CN116196922B - Silver catalyst and preparation method and application thereof - Google Patents

Silver catalyst and preparation method and application thereof Download PDF

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CN116196922B
CN116196922B CN202111455961.8A CN202111455961A CN116196922B CN 116196922 B CN116196922 B CN 116196922B CN 202111455961 A CN202111455961 A CN 202111455961A CN 116196922 B CN116196922 B CN 116196922B
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silver
silver catalyst
solid
content
drying
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CN116196922A (en
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李金兵
林强
廉括
代武军
李巍
汤之强
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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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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • 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
    • B01J23/54—Catalysts 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
    • B01J23/66—Silver or gold
    • B01J23/68—Silver or gold with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/688—Silver or gold with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with manganese, technetium or rhenium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/612—Surface area less than 10 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63—Pore volume
    • B01J35/635—0.5-1.0 ml/g
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • 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

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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 composition comprises the following components: i. a porous alumina support; silver on the porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters; the silver catalyst is prepared by a method comprising the following steps: a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying; b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture; c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase; d. and c, activating the dried solid phase obtained in the step c. The silver catalyst has proper or higher catalytic activity and obviously improved stability, and is suitable for the reaction of producing ethylene oxide by ethylene oxidation.

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 of the silver catalyst 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: the alumina powder is added with a binder, various additives and the like, uniformly mixed and kneaded, then extruded and molded into blanks (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, US 5703001, US 5801259 and the like. In the preparation process of the silver catalyst carrier, an auxiliary agent is often added to improve the performance of the carrier, for example, US5100859a suggests that adding alkaline earth metal, siO 2 and zirconia to an alumina carrier 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 etching of the support and the surface roughness of the support can be improved by immersing the porous alumina support in a precursor solution capable of generating hydrogen peroxide and optionally a nitrogen-containing solution, thereby improving the uniformity of the size and distribution of silver particles, effectively preventing the aggregation and growth of silver particles, and thus effectively improving the performance of the silver catalyst.
The first aspect of the invention provides a silver catalyst comprising the following components:
i. A porous alumina support; and
Silver on the porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the silver catalyst is prepared by a method comprising the following steps:
a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying;
b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture;
c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase;
d. and c, activating the dried solid phase obtained in the step c to obtain the silver catalyst.
A second aspect of the present invention provides a method for preparing the above silver catalyst, comprising the steps of:
a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying;
b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture;
c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase;
d. and c, activating the dried solid phase obtained in the step c 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 porous alumina support; and
Silver on the porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the silver catalyst is prepared by a method comprising the following steps:
a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying;
b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture;
c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase;
d. and c, activating the dried solid phase obtained in the step c to obtain the silver catalyst.
According to a preferred embodiment of the present invention, the silver catalyst further comprises, by a process comprising the steps of:
e. Before the step b, soaking the porous alumina carrier with nitrogen-containing solution and performing solid-liquid separation.
According to the method, the porous alumina carrier is treated by the precursor solution capable of generating hydrogen peroxide, so that the carrier can be etched, the surface roughness of the carrier is improved, the uniformity of the size and distribution of silver particles is further improved, and the performance can be further improved by treating the carrier by the nitrogen-containing solution.
The order of execution of step e is not particularly limited in the present invention, and step e may be executed before, during or after step a.
Specifically, when step e is performed before step a, step e further optionally includes a step of drying the solid phase obtained by the solid-liquid separation.
When step e is performed in step a, step e is preferably performed after the solid-liquid separation of step a and before drying.
When step e is performed after step a, step e preferably further comprises a step of drying the solid phase obtained by the solid-liquid separation.
According to some preferred embodiments of the present invention, the nitrogen in the nitrogen-containing hydrogen peroxide solution may be derived from at least one of organic amine, ammonia, ammonium salt, various amide group-containing compounds, polymers, and the like, and specifically, the nitrogen-containing solution includes, but is not limited to, at least one of organic amine, ammonia, ammonium salt containing NH 4 +, and a mixed solution formed by at least one of them and water and/or an organic solvent. Preferably, the nitrogen-containing solution is at least one of ethylenediamine, ethanolamine, ammonia, ammonium fluoride, NH 4HCO3, and solutions formed by at least one of them with water and/or C 1-C4 alkyl alcohol. The C 1-C4 alkyl alcohols include, but are not limited to, methanol, ethanol, propanol, ethylene glycol.
The nitrogen element content in the above-mentioned nitrogen-containing solution is preferably 0.01 to 10 wt%, more preferably 0.02 to 5wt%, for example, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.2 wt%, 0.5wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%.
According to the present invention, the precursor capable of generating hydrogen peroxide is preferably hydrogen peroxide, and the concentration of the hydrogen peroxide is preferably 0.01 to 10 wt%, more preferably 0.05 to 5 wt%, for example, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%.
The porous alumina carrier is not particularly limited, and a porous alumina carrier conventional in the art can be used, and preferably has the following characteristics: the content of alpha-A1 2O3 is more than 85 percent, and the content of alpha-A1 2O3 is more than 90 percent is preferred; particle crush strength >20N, preferably 30-150N; the specific surface area is 0.2-7.0m 2/g, preferably 0.5-6.0m 2/g; water absorption >30%, preferably >40%; and pore volume of 0.30-0.70ml/g, preferably 0.35-0.50ml/g.
According to the method of the invention, in each 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 at the same time, 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 carrier is then removed and drained, and the solid phase obtained is dried or soaked in the next step. 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 0-1500ppm, 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 was packed in a volume of 1ml with inert packing in the lower part 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: reaction gas composition, ethylene (C 2H4), 28.0.+ -. 1.0mol%; oxygen (O 2), 7.4.+ -. 0.2mol%; carbon dioxide (CO 2) < 5.0mol%; stabilizing gas (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
Where Δeo is the difference in ethylene oxide concentration in the reactor outlet gas and inlet gas, Δco 2 is the difference in carbon dioxide concentration in the reactor outlet gas and inlet gas, and the average of more than 10 sets of test data is taken as the test result on the same day.
The present invention is further described below 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 2O3 and 300g of 200 mesh pseudomonohydrate A1 2O3 are put into a mixer to be mixed uniformly, and then put into a kneader, 100 ml of 20 wt% nitric acid aqueous solution is added, and kneaded into paste which can be extruded and formed. 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 the green body is put into an electric furnace, the temperature is raised from room temperature to 1200-1500 ℃ for 30 hours, and the temperature is kept constant for 1-6 hours at the high temperature, so that a white alpha-A1 2O3 carrier sample A, the alpha-A1 2O3 content of which is more than 90 percent, the crushing strength of which is 140N, the specific surface area of which is 1.1m 2/g, the water absorption rate of which is 50 percent and the pore volume of which is 0.5ml/g, is obtained.
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.
Examples 1 to 6
Example 1
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, after draining, 50g of ethylenediamine aqueous solution containing 2wt% is used for soaking for half an hour and simultaneously ultrasonic treatment, after taking out and draining, the carrier A is 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 50ppm, and the content of alkali metal element is 550ppm; the content of rhenium element was 260ppm.
Example 2
30G of carrier A is taken, 50g of ethanol solution containing 2wt% of ethanolamine is soaked for half an hour and simultaneously subjected to ultrasonic treatment, then the carrier A is taken out, after draining, 50g of hydrogen peroxide solution containing 0.5wt% is soaked for half an hour and simultaneously subjected to ultrasonic treatment, and after taking out and draining, the carrier A is 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, wherein the content of nitrogen element in the catalyst is 30ppm.
Example 3
30G of carrier A is taken, 50g of 1wt% 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, after draining, the carrier A is dried for 2 hours at 500 ℃,50 g of ammonia water solution containing 2wt% is used for soaking for half an hour and simultaneously ultrasonic treatment is carried out, after taking out and draining, the carrier A is dried for 8 hours at 150 ℃ 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, wherein the content of nitrogen element in the catalyst is 20ppm.
Example 4
30G of the carrier A was taken, immersed in 50g of an ethanol-glycol solution containing 2wt% of ethanol for half an hour while sonicating, and then taken out, drained and dried at 500℃for 2 hours. Then 50g of 0.5wt% hydrogen peroxide solution is used for soaking for half an hour and ultrasonic treatment is carried out simultaneously, and the mixture is taken out and drained and dried for 8 hours at 150 ℃. 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 nitrogen element content in the catalyst is 80ppm.
Example 5
30G of the support A was taken, immersed in 50g of an aqueous solution containing 2wt% of NH 4HCO3 for half an hour while sonicating, after which the support was taken out, drained and dried at 150℃for 2 hours. Then 50g of aqueous ammonia solution containing 2wt% of hydrogen peroxide solution containing 0.5wt% is soaked for half an hour and simultaneously is subjected to ultrasonic treatment, taken out and drained, and then dried for 8 hours at 500 ℃. 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 40ppm.
Example 6
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.
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 the value at which the cumulative EO yield reaches the 200T/M 3 catalyst, and the average value at which the cumulative EO yield reaches the 500T/M 3 catalyst is selectively taken.
TABLE 1
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 a hydrogen peroxide solution and optionally a nitrogen-containing solution can have significantly improved activity and selectivity when used for catalyzing the oxidation of ethylene to 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 (20)

1. A silver catalyst comprising the following components:
i. A porous alumina support; and
Silver on the porous alumina support, and optionally one or more of alkali metal, alkaline earth metal, rhenium and rhenium co-promoters;
the silver catalyst is prepared by a method comprising the following steps:
a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying;
b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture;
c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase;
d. And c, activating the dried solid phase obtained in the step c to obtain the silver catalyst.
2. The silver catalyst according to claim 1, wherein the preparation method of the silver catalyst further comprises:
e. Before the step b, soaking the porous alumina carrier with nitrogen-containing solution and performing solid-liquid separation.
3. The silver catalyst according to claim 2, wherein step e is performed before, during or after step a;
When step e is performed before step a, step e optionally further comprises a step of drying the solid phase obtained by the solid-liquid separation;
when step e is performed in step a, step e is performed after the solid-liquid separation of step a, before drying;
when step e is performed after step a, step e further comprises a step of drying the solid phase obtained by the solid-liquid separation.
4. The silver catalyst according to claim 2 or 3, wherein the nitrogen-containing solution is at least one of an organic amine, aqueous ammonia, an ammonium salt containing NH 4 +, and a solution of at least one of them with water and/or an organic solvent.
5. The catalyst of claim 4, wherein the nitrogen-containing solution is at least one of ethylenediamine, ethanolamine, ammonia, ammonium fluoride, NH 4HCO3, and solutions of at least one of them with water and/or C 1-C4 alkyl alcohol.
6. The catalyst of claim 5, wherein the C 1-C4 alkyl alcohol is at least one of methanol, ethanol, propanol, and ethylene glycol.
7. The silver catalyst according to claim 2 or 3, wherein the nitrogen element content in the nitrogen-containing solution is 0.01 to 10% by weight.
8. The catalyst according to claim 7, wherein the nitrogen element content in the nitrogen-containing solution is 0.02-5 wt%.
9. The silver catalyst according to claim 1 or 2, wherein the hydrogen peroxide-generating precursor solution is hydrogen peroxide.
10. The catalyst of claim 9, wherein the hydrogen peroxide is present in a concentration of 0.01-10 wt%.
11. The catalyst of claim 10, wherein the hydrogen peroxide is present in a concentration of 0.05-5 wt%.
12. The silver catalyst according to claim 1 or 2, wherein the soaking is performed under stirring or ultrasonic conditions for not less than 10 minutes; the drying temperature is 80-800 ℃ and the drying time is not less than 1 hour.
13. The silver catalyst according to claim 1 or 2, 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 synergistic promoters of rhenium and rhenium.
14. The silver catalyst according to claim 1 or 2, wherein the porous alumina carrier has the following characteristics: alpha-A1 2O3 content >85%; particle crush strength >20N; the specific surface area is 0.2-7.0m 2/g; the water absorption rate is more than 30%; and a pore volume of 0.30-0.70ml/g.
15. The silver catalyst according to claim 14, wherein the porous alumina support has the following characteristics: the content of alpha-A1 2O3 is more than 90%, the crushing strength of the particles is 30-150N, the specific surface area is 0.5-6.0m 2/g, the water absorption is more than 40%, and the pore volume is 0.35-0.50ml/g.
16. The silver catalyst according to claim 1 or 2, wherein the content of silver element in the silver catalyst is 1 to 35wt% based on the total weight of the silver catalyst; the content of nitrogen element is 0-1500ppm; the content of alkali metal element is 0-2000ppm; the content of rhenium element is 0-1500ppm; the content of the synergistic auxiliary element of rhenium is 0-1000ppm.
17. The silver catalyst according to claim 16, wherein the silver catalyst has a content of silver element of 5 to 30wt% based on the total weight of the silver catalyst; the content of nitrogen element is 10-1000ppm; the content of alkali metal element is 10-1500ppm; the content of rhenium element is 10-1000ppm; the content of the co-promoter element of rhenium is 10-500ppm.
18. The method for producing a silver catalyst according to any one of claims 1 to 17, comprising the steps of:
a. soaking the porous alumina carrier with precursor solution capable of generating hydrogen peroxide, and then performing solid-liquid separation and drying;
b. impregnating the dried solid phase obtained in the previous step with a silver-containing impregnating solution to obtain a solid-liquid mixture;
c. c, carrying out solid-liquid separation on the solid-liquid mixture obtained in the step b, and drying the obtained solid phase;
d. And c, activating the dried solid phase obtained in the step c to obtain the silver catalyst.
19. The method of manufacturing of claim 18, wherein the method further comprises:
e. Before the step b, soaking the porous alumina carrier with nitrogen-containing solution and performing solid-liquid separation.
20. Use of the silver catalyst of any one of claims 1-17 in the epoxidation of ethylene to ethylene oxide.
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US5364826A (en) * 1993-09-13 1994-11-15 Shell Oil Company Process for preparing ethylene oxide catalysts
CN100577289C (en) * 2006-01-28 2010-01-06 中国石油化工股份有限公司 The carrier of ethylene oxide silver catalyst, its preparation method and application thereof
KR20150013704A (en) * 2012-05-04 2015-02-05 바스프 에스이 Catalyst for the epoxidation of alkenes
CN108607614B (en) * 2016-12-09 2020-07-21 中国石油化工股份有限公司 Silver catalyst and preparation method and application thereof
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