CN115957732A

CN115957732A - Alpha-alumina carrier and preparation method thereof, silver catalyst for ethylene epoxidation and ethylene oxidation method

Info

Publication number: CN115957732A
Application number: CN202111187708.9A
Authority: CN
Inventors: 魏会娟; 王辉; 代武军; 李金兵; 廉括; 林伟; 李建华; 纪玉国; 高立新; 崔秉全
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2021-10-12
Filing date: 2021-10-12
Publication date: 2023-04-14

Abstract

The invention belongs to the field of catalysts, and relates to an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation and an ethylene oxidation method. alpha-A1 of the alpha-alumina carrier ₂ O ₃ The content is more than 90 wt%; the crushing strength is 80-350N/grain; the specific surface area is 1.5 to 3.0m ² (ii)/g; the water absorption is 30-70%; the pore volume is 0.30-0.75 mL/g; the crystal morphology of the alpha-alumina carrier comprises twoFlake crystals of various sizes, wherein the size of the larger flake crystals is 1.0 to 8.0 μm and the size of the smaller flake crystals is less than 1 μm. Compared with the prior art, the silver catalyst prepared by the alpha-alumina carrier provided by the invention has the advantages of higher activity and stability while ensuring selectivity when being used for the reaction of producing ethylene oxide by ethylene oxidation.

Description

Alpha-alumina carrier and preparation method thereof, silver catalyst for ethylene epoxidation and ethylene oxidation method

Technical Field

The invention belongs to the field of catalysts, and relates to an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation and an ethylene oxidation method. Specifically, the invention relates to an alpha-alumina carrier, a preparation method of the alpha-alumina carrier, the alpha-alumina carrier prepared by the method, a silver catalyst prepared by the alpha-alumina carrier and an ethylene oxidation method. More particularly, the present invention relates to an α -alumina carrier for a silver catalyst for ethylene oxidation to produce ethylene oxide, a method for preparing the same, a silver catalyst prepared from the same, and a method for producing ethylene oxide by ethylene oxidation using the same.

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. As petroleum resources are increasingly scarce and energy-saving, 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 properties of the silver catalyst are of great importance in relation to the properties of the carrier used for the catalyst and the preparation process. Currently, alpha-alumina is generally used as a carrier for silver catalysts. The indexes for measuring the performance of the alpha-alumina carrier mainly comprise: compressive strength, specific surface area, pore volume, water absorption, etc. of the carrier. The proper compressive strength can ensure that the catalyst can bear reaction pressure for a long time; the appropriate specific surface area provides a position for deposition of the active component and the auxiliary agent; the proper pore volume provides a proper space for ethylene oxidation, so that the reaction heat can be dissipated in time; and the appropriate water absorption rate can control the loading amount of the active component and the catalytic promoter on the carrier. Due to various reasons, unqualified alpha-alumina carriers are inevitably produced in the production, and the carriers cannot be continuously used at present and are treated as 'three wastes'.

In 2020, the world demand for silver catalysts is about 6000 tons/year, while the national demand is about 2000 tons/year, and by the expectation of 2022, the demand for silver catalysts in our country is about 4600 tons/year. The used waste silver catalyst is subjected to recovery treatment of silver and auxiliary agent components, and if the rest carrier part and the unqualified alpha-alumina carrier can be reasonably utilized, the waste of resources and environmental pollution can be avoided. Therefore, the development of the method for recycling the waste carriers has very important practical significance.

Disclosure of Invention

In view of the foregoing circumstances of the prior art, the inventors of the present invention have conducted extensive and intensive studies in the field of silver catalysts and carrier preparations thereof, and as a result, have found that α -A1 having a specific particle size range obtained by pulverizing a waste carrier containing α -alumina as a main component ₂ O ₃ When the powder is used as a raw material to prepare the carrier, not only can the resource be recycled, but also the compression strength and the water absorption of the carrier can be ensured, meanwhile, the carrier has a part of relatively small flaky crystal morphology and relatively high specific surface area, and when the silver catalyst prepared by the carrier is used for preparing ethylene oxide by ethylene oxidation, the selectivity is ensured, and simultaneously, the activity and the stability are obviously improved. Based on the above, the invention aims to provide an alpha-alumina carrier and a preparation method thereof, a silver catalyst for ethylene epoxidation and an ethylene oxidation method. The alpha-alumina carrier of the invention shows good activity and stability in the process of producing ethylene oxide by oxidizing ethylene after being loaded with silver and preferably various active components to prepare a silver catalyst.

In a first aspect of the invention, there is provided an alpha-alumina carrier, the alpha-A1 of which ₂ O ₃ The content is 90 wt% or more; the crushing strength is 80-350N/grain, preferably 100-300N/grain; the specific surface area is 1.5 to 3.0m ² A ratio of 2.0 to 3.0 m/g ² (iv) g; the water absorption rate is 30-70%, preferably 45-70%; the pore volume is 0.30-0.75 mL/g, preferably 0.45-0.70 mL/g; the crystal morphology of the alpha-alumina carrier comprises flaky crystals with two sizes, wherein the size of the larger flaky crystal is 1.0-8.0 mu m, preferably 3.0-6.0 mu m, and the size of the smaller flaky crystal is less than 1 mu m, preferably less than 0.8 mu m.

The second aspect of the present invention provides a method for preparing an α -alumina carrier, comprising the steps of:

s1, crushing waste carriers taking alpha-alumina as a main component into alpha-A1 ₂ O ₃ Powder, wherein the content of alpha-alumina in the waste carrier is more than 90 wt%; the alpha-A1 ₂ O ₃ The granularity of the powder is 50-120 mu m;

s2, the alpha-A1 obtained in the step S1 ₂ O ₃ Powder, trihydrate A1 ₂ O ₃ Pseudo-water A1 ₂ O ₃ Mixing a fluoride mineralizer, a pore-forming agent and a combustible lubricating material to prepare a solid mixture, and mixing the solid mixture with a binder to obtain a mixture; wherein, the alpha-A1 ₂ O ₃ The powder is used in an amount of alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ 3 to 20% by weight, preferably 5 to 15% by weight, based on the total weight;

s3, molding the mixture obtained in the step S2 to obtain a molded body;

and S4, drying and roasting the formed body obtained in the step S3 to obtain the alpha-alumina carrier.

A third aspect of the present invention provides an α -alumina carrier obtained by the above-described production method.

The fourth 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 alpha-alumina carrier.

A fifth aspect of the invention provides a process for the oxidation of ethylene, the process comprising: and (2) carrying out ethylene epoxidation reaction on ethylene in the presence of the alpha-alumina carrier and/or the silver catalyst to obtain ethylene oxide.

The alpha-A1 with a specific particle size range is obtained by crushing waste carriers taking alpha-alumina as a main component ₂ O ₃ The powder is used as a raw material to prepare the carrier, so that not only can the resource be recycled, but also the compressive strength and the water absorption of the carrier can be ensured, and the carrier has a part of relatively small flaky crystal morphology and a relatively high specific surface area. Compared with the prior art, the silver catalyst prepared by the alpha-alumina carrier provided by the invention has the advantages of higher activity and stability while ensuring selectivity when being used for the reaction of producing ethylene oxide by ethylene oxidation.

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 preferred embodiment of the invention, are given by way of illustration and explanation only, not limitation.

The invention provides an alpha-alumina carrier, and alpha-A1 of the alpha-alumina carrier ₂ O ₃ The content is more than 90 wt%; the crushing strength is 80 to 350N/grain, preferably 100 to 300N/grain; the specific surface area is 1.5 to 3.0m ² A ratio of 2.0 to 3.0 m/g ² (ii)/g; the water absorption is 30 to 70 percent, preferably 45 to 70 percent; the pore volume is 0.30-0.75 mL/g, preferably 0.45-0.70 mL/g; the crystal morphology of the alpha-alumina carrier comprises flaky crystals with two sizes, wherein the size of the larger flaky crystal is 1.0-8.0 mu m, preferably 3.0-6.0 mu m, and the size of the smaller flaky crystal is less than 1 mu m, preferably less than 0.8 mu m.

In the invention, the lateral crushing strength of the carrier is obtained by selecting a carrier sample and measuring the radial crushing strength and then averaging by adopting a DL II type intelligent particle strength measuring instrument; the specific surface area is measured by adopting a nitrogen physical adsorption BET method; the water absorption was determined by boiling; the pore volume is measured by a mercury injection method; the average crystal size was determined by scanning electron microscopy.

The invention also provides a preparation method of the alpha-alumina carrier, which comprises the following steps:

s2, the alpha-A1 obtained in the step S1 is subjected to ₂ O ₃ Powder, trihydrate A1 ₂ O ₃ Pseudo-water A1 ₂ O ₃ Mixing a fluoride mineralizer, a pore-forming agent and a combustible lubricating material to prepare a solid mixture, and mixing the solid mixture with a binder to obtain a mixture; wherein, the alpha-A1 ₂ O ₃ The powder is used in an amount of alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ 3 to 20% by weight, preferably 5 to 15% by weight, based on the total weight;

s3, molding the mixture obtained in the step S2 to obtain a molded body;

The inventors of the present invention found that: alpha-A1 with specific particle size range obtained by crushing waste carrier with alpha-alumina as main component ₂ O ₃ The powder is used as a raw material to prepare the carrier, so that not only can the resource be recycled, but also the compressive strength and the water absorption of the carrier can be ensured, and meanwhile, part of the carrier has a smaller flaky crystal morphology and a higher specific surface area.

According to the invention, the waste carrier taking alpha-alumina as a main component can be an unqualified alpha-alumina carrier from laboratories or industrial production, or can be the rest carrier part of a catalyst taking alpha-alumina as a carrier after industrial use and subsequent active component recovery; the alpha-alumina supported catalyst is preferably a silver catalyst for olefin epoxidation. The waste carrier taking the alpha-alumina as the main component is crushed to obtain alpha-A1 ₂ O ₃ When the powder is used as a raw material for preparing a carrier, besides conventional flaky crystals with the size of 1.0-8.0 microns, the carrier has a large number of tiny wafers with the size of less than 1 micron, so that the compressive strength and the water absorption of the carrier can be ensured, and the carrier has a relatively high specific surface area.

According to a preferred embodiment of the invention, the trihydrate A1 ₂ O ₃ The granularity of (A) is 20-200 mu m; based on the total weight of the solid mixture, the alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ The total amount is 40 to 85 wt.%, preferably 45 to 80 wt.%; the trihydrate A1 ₂ O ₃ In an amount of alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ 80 to 97% by weight, preferably 85 to 95% by weight, based on the total weight. The trihydrate A1 ₂ O ₃ Conversion to stable alpha-A1 during high temperature calcination ₂ O ₃ To be alpha-A1 ₂ O ₃ A portion of a carrier.

According to a preferred embodiment of the invention, said pseudo-water A1 ₂ O ₃ The particle size of (A) is 1-120 mu m; the pseudo-monohydrate A1 is based on the total weight of the solid mixture ₂ O ₃ The amount of (B) is 10 to 55 wt%, preferably 15 to 50 wt%. The pseudo-water A1 ₂ O ₃ Reacting with acid during kneading with binder such as acid to convert into sol, serving as binder, and converting into stable alpha-A1 during high temperature calcination ₂ O ₃ To be alpha-A1 ₂ O ₃ A portion of a carrier. According to the invention, the binder and the pseudo-monohydrate A1 are added ₂ O ₃ Generating aluminum sol, and bonding the components together to form paste which can be extruded and molded. The binder may be added in an amount conventional in the art, and particularly preferably, the binder is added in an amount of 25 to 60 wt% based on the total weight of the solid mixture. In the present invention, the kind of the binder is well known to those skilled in the art, and includes, for example, an acid, which is usually provided in the form of an aqueous acid solution, preferably an aqueous nitric acid solution, in which the weight ratio of nitric acid to water 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 A1 ₂ O ₃ All or part of the aluminum sol is provided in the form of an aluminum sol.

The addition of the fluoride mineralizer has the effects of accelerating the crystal transformation of the alumina and reducing pores below 0.5 mu m. According to a preferred embodiment of the present invention, the fluoride mineralizer is one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite, and is used in an amount of 0.05 to 8 wt%, preferably 0.1 to 5 wt%, based on the total weight of the solid mixture.

The pore-forming agent is added to adjust the pore structure of the carrier and form a certain pore size distribution. According to a preferred embodiment of the present invention, the pore-forming agent is one or more of petroleum coke, activated carbon and graphite; preferably, the pore-forming agent is petroleum coke; the pore-forming agent is used in an amount of 0.05 to 10 wt%, preferably 0.1 to 8 wt%, based on the total weight of the solid mixture.

The addition of the burnout lubricating material is to ensure that the kneaded material is easy to form and granulate, oxidation reaction is generated in the roasting process of the material, generated gas escapes, and impurities are not introduced or introduced as little as possible when the burnout lubricating material is prepared into a carrier, so that the performance of the catalyst is not influenced. According to a preferred embodiment of the present invention, the burnout lubricant is petrolatum and/or white oil; the burnout lubricant is used in an amount of 0.01 to 8 wt%, preferably 0.01 to 5 wt%, based on the total weight of the solid mixture.

According to the invention, in step S3, the mixture obtained in step S2 is kneaded to give a paste, which is then extruded to give a shaped body, which can be carried out according to the techniques customary in the art. Wherein, the shape of the formed body can be annular, spherical, cylindrical or porous cylindrical.

According to the present invention, in step S4, drying and calcination may be performed in a conventional manner in the art. Preferably, the molded article may be dried to contain 10 wt% or less of free water, the drying temperature may be 80 to 120 ℃, and the drying time may be controlled to 1 to 24 hours depending on the moisture content. The calcination makes the alumina completely converted into alpha-A1 ₂ O ₃ The roasting time can be 1 to 20 hours, preferably 2 to 15 hours; the maximum firing temperature may be 1200 to 1500 ℃.

The invention provides the alpha-alumina carrier prepared by the preparation method.

The α -alumina support preferably has the following characteristics: alpha-A1 ₂ O ₃ The content is 90 wt% or more; the crushing strength is 80-350N/grain, preferably 100-300N/grain; the specific surface area is 1.5 to 3.0m ² A ratio of 2.0 to 3.0 m/g ² (ii)/g; water absorption of30 to 70 percent, preferably 45 to 70 percent; the pore volume is 0.30-0.75 mL/g, preferably 0.45-0.70 mL/g; the crystal morphology of the alpha-alumina carrier comprises flaky crystals with two sizes, wherein the size of the larger flaky crystal is 1.0-8.0 mu m, preferably 3.0-6.0 mu m, and the size of the smaller flaky crystal is less than 1 mu m, preferably less than 0.8 mu m.

The invention further 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 alpha-alumina carrier;

preferably, the 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.

According to an embodiment of the present invention, in the silver catalyst, the silver is contained in an amount of 5 to 37% by mass, preferably 8 to 32% by mass, based on the total weight of the silver catalyst; the mass content of 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-adjuvant is 0 to 1500ppm, preferably 5 to 1000ppm, based on the metals in the co-adjuvant.

The silver catalyst of the present invention can be prepared in a conventional manner, for example, by impregnating the above-mentioned α -alumina carrier with a solution containing a silver compound, an organic amine, an alkali metal assistant, an alkaline earth metal assistant, a rhenium assistant and optionally a co-assistant thereof.

Wherein the organic amine 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 cesium or a combination of any two thereof, such as a nitrate, sulfate or hydroxide thereof, or a combination of any two or more of the foregoing compounds, preferably cesium sulfate and/or cesium 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 one embodiment of the present invention, the preparation method of the silver catalyst comprises the steps of:

(1) Impregnating the porous alpha-alumina carrier with a solution containing sufficient amounts of a silver compound, an organic amine, an alkali metal auxiliary agent, an alkaline earth metal auxiliary agent, a rhenium-containing auxiliary agent and a co-auxiliary agent 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, and then the auxiliary agent is added to prepare impregnation liquid; then impregnating the alpha-alumina carrier with the prepared impregnation liquid, draining, keeping the alpha-alumina carrier in air flow or mixed gas of nitrogen and oxygen with the oxygen content not more than 21 wt percent (such as 8 wt percent of oxygen) at the temperature of 180-700 ℃, preferably 200-500 ℃ for 0.5-120 minutes, preferably 1-60 minutes, and carrying out thermal decomposition to prepare the finished product of the silver catalyst.

The present invention also provides a process for the oxidation of ethylene, which process comprises: ethylene is subjected to ethylene epoxidation reaction in the presence of the above-mentioned alpha-alumina carrier and/or the above-mentioned silver catalyst to obtain ethylene oxide. The ethylene oxidation 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.

In the following examples and comparative examples:

each silver catalyst was tested for initial performance and stability using a laboratory reactor (hereinafter referred to simply as a "microreaction") evaluation unit. 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 an inert filler, so that a catalyst bed layer is positioned in a constant temperature area of a heating sleeve.

The assay conditions for the activity and selectivity used are shown in table 1:

TABLE 1

When the reaction conditions are stably achieved, the gas composition at the inlet and outlet of the reactor is continuously measured. The measurement results were corrected for volume shrinkage and the selectivity S was calculated as follows:

wherein, delta EO is the difference of the concentration of ethylene oxide in the outlet gas and the inlet gas of the reactor, delta CO ₂ The carbon dioxide concentration difference between the outlet gas and the inlet gas of the reactor is obtained, and the average of more than 10 groups of test data is taken as the test result of the same day.

Side crush strength of alumina support: and (3) selecting an alumina carrier sample by adopting a DL II type intelligent particle strength tester, measuring the radial crushing strength, and then taking an average value to obtain the product.

Water absorption: measured by boiling method.

Specific surface area: measured by nitrogen physical adsorption BET method.

Pore volume: measured by mercury intrusion method.

Average crystal size: the measurement is carried out by adopting a scanning electron microscope observation method.

Preparation example

Crushing waste carrier (alpha-alumina content is more than 90 wt%) using alpha-alumina as main component by instrument, sieving, selecting 50-120 micrometer granules as alpha-A1 required by experiment ₂ O ₃ The powder is subsequently called alpha-A1 obtained by crushing waste carriers ₂ O ₃ Powder ". alpha-A1 not so limited in comparative examples hereinafter ₂ O ₃ Then refers to fresh, unused alpha-A1 ₂ O ₃ 。

Examples 1-5 are provided to illustrate the preparation of alumina supports provided by the present invention.

Example 1

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 388g of alpha-A1 obtained by crushing waste carriers ₂ O ₃ Powder 12g, pseudo-monohydrate A1 of 1-120 μm ₂ O ₃ 100g of magnesium fluoride, 28g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be mixed evenlyHomogenizing, transferring into a kneader, adding 27g vaseline and 200mL dilute nitric acid (nitric acid: water = 1: 5, by weight), and kneading into paste capable of being extruded. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. The kneaded and molded carrier is put into a bell jar kiln, is heated to 1400 ℃ from room temperature for 33 hours and is calcined for 5 hours at 1400 ℃ to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier physical property data are shown in table 1 below.

Example 2

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 380g of alpha-A1 obtained by crushing waste carriers ₂ O ₃ 2g of powder, 1-120 μm of pseudomonohydrate A1 ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. The kneaded and molded carrier is put into a bell jar kiln, is heated to 1400 ℃ from room temperature for 33 hours and is calcined for 5 hours at 1400 ℃ to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Example 3

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 360g, alpha-A1 obtained by crushing waste carriers ₂ O ₃ 40g of powder, pseudo-monohydrate A1 of 1 to 120 μm ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then are transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Kneading the above-mentioned formed carrierPlacing into a bell jar kiln, increasing the temperature from room temperature to 1400 ℃ over 33 hours, and calcining at 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier physical property data are shown in table 1 below.

Example 4

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 340g of alpha-A1 obtained by crushing waste carriers ₂ O ₃ Powder 60g, pseudo-monohydrate A1 of 1-120 mu m ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Example 5

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 320g, alpha-A1 obtained by crushing waste carriers ₂ O ₃ 80g of powder, pseudomonohydrate A1 of 1-120 μm ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Examples 6-10 are provided to illustrate the preparation of silver catalysts provided by the present invention.

Example 6

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 wt% silver and about 15 wt% 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 carrier sample prepared in example 1 was placed in a vacuum-evacuable container, vacuum-evacuated to 10mmHg or more, the immersion liquid was introduced, and the mixture was held for 30 minutes, and the excess solution was leached out. And heating the impregnated carrier in air flow at 450 ℃ for 3min, and cooling to obtain the silver catalyst C-1.

Example 7

The same as example 6 except that the carrier sample prepared in example 1 was replaced with the carrier sample prepared in example 2. The silver catalyst obtained is C-2.

Example 8

The same as example 6 except that the carrier sample prepared in example 3 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained is C-3.

Example 9

The same as example 6 except that the carrier sample prepared in example 1 was replaced with the carrier sample prepared in example 4. The silver catalyst obtained was C-4.

Example 10

The same as example 6 except that the carrier sample prepared in example 5 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained is C-5.

Comparative example 1

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

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 400g pseudo-monohydrate A1 of 1-120 mu m ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then are transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Comparative example 2

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 392g, alpha-A1 obtained by crushing waste carriers ₂ O ₃ Pseudo-monohydrate A1 in powder 8g, 1-120 micron ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier physical property data are shown in table 1 below.

Comparative example 3

20 is to be provided200 μm trihydrate A1 ₂ O ₃ 280g, alpha-A1 obtained by crushing waste carriers ₂ O ₃ 120g of powder, pseudo-monohydrate A1 of 1-120 mu m ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Comparative example 4

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 360g，1～10μmα-A1 ₂ O ₃ 40g, 1-120 μm pseudo-monohydrate A1 ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. The kneaded and molded carrier is put into a bell jar kiln, is heated to 1400 ℃ from room temperature for 33 hours and is calcined for 5 hours at 1400 ℃ to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier physical property data are shown in table 1 below.

Comparative example 5

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 360g，10～200μmα-A1 ₂ O ₃ 40g pseudo-monohydrate A1 of 1-120 μm ₂ O ₃ 100g of fluorine28g of magnesium oxide and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then are transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. The kneaded and molded carrier is put into a bell jar kiln, is heated to 1400 ℃ from room temperature for 33 hours and is calcined for 5 hours at 1400 ℃ to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier property data are shown in table 1 below.

Comparative example 6

Mixing 20-200 μm trihydrate A1 ₂ O ₃ 360g，50～120μmα-A1 ₂ O ₃ 40g, 1-120 μm pseudo-monohydrate A1 ₂ O ₃ 100g of magnesium fluoride and 45g of petroleum coke are put into a mixer to be uniformly mixed, and then are transferred into a kneader, 27g of vaseline and 200mL of dilute nitric acid (nitric acid: water = 1: 5, weight ratio) are added, and the mixture is kneaded into paste which can be extruded and formed. Extruding into seven-hole column with outer diameter of 8.0mm, length of 6.0mm and inner diameter of 1.0mm, and oven drying at 100 deg.C for more than 2 hr to reduce free water content to below 10 wt%. Placing the kneaded and molded carrier into a bell jar kiln, raising the temperature from room temperature to 1400 ℃ for 33 hours, and calcining the carrier at the temperature of 1400 ℃ for 5 hours to obtain white alpha-A1 ₂ O ₃ And (3) a carrier. The measured carrier physical property data are shown in table 1 below.

Comparative example 7

This comparative example serves to illustrate the preparation of a reference silver catalyst.

The same as example 6 except that the carrier sample prepared in comparative example 1 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-1.

Comparative example 8

The same as example 6 except that the carrier sample prepared in comparative example 2 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-2.

Comparative example 9

The same as example 6 except that the carrier sample prepared in comparative example 3 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-3.

Comparative example 10

The same as example 6 except that the carrier sample prepared in comparative example 4 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-4.

Comparative example 11

The same as example 6 except that the carrier sample prepared in comparative example 5 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-5.

Comparative example 12

The same as example 6 except that the carrier sample prepared in comparative example 6 was used in place of the carrier sample prepared in example 1. The silver catalyst obtained was DC-6.

TABLE 1

Test example

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 2

As can be seen from the data in tables 1 and 2, the carrier provided by the method of the present invention has both larger plate-like crystals and smaller plate-like crystals, and has higher specific surface area while having higher compressive strength and water absorption. The catalyst prepared by the carrier of the invention has wide application prospect, ensures selectivity, obviously reduces reaction temperature (namely improves reaction activity), obviously reduces increment of the reaction temperature within 50 days (namely improves stability).

While embodiments of the present invention have been described above, the above description is illustrative, not exhaustive, and not limited to the disclosed embodiments. 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

1. The alpha-alumina carrier is characterized in that alpha-A1 of the alpha-alumina carrier ₂ O ₃ The content is 90 wt% or more; the crushing strength is 80-350N/grain, preferably 100-300N/grain; the specific surface area is 1.5 to 3.0m ² A ratio of 2.0 to 3.0 m/g ² (ii)/g; the water absorption rate is 30-70%, preferably 45-70%; pore volume0.30-0.75 mL/g, preferably 0.45-0.70 mL/g; the crystal morphology of the alpha-alumina carrier comprises flaky crystals with two sizes, wherein the size of the larger flaky crystal is 1.0-8.0 mu m, preferably 3.0-6.0 mu m, and the size of the smaller flaky crystal is less than 1 mu m, preferably less than 0.8 mu m.

2. A preparation method of an alpha-alumina carrier is characterized by comprising the following steps:

s3, molding the mixture obtained in the step S2 to obtain a molded body;

3. The method for preparing an alpha-alumina carrier according to claim 2, wherein the waste carrier using alpha-alumina as a main component is an unqualified alpha-alumina carrier, or the rest carrier part of the catalyst using alpha-alumina as a carrier after industrial use and subsequent active component recovery; the alpha-alumina supported catalyst is preferably a silver catalyst for olefin epoxidation.

4. Alpha-alumina according to claim 2 or 3A method for preparing a carrier, wherein the trihydrate A1 ₂ O ₃ The granularity of (A) is 20-200 mu m; based on the total weight of the solid mixture, the alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ The total amount is 40 to 85 wt.%, preferably 45 to 80 wt.%; the trihydrate A1 ₂ O ₃ In an amount of alpha-A1 ₂ O ₃ Powder and trihydrate A1 ₂ O ₃ 80 to 97% by weight, preferably 85 to 95% by weight, based on the total weight.

5. The method for preparing an α -alumina carrier according to claim 2 or 3, wherein said pseudo-monohydrate A1 is used as a carrier ₂ O ₃ The particle size of (A) is 1-120 mu m; the pseudo-monohydrate A1 is used as the reference based on the total weight of the solid mixture ₂ O ₃ The amount of (B) is 10 to 55 wt%, preferably 15 to 50 wt%.

6. The method for preparing an α -alumina support according to claim 2 or 3, wherein the fluoride mineralizer is one or more of hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, and cryolite; the fluoride mineralizer is used in an amount of 0.05 to 8 wt%, preferably 0.1 to 5 wt%, based on the total weight of the solid mixture.

7. The method for preparing an α -alumina support according to claim 2 or 3, wherein the pore former is one or more of petroleum coke, activated carbon and graphite; preferably, the pore-forming agent is petroleum coke; the pore-forming agent is used in an amount of 0.05 to 10 wt%, preferably 0.1 to 8 wt%, based on the total weight of the solid mixture.

8. The method of preparing an alpha-alumina support according to claim 2 or 3, wherein the burnout lubricant is petrolatum and/or white oil; the burnout lubricant is used in an amount of 0.01 to 8 wt.%, preferably 0.01 to 5 wt.%, based on the total weight of the solid mixture.

9. The method for preparing the alpha-alumina carrier according to claim 2 or 3, wherein the binder is an aqueous acid solution, preferably an aqueous nitric acid solution, and the weight ratio of nitric acid to water in the aqueous nitric acid solution is 1 (1.25-10); the addition amount of the binder is 25 to 60 weight percent of the total weight of the solid mixture.

10. The method for preparing an α -alumina carrier according to claim 2 or 3, wherein said binder and pseudo-monohydrate A1 ₂ O ₃ All or part of the aluminum sol is provided in the form of an aluminum sol.

11. An α -alumina support obtained by the production method according to any one of claims 2 to 10.

12. The α -alumina support as claimed in claim 11, wherein the α -alumina support has an α -A1 ₂ O ₃ The content is more than 90 wt%; the crushing strength is 80 to 350N/grain, preferably 100 to 300N/grain; the specific surface area is 1.5 to 3.0m ² A ratio of 2.0 to 3.0 m/g ² (iv) g; the water absorption rate is 30-70%, preferably 45-70%; the pore volume is 0.30-0.75 mL/g, preferably 0.45-0.70 mL/g; the crystal morphology of the alpha-alumina carrier comprises flaky crystals with two sizes, wherein the size of the larger flaky crystal is 1.0-8.0 mu m, preferably 3.0-6.0 mu m, and the size of the smaller flaky crystal is less than 1 mu m, preferably less than 0.8 mu m.

13. A silver catalyst for ethylene epoxidation, comprising a carrier and an active component silver supported on the carrier, characterized in that the carrier is an α -alumina carrier according to claim 1, 11 or 12;

preferably, the silver catalyst further comprises:

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

rhenium metal and/or rhenium-based compounds; and

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

14. A process for the oxidation of ethylene, the process comprising: ethylene is subjected to an ethylene epoxidation reaction in the presence of an alpha-alumina support according to claim 1, 11 or 12 and/or a silver catalyst according to claim 13 to obtain ethylene oxide.