CN116196923A - Silver catalyst and preparation method and application thereof - Google Patents

Silver catalyst and preparation method and application thereof Download PDF

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Publication number
CN116196923A
CN116196923A CN202111455977.9A CN202111455977A CN116196923A CN 116196923 A CN116196923 A CN 116196923A CN 202111455977 A CN202111455977 A CN 202111455977A CN 116196923 A CN116196923 A CN 116196923A
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silver
silver catalyst
solution
nitrogen
hydrogen peroxide
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林强
李金兵
李旻旭
汤之强
李巍
代武军
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Sinopec Beijing Chemical Research Institute Co ltd
China Petroleum and Chemical Corp
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Sinopec Beijing Chemical Research Institute Co ltd
China Petroleum and Chemical Corp
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/66Silver or gold
    • B01J23/68Silver or gold with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/688Silver or gold with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with manganese, technetium or rhenium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04Alumina
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002Mixed oxides other than spinels, e.g. perovskite
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/30Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/60Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61Surface area
    • B01J35/612Surface area less than 10 m2/g
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/60Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63Pore volume
    • B01J35/6350.5-1.0 ml/g
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D301/00Preparation of oxiranes
    • C07D301/02Synthesis of the oxirane ring
    • C07D301/03Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08Synthesis 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
    • C07D301/10Synthesis 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
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07DHETEROCYCLIC COMPOUNDS
    • C07D303/00Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02Compounds containing oxirane rings
    • C07D303/04Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00Constitutive chemical elements of heterogeneous catalysts
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00Technologies relating to chemical industry
    • Y02P20/50Improvements relating to the production of bulk chemicals
    • Y02P20/52Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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Abstract

The invention belongs to the field of industrial catalysts, and relates to a silver catalyst and a preparation method and application thereof. The silver catalyst comprises the following components: i. a pretreated porous alumina support; silver on the pretreated porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters; the pretreatment is carried out by adopting a nitrogen-containing hydrogen peroxide solution. The silver catalyst has proper or higher catalytic activity and obviously improved stability, and is especially suitable for ethylene oxidation reaction to produce ethylene oxide.

Description

Silver catalyst and preparation method and application thereof
Technical Field
The invention belongs to the field of industrial catalysts, and particularly relates to a silver catalyst, a preparation method thereof and application of the silver catalyst in ethylene epoxidation production of ethylene oxide.
Background
Ethylene is oxidized to mainly generate ethylene oxide under the action of a silver catalyst, and side reactions are carried out to generate carbon dioxide, water and the like, wherein the activity, the selectivity and the stability are main performance indexes of the silver catalyst. The activity means a reaction temperature required for the production process of ethylene oxide to reach a certain reaction load, and the lower the reaction temperature is, the higher the activity of the catalyst is. By selectivity is meant the ratio of the moles of ethylene converted to ethylene oxide in the reaction to the total moles of ethylene reacted. Stability is expressed as the rate of decrease in activity and selectivity, with lower rates giving better catalyst stability. The use of a silver catalyst with high activity, high selectivity and good stability in the process of producing ethylene oxide by ethylene oxidation can greatly improve economic benefit, so that the production of the silver catalyst with high activity, high selectivity and good stability is the main direction of silver catalyst research. The performance of the silver catalyst has important relation with the composition of the catalyst and the preparation method, and also has important relation with the performance of a carrier used by the catalyst and the preparation method.
The preparation method of the silver catalyst mainly comprises two processes of preparing a porous carrier (such as alumina) and applying an active component and an auxiliary agent to the carrier.
Wherein, the carrier needs to provide a certain surface loading active component, the active component is uniformly dispersed on the carrier, the silver catalyst generally adopts alpha-alumina as the carrier, and the main preparation method is as follows: alumina powder is preparedThe raw materials are added with a binder, various additives and the like, evenly mixed and kneaded, then extruded and molded into green bodies (Raschig rings, spherical particles, porous columns, saddle shapes and the like) with different shapes, and finally sintered at high temperature to prepare porous heat-resistant alpha-alumina carrier products, as described in US 5063195, US5703001, US 5801259 and the like. In the preparation process of the silver catalyst carrier, an auxiliary agent is often added for improving the performance of the carrier, for example, US5100859A proposes that alkaline earth metal and SiO are added into an alumina carrier 2 And zirconia can improve the performance of the silver catalyst.
The application of the active components and auxiliaries to the support is generally effected industrially by means of impregnation activation. Firstly, preparing silver ammonia impregnating solution with a certain concentration by using silver salt, various auxiliary agents and organic amine, and carrying out complexation reaction on Ag ions and the organic amine to generate silver-organic amine complex ions; then the carrier is put into impregnating solution to be impregnated for enough time, so that silver amine complex ions and various auxiliary agent ions are impregnated on the surface of the carrier along with the solution; after leaching, finally, the silver-containing impregnated components on the surface of the carrier are put into an activation belt for activation, and during the activation process, various silver-containing impregnated components on the surface of the carrier are heated and gradually decomposed, silver ions are reduced into elemental silver, and particles of tens to hundreds of nanometers are formed on the surface of the carrier, so that the finished silver catalyst is obtained.
The uniformity of the size and the distribution of the silver particles have important influence on the performance of the silver catalyst, and the silver particles gradually migrate and grow up to reduce the activity, the stability, the service life and other performances of the catalyst, so that the migration and the growth of the silver particles are slowed down, and the performance, particularly the stability, of the silver catalyst can be improved. The traditional industrial silver catalyst preparation method has limited improvement on the size and distribution of silver particles, and the silver particles are easy to agglomerate and grow up in the use process of the silver catalyst, so that the improvement on the activity and selectivity of the catalyst is limited.
Disclosure of Invention
In view of the above-mentioned prior art, the present inventors have conducted extensive and intensive studies in the field of silver catalysts and preparation processes thereof, and as a result, have found that the use of a nitrogen-containing hydrogen peroxide solution for immersing a porous alumina carrier can achieve etching of the carrier, increase the roughness of the surface of the carrier, further increase the uniformity of the size and distribution of silver particles, and effectively prevent aggregation and growth of silver particles, thereby effectively improving the performance of the silver catalyst.
The first aspect of the invention provides a silver catalyst comprising the following components:
i. a pretreated porous alumina support; and
Silver on the pretreated porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the pretreatment is carried out by adopting a nitrogen-containing hydrogen peroxide solution.
A second aspect of the present invention provides a method for preparing the above silver catalyst, comprising the steps of:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier;
c. impregnating the pretreated porous alumina carrier with a silver-containing impregnating solution to obtain a solid-liquid mixture;
d. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step c, and drying the obtained solid phase;
and e, activating the dried solid phase obtained in the step d to obtain the silver catalyst.
In a third aspect, the invention provides the use of the silver catalyst in the epoxidation of ethylene to ethylene oxide.
The silver catalyst has proper or higher catalytic activity and obviously improved stability, and is especially suitable for ethylene oxidation reaction to produce ethylene oxide.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The invention provides a silver catalyst, which comprises the following components:
i. a pretreated porous alumina support; and
Silver on the pretreated porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the pretreatment is carried out by adopting a nitrogen-containing hydrogen peroxide solution.
According to a preferred embodiment of the invention, the step of pre-treating comprises:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. and c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier.
According to some preferred embodiments of the present invention, the nitrogen-containing hydrogen peroxide solution is a mixed solution of a nitrogen-containing solution and hydrogen peroxide. The nitrogen in the nitrogen-containing hydrogen peroxide solution can be from organic amine, ammonia, ammonium salt, various compounds containing amide group, high polymer, etc., in particular, the nitrogen-containing solution comprises but not limited to organic amine, ammonia, NH-containing solution 4 + At least one of the ammonium salt solutions of (a). Preferably, the nitrogen-containing solution is ethylenediamine, ethanolamine, ammonia water, ammonium fluoride aqueous solution, NH 4 HCO 3 At least one of the aqueous solutions.
According to some preferred embodiments of the present invention, the weight of the nitrogen element in the nitrogen-containing hydrogen peroxide solution is 0.01-10 wt%, preferably, the weight of the nitrogen element in the nitrogen-containing hydrogen peroxide solution is 0.02-5 wt%, such as 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1wt%, 0.2 wt%, 0.5wt%, 0.8 wt%, 1wt%, 2wt%, 3 wt%, 4 wt%, of the total weight of the solution. The weight of the hydrogen peroxide is 0.01-10 wt%, preferably 0.05-8 wt%, such as 0.1wt%, 0.2 wt%, 0.5wt%, 0.8 wt%, 1wt%, 2wt%, 3 wt%, 4 wt%, 5wt%, 6 wt%, 7 wt%, of the total weight of the solution.
The untreated porous alumina carrier is not particularly limited in the present invention, and a porous alumina carrier conventional in the art can be used, and preferably has the following characteristics: alpha-A1 2 O 3 Content of>85%, preferably alpha-A1 2 O 3 Content of>90%; crush strength of particles>20N, preferably 30-150N; the specific surface area is 0.2-7.0m 2 Preferably 0.5-6.0m 2 /g; water absorption rate>30%, preferably>40%; and pore volume of 0.30-0.70ml/g, preferably 0.35-0.50ml/g.
According to the invention, the catalyst may be prepared by a process comprising the steps of:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier;
c. impregnating the pretreated porous alumina carrier with a silver-containing impregnating solution to obtain a solid-liquid mixture;
d. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step c, and drying the obtained solid phase;
and e, activating the dried solid phase obtained in the step d to obtain the silver catalyst.
In the soaking process, the solution should not exceed the whole carrier, the dosage should be more than one time of the weight of the carrier, and simultaneously stirring, ultrasonic treatment and the like can be carried out, so that the carrier can be fully contacted with the solution, and the soaking time should not be less than 10 minutes in order to make the soaking more uniform.
The support should then be removed and, after draining, the solid phase obtained is dried. The drying temperature is preferably in the range of 80-800 ℃, the drying time is not less than 1 hour, and the drying time is correspondingly prolonged when the drying temperature is low.
After the carrier treatment is completed, the treated porous alumina carrier is impregnated with silver-containing impregnating solution, and then the carrier impregnated with silver is taken out for activation, so that a final product is obtained.
According to the method of the present invention, the carrier is preferably pre-evacuated in order to ensure uniform and sufficient loading of silver.
According to the method of the invention, the activation can be carried out in air or in an inert gas. For example, the dried solid phase may be activated in a stream of flowing air or inert gas such as nitrogen, argon or the like at 180-700 ℃, preferably 200-500 ℃ for a period of typically at least 2 minutes, for example 2-120 minutes, preferably 2-60 minutes. To ensure a high activity of the catalyst, the activation temperature is preferably not higher than 500 ℃.
According to the method of the present invention, the impregnation liquid contains at least one selected from the group consisting of alkali metal promoters, alkaline earth metal promoters, and synergistic promoters of rhenium and rhenium, in addition to the silver compound.
According to the method of the present invention, the silver element contained in the impregnation liquid is derived from a silver compound, which may be any silver compound suitable for preparing a silver catalyst for ethylene oxide production. The present invention preferably uses at least one of silver oxide, silver nitrate and silver carbonate. According to the present invention, the impregnation liquid generally contains an organic amine compound, and the organic amine compound used may be any organic amine compound suitable for preparing a silver catalyst, as long as the organic amine compound is capable of forming a silver amine complex with a silver compound. For the purposes of the present invention, preference is given to using pyridine, butylamine, ethylenediamine, 1, 3-propylenediamine, ethanolamine or the like or mixtures thereof.
According to the invention, the alkali metal promoter may be a compound of lithium, sodium, potassium, rubidium or cesium (such as nitrates, sulfates and hydroxides) or mixtures thereof, preferably cesium nitrate, lithium nitrate and/or potassium hydroxide. The alkaline earth metal promoter may be one or more of magnesium, calcium, strontium and barium compounds, such as one or more of oxides, oxalates, sulphates, acetates and nitrates of the alkaline earth metal element, preferably barium compounds and/or strontium compounds, such as barium acetate and/or strontium acetate.
According to the invention, the rhenium promoter may be a rhenium oxide, perrhenic acid, a perrhenate, or a mixture thereof, preferably perrhenic acid and/or a perrhenate, such as perrhenic acid, cesium perrhenate and/or ammonium perrhenate, and the like. In addition to the silver compound, the organic amine, the optional alkali metal promoter, the optional alkaline earth metal promoter, and the optional rhenium promoter, a co-promoter of a rhenium promoter may be added to the impregnation solution to further improve the activity, selectivity, and stability of the resulting silver catalyst. The co-promoter of the rhenium promoter in the present invention may be one or more selected from chromium compounds, molybdenum compounds, tungsten compounds, and boron compounds.
According to the invention, the term "optional" means that the catalyst may or may not contain, e.g. optionally an alkali metal, and that the catalyst may or may not contain an alkali metal.
According to one embodiment of the invention, the step of preparing a silver-containing impregnating solution comprises: silver carbonate is dissolved in an aqueous solution of an organic amine such as pyridine, butylamine, ethylenediamine, 1, 3-propylenediamine, ethanolamine or a mixture thereof to prepare an impregnating solution. Then impregnating the porous alpha-alumina carrier with the obtained impregnating solution for 10-60 minutes under the condition of vacuum degree less than 0.1 atmosphere, draining and drying, wherein the drying temperature can be selected from room temperature to 100 ℃, and the drying time can be selected from 1-96 hours. Finally, the activation is carried out in air or inert gas at a temperature in the range of 200-500 ℃ for 1-120 minutes, preferably 2-60 minutes. Silver oxide, silver nitrate, etc. may be used instead of silver carbonate.
In a specific embodiment of the silver catalyst, the alkali metal is one or more selected from lithium, sodium, potassium, rubidium and cesium; cesium and/or potassium are preferred, cesium being most preferred. The alkaline earth metal is one or more selected from magnesium, calcium, strontium and barium, preferably strontium and/or barium. The rhenium co-promoter element is selected from at least one of chromium, molybdenum, tungsten, and boron.
According to the silver catalyst of the present invention, silver is dispersed on the surface and in the pores of the alumina carrier. In order to control economy on the basis of ensuring catalyst performance, the content of silver element in the silver catalyst is 1-35wt%, preferably 5-30wt%, based on the total weight of the silver catalyst; the content of nitrogen element is 1-1500ppm, preferably 10-1000ppm; the content of alkali metal element is 0-2000ppm, preferably 10-1500ppm; the content of rhenium element is 0-1500ppm, preferably 10-1000ppm; the content of the co-promoter element of rhenium is 0 to 1000ppm, preferably 10 to 500ppm.
The silver catalyst can be applied to the reaction of ethylene epoxidation to produce ethylene oxide.
The present invention will be further described with reference to examples, but the scope of the present invention is not limited to these examples.
Determination of catalyst Performance: the activity and selectivity of each silver catalyst of the present invention were tested by a laboratory microreactor (hereinafter referred to as "microreactor") evaluation device. The reactor used in the micro-reaction evaluation device is a stainless steel reaction tube with an inner diameter of 4mm, and the reaction tube is arranged in a heating sleeve. The catalyst loading volume was 1mL, and inert packing was placed in the lower portion to allow the catalyst bed to be located in the constant temperature zone of the heating mantle. The activity and selectivity measurement conditions adopted by the invention are as follows: composition of reaction gas, ethylene (C) 2 H 4 ) 28.0.+ -. 1.0mol%; oxygen (O) 2 ) 7.4+ -0.2 mol%; carbon dioxide (CO) 2 ) Less than 5.0mol%; gas-stabilizing (N) 2 ) The balance; the inhibitor dichloroethane, 0.1-2.0ppm; airspeed, 8000/h; EO concentration at reactor outlet, 3.0mol%; space-time yield, 470kg EO/m 3 Cat./h。
After the above reaction conditions were stably reached, the gas composition at the inlet and outlet of the reactor was continuously measured. After the volume shrinkage correction is carried out on the measurement result, the selectivity is calculated according to the following formula:
selectivity of
Figure BDA0003386657970000071
Where ΔEO is the difference in ethylene oxide concentration in the reactor outlet and inlet gases, ΔCO 2 The concentration difference of carbon dioxide in the outlet gas and the inlet gas of the reactor is that the average of more than 10 groups of test data is taken as the test junction of the dayAnd (5) fruits.
The present invention will be further described with reference to examples, but the scope of the present invention is not limited to these examples.
Preparation of Carrier A
600g of 50-500 mesh trihydrate A1 2 O 3 And 300g of pseudomonohydrate A1 passing through a 200 mesh sieve 2 O 3 Put into a mixer to be mixed evenly, put into a kneader, added with 100 milliliters of 20 weight percent nitric acid aqueous solution, and kneaded into paste which can be extruded and molded. Extruding to obtain single-hole Raschig ring column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 2.0mm, and drying at 80-120deg.C for 2 hr to reduce free water content below 10wt% to obtain green body. Then placing the green body into an electric furnace, raising the temperature from room temperature to 1200-1500 ℃ for 30 hours, and keeping the temperature at the high temperature for 1-6 hours to obtain white alpha-A1 2 O 3 Carrier sample A, alpha-A1 2 O 3 Content of>90% of the steel has a crush strength of 140N and a specific surface area of 1.1m 2 Per g, water absorption of 50% and pore volume of 0.5ml/g.
Comparative example 1
Into a glass flask with stirring, 15g of ethylenediamine, 5.5g of ethanolamine and 19g of deionized water were charged to obtain a mixed solution. Adding silver carbonate into the obtained mixed solution slowly under stirring, keeping the temperature at 15-35 ℃ to dissolve the silver carbonate completely, wherein the addition amount of the silver carbonate is such that the finally prepared impregnating solution contains 24 weight percent of silver. Adding 0.15g cesium nitrate and 0.2g ammonium perrhenate, and adding deionized water to make the total mass of the solution reach 100g, so as to prepare the impregnating solution. 30g of carrier A are taken and placed in a vacuum-evacuable container. Vacuumizing to a vacuum degree lower than 0.1 atmosphere, and putting the impregnating solution into the vacuum degree to immerse the carrier for 30 minutes. After which the excess impregnation liquor is leached away. Heating the impregnated carrier in air flow at 250 ℃ for 5 minutes, and cooling to obtain the silver catalyst.
Comparative example 2
30g of the carrier A was taken, immersed in 50g of an aqueous solution containing 2wt% of ethylenediamine for half an hour while sonicating, taken out and drained, and dried at 500℃for 2 hours. Into a glass flask with stirring, 15g of ethylenediamine, 5.5g of ethanolamine and 19g of deionized water were charged to obtain a mixed solution. Adding silver carbonate into the obtained mixed solution slowly under stirring, keeping the temperature at 15-35 ℃ to dissolve the silver carbonate completely, wherein the addition amount of the silver carbonate is such that the finally prepared impregnating solution contains 24 weight percent of silver. Adding 0.15g cesium nitrate and 0.2g ammonium perrhenate, and adding deionized water to make the total mass of the solution reach 100g, so as to prepare the impregnating solution. Placing the treated carrier A into a container capable of being vacuumized, vacuumizing to a vacuum degree lower than 0.1 atmosphere, placing the impregnating solution into the container, immersing the carrier, and keeping for 30 minutes. After which the excess impregnation liquor is leached away. Heating the impregnated carrier in air flow at 250 ℃ for 5 minutes, and cooling to obtain the silver catalyst.
Comparative example 3
30g of carrier A is taken, 50g of 2wt% hydrogen peroxide solution is used for soaking for half an hour and simultaneously ultrasonic treatment is carried out, then the carrier A is taken out, drained and dried for 2 hours at 500 ℃ for standby. Into a glass flask with stirring, 15g of ethylenediamine, 5.5g of ethanolamine and 19g of deionized water were charged to obtain a mixed solution. Adding silver carbonate into the obtained mixed solution slowly under stirring, keeping the temperature at 15-35 ℃ to dissolve the silver carbonate completely, wherein the addition amount of the silver carbonate is such that the finally prepared impregnating solution contains 24 weight percent of silver. Adding 0.15g cesium nitrate and 0.2g ammonium perrhenate, and adding deionized water to make the total mass of the solution reach 100g, so as to prepare the impregnating solution. Placing the treated carrier A into a container capable of being vacuumized, vacuumizing to a vacuum degree lower than 0.1 atmosphere, placing the impregnating solution into the container, immersing the carrier, and keeping for 30 minutes. After which the excess impregnation liquor is leached away. Heating the impregnated carrier in air flow at 250 ℃ for 5 minutes, and cooling to obtain the silver catalyst.
Examples 1 to 7
Example 1
30g of carrier A is taken, 50g of 0.5wt% hydrogen peroxide solution containing 2wt% ethylenediamine is used for soaking for half an hour and simultaneously ultrasonic treatment is carried out, then the carrier A is taken out, drained and dried for 2 hours at 500 ℃ for standby. Into a glass flask with stirring, 15g of ethylenediamine, 5.5g of ethanolamine and 19g of deionized water were charged to obtain a mixed solution. Adding silver carbonate into the obtained mixed solution slowly under stirring, keeping the temperature at 15-35 ℃ to dissolve the silver carbonate completely, wherein the addition amount of the silver carbonate is such that the finally prepared impregnating solution contains 24 weight percent of silver. Adding 0.15g cesium nitrate and 0.2g ammonium perrhenate, and adding deionized water to make the total mass of the solution reach 100g, so as to prepare the impregnating solution. Placing the treated carrier A into a container capable of being vacuumized, vacuumizing to a vacuum degree lower than 0.1 atmosphere, placing the impregnating solution into the container, immersing the carrier, and keeping for 30 minutes. After which the excess impregnation liquor is leached away. Heating the impregnated carrier in air flow at 250 ℃ for 5 minutes, and cooling to obtain a silver catalyst, wherein the content of nitrogen element in the catalyst is 40ppm, and the content of alkali metal element is 550ppm; the content of rhenium element was 260ppm.
Example 2
30g of carrier A is taken, soaked for half an hour with 50g of 0.1wt% hydrogen peroxide solution containing 0.5wt% ethylenediamine and simultaneously sonicated, then the carrier A is taken out, drained and dried for 8 hours at 150 ℃ for later use. Into a glass flask with stirring, 15g of ethylenediamine, 5.5g of ethanolamine and 19g of deionized water were charged to obtain a mixed solution. Adding silver carbonate into the obtained mixed solution slowly under stirring, keeping the temperature at 15-35 ℃ to dissolve the silver carbonate completely, wherein the addition amount of the silver carbonate is such that the finally prepared impregnating solution contains 24 weight percent of silver. Adding 0.15g cesium nitrate and 0.2g ammonium perrhenate, and adding deionized water to make the total mass of the solution reach 100g, so as to prepare the impregnating solution. Placing the treated carrier A into a container capable of being vacuumized, vacuumizing to a vacuum degree lower than 0.1 atmosphere, placing the impregnating solution into the container, immersing the carrier, and keeping for 30 minutes. After which the excess impregnation liquor is leached away. Heating the impregnated carrier in air flow at 250 ℃ for 5 minutes, and cooling to obtain the silver catalyst, wherein the content of nitrogen element in the catalyst is 20ppm.
Example 3
The procedure was the same as in example 1, except that 50g of the carrier was immersed in a 0.1wt% hydrogen peroxide solution containing 1wt% of ethanolamine for half an hour, and the content of nitrogen element in the catalyst was 60ppm.
Implementation of the embodimentsExample 4
The procedure was as in example 1, except that 50g of the carrier was immersed in a 0.1wt% hydrogen peroxide solution containing 1wt% ammonium fluoride for half an hour, and the nitrogen element content in the catalyst was 70ppm.
Example 5
The procedure was the same as in example 1, except that 50g of a 0.1wt% hydrogen peroxide solution containing 2.5wt% ammonia was used to soak the carrier for half an hour, and the nitrogen element content in the catalyst was 50ppm.
Example 6
The procedure was as in example 1, except that 50g of a 5wt% hydrogen peroxide solution containing 0.1wt% ethylenediamine was used to soak the carrier for half an hour, and the nitrogen element content in the catalyst was 40ppm.
Example 7
The procedure was as in example 2, except that 50g of a solution containing 0.1% by weight of ethylenediamine, 0.1% by weight of ammonium fluoride, 0.1% by weight of aqueous ammonia, and 1% by weight of hydrogen peroxide was used to soak the carrier for half an hour, and the nitrogen content of the catalyst was 80ppm.
Evaluation of Performance
The activity and selectivity of each catalyst sample was determined using a microreactor evaluation device under the process conditions described in the section "determination of catalyst Performance" above, and the test results are set forth in Table 1. The reaction temperature in Table 1 is such that the cumulative EO yield reaches 200T/M 3 The value of catalyst is that the cumulative EO yield is up to 500T/M 3 Average value at catalyst.
TABLE 1
Figure BDA0003386657970000111
Figure BDA0003386657970000121
As can be seen from Table 1, the silver catalyst prepared from the treated carrier has better selectivity and catalytic activity than the silver catalyst prepared from the untreated carrier, and is particularly suitable for the reaction of ethylene oxidation to produce ethylene oxide.
It can be seen that the silver catalyst obtained by soaking the porous alumina carrier in the nitrogen-containing hydrogen peroxide solution can obtain significantly improved activity and selectivity when used for catalyzing the oxidation of ethylene to prepare ethylene oxide.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or 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 various embodiments described.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

Claims (12)

1. A silver catalyst comprising the following components:
i. a pretreated porous alumina support; and
Silver on the pretreated porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the pretreatment is carried out by adopting a nitrogen-containing hydrogen peroxide solution.
2. The silver catalyst according to claim 1, wherein the step of pretreating comprises:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. and c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier.
3. The silver catalyst according to claim 1 or 2, wherein the nitrogen-containing hydrogen peroxide solution is a mixed solution of a nitrogen-containing solution and hydrogen peroxide; the nitrogen-containing solution is preferably organic amine, ammonia water or NH 4 + At least one of the ammonium salt solutions of (a); preferably ethylenediamine, ethanolamine, aqueous ammonia, aqueous ammonium fluoride and NH 4 HCO 3 At least one of the aqueous solutions.
4. The silver catalyst according to claim 1 or 2, wherein the nitrogen element in the nitrogen-containing hydrogen peroxide solution accounts for 0.01-10 wt% of the total weight of the solution, and the hydrogen peroxide accounts for 0.01-10 wt% of the total weight of the solution; preferably, the weight of nitrogen element in the nitrogen-containing hydrogen peroxide solution accounts for 0.02-5 wt% of the total weight of the solution, and the weight of hydrogen peroxide accounts for 0.05-8 wt% of the total weight of the solution.
5. The silver catalyst according to claim 2, wherein in step a, the soaking is performed under stirring or ultrasonic conditions for a soaking time of not less than 10 minutes.
6. The silver catalyst according to claim 2, wherein in step b, the drying temperature is 80 ℃ to 800 ℃ and the drying time is not less than 1 hour.
7. The silver catalyst according to claim 1 or 2, wherein the silver catalyst is prepared by a method comprising the steps of:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier;
c. impregnating the pretreated porous alumina carrier with a silver-containing impregnating solution to obtain a solid-liquid mixture;
d. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step c, and drying the obtained solid phase;
and e, activating the dried solid phase obtained in the step d to obtain the silver catalyst.
8. The silver catalyst according to claim 7, wherein the silver-containing impregnation liquid includes therein a silver compound and at least one selected from the group consisting of alkali metal promoters, alkaline earth metal promoters, and co-promoters of rhenium and rhenium.
9. The silver catalyst according to claim 1 or 2, wherein the untreated porous alumina support has the following characteristics: alpha-A1 2 O 3 Content of>85%, preferably alpha-A1 2 O 3 Content of>90%; crush strength of particles>20N, preferably 30-150N; the specific surface area is 0.2-7.0m 2 Preferably 0.5-6.0m 2 /g; water absorption rate>30%, preferably>40%; and pore volume of 0.30-0.70ml/g, preferably 0.35-0.50ml/g.
10. The silver catalyst according to claim 1 or 2, wherein the content of silver element in the silver catalyst is 1-35wt%, preferably 5-30wt%, based on the total weight of the silver catalyst; the content of nitrogen element is 1-1500ppm, preferably 10-1000ppm; the content of alkali metal element is 0-2000ppm, preferably 10-1500ppm; the content of rhenium element is 0-1500ppm, preferably 10-1000ppm; the content of the co-promoter element of rhenium is 0 to 1000ppm, preferably 10 to 500ppm.
11. The method for producing a silver catalyst according to any one of claims 1 to 10, comprising the steps of:
a. soaking the untreated porous alumina carrier by using a nitrogen-containing hydrogen peroxide solution;
b. c, carrying out solid-liquid separation on the mixture obtained in the step a, and drying the obtained solid phase to obtain the pretreated porous alumina carrier;
c. impregnating the pretreated porous alumina carrier with a silver-containing impregnating solution to obtain a solid-liquid mixture;
d. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step c, and drying the obtained solid phase;
and e, activating the dried solid phase obtained in the step d to obtain the silver catalyst.
12. Use of the silver catalyst of any one of claims 1-10 in the epoxidation of ethylene to ethylene oxide.
CN202111455977.9A 2021-12-01 2021-12-01 Silver catalyst and preparation method and application thereof Pending CN116196923A (en)

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