CN100577289C - Carrier of silver catalyst for ethylene oxide production, its preparation method and application - Google Patents

Abstract

The present invention relates to an alumina carrier for a silver catalyst used in the oxidation of ethylene to produce ethylene oxide, a preparation method thereof and a silver catalyst prepared from the carrier, and also relates to the use of the catalyst in the production of ethylene oxide by the oxidation of ethylene use. In the preparation of the carrier of the present invention, a certain particle size of α-alumina trihydrate, α-alumina pseudomonohydrate, a certain amount of burnable carbonaceous material, flux, fluoride, and optional compound phase of heavy alkaline earth metal are used. Mixing, adding binder and water after mixing evenly, kneading evenly, extruding, drying and roasting to make α-alumina carrier. The specific surface of the carrier of the invention is 0.2-2.0m ² /g, the pore volume is 0.35-0.85ml/g, the water absorption rate is ≥ 30%, and the crushing strength is 30-120N/grain. The carrier is impregnated with the solution of silver amine complex, alkali metal compound and alkaline earth metal compound, dried and activated to prepare silver catalyst for ethylene epoxidation to prepare oxirane.

Description

Carrier of silver catalyst for ethylene oxide production, its preparation method and application

technical field

The present invention relates to a kind of carrier for silver catalyst, its preparation method and application thereof, more specifically the present invention relates to a kind of alumina carrier for silver catalyst of ethylene oxidation production ethylene oxide, its preparation method and The silver catalyst prepared by the carrier also relates to the application of the catalyst in ethylene oxidation to produce ethylene oxide.

Background technique

Under the action of silver catalyst, the oxidation of ethylene mainly produces ethylene oxide, and at the same time, side reactions produce carbon dioxide and water. Among them, activity, selectivity and stability are the main performance indicators of silver catalyst. The so-called activity refers to the reaction temperature required when the production process of ethylene oxide reaches a certain reaction load. The lower the reaction temperature, the higher the activity of the catalyst. The so-called selectivity refers to the ratio of the moles of ethylene converted into ethylene oxide in the reaction to the total reaction moles of ethylene. The so-called stability is expressed as the decline rate of activity and selectivity, and the smaller the decline rate, the better the stability of the catalyst. The use of silver catalysts with high activity, high selectivity and good stability in the process of ethylene oxidation to produce ethylene oxide can greatly improve economic benefits, so the manufacture of silver catalysts with high activity, high selectivity and good stability is a silver catalyst research main direction. The performance of the silver catalyst not only has an important relationship with the composition and preparation method of the catalyst, but also has an important relationship with the performance of the carrier used in the catalyst and the preparation method.

The preparation method of the silver catalyst mainly includes two processes of preparing a porous support (such as alumina) and applying active components and auxiliary agents to the support.

In the preparation process of silver catalyst, for the support with α-Al ₂ O ₃ as the main component, suitable specific surface and pore structure are required. On the one hand, it should provide enough space for ethylene epoxidation reaction, Diffusion of the reaction heat is also beneficial to the timely desorption of the reaction product ethylene oxide, avoiding deep oxidation to generate by-product carbon dioxide. In the prior art, pore-forming agents, such as petroleum coke, walnut shell powder, carbon powder and other organic burnable materials, are added during the production process of the alumina carrier, so that the carrier can obtain an ideal pore structure and specific surface area, so as to improve the performance of the catalyst . However, the addition of pore-forming agents can also bring negative effects, because the incomplete combustion residues of pore-forming agents during the calcination of the support can affect the performance of the catalyst. U.S. Patent No. 5801259 (corresponding to EP0900128, WO9740933 and CN1216940, 1998, Shell) and US5733842 (corresponding to EP0900126, CN1216939 and WO9740932, 1998, Norton) have all proposed the alumina carrier production method that does not use pore forming agent, with at least 80 weight % alumina, 0.01-10% by weight of alkaline earth metal oxides, 0.01-10% by weight of silicon dioxide, 0.01-15% by weight of zirconia, etc. to prepare the carrier, and the particle size of the ceramic components is carefully selected (15-120 μm and 1 ~15 μm) to ensure that the bulk density of the dry support precursor is not greater than that of the calcined support to ensure the required porosity.

Although the above-mentioned patent documents do not add pore-forming agents to the carrier raw materials in order to reduce the impact of residual metal ion impurities after the pore-forming agent is burned on the performance of the catalyst, and select raw materials with different particle sizes for use in combination to obtain an ideal pore structure, but This method does not bring any improvement to the activity and selectivity of the catalyst, so this field still needs to improve the manufacturing method of the carrier, so as to facilitate the manufacture of a silver catalyst with better performance.

Chinese Patent Application Publication No. CN1634652 discloses a method for manufacturing an ethylene oxide silver catalyst carrier without adding a pore-forming agent. According to this method, both the activity and the selectivity of the resulting catalyst can be improved. However, the water absorption rate of the carrier prepared by this method is low, which is not conducive to the deposition of active components and additives; moreover, there are many pores less than 5 μm, which will have some adverse effects on the mass transfer and heat transfer in the direct oxidation reaction process of ethylene.

Therefore, it is necessary to obtain a carrier with an ideal pore structure and specific surface area while reducing the negative impact of the pore-forming agent as much as possible, and further obtain a catalyst with good performance.

Summary of the invention

In view of the above-mentioned state of the art, the inventors of the present invention have carried out extensive and in-depth research in the field of silver catalysts, and believe that as the alumina containing crystal water is converted into α-Al ₂ O ₃ by roasting at high temperature, the loss of crystal water Pores of a certain size can be formed in the support, and the size and number of these pores have been found to be suitable for ethylene epoxidation reactions. It is further found that when alumina trihydrate and alumina monohydrate are used as raw materials to manufacture carriers, ideal specific surface and pore structure can still be obtained without adding too much pore-forming agent, which meets the requirements of making porous and heat-resistant ethylene oxide silver catalysts. carrier requirements. Compared with the carrier made by adding more pore-forming agents, the silver catalyst made by the present invention has higher strength and activity; compared with the carrier made without adding pore-forming agents, the silver catalyst made by the present invention has higher selectivity High, especially suitable for the reaction of ethylene oxide to produce ethylene oxide.

A heavy alkaline earth metal compound is optionally added to the alumina raw material to make a carrier, and a solution prepared by impregnating a silver compound, an organic amine and a specific auxiliary agent is prepared. After heat treatment in an oxygen-containing mixed gas, the silver catalyst prepared in The activity and selectivity in the oxidation reaction have been improved.

It was therefore an object of the present invention to provide a novel support from which silver catalysts exhibit good activity and selectivity in the oxidation of ethylene to ethylene oxide.

Another object of the present invention is to provide a preparation method of the above carrier.

Another object of the present invention is to provide a silver catalyst prepared from the above carrier.

Another object of the present invention is to provide the application of the above-mentioned silver catalyst in the oxidation of ethylene to produce ethylene oxide.

These and other objects, features and advantages of the present invention will become more apparent after reading this specification.

Detailed description of the invention

One aspect of the present invention provides a method for preparing a porous α-alumina carrier for silver catalysts used in ethylene oxidation to produce ethylene oxide, comprising the steps of:

1) Prepare a mixture with the following composition:

a) 50 to 500 mesh α-Al ₂ O ₃ trihydrate of 5 to 90% by weight based on the total weight of the solid mixture;

b) Pseudo monohydrate Al ₂ O ₃ with a particle size greater than 200 mesh of 5 to 70% by weight based on the total weight of the solid mixture;

c) more than 0 to 6.6% by weight of combustible carbonaceous materials based on the total weight of the solid mixture;

d) 0.01 to 3.0% by weight of a flux based on the total weight of the solid mixture;

e) 0.01 to 3.0% by weight of fluoride mineralizer based on the total weight of the solid mixture;

f) 0 to 5.0% by weight of heavy alkaline earth metal-containing compounds based on the total weight of the solid mixture;

g) a binder of 25 to 60% by weight based on the total weight of the above solid mixture; and

h) appropriate amount of water;

II) kneading the mixture obtained in I) uniformly and extruding; and

III) drying the product obtained in II), and then calcining at high temperature into α-Al ₂ O ₃ .

The porous alumina carrier prepared by the present invention has the following characteristics: the specific surface is 0.2m ² /g-2.0m ² /g, preferably 0.5m ² /g-1.5m ² /g; the pore volume is 0.35-0.85ml/g, Preferably 0.40-0.80ml/g; water absorption ≥ 30%, preferably ≥ 35%; and crushing strength 30N/grain-120N/grain, preferably 35N/grain-90N/grain.

Another aspect of the present invention provides a novel silver catalyst prepared by a method comprising the steps of:

1) impregnating the above-mentioned porous α-alumina carrier with a solution containing a sufficient amount of silver compound, organic amine, alkali metal additives and alkaline earth metal additives;

2) filtering off the impregnation solution, drying the impregnated carrier; and

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

Another aspect of the present invention relates to the application of the above-mentioned novel silver catalyst in the production of ethylene oxide by oxidizing ethylene.

In order to make the carrier have sufficient strength and good surface properties, the calcination temperature is preferably between 1250°C and 1550°C. If the temperature is too high, the activity and selectivity of the catalyst will be affected, and if the calcination temperature is too low, the strength of the carrier will be poor.

The addition of burnable carbonaceous materials is to create macropores, so that the carrier has a suitable pore structure and specific surface area. The carbonaceous material includes one or a mixture of petroleum coke, carbon powder, graphite, polyethylene, polypropylene, rosin and the like. The carbonaceous material is oxidized during the firing process, resulting in gas evolution and the formation of macropores in the support. According to the present invention, the particle size of the carbonaceous material is 20-300 mesh. The carbonaceous material is added in an amount greater than 0-6.6%, preferably 0.01-5%, of the total weight of the mixture.

The addition of flux is to make the carrier have good strength at low calcination temperature. Examples of fluxes include magnesium compounds such as one or a mixture of magnesium oxide, magnesium sulfate, magnesium nitrate and magnesium carbonate.

The fluoride mineralizer selected in the present invention includes hydrogen fluoride, ammonium fluoride, aluminum fluoride, magnesium fluoride, cryolite, etc. or their mixtures, and its function is to accelerate the crystal transformation of alumina and reduce the pores below 0.1 μm .

The heavy alkaline earth metal compound that the present invention adds comprises the oxide compound of strontium and/or barium, sulfate, acetate, nitrate and oxalate etc., and its effect is to improve carrier, and the addition is 0 of solid mixture gross weight ~5%, preferably 0.01-2.0%.

In the present invention, by adding binder, it forms aluminum sol with pseudomonohydrate _Al2O3 in the _mixture , binds each component together, and becomes extrudable paste. The binder used includes acid, such as nitric acid, formic acid, acetic acid, propionic acid and hydrochloric acid, etc., or replace the fake monohydrate Al ₂ O ₃ and acid with aluminum sol. When an acid is used as the binder, an aqueous solution of nitric acid is preferred, wherein the weight ratio of nitric acid to water is 1:1.25-10.

The obtained paste can be dried to less than 10% of water after being extruded, and the shape of the carrier can be ring, spherical, columnar or porous columnar. The drying temperature is 80-120°C, and the drying time is controlled within 1 hour to 24 hours according to the moisture content.

The dried paste is calcined at 1250-1550°C for 2-6 hours to convert almost all of the alumina, for example more than 90%, into α-Al ₂ O ₃ . The specific surface of the support is 0.2m ² /g-2.0m ² /g, preferably 0.5m ² /g-1.5m ² /g; the pore volume is 0.35-0.85ml/g, preferably 0.40-0.80ml/g; Water absorption ≥ 30%, preferably ≥ 35%; and crushing strength of 30N/grain to 120N/grain, preferably 35N/grain to 90N/grain.

The silver catalysts of the present invention can be prepared in a conventional manner, for example by impregnating the aforementioned alumina support with a solution containing a silver compound, an organic amine, an alkali metal promoter and an alkaline earth metal promoter.

In the preparation of the silver catalyst of the present invention, firstly, the aqueous solution of silver nitrate is reacted with ammonium oxalate or oxalic acid aqueous solution, and the silver oxalate precipitate is precipitated. Add additives to the aqueous solution of amines such as pyridine, butylamine, ethylenediamine, 1,3-propylenediamine, ethanolamine or their mixtures to form an impregnation solution. Then use the obtained impregnating solution to impregnate the above-mentioned alumina carrier for 30 minutes under the condition that the vacuum degree is less than 10mmHg, drain it, and place it in an air stream or a nitrogen-oxygen mixture with an oxygen content of not more than 21% (such as 8.0% oxygen) at 180 ~ The temperature range of 700°C, preferably 200-500°C, is maintained for 1 minute to 120 minutes, preferably 2 minutes to 60 minutes, for thermal decomposition. Silver oxide can also be used instead of silver nitrate, and silver oxalate can also be directly complexed with organic amine without diafiltration, and then impregnated with the carrier. The amount of silver compound used in the impregnation process of the present invention should be sufficient to make the final prepared catalyst contain 1-30% by weight of silver, preferably 5-25% by weight, based on the total weight of the catalyst.

The alkali metal additive in the present invention can be a compound of lithium, sodium, potassium, rubidium or cesium or a combination of any two thereof, and the content of the alkali metal in the final catalyst is 5-2000ppm, preferably 10-1500ppm. The alkali metal promoter can be applied to the support before, simultaneously with or after impregnating the silver, and can also be impregnated on the support after the silver compound has been reduced.

The alkaline earth metal additive in the present invention can be a compound of magnesium, calcium, strontium or barium, such as oxide, oxalate, sulfate, acetate or nitrate, or a mixture thereof, preferably a compound of barium or strontium. The total content of alkaline earth metals in the final catalyst is 5 ppm to 22000 ppm, preferably 10 ppm to 15000 ppm. The alkaline earth metal additives can be applied to the support before, simultaneously with or after impregnating the silver, and can also be impregnated on the support after the silver compound has been reduced.

In addition to the above-mentioned alkali metal additives and alkaline earth metal additives, other additives such as rhenium compounds and their co-auxiliaries, such as ammonium perrhenate and its co-auxiliaries chromium, molybdenum, tungsten, boron, etc., can be added to further The activity, selectivity, and stability of activity and selectivity of the resulting silver catalyst are improved. These other auxiliaries can be applied to the support before, simultaneously with, or after impregnating the silver, or after the silver compound has been reduced.

Determination of Catalyst Performance

Various silver catalysts of the present invention are tested for their initial performance and stability with a laboratory reactor (hereinafter referred to as "micro-reactor") evaluation device. The reactor used in the micro-reflection evaluation device is a stainless steel tube with an inner diameter of 4 mm, and the reactor is placed in a heating jacket. The packing volume of the catalyst is 1ml, and there is an inert filler at the lower part, so that the catalyst bed is located in the constant temperature zone of the heating mantle.

Determination of initial activity and selectivity

The assay conditions of activity and selectivity used in the present invention are as follows:

Reaction gas composition (mol%)

Ethylene (C ₂ H ₄ ) 28.0±1.0

Oxygen (O ₂ ) 7.4±0.2

Carbon dioxide (CO ₂ ) ＜8.0

Stable gas (N ₂ ) margin

Inhibitor Dichloroethane 0.1ppm～2.0ppm

Reaction pressure 2.1MPa

Airspeed 7000/h

EO concentration out of the reactor 1.35%

Space-time yield 185gEO/mlCat./h

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

Among them, ΔEO is the difference between the ethylene oxide concentration of the outlet gas and the inlet gas, and the average of more than 10 sets of test data is taken as the test result of the day.

Compared with the prior art, the present invention has the following advantages: the porous alumina carrier manufactured according to the present invention is not affected by the quality of the pore-forming agent, and the performance of the silver catalyst made from it is stable and has high activity, and is especially suitable for ethylene oxidation The reaction to produce ethylene oxide.

Example

The present invention will be further described below in conjunction with examples, but the scope of the present invention is not limited to these examples.

Preparation of Carrier Comparative Examples 1 and 2

Put 50-500 mesh α-Al ₂ O ₃ 312g, fake monohydrate Al ₂ O ₃ 92g larger than 200 mesh, petroleum coke 0 and 81g, NH ₄ F 7g and Mg(NO ₃ ) ₂ 8.5g into Mix evenly in a mixer, transfer to a kneader, add 0.12 liters of dilute nitric acid (nitric acid: water=1:3, weight ratio), and knead into a paste that can be extruded. Extrude into a five-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and dry it at 80-120°C for more than 2 hours to reduce the free water content to below 10%.

The preparation of carrier embodiment 1-3

50-500 mesh α-Al ₂ O ₃ 312g, fake monohydrate Al ₂ O ₃ 92g larger than 200 mesh, petroleum coke 5, 11 and 21g, NH ₄ F 7g and Mg(NO ₃ ) ₂ 8.5g Put it into a mixer and mix evenly, transfer it to a kneader, add 0.12 liters of dilute nitric acid (nitric acid: water=1:3, weight ratio), and knead it into a paste that can be extruded. Extrude into a five-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and dry it at 80-120°C for more than 2 hours to reduce the free water content to below 10%.

Preparation of Carrier Comparative Example 3

212g of α-Al ₂ O ₃ trihydrate of 50-500 mesh, 192g of false monohydrate Al ₂ O ₃ larger than 200 mesh, 81g of petroleum coke, 4g of finely ground barium sulfate, 7g of NH ₄ F and 8.5 g of Mg(NO ₃ ) ₂ g is put into a mixer and mixed evenly, then transferred to a kneader, and 0.12 liters of dilute nitric acid (nitric acid: water=1:3, weight ratio) was added, and kneaded into a paste that could be extruded. Extrude into a five-hole column with an outer diameter of 8.0mm, a length of 6.0mm, and an inner diameter of 1.0mm, and dry it at 80-120°C for more than 2 hours to reduce the free water content to below 10%.

Preparation of carrier embodiment 4

The difference from Comparative Example 3 is that the amount of petroleum coke added in the batching is 21g, and then mixed, kneaded, extruded, and dried to reduce the free water content to below 10%.

Put the above nine five-hole columns into a bell kiln, raise the temperature from room temperature to 1350°C to 1550°C in about 30 hours, and keep the temperature constant for 2 hours to obtain a white α-Al ₂ O ₃ carrier sample.

The measured carrier performance data are listed in Table 1.

The physical property data of table 1 comparative example 1 and embodiment 1～5

Comparative example 1 Comparative example 2 Example 1 Example 2 Example 3 Comparative example 3 Example 4 Crushing strength (N/grain) 84 34 79 71 63 42 55 Water Absorption (%) 47 70 50 54 58 74 73 Bulk specific gravity (g/cm³) 0.64 0.52 0.63 0.62 0.60 0.49 0.54 Specific surface (m²/gram) 0.91 0.90 0.88 0.84 0.72 0.78 1.05 Pore volume (ml/g) 0.58 0.64 0.60 0.61 0.61 0.65 0.62 Pore radius distribution (% of total pore volume) < 1 micron 1-5 microns 5-10 microns 10-30 microns 30-50 microns > 50 microns 6.274.59.07.50.82.0 4.653.711.717.84.97.3 5.472.110.28.51.02.8 5.871.69.89.12.31.4 8.268.59.69.41.92.4 5.656.210.816.25.85.4 6.960.710.614.83.13.9

The preparation of catalyst comparative example 1～3 and embodiment 1～4

Take 700g of silver nitrate and dissolve it in 750ml of deionized water. Take 325g of ammonium oxalate and dissolve it in 250ml of deionized water at 50°C. The two solutions were mixed under vigorous stirring, resulting in a white precipitate of silver oxalate. Aging for more than 30 minutes, filtering, and washing the precipitate with deionized water until there is no nitrate ion. The filter cake contains about 60% silver and about 15% water.

Add 300 g of ethylenediamine, 110 g of ethanolamine, and 375 g of deionized water in a stirred glass flask. Slowly add the prepared silver oxalate paste into the mixed solution under stirring, keep the temperature below 40° C. to completely dissolve the silver oxalate. The amount of silver oxalate added makes the prepared dipping solution silver-containing 22% (weight). Add 2.2 g of cesium sulfate, 1.4 g of strontium acetate, and deionized water to make the total mass of the solution reach 2000 g, and prepare a solution for use.

Take 100 g of the carrier samples prepared in Comparative Examples 1-3 and Examples 1-4 and put them into a vacuumable container. Vacuum to above 10mmHg, put in the above impregnation solution, immerse the carrier, and keep it for 30 minutes. Drain off excess solution. The impregnated support was heated in the air flow at 450°C for 5 minutes, and then cooled to make an ethylene oxide silver catalyst.

The silver and additive content of the prepared catalyst were analyzed, wherein the content was calculated as metal; the activity and selectivity of the catalyst sample were measured under the aforementioned process conditions using a microreactor evaluation device, and the test results are listed in Table 2.

The test result of the sample of table 2 catalyst preparation comparative example 1～3 and embodiment 1～4

sample name Silver content (%) Cesium content (ppm) Strontium content (ppm) Reaction temperature (°C) EO(%) Selectivity (%) Comparative Example 1 13.8 538 218 216 1.35 83.9 Comparative example 2 16.9 645 252 223 1.35 83.6 Example 1 14.2 542 223 218 1.35 84.2 Example 2 14.4 550 222 217 1.35 84.5 Example 3 15.2 564 229 218 1.35 84.1 Comparative example 3 17.0 654 255 225 1.34 83.8 Example 4 15.4 586 231 218 1.35 84.5

The preparation of catalyst comparative example 4 and embodiment 5

Add 300 g of ethylenediamine, 110 g of ethanolamine, and 375 g of deionized water in a stirred glass flask. Slowly add the silver oxalate paste prepared in Catalyst Comparative Examples 1 to 3 and Examples 1 to 4 under stirring, and keep the temperature below 40°C to completely dissolve the silver oxalate. The amount of silver oxalate added is The obtained dipping solution contained 22% silver by weight. Add 2.2g of cesium sulfate, 2.6g of barium acetate, 0.3g of lithium sulfate, and deionized water to make the total mass of the solution reach 2000g, and prepare a solution for use.

Take 100 g of carrier samples prepared in carrier comparative example 2 and embodiment 3 and put them into a vacuumable container. Vacuum to above 10mmHg, put in the above immersion solution, immerse the carrier, and keep it for 30 minutes. Drain off excess solution. The impregnated carrier was heated in an air flow at 350°C for 10 minutes, and then cooled to make an ethylene oxide silver catalyst.

The silver and additive content of the prepared catalyst were analyzed, wherein the content was calculated as metal; the activity and selectivity of the catalyst sample were measured under the aforementioned process conditions using a microreactor evaluation device, and the test results are listed in Table 3.

The test result of the sample of table 3 catalyst preparation comparative example 4 and embodiment 5

sample name Silver content (%) Cesium content (ppm) Lithium content (ppm) Barium content (ppm) Reaction temperature (°C) EO(%) Selectivity (%) Comparative example 4 17.2 650 15 417 222 1.35 83.5 Example 5 15.2 583 13 347 217 1.35 84.0

Claims (27)

1. a method for preparing the porous alpha-alumina supports that is used for ethene oxidation production oxirane usefulness silver catalyst comprises the steps:

I) preparation has the mixture of following composition:

A) based on the solid mixture gross weight be 50 orders～500 orders, the three water α-Al of 5～90% weight ₂O ₃

B) be that the granularity of 5～70% weight is greater than the false water α-Al of 200 purposes based on the solid mixture gross weight ₂O ₃

C) but be to after-flame carbonaceous material greater than 0 based on the solid mixture gross weight less than 5% weight;

D) based on the solid mixture gross weight be the flux of 0.01～3.0% weight;

E) based on the solid mixture gross weight be the fluoride-mineralization agent of 0.01～3.0% weight;

F) based on the solid mixture gross weight be the heavy alkaline earth metal compounds of 0～5.0% weight;

G) be the binding agent of 25～60% weight based on component gross weight a)-f); And

H) an amount of water;

II) with I) in the mixture that obtains mediate evenly and extrusion molding; With

III) product that obtains dry II), at high temperature roasting becomes α-Al then ₂O ₃

2. the method for claim 1, wherein said flux is the magnesium compound that is selected from magnesia, magnesium sulfate, magnesium nitrate, magnesium carbonate and composition thereof; Described carbonaceous material is petroleum coke, carbon dust, graphite, rosin, polyethylene, polypropylene or its mixture; Described fluoride-mineralization agent is one or more the mixture in hydrogen fluoride, aluminum fluoride, ammonium fluoride, magnesium fluoride, the ice crystal.

3. method as claimed in claim 2, the consumption that it is characterized in that described carbonaceous material is 0.01～5% of a described mixture total weight amount.

4. method as claimed in claim 2, the granularity that it is characterized in that described carbonaceous material is 20～300 orders.

5. the method for claim 1, wherein said binding agent are acid.

6. method as claimed in claim 5 wherein replaces an acid and a false water α-Al with aluminium colloidal sol ₂O ₃

7. method as claimed in claim 5, wherein said acid are aqueous solution of nitric acid, and wherein the weight ratio of nitric acid and water is 1: 1.25～10.

8. the method for claim 1 is characterized in that described heavy alkaline earth metal compounds is the oxide of strontium and/or barium, nitrate, acetate, oxalates or sulfate.

9. the product roasting under 1250 ℃～1550 ℃ high temperature that obtains the method for claim 1, wherein said III).

10. porous alumina carrier that obtains as each described method among the claim 1-9, it is characterized in that described porous alumina carrier has following feature: specific surface is 0.2m ²/ g～2.0m ²/ g; Pore volume is 0.35～0.85ml/g; Water absorption rate 〉=30%; And crushing strength is 30N/ grain～120N/ grain.

11. porous alumina carrier as claimed in claim 10, it is characterized in that described porous alumina carrier has following feature: specific surface is 0.5m ²/ g～1.5m ²/ g; Pore volume is 0.40～0.80ml/g; Water absorption rate 〉=35%; And crushing strength is 35N/ grain～90N/ grain.

12. porous alumina carrier as claimed in claim 10, the amount of wherein said heavy alkaline earth metal compound is counted 0.01～2.0% of described mixture total weight amount with heavy alkaline-earth metal.

13. as each described porous alumina carrier, wherein α-Al among the claim 10-12 ₂O ₃Content is more than 90%.

14. produce the used silver catalyst of oxirane by the ethene oxidation for one kind, by the method preparation that may further comprise the steps:

1) uses the porous alpha-alumina supports of the solution impregnation of the silver compound, organic amine, alkali metal promoter and the base earth metal promoter that contain q.s according to the described method preparation of claim 1;

2) elimination maceration extract, dry impregnated carrier; With

3) in containing oxygen gas mixture to step 2) the gained carrier activates, and makes described silver catalyst.

15. silver catalyst as claimed in claim 14, wherein silver compound be silver oxide, silver nitrate or silver oxalate and its addition should to make the content of silver in described silver catalyst be 1%～30%, based on the gross weight of described silver catalyst.

16. silver catalyst as claimed in claim 15, wherein should to make the content of silver in described silver catalyst be 5%～25% to the addition of silver compound, based on the gross weight of described silver catalyst.

17. silver catalyst as claimed in claim 14, wherein said alkali metal promoter is compound or its any two kinds combination of lithium, sodium, potassium, rubidium or caesium, and it is 5ppm～2000ppm that its addition should make the content of described alkali metal in described silver catalyst, based on the gross weight of described silver catalyst.

18. it is 10ppm～1500ppm that silver catalyst as claimed in claim 17, the addition of wherein said alkali metal promoter should make the content of described alkali metal in described silver catalyst, based on the gross weight of described silver catalyst.

19. as claim 17 or 18 described silver catalysts, wherein said alkali metal is the combination of caesium or caesium and lithium.

20. silver catalyst as claimed in claim 14, wherein said base earth metal promoter be the compound of magnesium, calcium, strontium or barium or its mixture and its addition should to make the total content of alkaline-earth metal in described silver catalyst be 5ppm～22000ppm, based on the gross weight of described silver catalyst.

21. it is 10ppm～15000ppm that silver catalyst as claimed in claim 20, the addition of wherein said base earth metal promoter should make the total content of alkaline-earth metal in described silver catalyst, based on the gross weight of described silver catalyst.

22. as claim 20 or 21 described silver catalysts, wherein said alkaline-earth metal is barium or strontium.

23. silver catalyst as claimed in claim 14, wherein said auxiliary agent before dipping silver, simultaneously or be applied on the carrier afterwards, or after silver compound is reduced, be immersed on the carrier.

24. silver catalyst as claimed in claim 14, wherein said activation process are to carry out in air or oxygen content are not more than 21% nitrogen oxygen atmosphere.

25. silver catalyst as claimed in claim 14, the temperature of wherein said activation process are controlled between 180 ℃～700 ℃ and the time of described activation process is 1 minute～120 minutes.

26. silver catalyst as claimed in claim 25, the temperature of wherein said activation process are controlled between 200 ℃～500 ℃ and the time of described activation process is 2 minutes～60 minutes.

27. a method of producing oxirane by the ethene oxidation is wherein used as each described silver catalyst in the claim 14～26.