Alpha-alumina carrier, preparation method thereof, silver catalyst and method for producing ethylene oxide through ethylene epoxidation

Abstract

The invention belongs to the field of silver catalysts, and relates to an alpha-alumina carrier of a silver catalyst for producing ethylene oxide through ethylene epoxidation, a preparation method of the alpha-alumina carrier, the silver catalyst and a method for producing ethylene oxide through ethylene epoxidation. The alpha-alumina carrier is prepared by forming, drying and roasting an alpha-alumina carrier precursor mixture, and the alpha-alumina carrier precursor mixture comprises: I) Al2O3 trihydrate; iI) preparing pseudo-boehmite; iII) a pore-forming agent; iV) an alkaline earth metal compound; v) a zirconium-containing compound; vI) a zirconia phase stabilizer; optionally, VIII) a fluorine-containing mineralizer; iX) a binder; and X) water. According to the alpha-aluminum oxide carrier, the zirconium oxide phase stabilizer and the zirconium-containing compound are added into the precursor mixture, and the crystalline phase of zirconium oxide in the carrier can be regulated by regulating the amount of the zirconium oxide phase stabilizer, so that the performance of a silver catalyst is regulated, and the alpha-aluminum oxide carrier shows considerable selectivity in ethylene oxide production through ethylene oxidation; the activity and the stability are obviously improved.

Description

Technical Field

[0001] The present invention belongs to the field of silver catalysts, and specifically relates to an alpha-alumina carrier of a silver catalyst for producing ethylene oxide by epoxidation of ethylene, a method for preparing the alpha-alumina carrier and the alpha-alumina carrier prepared by the method, a silver catalyst containing the carrier, and a method for producing ethylene oxide by epoxidation of ethylene using the silver catalyst. Background Art

[0002] Under the action of silver catalyst, ethylene oxidation mainly produces ethylene oxide, while side reactions produce carbon dioxide and water. Activity, selectivity and stability are the main performance indicators of silver catalysts. Among them, activity generally refers to the reaction temperature required for the ethylene oxide production process to reach a certain reaction load. The lower the reaction temperature, the higher the activity of the catalyst; selectivity refers to the ratio of the number of moles of ethylene converted into ethylene oxide to the total number of moles of ethylene in the reaction; and stability is expressed as the rate of decrease of activity and selectivity. The smaller the rate of decrease, the better the stability of the catalyst. At present, silver catalysts can be mainly divided into three types, namely high-activity, high-selectivity and medium-selectivity silver catalysts. Due to the increasing scarcity of petroleum resources and the requirement of energy conservation, high-selectivity and medium-selectivity silver catalysts have been widely used in industrial production in recent years and replaced the original high-activity silver catalysts.

[0003] The performance of silver catalysts is closely related to the performance and preparation method of the carrier used in the catalyst. At present, silver catalysts generally use α-alumina as a carrier. The indicators for measuring the performance of α-alumina carriers mainly include: compressive strength, specific surface area, pore volume, water absorption rate, tortuosity, shrinkage rate, etc. of the carrier. Appropriate compressive strength can ensure that the catalyst can withstand the reaction pressure for a long time; the appropriate specific surface area provides a location for the deposition of active components and additives; the appropriate pore volume provides a suitable space for ethylene oxidation, so that the reaction heat can be dissipated in time; and the appropriate water absorption rate can control the loading amount of active components and catalytic additives on the carrier.

[0004] As a kind of inert carrier, zirconium oxide calcined at high temperature is easy to produce oxygen vacancies and can interact with many active components in a unique way. It is one of the catalyst carriers with unique characteristics. Since pure zirconium oxide has three crystal phases, namely monoclinic, tetragonal and cubic phases, the tetragonal and cubic phases are relatively stable but their existence temperatures are all above 1100°C. The volume changes during the phase change. Doping with zirconium oxide phase stabilizer is an effective method to stabilize the high-temperature phase to room temperature. The principle is that the oxide formed after doping will be in ZrO 2 A certain pressure is applied on the lattice, making ZrO 2The coordination number is kept at 8, which can form a stable tetragonal phase structure. After doping, due to the different charges carried by different ions, a large number of oxygen vacancies will be generated in order to maintain electrical neutrality. Among them, yttria-stabilized zirconia (YSZ) is the most widely studied, but there is no relevant report on its use in silver catalysts for the production of ethylene oxide by epoxidation of ethylene. Zhang Kongyuan et al. 4 2- / ZrO 2 -Al 2 O 3 The research on solid superacid catalysts mentioned that when A1 2 O 3 When the mass fraction is greater than 5%, the tetragonal ZrO 2 Reduce, when A1 2 O 3 When the content is too high, after high temperature calcination, the monoclinic phase ZrO 2 It is difficult to crystallize into tetragonal phase. The physical and chemical properties of zirconium oxide of different crystal forms vary greatly. For example, monoclinic phase ZrO 2 and tetragonal ZrO 2 The surface acidity and alkalinity of ZrO 2 The crystal structure and surface morphology are closely related to the catalytic effect. Since the acidic center is not conducive to the performance of the silver catalyst, and the phase change of the stabilized zirconia is hindered during the temperature change process of the carrier preparation, thereby reducing the generation of cracks caused by the phase change volume change during the carrier preparation process. Therefore, it is preferred to add zirconia stabilized with zirconia phase stabilizer to the silver catalyst carrier precursor mixture to study its effect on the carrier and the silver catalyst performance. Summary of the invention

[0005] In view of the above-mentioned situation of the prior art, the inventors of the present invention have conducted extensive and in-depth research in the field of silver catalyst and carrier preparation, and found that adding zirconium oxide stabilized by a phase stabilizer to a precursor mixture to prepare an α-alumina carrier can not only effectively increase the specific surface area of ​​the carrier, but also have the advantages of higher activity and stability while ensuring the selectivity of ethylene oxidation to produce ethylene oxide. At the same time, because the preferred yttrium oxide phase stabilizer in the carrier can also react with water and CO 2 The reaction reduces the deactivation rate of the active components, and its synergistic effect with zirconium oxide and additives is beneficial to the improvement of the activity and stability of ethylene oxidation to produce ethylene oxide.

[0006] In order to achieve the purpose of the present invention, the first aspect of the present invention provides an α-alumina carrier for a silver catalyst for producing ethylene oxide by oxidation of ethylene, wherein the α-alumina carrier is prepared by molding, drying and calcining an α-alumina carrier precursor mixture, wherein the α-alumina carrier precursor mixture comprises: I) A1 trihydrate 2 O 3; II) pseudo-boehmite; III) a pore former; IV) an alkaline earth metal compound; V) a zirconium-containing compound; VI) a zirconium oxide phase stabilizer; optionally VIII) a fluorine-containing mineralizer; and X) water.

[0007] A second aspect of the present invention provides a method for preparing an α-alumina carrier, comprising the following steps:

[0008] S1. Preparation of precursor mixture: A1 trihydrate 2 O 3 , pseudo-boehmite, an alkaline earth metal compound, a pore former, an optional fluorine-containing mineralizer, a zirconium-containing compound and a zirconium oxide phase stabilizer to obtain a solid mixture, and mixing the solid mixture, a binder and water to obtain the precursor mixture;

[0009] S2. forming the precursor mixture obtained in step S1 to obtain a molded body;

[0010] S3. Drying and calcining the molded body obtained in step S2 to obtain the α-alumina carrier.

[0011] The third aspect of the present invention provides an α-alumina carrier prepared by the preparation method of the α-alumina carrier.

[0012] The fourth aspect of the present invention provides a silver catalyst for producing ethylene oxide by oxidation of ethylene, the silver catalyst comprising the α-alumina carrier and an active component silver supported on the carrier;

[0013] Preferably, the silver catalyst further comprises:

[0014] Alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals;

[0015] Rhenium metal and / or rhenium-based compounds; and

[0016] Optionally, the rhenium co-promoter is selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

[0017] The fifth aspect of the present invention provides a method for producing ethylene oxide by epoxidation of ethylene, the method comprising: subjecting ethylene to epoxidation reaction under the action of the silver catalyst to obtain ethylene oxide.

[0018] The present invention has the following advantages:

[0019] (1) The α-alumina carrier of the present invention is added with a zirconium oxide phase stabilizer and a zirconium-containing compound into a precursor mixture. By adjusting the amount of the zirconium oxide phase stabilizer, the crystal phase of zirconium oxide in the carrier can be regulated, thereby regulating the performance of the silver catalyst.

[0020] (2) In the present invention, a zirconium oxide phase stabilizer and a zirconium-containing compound are added to the precursor mixture, which has a large specific surface area. The silver catalyst prepared from the carrier has good application prospects when used for ethylene oxidation to produce ethylene oxide.

[0021] (3) After the α-alumina carrier of the present invention is loaded with silver and preferably loaded with various active components to prepare a silver catalyst, it exhibits considerable selectivity in the process of ethylene oxidation to produce ethylene oxide, while the activity and stability are significantly improved.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] In order to achieve the purpose of the present invention, the first aspect of the present invention provides an α-alumina carrier for a silver catalyst for producing ethylene oxide by oxidation of ethylene, wherein the α-alumina carrier is prepared by molding, drying and calcining an α-alumina carrier precursor mixture, wherein the α-alumina carrier precursor mixture comprises: I) A1 trihydrate 2 O 3 ; II) pseudo-boehmite; III) a pore former; IV) an alkaline earth metal compound; V) a zirconium-containing compound; VI) a zirconium oxide phase stabilizer; optionally VIII) a fluorine-containing mineralizer; and X) water.

[0025] In the present invention, "optionally" means that the compound may or may not be contained in the mixture.

[0026] According to the present invention, preferably, when the precursor mixture contains a fluorine-containing mineralizer, the crystal morphology of the α-alumina carrier is a lamellar crystal; when the precursor mixture does not contain a fluorine-containing mineralizer, the crystal morphology of the α-alumina carrier is an α-alumina carrier with a worm-like morphology.

[0027] According to the present invention, preferably, the content of the zirconium oxide phase stabilizer is trihydrate A1 2 O 3 0.01 to 1% by weight of the total weight of pseudo-boehmite, preferably 0.05 to 0.5% by weight.

[0028] According to the present invention, preferably, the zirconia phase stabilizer is a rare earth oxide and a precursor, or a mixture of a rare earth oxide and a divalent alkaline earth metal oxide and a precursor, wherein the mass ratio of the rare earth oxide to the divalent alkaline earth metal oxide in the mixture is 1:0.8-2.

[0029] Preferably, the rare earth oxide and precursor are at least one of yttrium oxide, yttrium nitrate, lanthanum oxalate, lanthanum carbonate, yttrium oxalate, lanthanum hydroxide and yttrium sulfate; the divalent alkaline earth metal oxide and precursor are at least one of calcium oxide, calcium silicate and calcium carbonate.

[0030] According to the present invention, preferably, the zirconium-containing compound and the zirconium oxide phase stabilizer are added to the precursor mixture separately and / or added to the precursor mixture together in the form of stabilized zirconium oxide.

[0031] According to the present invention, preferably, the zirconium-containing compound and the zirconium oxide phase stabilizer are added to the precursor mixture in the form of stabilized zirconium oxide.

[0032] According to the present invention, preferably, the zirconium-containing compound is at least one of zirconium oxide, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium nitrate and zirconium oxalate.

[0033] According to the present invention, preferably, the content of the zirconium-containing compound is trihydrate A1 2 O 3 1 to 20% by weight of the total weight of the pseudo-boehmite, preferably 1 to 8% by weight.

[0034] According to the present invention, preferably, the trihydrate A1 2 O 3 At least one selected from gibbsite, norwater and gibbsite; the gibbsite A1 2 O 3 The particle size of the pseudo-boehmite is 20 to 200 μm, the particle size of the pseudo-boehmite is 1 to 120 μm; the pore-forming agent is selected from at least one of petroleum coke, carbon powder, graphite, rosin, polyethylene and polypropylene; the alkaline earth metal compound is selected from at least one of alkaline earth metal oxides, hydroxides, sulfates, nitrates and oxalates; the fluorine-containing mineralizer is selected from at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite; based on the total weight of the solid mixture, the trihydrate Al 2 O 3 The addition amount of the pseudo-boehmite is 40 to 85% by weight, preferably 45 to 80% by weight, the addition amount of the pseudo-boehmite is 10 to 55% by weight, preferably 15 to 50% by weight, the addition amount of the pore-forming agent is 5 to 20% by weight, the addition amount of the alkaline earth metal compound is 0.1 to 5% by weight, and the addition amount of the fluorine-containing mineralizer is 0 to 8% by weight, preferably 0.1 to 5% by weight.

[0035] Preferably, the binder is an acid; the acid is preferably an aqueous nitric acid solution, wherein the volume ratio of nitric acid to water is 1:1.25-10, preferably 1:2-4; the pseudo-monohydrate alumina and the binder are partially or completely provided in the form of aluminum sol.

[0036] According to the present invention, preferably, the α-alumina carrier has the following characteristics: α-A1 2 O 3 The content is 90% by weight or more, the crushing strength is 70 to 350 N / grain, preferably 70 to 150 N / grain, and the specific surface area is 1 to 3.0 m 2 / g, preferably 1.1 to 2.0 m 2 / g, the water absorption rate is 30-70%, preferably 45-70%, and the pore volume is 0.30-0.75mL / g, preferably 0.45-0.70mL / g.

[0037] A second aspect of the present invention provides a method for preparing an α-alumina carrier, comprising the following steps:

[0038] S1. Preparation of precursor mixture: A1 trihydrate 2 O 3 , pseudo-boehmite, an alkaline earth metal compound, a pore former, an optional fluorine-containing mineralizer, a zirconium-containing compound and a zirconium oxide phase stabilizer to obtain a solid mixture, and mixing the solid mixture, a binder and water to obtain the precursor mixture;

[0039] S2. forming the precursor mixture obtained in step S1 to obtain a molded body;

[0040] S3. Drying and calcining the molded body obtained in step S2 to obtain the α-alumina carrier.

[0041] In step S1 of the present invention, a support is prepared by adding a zirconium oxide phase stabilizer and a zirconium-containing compound to a precursor mixture. The zirconium-containing compound and the zirconium oxide phase stabilizer can be added to the precursor mixture separately, and / or can be added to the precursor mixture in the form of stabilized zirconium oxide stabilized by the zirconium oxide phase stabilizer, preferably in the form of yttria-stabilized zirconium oxide (YSZ).

[0042] According to a specific embodiment of the present invention, when the zirconium-containing compound and the zirconium oxide phase stabilizer are added separately to the precursor mixture, step S1 comprises: adding trihydrate A1 2 O 3 , pseudo-boehmite, alkaline earth metal compounds, pore formers, fluorine-containing mineralizers, zirconium oxide phase stabilizers, and zirconium-containing compounds to prepare a solid mixture, and the solid mixture is mixed with a binder and water to obtain the precursor mixture.

[0043] According to a specific embodiment of the present invention, when the zirconium-containing compound and the zirconium oxide phase stabilizer are added to the precursor mixture in the form of stabilized zirconium oxide stabilized by the zirconium oxide phase stabilizer, step S1 comprises: adding trihydrate A1 2 O 3, pseudo-boehmite, alkaline earth metal compounds, pore formers, fluorine-containing mineralizers, and zirconium oxide stabilized by zirconium oxide phase stabilizers to prepare a solid mixture, and the solid mixture is mixed with a binder and water to obtain the precursor mixture.

[0044] According to a specific embodiment of the present invention, when the zirconium oxide phase stabilizer is added alone and in the form of stabilized zirconium oxide prepared in advance using a sol-gel technique of an alkoxide of an element or a microemulsion technique using a salt solution, step S1 comprises: adding trihydrate A1 2 O 3 , pseudo-boehmite, oxalic acid powder, alkaline earth metal compound, pore former, fluorine-containing mineralizer, zirconia phase stabilizer, zirconia stabilized by zirconia phase stabilizer, to prepare a solid mixture, and mix the solid mixture with a binder and water to obtain the precursor mixture.

[0045] In the present invention, while ensuring selectivity, yttria-stabilized zirconium oxide (YSZ) is preferably added to the precursor mixture, which is more conducive to improving the activity and stability of the silver catalyst prepared by the carrier when used for ethylene oxidation to produce ethylene oxide.

[0046] According to the present invention, preferably, the zirconia phase stabilizer is a rare earth oxide and a precursor, or a mixture of a rare earth oxide and a divalent alkaline earth metal oxide and a precursor, wherein the mass ratio of the rare earth oxide to the divalent alkaline earth metal oxide in the mixture is 1:0.8-2; preferably, the rare earth oxide and the precursor are at least one of yttrium oxide, yttrium nitrate, lanthanum oxalate, lanthanum carbonate, yttrium oxalate, lanthanum hydroxide and yttrium sulfate; the divalent alkaline earth metal oxide and the precursor are at least one of calcium oxide, calcium silicate and calcium carbonate.

[0047] According to the present invention, preferably, the zirconium-containing compound is at least one of zirconium oxide, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium nitrate and zirconium oxalate.

[0048] According to the present invention, preferably, the content of the zirconium oxide phase stabilizer is trihydrate A1 2 O 3 and pseudo-boehmite by weight, preferably 0.05 to 0.5 weight percent, and the content of the zirconium-containing compound is A1 trihydrate. 2 O 3 1 to 20% by weight of the total weight of the pseudo-boehmite, preferably 1 to 5% by weight.

[0049] According to the present invention, preferably, the trihydrate A1 2 O 3 At least one selected from gibbsite, norwater and gibbsite; the gibbsite A1 2 O 3The particle size of the pseudo-boehmite is 20 to 200 μm, and the particle size of the pseudo-boehmite is 1 to 120 μm; the pore-forming agent is selected from at least one of petroleum coke, carbon powder, graphite, rosin, polyethylene and polypropylene; the alkaline earth metal compound is selected from at least one of the oxides, hydroxides, sulfates, nitrates and oxalates of alkaline earth metals; the fluorine-containing mineralizer is selected from at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite; the binder is an acid, and the acid is preferably an aqueous nitric acid solution, wherein the volume ratio of nitric acid to water is 1:1.25 to 10, preferably 1:2 to 4; the pseudo-monohydrate alumina and the binder are partially or completely provided in the form of aluminum sol.

[0050] In the present invention, during the preparation of the α-alumina carrier, alumina trihydrate undergoes dehydration and a crystal phase transformation of alumina with different crystal phases, and is finally transformed into α-alumina.

[0051] According to the present invention, preferably, based on the total weight of the solid mixture, the trihydrate A1 2 O 3 The amount of the added substance is 40 to 85% by weight, preferably 45 to 80% by weight, the amount of the added substance of the pseudo-boehmite is 10 to 55% by weight, preferably 15 to 50% by weight, the amount of the added substance of the pore-forming agent is 5 to 20% by weight, the amount of the added substance of the alkaline earth metal compound is 0.1 to 5% by weight, the amount of the added substance of the fluorine-containing mineralizer is 0 to 8% by weight, preferably 0.1 to 5% by weight, and the content of the zirconium-containing compound is A1 trihydrate. 2 O 3 and pseudo-boehmite by weight, preferably 1 to 5% by weight, and the content of the zirconium oxide phase stabilizer is A1 trihydrate 2 O 3 and 0.01 to 1 weight percent of the total weight of pseudo-boehmite.

[0052] In the present invention, during the preparation process of the α-alumina carrier of the present invention, the pseudo-boehmite and the binder generate aluminum sol, which binds the components together to form a paste that can be extruded and formed. During the high-temperature roasting process, the pseudo-boehmite is also converted into α-alumina. According to the present invention, the pseudo-boehmite is preferably added in an amount of 10% to 50% based on the total weight of the solid mixture.

[0053] In the present invention, the method for obtaining the molded body in step S2 can be carried out according to the conventional technology in the art. The shape of the molded body can be annular, spherical, cylindrical or porous cylindrical. The solid powder is mixed with a binder and water to obtain a mixture which needs to be kneaded. The kneading can be carried out in a kneading machine. The kneading time can be 10 to 60 minutes. The paste is kneaded into an extrudable paste. The paste is formed in a molding machine to form an annular, spherical, cylindrical, single-hole or porous columnar, or multi-leaf clover shape.

[0054] In the present invention, in step S3, the drying and calcining methods can be carried out in accordance with conventional methods in the art. Preferably, the molded body can be dried to contain less than 10% by weight of free water, the drying temperature can be 20 to 100° C., and the drying time is controlled at 20 to 48 hours according to the moisture content. The high temperature calcination temperature is 1200 to 1550° C., and the calcination time is 1 to 60 hours.

[0055] The third aspect of the present invention provides an α-alumina carrier prepared by the preparation method of the α-alumina carrier.

[0056] The fourth aspect of the present invention provides a silver catalyst for producing ethylene oxide by oxidation of ethylene, the silver catalyst comprising the α-alumina carrier and an active component silver supported on the carrier;

[0057] Preferably, the silver catalyst further comprises:

[0058] Alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals;

[0059] Rhenium metal and / or rhenium-based compounds; and

[0060] Optionally, the rhenium co-promoter is selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

[0061] In the present invention, the silver catalyst of the present invention can be prepared by known methods or any conventional methods, such as impregnating the α-alumina carrier with a solution containing sufficient amounts of organic amine, silver compound, alkali metal promoter, alkaline earth metal promoter, optional rhenium promoter and co-promoter of rhenium promoter.

[0062] According to the present invention, the silver catalyst further comprises other elements deposited on the α-alumina carrier, wherein the other elements include one or more of phosphorus, boron, chromium and titanium.

[0063] According to a preferred embodiment of the present invention, the silver catalyst is prepared by a method comprising the following steps: Ⅰ) impregnating an α-alumina carrier prepared according to the method of the present invention with a solution containing a sufficient amount of an organic amine, a silver compound, an alkali metal promoter, an alkaline earth metal promoter, an optional rhenium promoter and a co-promoter of the rhenium promoter; Ⅱ) leaching the impregnation solution; Ⅲ) activating the carrier obtained in step Ⅱ) in an oxygen-containing gas to prepare the silver catalyst.

[0064] According to the present invention, in the process of preparing the silver catalyst, the organic amine can be selected from one or more of 1,2-propylenediamine, 1,3-propylenediamine, ethylenediamine, 1,2-butylenediamine, 1,3-butylenediamine, pyridine, ethylamine, n-propylamine, n-butylamine, isobutylamine, tert-butylamine, sec-butylamine, ethanolamine, propanolamine and butanolamine; the silver compound can be selected from one or more of silver oxide, silver nitrate and silver oxalate; the alkali metal auxiliary agent can be selected from one or more of lithium, sodium, potassium, rubidium and cesium; the alkaline earth metal auxiliary agent can be selected from one or more of magnesium, calcium, strontium and barium; the rhenium auxiliary agent can be selected from one or more of rhenium oxide, ammonium perrhenate, perrhenic acid and cesium perrhenate; the co-auxiliary agent of the rhenium auxiliary agent can be selected from one or more of oxygen anions in the form of salts or acids of cerium, sulfur, molybdenum and chromium.

[0065] According to the present invention, the mass of silver element accounts for 10-40% of the mass of the silver catalyst; the mass of alkali metal additive accounts for 5-2000ppm of the mass of the silver catalyst; the mass of alkaline earth metal additive accounts for 5-20000ppm of the mass of the silver catalyst; the mass of rhenium additive accounts for 50-10000ppm of the mass of the silver catalyst.

[0066] In the silver catalyst preparation method of the present invention, activation is carried out in an oxygen-containing mixed gas, which includes air flow or a nitrogen-oxygen mixed gas with an oxygen content of no more than 21%; the activation temperature is 180-700° C., and the activation time is 1-120 minutes.

[0067] In the present invention, in order to prepare the silver catalyst of the present invention, an aqueous solution of silver nitrate can be first reacted with an aqueous solution of ammonium oxalate or oxalic acid to precipitate a silver oxalate precipitate, which is then filtered and washed with deionized water until no nitrate ions are present. The silver oxalate is then dissolved in an aqueous solution of an organic amine, and an alkali metal auxiliary, an alkaline earth metal auxiliary, an optional rhenium auxiliary and a co-auxiliary of the rhenium auxiliary are added to prepare an impregnation solution. The obtained impregnation solution is used to impregnate the α-alumina carrier prepared by the method of the present invention, the impregnation solution is leached, and the silver catalyst is finally prepared.

[0068] In order to obtain a silver catalyst with a higher silver content and / or promoter content, the present invention can prepare the silver-containing catalyst by one or more impregnation methods.

[0069] The alkali metal, alkaline earth metal, rhenium promoter and rhenium co-promoter added in the preparation process of the silver catalyst of the present invention can be deposited on the carrier before, simultaneously or after the silver is impregnated, or can be deposited on the carrier after the silver compound is activated and reduced.

[0070] The fifth aspect of the present invention provides a method for producing ethylene oxide by epoxidation of ethylene, the method comprising: subjecting ethylene to epoxidation reaction under the action of the silver catalyst to obtain ethylene oxide.

[0071] In the present invention, the olefin may include one or more of styrene, propylene, ethylene and 1,3-butadiene. The olefin epoxidation reaction device may be any device capable of performing epoxidation reaction.

[0072] The present invention will be further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0073] Determination of catalytic performance of silver catalyst:

[0074] The selectivity of various silver catalysts of the present invention was tested using a laboratory microreactor evaluation device. The reactor used in the microreactor evaluation device was a stainless steel reaction tube with an inner diameter of 4 mm, and the reaction tube was placed in a heating jacket. The catalyst was loaded with an inert filler at the bottom so that the catalyst bed was located in the constant temperature zone of the heating jacket.

[0075] The activity and selectivity test conditions used in the present invention are shown in Table 1:

[0076] Table 1

[0077]

[0078] When the above reaction conditions are stably reached, the gas composition at the reactor inlet and outlet is continuously measured. The selectivity is calculated according to the following formula after volume shrinkage correction is performed on the measured results:

[0079] Selectivity

[0080] Where ΔEO is the difference in ethylene oxide concentration between the reactor outlet gas and the reactor inlet gas, ΔCO 2 It is the difference in carbon dioxide concentration between the reactor outlet gas and the inlet gas. The average of more than 10 groups of test data is taken as the test result of the day.

[0081] In the present invention, the lateral crushing strength of the alumina carrier is measured by a DLⅡ intelligent particle strength tester, and a carrier sample is selected, and the radial crushing strength is measured and the average value is obtained; the water absorption rate is measured by a density method; the specific surface area is measured by a nitrogen physical adsorption BET method; the pore distribution, tortuosity, shrinkage and permeability are measured by a mercury injection method.

[0082] The present invention will be further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0083] The yttria-stabilized zirconia (YSZ) described in the embodiments of the present invention was purchased from MCC New Materials.

[0084] Comparative Example 1

[0085] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, and 40.0g of petroleum coke, transfer them to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude it into a seven-hole column, dry it at 60-120°C for 30h, reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in this comparative example 1 is numbered Ccar-1, and the relevant physical property data are shown in Table 2.

[0086] Comparative Example 2

[0087] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, and 30g of zirconium oxide, transfer them to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude it into a seven-hole column, dry it at 60-120°C for 30h, reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in this comparative example 2 is numbered Ccar-2, and the relevant physical property data are shown in Table 2.

[0088] Examples 1-6 are used to illustrate the preparation of the alumina carrier provided by the present invention.

[0089] Example 1

[0090] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, 0.54g of calcium oxide and 7g of yttria-stabilized zirconia (YSZ), which contains 0.56g of yttria, transfer to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude into a seven-hole column, dry at 60-120°C for 30h to reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 1 is numbered Scar-1, and the relevant physical property data are shown in Table 2.

[0091] Example 2

[0092] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, and calcium oxide-doped yttria-stabilized zirconia (YSZ), which contains 3g of calcium oxide, 3g of yttria, and 30g of zirconium oxide, transfer to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude into a seven-hole column, dry at 60-120°C for 30h to reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 2 is numbered Scar-2, and the relevant physical property data are shown in Table 2.

[0093] Example 3

[0094] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, 3g of calcium oxide, 3g of yttrium oxide, and 30g of zirconium oxide, transfer them to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude it into a seven-hole column, dry it at 60-120°C for 30h to reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, the constant temperature roasting is 10h, and finally cooled to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 3 is numbered Scar-3, and the relevant physical property data are shown in Table 2.

[0095] Example 4

[0096] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, 3g of lanthanum oxide, 2g of yttrium nitrate, and 30g of zirconium oxalate, transfer them to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude it into a seven-hole column, dry it at 60-120°C for 30h, reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 4 is numbered Scar-4, and the relevant physical property data are shown in Table 2.

[0097] Example 5

[0098] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, 2g of lanthanum oxide, 4g of yttrium oxide, and 30g of zirconium hydroxide, transfer them to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude it into a seven-hole column, dry it at 60-120°C for 30h, reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 5 is numbered Scar-5, and the relevant physical property data are shown in Table 2.

[0099] Example 6

[0100] Weigh 470.0g of gibbsite, 130.0g of pseudo-boehmite, 16.0g of aluminum fluoride, 5.0g of barium carbonate, 40.0g of petroleum coke, and 7g of yttria-stabilized zirconia (YSZ), which contains 0.56g of yttria, transfer to a kneader, add dilute nitric acid (nitric acid: water = 1:3, volume ratio) until kneading into a paste that can be extruded, put the paste into an extruder, extrude into a seven-hole column, dry at 60-120°C for 30h to reduce the free water content to less than 10%, then put the dried seven-hole column into a natural gas kiln for roasting, the roasting temperature is 1300°C, constant temperature roasting for 10h, and finally cool to room temperature to obtain an α-alumina carrier. The α-alumina carrier prepared in Example 6 is numbered Scar-6, and the relevant physical property data are shown in Table 2.

[0101] Catalyst preparation example:

[0102] Weigh 140g of silver nitrate and dissolve it in 150ml of deionized water, weigh 64g of ammonium oxalate and dissolve it in 520ml of deionized water to obtain a silver nitrate solution and an ammonium oxalate solution, mix the two solutions under vigorous stirring to generate a white silver oxalate precipitate, age for more than 30 minutes, filter, and wash the precipitate with deionized water until there is no nitrate ion. The filter cake contains about 60% silver and about 15% water. Add 82g of n-propylamine and 75g of deionized water in a stirred glass flask to make a mixed solution, slowly add the prepared silver oxalate paste to the mixed solution, continue stirring to dissolve all the silver oxalate, and the amount of silver oxalate added makes the prepared impregnation solution contain 22% (mass) of silver, then add 0.8g of cesium acetate, 0.5g of barium acetate, and 0.5g of ammonium perrhenate in sequence, and then add deionized water to make the total mass of the solution reach 400g, mix evenly to make an impregnation solution for standby use. Take 20g of Ccar-1, Ccar-2, Scar-1, Scar-2, Scar-3, Scar-4, Scar-5 and Scar-6 carriers respectively and put them into a vacuum container, pour the prepared impregnation solution, immerse the carriers, evacuate to less than 10mmHg, keep for about 30 minutes, and remove the excess solution by leaching. Finally, place the impregnated carriers in air at 280℃ and heat for 3 minutes, and cool them to prepare silver catalysts.

[0103] Catalyst performance evaluation:

[0104] The activity and selectivity of the catalyst samples prepared at different stages were measured using a microreactor evaluation device under the aforementioned process conditions. The test results are listed in Table 3.

[0105] Table 2

[0106]

[0107]

[0108] Table 3

[0109]

[0110] By comparing the data in Table 2 and Table 3, it can be seen that the support prepared by adding zirconium oxide phase stabilizer and zirconium-containing compound to the precursor mixture is more conducive to the increase of the specific surface area of ​​α-alumina support, and the silver catalyst prepared by this support shows good activity and stability in the ethylene epoxidation reaction to produce ethylene oxide.

[0111] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0112] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. An alpha-alumina carrier for a silver catalyst for producing ethylene oxide by oxidation of ethylene, characterized in that: The α-alumina carrier is prepared by molding, drying and calcining an α-alumina carrier precursor mixture, wherein the α-alumina carrier precursor mixture comprises: I) Al2O3 trihydrate; II) pseudo-boehmite; III) a pore former; IV) an alkaline earth metal compound; V) a zirconium-containing compound; VI) a zirconium oxide phase stabilizer; optionally VIII) a fluorine-containing mineralizer; IX) a binder; and X) water.

2. The α-alumina carrier according to claim 1, wherein The content of the zirconium oxide phase stabilizer is 0.01 to 1.5 weight % of the total weight of Al2O3 trihydrate and pseudo-boehmite, preferably 0.5 to 1.5 weight %.

3. The α-alumina carrier according to claim 1, wherein The zirconium oxide phase stabilizer is a rare earth oxide and a precursor, or a mixture of a rare earth oxide and a divalent alkaline earth metal oxide and a precursor, wherein the mass ratio of the rare earth oxide to the divalent alkaline earth metal oxide in the mixture is 1:0.8-2; Preferably, the rare earth oxide and precursor are at least one of yttrium oxide, yttrium nitrate, lanthanum oxalate, lanthanum carbonate, yttrium oxalate, lanthanum hydroxide and yttrium sulfate; the divalent alkaline earth metal oxide and precursor are at least one of calcium oxide, calcium silicate and calcium carbonate.

4. The α-alumina carrier according to any one of claims 1 to 3, wherein The zirconium-containing compound and the zirconium oxide phase stabilizer are added to the precursor mixture separately and / or added to the precursor mixture together in the form of stabilized zirconium oxide.

5. The α-alumina carrier according to any one of claims 1 to 3, wherein The zirconium-containing compound is at least one of zirconium oxide, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium nitrate and zirconium oxalate; The content of the zirconium-containing compound is 1 to 20% by weight, preferably 1 to 8% by weight, of the total weight of Al2O3 trihydrate and pseudo-boehmite.

6. The α-alumina carrier according to any one of claims 1 to 3, wherein The trihydrate A12O3 is selected from at least one of gibbsite, norwater and gibbsite; the particle size of the trihydrate A12O3 is 20-200 μm, and the particle size of the pseudo-boehmite is 1-120 μm; the pore-forming agent is selected from at least one of petroleum coke, carbon powder, graphite, rosin, polyethylene and polypropylene; the alkaline earth metal compound is selected from at least one of the oxides, hydroxides, sulfates, nitrates and oxalates of alkaline earth metals; the fluorine-containing mineralizer is selected from at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite; Based on the total weight of the α-alumina carrier precursor mixture, the content of the trihydrate A12O3 is 40 to 85% by weight, preferably 45 to 80% by weight, the content of the pseudo-boehmite is 10 to 55% by weight, preferably 15 to 50% by weight, the content of the pore-forming agent is 5 to 20% by weight, the content of the alkaline earth metal compound is 0.1 to 5% by weight, and the content of the fluorine-containing mineralizer is 0 to 8% by weight, preferably 0.1 to 5% by weight; The binder is an acid; the acid is preferably an aqueous nitric acid solution, wherein the volume ratio of nitric acid to water is 1:1.25-10, preferably 1:2-4; the pseudo-monohydrate alumina and the binder are partially or completely provided in the form of aluminum sol.

7. The α-alumina carrier according to any one of claims 1 to 3, wherein The α-alumina carrier has the following characteristics: an α-A12O3 content of more than 90% by weight, a crushing strength of 70 to 350 N / grain, preferably 70 to 150 N / grain, and a specific surface area of ​​1.0 to 3.0 m 2 / g, preferably 1.1 to 2.0 m 2 / g, the water absorption rate is 30-70%, preferably 45-70%, and the pore volume is 0.30-0.75mL / g, preferably 0.45-0.70mL / g.

8. A method for preparing an α-alumina carrier, characterized in that: The steps include: S1. Preparing a precursor mixture: A12O3 trihydrate, pseudo-boehmite, an alkaline earth metal compound, a pore-forming agent, an optional fluorine-containing mineralizer, a zirconium-containing compound and a zirconium oxide phase stabilizer are mixed to obtain a solid mixture, and the solid mixture, a binder and water are mixed to obtain the precursor mixture; S2. forming the precursor mixture obtained in step S1 to obtain a molded body; S3. Drying and calcining the molded body obtained in step S2 to obtain the α-alumina carrier.

9. The method for preparing an α-alumina carrier according to claim 8, wherein: The zirconium-containing compound and the zirconium oxide phase stabilizer are added to the precursor mixture separately or in the form of zirconium oxide stabilized by the zirconium oxide phase stabilizer.

10. The method for preparing an α-alumina carrier according to claim 8, wherein: The zirconium oxide phase stabilizer is a rare earth oxide and a precursor, or a mixture of a rare earth oxide and a divalent alkaline earth metal oxide and a precursor, wherein the mass ratio of the rare earth oxide to the divalent alkaline earth metal oxide in the mixture is 1:0.8-2; preferably, the rare earth oxide and the precursor are at least one of yttrium oxide, yttrium nitrate, lanthanum oxalate, lanthanum carbonate, yttrium oxalate, lanthanum hydroxide and yttrium sulfate; the divalent alkaline earth metal oxide and the precursor are at least one of calcium oxide, calcium silicate and calcium carbonate; The zirconium-containing compound is at least one of zirconium oxide, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium nitrate and zirconium oxalate; The content of the zirconium oxide phase stabilizer is 0.01-1% by weight of the total weight of Al2O3 trihydrate and pseudo-boehmite, preferably 0.05-0.5% by weight, and the content of the zirconium-containing compound is 1-20% by weight of the total weight of Al2O3 trihydrate and pseudo-boehmite, preferably 1-8% by weight.

11. The method for preparing an α-alumina carrier according to claim 8, wherein: The trihydrate A12O3 is selected from at least one of gibbsite, gibbsite and gibbsite; the particle size of the trihydrate A12O3 is 20-200 μm, and the particle size of the pseudo-boehmite is 1-120 μm; the pore-forming agent is selected from at least one of petroleum coke, carbon powder, graphite, rosin, polyethylene and polypropylene; the alkaline earth metal compound is selected from at least one of the oxides, hydroxides, sulfates, nitrates and oxalates of alkaline earth metals; the fluorine-containing mineralizer is selected from at least one of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite; the binder is an acid, and the acid is preferably an aqueous nitric acid solution, wherein the volume ratio of nitric acid to water is 1:1.25-10, preferably 1:2-4; the pseudo-monohydrate alumina and the binder are partially or completely provided in the form of aluminum sol; Based on the total weight of the α-alumina carrier precursor mixture, the content of Al2O3 trihydrate is 40 to 85% by weight, preferably 45 to 80% by weight, the content of pseudo-boehmite is 10 to 55% by weight, preferably 15 to 50% by weight, the content of the pore-forming agent is 5 to 20% by weight, the content of the alkaline earth metal compound is 0.1 to 5% by weight, and the content of the fluorine-containing mineralizer is 0 to 8% by weight, preferably 0.1 to 5% by weight.

12. An α-alumina carrier obtained by the method for preparing an α-alumina carrier according to any one of claims 8 to 11.

13. A silver catalyst for producing ethylene oxide by ethylene oxidation, characterized in that: The silver catalyst comprises the α-alumina carrier according to any one of claims 1 to 8 and 12 and an active component silver supported on the carrier; Preferably, the silver catalyst further comprises: Alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals; Rhenium metal and / or rhenium-based compounds; and Optionally, the rhenium co-promoter is selected from at least one metal selected from chromium, molybdenum, tungsten and manganese, and / or selected from compounds based on at least one metal selected from chromium, molybdenum, tungsten and manganese.

14. A method for producing ethylene oxide by epoxidation of ethylene, characterized in that: The method comprises: subjecting ethylene to epoxidation reaction under the action of the silver catalyst described in claim 13 to obtain ethylene oxide.

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