Silver catalyst for production of ethylene oxide by ethylene epoxidation, and preparation method therefor and use thereof

Abstract

The present invention belongs to the field of catalysts, and relates to a silver catalyst for the production of ethylene oxide by ethylene epoxidation, characterized in that the silver catalyst comprises a porous inert carrier, metallic silver, a high-valence transition metal element, and a co-auxiliary element, and the high-valence transition metal element is closely associated with the metallic silver in the form of a compound, wherein based on the total weight of the silver catalyst, the silver content, calculated as elemental silver, is 10-40 wt%, the high-valence transition metal element is a molybdenum element and / or a tungsten element, and the content of the high-valence transition metal element in the catalyst is such that the weight ratio of the molybdenum element, the tungsten element, and the silver element satisfies the following relationship: MMo is 0-0.0021, MW is 0-0.0053, and F1 is 0.0015-0.0053, wherein MMo and MW are the weight ratio of the molybdenum element to the silver element in the catalyst and the weight ratio of the tungsten element to the silver element in the catalyst respectively, and F1=MW+2.52MMo, wherein the silver catalyst has a tungsten element retention rate and / or a molybdenum element retention rate of not less than 70%, preferably not less than 80%, and more preferably not less than 85% after being subjected to a water‑leaching treatment. In the present invention, by controlling the content of the high-valence transition metal element, the silver catalyst has the characteristics of rapidly reaching a high-selectivity state during the initial stage of operation.

Description

Silver catalysts for ethylene epoxidation to ethylene oxide, their preparation methods and applications Technical Field

[0001] This invention belongs to the field of catalysts, and more specifically, relates to a silver catalyst for the epoxidation of ethylene to produce ethylene oxide, a method for preparing the silver catalyst for the epoxidation of ethylene to produce ethylene oxide, a silver catalyst obtained by the method, a method for the epoxidation of ethylene to produce ethylene oxide, and the use of the silver catalyst in the method for the epoxidation of ethylene to produce ethylene oxide. Background Technology

[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; suitable trace components can greatly improve catalyst performance.

[0003] Among trace components, high-valence metal elements are recognized as effective components. Group VIB elements (including molybdenum and tungsten) have been used in numerous related patents due to their variable valence characteristics. When appropriate precursors are selected and suitable amounts are used, molybdenum and tungsten can form oxide particles physically bonded to metallic silver in the silver catalyst production process. This alters the redox properties of metallic silver through electronic effects, thereby improving the performance of the silver catalyst.

[0004] In existing patent applications, small amounts of tungsten and molybdenum are added to form a homogeneous dispersion through chemical bonding. In most patent applications, only small amounts of tungsten and molybdenum are added as conventional additives. For example, a low-tungsten scheme is used in patent application US20160297781A1, and a low-molybdenum scheme is used in application US20130296587; the mass fraction of tungsten / molybdenum added in these applications does not exceed 300 ppm.

[0005] While the aforementioned patent documents provide solutions involving molybdenum or tungsten, these require over 100 hours to achieve optimal catalyst performance. Therefore, it is necessary to provide a solution for catalysts used in the epoxidation of ethylene to ethylene oxide that can rapidly reach optimal performance. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a silver catalyst for the epoxidation of ethylene to produce ethylene oxide. By controlling the high-valence transition metal elements and their content, the performance of the silver catalyst is enhanced, enabling the catalyst to reach its optimal performance in a short time and quickly achieve high selectivity.

[0007] To achieve the above objectives, a first aspect of the present invention provides a silver catalyst for the epoxidation of ethylene to produce ethylene oxide, the silver catalyst comprising a porous inert support, metallic silver, a high-valence transition metal element, and a co-promoter element;

[0008] In this catalyst, based on the total weight of the silver catalyst, the silver content (calculated as elemental silver) is 10-40 wt%. The high-valence transition metal elements are molybdenum and / or tungsten, and the content of these high-valence transition metal elements in the catalyst ensures that the weight ratio of molybdenum, tungsten, and silver satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053; where M Mo M W These represent the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, F1 = M. W +2.52M Mo ;

[0009] Among them, after water leaching treatment, the silver catalyst has a tungsten retention rate and / or molybdenum retention rate of not less than 70%, preferably not less than 80%, and more preferably not less than 85%.

[0010] A second aspect of the present invention provides a method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide, characterized by comprising the following steps:

[0011] a. The high-valence transition metal precursor is pretreated by adding one or more silver-containing compounds to an aqueous solution of the high-valence transition metal precursor and heating it for a period of time followed by cooling.

[0012] b. Prepare an impregnation solution by mixing a pretreated high-valence transition metal precursor with one or more silver-containing compounds, organic amine compounds, one or more co-auxiliaries, and water.

[0013] c. Vacuum impregnate the porous inert support with an impregnation solution, leach and separate the impregnated support, and then dry the resulting impregnated support.

[0014] d. The dried impregnated support is thermally activated to obtain a silver catalyst;

[0015] The addition of high-valence transition metal precursors ensures that the weight ratio of molybdenum, tungsten, and silver in the catalyst satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053, where M... Mo M WThese represent the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, F1 = M. W +2.52M Mo .

[0016] A third aspect of the present invention provides a silver catalyst prepared by the preparation method described herein.

[0017] A fourth aspect of the present invention provides a method for producing ethylene oxide by epoxidation of ethylene, comprising oxidizing ethylene with oxygen in the presence of the silver catalyst described in the present invention and / or the silver catalyst prepared by the preparation method described in the present invention.

[0018] The fifth aspect of the invention provides the use of the silver catalyst described in the invention and / or the silver catalyst prepared by the preparation method described in the invention in the epoxidation of ethylene to produce ethylene oxide.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0021] Figure 1 is a comparison chart of the increase in catalyst selectivity between Example 5 and Comparative Example 2.

[0022] Figure 2 is a comparison chart of the increase in catalyst selectivity between Example 3 and Comparative Example 5. Detailed Implementation

[0023] 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. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of this invention are still within the scope of protection of this invention.

[0024] The first aspect of the present invention provides a silver catalyst for the epoxidation of ethylene to produce ethylene oxide, characterized in that the silver catalyst contains a porous inert support, metallic silver, a high-valence transition metal element, and a co-promoter element;

[0025] Based on the total weight of the silver catalyst, the silver content (calculated as elemental silver) is 10-40 wt%. The high-valence transition metal elements are molybdenum and / or tungsten. The content of these high-valence transition metal elements in the catalyst ensures that the weight ratio of molybdenum, tungsten, and silver satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053; where M Mo M WThese represent the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, F1 = M. W +2.52M Mo ;

[0026] Among them, after water leaching treatment, the silver catalyst has a tungsten retention rate and / or molybdenum retention rate of not less than 70%, preferably not less than 80%, and more preferably not less than 85%.

[0027] According to the present invention, metallic silver generally exists in the form of elemental silver in silver catalysts.

[0028] According to the present invention, high-valence transition metal elements refer to transition metal elements with a valence higher than +4, such as group VIB metals, including molybdenum and tungsten. In silver catalysts, high-valence transition metal elements can be tightly bonded to metallic silver in the form of compounds.

[0029] According to the present invention, by controlling the content of high-valence transition metal elements in the silver catalyst, the silver catalyst can rapidly reach a high selectivity state in the initial stage of use.

[0030] According to the present invention, the coefficients M corresponding to tungsten and molybdenum in factor F1 are Mo M W It is derived from the equivalent weight ratio of the two elements under the same performance of the catalyst.

[0031] In an embodiment of the present invention, the weight ratio of molybdenum, tungsten, and silver in the silver catalyst can satisfy the following relationship: M Mo For 0-0.0020, M W The range is 0-0.0050 for F1 and 0.0020-0.0050 for M; Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0032] In an embodiment of the present invention, the weight ratio of molybdenum, tungsten, and silver in the silver catalyst can satisfy the following relationship: M Mo For 0-0.0019, M W The range is 0-0.0047, and F1 is 0.0022-0.0047; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0033] In an embodiment of the present invention, the weight ratio of molybdenum, tungsten, and silver in the silver catalyst can satisfy the following relationship: M Mo For 0-0.0018, M W The range is 0-0.0045, and F1 is 0.0026-0.0045; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0034] In an embodiment of the present invention, the weight ratio of molybdenum, tungsten, and silver in the silver catalyst can satisfy the following relationship: M Mo For 0-0.0017, M W The range is 0-0.0042, and F1 is 0.0029-0.0042; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0035] In an embodiment of the present invention, the weight ratio of molybdenum, tungsten, and silver in the silver catalyst can satisfy the following relationship: M Mo For 0-0.0015, M W The range is 0-0.0039, and F1 is 0.0033-0.0039; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0036] According to the present invention, the co-agent element includes at least one selected from alkali metal elements, alkaline earth metal elements, and rhenium. The alkali metal element may be at least one selected from lithium, sodium, potassium, rubidium, and cesium, preferably at least one selected from potassium and cesium. The alkaline earth metal element may be at least one selected from magnesium, calcium, strontium, and barium, preferably at least one selected from barium and strontium.

[0037] According to the present invention, based on the total weight of the silver catalyst, the content of alkali metal elements can be 1-2000 ppm, preferably 4-1400 ppm. The content of alkaline earth metal elements can be 50-3000 ppm, preferably 100-2500 ppm. The content of rhenium can be 1-2000 ppm, preferably 50-1000 ppm.

[0038] According to the present invention, the silver content, based on the total weight of the silver catalyst, can be 10-40 wt%, preferably 14-38 wt%, more preferably 20-36 wt%, and particularly preferably 25-32 wt%.

[0039] According to the present invention, tungsten and molybdenum elements in the silver catalyst are tightly bonded to elemental silver. The structural characteristics of the silver catalyst can be characterized by the retention rates of tungsten and / or molybdenum elements after water leaching treatment. After water leaching treatment, the retention rates of tungsten and / or molybdenum elements in the silver catalyst of the present invention are each not less than 70%, preferably not less than 80%, more preferably not less than 85%, that is, the water leaching rates of tungsten and / or molybdenum elements are each not more than 30%, preferably not more than 20%, more preferably not more than 15%.

[0040] It should be noted that "after water leaching treatment, the retention rates of tungsten and / or molybdenum in the silver catalyst are each not less than 70%, preferably not less than 80%, and more preferably not less than 85%" means that when the silver catalyst contains tungsten but not molybdenum, the retention rate of tungsten after water leaching treatment is not less than 70%, preferably not less than 80%, and more preferably not less than 85%; when the silver catalyst contains molybdenum but not tungsten, the retention rate of molybdenum after water leaching treatment is not less than 70%, preferably not less than 80%, and more preferably not less than 85%; and when the silver catalyst contains both molybdenum and tungsten, the retention rates of molybdenum and molybdenum after water leaching treatment are both not less than 70%, preferably not less than 80%, and more preferably not less than 85%.

[0041] In this invention, the water leaching treatment of the silver catalyst refers to completely immersing a certain amount of catalyst sample in deionized water, maintaining the temperature at 40-120°C for 10-90 minutes, then removing the sample and drying it (e.g., at 90-120°C) before grinding it into powder. Samples before and after the water leaching treatment are taken separately, and the silver content is determined by potassium thiocyanate titration, and the molybdenum and tungsten content is determined by ICP-OES (inductively coupled plasma optical emission spectrometry), relative to the weight of the silver catalyst. The tungsten or molybdenum retention rate (%) of the silver catalyst after water leaching treatment is calculated based on the following formula: The content of tungsten and molybdenum is relative to the weight of the silver catalyst.

[0042] Since the silver in the silver catalyst exists in the form of elemental silver, the silver does not dissolve in water.

[0043] According to the present invention, suitable porous inert supports include alumina, silica, titanium dioxide, zirconium dioxide, other supports suitable for the purposes of the present invention, and combinations thereof, preferably including porous α-alumina supports, more preferably including those with a specific surface area of ​​0.2-2.0 m². 2 Porous α-alumina supports with a surface area of ​​0.35–0.85 mL / g and a pore volume of 0.35–0.85 mL / g. Specific surface area was determined according to the method described in standard ISO 9277. Pore volume was determined by mercury porosimetry.

[0044] According to the present invention, the content of the porous inert support can be 60-90 wt%, for example 65-85 wt%, based on the total weight of the silver catalyst.

[0045] A second aspect of the present invention provides a method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide, characterized by comprising the following steps:

[0046] a. The high-valence transition metal precursor is pretreated by adding one or more silver-containing compounds to an aqueous solution of the high-valence transition metal precursor and heating it for a period of time followed by cooling.

[0047] b. Prepare an impregnation solution by mixing a pretreated high-valence transition metal precursor with one or more silver-containing compounds, organic amine compounds, one or more co-auxiliaries, and water.

[0048] c. Vacuum impregnate the porous inert support with an impregnation solution, leach and separate the impregnated support, and then dry the resulting impregnated support.

[0049] d. The dried impregnated support is thermally activated to obtain a silver catalyst;

[0050] The addition of high-valence transition metal precursors ensures that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053, where M... Mo M W These represent the weight ratios of molybdenum to silver and tungsten to silver in the silver catalyst, respectively. F1 = M W +2.52M Mo .

[0051] According to the present invention, the silver-containing compound may be at least one selected from silver oxide, silver lactate, silver glycinate, silver propionate, silver acetate, silver formate, silver oxalate, silver acetylene, silver sulfate, and silver nitrate. The silver-containing compound used in step a may be the same as or different from the silver-containing compound used in step b.

[0052] According to the present invention, the high-valence transition metal precursor refers to the form in which molybdenum and / or tungsten exist before being prepared into the impregnation solution or catalyst, rather than the form in which they exist within the impregnation solution or catalyst. The high-valence transition metal precursor may be selected from at least one of molybdenum compounds and tungsten compounds.

[0053] According to the present invention, the molybdenum compound may be selected from at least one of molybdic acid, ammonium molybdate, lithium molybdate, sodium molybdate, potassium molybdate, cesium molybdate, molybdenum trioxide, phosphomolybdic acid and molybdic silicosmolybdic acid, preferably at least one of molybdic acid, phosphomolybdic acid, ammonium molybdate and molybdenum trioxide.

[0054] According to the present invention, the tungsten compound may be selected from at least one of tungstic acid, ammonium tungstate, lithium tungstate, sodium tungstate, potassium tungstate, cesium tungstate, tungsten trioxide, phosphotungstic acid, and silicotungstic acid, preferably at least one of phosphotungstic acid, tungstic acid, ammonium tungstate, and tungsten trioxide.

[0055] According to the present invention, in step a, the aqueous solution of the high-valence transition metal precursor may have a concentration of 0.001-0.1 g / mL, preferably 0.005-0.08 g / mL, and more preferably 0.01-0.05 g / mL based on the weight of tungsten or molybdenum. Based on the total weight of the aqueous solution of the high-valence transition metal precursor, the amount of silver-containing compound added may be 0.01-5 wt%, preferably 0.1-4 wt%, and more preferably 0.8-3 wt%. The pretreated high-valence transition metal precursor may have a concentration of 0.0005-0.2 g / mL, preferably 0.001-0.1 g / mL, and more preferably 0.005-0.05 g / mL based on the weight of tungsten or molybdenum.

[0056] According to the present invention, in step a, the heating temperature can be 40-250°C, for example 80-240°C or 100-220°C, for example 200°C; the duration can be 30 minutes to 72 hours, for example 5 hours to 36 hours, for example 48 hours; and the cooling temperature is 20-50°C, for example 20-40°C, for example room temperature. The pressure of the pretreatment of the high-valence transition metal precursor is not limited, and the pretreatment can be carried out in an open or closed container.

[0057] In an embodiment of the present invention, in step a, the pretreatment of the high-valence transition metal precursor may include adding one or more silver-containing compounds to an aqueous solution of the high-valence transition metal precursor, and heating the mixture of the aqueous solution of the high-valence transition metal precursor and the silver-containing compound to a temperature of 40-250°C, for example 200°C, for 30 minutes to 72 hours, for example 48 hours, and then cooling it to 20-50°C, for example, to room temperature.

[0058] In the preparation of the silver catalyst, the pretreatment process of the high-valence transition metal precursor enables the high-valence transition metals tungsten and molybdenum to achieve a tight bond with metallic silver. Due to the high-valence transition metal precursor pretreatment process of the present invention, the tungsten and / or molybdenum retention rates of the resulting catalyst after water dissolution treatment are each not less than 70%, preferably not less than 80%, more preferably not less than 85% (i.e., the water dissolution rates of tungsten and / or molybdenum are each not more than 30%, preferably not more than 20%, more preferably not more than 15%). The definitions of the tungsten and / or molybdenum retention rates of the catalyst after water dissolution treatment can be found in the first aspect of the present invention.

[0059] According to the present invention, step b can be carried out at a temperature of 0-50°C, for example 10-40°C, for example in an open or sealed container.

[0060] According to the present invention, in step b, the amount of silver-containing compound added can be 5-50 wt%, preferably 10-48 wt%, more preferably 15-45 wt%, and particularly preferably 20-40 wt%, based on the total weight of the impregnation liquid.

[0061] In an embodiment of the present invention, the amount of high-valence transition metal precursor added is such that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: M Mo For 0-0.0020, M W The range is 0-0.0050 for F1 and 0.0020-0.0050 for M; Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0062] In an embodiment of the present invention, the amount of high-valence transition metal precursor added is such that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: M Mo For 0-0.0019, M W The range is 0-0.0047, and F1 is 0.0022-0.0047; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0063] In an embodiment of the present invention, the amount of high-valence transition metal precursor added is such that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: MMo For 0-0.0018, M W The range is 0-0.0045, and F1 is 0.0026-0.0045; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0064] In an embodiment of the present invention, the amount of high-valence transition metal precursor added is such that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: M Mo For 0-0.0017, M W The range is 0-0.0042, and F1 is 0.0029-0.0042; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0065] In an embodiment of the present invention, the amount of high-valence transition metal precursor added is such that the weight ratio of molybdenum, tungsten, and silver in the silver catalyst satisfies the following relationship: M Mo For 0-0.0015, M W The range is 0-0.0039, and F1 is 0.0033-0.0039; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

[0066] According to the present invention, the organic amine compound can be any organic compound capable of forming a silver amine complex. Preferably, the organic amine compound can be at least one selected from methylamine, ethylamine, propylamine, butylamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, and ethanolamine, with ethylenediamine being the most preferred. Based on the total weight of the impregnation solution, the amount of the organic amine compound can be 7-35 wt%, preferably 14-33 wt%, more preferably 18-32 wt%, and particularly preferably 22-20 wt%.

[0067] According to the present invention, the co-compensator may include at least one of alkali metal co-compensator, alkaline earth metal co-compensator and rhenium co-compensator.

[0068] According to the present invention, the alkali metal co-agent can be a compound of at least one of lithium, sodium, potassium, rubidium and cesium, preferably a sulfate, nitrate, hydroxide or combination thereof of lithium, sodium, potassium, rubidium and cesium, more preferably cesium sulfate, cesium acetate, cesium nitrate or combination thereof.

[0069] According to the present invention, the alkaline earth metal co-agent can be a compound of at least one of magnesium, calcium, strontium and barium, preferably a sulfate, nitrate, carbonate, oxide, oxalate, acetate or a combination thereof of magnesium, calcium, strontium and barium, more preferably a compound of strontium and barium, and even more preferably barium acetate and / or strontium acetate.

[0070] According to the present invention, the rhenium co-agent may be rhenium oxide, perrhenic acid, perrhenate, or a combination thereof, preferably perrhenic acid and / or perrhenate.

[0071] According to the present invention, the amount of co-promoter added in the preparation of the silver catalyst can be the conventional amount used in the art. Preferably, the amount of alkali metal co-promoter is such that the alkali metal content in the silver catalyst is 1-2000 ppm, more preferably 4-1400 ppm; the amount of alkaline earth metal co-promoter is such that the alkaline earth metal content in the silver catalyst is 50-3000 ppm, more preferably 100-2500 ppm; and the amount of rhenium co-promoter is such that the rhenium metal content in the silver catalyst, on an atomic basis, is 1-2000 ppm, more preferably 50-1000 ppm.

[0072] According to the present invention, in step b, the water may include deionized water. The selection of the amount of water is well known in the art. Those skilled in the art can appropriately select the amount of water based on the desired silver content of the impregnation solution.

[0073] According to the present invention, the pretreated high-valence transition metal precursor obtained in step a is mixed with one or more silver-containing compounds, organic amine compounds, one or more co-auxiliaries, and water in the amounts described above to obtain a silver impregnation solution.

[0074] According to the present invention, suitable porous inert supports include alumina, silica, titanium dioxide, zirconium dioxide, other supports suitable for the purposes of the present invention, and combinations thereof, preferably including porous α-alumina supports, more preferably including those with a specific surface area of ​​0.2-2.0 m². 2 Porous α-alumina supports with a surface area of ​​0.35–0.85 mL / g and a pore volume of 0.35–0.85 mL / g. Specific surface area was determined according to the method described in standard ISO 9277. Pore volume was determined by mercury porosimetry.

[0075] According to the present invention, in step c, the impregnation solution obtained in step b is used to vacuum impregnate the porous inert support. The conditions for vacuum impregnation may include: a vacuum degree of less than 10 mmHg, for example less than 4 mmHg, less than 6 mmHg, or less than 8 mmHg; an impregnation temperature of 0 to 100°C, preferably 0 to 60°C; and an impregnation time of 10 to 60 minutes, for example 15 minutes, 30 minutes, and 45 minutes. The impregnated support obtained in step c can be dried at a temperature of 100-500°C, for example 200-400°C, for 1-10 minutes, for example 2-8 minutes, to obtain a dried impregnated support.

[0076] According to the present invention, in step d, the dried impregnated carrier obtained in step c is thermally activated. The activation atmosphere can be an oxygen-containing mixture, preferably a nitrogen-oxygen mixture with an oxygen content of not more than 21%, such as an air stream. The activation temperature can be 150-600°C, preferably 180-450°C. The activation time can be 1-120 minutes, preferably 1-80 minutes, more preferably 2-40 minutes.

[0077] In an embodiment of the present invention, the dried impregnated carrier may be heat-treated in an activating atmosphere such as an oxygen-containing mixture at 150-600°C, preferably 180-450°C, for 1-120 minutes, preferably 2-40 minutes.

[0078] A third aspect of the present invention provides a silver catalyst prepared by the preparation method described herein.

[0079] A fourth aspect of the present invention provides a method for producing ethylene oxide by epoxidation of ethylene, comprising oxidizing ethylene with oxygen in the presence of the silver catalyst described in the present invention and / or the silver catalyst prepared by the preparation method described in the present invention.

[0080] According to the present invention, the method for producing ethylene oxide by ethylene epoxidation can be carried out under conventional reaction conditions known to those skilled in the art. For example, the reaction temperature can be 150-350°C, preferably 180-300°C, the reaction pressure can be 0.2-4 MPa, preferably 0.5-3 MPa, and the space velocity (space velocity) can be 1000-30000 h⁻¹. -1 The preferred range is 3000-10000h. -1 .

[0081] In the method for producing ethylene oxide by ethylene epoxidation, the reaction gas may contain 10-80 mol%, preferably 20-60 mol%, more preferably 25-50 mol% of ethylene, and 3-10 mol%, preferably 4-9 mol%, more preferably 5-8 mol% of oxygen, based on the total molar amount of the reaction gas.

[0082] Inert gases such as nitrogen and argon, lower hydrocarbons such as methane and ethane, or reaction modifiers such as halogenated hydrocarbons such as ethyl chloride, vinyl chloride, or dichloroethane may be additionally mixed into the reaction gas containing ethylene and oxygen. The reaction gas may contain 0-15 mol ppm, preferably 0.1-8 mol ppm, of chlorine-containing reaction modifier. In addition, the reaction gas may contain 0-30 mol%, preferably 0.1-20 mol%, of other substances, such as vapor, carbon dioxide, or rare gases. The remainder of the reaction gas typically consists of lower hydrocarbons such as methane and inert gases such as nitrogen.

[0083] The fifth aspect of the invention provides the use of the silver catalyst described in the invention and / or the silver catalyst prepared by the preparation method described in the invention in a method for producing ethylene oxide by epoxidation of ethylene.

[0084] A sixth aspect of the invention provides a silver impregnation solution containing water, a silver-containing compound, an organic amine compound, a high-valence transition metal precursor, and a co-agent, wherein the high-valence transition metal precursor may or may not be pretreated. In embodiments of the invention, a silver impregnation solution containing water, a silver-containing compound, an organic amine compound, a pretreated high-valence transition metal precursor, and a co-agent is provided, such as the silver impregnation solution obtained in step b of the silver catalyst preparation method according to the invention. The use of the silver impregnation solution of the invention in a method for producing ethylene oxide through ethylene epoxidation is also provided.

[0085] The definitions of terms given in the first aspect of the invention also apply to the second, third, fourth, fifth, and sixth aspects. The definitions of terms given in the second aspect of the invention also apply to the first, third, fourth, fifth, and sixth aspects. The description of the method for producing ethylene oxide by epoxidation of ethylene in the fourth aspect of the invention also applies to the fifth and sixth aspects.

[0086] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0087] Example

[0088] 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.

[0089] Methods for determining the tungsten and molybdenum content in catalysts

[0090] The catalyst was digested with 68% nitric acid, and the resulting digest was analyzed for tungsten and molybdenum using ICP-OES (inductively coupled plasma optical emission spectrometry). The tungsten and molybdenum content was quantified by external standard method (relative to the weight of the catalyst).

[0091] Methods for determining the silver content in catalysts

[0092] The silver content in the catalyst (relative to the weight of the catalyst) was determined by potassium thiocyanate titration.

[0093] F1 Calculation Method

[0094] F1 = M W +2.52M M M Mo M W These represent the weight ratios of molybdenum to silver and tungsten to silver in the silver catalyst, respectively. o

[0095] Pretreatment of high-priced transition metal precursors

[0096] Measure 50 mL of 0.020 g / mL (based on the elemental weight of tungsten / molybdenum) ammonium tungstate or ammonium molybdate aqueous solution, add 1.69 g of silver glycinate solid, heat the resulting mixture in a container at 200 °C for 48 hours, cool to room temperature, and dilute with deionized water to 100 mL to obtain a pretreated ammonium tungstate or ammonium molybdate aqueous solution (0.010 g / mL, based on the elemental weight of tungsten / molybdenum), which will be used in the preparation of the silver catalysts in the comparative examples and embodiments described below.

[0097] In all comparative examples and embodiments below, the carrier used has a specific surface area of ​​1.2 m². 2 / g, pore volume 0.68mL 3 / g porous α-alumina support.

[0098] Comparative Example 1

[0099] At room temperature, add 35 g of ethylenediamine and 90 g of deionized water to a stirred glass beaker to obtain a homogeneous mixture. Add 70 g of anhydrous silver oxalate at 10 °C and stir to dissolve to obtain a homogeneous mixture. Then add 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium) and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium), and mix thoroughly to obtain an impregnation solution for later use.

[0100] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 25.07wt% silver, with no tungsten or molybdenum elements, and an F1 content of 0.

[0101] Comparative Example 2

[0102] At room temperature, 35 g of ethylenediamine and 87 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 3.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain an impregnation solution for later use.

[0103] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 25.03wt% silver, and the calculated weight ratio of tungsten to silver was 0.0006, with F1 being 0.0006.

[0104] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 151ppm, and the tungsten content after water leaching was 137ppm, resulting in a tungsten retention rate of 91%.

[0105] Comparative Example 3

[0106] At room temperature, 35 g of ethylenediamine and 89 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 1.0 mL of pretreated ammonium molybdate aqueous solution (0.010 g / mL, based on molybdenum element weight), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on cesium element weight), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on rhenium element weight) were added and mixed thoroughly to obtain an impregnation solution for later use.

[0107] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 24.99wt% silver, and the calculated weight ratio of molybdenum to silver was 0.0002, with an F1 value of 0.000504.

[0108] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The molybdenum content was determined by ICP-OES for both the pre- and post-water leaching samples. The molybdenum content before water leaching was 50ppm, and the molybdenum content after water leaching was 45ppm, resulting in a molybdenum retention rate of 90%.

[0109] Comparative Example 4

[0110] At room temperature, 35 g of ethylenediamine and 60 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 30.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain an impregnation solution for later use.

[0111] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 25.12wt% silver, and the calculated weight ratio of tungsten to silver was 0.0060, with F1 being 0.0060.

[0112] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 1513ppm, and the tungsten content after water leaching was 1331ppm, resulting in a tungsten retention rate of 88%.

[0113] Comparative Example 5

[0114] At room temperature, 35 g of ethylenediamine and 82 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 8.0 mL of untreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added separately and mixed thoroughly to obtain an impregnation solution for later use.

[0115] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 25.11 wt% silver, and the calculated weight ratio of tungsten to silver was 0.0016, with F1 being 0.0016.

[0116] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for samples before and after water leaching treatment. The tungsten content before treatment was 404ppm, and the tungsten content after treatment was 223ppm, resulting in a tungsten retention rate of 55%.

[0117] Example 1

[0118] At room temperature, 35 g of ethylenediamine and 70 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. At 10 °C, 70 g of anhydrous silver oxalate was added and stirred until dissolved to obtain a homogeneous mixture. Then, 20.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0119] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 25.05wt% silver, and the calculated weight ratio of tungsten to silver was 0.0040, with F1 being 0.0040.

[0120] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 994ppm, and the tungsten content after water leaching was 885ppm, resulting in a tungsten retention rate of 89%.

[0121] Example 2

[0122] At room temperature, 35 g of ethylenediamine and 84 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 8.0 mL of pretreated ammonium molybdate aqueous solution (0.010 g / mL, based on molybdenum element weight), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on cesium element weight), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on rhenium element weight) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0123] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 25.05wt% silver, and the calculated weight ratio of molybdenum to silver was 0.0016, with an F1 value of 0.00403.

[0124] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The molybdenum content was determined by ICP-OES for both the pre- and post-water leaching samples. The molybdenum content before water leaching was 401ppm, and the molybdenum content after water leaching was 349ppm, resulting in a molybdenum retention rate of 87%.

[0125] Example 3

[0126] At room temperature, 35 g of ethylenediamine and 82 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 8.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0127] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 24.95wt% silver, and the calculated weight ratio of tungsten to silver was 0.0016, with F1 being 0.0016.

[0128] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 399ppm, and the tungsten content after water leaching was 351ppm, resulting in a tungsten retention rate of 88%.

[0129] Example 4

[0130] At room temperature, 35 g of ethylenediamine and 84 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 6.0 mL of pretreated ammonium molybdate aqueous solution (0.010 g / mL, based on molybdenum element weight), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on cesium element weight), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on rhenium element weight) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0131] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 25.03wt% silver, and the calculated weight ratio of molybdenum to silver was 0.0012, with an F1 value of 0.004032.

[0132] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The molybdenum content was determined by ICP-OES for both the pre- and post-water leaching samples. The molybdenum content before water leaching was 297ppm, and the molybdenum content after water leaching was 267ppm, resulting in a molybdenum retention rate of 90%.

[0133] Example 5

[0134] At room temperature, 35 g of ethylenediamine and 72 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 18.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0135] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 25.07wt% silver, and the calculated weight ratio of tungsten to silver was 0.0036, with F1 also being 0.0036.

[0136] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for samples before and after water leaching treatment. The tungsten content before treatment was 898ppm, and the tungsten content after treatment was 782ppm, resulting in a tungsten retention rate of 87%.

[0137] Example 6

[0138] At room temperature, 35 g of ethylenediamine and 83 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 7.0 mL of pretreated ammonium molybdate aqueous solution (0.010 g / mL, based on molybdenum element weight), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on cesium element weight), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on rhenium element weight) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0139] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, followed by cooling to obtain the finished silver catalyst. The finished silver catalyst contained 24.93 wt% silver, and the calculated weight ratio of molybdenum to silver was 0.0014, with an F1 value of 0.003528.

[0140] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The molybdenum content was determined by ICP-OES for both the pre- and post-water leaching samples. The molybdenum content before water leaching was 350ppm, and the molybdenum content after water leaching was 318ppm, resulting in a molybdenum retention rate of 91%.

[0141] Example 7

[0142] At room temperature, 35 g of ethylenediamine and 77 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 10.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 3.0 mL of pretreated ammonium molybdate aqueous solution (0.010 g / mL, based on the weight of molybdenum), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain an impregnation solution for later use.

[0143] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes, and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 25.02wt% silver, the calculated weight ratio of tungsten to silver was 0.0020, the calculated weight ratio of molybdenum to silver was 0.0006, and F1 was 0.003512.

[0144] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten and molybdenum contents were determined by ICP-OES for samples before and after water leaching treatment. The tungsten content before treatment was 507ppm, and the tungsten content after treatment was 451ppm, resulting in a tungsten retention rate of 89%. The molybdenum content before treatment was 145ppm, and the molybdenum content after treatment was 126ppm, resulting in a molybdenum retention rate of 87%.

[0145] Example 8

[0146] At room temperature, 35 g of ethylenediamine and 150 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 18.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain the impregnation solution, which was then set aside for use.

[0147] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 18.15wt% silver, and the calculated weight ratio of tungsten to silver was 0.0036, with F1 being 0.0036.

[0148] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 644ppm, and the tungsten content after water leaching was 548ppm, resulting in a tungsten retention rate of 85%.

[0149] Example 9

[0150] At room temperature, 35 g of ethylenediamine and 29 g of deionized water were added to a stirred glass beaker to obtain a homogeneous mixture. 70 g of anhydrous silver oxalate was added at 10 °C and stirred until dissolved to obtain a homogeneous mixture. Then, 18.0 mL of pretreated ammonium tungstate aqueous solution (0.010 g / mL, based on the weight of tungsten), 2.5 mL of cesium nitrate aqueous solution (0.040 g / mL, based on the weight of cesium), and 2.5 mL of ammonium perrhenate aqueous solution (0.060 g / mL, based on the weight of rhenium) were added and mixed thoroughly to obtain an impregnation solution for later use.

[0151] 15g of porous α-alumina support was immersed in an impregnation solution at 35℃ for 30 minutes under a pressure of 6 mmHg. After being removed and drained at 250℃ for 5 minutes, the support was heat-treated in an air stream at 300℃ for 3 minutes and then cooled to obtain the finished silver catalyst. The finished silver catalyst contained 32.25wt% silver, and the calculated weight ratio of tungsten to silver was 0.0036, with F1 also being 0.0036.

[0152] The obtained silver catalyst was subjected to a water leaching treatment experiment. 10g of the catalyst sample was completely immersed in 30mL of deionized water and maintained at 80℃ for 30 minutes. The sample was then removed, dried at 100℃, and ground into powder. The tungsten content was determined by ICP-OES for both the pre- and post-water leaching samples. The tungsten content before water leaching was 1159ppm, and the tungsten content after water leaching was 1066ppm, resulting in a tungsten retention rate of 92%.

[0153] Catalyst performance testing

[0154] The activity and selectivity of various silver catalysts obtained from the comparative examples and embodiments above 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, placed within a heating mantle. The catalyst loading volume was 1 mL, and the lower part of the reaction tube contained ceramic inert packing material. The catalyst bed was located in the isothermal region of the heating mantle.

[0155] The reaction test conditions for the epoxidation of ethylene to produce ethylene oxide used in the experiment are shown in Table 1.

[0156] Table 1: Reaction test conditions for catalysts

[0157] Once the above conditions are met and the reactor stabilizes, the composition of the gas at the reactor inlet and outlet is simultaneously measured. Based on the measurement results, a volume shrinkage correction is performed, and then the catalyst selectivity is calculated using the following formula:

[0158] Selective Where ΔEO is the concentration difference of ethylene oxide in the reactor outlet gas and the reactor inlet gas, and ΔCO2 is the concentration difference of carbon dioxide in the reactor outlet gas and the reactor inlet gas.

[0159] The performance of the silver catalysts obtained in each comparative example and embodiment was determined using a microreactor evaluation device under the test conditions in Table 1 above. The data results 48 hours after the start of the reaction are shown in Table 2.

[0160] Table 2: Performance test results of the catalyst

[0161] As can be seen from Table 2, compared with Comparative Example 1, which did not contain high-valence transition metals molybdenum and tungsten, and Comparative Example 2 and Comparative Example 3, which contained amounts of tungsten and molybdenum that were below the range required by the present invention, the catalyst according to the present invention has a significant advantage in selectivity in the first 48 hours of the reaction.

[0162] Compared with Comparative Example 4, where the amount of high-valence transition metal tungsten added exceeded the range required by this invention, the catalyst according to this invention has a greater advantage in selectivity during the first 48 hours of the reaction, and also has advantages in reaction activity at a lower reaction temperature.

[0163] Compared with Comparative Example 5, which incorporates an untreated high-valence transition metal tungsten precursor, the catalyst according to the invention, which has undergone a pretreatment process, exhibits a greater advantage in selectivity during the first 48 hours of the reaction.

[0164] Figure 1 shows a comparison of the selectivity trends of the catalysts in Example 5 and Comparative Example 2 during the first 48 hours of the reaction. As can be seen from Figure 1, compared with Comparative Example 2, where the amount added was outside the range required by this invention, the silver catalyst in Example 5 can achieve a selectivity of over 90% very quickly.

[0165] Figure 2 shows a comparison of the selectivity trends of the catalysts in Example 3 and Comparative Example 5 during the first 48 hours of the reaction. The only difference between Example 3 and Comparative Example 5 is whether or not the high-valence transition metal tungsten precursor was pretreated. As can be seen from Figure 2, compared with Comparative Example 5, which did not pretreat the high-valence transition metal tungsten precursor, the silver catalyst in Example 3, which pretreated the high-valence transition metal tungsten precursor, could reach a selectivity of nearly 90% very quickly. Therefore, in the preparation of silver catalysts, the pretreatment of the high-valence transition metal precursor can enable the silver catalyst to reach its optimal performance more quickly.

[0166] 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.

[0167] 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 silver catalyst for the epoxidation of ethylene to produce ethylene oxide, characterized in that, The silver catalyst contains a porous inert support, metallic silver, high-valence transition metal elements, and co-catalyst elements; Wherein, based on the total weight of the silver catalyst, the silver content, calculated as silver element, is 10-40 wt%, and the high-valence transition metal element is molybdenum and / or tungsten. The content of the high-valence transition metal element in the catalyst is such that the weight ratio of molybdenum, tungsten, and silver satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo ; Wherein, after water leaching treatment, the silver catalyst retains tungsten and / or molybdenum elements at a rate of not less than 70%, preferably not less than 80%, and more preferably not less than 85%.

2. The silver catalyst for the epoxidation of ethylene to ethylene oxide according to claim 1, wherein, The weight ratios of molybdenum, tungsten, and silver in the catalyst satisfy the following relationship: M Mo For 0-0.0019, M W The range is 0-0.0047, and F1 is 0.0022-0.0047; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo ; Preferably; M Mo For 0-0.0017, M W The range is 0-0.0042, and F1 is 0.0029-0.0042; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo ; More preferably; M Mo For 0-0.0015, M W The range is 0-0.0039, and F1 is 0.0033-0.0039; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo。 3. The silver catalyst for the epoxidation of ethylene to ethylene oxide according to claim 1 or 2, wherein, The co-agent element includes at least one of alkali metal elements, alkaline earth metal elements, and rhenium, wherein the alkali metal element is at least one of lithium, sodium, potassium, rubidium, and cesium, preferably at least one of potassium and cesium; and the alkaline earth metal element is at least one of magnesium, calcium, strontium, and barium, preferably at least one of barium and strontium.

4. The silver catalyst for the epoxidation of ethylene to ethylene oxide according to claim 3, wherein, Based on the total weight of the silver catalyst, the content of the alkali metal element is 1-2000 ppm, preferably 4-1400 ppm; the content of the alkaline earth metal element is 50-3000 ppm, preferably 100-2500 ppm; and the content of the rhenium element is 1-2000 ppm, preferably 50-1000 ppm.

5. The silver catalyst for the epoxidation of ethylene to ethylene oxide according to any one of claims 1-4, wherein, Based on the total weight of the silver catalyst, the silver content, calculated as elemental silver, is 14-38 wt%, preferably 20-36 wt%, and more preferably 25-32 wt%.

6. A method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide, characterized in that, Includes the following steps: a. The high-valence transition metal precursor is pretreated by adding one or more silver-containing compounds to an aqueous solution of the high-valence transition metal precursor and heating it for a period of time followed by cooling. b. Prepare an impregnation solution by mixing a pretreated high-valence transition metal precursor with one or more silver-containing compounds, organic amine compounds, one or more co-auxiliaries, and water. c. Vacuum impregnate the porous inert carrier with the impregnation solution, and after leaching and separation, dry the resulting impregnated carrier; d. The dried impregnated support is thermally activated to obtain the silver catalyst; The amount of the high-valence transition metal precursor added ensures that the weight ratio of molybdenum, tungsten, and silver in the catalyst satisfies the following relationship: M Mo For 0-0.0021, M W The range is 0-0.0053, and F1 is 0.0015-0.0053, where M... Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

7. The method for preparing the silver catalyst for the epoxidation of ethylene to ethylene oxide according to claim 6, wherein, The silver-containing compound is at least one of silver oxide, silver lactate, silver glycinate, silver propionate, silver acetate, silver formate, silver oxalate, silver acetylene, silver sulfate, and silver nitrate. Preferably, in step a, the amount of silver-containing compound added is 0.01-5 wt%, preferably 0.1-4 wt%, based on the total weight of the aqueous solution of the high-valence transition metal precursor; in step b, the amount of silver-containing compound added is 5-50 wt%, preferably 10-48 wt%, based on the total weight of the impregnation solution.

8. The method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide according to claim 6 or 7, wherein, The high-valence transition metal precursor is selected from at least one of molybdenum compounds and tungsten compounds, wherein the molybdenum compound is selected from at least one of molybdic acid, ammonium molybdate, lithium molybdate, sodium molybdate, potassium molybdate, cesium molybdate, molybdenum trioxide, phosphomolybdic acid, and molybdic silicospore acid, preferably at least one of molybdic acid, phosphomolybdic acid, ammonium molybdate, and molybdenum trioxide; and the tungsten compound is selected from at least one of tungstic acid, ammonium tungstate, lithium tungstate, sodium tungstate, potassium tungstate, cesium tungstate, tungsten trioxide, phosphomolybdic acid, and molybdic silicospore acid, preferably at least one of phosphomolybdic acid, lithium tungstate, tungstic acid, ammonium tungstate, and tungsten trioxide.

9. The method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide according to any one of claims 6-8, wherein, The amount of the high-valence transition metal precursor added ensures that the weight ratio of molybdenum, tungsten, and silver in the catalyst satisfies the following relationship: M Mo For 0-0.0019, M W The range is 0-0.0047, and F1 is 0.0022-0.0047; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo ; Preferably, M Mo For 0-0.0017, M W The range is 0-0.0042, and F1 is 0.0029-0.0042, where M... Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo ; More preferably; M Mo For 0-0.0015, M W The range is 0-0.0039, and F1 is 0.0033-0.0039; where M Mo M W These are the weight ratios of molybdenum to silver and tungsten to silver in the catalyst, respectively, where F1 = M. W +2.52M Mo .

10. The method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide according to any one of claims 6-9, wherein, The organic amine compound is at least one selected from methylamine, ethylamine, propylamine, butylamine, ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, and ethanolamine; preferably, the amount of the organic amine compound is 7-35 wt%, more preferably 14-33 wt%, based on the total weight of the silver impregnation solution.

11. The method for preparing a silver catalyst for the epoxidation of ethylene to ethylene oxide according to any one of claims 6-10, wherein, The co-compensator includes at least one of alkali metal co-compensator, alkaline earth metal co-compensator, and rhenium co-compensator; Preferably, The alkali metal co-compensator is a compound of at least one of lithium, sodium, potassium, rubidium, and cesium, preferably a sulfate, nitrate, hydroxide, or combination thereof of lithium, sodium, potassium, rubidium, and cesium; the alkaline earth metal co-compensator is a compound of at least one of magnesium, calcium, strontium, and barium, preferably a sulfate, nitrate, carbonate, oxide, oxalate, acetate, or combination thereof of magnesium, calcium, strontium, and barium; the rhenium co-compensator is rhenium oxide, perrhenic acid, perrhenate, or a combination thereof, preferably perrhenic acid and / or perrhenate.

12. The preparation method according to any one of claims 6-11, wherein, In step a, the heating temperature is 40℃-250℃, the duration is 30 minutes-72 hours, and the cooling temperature is 20-50℃; Step b is performed at a temperature of 0-50℃; The conditions for vacuum impregnation in step c include: vacuum degree less than 10 mmHg, impregnation temperature of 0 to 100°C, and impregnation time of 10 to 60 minutes.

13. The preparation method according to any one of claims 6-12, wherein, In step d, the activation atmosphere is an oxygen-containing mixture, preferably a nitrogen-oxygen mixture with an oxygen content of no more than 21%; the activation temperature is 150-600℃, preferably 180-450℃; and the activation time is 1-120 minutes, preferably 2-40 minutes.

14. The preparation method according to any one of claims 6-13, wherein, The porous inert support includes alumina, silica, titanium dioxide, zirconium dioxide, and combinations thereof, preferably porous α-alumina support, and more preferably support with a specific surface area of ​​0.2-2.0 m². 2 α-Alumina support with a pore volume of 0.35-0.85 mL / g and a pore volume of 0.35-0.85 mL / g.

15. The silver catalyst prepared by any one of claims 6-14.

16. A method for producing ethylene oxide by epoxidation of ethylene, comprising oxidizing ethylene with oxygen in the presence of a silver catalyst according to any one of claims 1-5 and / or a silver catalyst according to claim 15.

17. Use of the silver catalyst according to any one of claims 1-5 and / or the silver catalyst according to claim 15 in a method for producing ethylene oxide by ethylene epoxidation.

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