阅读说明：本技术 一种α-氧化铝载体、乙烯环氧化用银催化剂及乙烯氧化方法 (α -alumina carrier, silver catalyst for ethylene epoxidation and ethylene oxidation method ) 是由 魏会娟 廉括 王辉 曹淑媛 李金兵 代武军 汤之强 王祎 隗永清 马坤 于 2019-01-16 设计创作，主要内容包括：本发明属于催化剂领域,涉及一种α-氧化铝载体、乙烯环氧化用银催化剂及乙烯氧化方法。该α-氧化铝载体通过包括如下步骤的方法制得：S1.获得具有如下组分的固体混合物：假一水A1<Sub>2</Sub>O<Sub>3</Sub>、组分A、可燃尽固体润滑材料和碱土金属化合物,然后将所述固体混合物与粘结剂和任选的水混合,得到混合物；其中,组分A为假一水A1<Sub>2</Sub>O<Sub>3</Sub>经氟化物处理后的焙烧产物或者假一水A1<Sub>2</Sub>O<Sub>3</Sub>经氟化物处理后的焙烧产物和三水α-A1<Sub>2</Sub>O<Sub>3</Sub>；S2.将步骤S1中所得的混合物进行成型；S3.将步骤S2中所得的成型体进行干燥和焙烧。与现有技术相比,本发明的α-氧化铝载体制成的银催化剂用于乙烯氧化生产环氧乙烷的反应时,具有活性和选择性更高的优点。(The invention belongs to the field of catalysts, and relates to an α -alumina carrier, a silver catalyst for ethylene epoxidation and an ethylene oxidation method, wherein the α -alumina carrier is prepared by the following steps of S1, obtaining a solid mixture containing pseudo-monohydrate A1 2 O 3 A component A, a burnable solid lubricating material and an alkaline earth metal compound, and then mixing the solid mixture with a binder and optionally water to obtain a mixture; wherein the component A is pseudo-monohydrate A1 2 O 3 Calcined product or false product after fluoride treatmentWater A1 2 O 3 The roasted product after fluoride treatment and trihydrate α -A1 2 O 3 S2, forming the mixture obtained in the step S1, and S3, drying and roasting the formed body obtained in the step S2. compared with the prior art, the silver catalyst prepared by the α -alumina carrier has the advantages of higher activity and selectivity when used for the reaction of producing ethylene oxide by ethylene oxidation.)

1. An α -alumina carrier, wherein the α -alumina carrier is prepared by a method comprising the following steps:

s1, obtaining a solid mixture with the following components: pseudo-water A1₂O₃A component A, a burnable solid lubricating material and an alkaline earth metal compound, and then mixing the solid mixture with a binder and optionally water to obtain a mixture; wherein the component A is pseudo-monohydrate A1₂O₃Calcined product or pseudo-monohydrate A1 after fluoride treatment₂O₃The roasted product after fluoride treatment and trihydrate α -A1₂O₃；

S2, molding the mixture obtained in the step S1 to obtain a molded body;

s3, drying and roasting the formed body obtained in the step S2 to obtain the α -alumina carrier.

2.α -alumina carrier according to claim 1, wherein the pseudo-monohydrate A1₂O₃The roasted product after fluoride treatment is pseudo-monohydrate A1₂O₃Roasting at 500-1000 ℃ after fluoride treatment to obtain a product; the pseudo-water A1₂O₃The amount of the baked product after fluoride treatment is 0.1 to 100 wt%, preferably 50 to 100 wt% of the total amount of the component A.

3.α -alumina carrier according to claim 1, wherein the pseudo-monohydrate A1₂O₃The fluoride treatment is carried out by impregnating pseudo-monohydrate A1 with aqueous or acidic fluoride solutions₂O₃(ii) a The fluoride is at least one of hydrogen fluoride, ammonium fluoride and magnesium fluoride; the fluoride is used in the amount of pseudo-monohydrate A1₂O₃0.05 to 20 wt%, preferably 0.5 to 10 wt% of the weight before impregnation.

4.α -alumina carrier according to claim 1, wherein the pseudo-monohydrate A1 is based on the total weight of the solid mixture₂O₃The amount of (B) is 10 to 55 wt%, preferably 15 to 45 wt%; the amount of the component A is 40-85 wt%, preferably 55-80 wt%; the using amount of the burnout solid lubricating material is 0.01-10 wt%, preferably 0.01-5 wt%; the amount of the alkaline earth metal compound is 0.01 to 8 wt%, preferably 0.05 to 5 wt%; the addition amount of the binder is 25-60 wt% of the total weight of the solid mixture.

5.α -alumina support according to claim 1, wherein the solid mixture is free of fluoride mineralizers.

6.α -alumina carrier according to claim 1, wherein the pseudo-monohydrate A1₂O₃The particle size of the pseudo-monohydrate A1 is 1-120 mu m₂O₃The particle size of the roasted product after fluoride treatment is 1-120 mu m, and the trihydrate α -A1₂O₃The particle size of (A) is 25 to 300 μm.

7. The α -alumina carrier of claim 1, wherein the burnout solid lubricant is at least one of petroleum coke, carbon powder, graphite, and vaseline, and the alkaline earth metal compound is at least one of strontium and/or barium oxide, nitrate, acetate, oxalate, and sulfate.

8.α -alumina carrier according to claim 1, wherein the binder is an acid provided in the form of an aqueous acid solution, preferably an aqueous nitric acid solution, with a weight ratio of nitric acid to water of 1 (1.25-10).

9.α -alumina carrier according to claim 1, wherein the binder and pseudo-monohydrate A1₂O₃All or part of the aluminum sol is provided in the form of an aluminum sol.

10. The α -alumina carrier of any one of claims 1-9, wherein the α -alumina carrier is characterized by α -A1₂O₃The content is more than 90 weight percent, and the crushing strength is 40-200N/particle, preferably 50-160N/particle; the specific surface area is 0.3-2.0 m²A preferred range is 0.5 to 1.8 m/g²(ii)/g; the water absorption rate is 30-80%, and preferably 40-70%; the pore volume is 0.30-0.85 ml/g, preferably 0.40-0.75 ml/g; the average crystal size is 1.0 to 8.0 μm, preferably 3.0 to 6.0. mu.m.

11. A silver catalyst for ethylene epoxidation, comprising a carrier and an active component silver supported on the carrier, characterized in that the carrier is the α -alumina carrier of any one of claims 1-10.

12. The silver catalyst for the epoxidation of ethylene according to claim 11, wherein said silver catalyst further comprises:

alkali and/or alkaline earth metals or compounds based on alkali and/or alkaline earth metals;

rhenium metal and/or rhenium-based compounds; and

optionally, a rhenium co-promoter, selected from at least one metal of chromium, molybdenum, tungsten and manganese, and/or from a compound based on at least one metal of chromium, molybdenum, tungsten and manganese.

13. A method for oxidizing ethylene, which comprises subjecting ethylene to epoxidation reaction under the action of the α -alumina carrier of any one of claims 1-10 and/or the silver catalyst of claim 11 or 12 to obtain ethylene oxide.

Technical Field

The invention belongs to the field of catalysts, and particularly relates to an α -alumina carrier, a silver catalyst prepared from the same and an ethylene oxidation method, in particular to a α -alumina carrier for a silver catalyst for producing ethylene oxide by oxidizing ethylene, a silver catalyst prepared from the carrier, and a method for producing ethylene oxide by oxidizing ethylene by using the catalyst.

Background

Under the action of silver catalyst, ethylene is oxidized to produce ethylene oxide, and side reaction to produce carbon dioxide, water, etc. Activity, selectivity and stability are the main performance indicators of silver catalysts. Wherein the activity generally refers to the reaction temperature required when the ethylene oxide production process reaches a certain reaction load, and the lower the reaction temperature is, the higher the activity of the catalyst is; selectivity refers to the ratio of moles of ethylene converted to ethylene oxide in the reaction to the total reacted moles of ethylene; stability is expressed as the rate of decline of activity and selectivity, the smaller the rate of decline, the better the catalyst stability. At present, the silver catalyst can be mainly divided into three types, namely, the silver catalyst with high activity, high selectivity and medium selectivity. Because of the increasing shortage of petroleum resources and the requirement of energy conservation, silver catalysts with high selectivity and medium selectivity are widely applied to industrial production in recent years and replace the original high-activity silver catalysts.

The performance of the silver catalyst is not only important in the composition and preparation method of the catalyst, but also important in the performance and preparation method of the carrier used by the catalyst, at present, α -alumina is generally selected as the carrier of the silver catalyst, indexes for measuring the performance of α -alumina mainly comprise the specific surface area, pore volume, water absorption rate, compressive strength and the like of the carrier, the proper specific surface area provides positions for deposition of active components and auxiliaries, the proper pore volume provides a proper space for ethylene oxidation, so that reaction heat is dissipated timely, the proper water absorption rate can control the loading capacity of the active components and the catalytic auxiliaries on the carrier, and the proper crushing strength can ensure that the catalyst can bear reaction pressure for a long time.

Disclosure of Invention

The object of the present invention is to overcome the above-mentioned drawbacks of the prior art by providing a α -alumina carrier, a silver catalyst for ethylene epoxidation and a method for ethylene oxidation, wherein the α -alumina carrier of the present invention shows good activity and selectivity in the process of ethylene oxidation to ethylene oxide after being supported with silver and preferably various active components to form a silver catalyst.

In view of the above-mentioned state of the art, the inventors of the present invention have conducted extensive and intensive studies in the field of preparation of silver catalysts and carriers therefor, and as a result, found that pseudomonohydrate a1₂O₃The product calcined at a certain temperature after fluoride treatment is used as a raw material for preparing the carrier instead of or partially replacing the hydrate of alumina, the crystal morphology and size, specific surface area, water absorption and pore volume of the finished carrier can be adjusted, and the activity and selectivity of the silver catalyst prepared by the carrier are obviously improved when the silver catalyst is used for preparing ethylene oxide by ethylene oxidation.

In a first aspect the present invention provides an α -alumina carrier, the α -alumina carrier being prepared by a process comprising the steps of:

s1, obtaining a solid mixture with the following components: pseudo-water A1₂O₃A component A, a burnable solid lubricating material and an alkaline earth metal compound, and then mixing the solid mixture with a binder and optionally water to obtain a mixture; wherein the component A is pseudo-monohydrate A1₂O₃Calcined product or pseudo-monohydrate A1 after fluoride treatment₂O₃The roasted product after fluoride treatment and trihydrate α -A1₂O₃；

S2, molding the mixture obtained in the step S1 to obtain a molded body;

s3, drying and roasting the formed body obtained in the step S2 to obtain the α -alumina carrier.

The second aspect of the invention provides a silver catalyst for ethylene epoxidation, which comprises a carrier and an active component silver loaded on the carrier, wherein the carrier is the α -alumina carrier provided by the invention.

In a third aspect, the invention provides an ethylene oxidation method, which comprises the step of carrying out ethylene epoxidation reaction on ethylene under the action of the α -alumina carrier provided by the invention and/or the silver catalyst provided by the invention to obtain ethylene oxide.

According to the invention, pseudo-water A1 is added₂O₃Compared with the prior art, the silver catalyst prepared from the α -alumina carrier has the advantages of higher activity and selectivity when used for the reaction of producing ethylene oxide by oxidizing ethylene.

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 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.

In a first aspect the present invention provides an α -alumina carrier, the α -alumina carrier being prepared by a process comprising the steps of:

s1, obtaining a solid mixture with the following components: pseudo-water A1₂O₃A component A, a burnable solid lubricating material and an alkaline earth metal compound, and then mixing the solid mixture with a binder and optionally water to obtain a mixture; wherein the component A is pseudo-monohydrate A1₂O₃Calcined product or pseudo-monohydrate A1 after fluoride treatment₂O₃The roasted product after fluoride treatment and trihydrate α -A1₂O₃；

S2, molding the mixture obtained in the step S1 to obtain a molded body;

s3, drying and roasting the formed body obtained in the step S2 to obtain the α -alumina carrier.

The inventor of the invention finds that the three-water α -A1₂O₃Pseudo-water A1₂O₃With pseudo-water A1₂O₃The coordination of the roasted product after fluoride treatment can adjust the crystal morphology and size, specific surface area, water absorption and pore volume of the finished product carrier; thereby being beneficial to improving the activity and the selectivity of the obtained catalyst.

In the present invention, "optional water" means that water may or may not be added, and water herein means water added additionally, excluding water contained in other components as such.

According to a preferred embodiment of the invention, said pseudo-monohydrate A1₂O₃The roasted product after fluoride treatment is pseudo-monohydrate A1₂O₃And roasting at 500-1000 ℃ after fluoride treatment to obtain the product. Wherein the pseudo-water A1₂O₃The fluoride treatment mode is impregnation by using an aqueous fluoride solution or an acid solution, and the fluoride is one or more of hydrogen fluoride, ammonium fluoride and magnesium fluoride; the fluoride is used in the amount of pseudo-monohydrate A1₂O₃0.05 to 20 wt%, preferably 0.5 to 10 wt% of the weight before impregnation. The pseudo-water A1₂O₃After fluoride treatment and when calcined, in pseudo-monohydrate A1₂O₃During the process of converting into gamma-alumina, fluorine ions can enter into alumina crystal lattices to form solid solutions, and the energy state of the crystal lattices is changed when pseudo-water A1 is used₂O₃After fluoride treatment, when the roasting is carried out at different temperatures of 500-1000 ℃, the crystal phase state of the roasted product is obviously different, preferably, the roasting is carried out at 500-800 ℃, and the pseudo-monohydrate A1₂O₃The addition of the calcined product treated by the fluoride can change the crystal phase composition and the particle size distribution of the raw materials for preparing the carrier, influence the crystal phase change of alumina in the carrier, change the crystal morphology and the size of the carrier, influence the physical properties of the carrier such as specific surface area, pore volume, water absorption and the like, and further influence the performance of the silver catalyst. Preferably, the pseudo-water A1₂O₃The particle size of the roasted product after fluoride treatment is 1-120 mu m.

Although only the pseudo-monohydrate A1 was added₂O₃The roasted product treated by fluoride can achieve the purpose of the invention, but from the viewpoint of further improving higher activity and selectivity of the silver catalyst prepared by the alumina carrier when being applied to the reaction for producing ethylene oxide by ethylene oxidation, the component A is used in an amount of 40-85 wt%, preferably 55-80 wt% based on the total amount of solid components in the mixture. The pseudo-water A1₂O₃By treatment with fluorideThe amount of the roasted product is 0.1-100 wt%, preferably 50-100 wt% of the total amount of the component A.

According to a preferred embodiment of the invention, said component A may be pseudo-monohydrate A1₂O₃The roasted product after fluoride treatment and trihydrate α -A1₂O₃The trihydrate α -A1₂O₃Dehydration and crystal transformation into α -A1 in the high-temperature roasting process₂O₃Preferably, the trihydrate α -A1₂O₃The particle size of (A) is 25 to 300 μm.

According to a preferred embodiment of the invention, the pseudo-monohydrate A1 is present in an amount based on the total weight of the solid mixture₂O₃The amount is 10 to 55 wt%, preferably 15 to 45 wt%. Preferably, the pseudo-water A1₂O₃The particle size of (A) is 1 to 120 μm. The pseudo-water A1₂O₃Reacting with acid during binder addition such as acid kneading, converting into sol, acting as binder, and converting into stable α -A1 during high temperature calcination₂O₃Is α -A1₂O₃A portion of a carrier. According to the invention, the binder and pseudo-monohydrate A1 are added₂O₃Generating aluminum sol, and bonding the components together to form paste which can be extruded and molded. The addition amount of the binder can be the conventional amount in the field, and particularly preferably, the addition amount of the binder is 25 to 60 weight percent of the total weight of the solid mixture based on the total weight of the solid mixture. In the present invention, the type of binder is well known to those skilled in the art and includes, for example, an acid, which is generally provided in the form of an aqueous acid solution, preferably an aqueous nitric acid solution, wherein the weight ratio of nitric acid to water in the aqueous nitric acid solution is preferably 1 (1.25-10).

According to one embodiment of the invention, the components are bonded together in the course of the kneading of the mixture to give an extrudable paste, in order to also function as a binder, the binder and the pseudo-water A1₂O₃All or part of the aluminum sol is provided in the form of an aluminum sol.

According to a preferred embodiment of the present invention, the combustible solid lubricant is added to facilitate molding and granulation of the kneaded material, and oxidation reaction occurs during calcination of the material, resulting in escape of generated gas, and no or as little impurities as possible are introduced during the preparation of the carrier, thereby not affecting the performance of the catalyst. The burnout solid lubricating material can be various burnout solid lubricating materials used for preparing the alumina carrier in the field, preferably one or more of petroleum coke, carbon powder, graphite and vaseline, and the burnout solid lubricating material is used in an amount of 0.01-10 wt%, preferably 0.01-5 wt%, based on the total weight of the solid mixture.

According to a preferred embodiment of the invention, the alkaline earth metal compound is one or more of oxides, nitrates, acetates, oxalates and sulfates of strontium and/or barium, which act to modify the properties of the support.

Preferably, the alkaline earth metal compound is used in an amount of 0.01 to 8 wt%, more preferably 0.05 to 5 wt%, based on the total weight of the solid mixture.

According to the present invention, the solid mixture is free of fluoride mineralizers, which is meant herein to mean that the fluoride mineralizers are not added separately when the solid mixture is prepared.

According to the present invention, in step S2, the mixture obtained in step S1 is kneaded to obtain a paste, and then the paste is extrusion-molded to obtain a molded body, which can be performed according to the conventional technique in the art. Wherein, the shape of the formed body can be annular, spherical, cylindrical or porous cylindrical.

According to the present invention, the drying and calcination processes in the step S3 can be performed in a conventional manner in the art, preferably, the molded body can be dried to contain less than 10 wt% of free water, the drying temperature can be 80 to 120 ℃, the drying time can be controlled to 1 to 24 hours according to the moisture content, and the calcination converts the alumina into α -A1₂O₃The roasting time can be 1-20 hours, preferably 2-15 hoursThe highest roasting temperature can be 1200-1500 ℃, and the alumina is completely converted into α -A1 by roasting₂O₃。

According to one embodiment of the present invention, the preparation method of the α -alumina carrier of the silver catalyst for ethylene epoxidation provided by the present invention comprises the following steps:

s1, preparing a solid mixture with the following composition:

a) based on the total weight of the solid mixture, the pseudo-monohydrate A1 with the particle size of 1-120 mu m is used in an amount of 10-55 wt%₂O₃；

b) Based on the total weight of the solid mixture, the total amount of the solid mixture is 40-85 wt% of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃And pseudo-monohydrate A1 having a particle size of 1 to 120 μm₂O₃A calcined product after fluoride treatment;

c) using trihydrate α -A1₂O₃With pseudo-water A1₂O₃The calcined product after fluoride treatment contains 0.1-100 wt% of pseudo-monohydrate A1 with particle size of 1-120 μm₂O₃A calcined product after fluoride treatment;

d) taking the total weight of the solid mixture as a reference, and taking the amount of the combustible solid lubricating material as 0.01-10 wt%;

e) 0.01-8 wt% of alkaline earth metal compound based on the total weight of the solid mixture;

s2, mixing, kneading and extruding the solid mixture and the binder in the step S1 with optional water to obtain a molded body;

the addition amount of the binder is 25-60 wt% of the total weight of the solid mixture, and the addition amount of the water is 0-30 wt% of the total weight of the solid mixture; and

s3, drying the formed body in the step S2 to the content of free water below 10 weight percent, and then roasting at the highest roasting temperature of 1200-1500 ℃ to obtain α -A1₂O₃And (3) a carrier.

The α -alumina carrier provided by the invention preferably has the following characteristics of α -A1₂O₃The content is more than 90 weight percent, and the crushing strength is 40-200N/particle, preferably 50-160N/particle; the specific surface area is 0.3 to 2.0m²A preferred range is 0.5 to 1.8 m/g²(ii) g, more preferably 1.45 to 1.8m²A more preferable range is 1.6 to 1.8 m/g²(ii)/g; the water absorption rate is 30-80%, preferably 40-70%, more preferably 52.5-58%, and more preferably 54.2-58%; the pore volume is 0.30-0.85 ml/g, preferably 0.40-0.75 ml/g, more preferably 0.53-0.6 ml/g, and even more preferably 0.55-0.58 ml/g; the average crystal size is 1.0 to 8.0 μm, preferably 3.0 to 6.0. mu.m, more preferably 3.0 to 5.3. mu.m, and still more preferably 3.0 to 4.0. mu.m.

In the invention, the lateral crushing strength of the carrier is measured by adopting a D L II type intelligent particle strength tester, a carrier sample is selected, the radial crushing strength is measured and then an average value is taken, the water absorption is measured by a density method, the specific surface area is measured by adopting a nitrogen physical adsorption BET method, the pore volume is measured by adopting a mercury intrusion method, and the average crystal size is measured by adopting a scanning electron microscope observation method.

The invention also provides a silver catalyst for ethylene epoxidation, which comprises a carrier and an active component silver loaded on the carrier, wherein the carrier is the α -alumina carrier provided by the invention.

According to a preferred embodiment of the present invention, there is also provided a silver catalyst for ethylene epoxidation, comprising:

a) the α -alumina carrier provided by the invention;

b) silver deposited on said α -alumina support;

c) alkali and/or alkaline earth metals or compounds based on alkali and/or alkaline earth metals;

d) rhenium metal and/or rhenium-based compounds; and

e) optionally, a rhenium co-promoter, selected from one or more metals of chromium, molybdenum, tungsten and manganese, and/or from a compound based on one or more metals of chromium, molybdenum, tungsten and manganese.

According to the invention, in the silver catalyst, the mass content of silver is 5-37%, preferably 8-32%, based on the total weight of the silver catalyst; the mass content of the alkali metal is 5-3000 ppm, preferably 10-2000 ppm; the mass content of the alkaline earth metal is 50-20000 ppm, preferably 100-15000 ppm; the mass content of rhenium metal is 10-2000 ppm, preferably 100-1500 ppm; the content of the co-promoter is 0-1500 ppm, preferably 0-1000 ppm, calculated by the metal in the co-promoter.

The silver catalyst of the present invention may be prepared in a conventional manner by impregnating the α -alumina support described above with a solution containing a silver compound, an organic amine, an alkali metal promoter, an alkaline earth metal promoter, a rhenium-containing promoter, and optionally a co-promoter.

Among them, the organic amine compound may be any organic amine compound suitable for preparing a silver catalyst for ethylene oxide production as long as the organic amine compound is capable of forming a silver amine complex with a silver compound, and for example, may be selected from one or more of pyridine, butylamine, ethylenediamine, 1, 3-propanediamine, and ethanolamine, and is preferably a mixture of ethylenediamine and ethanolamine.

The alkali metal promoter may be a compound of lithium, sodium, potassium, rubidium or caesium or a compound of any of these, such as a nitrate, sulphate or hydroxide thereof, or a combination of any two or more of the foregoing, preferably caesium sulphate and/or nitrate.

The alkaline earth metal promoter may be a compound of magnesium, calcium, strontium or barium, such as an oxide, oxalate, sulphate, acetate or nitrate thereof, or a combination of any two or more of the foregoing compounds, preferably a barium or strontium compound, more preferably barium acetate and/or strontium acetate. The alkaline earth metal promoter may be applied to the support before, simultaneously with, or after impregnation of the silver, or may be impregnated on the support after the silver compound has been reduced.

The rhenium-containing promoter may be a rhenium oxide, perrhenic acid, perrhenate, or mixtures thereof, preferably perrhenic acid and/or perrhenate, such as, for example, perrhenic acid, cesium perrhenate, ammonium perrhenate, and the like.

The co-promoter comprising the rhenium promoter may be a compound of any one of the transition metals of the periodic table of the elements, or a mixture of several transition metal compounds, preferably one or more metals of chromium, molybdenum, tungsten and manganese, and/or compounds based on one or more elements of chromium, molybdenum, tungsten and manganese, for example one or more of chromic acid, chromium nitrate, tungstic acid, caesium tungstate, molybdic acid, ammonium molybdate, manganic acid, potassium permanganate and the like. The rhenium promoter and its co-promoter may be applied to the carrier before, simultaneously with, or after impregnation of the silver, or may be impregnated on the carrier after the silver compound has been reduced. The activity, selectivity, and stability of activity and selectivity of the resulting silver catalyst can be further improved by the addition of a rhenium promoter and its co-promoter.

According to a specific embodiment of the present invention, the preparation method of the silver catalyst comprises the steps of:

(1) impregnating the porous α -alumina carrier with a solution containing sufficient amounts of silver compound, organic amine, alkali metal promoter, alkaline earth metal promoter, rhenium-containing promoter and co-promoter thereof;

(2) filtering to remove the impregnation solution, and drying the impregnated carrier; and

(3) and (3) activating the carrier obtained in the step (2) in oxygen-containing mixed gas to prepare the silver catalyst.

In the preparation of the silver catalyst, silver nitrate and ammonium oxalate solution are mixed to generate silver oxalate, the silver oxalate is dissolved in organic amine to prepare silver amine solution, then the auxiliary agent is added to prepare impregnation liquid, then the prepared impregnation liquid is used for impregnating the α -alumina carrier, the leaching is carried out, and the thermal decomposition is carried out in air flow or nitrogen-oxygen mixed gas with oxygen content not more than 21 wt percent (such as 8 wt percent of oxygen content) at the temperature of 180-700 ℃ and preferably 200-500 ℃ for 0.5-120 minutes and preferably 1-60 minutes to prepare the finished product silver catalyst.

According to another aspect of the present invention, there is provided a method for oxidizing ethylene, which comprises subjecting ethylene to an ethylene epoxidation reaction under the action of the α -alumina carrier provided by the present invention and/or the silver catalyst provided by the present invention to obtain ethylene oxide.

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.

Various silver catalysts of the present invention were tested for their initial performance and stability using a laboratory reactor (hereinafter referred to simply as "micro-reactor") evaluation apparatus. The reactor used in the microreaction evaluation apparatus was a stainless steel tube having an inner diameter of 4mm, and the reactor 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 activity and selectivity used in the present invention are as follows:

reaction gas composition (mol%)

When the reaction conditions are stably achieved, the gas composition at the inlet and outlet of the reactor is continuously measured. The selectivity was calculated after volume shrinkage correction of the measurement results according to the following formula:

where Δ EO is the difference in the ethylene oxide concentration of the outlet gas and the inlet gas, and the average of more than 10 sets of test data was taken as the test result on the same day.

In the following examples, the lateral crush strength of an alumina carrier is measured by a D L II type intelligent particle strength tester, an alumina carrier sample is selected, the radial crush strength is measured and then an average value is taken, the water absorption is measured by a density method, the specific surface area is measured by a nitrogen physical adsorption BET method, the pore distribution is measured by a mercury intrusion method, and the average crystal size is measured by a scanning electron microscope observation method.

Support preparation comparative example 1

This comparative preparation example is used to illustrate the preparation of a reference alumina support.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃380g of magnesium fluoride20g and 4g of barium nitrate are put into a blender to be mixed evenly, the mixture is transferred into a kneader, 22g of petroleum coke and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln and is heated from the room temperature to 1400 ℃ for 33 hours, and the calcination is carried out for 5 hours at the temperature of 1400 ℃, thus obtaining white α -A1₂O₃And (3) a carrier. The measured carrier property data are shown in table 1 below.

Comparative example 2 Carrier preparation

This comparative preparation example is used to illustrate the preparation of a reference alumina support.

372.0g of industrial α -alumina trihydrate, 110.0g of pseudo-monohydrate alumina, 8.0g of ammonium fluoride, 1.0g of barium sulfate and 10.0g of vaseline are placed in a mixer to be uniformly mixed, then, 132.0g of 17 wt% of dilute nitric acid aqueous solution is added to be fully kneaded into paste capable of being extruded and molded, then, the paste is extruded and molded, the molded carrier blank is dried for 16 hours at the temperature of about 80-100 ℃, then, the temperature is raised to 1300 ℃ and 1350 ℃ in a high-temperature bell-type kiln within 40 hours, and the temperature is kept for 6 hours, so that the first-step molded solid is obtained.

62g of the first-step shaped solid was taken out and placed in an acid-resistant plastic cup, and 125g of an aqueous solution containing 1.2% by weight of ammonium fluoride and 1.5% by weight of oxalic acid (the solution had a pH of 3 and a fluorine content of 0.62% by atom) was poured thereinto, and immersed at room temperature for 40 minutes, after which the solution was leached out, and then the resultant sample was immersed and washed with 90g of distilled water for 20 minutes, leached out of water, and thus washed three times, and then dried in a flowing air stream at 450 ℃ for 10 minutes, and then baked in a muffle furnace at a constant temperature of 500 ℃ for 120 minutes, to obtain a carrier. The measured carrier property data are shown in table 1 below.

Support preparation example 1

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

100g of magnesium fluoride is dissolved in 1000m L dilute nitric acid (nitric acid: water: 1: 5 by weight ratio), and 1-120 μm pseudo-monohydrate A1 is added₂O₃2000g, dipping for 2h, 80-10Drying at 0 deg.C for 20h, and calcining at 500 deg.C for 6h to obtain calcined product A₁。

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃360g, calcined product A₁20g and 4g of barium nitrate are put into a blender to be mixed evenly, the mixture is transferred into a kneader, 22g of petroleum coke and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln and is heated from the room temperature to 1400 ℃ for 33 hours, and the calcination is carried out for 5 hours at the temperature of 1400 ℃, thus obtaining white α -A1₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 2

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₁The procedure was as in example 1.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃190g, calcined product A₁190g and barium nitrate 4g are put into a blender to be mixed evenly, and then are transferred into a kneader, 22g of petroleum coke and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from the room temperature to 1400 ℃ after 33 hours, and the carrier is calcined for 5 hours at the temperature of 1400 ℃, thus obtaining white α -A1₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 3

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₁In the same manner asSupport preparation example 1.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of a calcined product A₁380g and 4g of barium nitrate are put into a blender to be mixed evenly, and are transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from the room temperature to 1400 ℃ after 33 hours, the carrier is calcined for 5 hours at the temperature of 1400 ℃, and white α -A1 is obtained₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 4

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

100g of magnesium fluoride is dissolved in 1000m L dilute nitric acid (nitric acid: water: 1: 5 by weight ratio), and 1-120 μm pseudo-monohydrate A1 is added₂O₃2000g, dipping for 2h, drying at 80-100 ℃ for 20h, and roasting at 800 ℃ for 6h to obtain a roasted product A₂。

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃360g, calcined product A₂20g and 4g of barium nitrate are put into a blender to be mixed evenly, the mixture is transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln and is heated from the room temperature to 1400 ℃ for 33 hours to be calcined for 5 hours at the temperature of 1400 ℃, and white α -A1 is obtained₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 5

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₂The same procedure as in example 4 was repeated to prepare a support.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃190g, calcined product A₂190g and barium nitrate 4g are put into a blender and mixed evenly, and then transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (weight ratio: 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, and the column is dried for more than 2 hours at 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from room temperature to 1400 ℃ after 33 hours, and the carrier is calcined for 5 hours at 1400 ℃ to obtain white α -A1₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 6

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₂The same procedure as in example 4 was repeated to prepare a support.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of a calcined product A₂380g and 4g of barium nitrate are put into a blender to be mixed evenly, and are transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from the room temperature to 1400 ℃ after 33 hours, the carrier is calcined for 5 hours at the temperature of 1400 ℃, and white α -A1 is obtained₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 7

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

100g of magnesium fluoride is dissolved in 1000m L dilute nitric acid (nitric acid: water: 1: 5 by weight), and 1-120 μm pseudomono is addedWater A1₂O₃2000g, dipping for 2h, drying at 80-100 ℃ for 20h, and roasting at 1000 ℃ for 6h to obtain a roasted product A₃。

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃360g, calcined product A₃20g and 4g of barium nitrate are put into a blender to be mixed evenly, the mixture is transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln and is heated from the room temperature to 1400 ℃ for 33 hours to be calcined for 5 hours at the temperature of 1400 ℃, and white α -A1 is obtained₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 8

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₃The procedure was as in example 7.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of trihydrate α -A1 with the particle size of 25-300 mu m₂O₃190g, calcined product A₃190g and barium nitrate 4g are put into a blender and mixed evenly, and then transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (weight ratio: 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, and the column is dried for more than 2 hours at 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from room temperature to 1400 ℃ after 33 hours, and the carrier is calcined for 5 hours at 1400 ℃ to obtain white α -A1₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Support preparation example 9

The preparation examples are provided to illustrate the preparation of the alumina carrier provided by the present invention.

Calcined product A₃The procedure was as in example 7.

Mixing pseudomonohydrate A1 of 1-120 μm₂O₃220g of a calcined product A₃380g and 4g of barium nitrate are put into a blender to be mixed evenly, and are transferred into a kneader, 22g of graphite and 200ml of dilute nitric acid (the weight ratio of nitric acid to water is 1: 5) are added to be kneaded into paste which can be extruded and molded, the paste is extruded and molded into a seven-hole column with the outer diameter of 8.0mm, the length of 6.0mm and the inner diameter of 1.0mm, the mixture is dried for more than 2 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 weight percent, the carrier after the kneading and molding is put into a bell jar kiln, the temperature is increased from the room temperature to 1400 ℃ after 33 hours, the carrier is calcined for 5 hours at the temperature of 1400 ℃, and white α -A1 is obtained₂O₃And (3) a carrier. The physical properties of the carriers were measured as shown in Table 1 below.

Catalyst preparation examples

Weighing 140g of silver nitrate and dissolving in 150ml of deionized water, weighing 64g of ammonium oxalate and dissolving in 520ml of deionized water, fully dissolving to 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 more than 30 minutes, filtering, and washing the precipitate with deionized water until no nitrate ions exist. The filter cake contained about 60% by weight silver and about 15% by weight water.

70.0g of ethylenediamine is dissolved in 75.0g of deionized water, the silver oxalate filter cake prepared by the method is added, the stirring is continued to completely dissolve the silver oxalate, and then 2.58g of cesium nitrate, 6.22g of barium acetate, 0.86g of ammonium perrhenate and deionized water are sequentially added to make the total mass of the solution reach 400g, so as to prepare impregnation liquid for later use.

20g of the support samples prepared in comparative examples 1 to 2 and examples 1 to 9 were taken, respectively, placed in a vacuum vessel, evacuated to 10mmHg or more, the above impregnation solution was introduced, and kept for 30min, and excess solution was leached out. Heating the impregnated carrier in air flow at 450 deg.C for 3min, and cooling to obtain silver catalysts DC-1, DC-2 and C-1 to C-9.

The activity and selectivity of the catalyst samples were measured using a microreactor evaluation unit under the aforementioned process conditions, and the results of the microreaction evaluation are shown in Table 2.

TABLE 1 physical Properties of the vectors

TABLE 2 Properties of the catalysts

As can be seen from the data in tables 1 and 2, the carrier provided by the method of the present invention has higher specific surface area, water absorption, pore volume, lower average crystal size of the carrier, and higher crushing strength. The catalyst prepared by the carrier of the invention has the advantages of obviously reduced reaction temperature (namely improved reaction activity), improved selectivity and wide application prospect.

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.