Modified alpha-alumina carrier, preparation method thereof, silver catalyst and application of silver catalyst

Abstract

The invention relates to the field of catalysts, in particular to a modified alpha-alumina carrier and a preparation method thereof as well as a silver catalyst and application thereof, and the modified alpha-alumina carrier is prepared by sequentially forming, drying, roasting, reducing, vulcanizing and purging a precursor mixture of the modified alpha-alumina carrier; the precursor mixture comprises the following components: a component a: alpha-Al2O3 trihydrate; a component b: false Al2O3 monohydrate; a component c: a heavy alkaline earth metal compound; a component d: a mineralizing agent; a component e: elemental copper and / or a copper-containing compound; a component f: elemental tungsten and / or a tungsten-containing compound; a component g: a binder; and a component h: optional water. The carrier has high specific surface area and strength, and has more macropores. A silver catalyst prepared from the modified alpha-aluminum oxide is beneficial to dispersion of a reaction active center, the catalytic performance of the active center is improved, and desorption of products is facilitated. The catalyst is applied to the reaction process of producing ethylene oxide through ethylene oxidation, and the activity and selectivity are improved.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst carrier and catalyst preparation, and in particular to a modified alpha-alumina carrier and a preparation method thereof, a silver catalyst and an application thereof. Background Art

[0002] Under the action of silver catalyst, ethylene oxidation mainly produces ethylene oxide, while side reactions also occur to produce carbon dioxide and water, among which activity, selectivity and stability are the main performance indicators of silver catalyst. The so-called activity 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. The so-called selectivity refers to the ratio of the number of moles of ethylene converted into ethylene oxide to the total number of moles of ethylene reacted in the reaction. The so-called 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.

[0003] In the process of ethylene oxidation to produce ethylene oxide, the use of highly active, highly selective and stable silver catalysts can greatly improve economic benefits. Therefore, the manufacture of highly active, highly selective and highly stable silver catalysts is the main direction of silver catalyst research. The performance of silver catalysts is not only closely related to the composition and preparation method of the catalyst, but also closely related to the performance and preparation of the carrier used in the catalyst.

[0004] At present, the silver catalysts on the market either have good selectivity but poor activity, or have good activity but poor selectivity. Therefore, in view of the market demand, it is necessary to research and develop a carrier processing technology that can improve the activity and stability of silver catalysts and the selectivity of silver catalysts, as well as a silver catalyst made from the carrier and an application method thereof.

[0005] Based on this background, the present invention studies and develops a modified α-alumina carrier and a preparation method thereof, a silver catalyst and an application thereof. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a modified α-alumina carrier and a preparation method thereof, a silver catalyst and an application thereof, wherein the carrier has a high specific surface area and strength and has a large number of macropores. The silver catalyst made of the modified α-alumina is conducive to the dispersion of the reaction active centers, improves the catalytic performance of the active centers, and is conducive to the desorption of the product. Therefore, the modified alumina carrier is applied to the reaction process of producing ethylene oxide by ethylene oxidation, which improves its activity and selectivity, especially significantly improves the selectivity.

[0007] The first aspect of the present invention provides a modified α-alumina carrier, wherein the modified α-alumina carrier is prepared by sequentially molding, drying, calcining, reducing, sulfiding and purging a precursor mixture thereof;

[0008] The precursor mixture comprises the following components:

[0009] Component a: α-A1 trihydrate 2 O 3 , its content based on the total weight of components a to g is 5 to 90 wt%;

[0010] Component b: Pseudomonohydrate A1 2 O 3 , its content based on the total weight of components a to g is 5-70wt.%;

[0011] Component c: a heavy alkaline earth metal compound, the content of which is 0-1.5 wt.% based on the total weight of components a-g;

[0012] Component d: a mineralizer, whose content is 0.1 to 3.0 wt.% based on the total weight of components a to g;

[0013] Component e: copper and / or copper-containing compounds, the content of which is 0.01-1.0 wt.% based on the total weight of components a to g;

[0014] Component f: tungsten element and / or tungsten-containing compound, the content of which is 0.01-5.0 wt.% based on the total weight of components a-g;

[0015] Component g: a binder, whose content is 2-60 wt.% based on the total weight of components a to g;

[0016] Component h: optional water.

[0017] The second aspect of the present invention provides a method for preparing the modified α-alumina carrier, the method comprising the following steps:

[0018] S1: Sanshui A1 2 O 3 , fake water A1 2 O 3 , an optional heavy alkaline earth metal compound, copper and / or a copper-containing compound, tungsten and / or a tungsten-containing compound, and a binder are mixed to prepare a precursor mixture;

[0019] S2: molding, drying and calcining the precursor mixture in sequence to obtain an α-alumina carrier containing copper and tungsten;

[0020] S3: reducing, sulfiding and purging the α-alumina carrier containing copper and tungsten in sequence to obtain a modified α-alumina carrier

[0021] The third aspect of the present invention provides a silver catalyst, which is prepared by impregnating the modified α-alumina carrier with an impregnation liquid and then subjecting the impregnation liquid to solid-liquid separation.

[0022] The fourth aspect of the present invention provides a use of the above-mentioned silver catalyst in the production of ethylene oxide by oxidation of ethylene.

[0023] The beneficial technical effects of the present invention are as follows: the present invention proposes a modified α-alumina carrier and a preparation method thereof, a silver catalyst and an application thereof, wherein the carrier has a high specific surface area and strength, and has a large number of macropores; the modified α-alumina carrier is obtained by adding copper and tungsten elements during the carrier preparation process and performing reduction and sulfidation treatment on the formed α-alumina carrier for modification; the silver catalyst made of the modified α-alumina is beneficial to the dispersion of the reaction active centers, improves the catalytic performance of the active centers, and is beneficial to the desorption of the product. Therefore, the modified alumina carrier is applied to the reaction process of ethylene oxidation to produce ethylene oxide, which improves its activity and selectivity, especially significantly improves the selectivity. The raw materials for preparing the modified α-alumina carrier of the present invention are easy to obtain, and the preparation method has simple steps. The modified α-alumina carrier and the silver catalyst provided by the present invention have broad application prospects.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0025] 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.

[0026] The present invention provides a modified α-alumina carrier, which is prepared by sequentially molding, drying, calcining, reducing, sulfiding and purging a precursor mixture thereof;

[0027] The precursor mixture includes the following components:

[0028] Component a: α-A1 trihydrate 2 O 3 , its content based on the total weight of components a to g is 5 to 90 wt%;

[0029] Component b: Pseudomonohydrate A1 2 O 3 , its content based on the total weight of components a to g is 5-70wt.%;

[0030] Component c: a heavy alkaline earth metal compound, the content of which is 0-1.5 wt.% based on the total weight of components a-g;

[0031] Component d: a mineralizer, whose content is 0.1 to 3.0 wt.% based on the total weight of components a to g;

[0032] Component e: copper and / or copper-containing compounds, the content of which is 0.01-1.0 wt.% based on the total weight of components a to g;

[0033] Component f: tungsten element and / or tungsten-containing compound, the content of which is 0.01-5.0 wt.% based on the total weight of components a-g;

[0034] Component g: a binder, whose content is 2-60 wt.% based on the total weight of components a to g;

[0035] Component h: optional water.

[0036] Preferably, the content of component a based on the total weight of components a to g is 6-80wt.%; the content of component b based on the total weight of components a to g is 6-60wt.%; the content of component c based on the total weight of components a to g is 0-1.0wt.%; the content of component d based on the total weight of components a to g is 0.5-2.0wt.%; the content of component e based on the total weight of components a to g is 0.05-0.5wt.%; the content of component f based on the total weight of components a to g is 0.5-3.5wt.%; the content of component g based on the total weight of components a to g is 15-40wt.%.

[0037] According to the present invention, the heavy alkaline earth metal compound is a compound of strontium and / or barium, preferably at least one of oxides, sulfates, nitrates, carbonates and oxalates of strontium and / or barium, and more preferably at least one of barium oxide, barium sulfate, barium nitrate and barium carbonate;

[0038] The mineralizer is selected from at least one of hydrogen fluoride, ammonium fluoride, aluminum fluoride, magnesium fluoride and cryolite, preferably ammonium fluoride.

[0039] According to the present invention, the copper-containing compound is selected from at least one of copper oxide, copper carbonate, copper nitrate, copper chloride and copper sulfate, preferably copper oxide and / or copper nitrate;

[0040] The tungsten-containing compound is at least one of tungsten oxide, ammonium tungstate and ammonium metatungstate, and preferably ammonium metatungstate.

[0041] According to the present invention, the binder is an aqueous solution of an acid;

[0042] The acid is selected from at least one of nitric acid, formic acid, acetic acid, propionic acid and hydrochloric acid, preferably nitric acid.

[0043] The weight ratio of acid to water in the acid aqueous solution is 1:1.25-10, preferably 1:1.5-6.

[0044] In the present invention, component g binder can be combined with component b pseudo monohydrate Al 2 O 3Aluminum sol is generated to bond the components together to form a paste that can be extruded.

[0045] In the present invention, aluminum sol can also be used to partially or completely replace the binder of component h and the pseudo-monohydrate Al2O3 of component b. 2 O 3 .

[0046] According to the present invention, the molded shape is any regular or irregular shape, preferably at least one of an annular shape, a spherical shape, a cylindrical shape, and a porous cylindrical shape;

[0047] The drying temperature is 80-120°C and the drying time is 1-24h;

[0048] The calcination temperature is 1000-1500°C, preferably 1000-1400°C; the calcination time is not less than 1 hour, preferably 2-24 hours, and more preferably 2-8 hours;

[0049] The reduction temperature is 300-600°C, preferably 400-500°C, the time is 0.2-10h, preferably 3-6h, the reducing gas used is hydrogen and / or methane, preferably hydrogen, and the space velocity of the reducing gas is 1-1000h -1 , preferably 200-600h -1 ;

[0050] The sulfurization method is to introduce organic sulfur into the reducing gas after the reduction is completed, preferably carbon disulfide and / or thioether; the concentration of organic sulfur is 10-500ppm, preferably 50-200ppm; the sulfurization time is 0.2-10h, preferably 3-6h, and the temperature is 20-300°C, preferably 20-200°C;

[0051] The purging gas is nitrogen and / or air, preferably nitrogen is used first, and then air is added to the nitrogen to purge until it is completely converted to air purging; the purging time is 0.2-24h, preferably 10-20h;

[0052] The rate of addition of air in nitrogen was 8-12 v.% / h.

[0053] Preferably, the modified α-alumina carrier has a specific surface area of ​​0.2-2.0 m 2 / g, pore volume is 0.35-0.85mL / g, water absorption rate is not less than 30%, and crushing strength is 20-140N / grain.

[0054] In the present invention, the modified α-alumina carrier has a higher specific surface area and strength and has more macropores.

[0055] In the present invention, component a is trihydrate A1 2 O 3, and is granular trihydrate A1 2 O 3 , its particle size is 50-500 mesh. 2 O 3 The presence of can increase the pores of the carrier, thereby forming a porous α-A1 2 O 3 carrier.

[0056] In the present invention, component b is pseudo-monohydrate A1 2 O 3 , and its particle size is preferably greater than or equal to 200 mesh.

[0057] In the present invention, component c is a heavy alkaline earth metal compound, which can improve the performance of the carrier.

[0058] In the present invention, the addition of fluoride mineralizer is to accelerate the 2 O 3 crystalline transformation.

[0059] The modified α-alumina carrier of the present invention is prepared by a method comprising the following steps:

[0060] S1: Sanshui A1 2 O 3 , fake water A1 2 O 3 , an optional heavy alkaline earth metal compound, copper and / or a copper-containing compound, tungsten and / or a tungsten-containing compound, and a binder are mixed to prepare a precursor mixture;

[0061] S2: molding, drying and calcining the precursor mixture in sequence to obtain an α-alumina carrier containing copper and tungsten;

[0062] S3: The α-alumina carrier containing copper and tungsten is reduced, sulfided and purged in sequence to obtain a modified α-alumina carrier.

[0063] According to the present invention, the preparation method further comprises the steps of:

[0064] S4: activating the modified α-alumina carrier to obtain an activated modified α-alumina carrier;

[0065] The activation atmosphere is air or nitrogen-oxygen mixed gas, and the oxygen content in the nitrogen-oxygen mixed gas is not more than 21v.%;

[0066] The activation temperature is 180-700° C., preferably 200-500° C., and the activation time is 1-120 min, preferably 2-60 min.

[0067] In the present invention, the precursor mixture is molded and dried in sequence, and the water content is below 10 wt.%.

[0068] In the present invention, the modified α-alumina carrier is a porous alumina carrier containing copper and tungsten which has been treated by a reduction and sulfidation step, and since the copper and tungsten elements contained in the modified alumina carrier are added in a manner of being mixed with other components during its preparation process, the copper and tungsten elements in the modified alumina carrier are uniformly distributed. The addition of copper and tungsten elements is conducive to forming a synergistic active center with the active component silver and improving the catalytic performance, and the treatment of the reduction and sulfidation steps ensures that the copper and tungsten additives are stably present in a low-valent state.

[0069] The present invention also provides a silver catalyst, which is prepared by impregnating the modified α-alumina carrier with an impregnation liquid and then performing solid-liquid separation;

[0070] The impregnation solution includes the following components by weight:

[0071] The content of silver compound is 1%-40%; the content of alkali metal auxiliary agent is 5-2000ppm; the content of alkaline earth metal auxiliary agent is 0-10000ppm; the content of rhenium auxiliary agent is 10-2000ppm; the content of organic amine compound is 1-24%; and the balance is water.

[0072] According to the present invention, the silver compound is at least one of silver oxide, silver nitrate and silver oxalate;

[0073] The alkali metal auxiliary agent is at least one of lithium, sodium, potassium, rubidium and cesium compounds, preferably at least one of cesium sulfate, cesium nitrate, lithium nitrate and potassium hydroxide;

[0074] The alkaline earth metal additive is at least one of a compound of magnesium, calcium, strontium and barium; preferably at least one of an oxide, oxalate, sulfate, acetate and nitrate of magnesium, calcium, strontium and barium;

[0075] The rhenium additive is at least one of rhenium oxide, perrhenic acid, cesium perrhenate and ammonium perrhenate;

[0076] The organic amine is at least one of pyridine, butylamine, ethylenediamine, 1,3-propylenediamine and ethanolamine, preferably ethylenediamine and / or ethanolamine;

[0077] The immersion pressure is no greater than normal pressure, and the time is 10-60 minutes;

[0078] Solid-liquid separation is leaching;

[0079] The content of silver in the silver catalyst is 15-18 wt.%.

[0080] In the present invention, the silver catalyst made of modified α-alumina is conducive to the dispersion of the reaction active center, improves the catalytic performance of the active center, and is conducive to the desorption of the product. Therefore, the modified alumina carrier is applied to the reaction process of ethylene oxidation to produce ethylene oxide, which improves its activity and selectivity, especially significantly improves the selectivity.

[0081] The present invention also provides an application of the silver catalyst in producing ethylene oxide by ethylene oxidation.

[0082] In the present invention, the above silver catalyst is used in the ethylene epoxidation reaction, and the epoxidation reaction conditions are the reaction conditions commonly used in the art, such as the reaction temperature can be 200-275°C.

[0083] The term "optionally" used in the present invention means containing or not containing, and also means adding or not adding.

[0084] The term "water" in the present invention, unless otherwise specified or explained, refers to at least one of deionized water, distilled water and ultrapure water.

[0085] The term "rhenium co-builder" used in the present invention is also referred to as "rhenium co-builder" or "rhenium synergist".

[0086] The molecular formula of the term "aluminum oxide" in the present invention is Al 2 O 3 .

[0087] The present invention is further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0088] In the present invention, the specific surface area of ​​the carrier is measured by nitrogen physical adsorption BET method according to international test standard ISO-9277. For example, the specific surface area of ​​the carrier can be measured using NOVA2000e nitrogen physical adsorption instrument produced by Quantachrome Corporation of the United States.

[0089] The pore volume of the carrier is measured by mercury intrusion. For example, the pore volume of the carrier can be measured by using an Auto Pore 9510 mercury intrusion instrument produced by Micromeritics, Inc., USA.

[0090] The amount of the alkaline earth metal compound in the carrier can be obtained by calculation.

[0091] The lateral compression strength of the carrier can be obtained, for example, by using a DLII intelligent particle strength tester produced by Dalian Chemical Research and Design Institute, randomly selecting 30 carrier samples, measuring the radial crushing strength and then taking the average value.

[0092] The term "water absorption rate" used here refers to the volume of saturated water adsorbed by a unit mass of a carrier, and the unit is mL / g. The determination method is as follows: first weigh a certain amount of carrier (assuming its mass is m1), boil it in boiling water for 1 hour, take out the carrier and place it upright on wet gauze with moderate water content to remove excess water on the surface of the carrier, and finally weigh the mass of the carrier after adsorbing water (assuming it is m2), and calculate the water absorption rate of the carrier according to the following formula.

[0093] Water absorption rate = (m2-m1) / m1 / ρwater

[0094] where ρwater is the density of water at the test temperature and atmospheric pressure.

[0095] Determination of catalyst performance: The various silver catalysts involved in the present invention are tested for their initial activity and selectivity using a laboratory microreactor (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 reaction tube is placed in a heating jacket. The filling volume of the catalyst 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. The determination conditions of the catalyst activity and selectivity used in the present invention are shown in Table 1:

[0096] The activity and selectivity test conditions used in the present invention are shown in Table 1:

[0097] Table 1 Determination conditions of catalyst activity and selectivity

[0098]

[0099] 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:

[0100]

[0101] Where ΔEO is the difference in ethylene oxide concentration between the outlet gas and the 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.

[0102] In the following examples, Examples 1-4 are α-alumina carrier examples, Comparative Examples 1-3 are α-alumina carrier comparative examples, Examples 5-8 are silver catalyst examples, and Comparative Examples 4-6 are silver catalyst comparative examples.

[0103] Comparative Example 1

[0104] 200-500 mesh α-Al trihydrate 2 O 3 372g, 200-400 mesh pseudo monohydrate Al 2 O 3112g, MgF 2 3g and Ba(NO 3 ) 2 0.5g of the solid mixture was put into a mixer and mixed evenly, then transferred to a kneader, 90mL of dilute nitric acid was added, and kneaded into a paste that could be extruded and formed into a five-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm. The five-hole column was dried at 80-120°C for 10h to reduce the free water content to less than 10% (by weight), and a molded α-alumina carrier precursor was obtained. The precursor was then placed in an electric furnace, and the temperature was raised from room temperature to 1400°C over 30h, and then kept at a constant temperature for 2h to obtain a white α-Al 2 O 3 The prepared white α-Al 2 O 3 The vector was named Z-1.

[0105] Comparative Example 2

[0106] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 14.87g, the rest is the same as in Comparative Example 1, to obtain α-Al containing copper and tungsten 2 O 3 The vector was named Z-2.

[0107] Comparative Example 3

[0108] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 The obtained α-Al2O3 carrier containing copper and tungsten was then heated at 500°C in a hydrogen atmosphere at a space velocity of 500 h -1 , reduced for 6 hours, and the reduced modified α-Al containing copper and tungsten was obtained. 2 O 3 The vector was named Z-3.

[0109] Example 1

[0110] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 14.87g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is at 500℃, in a hydrogen atmosphere, and its space velocity is 500h -1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 60°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with dimethyl disulfide, and then the carrier is sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 200ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge, and the air ratio increases by 10% every hour. After 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified α-Al containing copper and tungsten 2 O 3 The vector was named Z-4.

[0111] Example 2

[0112] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 14.87g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is heated at 400°C in a hydrogen atmosphere with a space velocity of 500 h -1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 60°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with dimethyl disulfide. The carrier is then sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 100 ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge. The air ratio increases by 10% every hour, and after 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified αAl containing copper and tungsten. 2 O 3 The vector was named Z-5.

[0113] Example 3

[0114] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 1214.87g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is at 500℃, in a hydrogen atmosphere, and its space velocity is 500h -1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 60°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with carbon disulfide. The carrier is then sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 200ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge. The air ratio increases by 10% every hour, and after 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified α-Al containing copper and tungsten. 2 O 3 The vector was named Z-6.

[0115] Example 4

[0116] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 14.87g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is at 500℃, in a hydrogen atmosphere, and its space velocity is 500h -1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 200°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with dimethyl disulfide. The carrier is then sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 200ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge. The air ratio increases by 10% every hour, and after 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified α-Al containing copper and tungsten. 2 O 3 The vector was named Z-7.

[0117] Example 5

[0118] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 0.61g and ammonium metatungstate H 28 N 6 O 41 W 12 14.87g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is at 500℃, in a hydrogen atmosphere, and its space velocity is 500h-1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 60°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with carbon disulfide. The carrier is then sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 200ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge. The air ratio increases by 10% every hour, and after 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified α-Al containing copper and tungsten. 2 O 3 The vector was named Z-8.

[0119] Example 6

[0120] The raw materials mixed in the mixer also include Cu(NO 3 ) 2 ·3H 2 O 1.21g and ammonium metatungstate H 28 N 6 O 41 W 12 7.44g, and the rest is the same as Comparative Example 1. Then the prepared α-Al containing copper and tungsten 2 O 3 The carrier is at 500℃, in a hydrogen atmosphere, and its space velocity is 500h -1 , reduction for 6 hours; after the reduction is completed, the temperature is lowered to 60°C, and a hydrogen gas flow is introduced into a stainless steel tank filled with carbon disulfide. The carrier is then sulfurized for 2 hours with a hydrogen gas flow containing organic sulfur, and the concentration of organic sulfur is 200ppm. After the sulfurization is completed, it is switched to nitrogen purge for 5 hours, and then mixed with air purge. The air ratio increases by 10% every hour, and after 10 hours, it is completely converted to air to obtain a reduction-sulfurized modified α-Al containing copper and tungsten. 2 O 3 The vector was named Z-9.

[0121] Preparation of the corresponding silver catalysts in Comparative Examples 1-3 and Examples 1-6

[0122] 300 g of butylamine, 110 g of 1,3-propylenediamine and 375 g of deionized water were added to a stirred glass flask to obtain a mixed solution. 650 g of silver oxalate was slowly added to the mixed solution under stirring to dissolve all the silver oxalate, and then 3.2 g of potassium nitrate and 2.1 g of calcium nitrate were added, and deionized water was added to make the total mass of the solution reach 2000 g. The obtained solution was mixed evenly to obtain a silver catalyst impregnation solution, and the silver content of the obtained silver compound impregnation solution was 22 wt.%.

[0123] Take 15g of each carrier sample prepared in Comparative Examples 1-3 and Examples 1-6, place them in vacuum containers, evacuate to a certain degree of vacuum, add the above silver catalyst impregnation solution, immerse the carrier, and keep it for 30 minutes. Then, remove the excess silver catalyst impregnation solution by leaching, heat the impregnated carrier in an air flow at 350°C for 5 minutes, and cool it to prepare the corresponding silver catalysts of Comparative Examples 1-3 and Examples 1-6. The prepared silver catalysts are named CZ-1 to CZ-9.

[0124] Test Example 1

[0125] The contents of silver and auxiliary agents in the prepared silver catalysts were analyzed, where all contents were calculated as metals. The contents of silver and auxiliary agents in CZ-1 to CZ-9 were basically the same, where the content of silver element was about 16.1 wt.%.

[0126] Test Example 2

[0127] The activity and selectivity of silver and additives in CZ-1 to CZ-9 were determined using a microreactor evaluation device. The temperature and selectivity data on the 8th day of the reaction are listed in Table 2.

[0128] Table 2 Physical properties of catalysts

[0129] Catalyst source catalyst Initial reaction temperature (℃) EO(mol%) Selectivity (%) Comparative Example 1 CZ-1 236.2 2.51 81.02 Comparative Example 2 CZ-2 233.5 2.50 82.57 Comparative Example 3 CZ-3 232.1 2.50 83.23 Example 1 CZ-4 223.9 2.50 88.65 Example 2 CZ-5 227.4 2.51 87.87 Example 3 CZ-6 225.8 2.50 87.77 Example 4 CZ-7 226.0 2.51 87.19 Example 5 CZ-8 226.9 2.51 87.10 Example 6 CZ-9 227.9 2.49 87.89

[0130] It can be seen from the data in Table 2 that the reduced and sulfurized α-Al2O3 containing copper and tungsten provided by the present invention is 2 O 3 The silver catalyst made of the carrier is used in the process of ethylene oxidation to produce ethylene oxide, which is beneficial to the dispersion of the reaction active center and improves the catalytic performance of the active center. Compared with the catalysts CZ-1-CZ-3 prepared from the carriers in Comparative Examples 1-3 (containing no copper and tungsten elements and containing copper and tungsten zinc elements but not treated by reduction and sulfurization steps), the catalyst selectivity and activity are significantly improved compared with the catalysts CZ-4-CZ-9 prepared from the carriers in Examples 1-6 (containing copper and tungsten elements and treated by reduction and sulfurization steps).

[0131] 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.

[0132] 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 modified α-alumina carrier, characterized in that: The modified α-alumina carrier is prepared by sequentially molding, drying, calcining, reducing, sulfiding and purging a precursor mixture thereof; The precursor mixture comprises the following components: Component a: α-A12O3 trihydrate, the content of which is 5 to 90 wt% based on the total weight of components a to g; Component b: pseudo monohydrate A12O3, whose content is 5-70wt.% based on the total weight of components a-g; Component c: a heavy alkaline earth metal compound, the content of which is 0-1.5 wt.% based on the total weight of components a-g; Component d: a mineralizer, whose content is 0.1 to 3.0 wt.% based on the total weight of components a to g; Component e: copper and / or copper-containing compounds, the content of which is 0.01-1.0 wt.% based on the total weight of components a to g; Component f: tungsten element and / or tungsten-containing compound, the content of which is 0.01-5.0 wt.% based on the total weight of components a-g; Component g: a binder, whose content is 2-60 wt.% based on the total weight of components a to g; Component h: optional water.

2. The modified α-alumina carrier according to claim 1, characterized in that The content of component a based on the total weight of components a to g is 6-80wt.%; the content of component b based on the total weight of components a to g is 6-60wt.%; the content of component c based on the total weight of components a to g is 0-1.0wt.%; the content of component d based on the total weight of components a to g is 0.5-2.0wt.%; the content of component e based on the total weight of components a to g is 0.05-0.5wt.%; the content of component f based on the total weight of components a to g is 0.5-3.5wt.%; the content of component g based on the total weight of components a to g is 15-40wt.%.

3. The modified α-alumina carrier according to claim 1 or 2, characterized in that The heavy alkaline earth metal compound is a compound of strontium and / or barium, preferably at least one of oxides, sulfates, nitrates, carbonates and oxalates of strontium and / or barium, and more preferably at least one of barium oxide, barium sulfate, barium nitrate and barium carbonate; The mineralizer is selected from at least one of hydrogen fluoride, ammonium fluoride, aluminum fluoride, magnesium fluoride and cryolite, preferably ammonium fluoride.

4. The modified α-alumina carrier according to claim 1 or 2, characterized in that The copper-containing compound is selected from at least one of copper oxide, copper carbonate, copper nitrate, copper chloride and copper sulfate, preferably copper oxide and / or copper nitrate; The tungsten-containing compound is at least one of tungsten oxide, ammonium tungstate and ammonium metatungstate, preferably ammonium metatungstate.

5. The modified α-alumina carrier according to claim 1 or 2, characterized in that The binder is an aqueous solution of an acid; The acid is selected from at least one of nitric acid, formic acid, acetic acid, propionic acid and hydrochloric acid, preferably nitric acid.

6. The modified α-alumina carrier according to claim 5, characterized in that The weight ratio of acid to water in the acid aqueous solution is 1:1.25-10, preferably 1:1.5-6.

7. The modified α-alumina carrier according to claim 1 or 2, characterized in that The molded shape is any regular or irregular shape, preferably at least one of an annular shape, a spherical shape, a cylindrical shape, and a porous cylindrical shape; The drying temperature is 80-120°C and the drying time is 1-24h; The calcination temperature is 1000-1500°C, preferably 1000-1400°C; the calcination time is not less than 1 hour, preferably 2-24 hours, and more preferably 2-8 hours; The reduction temperature is 300-600°C, preferably 400-500°C, the time is 0.2-10h, preferably 3-6h, the reducing gas used is hydrogen and / or methane, preferably hydrogen, and the space velocity of the reducing gas is 1-1000h -1 , preferably 200-600h -1 ; The sulfurization method is to introduce organic sulfur into the reducing gas after the reduction is completed, preferably carbon disulfide and / or thioether; the concentration of the organic sulfur is 10-500ppm, preferably 50-200ppm; the sulfurization time is 0.2-10h, preferably 3-6h, and the temperature is 20-300°C, preferably 20-200°C; The purging gas is nitrogen and / or air, preferably nitrogen is used for purging first, and then air is added to the nitrogen for purging until it is completely converted to air purging; the purging time is 0.2-24h, preferably 10-20h; The rate at which the air is added to the nitrogen is 8-12 v.% / h.

8. The modified α-alumina carrier according to claim 1 or 2, characterized in that The modified α-alumina carrier has a specific surface area of ​​0.2-2.0m 2 / g, pore volume is 0.35-0.85mL / g, water absorption rate is not less than 30%, and crushing strength is 20-140N / grain.

9. A method for preparing a modified α-alumina carrier according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: mixing trihydrate Al2O3, pseudo monohydrate Al2O3, an optional heavy alkaline earth metal compound, copper element and / or a copper-containing compound, tungsten element and / or a tungsten-containing compound and a binder to prepare a precursor mixture; S2: molding, drying and calcining the precursor mixture in sequence to obtain an α-alumina carrier containing copper and tungsten; S3: reducing, sulfiding and purging the copper and tungsten-containing α-alumina carrier in sequence to obtain a modified α-alumina carrier.

10. The preparation method according to claim 9, characterized in that: The preparation method further comprises the following steps: S4: activating the modified α-alumina carrier to obtain an activated modified α-alumina carrier; The activation atmosphere is air or a nitrogen-oxygen mixture, and the oxygen content in the nitrogen-oxygen mixture is not more than 21v.%; The activation temperature is 180-700° C., preferably 200-500° C., and the activation time is 1-120 min, preferably 2-60 min.

11. A silver catalyst, characterized in that The silver catalyst is prepared by impregnating the modified α-alumina carrier according to any one of claims 1 to 8 with an impregnation solution and then performing solid-liquid separation; The impregnation solution comprises the following components by weight: The content of silver compound is 1%-40%; the content of alkali metal auxiliary agent is 5-2000ppm; the content of alkaline earth metal auxiliary agent is 0-10000ppm; the content of rhenium auxiliary agent is 10-2000ppm; the content of organic amine compound is 1-24%; and the balance is water.

12. The silver catalyst according to claim 11, characterized in that The silver compound is at least one of silver oxide, silver nitrate and silver oxalate; The alkali metal auxiliary agent is at least one of lithium, sodium, potassium, rubidium and cesium compounds, preferably at least one of cesium sulfate, cesium nitrate, lithium nitrate and potassium hydroxide; The alkaline earth metal additive is at least one of a compound of magnesium, calcium, strontium and barium; preferably at least one of an oxide, oxalate, sulfate, acetate and nitrate of magnesium, calcium, strontium and barium; The rhenium auxiliary agent is at least one of rhenium oxide, perrhenic acid, cesium perrhenate and ammonium perrhenate; The organic amine is at least one of pyridine, butylamine, ethylenediamine, 1,3-propylenediamine and ethanolamine, preferably ethylenediamine and / or ethanolamine; The immersion pressure is no greater than normal pressure, and the time is 10-60 minutes; The solid-liquid separation is leaching; The content of silver in the silver catalyst is 15-18 wt.%.

13. Use of the silver catalyst according to any one of claims 11 to 12 in producing ethylene oxide by ethylene oxidation.

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