A silver catalyst for producing ethylene oxide by ethylene oxidation, and its preparation method and application

Abstract

The present application belongs to the field of silver catalysts, and relates to a silver catalyst for ethylene oxidation to produce ethylene oxide, and a preparation method and application thereof. The silver catalyst comprises an alumina carrier, silver supported thereon, nano manganese dioxide and an additive. The content of the silver is 2-39 wt% based on the total weight of the silver catalyst; the content of the nano manganese dioxide is 0.001-0.5 wt%. The silver catalyst is obtained by impregnating the alumina carrier in a silver ammonia solution, solid-liquid separation and calcination. The silver ammonia solution comprises a chelating agent, and the content of the chelating agent is 0.01-20.0 wt%. The porous alumina carrier is impregnated in the silver ammonia solution containing the chelating agent and the nano manganese dioxide, and the silver catalyst prepared therefrom has high reactivity, and is particularly suitable for the reaction of ethylene oxidation to produce ethylene oxide.

Description

Technical Field

[0001] The present invention belongs to the field of silver catalysts, and specifically relates to a silver catalyst for producing ethylene oxide by ethylene oxidation, a method for preparing the silver catalyst for producing ethylene oxide by ethylene oxidation, a silver catalyst obtained by the method for preparing the silver catalyst for producing ethylene oxide by ethylene oxidation, and application of the silver catalyst in the reaction of producing ethylene oxide by ethylene oxidation. Background Art

[0002] Ethylene oxidation over a silver catalyst primarily produces ethylene oxide, with carbon dioxide and water as side reactions. Activity, selectivity, and stability are the key performance indicators of silver catalysts. Activity refers to the reaction temperature required to achieve a certain reaction load in the ethylene oxide production process. The lower the reaction temperature, the higher the catalyst activity. Selectivity refers to the ratio of the number of moles of ethylene converted to ethylene oxide to the total number of moles of ethylene reacted. Stability is expressed as the rate of decrease in activity and selectivity; the slower the rate of decrease, the greater the catalyst stability. Using silver catalysts with high activity, selectivity, and stability in the ethylene oxide production process can significantly improve economic efficiency. Therefore, the development of silver catalysts with high activity, selectivity, and stability is a major research focus. The performance of silver catalysts is not only significantly influenced by the catalyst composition and preparation method, but also by the properties and preparation method of the catalyst support.

[0003] The preparation method of silver catalyst in the prior art includes two processes: preparation of a porous carrier (such as alumina) and application of active components and additives to the carrier. In the preparation process of silver catalyst, for the carrier with α-Al2O3 as the main component, suitable specific surface area and pore structure are required. On the one hand, it is necessary to provide enough space for the ethylene epoxidation reaction to diffuse the reaction heat. On the other hand, it is also beneficial for the timely desorption of the reaction product ethylene oxide to avoid deep oxidation to generate by-product carbon dioxide. German patent WO2021260138A1 provides a shaped catalyst body for the gas-phase oxidation of ethylene to produce ethylene oxide, and its BET surface area is 2-20m 2 / g, and comprises silver and rhenium promoters deposited on a porous alumina catalyst support, characterized in that the support has a calcination history of at least 1460°C, and the catalyst support has a high surface area and a small amount of ethylene oxide isomerization and / or decomposition activity. Chinese patent CN1009437B uses alumina trihydrate with a suitable proportion to prepare a catalyst with a specific surface area of ​​0.2 to 2 m 2 / g, an alumina carrier with a pore volume greater than 0.5mL / g, wherein pores with a pore radius greater than 30μm account for less than 25%, and can achieve a selectivity of 83-84% for ethylene epoxidation reaction.

[0004] It is also an important research direction to improve the performance of silver catalyst by adding other components to the alumina support. In addition, the performance of silver catalyst can also be improved by chemical treatment of the alumina support. German patent WO2021260185A1 provides a sheet-shaped catalyst support characterized by an alpha-alumina content of at least 85 wt.%, a pore volume of at least 0.40 ml / g measured by the mercury porosimetry method, a BET surface area of 0.5-5.0 m 2 / g, the sheet-shaped catalyst support is an alpha-alumina catalyst support which has a high geometric precision and shows a high total pore volume, thereby allowing impregnation with a large amount of silver, while showing a sufficiently large surface area to provide optimal dispersion of catalytically active species, in particular metallic species. European patent EP0150238B1 uses a small amount of barium aluminate or barium silicate binder in the manufacturing process of high-purity, low-surface alumina support, claiming to improve the crushing strength and wear resistance of the support, the specific surface area of the support manufactured by the patent is less than 0.3 m 2 / g, the activity and selectivity of the prepared catalysts are low. US4740493A, US4829043A and EP0501317A1 use alumina carriers containing a certain amount of Ca, Al, K, Na soluble salts, which are claimed to reduce the rate of decline of the selectivity of the catalyst during use. US5384302A claims that the pretreatment of α-Al2O3 reduces the content of Na, K, Ca, Al ions in the carrier, thereby improving the crushing strength and wear resistance of the carrier. KR102258044B1 adjusts the metal crystal size by adding polyvinylpyrrolidone to prepare a catalyst for generating high-yield ethylene oxide from ethylene, which first dissolves a compound containing at least one first metal selected from Ag, Pd and Pt in a solvent to form a solution, contains at least one compound of a first metal selected from cesium, rhenium, molybdenum, lithium, sodium, and then adds polyvinylpyrrolidone (PVP) with a molecular weight of 20,000-55,000 to the catalyst precursor solution in an amount of 0.3-0.6 wt% based on the catalyst precursor solution. EP0712334B1 supports an effective amount of silver, an auxiliary amount of an alkali metal, an auxiliary amount of magnesium and an auxiliary amount of rhenium on a carrier containing at least 85% alumina and 0.001-2% magnesium in the form of an oxide to prepare a silver catalyst, which improves the stability of the catalyst. US5100859A, US5145824A, EP0900126B1, US5801259A, US5733842A add alkaline earth metals, silicon, zirconium to α-Al2O3 to make a carrier, and then impregnate silver, alkali metal auxiliary agent, rhenium auxiliary agent and its auxiliary agent to make a silver catalyst, which points out that the compounds of alkaline earth metals, preferably calcium, strontium and barium, are used together with zirconium, but it is unknown that the addition of both affects the performance of the catalyst. US5739075A pre-deposits an auxiliary amount of rare earth metal and another auxiliary amount of metal salt (alkaline earth metal or Group VIII transition metal) on the surface of the alumina carrier, then performs a calcination treatment, and finally makes a silver catalyst from the treated carrier, and the evaluation results show that the selectivity decline rate of the catalyst is less than that of the catalyst sample without pre-deposition treatment. CN1511632A finds that adding a heavy alkaline earth metal compound to an alumina raw material to make a carrier, impregnating a solution prepared from a silver compound, an organic amine and a specific auxiliary agent, and heat treating in an oxygen-containing mixed gas, the prepared silver catalyst has improved activity and selectivity in the ethylene oxidation reaction.

[0005] Although the above patent documents use various methods to improve the alumina carrier, the activity, stability and selectivity of the catalyst are improved to different degrees, but as the large-scale industrial application of the Re-containing high-selectivity silver catalyst, the requirements for the performance of the catalyst are also increasing, and therefore, the performance of the silver catalyst needs to be continuously improved. SUMMARY

[0006] In view of the above prior art, the inventors of the present application have made extensive and in-depth research in the field of silver catalysts, and found that the reaction activity of a silver catalyst made from a silver ammonia solution to which a proper amount of a chelating agent and nano manganese dioxide are added can be significantly improved.

[0007] The first aspect of the present application provides a silver catalyst for the production of ethylene oxide by ethylene oxidation, which comprises an alumina carrier and silver, nano manganese dioxide and an auxiliary agent supported thereon.

[0008] The content of the silver is 2-39 wt%, preferably 10-35 wt%, based on the total weight of the silver catalyst; the content of the nano manganese dioxide is 0.001-0.5 wt%, preferably 0.005-0.1 wt%, and further preferably 0.01-0.05 wt%.

[0009] The second aspect of the present application provides a preparation method of a silver catalyst for the production of ethylene oxide by ethylene oxidation, comprising the following steps:

[0010] (1) obtaining a silver ammonia solution, which comprises a silver-containing compound, a chelating agent, nano manganese dioxide, an amine compound, water, an alkali metal auxiliary agent, an optional rhenium auxiliary agent and a co-auxiliary agent thereof;

[0011] (2) immersing an α-Al2O3 carrier in the silver ammonia solution obtained in step (1), then performing solid-liquid separation and calcination to obtain the silver catalyst.

[0012] The third aspect of the present application provides a silver catalyst prepared by the preparation method.

[0013] The fourth aspect of the present application provides the use of the silver catalyst in the reaction of ethylene oxidation for the production of ethylene oxide.

[0014] Compared with the prior art, the present application has the following advantages: the silver catalyst made from a porous alumina carrier immersed in a silver ammonia solution containing a chelating agent and nano manganese dioxide has high reaction activity, and is particularly suitable for the reaction of ethylene oxidation for the production of ethylene oxide.

[0015] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0016] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0017] The present invention provides a silver catalyst for producing ethylene oxide by ethylene oxidation. The silver catalyst comprises an alumina carrier and silver supported thereon, nano manganese dioxide, and an additive.

[0018] Wherein, based on the total weight of the silver catalyst, the content of silver is 2-39wt%, preferably 10-35wt%; the content of the nano manganese dioxide is 0.001-0.5wt%, preferably 0.005-0.1wt%, and more preferably 0.01-0.05wt%.

[0019] According to the present invention, preferably, the diameter of the nano manganese dioxide is 1 to 100 nanometers, preferably 10 to 80 nanometers.

[0020] According to the present invention, preferably, the alumina carrier is a porous α-Al2O3 carrier, wherein the α-Al2O3 content is ≥90%, and has the following characteristics: a crushing strength of 20 to 200 N / particle; a specific surface area of ​​0.2 to 3.0 m 2 / g; water absorption rate ≥30%; pore volume is 0.30~0.85mL / g.

[0021] According to the present invention, preferably, the auxiliary agent is an alkali metal auxiliary agent and an optional rhenium auxiliary agent and a co-auxiliary agent thereof; preferably, based on the total weight of the silver catalyst, the content of the alkali metal auxiliary agent is 1 to 2000 ppm, preferably 5 to 1500 ppm; the content of rhenium metal in terms of atoms is 0 to 2000 ppm, preferably 100 to 1000 ppm; the content of the co-auxiliary agent of the rhenium auxiliary agent in terms of atoms is 0 to 2000 ppm, preferably 100 to 1000 ppm.

[0022] According to the present invention, preferably, the silver catalyst is obtained by impregnating the alumina carrier in a silver ammonia solution, performing solid-liquid separation, and calcining. The silver ammonia solution comprises a silver-containing compound, a chelating agent, nano-manganese dioxide, an amine compound, water, an alkali metal additive, an optional rhenium additive, and a co-additive thereof; the chelating agent is selected from at least one of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and aminotriacetic acid; and the content of the chelating agent is 0.01 to 20.0 wt%, preferably 0.05 to 5.0 wt%, based on the total weight of the silver ammonia solution.

[0023] The present invention also provides a method for preparing a silver catalyst for producing ethylene oxide by ethylene oxidation, comprising the following steps:

[0024] (1) obtaining a silver ammonia solution, wherein the silver ammonia solution comprises a silver-containing compound, a chelating agent, nano manganese dioxide, an amine compound, water, an alkali metal additive, an optional rhenium additive, and a co-additive thereof;

[0025] (2) dipping the α-Al2O3 carrier into the silver ammonia solution obtained in step (1), then performing solid-liquid separation and calcination to obtain the silver catalyst.

[0026] According to the present application, preferably, in step (1), the diameter of the nanometer manganese dioxide is 1-100 nanometers, preferably 10-80 nanometers; the amount of the nanometer manganese dioxide added is such that the content of the nanometer manganese dioxide in the silver catalyst is 0.001-0.5wt%, preferably 0.005-0.1wt%, and further preferably 0.01-0.05wt%, based on the total weight of the silver catalyst.

[0027] According to the present application, preferably, in step (1), the chelating agent is at least one selected from ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and amino triacetic acid; the content of the chelating agent is 0.01-20.0wt%, preferably 0.05-5.0wt%, based on the total weight of the silver ammonia solution.

[0028] According to the present application, preferably, in step (1), the amine compound is at least one selected from ammonia, ethylamine, n-propylamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, N,N-dimethylformamide, ethanolamine and propanolamine; the silver-containing compound is at least one selected from silver acetate, silver nitrate and silver oxalate; the content of the amine compound is 10-90wt%, and the amount of the silver-containing compound added is such that the content of silver in terms of atoms in the silver catalyst is 2-39wt%, preferably 10-35wt%, based on the total weight of the silver ammonia solution.

[0029] According to the present application, preferably, in step (1), the alkali metal promoter is a compound of at least one selected from lithium, sodium, potassium, rubidium and cesium; the rhenium promoter is at least one selected from oxides of rhenium, perrhenic acid, cesium perrhenate, methyltrioxorhenium (VII) and ammonium perrhenate; the co-promoter of the rhenium promoter is at least one in the form of a salt or acid containing manganese, chromium, sulfur, cobalt, molybdenum, nickel; the amount of the alkali metal promoter added is such that the content of the alkali metal in the silver catalyst is 1-2000ppm, preferably 5-1500ppm, based on the total weight of the silver catalyst; the amount of the rhenium promoter added is such that the content of rhenium metal in terms of atoms in the silver catalyst is 0-2000ppm, preferably 100-1000ppm; the amount of the co-promoter of the rhenium promoter added is such that the content of the co-promoter of the rhenium promoter in terms of atoms in the silver catalyst is 0-2000ppm, preferably 100-1000ppm.

[0030] In the present application, the specific selection and amount of the alkali metal promoter, the rhenium promoter and the co-promoter thereof can be conventional selection in the art.

[0031] According to the present application, preferably, in step (2), the impregnation time is 10-300 minutes, and the impregnation is preferably carried out under a pressure of 100 mmHg or less.

[0032] The solid-liquid separation includes leaching and drying, and preferably, the drying after leaching is carried out in an air and / or inert gas atmosphere, at a temperature of 50-120℃ for 0.1-12 hours.

[0033] In the present application, the impregnation in step (2) can be carried out according to conventional methods in the art, and the alumina carrier is completely impregnated in the solution obtained in step (1) and impregnated sufficiently. The impregnation time can be 10-300 minutes, and the temperature of the impregnation solution is kept below 30℃ to prevent the silver-containing compound from being decomposed and precipitated prematurely. The impregnation process can be accelerated by reducing the pressure to 100 mmHg or less, and the carrier surface is preferably free of small air bubbles and the inner and outer surfaces are impregnated sufficiently.

[0034] In the present application, the solid-liquid separation in step (2) can include leaching and drying. The leaching process is preferably carried out to minimize the excess impregnation solution adhering to the surface of the carrier, and the excess dust in the alumina carrier can be removed at the same time. The drying is carried out sufficiently until the solid mass no longer changes significantly.

[0035] According to the present application, preferably, in step (2), the calcination is carried out in air or a nitrogen-oxygen mixed gas having an oxygen content of not more than 21%, and the calcination temperature is 100-600℃, preferably 150-500℃, and the calcination time is 0.5-120 minutes, preferably 1-30 minutes.

[0036] According to the present application, preferably, the α-Al2O3 carrier is a porous α-Al2O3 carrier having an α-Al2O3 content of ≥90% and the following characteristics: crushing strength of 20-200 N / particle; specific surface area of 0.2-3.0 m 2 / g; water absorption of ≥30%; pore volume of 0.30-0.85 mL / g.

[0037] The present application also provides a silver catalyst prepared by the preparation method.

[0038] The silver catalyst of the present application can be used in the production of ethylene oxide by the oxidation of ethylene. Specifically, a mixture of ethylene and oxygen gas is reacted in the presence of the silver catalyst in a fixed-bed micro-tube reactor.

[0039] The present application is further illustrated by the following examples, but the scope of the present application is not limited to these examples.

[0040] Determination of catalyst performance

[0041] The initial performance and stability of the various silver catalysts of the present application were tested in a laboratory reactor (hereinafter "microreactor") evaluation apparatus. The reactor used in the microreactor evaluation apparatus was a stainless steel tube with an inner diameter of 4 mm, which was placed in a heating jacket. The catalyst was packed in a volume of 1 mL, with inert packing at the bottom to position the catalyst bed in the constant temperature zone of the heating jacket.

[0042] Determination of initial activity and selectivity

[0043] The conditions for determining activity and selectivity used in the present application were as follows:

[0044] Composition of reaction gas (mol%)

[0045]

[0046]

[0047] The composition of the inlet and outlet gas of the reactor was continuously determined after the above reaction conditions were reached. The results were corrected for volume shrinkage and the selectivity was calculated according to the following formula:

[0048] Selectivity

[0049] where ΔEO is the difference in the concentration of ethylene oxide between the outlet gas and the inlet gas, and the average of more than 10 sets of test data was taken as the test result for that day.

[0050] The activity of the catalyst was measured by the level of the reaction temperature when a certain concentration of EO was reached.

[0051] The support samples used in the examples and comparative examples were all prepared from the same support formulation, and the details can be found in CN88100400.6, CN1634652A and US5063195, which will not be described in detail herein.

[0052] Example 1

[0053] In a glass beaker with stirring, 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 3.5 g of ethylenediaminetetraacetic acid and 179.8 g of deionized water were added to obtain a mixed solution; 72.2 g of silver oxalate was slowly added to the mixed solution, the temperature was kept below 40°C and stirring was continued until the silver oxalate was completely dissolved; then 2.25 mL of cesium nitrate aqueous solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL of ammonium perrhenate aqueous solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 10 mg of manganese dioxide particles (diameter of 30 nanometers) were added in sequence, and the mixture was uniformly mixed to prepare 300 g of impregnation solution for use.

[0054] Take 15 g of the carrier, put it into a glass container that can be vacuumed, and add the above impregnation solution to completely immerse the carrier. Vacuum to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to make silver catalyst example 1.

[0055] Example 2

[0056] In a glass beaker with stirring, add 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 3.5 g of ethylenediaminetetraacetic acid and 179.8 g of deionized water to obtain a mixture; slowly add 72.2 g of silver oxalate to the mixture, keep the temperature below 40°C and continue stirring until the silver oxalate is completely dissolved; then add 2.25 mL of cesium nitrate aqueous solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL of high-rhenium ammonium solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 10 mg of manganese dioxide particles (diameter of 60 nanometers) in sequence, mix well to make 300 g of impregnation solution for use.

[0057] Take 15 g of the carrier, put it into a glass container that can be vacuumed, and add the above impregnation solution to completely immerse the carrier. Vacuum to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to make silver catalyst example 2.

[0058] Example 3

[0059] In a glass beaker with stirring, add 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 3.5 g of ethylenediaminetetraacetic acid and deionized water to obtain a mixture; slowly add 72.2 g of silver oxalate to the mixture, keep the temperature below 40°C and continue stirring until the silver oxalate is completely dissolved; then add 2.25 mL of cesium nitrate aqueous solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL of high-rhenium ammonium solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 20 mg of manganese dioxide particles (diameter of 30 nanometers) in sequence, mix well to make 300 g of impregnation solution for use.

[0060] Take 15 g of the carrier, put it into a glass container that can be vacuumed, and add the above impregnation solution to completely immerse the carrier. Vacuum to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to make silver catalyst example 3.

[0061] Example 4

[0062] Into a stirred glass beaker, add 32.1 g ethylenediamine, 10.8 g ethanolamine, 3.5 g ethylenediaminetetraacetic acid and deionized water to make a mixture; slowly add 72.2 g silver oxalate into the mixture while keeping the temperature below 40°C and continue stirring until the silver oxalate is completely dissolved; then add 2.25 mL aqueous cesium nitrate solution (0.03995 g / mL in atomic weight of cesium), 2.78 mL aqueous ammonium perrhenate solution (0.0162 g / mL in atomic weight of rhenium), 20 mg manganese dioxide particles (60 nm in diameter) into the mixture one after another, mix well to make 300 g of impregnation solution.

[0063] Take 15 g of the support and put it into a glass container that can be evacuated, and add the above impregnation solution to completely immerse the support. Evacuate to above 10 mm Hg and keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated support sample in a stream of air at 350°C for about 2 minutes to make silver catalyst example 4.

[0064] Example 5

[0065] Into a stirred glass beaker, add 32.1 g ethylenediamine, 10.8 g ethanolamine, 3.5 g ethylenediaminetetraacetic acid and deionized water to make a mixture; slowly add 72.2 g silver oxalate into the mixture while keeping the temperature below 40°C and continue stirring until the silver oxalate is completely dissolved; then add 2.25 mL aqueous cesium nitrate solution (0.03995 g / mL in atomic weight of cesium), 2.78 mL aqueous ammonium perrhenate solution (0.0162 g / mL in atomic weight of rhenium), 20 mg manganese dioxide particles (60 nm in diameter) into the mixture one after another, mix well to make 300 g of impregnation solution.

[0066] Take 15 g of the support and put it into a glass container that can be evacuated, and add the above impregnation solution to completely immerse the support. Evacuate to above 10 mm Hg and keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated support sample in a stream of air at 350°C for about 2 minutes to make silver catalyst example 4.

[0067] Example 6

[0068] In a stirred glass beaker, add 32.1 g ethylenediamine, 10.8 g ethanolamine, 10.5 g ethylenediaminetetraacetic acid and 179.8 g deionized water to obtain a mixture; slowly add 72.2 g silver oxalate into the mixture, keep the temperature below 40°C and continuously stir until the silver oxalate is completely dissolved; then add 2.25 mL aqueous cesium nitrate solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL aqueous ammonium perrhenate solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 10 mg manganese dioxide particles (diameter of 60 nanometers) in sequence, mix well to prepare 300 g impregnation solution for use.

[0069] Take 15 g of the carrier, place it in a glass container capable of vacuum extraction, and add the above impregnation solution to completely immerse the carrier. Extract the vacuum to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by leaching. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to prepare silver catalyst example 6.

[0070] Example 7

[0071] In a stirred glass beaker, add 32.1 g ethylenediamine, 10.8 g ethanolamine, 10.5 g ethylenediaminetetraacetic acid and 179.8 g deionized water to obtain a mixture; slowly add 72.2 g silver oxalate into the mixture, keep the temperature below 40°C and continuously stir until the silver oxalate is completely dissolved; then add 2.25 mL aqueous cesium nitrate solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL aqueous ammonium perrhenate solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 20 mg manganese dioxide particles (diameter of 30 nanometers) in sequence, mix well to prepare 300 g impregnation solution for use.

[0072] Take 15 g of the carrier, place it in a glass container capable of vacuum extraction, and add the above impregnation solution to completely immerse the carrier. Extract the vacuum to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by leaching. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to prepare silver catalyst example 7.

[0073] Example 8

[0074] In a stirred glass beaker, add 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 10.5 g of ethylenediaminetetraacetic acid and 179.8 g of deionized water to obtain a mixture; slowly add 72.2 g of silver oxalate into the mixture, keep the temperature below 40°C and continuously stir until the silver oxalate is completely dissolved; then add 2.25 mL of aqueous cesium nitrate solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL of aqueous ammonium perrhenate solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 20 mg of manganese dioxide particles (diameter of 60 nm) in sequence, mix well to prepare 300 g of impregnation solution for use.

[0075] Take 15 g of the carrier and place it in a glass container that can be evacuated, and add the above impregnation solution to completely immerse the carrier. Evacuate to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to prepare silver catalyst example 8.

[0076] Example 9

[0077] In a stirred glass beaker, add 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 10.5 g of ethylenediaminetetraacetic acid and 179.8 g of deionized water to obtain a mixture; slowly add 72.2 g of silver oxalate into the mixture, keep the temperature below 40°C and continuously stir until the silver oxalate is completely dissolved; then add 2.25 mL of aqueous cesium nitrate solution (concentration of 0.03995 g / mL, based on the atomic weight of cesium), 2.78 mL of aqueous ammonium perrhenate solution (concentration of 0.0162 g / mL, based on the atomic weight of rhenium), 20 mg of manganese dioxide particles (diameter of 60 nm) in sequence, mix well to prepare 300 g of impregnation solution for use.

[0078] Take 15 g of the carrier and place it in a glass container that can be evacuated, and add the above impregnation solution to completely immerse the carrier. Evacuate to above 10 mmHg, keep for about 15 minutes, then remove the excess solution by decanting. Finally, place the impregnated carrier sample in an air stream at 350°C for about 2 minutes to prepare silver catalyst example 8.

[0079] Example 10

[0080] In a stirred glass beaker, 32.1 g of ethylenediamine, 10.8 g of ethanolamine, 3.5 g of nitrilotriacetic acid and 179.8 g of deionized water were added to obtain a mixture; 72.2 g of silver oxalate was slowly added to the mixture while maintaining the temperature below 40°C and continuously stirring to completely dissolve the silver oxalate; then 2.25 mL of aqueous cesium nitrate solution (0.03995 g / mL in terms of cesium atomic weight), 2.78 mL of aqueous ammonium perrhenate solution (0.0162 g / mL in terms of rhenium atomic weight), 10 mg of manganese dioxide particles (60 nm in diameter) were sequentially added and mixed to obtain 300 g of impregnation solution.

[0081] 15 g of the support was taken and placed in a glass container capable of being evacuated and the above impregnation solution was added to completely immerse the support. The container was evacuated to 10 mm Hg or more and maintained for about 15 minutes, after which the excess solution was drained. Finally, the impregnated support sample was heated in a stream of air at 350°C for about 2 minutes to obtain silver catalyst example 2.

[0082] Comparative Example 1

[0083] Comparative example 1 was identical to example 1 except that the chelating agent and manganese dioxide particles were not added.

[0084] Comparative Example 2

[0085] Comparative example 2 was identical to example 1 except that the manganese dioxide particles added had a diameter of 290 nm.

[0086] Comparative Example 3

[0087] Comparative example 3 was identical to example 1 except that the chelating agent was not added.

[0088] The silver catalysts of the examples and comparative examples were evaluated using a microreactor evaluation device to determine the performance of the catalyst samples under the aforementioned process conditions, and the results of the evaluation are shown in Table 1.

[0089] Table 1. Evaluation results on the 6th day for silver catalysts of comparative examples 1-3 and examples 1-10

[0090]

[0091]

[0092] As can be seen from Table 1, the initial reaction activity of the silver catalyst samples prepared using the process of adding a chelating agent and nanometer-sized manganese dioxide particles to the silver ammonia solution was significantly improved.

[0093] Embodiments of the application have been described above, as well as examples. None of the above description is exhaustive or complete with respect to the practice of the disclosed embodiments. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the before disclosure.

[0094] The endpoints of the ranges and any values described herein are not limited to the precise values recited as exactly that endpoint point, but rather are intended to cover values approximating that range or that point. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within the range. For values having a range, the endpoints of the ranges are included within

Claims

1. A silver catalyst for producing ethylene oxide by ethylene oxidation, characterized in that: The silver catalyst comprises an alumina carrier and silver, nano manganese dioxide and an additive supported thereon. The additive is an alkali metal additive and an optional rhenium additive and a co-additive thereof. Wherein, based on the total weight of the silver catalyst, the content of the silver is 2 to 39 wt%; the content of the nano manganese dioxide is 0.001 to 0.5 wt%; The silver catalyst is obtained by impregnating the alumina carrier in a silver ammonia solution, performing solid-liquid separation, and calcining. The silver ammonia solution comprises a silver-containing compound, a chelating agent, nano-manganese dioxide, an amine compound, water, an alkali metal additive, an optional rhenium additive, and a co-additive thereof; the chelating agent is selected from at least one of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and aminotriacetic acid. The diameter of the nano manganese dioxide is 1 to 100 nanometers.

2. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 1, wherein The content of silver is 10-35 wt%.

3. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 1, wherein The content of the nano manganese dioxide is 0.005-0.1 wt%.

4. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 3, wherein The content of the nano manganese dioxide is 0.01-0.05 wt%.

5. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 1, wherein The diameter of the nano manganese dioxide is 10 to 80 nanometers.

6. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 1, wherein The alumina carrier is a porous α-Al2O3 carrier, wherein the α-Al2O3 content is ≥90%, and has the following characteristics: a crushing strength of 20 to 200 N / particle; a specific surface area of ​​0.2 to 3.0 m 2 / g; water absorption rate ≥30%; pore volume is 0.30~0.85mL / g.

7. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 1, wherein Based on the total weight of the silver catalyst, the content of the alkali metal additive is 1 to 2000 ppm; the content of the rhenium metal in terms of atoms is 0 to 2000 ppm; and the content of the co-additive of the rhenium additive in terms of atoms is 0 to 2000 ppm.

8. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 7, wherein Based on the total weight of the silver catalyst, the content of the alkali metal additive is 5 to 1500 ppm; the content of the rhenium metal in terms of atoms is 100 to 1000 ppm; and the content of the co-additive of the rhenium additive in terms of atoms is 100 to 1000 ppm.

9. The silver catalyst for producing ethylene oxide by ethylene oxidation according to any one of claims 1 to 8, wherein Based on the total weight of the silver ammonia solution, the content of the chelating agent is 0.01-20.0 wt%.

10. The silver catalyst for producing ethylene oxide by ethylene oxidation according to claim 9, wherein Based on the total weight of the silver ammonia solution, the content of the chelating agent is 0.05-5.0wt%.

11. A method for preparing a silver catalyst for producing ethylene oxide by ethylene oxidation, characterized in that: The steps include: (1) obtaining a silver ammonia solution, the silver ammonia solution comprising a silver-containing compound, a chelating agent, nano manganese dioxide, an amine compound, water, an alkali metal additive, an optional rhenium additive and a co-additive thereof; the nano manganese dioxide having a diameter of 1 to 100 nanometers; and the chelating agent being at least one selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and aminotriacetic acid; (2) impregnating the α-Al2O3 carrier into the silver ammonia solution obtained in step (1), and then performing solid-liquid separation and calcination to obtain the silver catalyst.

12. The preparation method according to claim 11, wherein In step (1), the diameter of the nano manganese dioxide is 10 to 80 nanometers; based on the total weight of the silver catalyst, the amount of the nano manganese dioxide added is such that the content of the nano manganese dioxide in the silver catalyst is 0.001 to 0.5 wt%.

13. The preparation method according to claim 12, wherein The amount of the nano-manganese dioxide added is such that the content of the nano-manganese dioxide in the silver catalyst is 0.005-0.1 wt %.

14. The preparation method according to claim 13, wherein The amount of the nano-manganese dioxide added is such that the content of the nano-manganese dioxide in the silver catalyst is 0.01 to 0.05 wt %.

15. The preparation method according to claim 11, wherein In step (1), the content of the chelating agent is 0.01 to 20.0 wt % based on the total weight of the silver ammonia solution.

16. The preparation method according to claim 15, wherein The content of the chelating agent is 0.05-5.0 wt%.

17. The preparation method according to any one of claims 11 to 16, wherein: In step (1), the amine compound is selected from at least one of ammonia water, ethylamine, n-propylamine, ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, N,N-dimethylformamide, ethanolamine and propanolamine; the silver-containing compound is at least one of silver acetate, silver nitrate and silver oxalate; the content of the amine compound is 10 to 90 wt% based on the total weight of the silver ammonia solution, and the amount of the silver-containing compound added is such that the content of silver in the silver catalyst in terms of atoms is 2 to 39 wt%.

18. The preparation method according to claim 17, wherein The silver-containing compound is added in an amount such that the content of silver in the silver catalyst is 10 to 35 wt % in terms of atom.

19. The preparation method according to any one of claims 11 to 16, wherein: In step (1), the alkali metal promoter is selected from at least one compound of lithium, sodium, potassium, rubidium and cesium; the rhenium promoter is selected from at least one of rhenium oxide, perrhenic acid, cesium perrhenate, methyltrioxyrhenium (VII) and ammonium perrhenate; the co-promoter of the rhenium promoter is selected from at least one of salts or acids containing manganese, chromium, sulfur, cobalt, molybdenum and nickel; based on the total weight of the silver catalyst, the amount of the alkali metal promoter added is such that the content of the alkali metal in the silver catalyst is 1 to 2000 ppm; the amount of the rhenium promoter added is such that the content of rhenium metal in the silver catalyst, calculated on an atom basis, is 0 to 2000 ppm; the amount of the co-promoter of the rhenium promoter added is such that the content of the co-promoter of the rhenium promoter, calculated on an atom basis, is 0 to 2000 ppm in the silver catalyst.

20. The preparation method according to claim 19, wherein Based on the total weight of the silver catalyst, the amount of the alkali metal additive added is such that the content of the alkali metal in the silver catalyst is 5 to 1500 ppm; the amount of the rhenium additive added is such that the content of the rhenium metal in the silver catalyst, calculated on an atomic basis, is 100 to 1000 ppm; and the amount of the co-additive of the rhenium additive added is such that the content of the co-additive of the rhenium additive in the silver catalyst, calculated on an atomic basis, is 100 to 1000 ppm.

21. The preparation method according to any one of claims 11 to 16, wherein: In step (2), the immersion time is 10 to 300 minutes; The solid-liquid separation includes leaching and drying.

22. The preparation method according to claim 21, wherein The immersion is performed at a pressure below 100 mmHg.

23. The preparation method according to claim 21, wherein The drying process after leaching is carried out in air and / or inert gas atmosphere, the drying temperature is 50-120° C., and the drying time is 0.1-12 hours.

24. The preparation method according to any one of claims 11 to 16, wherein: In step (2), the roasting is carried out in air or a nitrogen-oxygen mixed gas with an oxygen content of no more than 21%; the roasting temperature is 100-600° C., and the roasting time is 0.5-120 minutes.

25. The preparation method according to claim 24, wherein The calcination temperature is 150-500° C., and the calcination time is 1-30 minutes.

26. The preparation method according to any one of claims 11 to 16, wherein: The α-Al2O3 carrier is a porous α-Al2O3 carrier, wherein the α-Al2O3 content is ≥90%, and has the following characteristics: a crushing strength of 20 to 200 N / particle; a specific surface area of ​​0.2 to 3.0 m 2 / g; water absorption rate ≥30%; pore volume is 0.30~0.85mL / g.

27. A silver catalyst for producing ethylene oxide by oxidation of ethylene obtained by the preparation method according to any one of claims 11 to 26.

28. Use of the silver catalyst for producing ethylene oxide by ethylene oxidation according to any one of claims 1 to 10 and 27 in the reaction of producing ethylene oxide by ethylene oxidation.

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