Low-sodium silver-containing raw material, preparation method thereof, silver impregnation liquid, silver catalyst and method for producing ethylene oxide through ethylene epoxidation

Abstract

The invention belongs to the field of industrial catalysts, and relates to a low-sodium silver-containing raw material, a preparation method thereof, a silver impregnation liquid, a silver catalyst and a method for producing ethylene oxide through ethylene epoxidation. The preparation method of the low-sodium silver-containing raw material comprises the following steps that I, a homogeneous solution A is obtained, the homogeneous solution A is a sodium removal agent water-based solution, and a sodium removal agent comprises organic acid, optional organic alcohol and optional organic ether; and II, treating a silver oxide raw material by adopting the homogeneous solution A obtained in the step I, and filtering out a liquid-phase component to obtain the low-sodium silver-containing raw material. According to the method, the silver oxide raw material is subjected to sodium removal treatment to obtain the low-sodium silver-containing raw material, the low-sodium silver-containing raw material is used for preparing the silver impregnation liquid, and the selectivity and activity of the prepared silver catalyst are further improved.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysts, specifically relating to a low-sodium silver-containing raw material for the epoxidation of ethylene to produce ethylene oxide and its preparation method, a silver impregnation solution containing the low-sodium silver-containing raw material, a silver catalyst prepared using the silver impregnation solution, and a method for the epoxidation of ethylene to produce ethylene oxide using the silver catalyst. Background Art

[0002] Silver catalysts are a key element in the ethylene oxidation to ethylene oxide industry. In the silver-catalyzed ethylene epoxidation reaction, the main factors affecting catalyst performance include the properties of the support, the properties of the metallic silver, and trace components. Among these, trace components have a significant impact on silver catalyst performance; the presence of harmful components can lead to a marked decrease in catalyst selectivity, activity, and lifetime.

[0003] Among trace components, alkali metals are the most common: cesium is a widely used and beneficial component for improving catalyst lifetime and selectivity; conversely, sodium, which is prevalent, has a detrimental effect on catalysts, such as reducing catalyst activity. Since sodium can be widely present in the production process of silver catalysts, measures must be taken to reduce or even eliminate its introduction.

[0004] Sodium in catalysts originates from two sources: introduction from silver feedstock and introduction from support feedstock. Introduction from silver feedstock stems from sodium residue introduced during the production of silver oxide feedstock. To address this issue, a common approach is to avoid using silver oxide feedstocks with high sodium residue levels, such as using silver oxalate feedstocks, which do not involve sodium in their production process. CN103906568A, US4746749A, and US2013109871A1 utilize the reaction of potassium oxalate and silver nitrate to produce silver oxalate feedstock; JP2014118587A utilizes the reaction of oxalic acid and silver nitrate to produce silver oxalate feedstock.

[0005] Although the aforementioned patent documents provide a production method for silver raw materials that does not introduce sodium impurities, they introduce other types of impurities, such as potassium and nitric acid. These new impurities will affect the reactivity, selectivity, and product quality of the ethylene epoxidation reaction to varying degrees. Summary of the Invention

[0006] In view of the current state of the technology, the inventors of this invention propose a scheme to reduce the sodium content of silver oxide raw material to low sodium silver content raw material through desodium treatment. The silver catalyst prepared by using the low sodium silver content raw material to prepare silver impregnation solution has further improved selectivity and activity.

[0007] To achieve the objectives of this invention, a first aspect of this invention provides a method for preparing a low-sodium silver-containing raw material for the epoxidation of ethylene to produce ethylene oxide, comprising the following steps:

[0008] Step I, obtaining homogeneous solution A, wherein homogeneous solution A is an aqueous solution of a sodium removal agent, wherein the sodium removal agent includes organic acid, optional organic alcohol and optional organic ether;

[0009] Step II: The silver oxide raw material is treated with the homogeneous solution A obtained in Step I, and the liquid phase components are filtered out to obtain the low-sodium silver-containing raw material.

[0010] A second aspect of the present invention provides a low-sodium silver-containing raw material prepared by the aforementioned preparation method, wherein the sodium content in the low-sodium silver-containing raw material is less than 30 ppm.

[0011] A third aspect of the present invention provides a silver impregnation solution for the epoxidation of ethylene to produce ethylene oxide, comprising:

[0012] 1) The low-sodium silver-containing raw material mentioned above;

[0013] 2) Organic amines;

[0014] 3) Water; and

[0015] 4) Additives.

[0016] A fourth aspect of the present invention provides a method for preparing a silver catalyst for the oxidation of ethylene to ethylene oxide, comprising the following steps:

[0017] (1) Provide the silver impregnation solution;

[0018] (2) Impregnate the inert carrier with the silver impregnation solution from step (1), and after leaching and separation, dry the resulting solid phase.

[0019] (3) The dried solid phase is activated to obtain the silver catalyst.

[0020] A fifth aspect of the present invention provides a silver catalyst prepared by the aforementioned preparation method.

[0021] A sixth aspect of the present invention provides a method for producing ethylene oxide by ethylene oxidation, the method comprising: contacting a mixture of ethylene and oxygen, or a mixture of ethylene and oxygen-containing gas, with the silver catalyst in the gas phase to carry out an epoxidation reaction to obtain ethylene oxide.

[0022] This invention obtains a low-sodium silver-containing raw material by desodiuming silver oxide raw material, which is then used to prepare a silver impregnation solution. The resulting silver catalyst exhibits further improved selectivity and activity.

[0023] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] To achieve the objectives of this invention, a first aspect of this invention provides a method for preparing a low-sodium silver-containing raw material for the epoxidation of ethylene to produce ethylene oxide, comprising the following steps:

[0026] Step I, obtaining homogeneous solution A, wherein homogeneous solution A is an aqueous solution of a sodium removal agent, wherein the sodium removal agent includes organic acid, optional organic alcohol and optional organic ether;

[0027] Step II: The silver oxide raw material is treated with the homogeneous solution A obtained in Step I, and the liquid phase components are filtered out to obtain the low-sodium silver-containing raw material.

[0028] In this invention, "filtration" refers to centrifugation or filtration, which retains the solid phase components and discards the liquid phase components.

[0029] According to the present invention, preferably, in step I, based on the total weight of homogeneous solution A, the content of the organic acid is 1-25 wt%, preferably 12-18 wt%, the content of the organic alcohol is 0-5 wt%, preferably 0.01-1 wt%, and the content of the organic ether is 0-2 wt%, preferably 0.01-0.5 wt%.

[0030] According to the present invention, preferably, in step I, the organic acid is oxalic acid and / or acetic acid, more preferably oxalic acid; the organic alcohol is at least one selected from methanol, ethanol, propanol, ethylene glycol, propylene glycol, and glycerol; the organic ether is an ethylene glycol condensate and / or a glycerol condensate, preferably an ethylene glycol condensate, and more preferably, the ethylene glycol condensate is at least one selected from chain, cyclic, and dendritic ethylene glycol condensates.

[0031] According to the present invention, preferably, the sodium content of the silver oxide raw material is not higher than 2000 ppm, and more preferably 0 to 1000 ppm.

[0032] Preferably, the silver oxide raw material is in powder form; the particle size of the silver oxide raw material powder is preferably less than 50 mesh, more preferably less than 100 mesh.

[0033] According to the present invention, preferably, in step II, the molar ratio of organic acid to silver oxide raw material in homogeneous solution A is 1.0 to 1.2, more preferably 1.05 to 1.1.

[0034] According to the present invention, preferably, in step II, the treatment involves fully contacting and reacting the homogeneous solution A and the silver oxide raw material, and the reaction conditions include: a temperature of 30-80°C and a time of 0.5-2 hours.

[0035] In this invention, "processing" may or may not include a stirring operation.

[0036] According to the present invention, preferably, step II further includes drying the solid phase material after filtering out the liquid phase components.

[0037] A second aspect of the present invention provides a low-sodium silver-containing raw material prepared by the aforementioned preparation method, wherein the sodium content in the low-sodium silver-containing raw material is less than 30 ppm.

[0038] A third aspect of the present invention provides a silver impregnation solution for the epoxidation of ethylene to produce ethylene oxide, comprising:

[0039] 1) The low-sodium silver-containing raw material mentioned above;

[0040] 2) Organic amines;

[0041] 3) Water; and

[0042] 4) Additives.

[0043] According to the present invention, preferably, the organic amine compound can be any organic compound capable of forming a silver amine complex, preferably at least one of methylamine, ethylamine, propylamine, butylamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine and ethanolamine, more preferably ethylenediamine;

[0044] According to the present invention, preferably, the additives include at least one of alkali metal additives, alkaline earth metal additives, rhenium additives, and co-additives thereof.

[0045] Preferably, the alkali metal auxiliary is at least one of lithium, sodium, potassium, rubidium and cesium sulfate, nitrate and hydroxide, preferably cesium sulfate or cesium nitrate or a combination thereof.

[0046] Preferably, the alkaline earth metal auxiliaries are at least one selected from the following: sulfates, nitrates, carbonates, oxides, oxalates, and acetates of magnesium, calcium, strontium, and barium.

[0047] Preferably, the rhenium additive is at least one of rhenium oxide, ammonium perrhenate, cesium perrhenate, potassium perrhenate, and perrhenic acid, preferably a compound of strontium and barium, and more preferably barium acetate or strontium acetate or a mixture thereof.

[0048] Preferably, the co-additive of the rhenium additive is derived from at least one of group 6B metal oxides, oxyacids, and oxyacid salts, and can be tungsten or molybdenum oxides, oxyacids, oxyacid salts, or mixtures thereof, preferably tungstic acid, molybdic acid, or mixtures thereof.

[0049] A fourth aspect of the present invention provides a method for preparing a silver catalyst for the oxidation of ethylene to ethylene oxide, comprising the following steps:

[0050] (1) Provide the silver impregnation solution;

[0051] (2) Impregnate the inert carrier with the silver impregnation solution from step (1), and after leaching and separation, dry the resulting solid phase.

[0052] (3) The dried solid phase is activated to obtain the silver catalyst.

[0053] According to the present invention, preferably, in step (1), the inert support is α-alumina.

[0054] According to the present invention, preferably, in step (2), the activation conditions include: the activation atmosphere is an oxygen-containing mixed gas, preferably a nitrogen-oxygen mixed gas flow with an oxygen content of not more than 21%, the temperature is 150-600°C, preferably 180-450°C, and the time is 1-120 minutes, preferably 2-40 minutes.

[0055] A fifth aspect of the present invention provides a silver catalyst prepared by the aforementioned preparation method.

[0056] According to the present invention, preferably, based on the total weight of the silver catalyst, the silver catalyst contains 4-38 wt% silver, preferably 7-31 wt%; alkali metals contain 1-2000 ppm alkali metals, preferably 4-1400 ppm alkali metals; alkaline earth metals contain 50-3000 ppm alkaline earth metals, preferably 100-2500 ppm alkaline earth metals; rhenium metals contain 1-2000 ppm rhenium metals, preferably 50-1000 ppm rhenium additives; and the co-additives of rhenium additives contain 1-300 ppm rhenium metals, preferably 30-200 ppm rhenium metals.

[0057] A sixth aspect of the present invention provides a method for producing ethylene oxide by ethylene oxidation, the method comprising: contacting a mixture of ethylene and oxygen, or a mixture of ethylene and oxygen-containing gas, with the silver catalyst in the gas phase to carry out an epoxidation reaction to obtain ethylene oxide.

[0058] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0059] Determination of sodium content:

[0060] In this invention, the sodium content is determined by atomic emission spectrometry. During the test, the sample is dissolved in nitric acid / ammonia, silver is removed by acetic acid precipitation, and then diluted to a sodium concentration range of 5–200 ppm. The sodium content is then determined using the external standard method.

[0061] Determination of catalyst performance:

[0062] The activity and selectivity of various silver catalysts of the present invention were tested using a laboratory microreactor evaluation apparatus. The reactor used in the microreactor evaluation apparatus was a stainless steel reaction tube with an inner diameter of 4 mm, which was placed in a heating jacket. The catalyst loading volume was 1 ml, and there was inert packing material at the bottom of the reaction tube. The catalyst bed was located in the constant temperature zone of the heating jacket.

[0063] The selective measurement conditions used in this invention are shown in Table 1.

[0064] Table 1: Reaction conditions for catalysts

[0065]

[0066] Once the above conditions are met and the reactor stabilizes, the composition of the gas at the reactor inlet and outlet is measured simultaneously. Based on the measurement results, the volume shrinkage correction is applied, and the selectivity is calculated using the following formula:

[0067] Selective Where ΔEO is the difference in ethylene oxide concentration between the reactor outlet gas and the reactor inlet gas, and ΔCO2 is the difference in carbon dioxide concentration between the reactor outlet gas and the reactor inlet gas, and no less than 10 sets of data are taken as the experimental results for the day.

[0068] Comparative Example 1

[0069] Mix 20g of powdered silver oxide with 80g of distilled water, stir at 40℃ for 1h, filter to remove the filtrate and retain the solid phase, and dry to obtain the silver-containing raw material.

[0070] Comparative Example 2

[0071] The method described in CN103906568A is as follows: 86.1 kg of oxalic acid dihydrate was dissolved in 517 kg of deionized water in a heatable stirred tank. During the dissolution process, 145.2 kg of a 47.5 wt% potassium hydroxide aqueous solution (deionized water) was rapidly added using a coarse weighing metering device. This amount corresponds to 90% of the required equimolar amount of alkali (oxalic acid dihydrate: KOH = 1:2). The resulting solution was heated to 40°C in the heatable stirred tank using a hot water circuit, which was in turn heated by steam. The temperature was determined using an internal temperature measurement device, i.e., the temperature of the solution was directly measured. Subsequently, a 47.5 wt% potassium hydroxide aqueous solution was slowly added using a fine weighing metering device. The addition of potassium hydroxide solution was stopped when the second equivalence point of oxalic acid deprotonation was reached. The endpoint, i.e., the second equivalence point, was determined by measuring the pH value in the stirred tank using a glass electrode. Here, the pH value was monitored online from the start of adding the potassium hydroxide solution. According to the present invention, when the pH value reaches 8.52, the addition of potassium hydroxide solution is stopped; an aqueous solution of silver nitrate at approximately 44°C is placed in a stirred sedimentation vessel with a volume of 1800L and maintained at approximately 44°C. The silver nitrate solution is prepared by dissolving 219 kg AgNO3 in 597 kg H2O (deionized water); the prepared potassium oxalate solution is transferred via a downwardly inclined conduit to the stirred sedimentation vessel containing the silver nitrate solution, and the temperature is maintained at approximately 44°C for 4 hours. Precipitation of silver oxalate is initiated by the addition of potassium oxalate solution. After a precipitation time of 4 hours and a further stirring time of 1 hour, the reaction is completed; the obtained precipitated solid is filtered out on a membrane filter press and washed with deionized water until the conductivity of the washings reaches (not exceeding) 40 μSiemens / cm. The filter cake is then further pressed under a water pressure of 4 bar until no more water flows out of the filter press's washing water pipe. The filter cake obtained in this manner is removed and weighed. The residual moisture content of the filter cake is determined using a moisture analyzer. In this way, approximately 220 kg of moist silver oxalate with a residual moisture content of approximately 15% by weight was obtained, and then dried to obtain silver oxalate.

[0072] Comparative Example 3

[0073] The preparation method adopted is JP2014118587A. Specifically, using a 500cc plastic container containing 28.5g of silver nitrate, silver nitrate solution was added to 71.5g of 28.5wt% ion-exchanged water. Separately, 13g of oxalic acid was added to a 500cc plastic container containing another 13wt% oxalic acid solution, and 87g of ion-exchanged water was added. Then, the entire silver nitrate solution was stirred (250rpm) using the aforementioned magnetic stirrer, with all the oxalic acid solution added to the silver nitrate solution, for 3 hours. A white precipitate of silver oxalate was observed. The liquid phase was removed by filtration, and the solid phase was dried to obtain silver oxalate.

[0074] Example 1

[0075] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate and 80g of distilled water, stirred at 40 degrees Celsius for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0076] Example 2

[0077] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 2g of glycerol and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0078] Example 3

[0079] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 1g of polyethylene glycol-20000 and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0080] Example 4

[0081] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 1g of polyethylene glycol-20000, 2g of ethylene glycol, and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0082] Example 5

[0083] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 1g of polyethylene glycol-1000, 2g of glycerol and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0084] Example 6

[0085] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 1g of polyethylene glycol-20000, 2g of glycerol and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0086] Example 7

[0087] 20g of powdered silver oxide was mixed with 12g of oxalic acid dihydrate, 1g of ethanol and 80g of distilled water. The mixture was stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0088] Example 8

[0089] 20g of powdered silver oxide was mixed with 10.5g of acetic acid and 80g of distilled water, stirred at 40℃ for 1 hour, filtered to remove the filtrate and retain the solid phase, and dried to obtain a low-sodium silver-containing raw material.

[0090] Catalyst preparation:

[0091] Add 31g of ethylenediamine and 180g of deionized water to a stirred glass beaker to obtain a homogeneous mixture. Add 72g of the low-sodium silver-containing raw material prepared in Examples 1-7 (173g of deionized water and 79g of the prepared low-sodium silver-containing raw material in Example 8) at 10°C and stir continuously until completely dissolved. Then add 2.3ml of cesium nitrate aqueous solution (0.040g / mL, based on the weight of cesium) and 2.8mL of ammonium perrhenate aqueous solution (0.016g / mL, based on the weight of rhenium), mix well and set aside. Take 15g of porous α-alumina support and immerse it in the above impregnation solution at a pressure not exceeding 10mmHg for at least 15 minutes. After removing and draining the impregnated support, heat-treat it in an air stream at 280°C for 3 minutes and cool it to obtain silver catalyst products S1 to S8.

[0092] Comparative catalyst preparation:

[0093] Add 31g of ethylenediamine, 33g of oxalic acid dihydrate, and 164g of deionized water to a stirred glass beaker to obtain a homogeneous mixture. Add 55g of the silver-containing raw material prepared from Comparative Example 1 above at 10°C and stir continuously until completely dissolved. Then add 2.3ml of cesium nitrate aqueous solution (0.040g / mL, based on the weight of cesium) and 2.8mL of ammonium perrhenate aqueous solution (0.016g / mL, based on the weight of rhenium), mix well and set aside. Take 15g of porous α-alumina support and immerse it in the above impregnation solution at a pressure not exceeding 10mmHg for at least 15 minutes. After removing and draining the impregnated support, heat-treat it in an air stream at 280°C for 3 minutes and cool it to obtain the finished silver catalyst DS1.

[0094] Add 31g of ethylenediamine, 33g of oxalic acid dihydrate, and 164g of deionized water to a stirred glass beaker to obtain a homogeneous mixture. Add 55g of silver oxalate raw material prepared from Comparative Examples 2-3 above at 10°C and stir continuously until completely dissolved. Then add 2.3ml of cesium nitrate aqueous solution (0.040g / mL, based on the weight of cesium) and 2.8mL of ammonium perrhenate aqueous solution (0.016g / mL, based on the weight of rhenium), mix well and set aside. Take 15g of porous α-alumina support and immerse it in the above impregnation solution at a pressure not exceeding 10mmHg for at least 15 minutes. After removing and draining the impregnated support, heat-treat it in an air stream at 280°C for 3 minutes and cool it to obtain the silver catalyst products DS2 to DS3.

[0095] Test Example 1

[0096] The sodium content in the silver impregnation solutions obtained in each comparative example and embodiment was determined by atomic emission spectrometry, and the data are shown in Table 2.

[0097] Table 2: Sodium content in silver immersion solution

[0098]

[0099] Test Example 2

[0100] The performance of the silver catalysts obtained in each comparative example and embodiment was determined using a microreactor evaluation device under the above process conditions. The data results seven days after the start of the reaction are shown in Table 3.

[0101] Table 3: Performance Measurement Results of Catalysts

[0102]

[0103]

[0104] As shown in Table 3, compared with Comparative Example 1 (which did not undergo sodium removal treatment), the sodium content in Examples 1-8 was reduced by more than 90% in the impregnation solution with the same silver content. Correspondingly, the initial catalyst temperature decreased by 1-2°C, and the initial selectivity increased by 0.3-0.5 percentage points. Compared with Comparative Examples 2-3, the corresponding initial catalyst temperature decreased by 2-4°C, and the initial selectivity increased by 0.5-0.7 percentage points.

[0105] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0106] 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.

Claims

1. A method for preparing a low-sodium silver-containing raw material for the epoxidation of ethylene to produce ethylene oxide, characterized in that, Includes the following steps: Step I, obtaining homogeneous solution A, wherein homogeneous solution A is an aqueous solution of a sodium removal agent, wherein the sodium removal agent includes organic acid, optional organic alcohol and optional organic ether; Step II: The silver oxide raw material is treated with the homogeneous solution A obtained in Step I, and the liquid phase components are filtered out to obtain the low-sodium silver-containing raw material.

2. The preparation method according to claim 1, wherein, In step I, based on the total weight of homogeneous solution A, the content of the organic acid is 1-25 wt%, preferably 12-18 wt%, the content of the organic alcohol is 0-5 wt%, preferably 0.01-1 wt%, and the content of the organic ether is 0-2 wt%, preferably 0.01-0.5 wt%.

3. The preparation method according to claim 1, wherein, In step I, the organic acid is oxalic acid and / or acetic acid, preferably oxalic acid; the organic alcohol is at least one of methanol, ethanol, propanol, ethylene glycol, propylene glycol, and glycerol; the organic ether is an ethylene glycol condensate and / or a glycerol condensate, preferably an ethylene glycol condensate, and more preferably, the ethylene glycol condensate is at least one of chain, cyclic, and dendritic ethylene glycol condensates.

4. The preparation method according to claim 1, wherein, In step II, the sodium content of the silver oxide raw material is no higher than 2000 ppm, preferably 0 to 1000 ppm; Preferably, the silver oxide raw material is in powder form; the particle size of the silver oxide raw material powder is preferably less than 50 mesh, more preferably less than 100 mesh.

5. The preparation method according to claim 1, wherein, In step II, the molar ratio of organic acid to silver oxide raw material in homogeneous solution A is 1.0 to 1.2, preferably 1.05 to 1.

1.

6. The preparation method according to claim 1, wherein, In step II, the treatment involves fully contacting and reacting the homogeneous solution A and the silver oxide raw material. The reaction conditions include a temperature of 30–80°C and a time of 0.5–2 hours.

7. The preparation method according to claim 1, wherein, Step II also includes drying the solid phase material after filtering out the liquid phase components.

8. A low-sodium silver-containing raw material prepared by the preparation method according to any one of claims 1-7, characterized in that, The sodium content in the low-sodium silver-containing raw material is less than 30 ppm.

9. A silver impregnation solution for the epoxidation of ethylene to produce ethylene oxide, characterized in that, include: 1) The low-sodium silver-containing raw material as described in claim 8; 2) Organic amines; 3) Water; as well as 4) Additives.

10. The silver impregnation solution for the epoxidation of ethylene to produce ethylene oxide according to claim 9, wherein, The organic amine is at least one selected from methylamine, ethylamine, propylamine, butylamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine and ethanolamine, preferably ethylenediamine; The additives include at least one of alkali metal additives, alkaline earth metal additives, rhenium additives, and their co-additives; Preferably, the alkali metal auxiliary is at least one selected from lithium, sodium, potassium, rubidium and cesium sulfate, nitrate and hydroxide; Preferably, the alkaline earth metal auxiliaries are at least one selected from the following: sulfates, nitrates, carbonates, oxides, oxalates, and acetates of magnesium, calcium, strontium, and barium. Preferably, the rhenium additive is at least one selected from rhenium oxide, ammonium perperurate, cesium perperurate, potassium perperurate, and perperuric acid; Preferably, the co-additive of the rhenium additive is derived from at least one of group 6B metal oxides, oxyacids, and oxyacid salts.

11. A method for preparing a silver catalyst for the oxidation of ethylene to ethylene oxide, characterized in that, Includes the following steps: (1) Provide the silver impregnation solution according to claim 9 or 10; (2) Impregnate the inert carrier with the silver impregnation solution from step (1), and after leaching and separation, dry the resulting solid phase. (3) The dried solid phase is activated to obtain the silver catalyst.

12. The preparation method according to claim 11, wherein, In step (1), the inert support is α-alumina.

13. The preparation method according to claim 11, wherein, In step (2), the activation conditions include: the activation atmosphere is an oxygen-containing mixed gas, preferably a nitrogen-oxygen mixed gas with an oxygen content of no more than 21%, the temperature is 150-600℃, preferably 180-450℃, and the time is 1-120 minutes, preferably 2-40 minutes.

14. A silver catalyst prepared by the preparation method according to any one of claims 11-13.

15. The silver catalyst according to claim 14, wherein, Based on the total weight of the silver catalyst, the silver catalyst contains 4-38 wt% silver, preferably 7-31 wt%; alkali metals contain 1-2000 ppm alkali metals, preferably 4-1400 ppm alkali metals; alkaline earth metals contain 50-3000 ppm alkaline earth metals, preferably 100-2500 ppm alkaline earth metals; rhenium metals contain 1-2000 ppm rhenium metals, preferably 50-1000 ppm rhenium additives; and the co-additives of rhenium additives contain 1-300 ppm rhenium metals, preferably 30-200 ppm rhenium metals.

16. A method for producing ethylene oxide by ethylene oxidation, characterized in that, The method comprises: in the gas phase, contacting a mixture of ethylene and oxygen, or a mixture of ethylene and oxygen-containing gas, with the silver catalyst of claim 14 or 15 to perform an epoxidation reaction to obtain ethylene oxide.

Images