where multiple reactions can occur. In this reaction, it refers to the ratio of the number of moles of ethylene converted into the main product ethylene oxide to the number of moles of ethylene in the total reaction. Stability refers to the ability of the catalyst to maintain the activity, selectivity, anti-toxicity, thermal stability and other properties and structure unchanged during the catalytic reaction. The better the stability of the catalyst, the longer its life. The optimization of silver catalyst performance is often to improve one or more of activity, selectivity and stability. Among them, selectivity is particularly important because it directly affects production costs and environmental protection.

[0004] Using different substances to modify silver catalysts to improve the performance of silver catalysts is one of the common methods used by workers in this field. CN103769165 adds copper micrometer wires, urotropine and polyvinyl pyrrolidone to water in turn, and ultrasonically vibrates to obtain a copper dispersion; adds an aqueous silver nitrate solution to the copper dispersion, performs a replacement reaction, and obtains a linear silver catalyst with high photocatalytic activity that can be used to degrade organic pollutants after a series of treatments, but it is not a catalyst for preparing ethylene oxide. US11612881B2 adds a certain amount of surfactant to the impregnation solution, so that the carrier is in contact with the impregnation solution containing the surfactant. The use of the surfactant leads to improved discharge of the silver impregnation solution from the outside of the carrier during the catalyst synthesis, and the amount of silver-containing impregnation solution required for the synthesis of EO catalyst is reduced by up to 15% without reducing the catalyst performance. CN111097529B uses a silicon-containing nanocage structure to prepare a catalyst, which is applied to the reaction of hydration of alkylene oxide to produce glycols.

[0005] Although the above patent documents adopt different methods to improve the catalyst, there is still room for improvement in the selectivity of silver catalysts, and there is also room for improvement in the method of introducing organic groups in the field of ethylene epoxidation silver catalysts. Summary of the invention

[0006] Against the background of the above-mentioned prior art, the inventors of the present invention have conducted a large number of optimization experiments on the preparation process of the silver catalyst and found that some organic groups such as amine groups can combine with silver nanoparticles in the silver catalyst to help disperse the surface charge of the active component and have a favorable effect on the selectivity; the introduction of vinyl and alkyl groups can react with the chlorine groups dissociated from the chlorine-containing regulator during the reaction, absorb the chlorine enriched on the local surface, and adjust the chlorine concentration on the surface of the active component of the catalyst, which helps to stabilize and control the reaction, thereby adjusting and improving the selectivity of the silver catalyst.

[0007] In order to achieve the purpose of the present invention, the first aspect of the present invention provides a modified α-alumina carrier, wherein the modified α-alumina carrier is an α-alumina carrier having a silane coupling structure on the surface.

[0008] The second aspect of the present invention provides a method for preparing a modified α-alumina carrier, comprising the following steps:

[0009] (1) obtaining a silane solution;

[0010] (2) The silane solution obtained in step (1) is used to fully impregnate the α-alumina carrier, and the modified α-alumina carrier is obtained by leaching and drying.

[0011] The third aspect of the present invention provides a modified α-alumina carrier obtained by the preparation method.

[0012] The fourth aspect of the present invention provides a supported silver catalyst, which includes the modified α-alumina carrier and a catalytically effective amount of silver deposited thereon, an optional alkali metal promoter and / or alkaline earth metal promoter, and an optional rhenium promoter and a co-promoter thereof.

[0013] The fifth aspect of the present invention provides the use of the supported silver catalyst in the epoxidation of ethylene to produce ethylene oxide.

[0014] The modified α-alumina carrier of the present invention is treated with a silane solution. The silane contains a -Si-OC- structure. The group can form a relatively stable structure on the surface of the carrier after hydrolysis or dehydration condensation, which has a long-term impact during the use of the silver catalyst, thereby improving the performance of the catalyst.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0017] Figure 1 The infrared spectra of the carriers prepared in Examples 1-2 and Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0019] In order to achieve the purpose of the present invention, the first aspect of the present invention provides a modified α-alumina carrier, wherein the modified α-alumina carrier is an α-alumina carrier having a silane coupling structure on the surface.

[0020] According to the present invention, preferably, the silane is at least one of silane compounds containing 1 to 3 -Si-OC- structures and containing a vinyl group or an amino group, preferably at least one selected from vinylmethoxysilane, 3-aminopropyltriethoxysilane and methylvinyldimethoxysilane.

[0021] According to the present invention, preferably, the modified α-alumina carrier is obtained by modifying the α-alumina carrier with a silane solution.

[0022] According to the present invention, preferably, the solvent of the silane solution is at least one of water, methanol, ethanol and acetone.

[0023] Preferably, based on the total weight of the silane solution, the content of silane is 0.01 to 20 wt %, preferably 0.05 to 5 wt %.

[0024] In the present invention, the silane is selected to have 1 to 3 -Si-OC- structures, which can form a relatively stable structure on the surface of the carrier after hydrolysis or dehydration condensation, thereby exerting a long-term effect during the use of the silver catalyst. One or more silanes with vinyl or amino groups have a content of 0.01 to 20 wt%, and the content of silane in the silane solution adsorbed by the carrier after the final leaching is adjusted by adjusting the concentration, thereby adjusting the total amount of silicon-containing organic matter after treatment.

[0025] In the present invention, the solvent of the silane solution is selected to be a solvent with a low boiling point and good stability that can dissolve silane, so as to facilitate drying and separating the solvent, leaving the silicon-containing organic matter on the surface of the carrier, which can be one or more volatile polar solvents such as water, methanol, ethanol, acetone, etc.

[0026] According to the present invention, preferably, the α-alumina carrier has the following characteristics: a crushing strength of 35 to 300 N / particle, preferably 50 to 250 N / particle, a specific surface area of ​​0.6 to 2.6 m 2 / g, preferably 1.0 to 2.2 m 2 / g, and the pore volume is 0.3-1.2 ml / g, preferably 0.4-0.8 ml / g.

[0027] The second aspect of the present invention provides a method for preparing a modified α-alumina carrier, comprising the following steps:

[0028] (1) obtaining a silane solution;

[0029] (2) The silane solution obtained in step (1) is used to fully impregnate the α-alumina carrier, and the modified α-alumina carrier is obtained by leaching and drying.

[0030] According to the present invention, preferably, in the silane solution, the silane is at least one of silane compounds containing 1 to 3 -Si-OC- structures and containing a vinyl group or an amino group, preferably selected from at least one of vinylmethoxysilane, 3-aminopropyltriethoxysilane and methylvinyldimethoxysilane; and the solvent is at least one of water, methanol, ethanol and acetone.

[0031] Preferably, based on the total weight of the silane solution, the content of silane is 0.01 to 20 wt %, preferably 0.05 to 5 wt %.

[0032] According to the present invention, preferably, the α-alumina carrier has the following characteristics: a crushing strength of 35 to 300 N / particle, preferably 50 to 250 N / particle, a specific surface area of ​​0.6 to 2.6 m 2 / g, preferably 1.0 to 2.2 m 2 / g, and the pore volume is 0.3-1.2 ml / g, preferably 0.4-0.8 ml / g.

[0033] According to the present invention, preferably, the drying conditions include: temperature of 60-290° C. and time of 0.1-5 h.

[0034] In the present invention, the pressure may be appropriately reduced to lower the drying temperature.

[0035] The third aspect of the present invention provides a modified α-alumina carrier obtained by the preparation method.

[0036] The fourth aspect of the present invention provides a supported silver catalyst, which includes the modified α-alumina carrier and a catalytically effective amount of silver deposited thereon, an optional alkali metal promoter and / or alkaline earth metal promoter, and an optional rhenium promoter and a co-promoter thereof.

[0037] In the present invention, the impregnation preparation method of the silver catalyst described in each step can be prepared according to the method known to technicians in the field of silver catalyst preparation or conventionally disclosed methods, and a certain amount of impregnation solution is prepared for preparing the silver catalyst. The impregnation solution mainly contains a mixture of silver-containing compounds, water, amines and other conventional polar solvents, alkali metal additives, alkaline earth metal additives, optional rhenium additives and co-auxiliaries, and the temperature of the impregnation solution is maintained below 30°C to prevent the silver-containing compounds from being decomposed and precipitated prematurely due to heat.

[0038] According to the present invention, preferably, in step I, the solvent is at least one of ammonia water, ethylamine, ethylenediamine, ethanol, 1,3-propylenediamine, dimethylformamide, 1,4-butylenediamine, ethanolamine, and tetrahydrofuran; the silver-containing compound is at least one of silver acetate, silver nitrate, and silver oxalate; the alkali metal additive is selected from at least one of soluble salts of lithium, sodium, potassium, rubidium, and cesium; the alkaline earth metal additive is selected from at least one of soluble salts of magnesium, calcium, strontium, and barium; the rhenium additive is selected from at least one of potassium perrhenate, perrhenic acid, and ammonium rhenate; the rhenium co-additive is selected from at least one of salts and acids containing manganese, chromium, sulfur, cobalt, molybdenum, and nickel.

[0039] In the present invention, the solvent and the generated impurities need to be removed as much as possible during the activation process.

[0040] Preferably, based on the weight of the mixed impregnation liquid, the content of the solvent is 10 to 90 wt%; the content of the silver-containing compound in terms of silver element is 10 to 40 wt%; the content of the alkali metal additive is 50 to 2000 ppm; the content of the alkaline earth metal additive is 0 to 3000 ppm; the content of the rhenium additive is 0 to 2000 ppm; and the content of the rhenium co-additive is 0 to 2000 ppm.

[0041] According to the present invention, preferably, in step II, the immersion conditions include: temperature below 30° C., pressure below 10 mmHg, and time of 0.1 to 300 minutes.

[0042] In the present invention, the alumina carrier is treated by a solution impregnation method commonly used in the art, and this process can be accelerated by reducing the pressure to below 100 mmHg, so that there are no tiny bubbles on the surface of the carrier and the inner and outer surfaces are fully wetted.

[0043] According to the present invention, preferably, the drying is carried out in air or an inert gas atmosphere, the drying temperature is 60 to 200° C., and the drying time is 0.1 to 300 min.

[0044] In the present invention, the drying process can be accelerated by auxiliary decompression, and appropriate vibration or stirring can be selected during the drying process to make the solute precipitate more uniformly.

[0045] According to the present invention, preferably, the activation is carried out in flowing air or inert gas atmosphere, the activation temperature is 180-380° C., and the activation time is 1-30 min.

[0046] According to the present invention, preferably, when the silver content in the catalyst needs to be increased, an impregnation solution with a higher silver concentration can be prepared, or the catalyst obtained after activation in step II can be subjected to step III again, and impregnation, leaching, drying and activation are repeated to achieve the purpose of significantly increasing the loaded silver content.

[0047] The fifth aspect of the present invention provides the use of the supported silver catalyst in the epoxidation of ethylene to produce ethylene oxide.

[0048] The present invention also provides a method for oxidizing ethylene to ethylene oxide, which comprises reacting a mixed gas of ethylene and oxygen and other gases in a fixed bed micro-tubular reactor in the presence of the silver catalyst of the present invention.

[0049] The present invention will be further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0050] Method for determining the performance of silver catalyst:

[0051] The various silver catalysts prepared in the present invention are evaluated for initial catalytic reaction performance and stability using a micro-tubular reactor (hereinafter referred to as "micro-reactor"). The tubular reactor used in the micro-reactor evaluation device is a stainless steel reaction tube with an inner diameter of 4 mm, and the reaction tube is placed in a copper or aluminum heating jacket. After the silver catalyst particles are crushed, 0.8 g of catalyst particles with a size of 12 to 18 meshes are screened and filled into the reactor for compaction. The lower part of the reactor has an inert filler so that the catalyst bed is located in the constant temperature zone of the heating jacket.

[0052] The standard evaluation conditions for catalytic activity and selectivity used in the present invention are as follows (the actual reaction conditions are described in the examples):

[0053] Gas composition at the reaction inlet (mol%): ethylene, 30.0±2.0; oxygen, 7.0-8.0; carbon dioxide, <3.0; nitrogen, balance; ethylene dichloride, 0.1-2.0ppm. Reaction pressure 2.1MPa; space velocity 6000h -1 ; The reaction temperature is manually controlled; the target concentration of ethylene oxide in the reactor outlet tail gas is set to 2.5%.

[0054] The reactor was gradually heated from room temperature. When the reaction stabilized under the operating conditions, the gas composition at the reactor inlet and outlet was continuously measured. The selectivity (S) was calculated according to the following formula after the volume shrinkage correction was performed on the measured results:

[0055] Where ΔEO is the concentration difference of ethylene oxide in the reactor outlet gas and the inlet gas, and ΔCO2 is the concentration difference of carbon dioxide in the reactor outlet gas and the inlet gas.

[0056] Example 1

[0057] Catalyst preparation

[0058] 20g of porous alumina carrier for industrial silver catalyst was selected. It was a white seven-hole cylinder with a crushing strength of 160N / grain and a specific surface area of ​​1.9m 2 / g, pore volume 0.7ml / g. After the support is fully impregnated with a 0.1wt% aqueous solution of vinylmethoxysilane, it is leached and dried in an oven at 100°C for 3 hours before being taken out.

[0059] Mix 50g 1,3-propylenediamine, 10g ammonia water, 10g tetrahydrofuran, and 100g deionized water evenly and cool to 15°C in a water bath. Slowly add 100g silver nitrate. After the silver nitrate is completely dissolved, add 0.02g lithium nitrate, 0.1g barium nitrate, 0.6g perrhenic acid, and 0.05g manganese nitrate. Mix evenly to use as the impregnation solution. Immerse the carrier treated in the previous step with the prepared impregnation solution, put it in a vacuum container, vacuumize it to reduce the pressure to below 10mmHg, fully soak for half an hour, leach the excess solution, dry it in an oven at 80°C for 1 hour, and then take it out. Activate it at 300°C for 5min to obtain the finished catalyst.

[0060] Repeat the above impregnation with the silver-containing impregnation solution, and leaching, drying and activation under the same conditions to obtain a finished catalyst.

[0061] Example 2

[0062] The preparation of the catalyst was the same as in Example 1, except that the 0.1 wt % aqueous solution of vinylmethoxysilane in step I was replaced by a 0.1 wt % ethanol solution of 3-aminopropyltriethoxysilane.

[0063] Example 3

[0064] The preparation of the catalyst was the same as in Example 1, except that the 0.1 wt % aqueous solution of vinylmethoxysilane in step I was replaced by an aqueous solution containing 0.6 wt % methylvinyldimethoxysilane and 1.5 wt % 3-aminopropyltriethoxysilane.

[0065] Example 4

[0066] The preparation of the catalyst was the same as in Example 2, except that in step I, 0.5 wt % of 3-aminopropyltriethoxysilane ethanol solution was used.

[0067] Example 5

[0068] The preparation of the catalyst was the same as in Example 2, except that in step I, 1 wt % of 3-aminopropyltriethoxysilane in ethanol was used instead.

[0069] Example 6

[0070] The preparation of the catalyst was the same as in Example 1, except that the 0.1 wt % aqueous solution of vinylmethoxysilane in step I was replaced by a 1 wt % acetone solution of methylvinyldimethoxysilane.

[0071] Example 7

[0072] The preparation of the catalyst was the same as in Example 1, except that the 0.1 wt % aqueous solution of vinylmethoxysilane in step I was replaced with 0.5 wt % methylvinyldimethoxysilane and 0.5 wt % methanol solution of vinylmethoxysilane.

[0073] Example 8

[0074] The preparation of the catalyst is the same as in Example 1, except that in step I, a 6 wt % aqueous solution of vinylmethoxysilane is used.

[0075] Comparative Example 1

[0076] The preparation of the catalyst is the same as in Example 1, except that the silane solution treatment in step I is not used.

[0077] Comparative Example 2

[0078] The preparation of the catalyst is the same as in Example 2, except that the silane solution in step I is replaced by pure deionized water, which is equivalent to rinsing the carrier once with water and drying it before use.

[0079] Test Case

[0080] The carriers prepared in Examples 1-2 and Comparative Example 2 were observed using an infrared spectrometer. The results are as follows: Figure 1 As shown, from Figure 1 It can be seen that after silane treatment, the carrier of Example 1-2 has a high -1 Compared with the untreated comparative example 2, there is an obvious absorption peak in the range of , which is close to the peak position of the corresponding pure substance silane, indicating that the corresponding silane coupling structure is formed by the support surface loading modification. Using a microreactor evaluation device, the initial reaction characteristics of the catalyst samples were measured under the above-mentioned process conditions, and the test results are listed in Table 1.

[0081] Table 1

[0082] Selectivity (%) Reaction temperature (℃) Example 1 84.24 216.2 Example 2 84.30 216.4 Example 3 84.11 216.8 Example 4 84.23 216.1 Example 5 84.33 215.9 Example 6 83.97 216.3 Example 7 84.15 216.2 Example 8 84.08 216.9 Comparative Example 1 83.09 216.3 Comparative Example 2 83.19 217.3

[0083] As can be seen from Table 1, the selectivity of the silver catalyst prepared using the carrier treated with silane has been significantly improved.

[0084] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0085] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A modified α-alumina carrier, characterized in that: The modified α-alumina carrier is an α-alumina carrier with a silane coupling structure on the surface.

2. The modified α-alumina carrier according to claim 1, wherein The silane is at least one of silane compounds containing 1 to 3 -Si-OC- structures and containing a vinyl group or an amino group, and is preferably at least one selected from vinylmethoxysilane, 3-aminopropyltriethoxysilane and methylvinyldimethoxysilane.

3. The modified α-alumina carrier according to claim 1 or 2, wherein The modified α-alumina carrier is obtained by modifying the α-alumina carrier with a silane solution.

4. The modified α-alumina carrier according to claim 3, wherein The solvent of the silane solution is at least one of water, methanol, ethanol and acetone; Based on the total weight of the silane solution, the content of silane is 0.01 to 20 wt %, preferably 0.05 to 5 wt %.

5. The modified α-alumina carrier according to claim 1 or 2, wherein The α-alumina carrier has the following characteristics: a crushing strength of 35 to 300 N / grain, preferably 50 to 250 N / grain, and a specific surface area of ​​0.6 to 2.6 m 2 / g, preferably 1.0 to 2.2 m 2 / g, and the pore volume is 0.3-1.2 ml / g, preferably 0.4-0.8 ml / g.

6. A method for preparing a modified α-alumina carrier, characterized in that: The steps include: (1) obtaining a silane solution; (2) The silane solution obtained in step (1) is used to fully impregnate the α-alumina carrier, and the modified α-alumina carrier is obtained by leaching and drying.

7. The method for preparing a modified α-alumina carrier according to claim 6, wherein: In the silane solution, the silane is at least one of silane compounds containing 1 to 3 -Si-OC- structures and containing vinyl or amino groups, preferably at least one selected from vinylmethoxysilane, 3-aminopropyltriethoxysilane and methylvinyldimethoxysilane; the solvent is at least one of water, methanol, ethanol and acetone; Based on the total weight of the silane solution, the content of silane is 0.01 to 20 wt %, preferably 0.05 to 5 wt %.

8. The method for preparing a modified α-alumina carrier according to claim 6, wherein: The α-alumina carrier has the following characteristics: a crushing strength of 35 to 300 N / grain, preferably 50 to 250 N / grain, and a specific surface area of ​​0.6 to 2.6 m 2 / g, preferably 1.0 to 2.2 m 2 / g, and the pore volume is 0.3-1.2 ml / g, preferably 0.4-0.8 ml / g.

9. The method for preparing a modified α-alumina carrier according to claim 6, wherein: The drying conditions include: temperature of 60-290° C. and time of 0.1-5 h.

10. A modified α-alumina carrier obtained by the preparation method according to any one of claims 6 to 9.

11. A supported silver catalyst, characterized in that: The supported silver catalyst comprises the modified α-alumina carrier according to any one of claims 1-5 and 10 and a catalytically effective amount of silver, an optional alkali metal promoter and / or an alkaline earth metal promoter, and an optional rhenium promoter and a co-promoter thereof deposited thereon.

12. The supported silver catalyst according to claim 11, wherein The preparation method of the supported silver catalyst comprises the following steps: Step I, obtaining a mixed impregnation solution, wherein the mixed impregnation solution comprises: a silver-containing compound, a solvent, water, an alkali metal additive, an optional alkaline earth metal additive, an optional rhenium additive and a co-additive thereof; Step II, using the mixed impregnation solution obtained in step I to fully impregnate the modified α-alumina carrier described in any one of claims 1-4 and 9, and then leaching, drying and activating to obtain the supported silver catalyst.

13. The supported silver catalyst according to claim 12, wherein In step I, the solvent is at least one of ammonia water, ethylamine, ethylenediamine, ethanol, 1,3-propylenediamine, dimethylformamide, 1,4-butylenediamine, ethanolamine, and tetrahydrofuran; the silver-containing compound is at least one of silver acetate, silver nitrate, and silver oxalate; the alkali metal additive is at least one of soluble salts of lithium, sodium, potassium, rubidium, and cesium; the alkaline earth metal additive is at least one of soluble salts of magnesium, calcium, strontium, and barium; the rhenium additive is at least one of potassium perrhenate, perrhenic acid, and ammonium rhenate; the rhenium co-additive is at least one of salts and acids containing manganese, chromium, sulfur, cobalt, molybdenum, and nickel; Based on the weight of the mixed impregnation liquid, the content of the solvent is 10 to 90 wt%; the content of the silver-containing compound in terms of silver element is 10 to 40 wt%; the content of the alkali metal additive is 50 to 2000 ppm; the content of the alkaline earth metal additive is 0 to 3000 ppm; the content of the rhenium additive is 0 to 2000 ppm; and the content of the rhenium co-additive is 0 to 2000 ppm.

14. The supported silver catalyst according to claim 12, wherein In step II, the immersion conditions include: temperature below 30°C, pressure below 10 mmHg, and time of 0.1 to 300 minutes; The drying is carried out in air or inert gas atmosphere, the drying temperature is 60-200°C, and the drying time is 0.1-300min; The activation is carried out in flowing air or inert gas atmosphere, the activation temperature is 180-380° C., and the activation time is 1-30 minutes.

15. The supported silver catalyst according to claim 12, wherein The preparation method further comprises: subjecting the activated catalyst to at least one more step of impregnation, leaching, drying and activation.

16. Use of the supported silver catalyst according to any one of claims 11 to 12 in the epoxidation of ethylene to produce ethylene oxide.

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