CN115475610A - Alpha-alumina carrier and preparation method thereof, silver catalyst and olefin epoxidation method - Google Patents

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

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CN115475610A
CN115475610A CN202110663103.6A CN202110663103A CN115475610A CN 115475610 A CN115475610 A CN 115475610A CN 202110663103 A CN202110663103 A CN 202110663103A CN 115475610 A CN115475610 A CN 115475610A
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carrier
solid mixture
alpha
total weight
alumina carrier
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CN115475610B (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 and 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 a binder aqueous solution into the solid mixture obtained in the step I to obtain an alpha-alumina carrier precursor mixture; and step III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, molding, drying and roasting to obtain the alpha-alumina carrier. The specific surface area and the pore size of the carrier can be 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 for preparing ethylene oxide by ethylene epoxidation.

Description

Alpha-alumina carrier and 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 one of the more important oxides, and is widely used in the fields of refractory materials, ceramics, catalysts, adsorbents, catalyst carriers and the like. Among them, as a catalyst carrier, an alumina carrier plays 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 reduced; (3) increase the effective specific surface, provide suitable pore structure; (4) the thermal stability of the catalyst is improved. Among them, the specific surface area and pore structure of the alumina carrier play a crucial role in the catalyst performance. The carrier specific surface area is big, is favorable to improving the dispersibility of active ingredient on the carrier, increases effective active ingredient, but great carrier specific surface area is unfavorable for the large aperture of carrier, and the carrier aperture is too little can be unfavorable for catalytic reaction process reactant or resultant in time to inhale the desorption, and to exothermic reaction, the carrier aperture is less can cause the heat that the reaction produced can not in time diffuse, causes local high temperature, also can cause catalyst activity to reduce moreover. Conversely, if the specific surface area of the carrier is small, the carrier has larger pore size, but the low specific surface area is not favorable for loading the active component on the carrier. The balance between the different physical properties is very important for the carrier. Therefore, the ideal alumina catalyst carrier should have a large specific surface area and a large pore structure, but both are mutually restricted and difficult to realize and optimize.
Disclosure of Invention
In view of the above-mentioned state of the art, through extensive and intensive studies in the field of preparation of α -alumina carriers and silver catalysts, the inventors of the present invention have achieved simultaneous optimization of specific surface area and pore size by adding lignocellulose and/or natural resin during preparation of the carrier. The carrier can be used for olefin epoxidation reaction, in particular to a carrier of a catalyst for preparing ethylene oxide by ethylene epoxidation.
The first aspect of 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 weight percent alumina trihydrate, based on the total weight of the solid mixture;
b. 5 to 70 wt% of pseudoboehmite 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. 0.1 to 40 wt% of lignocellulose and/or natural resin based on the total weight of the solid mixture;
step II, adding a binder aqueous solution into the solid mixture obtained in the step I to obtain an alpha-alumina carrier precursor mixture;
step III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, molding, drying and roasting to obtain the alpha-alumina carrier.
The second aspect of the present invention provides an α -alumina carrier obtained by the above-described production method.
The third aspect of the invention provides a silver catalyst for olefin epoxidation, which comprises a carrier and an 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 process comprises subjecting an olefin to an olefin epoxidation reaction under the action of the silver catalyst described above to obtain an epoxy compound.
In 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 natural resin is adjusted to realize that the prepared alpha-alumina carrier has larger specific surface area and pore diameter, particularly, the specific surface area of the prepared alpha-alumina carrier is 0.5-15.0 m 2 A/g, preferably from 1.0 to 5.0m 2 (ii)/g; the aperture of the carrier is 0.1-100.0 μm, preferably 0.2-50.0 μm; the water absorption of the carrier is more than or equal to 30.0 percent, and preferably 40.0 to 85.0 percent. The carrier can be used as a carrier of a silver catalyst 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 the embodiments of the present invention in detail. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are given by way of illustration and explanation only, not limitation.
The invention mixes, kneads, shapes, dries and roasts lignocellulose and/or natural resin, alumina trihydrate, pseudo-boehmite, fluoride and alkaline earth metal compound to obtain the alpha-alumina carrier, which can not only increase the specific surface area of the alpha-alumina carrier, but also increase the aperture of the alpha-alumina carrier by adjusting the dosage of the lignocellulose and/or natural resin, thus realizing the improvement of both the specific surface area and the aperture.
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 weight percent alumina trihydrate, based on the total weight of the solid mixture;
b. 5 to 70 wt% of pseudoboehmite 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. 0.1 to 40 wt% of lignocellulose and/or natural resin based on the total weight of the solid mixture;
step II, adding a binder aqueous solution into the solid mixture obtained in the step I to obtain an alpha-alumina carrier precursor mixture;
step III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, molding, 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 lignocellulosic and/or natural resin is preferably between 0.5% and 20% by weight of the total weight of the solid mixture.
In the preparation process of the alpha-alumina carrier, the alumina trihydrate can be finally converted into the alpha-alumina through dehydration and crystal phase conversion of alumina with different crystal phases. According to the invention, the alumina trihydrate may be selected from one or more of gibbsite, nordstrandite and bayerite; the weight of the alumina trihydrate is preferably between 40% and 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 formed, and the pseudo-boehmite can also be converted into the alpha-alumina in the high-temperature roasting process. According to the invention, the weight of the pseudoboehmite is preferably comprised between 10.0% and 45.0% by weight of the total weight of the solid mixture.
According to the present invention, in order to accelerate the crystal transformation of alumina, a fluorine-containing compound may be added during the preparation of the α -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 weight of the fluorine-containing compound is preferably 0.1 wt% to 10.0 wt% based on the total weight of the solid mixture.
According to the invention, the alkaline earth metal compound may be selected from one or more of oxides, hydroxides, sulfates, nitrates and oxalates of alkaline earth metals. The weight of the alkaline earth metal compound is preferably 0.1 to 2.0 wt% based on the total weight of the solid mixture.
In the method for preparing the alpha-alumina carrier, the aqueous solution of the binder is used for generating alumina sol with the pseudo-boehmite in the solid mixture, thereby binding the components together into paste which can be extruded and formed. The aqueous binder solution may be selected from at least one 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 amount of the aqueous binder solution and the content of the binder therein are limited to satisfy the requirements for binding and forming an extrudable paste, and specifically, the aqueous binder solution may be added in an amount of 5 to 60% by weight 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 of the invention with the aqueous binder solution need not be in a particular order, for example the fluoride in the solid mixture may be added to the solid mixture at the end of the addition with the binder.
The molding is carried out in a molding machine, and the shape of the molded alpha-alumina carrier can be selected from spherical shape, raschig ring shape, single-hole cylindrical shape, porous cylindrical shape, block shape, pill shape and leafy grass shape.
In 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, lubricating oil, and vegetable oil may be added to the solid mixture.
The drying process of the invention 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 24h
The roasting process of the invention is carried out in air atmosphere, preferably at the roasting temperature of 1100-1500 ℃ for 1-60 h.
The invention also provides the 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 A ratio of 1.0 to 5.0 m/g is preferred 2 (ii)/g; the aperture of the carrier is 0.1-100.0 μm, preferably 0.2-50.0 μm; the water absorption of the carrier is more than or equal to 30.0 percent, and preferably 40.0 to 85.0 percent.
The invention also provides a silver catalyst for olefin epoxidation, which comprises a carrier and an 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 and/or alkaline earth metals or compounds based on alkali and/or alkaline earth metals;
b) A rhenium metal and/or a rhenium-based compound; and
c) Optionally a rhenium co-promoter element selected from one or more of cerium, sulphur, molybdenum, chromium, oxyanions in salt or acid form.
The silver catalyst of the present invention can be prepared by a known manner or any conventional manner by those skilled in the art. Such as by impregnating the above-described alpha-alumina carrier with a solution containing sufficient amounts of an organic amine, a silver compound, an alkali metal promoter, an alkaline earth metal promoter, optionally a rhenium promoter and a co-promoter for the rhenium promoter.
According to a preferred embodiment of the present invention, the silver catalyst is prepared by a method comprising the steps of: i) impregnating an alpha-alumina carrier prepared according to the method of the invention with a solution containing sufficient amounts of an organic amine, a silver compound, an alkali metal promoter, an alkaline earth metal promoter, optionally a rhenium promoter and a co-promoter for the rhenium promoter; II) leaching the impregnation liquid; 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, tert-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 promoter can be one or more selected from 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 for the rhenium promoter may be selected from one or more of oxyanions of cerium, sulfur, molybdenum, chromium in salt or 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 additive accounts for 5-2000 ppm of the mass of the silver catalyst; the mass of the alkaline earth metal additive 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 preparation method of the silver catalyst, activation is carried out in 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 invention, in order to prepare the silver catalyst, firstly, silver nitrate aqueous solution and ammonium oxalate or oxalic acid aqueous solution react to separate out silver oxalate precipitate, the precipitate is filtered and washed by deionized water until no nitrate ions exist, then the silver oxalate is dissolved in organic amine aqueous solution, an alkali metal additive, an alkaline earth metal additive, an optional rhenium additive and a co-additive of the rhenium additive are added to prepare impregnation liquid, the obtained impregnation liquid is used for impregnating the alpha-alumina carrier prepared by the method, the impregnation liquid is leached and activated, and finally the silver catalyst is prepared.
In order to obtain silver catalysts with higher silver content and/or promoter content, the present invention may prepare silver-containing catalysts by one or more impregnation processes.
The assistants such as alkali metal, alkaline earth metal, rhenium assistant and rhenium co-assistant added in the preparation process of the silver catalyst can be deposited on the carrier before, simultaneously with or after silver impregnation, and can also 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 subjecting olefin to olefin epoxidation reaction under the action of the silver catalyst to obtain an epoxy compound. Wherein the olefins may include one or more of styrene, propylene, ethylene, and 1,3-butadiene. The olefin epoxidation reaction apparatus may be any apparatus capable of carrying out an epoxidation reaction.
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 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 pore diameter is measured by a mercury intrusion measuring instrument.
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, transferred into a kneader and added with 100 ml of dilute nitric acid (nitric acid: water =1:3, volume ratio)Kneading into paste capable of being extruded and formed. Finally, the paste is put into a forming machine, extruded into a single-hole cylindrical object, and 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 jar kiln for roasting, wherein the roasting temperature is 1300 ℃, roasting at a constant temperature for 20 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier. The specific surface area of the carrier was measured to be 1.2m 2 The pore size was 0.9 μm and the water absorption was 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 methyl cellulose 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 capable of being extruded and molded. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object which is dried for more than 24 hours at the temperature of 80-120 ℃ so that the free water content is reduced to be less than 10 percent. And then placing the dried single-hole cylindrical object into a bell jar kiln for roasting, wherein the roasting temperature is 1300 ℃, roasting at a constant temperature for 20 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier. The specific surface area of the carrier was measured to be 0.9m 2 The pore size was 1.1 μm and the water absorption was 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 are transferred into a kneader, 100 ml of dilute nitric acid (nitric acid: water =1:3, volume ratio) is added, and the mixture is kneaded into paste which can be extruded and molded. Finally, the paste is put into a forming machine, extruded into a single-hole cylindrical object, and 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-jar kiln for roasting, wherein the roasting temperature is 1300 ℃, roasting at a constant temperature for 20 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier. The specific surface area of the carrier was measured to be 1.8m 2 The pore size is 2.1 μm, the water absorption is 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 are transferred into a kneader, 100 ml of dilute nitric acid (nitric acid: water =1:3, volume ratio) is added, and the mixture is kneaded into paste which can be extruded and molded. Finally, the paste is put into a forming machine, extruded into a single-hole cylindrical object, and 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 jar kiln for roasting, wherein the roasting temperature is 1300 ℃, roasting at a constant temperature for 20 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier. The specific surface area of the carrier was measured to be 1.9m 2 (ii)/g, pore size 2.7 μm, water absorption 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 are transferred into a kneader, 100 ml of dilute nitric acid (nitric acid: water =1:3, volume ratio) is added, and the mixture is kneaded into paste which can be extruded and molded. Finally, the paste is put into a forming machine, extruded into a single-hole cylindrical object, and 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 jar kiln for roasting, wherein the roasting temperature is 1350 ℃, roasting at a constant temperature for 20 hours, and finally cooling to room temperature to obtain the alpha-alumina carrier. 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, transferred into a kneader, added with 100 ml of dilute nitric acid (nitric acid: water =1:3, volume ratio) and kneaded into paste capable of being extruded and molded. Finally, the paste is put into a forming machine and extruded into a single-hole cylindrical object which is dried for more than 24 hours at the temperature of 80-120 ℃ so that the free water content is reduced to be less than 10 percent. Then the dried single-hole cylindrical object is put into a bell jar kiln for roasting,the roasting temperature is 1230 ℃, the constant temperature roasting is carried out for 20 hours, and finally the alpha-alumina carrier is obtained after the cooling to the room temperature. The specific surface area of the carrier was measured to be 2.4m 2 Per g, pore size 3.2 μm, water absorption 82.1%.
As can be seen from comparison of example data and comparative example data, the performance of the alpha-alumina carrier can be improved by adding lignocellulose and/or natural resin in the preparation process of the carrier, and the specific surface area of the alpha-alumina carrier can be increased and the pore size of the alpha-alumina carrier can be increased by controlling the adding amount of the alpha-alumina carrier within a certain range. The alpha-alumina carrier prepared by the invention is an ideal catalyst carrier for the highly exothermic olefin epoxidation reaction, such as the reaction for preparing ethylene oxide by ethylene epoxidation, and can improve the catalytic performance of the catalyst used in the reaction.
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. A preparation method of an alpha-alumina carrier comprises the following steps:
step I, obtaining a solid mixture comprising the following components:
a. 5 to 90 weight percent alumina trihydrate, based on the total weight of the solid mixture;
b. 5 to 70 wt% of pseudoboehmite 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. 0.1 to 40 wt% of lignocellulose and/or natural resins based on the total weight of the solid mixture;
step II, adding a binder aqueous solution into the solid mixture obtained in the step I to obtain an alpha-alumina carrier precursor mixture;
step III, kneading the alpha-alumina carrier precursor mixture obtained in the step II uniformly, extruding, molding, drying and roasting to obtain the alpha-alumina carrier.
2. The process according to claim 1, wherein the natural resins are selected from rosin and/or mastic; the weight of the lignocellulose and/or natural resin accounts for 0.5-20 wt% of the total weight of the solid mixture.
3. The production method according to claim 1, wherein the alumina trihydrate is selected from one or more of gibbsite, nordstrandite, and bayerite; the weight of the alumina trihydrate accounts for 40.0-80.0 wt% of the total weight of the solid mixture.
4. The method of claim 1, wherein the weight of the pseudoboehmite is 10.0-45.0 wt% of the total weight of the solid mixture.
5. The production 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 weight of the fluorine-containing compound accounts for 0.1-10.0 wt% 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 weight of the alkaline earth metal compound is 0.1-2.0 wt% of the total weight of the solid mixture.
7. The production method according to claim 1, wherein the aqueous binder solution is selected from at least one 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 the water in the binder aqueous solution is 1; the addition amount of the aqueous binder solution is 5-60 wt% of the total weight of the solid mixture.
8. The preparation method according to claim 1, wherein the drying temperature is 80 to 120 ℃ and the drying time is 24 hours or more; the roasting temperature is 1100-1500 ℃, and the roasting time is 1-60 h.
9. An α -alumina carrier obtained by the production method according to any one of claims 1 to 8.
10. The α -alumina carrier as claimed in claim 9, wherein the α -alumina carrier has a specific surface area of 0.5 to 15.0m 2 A/g, preferably from 1.0 to 5.0m 2 (ii)/g; the pore diameter of the carrier is 0.1-100.0 μm, preferably 0.2-50.0 μm; the water absorption of the carrier is more than or equal to 30.0 percent, and preferably 40.0 to 85.0 percent.
11. A silver catalyst for olefin epoxidation, comprising a carrier and an active component silver supported on the carrier, wherein the carrier is the α -alumina carrier of claim 9 or 10.
12. A process for the epoxidation of an olefin, which process comprises subjecting an olefin, preferably selected from one or more of styrene, propylene, ethylene and 1,3-butadiene, to an epoxidation reaction under the action of the silver catalyst of claim 11 to obtain an epoxy compound.
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