CN112007625A - Alpha-alumina carrier, preparation method thereof, silver catalyst and application - Google Patents
Alpha-alumina carrier, preparation method thereof, silver catalyst and application Download PDFInfo
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- CN112007625A CN112007625A CN201910452543.XA CN201910452543A CN112007625A CN 112007625 A CN112007625 A CN 112007625A CN 201910452543 A CN201910452543 A CN 201910452543A CN 112007625 A CN112007625 A CN 112007625A
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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
- 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
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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
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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 catalysts, and relates to an alpha-alumina carrier, a preparation method thereof, a silver catalyst and application thereof. The alpha-alumina carrier is prepared by mixing, kneading, molding and roasting a solid mixture and a binder aqueous solution; the solid mixture is doped with waste silver catalyst carrier powder, and the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier; the median particle size of the waste silver catalyst carrier powder is 40-5000 meshes; the mass of the waste silver catalyst carrier powder accounts for 0.1-50.0% of the total mass of the solid mixture. The silver catalyst prepared by the carrier shows activity and selectivity equivalent to those of the silver catalyst prepared by the conventional method in the reaction of producing ethylene oxide by ethylene epoxidation. The invention realizes the effective utilization of waste resources, energy conservation and efficiency improvement.
Description
Technical Field
The invention belongs to the field of catalysts, and particularly relates to an alpha-alumina carrier, a preparation method thereof, a silver catalyst and application thereof, and more particularly relates to an alpha-alumina carrier prepared by using a recycled silver catalyst carrier, a method for preparing an alpha-alumina carrier by using a recycled silver catalyst carrier, an alpha-alumina carrier prepared by the method, a silver catalyst comprising the alpha-alumina carrier, and application of the alpha-alumina carrier and the silver catalyst in olefin epoxidation.
Background
To date, silver catalysts remain the only catalyst commercially effective for the epoxidation of ethylene to ethylene oxide. In the prior art, silver catalysts usually have, in addition to the silver component, one or more other elements co-deposited therewith for improving the catalytic performance of the silver catalyst on a carrier, which usually consists of alpha-alumina having a suitable specific surface and pore structure, which is resistant to high temperatures.
The materials of the alpha-alumina carrier for the preparation of the silver catalyst generally include: alpha-alumina powder and/or aluminum hydroxide, a binder, a thermally decomposable pore-forming agent, a lubricant and an auxiliary agent. The SD company patent discloses the preparation of an alpha-alumina carrier from at least one alpha-alumina hydration precursor and optionally alpha-alumina and a binder. PCT/US2003/005902 patent by Shell corporation discloses 50% to 95% by weight of first particulate alpha-alumina having a median pore diameter (d50) of 5 to 100 μm and 5% to 50% by weight of second particulate alpha-alumina having a median pore diameter of 1 to 10 μm smaller than d50 of said first particulate alpha-alumina. The alpha-alumina carrier prepared by Noritake company of Japan has a double-distribution pore diameter structure, and the research also researches that alpha-alumina with different particle sizes is used as a raw material and is kneaded and roasted at about 500 ℃ to prepare the alpha-alumina carrier.
After industrial application, the waste silver catalyst can be subjected to silver and auxiliary agent component recovery treatment to obtain the waste alpha-alumina carrier. In 2017, the total silver catalyst loading amount of China is about 6000m3It is expected that the total silver catalyst loading will be about 11000m in 20193. This results in a large amount of waste silver catalyst support to be treated or utilized. But no suitable method for recycling the waste silver catalyst carrier exists at present.
Disclosure of Invention
In view of the above-mentioned state of the art, as a result of extensive and intensive studies in the field of α -alumina supports and silver catalyst preparation, the present inventors crushed the recovered α -alumina support of the waste silver catalyst into α -alumina powder of a certain particle size, and selected this powder to prepare a silver catalyst support and a silver catalyst, which exhibit catalytic performance comparable to that of the existing catalysts in the reaction for preparing epoxy compounds by epoxidation of olefins. The invention realizes the recycling of waste carriers and makes full use of resources.
The invention provides an alpha-alumina carrier, which is prepared by mixing, kneading, molding and roasting a solid mixture and a binder aqueous solution; the solid mixture is doped with waste silver catalyst carrier powder, and the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier; the median particle size of the waste silver catalyst carrier powder is 40-5000 meshes; the mass of the waste silver catalyst carrier powder accounts for 0.1-50.0% of the total mass of the solid mixture.
The second aspect of the invention provides a preparation method of an alpha-alumina carrier, which comprises the following steps:
step I, crushing a waste silver catalyst carrier into alpha-alumina powder, wherein the median particle size of the alpha-alumina powder is 40-5000 meshes; the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier;
step II, obtaining a solid mixture comprising the following components: a. the alpha-alumina powder obtained in step I; b. alumina trihydrate; c. pseudo-boehmite; d. a fluorine-containing compound; e. an alkaline earth metal compound; wherein the mass of the alpha-alumina powder accounts for 0.1-50.0% of the total mass of the solid mixture;
step III, mixing the solid mixture obtained in the step II with a binder aqueous solution to obtain an alpha-alumina carrier precursor mixture;
and IV, kneading, molding and roasting the alpha-alumina carrier precursor mixture obtained in the step III to obtain the alpha-alumina carrier.
A third aspect of the present invention provides an α -alumina carrier obtained by the above-described production method.
A fourth aspect of the present invention provides a silver catalyst comprising the above-described alpha-alumina support and deposited thereon a catalytically effective amount of silver, optionally an alkali metal promoter and/or an alkaline earth metal promoter, and optionally a rhenium promoter and co-promoters thereof.
A fifth aspect of the present invention provides the use of an alpha-alumina support and/or a silver catalyst as described above in an olefin epoxidation reaction.
The method comprises the steps of adding waste silver catalyst alpha-alumina carrier powder in the preparation process of the alpha-alumina carrier, and controlling the performance of the prepared alpha-alumina carrier by adjusting the granularity and adding amount of the waste alpha-alumina carrier powder, wherein the specific surface area of the prepared carrier is 1.0-50.0 m2A preferred range is 1.1 to 10.0m2(ii)/g; the water absorption of the carrier is more than or equal to 30 percent, and preferably 40 to 70 percent; the crushing strength of the carrier is 30-300N/particle. The silver catalyst prepared by the carrier shows the reaction with ethylene oxide in the reaction of producing ethylene oxide by the epoxidation of ethyleneThe silver catalyst prepared by the conventional method has equivalent activity and selectivity. Therefore, the preparation method of the silver catalyst carrier realizes the effective utilization of waste resources, saves energy and improves efficiency.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present invention. 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 an alpha-alumina carrier, which is prepared by mixing, kneading, molding and roasting a solid mixture and a binder aqueous solution; the solid mixture is doped with waste silver catalyst carrier powder, and the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier; the median particle size of the waste silver catalyst carrier powder is 40-5000 meshes; the mass of the waste silver catalyst carrier powder accounts for 0.1-50.0% of the total mass of the solid mixture, preferably 0.1-40.0%, and more preferably 1.0-30.0%; according to a preferred embodiment of the present invention, the mass of the waste silver catalyst carrier powder accounts for 12.0-25.0% of the total mass of the solid mixture.
The waste silver catalyst used in the invention refers to a waste silver catalyst which can be used for olefin epoxidation reaction and takes alpha-alumina as a carrier, and correspondingly, the waste silver catalyst carrier refers to the carrier part left after the silver and the auxiliary agent are recovered from the waste silver catalyst. However, the present invention is not limited to the waste silver catalyst obtained by subjecting the catalyst having the above characteristics to an olefin epoxidation reaction.
Although the present invention is not limited to the specific sources of the "waste silver catalyst" and the "waste silver catalyst carrier", it preferably refers to a waste silver catalyst (generally referred to as "three wastes") obtained after an olefin epoxidation reaction is carried out in industry and a carrier part remaining after the silver catalyst is subjected to recovery of silver and auxiliary components. The specific recovery process of the present invention is not particularly limited, and any catalyst carrier may be used as long as it is a silver catalyst carrier remaining after recovery of the silver and the auxiliary components.
In the present invention, the terms "spent silver catalyst" and "recovered silver catalyst" are used synonymously; the meanings of the waste silver catalyst carrier, the recycled silver catalyst carrier and the waste alpha-alumina carrier are also the same.
According to the invention, the solid mixture also comprises other components required for preparing the silver catalyst carrier for olefin epoxidation, and specifically comprises the following components: alumina trihydrate, pseudo-boehmite, a fluorine-containing compound and an alkaline earth metal compound; wherein the content of the first and second substances,
the alumina trihydrate is preferably selected from gibbsite and/or bayer stone; the mass of the alumina trihydrate is preferably 5.0-85.0% of the total mass of the solid mixture, and more preferably 20.0-80.0%.
The mass of the pseudo-boehmite is preferably 2.0-75.0% of the total mass of the solid mixture, and more preferably 10.0-60.0%.
In the invention, alumina trihydrate and pseudo-boehmite are converted into transition phase alumina through roasting and dehydration, and finally converted into alpha-alumina. The fluorine-containing compound can promote the transition phase of alumina to alpha-alumina in the roasting process, eliminate unnecessary micropores and reduce the micropores below 0.1 mu m. The fluorine-containing compound is preferably selected from one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, lithium fluoride and cryolite; the amount of the fluorine-containing compound is preferably 0.01 to 20.0% by mass, more preferably 0.1 to 10.0% by mass, based on the total mass of the solid mixture.
In the present invention, the alkaline earth metal compound is added for the purpose of improving the properties of the α -alumina support. The alkaline earth metal compound is preferably selected from one or more of the oxides, sulfates, nitrates and oxalates of calcium, strontium and barium; the mass of the alkaline earth metal compound is preferably 0.01% to 6.00%, and more preferably 0.01% to 3.00% of the total mass of the solid mixture.
In the present invention, the aqueous binder solution acts to form an alumina sol with the pseudo-boehmite in the solid mixture, thereby binding the components together into an extrudable paste. The binder aqueous solution may be at least one selected from the group consisting of a citric acid aqueous solution, a nitric acid aqueous solution, a formic acid aqueous solution, an acetic acid aqueous solution, a propionic acid aqueous solution, and a hydrochloric acid aqueous solution. The amount of the aqueous binder solution and the amount of the binder contained therein are limited to meet the requirements for binding and forming an extrudable paste. Typically, the weight ratio of the aqueous binder solution to the solid mixture may be 1: 2-10; the mass ratio of the binder to water in the aqueous binder solution is preferably 1: 0.2 to 10.
In the present invention, the term "water" preferably means deionized water unless otherwise specified.
The mixing of the components of the solid mixture of the present invention with the aqueous binder solution can be carried out in any manner and need not be in any particular order.
In the preparation of the silver catalyst carrier of the present invention, the conditions for the kneading, molding and calcination may be those conventional in the art. For example, the kneading is carried out in a kneader, and the kneading time is 5-90 min; the molding is carried out in a molding machine, and the molded shape comprises a spherical shape, a Raschig ring shape, a porous cylindrical shape, a block shape, a pill shape, a clover shape or a clover shape; the drying is carried out at the temperature of 80-120 ℃; the roasting can comprise the processes of temperature programming and constant-temperature roasting, wherein the constant-temperature roasting temperature is 1100-1600 ℃, and the constant-temperature roasting time is 0.5-30 h, so that the alumina is basically and completely (for example, more than 90%) converted into the alpha-alumina.
The second aspect of the invention provides a preparation method of an alpha-alumina carrier, which comprises the following steps:
step I, crushing a waste silver catalyst carrier into alpha-alumina powder, wherein the median particle size of the alpha-alumina powder is 40-5000 meshes; the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier;
step II, obtaining a solid mixture comprising the following components: a. the alpha-alumina powder obtained in step I; b. alumina trihydrate; c. pseudo-boehmite; d. a fluorine-containing compound; e. an alkaline earth metal compound; wherein the mass of the alpha-alumina powder accounts for 0.1-50.0% of the total mass of the solid mixture, preferably 0.1-40.0%, and more preferably 1.0-30.0%; according to a preferred embodiment of the invention, the mass of the alpha-alumina powder is 12.0% to 25.0% of the total mass of the solid mixture;
step III, mixing the solid mixture obtained in the step II with a binder aqueous solution to obtain an alpha-alumina carrier precursor mixture;
and IV, kneading, molding and roasting the alpha-alumina carrier precursor mixture obtained in the step III to obtain the alpha-alumina carrier.
In the preparation method of the present invention, the specific components and amounts of the alumina trihydrate, the pseudo-boehmite, the fluorine-containing compound, the alkaline earth metal compound, and the aqueous binder solution are defined as above, and thus the details are not repeated herein.
In the preparation step of the silver catalyst carrier of the present invention, the conditions for the kneading, molding and firing may be those conventional in the art. The specific conditions are the same as those described above, and are not described herein again.
According to some embodiments of the present invention, in order to facilitate extrusion of the molded object, a molding aid including at least one of vaseline, graphite, paraffin, and vegetable oil may be added to the solid mixture.
A third aspect of the present invention provides an α -alumina carrier obtained by the above-described production method. The α -alumina support preferably has the following characteristics: the specific surface area is 1.0-50.0 m2A preferred range is 1.1 to 10.0m2(ii)/g; the water absorption rate is more than or equal to 30 percent, and is preferably 40 to 70 percent; the crushing strength is 30 to 300N/grain.
A fourth aspect of the present invention provides a silver catalyst comprising the above-described alpha-alumina support and deposited thereon a catalytically effective amount of silver, optionally an alkali metal promoter and/or an alkaline earth metal promoter, and optionally a rhenium promoter and co-promoters thereof.
The silver catalyst can be prepared by a preparation method comprising the following steps: soaking the alpha-alumina carrier in a solution containing organic amine, a silver compound and an auxiliary agent, and carrying out activation heat treatment to obtain a silver catalyst; the promoter comprises an optional alkali metal promoter and/or an alkaline earth metal promoter, and an optional rhenium promoter and a co-promoter thereof.
In the method for preparing the silver catalyst of the present invention, the organic amine may include at least one of pyridine, ethylamine, n-propylamine, n-butylamine, isobutylamine, tert-butylamine, sec-butylamine, 1, 2-propylenediamine, 1, 3-propylenediamine, ethylenediamine, 1, 2-butylenediamine, 1, 3-butylenediamine, ethanolamine, propanolamine, and butanolamine.
In the silver catalyst of the present invention, the mass content of the alkali metal promoter may be 5 to 2000ppm, the alkali metal promoter may be at least one selected from nitrates, sulfates and hydroxides of alkali metals, and the alkali metal may be at least one selected from lithium, sodium, potassium, rubidium and cesium.
In the silver catalyst of the present invention, the mass content of the alkaline earth metal promoter may be 5 to 20000ppm, the alkaline earth metal promoter may be at least one selected from acetate, oxalate, sulfate and nitrate of an alkaline earth metal, and the alkaline earth metal may be at least one selected from magnesium, calcium, strontium and barium.
In some embodiments of the invention, the silver catalyst may further comprise other elements deposited on the alpha-alumina support, the other elements including at least one of phosphorus, boron, chromium, and titanium.
In order to obtain a silver catalyst with a higher silver content and/or promoter content, in the method for preparing a silver catalyst according to the present invention, the silver catalyst may be prepared by one or more impregnation processes. The promoter for the silver catalyst may be deposited on the support either before, simultaneously with or after impregnation of the silver, or after the silver compound has been activated.
In the present invention, specific impregnation conditions and conditions of activation heat treatment are not particularly limited, and may be any conditions that are conventional in the art.
A fifth aspect of the present invention provides the use of an alpha-alumina support and/or a silver catalyst as described above in an olefin epoxidation reaction. For example, a process for producing an epoxy compound by the epoxidation of an olefin, the epoxidation of the olefin is carried out in the presence of the above-mentioned silver catalyst. The olefins include, but are not limited to, at least one of styrene, propylene, ethylene, and 1, 3-butadiene.
The present invention will be further described with reference to the following examples, but the scope of the present invention is not limited to these examples.
The median particle size of the alpha-alumina powders of the present invention was determined using a laser particle sizer.
The detection method of the various physical properties of the alpha-alumina carrier comprises the following steps:
specific surface area of the support: measured using a nitrogen physisorption BET method according to International test Standard ISO-9277 using a model NOVA2000e, Congta, USA.
Side pressure strength of carrier: and (3) selecting 30 carrier samples randomly by adopting a DL II type intelligent particle strength tester produced by the large chemical research and design institute, and measuring the radial crushing strength and then averaging to obtain the radial crushing strength.
The term "water absorption" as used in the present invention refers to the volume of saturated adsorbed water per unit mass of the carrier, in mL/g. The measurement method is as follows: first, a certain amount of carrier (assuming its mass m) is weighed1) Boiling in boiling water for 1 hr, taking out the carrier, standing on wet gauze with moderate water content to remove excessive water on the surface of the carrier, and weighing the mass of the carrier after water adsorption (assuming that m is m)2) The water absorption of the carrier was calculated by the following formula. Water absorption rate of (m)2-m1)/m1/ρWater (W)Wherein: rhoWater (W)The density of water at temperature and atmospheric pressure was measured.
Various silver catalysts of the present invention were tested for selectivity using a laboratory microreactor ("microreaction") evaluation unit. The reactor used in the microreactor evaluation apparatus was a stainless steel reaction tube having an inner diameter of 4mm, which was placed in a heating mantle. The filling volume of the catalyst is 1ml, and the lower part of the catalyst is provided with inert filler, so that a catalyst bed layer is positioned in a constant temperature area of the heating sleeve.
The assay conditions for the activity and initial selectivity employed in the present invention are shown in table 1:
TABLE 1
The reactor inlet and outlet gas compositions were continuously measured after the above reaction conditions were stably achieved. The selectivity was calculated after volume shrinkage correction of the measurement results according to the following formula:
selectivity is
Where Δ EO is the difference in ethylene oxide concentration between the reactor outlet gas and the inlet gas, Δ CO2The carbon dioxide concentration difference between the outlet gas and the inlet gas of the reactor is determined, and the average of more than 10 groups of test data is taken as the test result of the day.
Comparative example 1
Preparation of an alpha-alumina carrier: 300.0g of gibbsite, 150.0g of pseudo-boehmite, 8.5g of aluminum fluoride and 2.5g of barium nitrate are put into a mixer to be uniformly mixed, transferred into a kneader, added with 100 ml of dilute nitric acid (nitric acid: water is 1: 3, volume ratio) and kneaded into paste which can be extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then putting the dried five-hole column into a bell jar kiln for roasting at 1200 ℃, roasting at constant temperature for 2h, and finally cooling to room temperature to obtain the alpha-alumina carrier named as C-1. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: respectively dissolving 700g of silver nitrate and 325g of ammonium oxalate in 750ml of deionized water and 250ml of deionized water to respectively obtain a silver nitrate solution and an ammonium oxalate solution, mixing the two solutions under vigorous stirring to generate a white silver oxalate precipitate, aging for 30min, filtering, and washing the precipitate with deionized water until no nitrate ions exist. The mass content of silver in the filter cake is about 60 percent, the mass content of water is about 15 percent, and the filter cake is pasty. 300.0g of ethylenediamine, 110.0g of ethanolamine and 375.0g of deionized water were added to a stirred glass flask to obtain a mixed solution, and the silver oxalate paste prepared above was continuously added with stirring, and the temperature was maintained below 40 ℃ to completely dissolve the silver oxalate. Then, 2.5g of cesium nitrate, 3.0g of barium acetate and 0.6g of ammonium perrhenate are sequentially added, deionized water is added to enable the total mass of the solution to reach 2000g, and the solution is uniformly mixed to prepare an impregnation solution for later use. 100g of the support is taken and placed in a glass vessel capable of being evacuated, the prepared impregnation solution is poured to completely immerse the support, the vacuum is applied to less than 10mmHg for about 15min, and then the excess solution is leached away. Finally, the impregnated carrier sample is placed in air at 340 ℃ for heating for 3min and cooled to prepare the silver catalyst.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
Example 1
Preparation of an alpha-alumina carrier: crushing a waste silver catalyst carrier into alpha-alumina powder with the median particle size of 4000 meshes, putting 10g of alpha-alumina powder, 290.0g of gibbsite, 150.0g of pseudo-boehmite, 8.5g of aluminum fluoride and 2.5g of barium nitrate into a mixer, uniformly mixing, transferring into a kneader, adding 100 ml of dilute nitric acid (nitric acid: water is 1: 3, volume ratio), and kneading into paste capable of being extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then putting the dried five-hole column into a bell jar kiln for roasting at 1200 ℃, roasting at constant temperature for 2h, and finally cooling to room temperature to obtain the alpha-alumina carrier named as S-1. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: the procedure for preparing the silver catalyst was the same as in comparative example 1.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
Example 2
Preparation of an alpha-alumina carrier: crushing a waste silver catalyst carrier into alpha-alumina powder with the median particle size of 2000 meshes, putting 50g of alpha-alumina powder, 250.0g of gibbsite, 150.0g of pseudo-boehmite, 8.5g of aluminum fluoride and 2.5g of barium nitrate into a mixer, uniformly mixing, transferring into a kneader, adding 100 ml of dilute nitric acid (nitric acid: water is 1: 3, volume ratio), and kneading into paste capable of being extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then putting the dried five-hole column into a bell jar kiln for roasting at 1200 ℃, roasting at constant temperature for 2h, and finally cooling to room temperature to obtain the alpha-alumina carrier named as S-2. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: the procedure for preparing the silver catalyst was the same as in comparative example 1.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
Comparative example 2
Preparation of an alpha-alumina carrier: 200.0g of bayer stone, 200.0g of pseudo-boehmite, 8.0g of aluminum fluoride and 1.5g of barium sulfate are put into a mixer to be uniformly mixed, transferred into a kneader, added with 100 ml of dilute nitric acid (nitric acid: water: 1: 3, volume ratio) and kneaded into paste which can be extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then placing the dried five-hole column into a bell jar kiln for roasting, wherein the roasting temperature is 1350 ℃, roasting at a constant temperature for 10 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier named as C-2. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: respectively dissolving 700g of silver nitrate and 325g of ammonium oxalate in 750m of deionized water and 250ml of deionized water to respectively obtain silver nitrate solution and ammonium oxalate solution, mixing the two solutions under vigorous stirring to generate white silver oxalate precipitate, aging for 30min, filtering, and washing the precipitate with deionized water until no nitrate ions exist. The mass content of silver in the filter cake is about 60 percent, the mass content of water is about 15 percent, and the filter cake is pasty. 300.0g of ethylenediamine, 110.0g of ethanolamine and 375.0g of deionized water were added to a stirred glass flask to obtain a mixed solution, and the silver oxalate paste prepared above was continuously added with stirring, and the temperature was maintained below 40 ℃ to completely dissolve the silver oxalate. Then adding 3.0g of cesium acetate, 3.5g of barium acetate and 0.6g of ammonium perrhenate in sequence, adding deionized water to enable the total mass of the solution to reach 2000g, and uniformly mixing to prepare an impregnation solution for later use. 100g of the support is taken and placed in a glass vessel capable of being evacuated, the prepared impregnation solution is poured to completely immerse the support, the vacuum is applied to less than 10mmHg for about 15min, and then the excess solution is leached away. Finally, the impregnated carrier sample is placed in air at 340 ℃ for heating for 3min and cooled to prepare the silver catalyst.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
Example 3
Preparation of an alpha-alumina carrier: crushing a waste silver catalyst carrier into alpha-alumina powder with the median particle size of 700 meshes, putting 100g of alpha-alumina powder, 100.0g of bayer stone, 200.0g of pseudo-boehmite, 8.0g of aluminum fluoride and 1.5g of barium sulfate into a mixer, uniformly mixing, transferring into a kneader, adding 100 ml of dilute nitric acid (nitric acid: water: 1: 3, volume ratio), and kneading into paste capable of being extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then placing the dried five-hole column into a bell jar kiln for roasting, wherein the roasting temperature is 1350 ℃, roasting at a constant temperature for 10 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier which is named as S-3. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: the procedure for preparing the silver catalyst was the same as in comparative example 1.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
Example 4
Preparation of an alpha-alumina carrier: crushing a waste silver catalyst carrier into alpha-alumina powder with the median particle size of 1000 meshes, putting 60g of alpha-alumina powder, 140.0g of bayer stone, 200.0g of pseudo-boehmite, 8.0g of aluminum fluoride and 1.5g of barium sulfate into a mixer, uniformly mixing, transferring into a kneader, adding 100 ml of dilute nitric acid (nitric acid: water is 1: 3, volume ratio), and kneading into paste capable of being extruded and molded. And finally, putting the paste into a forming machine, extruding the paste into a five-hole column, and drying the five-hole column for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to be less than 10%. And then placing the dried five-hole column into a bell jar kiln for roasting, wherein the roasting temperature is 1300 ℃, roasting at a constant temperature for 10 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier which is named as S-4. The relevant physical property data of this support are shown in table 2.
Preparation of silver catalyst: the procedure for preparing the silver catalyst was the same as in comparative example 1.
Evaluation of silver catalyst: the activity and selectivity of the catalyst were measured using a microreactor evaluation means under the aforementioned process conditions for the resulting catalyst, and the test results are shown in Table 3.
TABLE 2
| Specific surface area (m)2/g) | Strength (N/grain) | Water absorption (%) | |
| Comparative example 1 | 1.20 | 151 | 52.1 |
| Example 1 | 1.17 | 130 | 52.7 |
| Example 2 | 1.21 | 125 | 51.8 |
| Comparative example 2 | 1.49 | 217 | 52.4 |
| Example 3 | 1.45 | 184 | 51.7 |
| Example 4 | 1.57 | 157 | 53.1 |
TABLE 3
| Initial selectivity (%) | Initial reaction temperature (. degree. C.) | |
| Comparative example 1 | 82.4 | 228.5 |
| Example 1 | 82.3 | 227.7 |
| Example 2 | 82.6 | 228.3 |
| Comparative example 2 | 81.9 | 226.7 |
| Example 3 | 82.4 | 226.5 |
| Example 4 | 83.1 | 225.1 |
It can be seen from comparing the data in tables 2 and 3 that the recovered alpha-alumina carrier of the waste silver catalyst is crushed into alpha-alumina powder with a certain particle size, and the silver catalyst carrier prepared by using the powder has a slightly reduced strength, but still can meet the strength requirement of the silver catalyst carrier for industrial application, and the silver catalyst prepared by using the carrier has the same good catalytic performance in the reaction of preparing epoxy compounds by ethylene epoxidation.
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 ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
Claims (12)
1. The alpha-alumina carrier is characterized in that the alpha-alumina carrier is prepared by mixing, kneading, molding and roasting a solid mixture and a binder aqueous solution; the solid mixture is doped with waste silver catalyst carrier powder, and the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier; the median particle size of the waste silver catalyst carrier powder is 40-5000 meshes; the mass of the waste silver catalyst carrier powder accounts for 0.1-50.0% of the total mass of the solid mixture, preferably 0.1-40.0%, and more preferably 1.0-30.0%.
2. The alpha-alumina support according to claim 1, wherein the solid mixture further comprises: alumina trihydrate, pseudo-boehmite, a fluorine-containing compound and an alkaline earth metal compound; wherein the content of the first and second substances,
the alumina trihydrate is preferably selected from gibbsite and/or bayer stone; the mass of the alumina trihydrate is preferably 5.0-85.0% of the total mass of the solid mixture, and more preferably 20.0-80.0%;
the mass of the pseudo-boehmite is preferably 2.0-75.0% of the total mass of the solid mixture, and more preferably 10.0-60.0%;
the fluorine-containing compound is preferably selected from one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, lithium fluoride and cryolite; the mass of the fluorine-containing compound is preferably 0.01 to 20.0% of the total mass of the solid mixture, and more preferably 0.1 to 10.0%;
the alkaline earth metal compound is preferably selected from one or more of the oxides, sulfates, nitrates and oxalates of calcium, strontium and barium; the mass of the alkaline earth metal compound is preferably 0.01 to 6.00 percent of the total mass of the solid mixture, and more preferably 0.01 to 3.00 percent;
the aqueous binder solution is preferably at least one selected from the group consisting of an aqueous citric acid solution, an aqueous nitric acid solution, an aqueous formic acid solution, an aqueous acetic acid solution, an aqueous propionic acid solution, and an aqueous hydrochloric acid solution, and the mass ratio of the binder to water in the aqueous binder solution is preferably 1: 0.2 to 10.
3. A preparation method of an alpha-alumina carrier comprises the following steps:
step I, crushing a waste silver catalyst carrier into alpha-alumina powder, wherein the median particle size of the alpha-alumina powder is 40-5000 meshes; the silver catalyst is a silver catalyst for olefin epoxidation with alpha-alumina as a carrier;
step II, obtaining a solid mixture comprising the following components: a. the alpha-alumina powder obtained in step I; b. alumina trihydrate; c. pseudo-boehmite; d. a fluorine-containing compound; e. an alkaline earth metal compound; wherein the mass of the alpha-alumina powder accounts for 0.1-50.0% of the total mass of the solid mixture, preferably 0.1-40.0%, and more preferably 1.0-30.0%;
step III, mixing the solid mixture obtained in the step II with a binder aqueous solution to obtain an alpha-alumina carrier precursor mixture;
and IV, kneading, molding and roasting the alpha-alumina carrier precursor mixture obtained in the step III to obtain the alpha-alumina carrier.
4. The method for producing an α -alumina support according to claim 3, wherein the alumina trihydrate is gibbsite and/or bayer alumina; the mass of the alumina trihydrate accounts for 5.0-85.0% of the total mass of the solid mixture, and preferably 20.0-80.0%.
5. The method for preparing an alpha-alumina carrier according to claim 3, wherein the mass of the pseudoboehmite is 2.0-75.0%, preferably 10.0-60.0% of the total mass of the solid mixture.
6. The method for preparing an alpha-alumina carrier according to claim 3, wherein the fluorine-containing compound is selected from one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, lithium fluoride and cryolite; the mass of the fluorine-containing compound accounts for 0.01-20.0% of the total mass of the solid mixture, and preferably 0.1-10.0%.
7. The method for preparing an alpha-alumina carrier according to claim 3, wherein the alkaline earth metal compound is selected from one or more of oxides, sulfates, nitrates and oxalates of calcium, strontium and barium; the mass of the alkaline earth metal compound accounts for 0.01-6.00%, preferably 0.01-3.00% of the total mass of the solid mixture.
8. The method for producing an α -alumina support according to claim 3, wherein the aqueous binder solution is at least one selected from the group consisting of an aqueous citric acid solution, an aqueous nitric acid solution, an aqueous formic acid solution, an aqueous acetic acid solution, an aqueous propionic acid solution and an aqueous hydrochloric acid solution, and the mass ratio of the binder to water in the aqueous binder solution is 1: 0.2 to 10.
9. The method for preparing an α -alumina support according to any one of claims 3 to 8, wherein the calcination is carried out at a temperature of 1100 to 1600 ℃ for a time of 0.5 to 30 hours.
10. The preparation method of any one of claims 3 to 8The alpha-alumina carrier prepared by the method; the α -alumina support preferably has the following characteristics: the specific surface area is 1.0-50.0 m2A preferred range is 1.1 to 10.0m2(ii)/g; the water absorption rate is more than or equal to 30 percent, and is preferably 40 to 70 percent; the crushing strength is 30 to 300N/grain.
11. A silver catalyst comprising an alpha-alumina support according to any one of claims 1 to 2 and 10 and deposited thereon a catalytically effective amount of silver, optionally an alkali metal promoter and/or an alkaline earth metal promoter, and optionally a rhenium promoter and co-promoters thereof.
12. Use of an alpha-alumina support according to any one of claims 1 to 2 and 10 and/or a silver catalyst according to claim 11 in the epoxidation of an olefin.
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