CN112705196B - Silver-gold bimetal supported catalyst and preparation method and application thereof - Google Patents
Silver-gold bimetal supported catalyst and preparation method and application thereof Download PDFInfo
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- CN112705196B CN112705196B CN201911017950.4A CN201911017950A CN112705196B CN 112705196 B CN112705196 B CN 112705196B CN 201911017950 A CN201911017950 A CN 201911017950A CN 112705196 B CN112705196 B CN 112705196B
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/48—Silver or gold
- B01J23/52—Gold
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D301/00—Preparation of oxiranes
- C07D301/02—Synthesis of the oxirane ring
- C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
- C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
- C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
- C07D301/10—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
- C07D303/02—Compounds containing oxirane rings
- C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention belongs to the field of olefin epoxidation reaction, and relates to a silver-gold bimetallic supported catalyst, and a preparation method and application thereof. The catalyst comprises an alpha-alumina carrier and silver and gold loaded on the carrier, wherein the content of the silver is 5-25wt% calculated by elements, and the content of the gold is 50-2000ppmw calculated by elements. The catalyst of the invention has higher activity, selectivity and stability in the ethylene epoxidation reaction, and particularly has better catalytic activity and stability in the ethylene epoxidation reaction under the condition of containing 0.5-10 wt% of water vapor.
Description
Technical Field
The invention belongs to the field of olefin epoxidation, and particularly relates to a silver-gold bimetallic supported catalyst and a preparation method thereof, the silver-gold bimetallic supported catalyst prepared by the method, and application of the silver-gold bimetallic supported catalyst in ethylene epoxidation.
Background
Under the action of the silver catalyst, ethylene is oxidized to mainly generate ethylene oxide, and byproducts of carbon dioxide, water and the like are generated at the same time, wherein the activity, the selectivity and the stability are main performance indexes of the silver catalyst. The activity refers to the reaction temperature required when the ethylene oxide production process reaches a certain reaction load, and the lower the reaction temperature is, the higher the activity of the catalyst is; selectivity refers to the ratio of moles of ethylene converted to ethylene oxide in the reaction to the total reacted moles of ethylene; stability is expressed as the rate of decline of activity and selectivity, the smaller the rate of decline, the better the stability of the catalyst. The silver catalyst with high activity, high selectivity and good stability is used in the process of producing ethylene oxide by oxidizing ethylene, so that the economic benefit can be greatly improved, and the preparation of the silver catalyst with high activity, high selectivity and good stability is the main direction of research on the silver catalyst.
Currently, industrial silver catalysts all use alpha-alumina supported silver monometal, and the preparation method comprises two processes of preparing alumina and applying active components and auxiliary agents to the carrier.
The conventional method of applying the active component silver and the auxiliary agent to the carrier is mainly a dip-reduction method, i.e., the carrier is first dipped with a solution containing a silver salt, an organic amine and various auxiliary agents, and then the dipped carrier is subjected to an activation treatment in a heat medium to reduce the silver salt to the active component silver and decompose an excessive reducing agent.
The disclosed patents mostly describe single metal silver catalysts, and few double metal alloy catalysts are used for preparing silver catalysts, but some double metal alloy catalysts can have excellent catalytic performance, for example, CN201310090699.0 uses silver-palladium double metal silver catalysts to show better catalytic selectivity under normal pressure reaction conditions.
Other methods of activating atmospheres have been reported, including air, oxygen-containing mixtures and inert atmospheres, with activation temperatures in the broad range of 100-950 ℃. EP0038446A uses a stepwise temperature rise process to decompose silver compounds into the active component silver; US5602070A believes that treating the catalyst in an inert atmosphere at no more than 300 ℃ is beneficial in improving the performance of the catalyst.
The above patent documents have a limited effect of improving the activity of the silver catalyst, and have an insignificant effect of improving the selectivity and a significant effect on the stability.
In addition, in industrial production, the recycle gas from ethylene oxide production plants contains a certain amount of water vapour (0.2-0.5%), but some plants may have a water content of up to 5% in some cases. The silver catalyst has better catalytic activity and stability under the condition of normal water content (0.2-0.5%), but when the water content in the circulating gas reaches more than 2.0%, the activity and the selectivity of the catalyst are reduced to different degrees, and the service life of the catalyst can be shortened under severe conditions.
Therefore, there is still a need to develop a method for improving the activity and selectivity of silver catalyst to a greater extent, especially for silver-containing catalyst with excellent catalytic performance under high water content.
Disclosure of Invention
The invention aims to provide a novel silver-gold bimetallic supported catalyst and a preparation method thereof, wherein the catalyst has higher activity, selectivity and stability.
In a first aspect, the present invention provides a silver-gold bimetallic supported catalyst comprising an α -alumina support and silver and gold supported thereon, wherein the silver content is in the range of 5 to 25wt% calculated as element and the gold content is in the range of 50 to 2000ppmw calculated as element, based on the weight of the catalyst.
The second aspect of the present invention provides a method for preparing the silver-gold bimetallic supported catalyst, which comprises: the silver compound and the gold compound are simultaneously impregnated on the support, and thereafter, reduction by firing is performed.
The third aspect of the present invention provides a silver-gold bimetallic supported catalyst prepared by the above preparation method.
The fourth aspect of the present invention provides the use of the silver-gold bimetallic supported catalyst in the epoxidation of ethylene.
The catalyst of the invention has higher activity, selectivity and stability in ethylene epoxidation reaction, and particularly has better catalytic activity and stability in ethylene epoxidation reaction under the condition of containing 0.5-10 wt% of water vapor.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes the embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The invention provides a silver-gold bimetallic supported catalyst, which comprises an alpha-alumina carrier and silver and gold loaded on the alpha-alumina carrier, wherein the content of the silver is 5-25wt% calculated by elements, preferably 15-25wt% calculated by the weight of the catalyst, and the content of the gold is 50-2000ppmw calculated by elements, preferably 200-1000ppmw calculated by the elements.
The silver-gold bimetallic supported catalyst can be prepared by a method comprising the following steps: the silver compound and the gold compound are simultaneously impregnated on the support, and thereafter, reduction by firing is performed.
According to a preferred embodiment of the present invention, the catalyst is prepared by a process comprising the steps of:
(1) Impregnating an alpha-alumina carrier with an impregnating solution containing a silver compound, a gold reducing agent, organic amine, an alkali metal assistant, a rhenium-containing assistant and an optional rhenium co-assistant;
(2) Filtering to remove the maceration extract;
(3) The impregnated support is subjected to an activating thermal decomposition, preferably in a reducing atmosphere.
The invention also provides a preparation method of the silver-gold bimetal supported catalyst, which comprises the following steps: the silver compound and the gold compound are simultaneously impregnated on the support, and thereafter, reduction by firing is performed.
Preferably, the method comprises the steps of:
(1) Dipping an alpha-alumina carrier by using a dipping solution containing a silver compound, a gold reducing agent, organic amine, an alkali metal auxiliary agent, a rhenium-containing auxiliary agent and an optional rhenium co-auxiliary agent;
(2) Filtering to remove the maceration extract;
(3) The impregnated support is subjected to an activating thermal decomposition, preferably in a reducing atmosphere.
According to the invention, in step (1), the silver compound is silver oxide and/or silver salt, such as silver nitrate, silver carbonate and the like, preferably silver carbonate.
According to the invention, in step (1), the gold compound is chloroauric acid and/or a gold salt, such as gold hydroxide, gold chloride, gold cyanide and the like, preferably chloroauric acid.
According to the present invention, in the step (1), the gold reducing agent may be various gold reducing substances conventional in the art, and may be at least one selected from oxalic acid, formaldehyde, glucose and ascorbic acid; preferably ascorbic acid and/or glucose.
The selection of the other components in step (1) according to the present invention may be any conventional choice in the art.
According to the present invention, in step (1), the organic amine may be any organic amine compound suitable for preparing a silver catalyst for ethylene oxide production, as long as the organic amine compound is capable of forming a silver amine complex with a silver compound. For example, the organic amine is selected from at least one of pyridine, butylamine, ethylenediamine, 1, 3-propanediamine, ethanolamine, and triethylamine, and preferably the organic amine is ethylenediamine and/or ethanolamine.
The alkali metal promoter may be selected from at least one of lithium, sodium, potassium, rubidium, and cesium. The content of the alkali metal element is usually 0 to 5000ppm, preferably 5 to 3500ppm, based on the total weight of the catalyst.
The rhenium-containing promoter may be selected from elemental rhenium, at least one of rhenium oxide, perrhenic acid and perrhenate, preferably from perrhenic acid and/or perrhenate, and more preferably from at least one of perrhenic acid, cesium perrhenate and ammonium perrhenate. The rhenium element content of the finally obtained catalyst is generally from 5 to 3500ppm, preferably from 10 to 2500ppm, based on the total weight of the catalyst.
The rhenium co-additive can be at least one of a chromium simple substance, a molybdenum simple substance, a tungsten simple substance, a boron simple substance, a chromium metal compound, a molybdenum metal compound, a tungsten metal compound and a boron compound. The rhenium cobuilders are generally present in the finally prepared catalysts in amounts of from 0 to 3500ppm, based on the total weight of the catalyst.
According to the invention, in step (3), the reducing atmosphere is in the presence of at least one of the following gases: ethylene, hydrogen, carbon monoxide and nitrous oxide gases. Preferably 20% to 80% ethylene or nitrous oxide gas, more preferably nitrous oxide gas.
According to the invention, in step (3), the activation is aimed at subjecting the product to thermal decomposition. The activation thermal decomposition is carried out under the surrounding of reducing gas, the temperature of the activation thermal decomposition can be 150-450 ℃, preferably 200-400 ℃, and the time of the activation thermal decomposition can be 10-300 minutes, preferably 3-60 minutes.
According to a more specific embodiment of the present invention, the catalyst is prepared by the following method:
firstly, dissolving silver carbonate aqueous solution into organic amine aqueous solution, adding chloroauric acid and/or gold salt, gold reducing agent (glucose, etc.), and then adding the above-mentioned other auxiliary agents (alkali metal auxiliary agent, rhenium metal auxiliary agent and optional rhenium co-adjuvant) to prepare impregnation mixed solution. Then, the α -alumina support is impregnated with the impregnation mixed solution, drained, and activated in a reducing atmosphere to be thermally decomposed.
In the present invention, the amount of the silver compound used in the impregnation process is such that the content of silver element in the finally prepared catalyst is 5 to 25wt% based on the total weight of the catalyst. The amount of gold compound used during impregnation is such that the gold element content in the finally obtained catalyst is from 50 to 2000ppmw, preferably from 200 to 1000ppmw, based on the total weight of the catalyst.
The invention also provides the silver-gold bimetallic supported catalyst prepared by the preparation method.
The silver-gold bimetallic supported catalyst is particularly suitable for ethylene epoxidation reaction. In particular, the catalyst of the invention is particularly suitable for the ethylene oxidation process to produce ethylene oxide under the condition of containing 0.5 to 10 percent of water vapor, preferably 2.5 to 8 percent of water vapor, and can show good activity and selectivity.
The term "optional" or "optionally" as used herein means either with or without, and with or without the addition of.
The term "water" as used herein refers to one or more of deionized water, distilled water and ultrapure water, unless otherwise specified or indicated.
The term "rhenium co-promoter" as used in the present invention is also referred to as "rhenium co-promoter" or rhenium co-promoter.
The present invention will be described in detail below by way of examples.
Various catalysts involved in the present invention were tested for their initial activity and selectivity using a laboratory microreactor (hereinafter referred to as "microreaction") evaluation device. The reactor used in the microreaction evaluation apparatus was a stainless steel tube having an inner diameter of 4mm, and the reaction tube was placed in a heating mantle. The filling volume of the catalyst is 1mL, and the lower part of the catalyst is provided with an inert filler, so that a catalyst bed layer is positioned in a constant temperature area of a heating sleeve.
The measurement conditions for the activity and selectivity of the catalyst used in the present invention are shown in table 1:
TABLE 1 determination of catalyst Activity and selectivity
When the reaction conditions are stably achieved, the gas composition at the inlet and outlet of the reactor is continuously measured. The measurement results were corrected for volume shrinkage and the selectivity S was calculated as follows:
where Δ EO is the difference in ethylene oxide concentration between the reactor outlet gas and the inlet gas, Δ CO 2 The carbon dioxide concentration difference between the outlet gas and the inlet gas of the reactor is obtained, and the average of more than 10 groups of test data is taken as the test result of the same day.
Comparative example 1
7.0g of silver nitrate was dissolved in 7mL of deionized water. 3.2g of ammonium oxalate was dissolved in 5mL of 50 ℃ deionized water. The two solutions were mixed under vigorous stirring to form a white silver oxalate precipitate. Aging for more than 30 minutes, filtering, washing the precipitate with deionized water until nitrate ions are removed to obtain a silver oxalate paste containing about 60wt% silver and about 15wt% water.
A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The prepared silver oxalate paste was slowly added to the mixed solution with stirring, the temperature was kept below 45 ℃ to completely dissolve the silver oxalate, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, thereby preparing an impregnation mixed solution. The addition amount of the silver oxalate ensures that the impregnation mixed liquor contains 20 to 25 weight percent of silver.
4g of an alpha-alumina particle carrier (specific surface area 1.0 m) was taken 2 Per g, pore volume 0.5ml/g (mercury intrusion) into a vessel capable of being evacuated. Vacuumizing to the vacuum degree of more than 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, immersing the carrier and keeping for 30min. The excess solution is leached away. And heating the impregnated carrier in air flow at 210 ℃ for 30min, and cooling to obtain the silver catalyst.
Comparative example 2
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture with stirring, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare an impregnation mixture. The addition amount of the silver carbonate ensures that the dipping mixed solution contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier used in comparative example 1 (specific surface area 1.0 m) 2 G, pore volume 0.5 ml/g) is put in the suction cupIn a vacuum vessel. Vacuumizing to vacuum degree above 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, and immersing the carrier and keeping for 30min. The excess solution is leached away. And heating the impregnated carrier in air flow at 210 ℃ for 30min, and cooling to prepare the silver-gold bimetallic supported catalyst.
Example 1
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture with stirring, and 0.06g of chloroauric acid was added, followed by 1.0g of glucose, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare a dipping mixture. The addition amount of the silver carbonate ensures that the impregnation mixed liquor contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier used in comparative example 1 (specific surface area 1.0 m) 2 Per gram, pore volume 0.5 ml/g) into a vessel capable of being evacuated. Vacuumizing to the vacuum degree of more than 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, immersing the carrier and keeping for 30min. The excess solution is leached away. And heating the impregnated carrier in air flow at 210 ℃ for 30min, and cooling to prepare the silver-gold bimetallic supported catalyst.
Example 2
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture with stirring, 0.06g of gold hydroxide was added, followed by 1.0g of oxalic acid, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare an impregnation mixture. The addition amount of the silver carbonate ensures that the impregnation mixed liquor contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier (specific surface area 1.0 m) used in comparative example 1 was added 2 Per gram, pore volume 0.5 ml/g) into a vessel capable of being evacuated. A silver-gold bimetallic supported catalyst was prepared according to the method of example 1.
Example 3
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture with stirring, and 0.06g of chloroauric acid was added, followed by 1.0g of glucose, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare an impregnation mixture. The addition amount of the silver carbonate ensures that the dipping mixed solution contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier used in comparative example 1 (specific surface area 1.0 m) 2 G, pore volume 0.5 ml/g) into a vessel capable of being evacuated. Vacuumizing to the vacuum degree of more than 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, immersing the carrier and keeping for 30min. The excess solution is leached away. The impregnated carrier is heated for 30min in a gas flow of 45 percent of ethylene and 55 percent of nitrogen at the temperature of 320 ℃ and cooled to prepare the silver-gold bimetal supported catalyst.
Example 4
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture under stirring, 0.06g of chloroauric acid was added, followed by 1.0g of glucose, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare a dipping mixture. The addition amount of the silver carbonate ensures that the dipping mixed solution contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier (specific surface area 1.0 m) used in comparative example 1 was added 2 G, pore volume 0.5 ml/g) into a vessel capable of being evacuated. Vacuumizing to vacuum degree above 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, and immersing the carrier and keeping for 30min. The excess solution is leached away. And heating the impregnated carrier in nitrous oxide gas flow at 350 ℃ for 30min, and cooling to obtain the silver-gold bimetallic catalyst.
Example 5
6.0g of silver carbonate was dissolved in deionized water to prepare a solution containing 35wt% silver. A stirred glass flask was charged with 3g of ethylenediamine and 5g of deionized water. The resulting silver carbonate solution was added to the mixture with stirring, and 0.12g of chloroauric acid was added, followed by 1.4g of ascorbic acid, and stirred for 30 minutes. At room temperature, 0.02g of potassium nitrate and 0.02g of ammonium perrhenate were added, and deionized water was added to make the total mass of the solution 20g, to prepare a dipping mixture. The addition amount of the silver carbonate ensures that the dipping mixed solution contains 28 to 30 weight percent of silver.
4g of the alpha-alumina carrier (specific surface area 1.0 m) used in comparative example 1 was added 2 G, pore volume 0.5 ml/g) into a vessel capable of being evacuated. Vacuumizing to the vacuum degree of more than 10mmHg, putting the carrier into 10g of the prepared impregnation mixed solution, immersing the carrier and keeping for 30min. The excess solution is leached away. And heating the impregnated carrier in nitrous oxide gas flow at 350 ℃ for 30min, and cooling to obtain the silver-gold bimetallic catalyst.
Test example
Analyzing the silver content and the gold content of the prepared catalyst, wherein the contents are calculated by metal elements; the activity and selectivity of the catalyst samples were measured using a microreactor evaluation unit under the aforementioned process conditions and the results of the tests are set forth in Table 1.
TABLE 1 test results of catalysts for ethylene oxide production
* Note: selectively taking the accumulated EO yield to 400T/M 3 Average value of catalyst time, reaction temperature, and cumulative EO production to 400T/M 3 Reaction temperature at the time of catalyst.
As can be seen by comparing the data in table 1, the silver content in the impregnation solution using silver carbonate can be further increased while increasing the silver content on the carrier, simplifying the preparation process compared to the method using silver nitrate.
The test results of comparative example 1 in the presence and absence of water show that the single silver catalyst suffers a large loss of selectivity and activity in the presence of 3% water, whereas the catalysts of examples 1-5, after addition of gold, show comparable activity and selectivity in the absence of water as the single silver catalyst, but show a large increase in activity and selectivity in the presence of water.
As can be seen from the data of example 2, example 3, and example 4, the silver-gold bimetal supported catalyst has lower stability and selectivity of activation under air conditions than the bimetal catalyst activated under a reducing atmosphere.
The data of example 5 show that a suitable gold content can further significantly improve the selectivity and stability of the catalyst.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
Claims (14)
1. A silver-gold bimetallic supported catalyst for the epoxidation of ethylene with water vapor, characterized in that the catalyst comprises an alpha-alumina support and supported thereon silver and gold, wherein the silver content is from 15 to 25wt% calculated as element and the gold content is from 50 to 2000ppmw calculated as element, based on the weight of the catalyst;
the catalyst is prepared by a method comprising the following steps:
(1) Dipping an alpha-alumina carrier by using a dipping solution containing a silver compound, a gold reducing agent, organic amine, an alkali metal auxiliary agent, a rhenium-containing auxiliary agent and an optional rhenium co-auxiliary agent;
(2) Filtering to remove the impregnation liquid;
(3) Subjecting the impregnated support to an activation thermal decomposition, the activation thermal decomposition being carried out in a reducing atmosphere;
the silver compound is silver carbonate;
the reducing atmosphere is in the presence of nitrous oxide gas.
2. A silver-gold bimetallic supported catalyst according to claim 1, characterized in that the gold content is from 200 to 1000ppmw calculated as element.
3. A method for preparing a silver-gold bimetallic supported catalyst as in claim 1 or 2, wherein the method comprises the steps of:
(1) Dipping an alpha-alumina carrier by using a dipping solution containing a silver compound, a gold reducing agent, organic amine, an alkali metal auxiliary agent, a rhenium-containing auxiliary agent and an optional rhenium co-auxiliary agent;
(2) Filtering to remove the impregnation liquid;
(3) Subjecting the impregnated support to an activation thermal decomposition, the activation thermal decomposition being carried out in a reducing atmosphere;
the silver compound is silver carbonate;
the reducing atmosphere is in the presence of nitrous oxide gas.
4. The method for preparing a silver-gold bimetallic supported catalyst according to claim 3, wherein in the step (1), the gold compound is chloroauric acid and/or a gold salt.
5. The method for preparing a silver-gold bimetallic supported catalyst according to claim 3, wherein in the step (1), the gold reducing agent is at least one selected from oxalic acid, formaldehyde, glucose and ascorbic acid.
6. The method for preparing a silver-gold bimetallic supported catalyst according to claim 5, wherein the gold reducing agent is ascorbic acid and/or glucose.
7. The method for preparing a silver-gold bimetallic supported catalyst according to claim 3, wherein, in the step (1),
the organic amine is selected from at least one of pyridine, butylamine, ethylenediamine, 1, 3-propane diamine, ethanolamine and triethylamine;
the alkali metal auxiliary agent is at least one selected from lithium, sodium, potassium, rubidium and cesium;
the rhenium-containing auxiliary agent is selected from at least one of rhenium elementary substance, rhenium oxide, perrhenic acid and perrhenate;
the rhenium co-additive is at least one of a chromium simple substance, a molybdenum simple substance, a tungsten simple substance, a boron simple substance, a chromium metal compound, a molybdenum metal compound, a tungsten metal compound and a boron compound.
8. The method for preparing the silver-gold bimetallic supported catalyst according to claim 7, wherein the organic amine is ethylenediamine and/or ethanolamine;
the rhenium-containing promoter is selected from perrhenic acid and/or perrhenate.
9. The method of making a silver-gold bimetallic supported catalyst of claim 8, wherein said rhenium-containing promoter is selected from at least one of perrhenic acid, cesium perrhenate, and ammonium perrhenate.
10. The method for preparing a silver-gold bimetal supported catalyst according to claim 3, wherein the temperature of the activation thermal decomposition in the step (3) is 150 to 450 ℃ and the time is 1 to 300 minutes.
11. A silver-gold bimetallic supported catalyst prepared by the preparation method of any one of claims 3 to 10.
12. Use of a silver-gold bimetallic supported catalyst according to any one of claims 1-2, 11 in an ethylene epoxidation reaction.
13. Use of a silver-gold bimetallic supported catalyst as in claim 12 in an ethylene epoxidation reaction, wherein the ethylene epoxidation reaction is carried out with a water vapor content of 0.5wt% to 10 wt%.
14. Use of a silver-gold bimetallic supported catalyst as in claim 13 in an ethylene epoxidation reaction wherein said ethylene epoxidation reaction is carried out in the presence of 2.5 to 8wt% water vapor.
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| US5447897A (en) * | 1993-05-17 | 1995-09-05 | Shell Oil Company | Ethylene oxide catalyst and process |
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