An α-alumina support and its preparation method, a silver catalyst, a method for producing epoxides from olefins, and their applications.

Abstract

The application belongs to the technical field of catalysts, and discloses an alpha-alumina carrier and a preparation method thereof, a silver catalyst, a method for producing an epoxide compound by olefin epoxidation, and application, the alpha-alumina carrier is prepared by a method comprising the following steps: (1) uniformly mixing an organic oily liquid, aluminum hydroxide, optionally, alumina, optionally, a silicon-containing compound, optionally, an alkaline earth metal compound, and optionally, a mineralizer to obtain a solid mixture; (2) kneading, molding, drying, and calcining the solid mixture with an acid solution to obtain the alpha-alumina carrier; wherein the kinematic viscosity of the organic oily liquid is greater than or equal to 10 mm 2 / s, preferably greater than or equal to 20 mm 2 / s. By selecting an organic oily liquid with different kinematic viscosities, the present application can optimize the permeability of the pore channels of the alpha-alumina carrier and improve the performance of the silver catalyst prepared therefrom.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to an α-alumina support and its preparation method, a silver catalyst, a method for producing epoxides from olefins, and their applications. Background Technology

[0002] Alumina, as a commonly used catalyst support, has attracted widespread attention and in-depth research due to its large specific surface area, good thermal stability, high mechanical strength, and excellent texture. It is a widely used and mature catalyst support. Alumina exists in various crystalline phases, among which γ, δ, κ, η, θ, and α are common. Of these, the α phase is stable, while the others are metastable. In current industrial applications, the technique of preparing α-alumina supports by calcining aluminum hydroxide precursors is quite prevalent. During precursor calcination, the resulting amorphous alumina transforms into metastable alumina phases; this process is an amorphous reforming process. After further calcination at sufficiently high temperatures, these metastable alumina phases can all be transformed into α-alumina. Among alumina with different crystalline forms, γ-alumina and α-alumina are the most common catalyst supports.

[0003] Currently, α-alumina support is the only effective support for silver catalysts used in olefin epoxidation reactions. In existing technologies, silver catalysts, in addition to silver, typically contain one or more other elements co-deposited on the support. These other elements act as promoters or co-promoters to improve the catalytic performance of the silver catalyst. The support is usually composed of α-alumina with a suitable pore structure. An α-alumina support with a suitable pore structure not only promotes the deposition of the active component on the support but also improves the catalytic performance of the silver catalyst. This is because a suitable pore structure provides sufficient space for the olefin epoxidation reaction, allowing the heat of reaction to dissipate promptly. Furthermore, it facilitates the timely desorption of the target product, the epoxide. Parameters for evaluating the pore structure of α-alumina supports include pore volume, pore size, and pore size distribution.

[0004] Materials used to prepare α-alumina supports for silver catalysts generally include: alumina and / or aluminum hydroxide, binders, additives, solid pore-forming agents, and lubricants. Alumina and aluminum hydroxide provide the aluminum source, binders bind the different components together for easy molding, and additives improve the performance of the support. Solid pore-forming agents decompose and leave during calcination, resulting in a suitable pore distribution on the final support. Currently, solid pore-forming agents include carbon-containing materials, powdered plastics, cellulose, sawdust, and other plant materials. However, these pore-forming agents often introduce impurities, which are detrimental to the performance of the silver catalyst. Lubricants reduce friction and facilitate support molding. Summary of the Invention

[0005] The purpose of this invention is to address the limitations of the existing technology. Through extensive and in-depth research in the field of α-alumina support and silver catalyst preparation, the inventors have broken through conventional methods for α-alumina support preparation and pore structure characterization. They have selected an organic oily liquid, aluminum hydroxide, optionally alumina, optionally a silicon-containing compound, optionally an alkaline earth metal compound, and optionally a mineralizing agent to prepare the α-alumina support. The organic oily liquid can reduce friction between material particles and between the material and equipment, increasing its fluidity, facilitating support formation, and extending the service life of mechanical equipment. Furthermore, it has been found that the α-alumina support prepared by this invention not only possesses a suitable pore structure but also has highly permeable micropores with low tortuosity. This is beneficial for improving the uniformity of the active component silver and additives on the support surface and interior, and also facilitates the full diffusion of reactant molecules into the catalyst interior and the timely desorption of product molecules during the catalytic reaction, thereby improving the catalytic performance of the catalyst.

[0006] A first aspect of the present invention provides an α-alumina support, which is prepared by a method comprising the following steps:

[0007] (1) Mix organic oily liquid, aluminum hydroxide, optional aluminum oxide, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer evenly to obtain a solid mixture;

[0008] (2) The solid mixture is kneaded, shaped, dried and calcined with an acid solution to obtain the α-alumina carrier;

[0009] Wherein, the kinematic viscosity of the organic oily liquid is ≥10 mm. 2 / s, preferably ≥20mm 2 / s.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned α-alumina support, the method comprising:

[0011] (1) The organic oily liquid, aluminum hydroxide, optional aluminum oxide, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer are mixed evenly to obtain the solid mixture;

[0012] (2) The solid mixture is kneaded, shaped, dried and calcined with the acid solution to obtain the α-alumina carrier.

[0013] A third aspect of the present invention provides a silver catalyst prepared by a method comprising the following steps: first, impregnating the above-mentioned alumina support with a solution comprising an organic amine, a silver-containing compound, an alkali metal promoter, an alkaline earth metal promoter, an optional rhenium promoter, and an optional rhenium promoter, and then leaching the impregnation solution; and then activating the leached support to obtain the silver catalyst.

[0014] A fourth aspect of the present invention provides a method for producing an epoxide compound by epoxidation of an olefin, the method comprising: epoxidizing an olefin in the presence of the above-mentioned silver catalyst to obtain the epoxide compound;

[0015] The olefin is preferably selected from at least one of styrene, propylene, ethylene and 1,3-butadiene.

[0016] The fifth aspect of the invention provides the use of the epoxy compound obtained by the above method as a raw material for the production of at least one of ethylene glycol, ethylene glycol ether, and ethanolamine.

[0017] The technical solution of the present invention has the following beneficial effects:

[0018] (1) The α-alumina carrier provided by the present invention can be prepared by adding an organic oily liquid with suitable kinematic viscosity during the preparation process, without adding other pore-forming agents and lubricants.

[0019] (2) By selecting organic oily liquids with different kinematic viscosities, the present invention can optimize the permeability of the pores of the α-alumina support and improve the performance of the silver catalyst prepared therefrom.

[0020] (3) The preparation method of the α-alumina carrier of the present invention is simple and does not introduce impurity elements, so it is more economical and environmentally friendly, and meets the requirements of industry development.

[0021] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0022] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0023] A first aspect of the present invention provides an α-alumina support, which is prepared by a method comprising the following steps:

[0024] (1) Mix organic oily liquid, aluminum hydroxide, optional aluminum oxide, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer evenly to obtain a solid mixture;

[0025] (2) The solid mixture is kneaded, shaped, dried and calcined with an acid solution to obtain the α-alumina carrier;

[0026] Wherein, the kinematic viscosity of the organic oily liquid is ≥10 mm. 2 / s, preferably ≥20mm 2 / s.

[0027] According to the present invention, preferably, the organic oily liquid includes alkanes and / or aromatic hydrocarbons, preferably at least one of n-alkanes, cycloalkanes and aromatic hydrocarbons, and more preferably at least one of white oil, paraffin oil, rubber oil and naphtha;

[0028] The white oil is preferably at least one of medical-grade white oil, food-grade white oil, cosmetic-grade white oil, and industrial-grade white oil.

[0029] According to the present invention, preferably, the aluminum hydroxide comprises aluminum oxide monohydrate and optionally aluminum oxide trihydrate;

[0030] The monohydrate alumina is at least one of boehmite monohydrate, diaspore monohydrate, and pseudo-monohydrate alumina.

[0031] The alumina trihydrate is at least one of gibbsite, gibbsite trihydrate, and diaspore.

[0032] The aluminum hydroxide of the present invention will be transformed into intermediate transition state aluminum oxide by high-temperature calcination, and finally transformed into α-alumina.

[0033] According to the present invention, in addition to aluminum hydroxide providing the aluminum source, aluminum oxide may also be selected. Preferably, the aluminum oxide includes at least one of γ-aluminum oxide, θ-aluminum oxide, κ-aluminum oxide, η-aluminum oxide and α-aluminum oxide.

[0034] To improve the performance of the α-alumina support, the present invention may optionally add a silicon-containing compound as an additive; the silicon-containing compound includes at least one of silicon-containing elemental sol, silicon dioxide, silicic acid, organosilicon and silicate.

[0035] The alkaline earth metal compound is selected from at least one of the following alkaline earth metal oxides, hydroxides, nitrates, acetates, oxalates, and sulfates; the alkaline earth metal is at least one of magnesium, calcium, strontium, and barium.

[0036] The mineralizing agent is selected from at least one of ammonium fluoride, magnesium fluoride, aluminum fluoride, lithium fluoride, boric acid, zinc fluoride, ammonium chloride, and ammonium nitrate.

[0037] In this invention, the performance of the α-alumina support is improved by adding a mineralizing agent to change the alumina crystallization process.

[0038] According to the present invention, preferably, based on the total weight of the solid mixture, the amount of the organic oily liquid is 1.0–30.0 wt%, the amount of the gibbsite is 15.0–99.0 wt%, the amount of the trihydrate gibbsite is 0–80.0 wt%, the amount of the alumina is 0–60.0 wt%, the amount of the silicon-containing compound is 0–10.0 wt%, the amount of the alkaline earth metal compound is 0–5.0 wt%, and the amount of the mineralizer is 0–10.0 wt%.

[0039] According to the present invention, preferably, the acid solution includes at least one selected from the following: citric acid aqueous solution, nitric acid aqueous solution, formic acid aqueous solution, oxalic acid aqueous solution, acetic acid aqueous solution, propionic acid aqueous solution, and hydrochloric acid aqueous solution.

[0040] In this invention, the added acid solution can react with some of the aluminum hydroxide to form an aluminum sol, which binds the components together to form an extrudable paste. The amount of acid solution used and the acid content therein are limited to meet the requirements of the mixed raw materials to form an extrudable paste; preferably, the mass ratio of acid to water in the acid solution is 1:0.2 to 10.

[0041] In this invention, preferably, the components in the solid mixture are not mixed with the acid solution in a specific order. For example, the mineralizer in the solid mixture can be dispersed or dissolved in the acid solution and then added to the solid mixture together.

[0042] To ensure the mixture is thoroughly mixed, this invention involves kneading the mixture. Kneading and mixing can be performed independently or continuously. This invention does not have a particular limitation on the timing of adding the acid solution during the kneading process; as long as the acid solution is added during kneading and then kneaded to the desired consistency, it is acceptable.

[0043] In this invention, preferably, the molding method may include extrusion molding, horizontal molding, sheet molding or roll cutting molding, and the carrier molding shape may include spherical, cylindrical, annular, foliage-shaped, porous cylindrical, pellet-shaped, block-shaped or other shapes.

[0044] After molding, the carrier undergoes a drying process. According to the present invention, preferably, the drying temperature is 60-120°C.

[0045] In order to obtain an α-alumina carrier with suitable properties, the present invention calcines the dried molded article; the calcination temperature is 1000-1600℃ and the calcination time is 1-70h.

[0046] In this invention, preferably, the roasting apparatus includes a muffle furnace, a tunnel kiln, a microwave roasting apparatus, a roller kiln, or a bell kiln.

[0047] In this invention, aluminum hydroxide and / or aluminum oxide are essentially converted into α-alumina after high-temperature calcination, and the mass content of α-alumina in the α-alumina carrier of this invention is ≥95%.

[0048] According to the present invention, preferably, the α-alumina support has at least one of the following characteristics: porosity ≥45%, preferably ≥60%; tortuosity ≤40, preferably ≤23.

[0049] A second aspect of the present invention provides a method for preparing the above-mentioned α-alumina support, the method comprising:

[0050] (1) The organic oily liquid, aluminum hydroxide, optional aluminum oxide, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer are mixed evenly to obtain the solid mixture;

[0051] (2) The solid mixture is kneaded, shaped, dried and calcined with the acid solution to obtain the α-alumina carrier.

[0052] A third aspect of the present invention provides a silver catalyst prepared by a method comprising the following steps: first, impregnating the above-mentioned alumina support with a solution comprising an organic amine, a silver-containing compound, an alkali metal promoter, an alkaline earth metal promoter, an optional rhenium promoter, and an optional rhenium promoter, and then leaching the impregnation solution; and then activating the leached support to obtain the silver catalyst.

[0053] After preparing the α-alumina support of the present invention, those skilled in the art can prepare the silver catalyst of the present invention by known methods or any conventional method. For example, the above-mentioned α-alumina support is usually impregnated with a solution containing sufficient amounts of organic amine, silver-containing compound, alkali metal promoter, alkaline earth metal promoter, optional rhenium promoter, and optional rhenium promoter co-promoter.

[0054] In this invention, preferably, the carrier obtained by leaching is activated in a gaseous atmosphere containing oxygen.

[0055] In this invention, the organic amine is added to enable the formation of a silver amine complex with the silver compound. The organic amine includes one or more of pyridine, ethylamine, n-propylamine, n-butylamine, isobutylamine, tert-butylamine, sec-butylamine, 1,2-propanediamine, 1,3-propanediamine, ethylenediamine, 1,2-butanediamine, 1,3-butanediamine, ethanolamine, propanolamine, and butanolamine.

[0056] In this invention, during the preparation of the silver catalyst, the silver-containing compound includes one or more of silver oxide, silver nitrate, and silver oxalate, and the mass of the silver element accounts for 10 to 40% of the mass of the silver catalyst.

[0057] In this invention, during the preparation of the silver catalyst, the alkali metal promoter comprises one or more of alkali metal nitrates, sulfates, and hydroxides, wherein the alkali metal comprises at least one of lithium, sodium, potassium, rubidium, and cesium; the alkali metal content in the silver catalyst is 5–2000 ppm based on the total weight of the silver catalyst. The alkali metal promoter can be applied to the support before, simultaneously with, or after impregnation of silver, or it can be impregnated onto the support after the impregnated support has been activated.

[0058] In this invention, during the preparation of the silver catalyst, the alkaline earth metal promoter includes one or more of the alkaline earth metal acetate, oxalate, sulfate and nitrate, and the alkaline earth metal includes at least one of magnesium, calcium, strontium and barium; the content of the alkaline earth metal in the silver catalyst is 5 to 20,000 ppm based on the total weight of the silver catalyst.

[0059] In this invention, during the preparation of the silver catalyst, the rhenium promoter includes one or more of rhenium oxide, ammonium perrhenate, perrhenic acid, and cesium perrhenate; the rhenium content in the silver catalyst is 0-10000 ppm, preferably 50-10000 ppm, based on the total weight of the silver catalyst. In this invention, during the preparation of the silver catalyst, the co-promoter of the rhenium promoter includes one or more of cerium, sulfur, molybdenum, chromium salts, or oxygen anions in acid form.

[0060] In this invention, during the preparation of the silver catalyst, in order to fully impregnate the α-alumina support prepared by the above method with a solution containing sufficient amounts of organic amine, silver compound, alkali metal promoter, alkaline earth metal promoter, optional rhenium promoter, and optional rhenium promoter co-promoter, the α-alumina support is typically impregnated under a vacuum of less than 10 mmHg for 5–60 min. After impregnation, the impregnation solution is filtered, and then activated in air or a nitrogen-oxygen mixture with an oxygen content not exceeding 21% by volume at an activation temperature of 150–400 °C for 1–120 min.

[0061] In some embodiments of the present invention, the silver catalyst further includes other elements deposited on an α-alumina support, the other elements including at least one of phosphorus, boron, chromium and titanium.

[0062] In this invention, to prepare the silver catalyst, preferably, an aqueous solution of silver nitrate is first reacted with an aqueous solution of ammonium oxalate or oxalic acid to precipitate silver oxalate. The precipitate is then filtered, washed with deionized water until no nitrate ions are present, and then the silver oxalate is dissolved in an aqueous solution of an organic amine. An alkali metal auxiliary agent, an alkaline earth metal auxiliary agent, an optional rhenium auxiliary agent, and a co-auxiliary agent of the rhenium auxiliary agent are added to prepare an impregnation solution. The α-alumina support prepared by the above method is impregnated with the obtained impregnation solution, the impregnation solution is filtered, activated, and finally the silver catalyst is prepared.

[0063] To obtain silver catalysts with high silver content and / or additive content, the present invention can prepare silver-containing catalysts by one or more impregnation methods.

[0064] The alkali metals, alkaline earth metals, rhenium additives, and rhenium co-additives added during the preparation of the silver catalyst of this invention can be deposited on the support before, during, or after impregnation with silver, or they can be deposited on the support after the silver compound is activated and reduced.

[0065] A fourth aspect of the present invention provides a method for producing an epoxide compound by epoxidation of an olefin, the method comprising: epoxidizing an olefin in the presence of the above-mentioned silver catalyst to obtain the epoxide compound;

[0066] The olefin is preferably selected from at least one of styrene, propylene, ethylene and 1,3-butadiene.

[0067] The fifth aspect of the invention provides the use of the epoxy compound produced by the above method as a raw material for the production of at least one of ethylene glycol, ethylene glycol ether, and ethanolamine.

[0068] In this invention, the epoxy compound is preferably ethylene oxide.

[0069] 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.

[0070] The following examples and comparative examples demonstrate the determination of the catalytic performance of silver catalysts:

[0071] The selectivity of various silver catalysts of the present invention was 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, with inert packing material at the bottom, ensuring the catalyst bed was located in the isothermal zone of the heating mantle.

[0072] The determination conditions for activity and selectivity used in this invention are shown in Table 1:

[0073] Table 1

[0074]

[0075] Once the above reaction conditions are stabilized, the composition of the gas at the reactor inlet and outlet is continuously measured. After volume shrinkage correction, the selectivity is calculated using the following formula:

[0076] Selective

[0077] Where ΔEO is the difference in ethylene oxide concentration between the reactor outlet gas and the inlet gas, and ΔCO2 is the difference in carbon dioxide concentration between the reactor outlet gas and the inlet gas, the average of more than 10 sets of test data is taken as the test result for that day.

[0078] The porosity, tortuosity, and pore volume of the α-alumina supports in the following examples and comparative examples were determined by mercury porosimetry.

[0079] Example 1

[0080] Weigh 50g of material with a kinematic viscosity of 150mm. 2 Paraffin oil, 200.0g of diatomaceous earth, 800.0g of gibbsite, 40.0g of ethyl silicate, 10.5g of barium nitrate, and 20.0g of aluminum fluoride were mixed evenly in a mixer and then transferred to a kneader. Dilute nitric acid (nitric acid:water = 1:3, volume ratio) was added until a paste that could be extruded was formed. The paste was extruded into seven-hole cylindrical shapes and dried at 100°C for at least 24 hours to reduce the free water content to below 10%. The dried seven-hole cylindrical shapes were then calcined in a muffle furnace at 1300°C for 50 hours. Finally, they were cooled to room temperature to obtain the α-alumina support. The relevant physical property data of the α-alumina support in this example are shown in Table 2.

[0081] Example 2

[0082] Weigh out 80g of material with a kinematic viscosity of 250 mmHg. 2 The following ingredients were mixed evenly in a mixer: naphtha (200.0g), gibbsite (600.0g), trihydrate (200.0g), α-alumina (40.0g), ethyl silicate (10.5g), barium nitrate (20.0g), and aluminum fluoride (20.0g). The mixture was then transferred to a kneader, and an oxalic acid aqueous solution (oxalic acid:water = 1:2, mass ratio) was added until a paste that could be extruded was formed. The paste was then pressed into sheets, which were then pressed into single-hole cylindrical shapes. These were dried at 100°C for at least 24 hours to reduce the free water content to below 10%. The dried single-hole cylindrical shapes were then calcined in a muffle furnace at 1240°C for 40 hours. Finally, they were cooled to room temperature to obtain the α-alumina support. The relevant physical property data of the α-alumina support in this example are shown in Table 2.

[0083] Example 3

[0084] Weigh out 250g of material with a kinematic viscosity of 250mm. 2250.0g of medical white oil, 750.0g of pseudo-boehmite, 15.2g of α-alumina, 30.4g of silica, and 61.0g of calcium carbonate were mixed evenly in a mixer and then transferred to a kneader. Dilute nitric acid (nitric acid:water = 1:3, volume ratio) was added until a paste that could be extruded was formed. The paste was then rolled into single-hole cylindrical shapes and dried at 100°C for at least 24 hours to reduce the free moisture content to below 10%. The dried single-hole cylindrical shapes were then calcined in a microwave oven at 1200°C for 20 hours and finally cooled to room temperature to obtain the α-alumina carrier. The relevant physical property data of the α-alumina carrier in this example are shown in Table 2.

[0085] Example 4

[0086] Weigh 100g of material with a kinematic viscosity of 50mm. 2 Industrial white oil (800.0g), pseudo-boehmite (100.0g), boehmite (100.0g), α-alumina (100.0g), and ammonium fluoride (30.0g) were mixed evenly in a mixer and then transferred to a kneader. Dilute nitric acid (nitric acid:water = 1:3, volume ratio) was added until a paste that could be extruded was formed. The paste was extruded into a four-leaf clover shape and dried at 100℃ for at least 24 hours to reduce the free moisture content to below 10%. The dried four-leaf clover shape was then calcined in a tunnel kiln at 1300℃ for 35 hours. Finally, it was cooled to room temperature to obtain the α-alumina carrier. The relevant physical property data of the α-alumina carrier in this example are shown in Table 2.

[0087] Example 5

[0088] Weigh 200g of material with a kinematic viscosity of 100mm. 2 Rubber oil, 500.0g of diaspore monohydrate, 200.0g of gibbsite trihydrate, 300.0g of α-alumina, and 5.0g of ethyl silicate were mixed evenly in a mixer and then transferred to a kneader. Dilute nitric acid (nitric acid:water = 1:3, volume ratio) was added until a paste that could be extruded was formed. The paste was then pressed into sheets, which were then pressed into five-hole cylindrical shapes. These were dried at 100°C for at least 24 hours to reduce the free moisture content to below 10%. The dried five-hole cylindrical shapes were then calcined in a bell-shaped kiln at 1400°C for 30 hours. Finally, they were cooled to room temperature to obtain the α-alumina carrier. The relevant physical property data of the α-alumina carrier in this example are shown in Table 2.

[0089] Comparative Example 1

[0090] Weigh out 50g of graphite, 200.0g of diaspore monohydrate, 800.0g of gibbsite trihydrate, 40.0g of ethyl silicate, 10.5g of barium nitrate, and 20.0g of aluminum fluoride. Mix them thoroughly in a mixer, then transfer the mixture to a kneader. Add dilute nitric acid (nitric acid:water = 1:3, volume ratio) until a paste that can be extruded is formed. Extrude the paste into seven-hole cylindrical shapes and dry them at 100℃ for at least 24 hours to reduce the free moisture content to below 10%. Then, calcine the dried seven-hole cylindrical shapes in a muffle furnace at 1300℃ for 50 hours. Finally, cool to room temperature to obtain the α-alumina support. The relevant physical property data of the α-alumina support in this example are shown in Table 2.

[0091] Comparative Example 2

[0092] Weigh out 80g of petroleum coke, 200.0g of diaspore monohydrate, 600.0g of gibbsite trihydrate, 200.0g of α-alumina, 40.0g of ethyl silicate, 10.5g of barium nitrate, and 20.0g of aluminum fluoride. Mix them thoroughly in a mixer, then transfer the mixture to a kneader. Add an oxalic acid aqueous solution (oxalic acid:water = 1:2, mass ratio) until a paste that can be extruded is formed. Press the paste into sheets, then press it into single-hole cylindrical shapes. Dry the cylindrical shapes at 60–120℃ for at least 24 hours to reduce the free moisture content to below 10%. Then, calcine the dried cylindrical shapes in a muffle furnace at 1240℃ for 40 hours. Finally, cool to room temperature to obtain the α-alumina carrier. The relevant physical property data of the α-alumina carrier in this example are shown in Table 2.

[0093] Comparative Example 3

[0094] Weigh 100g of material with a kinematic viscosity of 5mm. 2 Industrial white oil (800.0g), pseudo-boehmite (100.0g), boehmite (100.0g), α-alumina (100.0g), and ammonium fluoride (30.0g) were mixed evenly in a mixer and then transferred to a kneader. Dilute nitric acid (nitric acid:water = 1:3, volume ratio) was added until a paste that could be extruded was formed. The paste was extruded into a four-leaf clover shape and dried at 100℃ for at least 24 hours to reduce the free moisture content to below 10%. The dried four-leaf clover shape was then calcined in a tunnel kiln at 1300℃ for 35 hours. Finally, it was cooled to room temperature to obtain the α-alumina carrier. The relevant physical property data of the α-alumina carrier in this example are shown in Table 2.

[0095] Table 2

[0096] Pore ​​volume (ml / g) Porosity (%) Tortuosity Example 1 0.58 60.1 14.7 Example 2 0.61 68.6 12.3 Example 3 0.59 63.7 17.8 Example 4 0.78 70.1 2.3 Example 5 0.60 60.3 9.5 Comparative Example 1 0.56 56.8 28.2 Comparative Example 2 0.57 58.4 25.9 Comparative Example 3 0.56 59.1 23.6

[0097] Example 6

[0098] Add 35.0g of ethylenediamine, 14.0g of ethanolamine, and 40.0g of deionized water to a stirred glass flask to prepare a mixture. Slowly add a portion of the prepared silver oxalate paste to the mixture, stirring continuously until the silver oxalate is completely dissolved. The amount of silver oxalate added should make the impregnation solution contain 24% silver (by weight). Then, add 0.50g of cesium nitrate, 1.0g of barium acetate, and 0.60g of ammonium perrhenate in sequence, and then add deionized water to make the total mass of the solution reach 200g. Mix well to prepare the impregnation solution for later use. Take 20g of the carrier from Example 1 and place it in a vacuum-capable container. Pour in the prepared impregnation solution to immerse the carrier, and evacuate to below 10mmHg. Maintain this for about 30 minutes, then filter to remove excess solution. Finally, place the filtered carrier in air at 320°C and heat for 6 minutes, then cool to prepare the silver catalyst. The silver oxalate paste is prepared by the following method:

[0099] Weigh 80.0g of silver nitrate and dissolve it in 90.0ml of deionized water. Weigh 36.0g of ammonium oxalate and dissolve it in 300.0ml of deionized water. Dissolve thoroughly to obtain silver nitrate solution and ammonium oxalate solution. Mix the two solutions under vigorous stirring to form a white silver oxalate precipitate. Aging for 1 hour, filter, and wash the filter cake with deionized water until no nitrate ions are present in the filtrate, yielding a silver oxalate paste.

[0100] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0101] Example 7

[0102] Except for taking 20g of the carrier from Example 2, the preparation method of the silver catalyst in Example 6 is the same.

[0103] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0104] Example 8

[0105] Take 20g of the carrier from Example 3, place the carrier obtained by leaching in air at 350°C and heat for 3 minutes. The rest is the same as the silver catalyst preparation method in Example 6.

[0106] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0107] Example 9

[0108] Take 20g of the carrier from Example 4, and replace 0.50g of cesium nitrate and 1.0g of barium acetate with 0.50g of cesium sulfate and 1.5g of strontium acetate. The rest of the preparation method is the same as that of the silver catalyst in Example 6.

[0109] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0110] Example 10

[0111] Take 20g of the carrier from Example 5, replace 0.60g of ammonium perrhenate with 0.70g of ammonium perrhenate, and the rest is the same as the silver catalyst preparation method in Example 9.

[0112] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0113] Comparative Example 4

[0114] Take 20g of the carrier from Comparative Example 1, and the rest are prepared in the same way as the silver catalyst in Example 6.

[0115] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0116] Comparative Example 5

[0117] Take 20g of the carrier from Comparative Example 2, and the rest are prepared in the same way as the silver catalyst in Example 7.

[0118] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0119] Comparative Example 6

[0120] Take 20g of the carrier of Comparative Example 3, and the rest are prepared in the same way as the silver catalyst in Example 8.

[0121] The activity and selectivity of the prepared catalyst were determined using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0122] Table 3

[0123] Selectivity (%) Reaction temperature (%) Example 6 84.5 217.1 Example 7 84.1 215.8 Example 8 83.8 217.3 Example 9 85.3 212.1 Example 10 85.0 216.8 Comparative Example 4 83.0 224.0 Comparative Example 5 82.5 225.1 Comparative Example 6 83.3 223.4

[0124] By comparing the data in Tables 2 and 3, it can be seen that the α-alumina prepared by adding organic oily liquid has better pore volume, porosity and lower tortuosity. This indicates that this support has a good pore structure and pore permeability. The silver catalyst prepared by this support also shows good activity and selectivity.

[0125] 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.

Claims

1. An alpha-alumina support characterized in that, The alpha-alumina carrier is prepared by a method comprising the following steps: (1) uniformly mixing an organic oily liquid, aluminum hydroxide, optional alumina, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer to obtain a solid mixture; (2) kneading, molding, drying and calcining the solid mixture with an acid solution to obtain the alpha-alumina carrier; wherein the organic oily liquid has a kinematic viscosity ≥ 10 mm 2 / s; The organic oily liquid comprises alkane and / or aromatic hydrocarbon.

2. The alpha-alumina support of claim 1, wherein, The kinematic viscosity of the organic oily liquid is > 20 mm 2 / s.

3. The alpha-alumina support of claim 1 or 2, wherein, The organic oily liquid is at least one of n-alkane, cycloalkane and aromatic hydrocarbon.

4. The alpha-alumina support of claim 3, wherein, The organic oily liquid is at least one of white oil, paraffin oil, rubber oil and naphtha.

5. The alpha-alumina support of claim 4, wherein, The white oil is at least one of medical-grade white oil, food-grade white oil, cosmetic-grade white oil and industrial-grade white oil.

6. The alpha-alumina support of claim 1 or 2, wherein, The aluminum hydroxide comprises monohydrate and optional trihydrate; The monohydrate is at least one of monohydrate boehmite, monohydrate diaspore and pseudo-monohydrate; The trihydrate is at least one of nordstrandite, gibbsite and bayerite.

7. The alpha-alumina support of claim 1 or 2, wherein, The alumina comprises at least one of gamma-alumina, theta-alumina, kappa-alumina, eta-alumina and alpha-alumina; The silicon-containing compound comprises at least one of silicon-containing sol, silicon dioxide, silicic acid, organosilicon and silicate; The alkaline earth metal compound is at least one of oxides, hydroxides, nitrates, acetates, oxalates and sulfates of alkaline earth metals; the alkaline earth metal is at least one of magnesium, calcium, strontium and barium; The mineralizer is at least one of ammonium fluoride, magnesium fluoride, aluminum fluoride, lithium fluoride, boric acid, zinc fluoride, ammonium chloride and ammonium nitrate.

8. The alpha-alumina support of claim 6 wherein, The amount of the organic oily liquid is 1.0-30.0 wt%, the amount of monohydrate is 15.0-99.0 wt%, the amount of trihydrate is 0-80.0 wt%, the amount of alumina is 0-60.0 wt%, the amount of silicon-containing compound is 0-10.0 wt%, the amount of alkaline earth metal compound is 0-5.0 wt% and the amount of mineralizer is 0-10.0 wt%, based on the total weight of the solid mixture.

9. The alpha-alumina support of claim 1 or 2, wherein, The acid solution comprises at least one of aqueous citric acid, aqueous nitric acid, aqueous formic acid, aqueous oxalic acid, aqueous acetic acid, aqueous propionic acid and aqueous hydrochloric acid.

10. The alpha-alumina support of claim 1 or 2, wherein, The drying temperature is 60-120°C; The calcining temperature is 1000-1600°C and the calcining time is 1-70h.

11. The alpha-alumina support of claim 1 or 2, wherein, The alpha-alumina carrier has at least one of the following characteristics: porosity≥45% and tortuosity≤40.

12. The alpha-alumina support of claim 11, wherein, The alpha-alumina carrier has at least one of the following characteristics: porosity≥60% and tortuosity≤23.

13. Process for the production of an alpha-alumina support according to any one of claims 1 to 12, characterized in that, The preparation method comprises: (1) uniformly mixing the organic oily liquid, aluminum hydroxide, optional alumina, optional silicon-containing compound, optional alkaline earth metal compound and optional mineralizer to obtain the solid mixture; (2) kneading, molding, drying and calcining the solid mixture with the acid solution to obtain the alpha-alumina carrier.

14. A silver catalyst characterized in that, The silver catalyst is prepared by a preparation method comprising the following steps: first, impregnating the alpha-alumina carrier according to any one of claims 1-12 with a solution comprising an organic amine, a silver-containing compound, an alkali metal promoter, an alkaline earth metal promoter, optionally a rhenium promoter, and optionally a co-promoter of the rhenium promoter, and then leaching the impregnation solution; and then activating the leached carrier to obtain the silver catalyst.

15. A process for the production of an epoxide compound by olefin epoxidation, characterized in that, The method comprises: subjecting an olefin to an epoxidation reaction in the presence of the silver catalyst according to claim 14 to obtain the epoxide compound.

16. The method of claim 15, wherein, The olefin is selected from at least one of styrene, propylene, ethylene, and 1,3-butadiene.

17. Use of the epoxide compound produced by the method according to claim 15 or 16 as a raw material for producing at least one of ethylene glycol, glycol ether, and ethanol amine.

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