Alpha-alumina carrier and preparation method thereof, silver catalyst for ethylene epoxidation and ethylene oxidation method

Abstract

The present invention belongs to the field of catalysts and relates to an α-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation and an ethylene oxidation method. The α-alumina carrier has an α-A12O3 content of more than 90% by weight; a crushing strength of 80 to 350 N / particle; and a specific surface area of ​​1.5 to 3.0 m 2 / g; water absorption rate is 30-70%; pore volume is 0.30-0.75mL / g; the crystal morphology of the α-alumina carrier includes two sizes of flake crystals, wherein the size of the larger flake crystals is 1.0-8.0μm, and the size of the smaller flake crystals is less than 1μm. Compared with the prior art, the silver catalyst made of the α-alumina carrier provided by the present invention is used for the reaction of ethylene oxidation to produce ethylene oxide, while ensuring selectivity, and has the advantages of higher activity and stability.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts, and relates to an α-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation, and an ethylene oxidation method. Specifically, the present invention relates to an α-alumina carrier, a preparation method of an α-alumina carrier, an α-alumina carrier obtained by the method, a silver catalyst made from the α-alumina carrier, and an ethylene oxidation method. More specifically, the present invention relates to an α-alumina carrier for a silver catalyst for producing ethylene oxide by ethylene oxidation, a preparation method thereof, a silver catalyst made from the carrier, and a method for producing ethylene oxide by ethylene oxidation using the 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, α-alumina is generally used as a carrier for silver catalysts. The indicators for measuring the performance of α-alumina carriers mainly include: compressive strength, specific surface area, pore volume, water absorption 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. Due to various reasons, unqualified α-alumina carriers are inevitable in production, and currently these carriers cannot be used anymore and are treated as "three wastes".

[0004] In 2020, the global demand for silver catalysts is about 6,000 tons / year, while my country's demand is about 2,000 tons / year. It is estimated that by 2022, my country's demand for silver catalysts will be about 4,600 tons / year. Used silver catalysts will be recycled for silver and auxiliary components. If the remaining carrier part and the above-mentioned unqualified α-alumina carrier can be reasonably utilized, it will help avoid waste of resources and environmental pollution. Therefore, it is of great practical significance to develop a method for the reuse of waste carriers. 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 thereof. As a result, it is found that when α-A12O3 powder of a specific particle size range obtained by crushing waste carriers with α-alumina as the main component is used as a raw material to prepare carriers, not only can the reuse of resources be achieved, but also the carrier can have a relatively small plate-like crystal morphology and a relatively high specific surface area while ensuring the compressive strength and water absorption rate of the carrier. When the silver catalyst prepared from the carrier is used for ethylene oxidation to produce ethylene oxide, the activity and stability are significantly improved while ensuring the selectivity. Based on this, the purpose of the present invention is to provide an α-alumina carrier and a preparation method, a silver catalyst for ethylene epoxidation, and an ethylene oxidation method. After the α-alumina carrier of the present invention is loaded with silver and preferably loaded with various active components to form a silver catalyst, it exhibits good activity and stability in the process of ethylene oxidation to produce ethylene oxide.

[0006] The first aspect of the present invention provides an α-alumina carrier, wherein the α-A12O3 content of the α-alumina carrier is 90% by weight or more; the crushing strength is 80 to 350 N / grain, preferably 100 to 300 N / grain; the specific surface area is 1.5 to 3.0 m 2 / g, preferably 2.0 to 3.0 m 2 / g; the water absorption rate is 30-70%, preferably 45-70%; the pore volume is 0.30-0.75mL / g, preferably 0.45-0.70mL / g; the crystal morphology of the α-alumina carrier comprises two sizes of flaky crystals, wherein the size of the larger flaky crystals is 1.0-8.0μm, preferably 3.0-6.0μm, and the size of the smaller flaky crystals is less than 1μm, preferably less than 0.8μm.

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

[0008] S1. The waste carrier with α-alumina as the main component is crushed into α-A12O3 powder, wherein the α-alumina content in the waste carrier is more than 90% by weight; the particle size of the α-A12O3 powder is 50 to 120 μm;

[0009] S2. The α-A12O3 powder obtained in step S1, A12O3 trihydrate, pseudo-monohydrate A12O3, fluoride mineralizer, pore former and burnable lubricant are mixed to obtain a solid mixture, and the solid mixture is mixed with a binder to obtain a mixture; wherein the amount of the α-A12O3 powder is 3 to 20% by weight of the total weight of the α-A12O3 powder and the A12O3 trihydrate, preferably 5 to 15% by weight;

[0010] S3. The mixture obtained in step S2 is molded to obtain a molded body;

[0011] S4. Drying and calcining the molded body obtained in step S3 to obtain the α-alumina carrier.

[0012] The third aspect of the present invention provides an α-alumina carrier prepared by the above preparation method.

[0013] A fourth aspect of the present invention provides a silver catalyst for ethylene epoxidation, the silver catalyst comprising a carrier and an active component silver supported on the carrier, the carrier being the above-mentioned α-alumina carrier.

[0014] The fifth aspect of the present invention provides an ethylene oxidation method, which comprises: subjecting ethylene to an ethylene epoxidation reaction in the presence of the above-mentioned α-alumina carrier and / or the above-mentioned silver catalyst to obtain ethylene oxide.

[0015] The present invention uses α-A12O3 powder of a specific particle size range obtained by crushing waste carriers with α-alumina as the main component as a raw material to prepare carriers, which can not only realize the reuse of resources, but also ensure the compressive strength and water absorption rate of the carrier while making the carrier have a relatively small plate-like crystal morphology and a relatively high specific surface area. Compared with the prior art, the silver catalyst made of the α-alumina carrier provided by the present invention has the advantages of higher activity and stability while ensuring selectivity when used in the reaction of ethylene oxidation to produce ethylene oxide.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0017] 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.

[0018] The present invention provides an α-alumina carrier, wherein the α-A12O3 content of the α-alumina carrier is more than 90% by weight; the crushing strength is 80 to 350 N / grain, preferably 100 to 300 N / grain; the specific surface area is 1.5 to 3.0 m 2 / g, preferably 2.0 to 3.0 m 2 / g; the water absorption rate is 30-70%, preferably 45-70%; the pore volume is 0.30-0.75mL / g, preferably 0.45-0.70mL / g; the crystal morphology of the α-alumina carrier comprises two sizes of flaky crystals, wherein the size of the larger flaky crystals is 1.0-8.0μm, preferably 3.0-6.0μm, and the size of the smaller flaky crystals is less than 1μm, preferably less than 0.8μm.

[0019] In the present invention, the lateral crushing strength of the 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 specific surface area is measured by a nitrogen physical adsorption BET method; the water absorption rate is measured by a boiling method; the pore volume is measured by a mercury injection method; and the average crystal size is measured by a scanning electron microscope observation method.

[0020] The present invention also provides a method for preparing an α-alumina carrier, the preparation method comprising the following steps:

[0021] S1. The waste carrier with α-alumina as the main component is crushed into α-A12O3 powder, wherein the α-alumina content in the waste carrier is more than 90% by weight; the particle size of the α-A12O3 powder is 50 to 120 μm;

[0022] S2. The α-A12O3 powder obtained in step S1, A12O3 trihydrate, pseudo-monohydrate A12O3, fluoride mineralizer, pore former and burnable lubricant are mixed to obtain a solid mixture, and the solid mixture is mixed with a binder to obtain a mixture; wherein the amount of the α-A12O3 powder is 3 to 20% by weight of the total weight of the α-A12O3 powder and the A12O3 trihydrate, preferably 5 to 15% by weight;

[0023] S3. The mixture obtained in step S2 is molded to obtain a molded body;

[0024] S4. Drying and calcining the molded body obtained in step S3 to obtain the α-alumina carrier.

[0025] The inventors of the present invention have discovered that the use of α-A12O3 powder in a specific particle size range obtained by crushing waste carriers with α-alumina as the main component as a raw material to prepare carriers can not only achieve the reuse of resources, but also ensure the compressive strength and water absorption rate of the carrier while having some relatively small flaky crystal morphology and a relatively high specific surface area.

[0026] According to the present invention, the waste carrier with α-alumina as the main component can be an unqualified α-alumina carrier from a laboratory or industrial production, or can be the remaining carrier portion of a catalyst with α-alumina as the carrier after industrial use and subsequent active component recovery; the catalyst with α-alumina as the carrier is preferably a silver catalyst for olefin epoxidation reaction. The waste carrier with α-alumina as the main component is crushed to obtain α-A12O3 powder, and when it is used as a raw material to prepare a carrier, the carrier morphology has a large number of tiny chips with a size of less than 1 μm in addition to conventional 1.0 to 8.0 μm flake crystals, which can ensure the carrier's compressive strength and water absorption rate while having a relatively high specific surface area.

[0027] According to a preferred embodiment of the present invention, the particle size of the trihydrate Al2O3 is 20-200 μm; based on the total weight of the solid mixture, the total amount of the α-Al2O3 powder and the trihydrate Al2O3 is 40-85% by weight, preferably 45-80% by weight; the amount of the trihydrate Al2O3 is 80-97% by weight of the total weight of the α-Al2O3 powder and the trihydrate Al2O3, preferably 85-95% by weight. The trihydrate Al2O3 is converted into stable α-Al2O3 during high-temperature calcination and becomes part of the α-Al2O3 carrier.

[0028] According to a preferred embodiment of the present invention, the particle size of the pseudo-monohydrate Al2O3 is 1 to 120 μm; based on the total weight of the solid mixture, the amount of the pseudo-monohydrate Al2O3 is 10 to 55% by weight, preferably 15 to 50% by weight. The pseudo-monohydrate Al2O3 reacts with the acid during the kneading process with the addition of a binder such as acid, and is converted into a sol, which acts as a binder. It is also converted into a stable α-A12O3 during the high-temperature roasting process, becoming a part of the α-A12O3 carrier. According to the present invention, the added binder and the pseudo-monohydrate Al2O3 generate an aluminum sol, which binds the components together to form an extrudable paste. The amount of the binder added can be the conventional amount in the art. Specifically, preferably, based on the total weight of the solid mixture, the amount of the binder added is 25 to 60% by weight of the total weight of the solid mixture. In the present invention, the types of the binder are well known to those skilled in the art, such as acids, which are usually provided in the form of an aqueous solution of the acid, preferably an aqueous nitric acid solution, wherein the weight ratio of nitric acid to water in the aqueous nitric acid solution is preferably 1:(1.25-10).

[0029] According to a specific embodiment of the present invention, in order to also play the role of a binder, the components are bonded together during the process of kneading the mixture into a paste that can be extruded, and the binder and pseudo-monohydrate Al2O3 are provided in whole or in part in the form of aluminum sol.

[0030] The addition of the fluoride mineralizer is to accelerate the crystal transformation of alumina and reduce pores below 0.5 μm. According to a preferred embodiment of the present invention, the fluoride mineralizer is one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite, and the amount of the fluoride mineralizer is 0.05 to 8% by weight, preferably 0.1 to 5% by weight, based on the total weight of the solid mixture.

[0031] The pore-forming agent is added to adjust the pore structure of the carrier to form a certain pore size distribution. According to a preferred embodiment of the present invention, the pore-forming agent is one or more of petroleum coke, activated carbon and graphite; preferably, the pore-forming agent is petroleum coke; based on the total weight of the solid mixture, the amount of the pore-forming agent is 0.05 to 10% by weight, preferably 0.1 to 8% by weight.

[0032] The burnable lubricant is added to facilitate molding and granulation of the kneaded material. At the same time, an oxidation reaction occurs during the calcination of the material, and the generated gas escapes. When the carrier is made, no or as little impurities are introduced as possible, thereby not affecting the performance of the catalyst. According to a preferred embodiment of the present invention, the burnable lubricant is vaseline and / or white oil; based on the total weight of the solid mixture, the amount of the burnable lubricant is 0.01 to 8% by weight, preferably 0.01 to 5% by weight.

[0033] According to the present invention, in step S3, the mixture obtained in step S2 is kneaded to obtain a paste, and then the paste is extruded to obtain a molded body, and the method can be carried out according to conventional techniques in the art. The shape of the molded body can be annular, spherical, cylindrical or porous cylindrical.

[0034] According to the present invention, in step S4, drying and calcining can be performed 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 80 to 120°C, and the drying time is controlled at 1 to 24 hours according to the moisture content. The calcination converts all the aluminum oxide into α-A12O3, and the calcination time can be 1 to 20 hours, preferably 2 to 15 hours; the maximum calcination temperature can be 1200 to 1500°C.

[0035] The present invention provides an α-alumina carrier prepared by the above preparation method.

[0036] The α-alumina carrier preferably has the following characteristics: an α-A12O3 content of 90 wt% or more; a crushing strength of 80 to 350 N / grain, preferably 100 to 300 N / grain; a specific surface area of ​​1.5 to 3.0 m 2 / g, preferably 2.0 to 3.0 m 2 / g; the water absorption rate is 30-70%, preferably 45-70%; the pore volume is 0.30-0.75mL / g, preferably 0.45-0.70mL / g; the crystal morphology of the α-alumina carrier comprises two sizes of flaky crystals, wherein the size of the larger flaky crystals is 1.0-8.0μm, preferably 3.0-6.0μm, and the size of the smaller flaky crystals is less than 1μm, preferably less than 0.8μm.

[0037] The present invention further provides a silver catalyst for ethylene epoxidation, the silver catalyst comprising a carrier and an active component silver supported on the carrier, the carrier being the above-mentioned α-alumina carrier;

[0038] Preferably, the silver catalyst further comprises:

[0039] Alkali metals and / or alkaline earth metals, or compounds based on alkali metals and / or alkaline earth metals;

[0040] Rhenium metal and / or rhenium-based compounds; and

[0041] 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.

[0042] According to one embodiment of the present invention, in the above-mentioned silver catalyst, based on the total weight of the silver catalyst, the mass content of silver is 5-37%, preferably 8-32%; the mass content of alkali metal is 5-3000ppm, preferably 10-2000ppm; the mass content of alkaline earth metal is 50-20000ppm, preferably 100-15000ppm; the mass content of rhenium metal is 10-2000ppm, preferably 100-1500ppm; the content of co-auxiliary agent is 0-1500ppm, calculated as the metal in the co-auxiliary agent, preferably 5-1000ppm.

[0043] The silver catalyst of the present invention can be prepared in a conventional manner, for example, by impregnating the above-mentioned α-alumina carrier with a solution containing a silver compound, an organic amine, an alkali metal promoter, an alkaline earth metal promoter, a rhenium promoter and optional co-promoters.

[0044] The organic amine may be any organic amine compound suitable for preparing a silver catalyst for producing ethylene oxide, as long as the organic amine compound can form a silver amine complex with a silver compound. For example, the organic amine may be selected from one or more of pyridine, butylamine, ethylenediamine, 1,3-propylenediamine and ethanolamine, preferably a mixture of ethylenediamine and ethanolamine.

[0045] The alkali metal additive may be a compound of lithium, sodium, potassium, rubidium or cesium or a combination of any two thereof, such as their nitrates, sulfates or hydroxides, or a combination of any two or more of the aforementioned compounds, preferably cesium sulfate and / or cesium nitrate.

[0046] The alkaline earth metal additive can be a compound of magnesium, calcium, strontium or barium, such as their oxides, oxalates, sulfates, acetates or nitrates, or a combination of any two or more of the foregoing compounds, preferably a compound of barium or strontium, more preferably barium acetate and / or strontium acetate. The alkaline earth metal additive can be applied to the support before, simultaneously with or after the silver is impregnated, or can be impregnated on the support after the silver compound is reduced.

[0047] The rhenium-containing auxiliary agent may be rhenium oxide, perrhenic acid, perrhenate, or a mixture thereof, preferably perrhenic acid and / or perrhenate, such as perrhenic acid, cesium perrhenate, and ammonium perrhenate.

[0048] The co-promoter containing the rhenium promoter can be a compound of any transition metal in the periodic table, or a mixture of several transition metal compounds, preferably one or more metals of chromium, molybdenum, tungsten and manganese, and / or compounds based on one or more elements of chromium, molybdenum, tungsten and manganese, such as one or more of chromic acid, chromium nitrate, tungstic acid, cesium tungstate, molybdic acid, ammonium molybdate, manganese acid and potassium permanganate. The rhenium promoter and its co-promoter can be applied to the support before, at the same time or after the silver is impregnated, or can be impregnated on the support after the silver compound is reduced. The activity, selectivity and stability of the activity and selectivity of the obtained silver catalyst can be further improved by adding the rhenium promoter and its co-promoter.

[0049] According to a specific embodiment of the present invention, the preparation method of the silver catalyst comprises the following steps:

[0050] (1) impregnating the porous α-alumina support with a solution containing a sufficient amount of a silver compound, an organic amine, an alkali metal promoter, an alkaline earth metal promoter, a rhenium promoter and a co-promoter;

[0051] (2) filtering off the impregnation liquid and drying the impregnated support; and

[0052] (3) activating the carrier obtained in step (2) in an oxygen-containing mixed gas to prepare the silver catalyst.

[0053] In the preparation of the silver catalyst of the present invention, silver nitrate and ammonium oxalate solution can be first mixed to generate silver oxalate, the silver oxalate is dissolved in an organic amine to form a silver amine solution, and then the above-mentioned auxiliary agent is added to form an impregnation solution; then the prepared impregnation solution is used to impregnate the above-mentioned α-alumina carrier, drained, and kept in an air flow or a nitrogen-oxygen mixed gas with an oxygen content of not more than 21% by weight (such as 8% by weight of oxygen) at a temperature range of 180-700° C., preferably 200-500° C. for 0.5-120 minutes, preferably 1-60 minutes, to perform thermal decomposition to obtain a finished silver catalyst.

[0054] The present invention also provides an ethylene oxidation method, which comprises: subjecting ethylene to an ethylene epoxidation reaction in the presence of the above-mentioned α-alumina carrier and / or the above-mentioned silver catalyst to obtain ethylene oxide. The ethylene oxidation reaction device can be any device that can perform an epoxidation reaction.

[0055] 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.

[0056] In the following examples and comparative examples:

[0057] The initial performance and stability of various silver catalysts were tested using a laboratory reactor (hereinafter referred to as "microreactor") evaluation device. The reactor used in the microreactor evaluation device is a stainless steel tube with an inner diameter of 4 mm, and the reactor is placed in a heating jacket. The catalyst loading volume is 1 mL, and there is an inert filler at the bottom, so that the catalyst bed is located in the constant temperature zone of the heating jacket.

[0058] The activity and selectivity assay conditions used are shown in Table 1:

[0059] Table 1

[0060]

[0061] When the above reaction conditions are stably reached, the gas composition at the reactor inlet and outlet is continuously measured. The selectivity S is calculated according to the following formula after volume shrinkage correction is performed on the measured results:

[0062]

[0063] Among them, ΔEO is the difference in ethylene oxide concentration between the reactor outlet gas and the inlet gas, ΔCO2 is the difference in carbon dioxide concentration between the reactor outlet gas and the inlet gas, and the average of more than 10 groups of test data is taken as the test result of the day.

[0064] Lateral crushing strength of alumina carrier: A DLⅡ intelligent particle strength tester was used to select alumina carrier samples, and the radial crushing strength was measured and the average value was taken.

[0065] Water absorption: Determined by boiling method.

[0066] Specific surface area: measured by nitrogen physical adsorption BET method.

[0067] Pore ​​volume: measured by mercury intrusion method.

[0068] Average crystal size: measured by scanning electron microscopy.

[0069] Preparation Example

[0070] The waste carrier with α-alumina as the main component (α-alumina content of more than 90% by weight) was crushed by an instrument and sieved, and particles of 50 to 120 μm were selected, which was the α-A12O3 powder required for the experiment, and was hereinafter referred to as "α-A12O3 powder obtained by crushing the waste carrier". α-A12O3 not limited to this in the comparative examples below refers to unused, fresh α-A12O3.

[0071] Examples 1-5 are used to illustrate the preparation of the alumina carrier provided by the present invention.

[0072] Example 1

[0073] 388g of 20-200μm trihydrate A12O3, 12g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0074] Example 2

[0075] 380g of 20-200μm trihydrate A12O3, 20g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0076] Example 3

[0077] 360g of 20-200μm trihydrate A12O3, 40g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0078] Example 4

[0079] 340g of 20-200μm trihydrate A12O3, 60g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0080] Example 5

[0081] 320g of 20-200μm trihydrate A12O3, 80g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0082] Examples 6-10 are used to illustrate the preparation of the silver catalyst provided by the present invention.

[0083] Example 6

[0084] 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, fully dissolve 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% by weight of silver and about 15% by weight of water.

[0085] Dissolve 70.0g of ethylenediamine in 75.0g of deionized water, add the silver oxalate filter cake prepared by the above method, continue stirring to dissolve all the silver oxalate, then add 2.58g of cesium nitrate, 6.22g of barium acetate, 0.86g of ammonium perrhenate and deionized water in sequence to make the total mass of the solution reach 400g, and prepare an impregnation solution for standby use.

[0086] Take 20g of the carrier sample prepared in Example 1, put it into a vacuum container, evacuate to above 10mmHg, introduce the above impregnation solution, keep it for 30 minutes, and filter out the excess solution. The impregnated carrier is heated in an air flow at 450℃ for 3 minutes, and cooled to prepare silver catalyst C-1.

[0087] Example 7

[0088] The same as Example 6, except that the carrier sample prepared in Example 2 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was C-2.

[0089] Example 8

[0090] The same as Example 6, except that the carrier sample prepared in Example 3 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was C-3.

[0091] Example 9

[0092] The same as Example 6, except that the carrier sample prepared in Example 4 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was C-4.

[0093] Example 10

[0094] The same as Example 6, except that the carrier sample prepared in Example 5 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was C-5.

[0095] Comparative Example 1

[0096] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0097] 400g of 20-200μm trihydrate A12O3, 100g of 1-120μm pseudo-monohydrate A12O3, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole columnar object with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and drying at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0098] Comparative Example 2

[0099] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0100] 392g of 20-200μm trihydrate A12O3, 8g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0101] Comparative Example 3

[0102] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0103] 280g of 20-200μm trihydrate A12O3, 120g of α-A12O3 powder obtained by crushing waste carriers, 100g of pseudo monohydrate A12O3 of 1-120μm, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. Dry at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0104] Comparative Example 4

[0105] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0106] 360g of 20-200μm trihydrate A12O3, 40g of 1-10μm α-A12O3, 100g of 1-120μm pseudo-monohydrate A12O3, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole columnar object with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and drying at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0107] Comparative Example 5

[0108] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0109] 360g of 20-200μm trihydrate A12O3, 40g of 10-200μm α-A12O3, 100g of 1-120μm pseudo-monohydrate A12O3, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole columnar object with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and drying at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0110] Comparative Example 6

[0111] This comparative example is used to illustrate the preparation of a reference alumina carrier.

[0112] 360g of 20-200μm trihydrate A12O3, 40g of 50-120μm α-A12O3, 100g of 1-120μm pseudo-monohydrate A12O3, 28g of magnesium fluoride and 45g of petroleum coke were put into a mixer and mixed evenly, transferred to a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) were added, and kneaded into a paste that can be extruded. Extrusion molding is a seven-hole columnar object with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and drying at 100℃ for more than 2 hours to reduce the free water content to less than 10% by weight. The carrier after kneading is placed in a bell kiln, raised from room temperature to 1400℃ over 33 hours, and calcined at 1400℃ for 5 hours to obtain a white α-A12O3 carrier. The measured carrier physical property data are shown in Table 1 below.

[0113] Comparative Example 7

[0114] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0115] Same as Example 6, except that the carrier sample prepared in Comparative Example 1 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was DC-1.

[0116] Comparative Example 8

[0117] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0118] The same as Example 6, except that the carrier sample prepared in Comparative Example 2 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was DC-2.

[0119] Comparative Example 9

[0120] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0121] The same as Example 6, except that the carrier sample prepared in Comparative Example 3 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was DC-3.

[0122] Comparative Example 10

[0123] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0124] The same as Example 6, except that the carrier sample prepared in Comparative Example 4 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was DC-4.

[0125] Comparative Example 11

[0126] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0127] The same as Example 6, except that the carrier sample prepared in Comparative Example 5 was used to replace the carrier sample prepared in Example 1. The prepared silver catalyst was DC-5.

[0128] Comparative Example 12

[0129] This comparative example is used to illustrate the preparation of a reference silver catalyst.

[0130] The same as Example 6, except that the carrier sample prepared in Comparative Example 6 is used to replace the carrier sample prepared in Example 1. The prepared silver catalyst is DC-6.

[0131] Table 1

[0132]

[0133]

[0134] Test Case

[0135] The activity and selectivity of the catalyst samples were measured under the aforementioned process conditions using a microreactor evaluation device. The microreactor evaluation results are listed in Table 2.

[0136] Table 2

[0137]

[0138] It can be seen from the data in Table 1 and Table 2 that the carrier provided by the method of the present invention has both large plate-like crystals and small plate-like crystals, and has a high specific surface area while having high compressive strength and water absorption. The catalyst prepared by the carrier of the present invention has a significantly lower reaction temperature (i.e., improved reaction activity) while ensuring selectivity, and a significantly lower increment of reaction temperature within 50 days (i.e., improved stability), and has broad application prospects.

[0139] 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.

[0140] 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. A method for preparing an α-alumina carrier, characterized in that: The preparation method comprises the following steps: S1. crushing the waste carrier with α-alumina as the main component into α-Al2O3 powder, wherein the α-alumina content in the waste carrier is more than 90% by weight; the particle size of the α-Al2O3 powder is 50 to 120 µm; S2. The α-Al2O3 powder, Al2O3 trihydrate, pseudo-monohydrate Al2O3, fluoride mineralizer, pore former and burnable lubricant obtained in step S1 are mixed to obtain a solid mixture, and the solid mixture is mixed with a binder to obtain a mixture; wherein the amount of the α-Al2O3 powder is 3 to 20% by weight of the total weight of the α-Al2O3 powder and the Al2O3 trihydrate; S3. The mixture obtained in step S2 is molded to obtain a molded body; S4. The molded body obtained in step S3 is dried and calcined to obtain the α-alumina carrier; The α-alumina carrier has an α-Al2O3 content of more than 90% by weight; a crushing strength of 80 to 350 N / grain; and a specific surface area of ​​2.0 to 3.0 m 2 / g; water absorption rate is 30-70%; pore volume is 0.30-0.75mL / g; the crystal morphology of the α-alumina carrier includes two sizes of flaky crystals, wherein the size of the larger flaky crystals is 1.0-8.0µm, and the size of the smaller flaky crystals is less than 1µm.

2. The method for preparing an α-alumina carrier according to claim 1, wherein: The amount of the α-Al2O3 powder used is 5 to 15 weight % of the total weight of the α-Al2O3 powder and Al2O3 trihydrate.

3. The method for preparing an α-alumina carrier according to claim 1, wherein: The crushing strength of the α-alumina carrier is 100-300N / grain; the water absorption rate is 45-70%; the pore volume is 0.45-0.70mL / g; the crystal morphology of the α-alumina carrier includes two sizes of flaky crystals, wherein the size of the larger flaky crystals is 3.0-6.0µm, and the size of the smaller flaky crystals is less than 0.8µm.

4. The method for preparing an α-alumina carrier according to claim 1, wherein: The waste carrier with α-alumina as the main component is an unqualified α-alumina carrier, or a remaining carrier portion after the catalyst with α-alumina as the carrier is used in industry and the subsequent active component is recovered.

5. The method for preparing an α-alumina carrier according to claim 4, wherein: The catalyst using α-alumina as a carrier is a silver catalyst used for olefin epoxidation reaction.

6. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The particle size of the Al2O3 trihydrate is 20 to 200 μm; based on the total weight of the solid mixture, the total amount of the α-Al2O3 powder and the Al2O3 trihydrate is 40 to 85 weight %; the amount of the Al2O3 trihydrate is 80 to 97 weight % of the total weight of the α-Al2O3 powder and the Al2O3 trihydrate.

7. The method for preparing an α-alumina carrier according to claim 6, wherein: Based on the total weight of the solid mixture, the total amount of the α-Al2O3 powder and Al2O3 trihydrate is 45-80% by weight; the amount of Al2O3 trihydrate is 85-95% by weight of the total weight of the α-Al2O3 powder and Al2O3 trihydrate.

8. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The particle size of the pseudo monohydrated Al2O3 is 1 to 120 μm; based on the total weight of the solid mixture, the amount of the pseudo monohydrated Al2O3 is 10 to 55% by weight.

9. The method for preparing an α-alumina carrier according to claim 8, wherein: Based on the total weight of the solid mixture, the amount of the pseudo-monohydrate Al2O3 is 15 to 50 weight %.

10. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The fluoride mineralizer is one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride and cryolite; based on the total weight of the solid mixture, the amount of the fluoride mineralizer is 0.05-8% by weight.

11. The method for preparing an α-alumina carrier according to claim 10, wherein: Based on the total weight of the solid mixture, the amount of the fluoride mineralizer is 0.1 to 5% by weight.

12. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The pore-forming agent is one or more of petroleum coke, activated carbon and graphite; based on the total weight of the solid mixture, the amount of the pore-forming agent is 0.05-10% by weight.

13. The method for preparing an α-alumina carrier according to claim 12, wherein: The pore-forming agent is petroleum coke.

14. The method for preparing an α-alumina carrier according to claim 12, wherein: Based on the total weight of the solid mixture, the amount of the pore former is 0.1 to 8% by weight.

15. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The burnable lubricating material is vaseline and / or white oil; based on the total weight of the solid mixture, the amount of the burnable lubricating material is 0.01-8% by weight.

16. The method for preparing an α-alumina carrier according to claim 15, wherein: Based on the total weight of the solid mixture, the amount of the burnable lubricating material is 0.01 to 5% by weight.

17. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The binder is an acid aqueous solution, and the weight ratio of nitric acid to water in the nitric acid aqueous solution is 1:(1.25-10); the added amount of the binder is 25-60 weight % of the total weight of the solid mixture.

18. The method for preparing an α-alumina carrier according to claim 17, wherein: The binder is a nitric acid aqueous solution.

19. The method for preparing an α-alumina carrier according to any one of claims 1 to 5, wherein: The binder and pseudo-monohydrate Al2O3 are provided in whole or in part in the form of aluminum sol.

20. An α-alumina carrier obtained by the preparation method according to any one of claims 1 to 19.

21. A silver catalyst for ethylene epoxidation, comprising a carrier and an active component silver supported on the carrier, characterized in that: The carrier is the α-alumina carrier according to claim 20.

22. The silver catalyst for ethylene epoxidation according to claim 21, wherein The silver catalyst also includes: 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.

23. A method for ethylene oxidation, characterized in that: The method comprises: subjecting ethylene to epoxidation reaction in the presence of the α-alumina carrier according to claim 20 or the silver catalyst according to claim 21 or 22 to obtain ethylene oxide.

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