CN115475610B - Alpha-alumina carrier, preparation method thereof, silver catalyst and olefin epoxidation method - Google Patents

Alpha-alumina carrier, preparation method thereof, silver catalyst and olefin epoxidation method Download PDF

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CN115475610B
CN115475610B CN202110663103.6A CN202110663103A CN115475610B CN 115475610 B CN115475610 B CN 115475610B CN 202110663103 A CN202110663103 A CN 202110663103A CN 115475610 B CN115475610 B CN 115475610B
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carrier
alpha
solid mixture
alumina
total weight
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CN115475610A (en
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王辉
魏会娟
廉括
李金兵
代武军
汤之强
李巍
林伟
曹淑媛
高立新
崔秉全
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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Sinopec Beijing Research Institute of Chemical Industry
China Petroleum and Chemical Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/612—Surface area less than 10 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/64—Pore diameter
    • B01J35/657—Pore diameter larger than 1000 nm
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • C07D301/10—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
    • C07D303/02—Compounds containing oxirane rings
    • C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Catalysts (AREA)

Abstract

The invention belongs to the field of catalysts, and relates to an alpha-alumina carrier, a preparation method thereof, a silver catalyst and an olefin epoxidation method. The method comprises the following steps: step I, obtaining a solid mixture; step II, adding an aqueous binder solution into the solid mixture in the step I to obtain an alpha-alumina carrier precursor mixture; and III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, forming, drying and roasting to obtain the alpha-alumina carrier. The invention can realize that the specific surface area and the pore size of lignocellulose and/or natural resin are simultaneously optimized by adding the lignocellulose and/or the natural resin in the preparation process of the carrier. The carrier can be used for olefin epoxidation reaction, in particular to a carrier of a catalyst used for preparing ethylene oxide by ethylene epoxidation.

Description

Alpha-alumina carrier, preparation method thereof, silver catalyst and olefin epoxidation method
Technical Field
The invention belongs to the field of catalysts, and particularly relates to a preparation method of an alpha-alumina carrier, the alpha-alumina carrier prepared by the preparation method, a silver catalyst containing the alpha-alumina carrier, and an olefin epoxidation method adopting the silver catalyst.
Background
Alumina is an important one of the oxides and is widely used in the fields of refractory materials, ceramics, catalysts, adsorbents, catalyst carriers and the like. Among them, as a catalyst support, alumina supports play a very important role: such as, (1) improving the dispersibility of the active ingredient; (2) the consumption of active components is reduced, and the cost is lowered; (3) increasing the effective specific surface area to provide a suitable pore structure; (4) improving the thermal stability of the catalyst. Among them, the specific surface area and pore structure of the alumina carrier play a critical role in catalyst performance. The specific surface area of the carrier is large, so that the dispersibility of the active components on the carrier is improved, the effective active components are increased, but the large specific surface area of the carrier is unfavorable for the large aperture of the carrier, too small aperture of the carrier is unfavorable for timely adsorption and desorption of reactants or products in the catalytic reaction process, and for exothermic reaction, the smaller aperture of the carrier can cause that heat generated by the reaction cannot be timely diffused, so that the local temperature is too high, and the activity of the catalyst is possibly reduced. Conversely, if the specific surface area of the carrier is small, it has a larger pore size, but the low specific surface area is detrimental to the loading of the active ingredient on the carrier. The balance between the different physical properties is very important for the carrier. Therefore, the ideal alumina catalyst support should have a large specific surface area and a large pore structure, but both are constrained with each other, and are difficult to optimize.
Disclosure of Invention
In view of the above-described state of the art, through extensive and intensive studies in the field of α -alumina support and silver catalyst preparation, the inventors of the present invention have achieved that the specific surface area and pore size thereof can be simultaneously optimized by adding lignocellulose and/or natural resin during the support preparation. The carrier can be used for olefin epoxidation reaction, in particular to a carrier of a catalyst used for preparing ethylene oxide by ethylene epoxidation.
The first aspect of the present invention provides a method for preparing an α -alumina carrier, comprising the steps of:
step I, obtaining a solid mixture comprising the following components:
a. 5 to 90 wt% alumina trihydrate based on the total weight of the solid mixture;
b. 5 to 70 wt% pseudo-boehmite based on the total weight of the solid mixture;
c. 0 to 8 wt% of an alkaline earth metal compound based on the total weight of the solid mixture;
d. 0 to 12 wt% of a fluoride-containing compound, based on the total weight of the solid mixture;
e. from 0.1% to 40% by weight, based on the total weight of the solid mixture, of lignocellulose and/or natural resins;
step II, adding an aqueous binder solution into the solid mixture in the step I to obtain an alpha-alumina carrier precursor mixture;
and III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, forming, drying and roasting to obtain the alpha-alumina carrier.
In a second aspect the invention provides an alpha-alumina support obtainable by the above-described preparation process.
In a third aspect, the invention provides a silver catalyst for olefin epoxidation, which comprises a carrier and active component silver loaded on the carrier, wherein the carrier is the alpha-alumina carrier.
In a fourth aspect, the present invention provides a process for the epoxidation of an olefin which comprises subjecting the olefin to an olefin epoxidation reaction over a silver catalyst as defined above to give an epoxide.
According to the invention, lignocellulose and/or natural resin are added in the preparation process of the alpha-alumina carrier, and the addition amount of the lignocellulose and/or the natural resin is adjusted to realize that the prepared alpha-alumina carrier has larger specific surface area and pore diameter, and specifically, the specific surface area of the prepared alpha-alumina carrier is 0.5-15.0 m 2 Preferably 1.0-5.0m 2 /g; the pore diameter of the carrier is 0.1-100.0 μm, preferably 0.2-50.0 μm; the water absorption rate of the carrier is more than or equal to 30.0%, preferably 40.0% -85.0%. The carrier can be used for silver catalyst carrier for producing ethylene oxide by ethylene epoxidation.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
The following describes specific embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
According to the invention, lignocellulose and/or natural resin, alumina trihydrate, pseudo-boehmite, fluoride and alkaline earth metal compound are mixed, kneaded, molded, dried and roasted to obtain the alpha-alumina carrier, and the specific surface area of the alpha-alumina carrier can be increased, the aperture of the alpha-alumina carrier can be increased by adjusting the dosage of the lignocellulose and/or the natural resin, and the specific surface area and aperture of the alpha-alumina carrier can be improved.
Specifically, the invention provides a preparation method of an alpha-alumina carrier, which comprises the following steps:
step I, obtaining a solid mixture comprising the following components:
a. 5 to 90 wt% alumina trihydrate based on the total weight of the solid mixture;
b. 5 to 70 wt% pseudo-boehmite based on the total weight of the solid mixture;
c. 0 to 8 wt% of an alkaline earth metal compound based on the total weight of the solid mixture;
d. 0 to 12 wt% of a fluoride-containing compound, based on the total weight of the solid mixture;
e. from 0.1% to 40% by weight, based on the total weight of the solid mixture, of lignocellulose and/or natural resins;
step II, adding an aqueous binder solution into the solid mixture in the step I to obtain an alpha-alumina carrier precursor mixture;
and III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, forming, drying and roasting to obtain the alpha-alumina carrier.
According to the present invention, preferably, the natural resin is selected from rosin and/or mastic; the weight of the lignocellulose and/or natural resin is preferably 0.5 to 20% by weight based on the total weight of the solid mixture.
In the preparation process of the alpha-alumina carrier, the alumina trihydrate is subjected to dehydration and crystal phase transformation of alumina with different crystal phases, and finally is converted into the alpha-alumina. According to the present invention, the alumina trihydrate may be selected from one or more of gibbsite, norboehmites, and bayerite; the weight of the alumina trihydrate is preferably 40% to 80% by weight of the total weight of the solid mixture.
In the preparation process of the alpha-alumina carrier, the pseudo-boehmite and the binder generate alumina sol, the components are bonded together to form paste which can be extruded and molded, and the pseudo-boehmite can be converted into the alpha-alumina in the high-temperature roasting process. According to the invention, the weight of pseudo-boehmite preferably represents 10.0% to 45.0% by weight of the total weight of the solid mixture.
In order to accelerate the crystal form transformation of alumina according to the present invention, a fluorine-containing compound may be added during the preparation of the alpha-alumina carrier. The fluorine-containing compound may be selected from one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite. The fluorine-containing compound preferably comprises 0.1 to 10.0 wt% of the total weight of the solid mixture.
According to the present invention, the alkaline earth metal compound may be selected from one or more of an oxide, hydroxide, sulfate, nitrate and oxalate of an alkaline earth metal. The alkaline earth metal compound preferably comprises 0.1 to 2.0 wt% of the total weight of the solid mixture.
In the preparation method of the alpha-alumina carrier, the aqueous binder solution is used for forming an aluminum sol with pseudo-boehmite in the solid mixture, so that all the components are bonded together to form paste capable of being extruded and molded. The aqueous binder solution may be at least one selected from the group consisting of aqueous citric acid solution, aqueous nitric acid solution, aqueous formic acid solution, aqueous acetic acid solution, aqueous propionic acid solution, and hydrochloric acid. The amount of the aqueous binder solution and the content of the binder therein are limited to meet the requirements of bonding and forming into an extrudable paste, and specifically, the amount of the aqueous binder solution may be 5 to 60 wt% based on the total weight of the solid mixture. Typically, the mass ratio of binder to water in the aqueous binder solution is 1:0.2 to 10.
The mixing of the components of the solid mixture according to the invention with the aqueous binder solution does not need to be in a specific order, for example the fluoride in the solid mixture can be added to the solid mixture together with the binder at the end.
The shaping of the invention is carried out in a shaping machine, and the shape of the alpha-alumina carrier after shaping can be selected from sphere, raschig ring shape, single-hole cylinder, porous cylinder, block, pill and leafy grass shape.
In some embodiments of the present invention, to facilitate extrusion of the molded article, a molding aid may be added to the solid mixture, the molding aid including at least one of petrolatum, graphite, lubricating oil, and vegetable oil.
The drying process is carried out in a forced air drying oven, preferably the drying process can be carried out at 80-120 ℃ and the drying time is controlled to be more than 24 hours
The roasting step of the present invention is carried out in an air atmosphere, preferably at a roasting temperature of 1100 to 1500 ℃ for a roasting time of 1 to 60 hours.
The invention also provides an alpha-alumina carrier prepared by the preparation method.
Specifically, the specific surface area of the alpha-alumina carrier is 0.5-15.0 m 2 Preferably 1.0-5.0m 2 /g; the pore diameter of the carrier is 0.1-100.0 μm, preferably 0.2-50.0 μm; the water absorption rate of the carrier is more than or equal to 30.0%, preferably 40.0% -85.0%.
The invention also provides a silver catalyst for olefin epoxidation, which comprises a carrier and active component silver loaded on the carrier, wherein the carrier is the alpha-alumina carrier.
According to one embodiment of the present invention, the silver catalyst further comprises:
a) Alkali metal and/or alkaline earth metal or alkali metal and/or alkaline earth metal based compounds;
b) Rhenium metal and/or rhenium-based compounds; and
c) Optionally a co-promoter element of rhenium selected from one or more of cerium, sulfur, molybdenum, chromium salts or oxyanions in acid form.
The silver catalysts of the present invention may be prepared by those skilled in the art in a known manner or in any conventional manner. Such as impregnating the α -alumina support with a solution of a co-promoter containing a sufficient amount of an organic amine, a silver compound, an alkali metal promoter, an alkaline earth metal promoter, optionally a rhenium promoter, and a rhenium promoter.
According to a preferred embodiment of the present invention, the silver catalyst is prepared by a process comprising the steps of: impregnating an alpha-alumina support prepared according to the process of the present invention with a solution of a co-promoter comprising a sufficient amount of an organic amine, a silver compound, an alkali metal promoter, an alkaline earth metal promoter, optionally a rhenium promoter; II) leaching the impregnation liquor; III) activating the carrier obtained in the step II) in oxygen-containing gas to prepare the silver catalyst.
According to the present invention, in the preparation of the silver catalyst, the organic amine may be selected from one or more of 1, 2-propanediamine, 1, 3-propanediamine, ethylenediamine, 1, 2-butanediamine, 1, 3-butanediamine, pyridine, ethylamine, n-propylamine, n-butylamine, isobutylamine, t-butylamine, sec-butylamine, ethanolamine, propanolamine and butanolamine; the silver compound may be selected from one or more of silver oxide, silver nitrate and silver oxalate; the alkali metal auxiliary agent can be selected from one or more of lithium, sodium, potassium, rubidium and cesium; the alkaline earth metal promoter may be selected from one or more of magnesium, calcium, strontium, barium, the rhenium promoter may be selected from one or more of rhenium oxide, ammonium perrhenate, perrhenic acid, and cesium perrhenate, and the co-promoter of the rhenium promoter may be selected from one or more of cerium, sulfur, molybdenum, chromium salts, or oxyanions in acid form.
According to the invention, the mass of the silver element accounts for 10-40% of the mass of the silver catalyst; the mass of the alkali metal auxiliary agent accounts for 5-2000 ppm of the mass of the silver catalyst; the mass of the alkaline earth metal auxiliary agent accounts for 5-20000 ppm of the mass of the silver catalyst; the mass of the rhenium auxiliary agent accounts for 50-10000 ppm of the mass of the silver catalyst.
In the silver catalyst preparation method, the activation is performed in an oxygen-containing mixed gas, and the oxygen-containing mixed gas comprises air flow or nitrogen-oxygen mixed gas with oxygen content not more than 21%; the activation temperature is 180-700 ℃ and the activation time is 1-120 min.
In the method, in order to prepare the silver catalyst, firstly, an aqueous solution of silver nitrate is reacted with an aqueous solution of ammonium oxalate or oxalic acid to precipitate silver oxalate, filtering, washing with deionized water until no nitrate ions exist, then, dissolving silver oxalate into an aqueous solution of organic amine, adding an alkali metal auxiliary agent, an alkaline earth metal auxiliary agent, an optional rhenium auxiliary agent and a co-auxiliary agent of the rhenium auxiliary agent to prepare an impregnating solution, impregnating the alpha-alumina carrier prepared by the method with the obtained impregnating solution, leaching the impregnating solution, and activating to finally prepare the silver catalyst.
In order to obtain a silver catalyst with higher silver content and/or additive content, the silver-containing catalyst can be prepared by one or more impregnation methods.
The alkali metal, alkaline earth metal, rhenium auxiliary agent, rhenium co-auxiliary agent and other auxiliary agents added in the silver catalyst preparation process can be deposited on the carrier before, during or after silver impregnation, or can be deposited on the carrier after the silver compound is activated and reduced.
In another aspect, the invention also provides a method for olefin epoxidation, wherein the method comprises the step of carrying out olefin epoxidation reaction under the action of the silver catalyst to obtain an epoxide. Wherein the olefin may include one or more of styrene, propylene, ethylene, and 1, 3-butadiene. The olefin epoxidation reaction apparatus may be any apparatus capable of conducting an epoxidation reaction.
The present invention will be further described with reference to examples, but the scope of the present invention is not limited to these examples.
The specific surface area of the alpha-alumina carrier in the embodiment of the invention is measured by a nitrogen physical adsorption and desorption BET specific surface area analyzer, and the aperture is measured by a mercury intrusion analyzer.
Comparative example 1
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride and 2.5g of barium nitrate are put into a mixer to be uniformly mixed, the mixture is transferred into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added to be kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. And then placing the dried single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1300 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 1.2m 2 Per g, pore size 0.9 μm and water absorption 45%.
Comparative example 2
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride, 2.5g of barium nitrate and 65.4g of methylcellulose are put into a mixer to be uniformly mixed, the mixture is transferred into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added, so that the mixture is kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. And then placing the dried single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1300 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 0.9m 2 Per g, pore size 1.1 μm and water absorption 47%.
Example 1
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride, 2.5g of barium nitrate and 65.4g of lignocellulose are put into a mixer to be uniformly mixed, and then put into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added, and kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. And then placing the dried single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1300 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 1.8m 2 Per g, pore size 2.1 μm and water absorption 76.1%.
Example 2
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride, 2.5g of barium nitrate and 82g of lignocellulose are put into a mixer to be uniformly mixed, and then put into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added to be kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. Then the dried product is driedAnd (3) placing the single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1300 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 1.9m 2 Per g, pore size was 2.7 μm and water absorption was 81.3%.
Example 3
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride, 2.5g of barium nitrate and 35g of rosin are put into a mixer to be uniformly mixed, and then the mixture is transferred into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added to be kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. And then placing the dried single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1350 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 1.5m 2 The pore size was 1.8 μm and the water absorption was 59.7%.
Example 4
480.0g of gibbsite, 120.0g of pseudo-boehmite, 5.6g of aluminum fluoride, 2.5g of barium nitrate, 25g of rosin and 25g of lignocellulose are put into a mixer to be uniformly mixed, and then the mixture is transferred into a kneader, and 100 ml of dilute nitric acid (nitric acid: water=1:3, volume ratio) is added, and kneaded into paste capable of being extruded and formed. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object, and the single-hole cylindrical object is dried for more than 24 hours at the temperature of 80-120 ℃ to reduce the free water content to below 10 percent. And then placing the dried single-hole cylindrical object into a bell kiln for roasting, wherein the roasting temperature is 1230 ℃, the constant-temperature roasting is carried out for 20 hours, and finally, the alpha-alumina carrier is obtained after cooling to room temperature. The specific surface area of the carrier was measured to be 2.4m 2 Per g, pore size 3.2 μm and water absorption 82.1%.
As can be seen from the comparison of the example data and the comparative example data, the addition of lignocellulose and/or natural resin in the preparation process of the carrier can improve the performance of the alpha-alumina carrier, and the addition of the lignocellulose and/or natural resin in a certain range can not only improve the specific surface area of the alpha-alumina carrier, but also increase the pore size of the alpha-alumina carrier. For olefin epoxidation reactions with strong exotherm, such as ethylene epoxidation to ethylene oxide, the alpha-alumina carrier prepared by the invention is an ideal catalyst carrier and can improve the catalytic performance of the catalyst used in the reaction.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

Claims (14)

1. A method for preparing an alpha-alumina carrier, comprising the following steps:
step I, obtaining a solid mixture comprising the following components:
a. 5 to 90 wt% alumina trihydrate based on the total weight of the solid mixture;
b. 5 to 70 wt% pseudo-boehmite based on the total weight of the solid mixture;
c. 0 to 8 wt% of an alkaline earth metal compound based on the total weight of the solid mixture;
d. 0 to 12 wt% of a fluorochemical compound based on the total weight of the solid mixture;
e. from 0.1% to 40% by weight, based on the total weight of the solid mixture, of lignocellulose and/or natural resins;
step II, adding an aqueous binder solution into the solid mixture in the step I to obtain an alpha-alumina carrier precursor mixture;
and III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, forming, drying and roasting to obtain the alpha-alumina carrier.
2. The method of claim 1, wherein the natural resin is selected from rosin and/or mastic; the weight of the lignocellulose and/or the natural resin accounts for 0.5-20 wt% of the total weight of the solid mixture.
3. The preparation method according to claim 1, wherein the alumina trihydrate is selected from one or more of gibbsite, nordiaspore, and surge aluminosilicate; the weight of the alumina trihydrate is 40.0-80.0% of the total weight of the solid mixture.
4. The method of claim 1, wherein the pseudo-boehmite is present in an amount of 10.0 wt% to 45.0 wt% based on the total weight of the solid mixture.
5. The preparation method according to claim 1, wherein the fluorine-containing compound is selected from one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite; the fluorine-containing compound accounts for 0.1 to 10.0 weight percent of the total weight of the solid mixture.
6. The production method according to claim 1, wherein the alkaline earth metal compound is selected from one or more of an oxide, a hydroxide, a sulfate, a nitrate and an oxalate of an alkaline earth metal; the alkaline earth metal compound is present in an amount of 0.1 wt% to 2.0 wt% based on the total weight of the solid mixture.
7. The production method according to claim 1, 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 hydrochloric acid; the mass ratio of the binder to water in the binder aqueous solution is 1:0.2-10; the binder aqueous solution is added in an amount of 5 to 60% by weight based on the total weight of the solid mixture.
8. The preparation method according to claim 1, wherein the drying temperature is 80-120 ℃ and the drying time is more than 24 hours; the roasting temperature is 1100-1500 ℃ and the roasting time is 1-60 h.
9. An α -alumina support obtainable by the process of any one of claims 1 to 8.
10. The α -alumina carrier according to claim 9, wherein the specific surface area of the α -alumina carrier is 0.5-15.0 m 2 /g; the pore diameter of the carrier is 0.1-100.0 mu m; the water absorption rate of the carrier is more than or equal to 30.0 percent.
11. The alpha-alumina carrier according to claim 10, wherein the specific surface area of the alpha-alumina carrier is 1.0-5.0m 2 /g; the pore diameter of the carrier is 0.2-50.0 mu m; the water absorption rate of the carrier is 40.0% -85.0%.
12. A silver catalyst for olefin epoxidation comprising a carrier and an active ingredient silver supported on the carrier, the carrier being the α -alumina carrier of claim 10 or 11.
13. A process for the epoxidation of an olefin which comprises subjecting an olefin to an olefin epoxidation reaction under the influence of the silver catalyst of claim 12 to obtain an epoxide.
14. The olefin epoxidation process of claim 13 wherein the olefin is selected from one or more of styrene, propylene, ethylene, and 1, 3-butadiene.
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