JPS581629B2 - Ethylene oxide sagebrush - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silver catalyst for the production of ethylene oxide comprising silver supported on a porous refractory support.

The invention also relates to processes for making these catalysts and for producing ethylene oxide in the presence of these catalysts.

A substance consisting of silver supported on a carrier is known as a useful catalyst for producing ethylene oxide through controlled incomplete oxidation of ethylene with molecular oxygen.

A number of improvements have been proposed to improve the activity and selectivity of these catalysts.

These modifications include, for example, the carrier used, the method of manufacture, the physical form of the silver on the carrier, and the addition of additives to the catalyst.

Alkali metals and their salts have repeatedly been proposed as additives for various silver catalysts for the production of ethylene oxide.

U.S. Pat. No. 212, an early publication on the subject.
No. 5,333 discloses the inclusion of "small amounts" of alkali metals (including both sodium or potassium) in the silver catalyst.

Subsequent patents modified this invention, but often contained teachings that contradicted it.

For example, US Pat. No. 2,238,474 discloses that when 1000 ppm by weight of potassium or cesium hydroxide is added to 24% by weight of a silver catalyst enriched with sodium,
They teach that this amount had a detrimental effect on the performance of the catalyst.

A number of accelerators useful over a wide weight range are disclosed in U.S. Pat.
No. 5900, no differentiation in the effectiveness of the various promoters is shown.

The use of large amounts of alkali metal sulfates is described in US Pat. No. 2,671,764.

Further, U.S. Pat. No. 2,765,283 discloses that adding an inorganic chlorine compound (e.g., sodium chloride) in a weight ratio of 1 to 2000 ppm to the catalyst support before adding silver improves the performance of the resulting catalyst. There is.

However, U.S. Pat. No. 2,799,687 discloses that when 20 ppm to 1.6% by weight of an inorganic halide (sodium chloride or preferably potassium chloride) is added as separate solid particles to a fluidized bed of supported silver catalyst, the halide is It is disclosed that it acts as an inhibitor to inhibit catalyst activity.

U.S. Pat. No. 3,144,416 covers a large number of promoter materials, but does not impose critical limits on their concentrations.

The use of alkali metals and alkaline earth metals as cocatalysts is generally disclosed in US Pat. No. 3,563,913, with particular reference to lithium, but no mention of cesium, rubidium or potassium.

These promoters are preferably added to the catalyst support before it is impregnated with a solution containing a silver compound.

pore volume within the range of 0.15-0.30 m2/g and 10 m
The use of aluminum oxide supports with a surface area of 2/g or less is described in US Pat. No. 3,575,888.

The use of certain organic amine solubilizing/reducing agents to obtain uniformly spaced, closely spaced hemispherical deposits on a catalyst support is disclosed in U.S. Pat. No. 3,702,259. There is.

According to Dutch Patent Application No. 7300162, one or more alkali metals, namely potassium, rubidium and/or cesium, are added per kg of catalyst to 0.35 to 3.0 milligram atoms of alkali metal (mgat).
Catalysts can be used in which these metals are co-deposited with silver on the catalyst support.

Adding potassium, lupidium and/or cesium in amounts outside the above ranges is not advantageous, and adding alkali before adding silver provides little or no advantage.

The prior art recognizes that the addition of alkali metal compounds changes the character of the silver catalyst for ethylene oxide, either for the better or for the worse.

It has been found that excellent ethylene oxide catalysts are obtained if potassium, rubidium or cesium is deposited in critical amounts proportional to the support surface area before the silver is deposited.

The present invention provides a silver catalyst in which silver and one or more alkali ratio compounds are supported on a porous refractory carrier, in which the above catalyst is used in the following process, i.e. (a) in the range of 0.03 to 10 m2/g. After carrying out either of the following steps (b) or (c), a porous refractory support having a surface area of After extraction, in the final catalyst, the alkali metal content is 1 to 9 equivalents per kg of total catalyst per square meter of supported surface area per gram of catalyst support [(■ew/kg
)/(m2/g)]; (b) the impregnated carrier of step (a) is at least partially dried; (c) the product of step (b) is contacting the dissolved silver compound or slurry of silver particles or the silver compound with a liquid phase containing a sufficient amount to deposit 1 to 25% by weight of silver, based on the total catalyst, on the support surface; ) The product of step (c) may be defined as relating to the above-mentioned silver catalyst prepared by a process comprising heat treatment to convert the silver compound to silver metal.

The catalyst of the present invention consists of a porous refractory support on which silver is deposited in an amount of 1 to 25% by weight based on the total catalyst on the outer and inner surfaces (pore surfaces) of the support, and a certain amount of potassium ions, lupidium, etc. ions and/or cesium ions.

Of the alkali metals lithium, sodium, potassium, rubidium and cesium, atomic numbers 19 to
The 55 alkali metals potassium, rubidium and cesium are suitable.

Unless otherwise specified, these three preferred metals will hereinafter be referred to as "higher alkali metals."

Excellent results are achieved using each of these three higher alkali metals.

Potassium offers cost advantages and cesium offers the greatest catalyst improvement.

Rubidium provides greater catalyst improvement than potassium.

Mixtures of higher alkali metals are also useful.

Higher alkali metals are present on the catalyst in their cationic form rather than as highly active free alkali metals.

Silver, on the other hand, is present as metallic silver on the product catalyst.

The amount of higher alkali metal (or metals) present on the catalyst surface is a critical function of surface area.

The amount of higher alkali metal according to the invention is directly proportional to the surface area of the support, the optimum content being 5 ± 4, preferably 5 ± 3 mg equivalent [(mgew/kg) per kg of total catalyst for each square meter of surface area per gram of catalyst support. /(m2/g))
] is the weight of

In other words, the value obtained by dividing the optimum higher alkali metal content by the surface area is approximately a constant value.

As the alkali metal content is increased from 0, the selectivity of the catalyst increases until a maximum value is reached, after which the selectivity decreases again at contents after reaching the maximum value.

In this specification, the content at which this maximum value of selectivity appears is referred to as the optimum alkali metal content.

Furthermore, since the approach to optimal selectivity is gradual rather than stepwise, alkali metal contents above and below the optimum also result in commercially meaningful improvements in catalyst selectivity; Amounts are also considered to be within the scope of the invention.

Therefore, the alkali metal content is preferably 2
It includes a content within the range of 5-175%, more preferably 25-150%, most preferably 50-150%.

Small variations are observed in the range of content of each of the higher alkali metals of the present invention at which optimum selectivity is obtained when the catalysts of the present invention are used to partially oxidize ethylene to ethylene oxide.

However, these small differences may be due to unmeasured experimental differences or other unknown variables, but these do not appear to be significant.

Although the optimum alkali metal content is directly proportional to the surface area of the catalyst support, not all surface area provides a commercially useful catalyst.

The catalyst surface which has been found to be critical to the present invention is within the range of 0.03 to 10 square meters per gram (m2/g).

It must be made clear that the amount of potassium, rubidium and/or cesium deposited is not necessarily the total amount of these metals present in the catalyst.

These are the amounts of these alkali metals that are present on the surface of the catalyst and are intentionally added to the catalyst before adding silver.

By using support materials containing naturally occurring alkali metals, or by adding a single alkali metal during the manufacture of the support, significant amounts of higher alkali metals (often up to 1% by weight) can be introduced into the porous support. The presence of potassium (usually potassium) is not unusual.

These amounts of higher alkali metals present in the support in non-flushable form do not appear to contribute to the improved performance of the catalysts of the invention and are ignored in the measurement of alkali metal concentration.

However, the amount of higher alkali metal present in the carrier in washable form must be taken into account in determining the amount of higher alkali metal deposited on the carrier.

In fact, another method of adding all or part of the desired amount of higher alkali metal is to add the higher alkali metal in reachable form into the support during manufacture of the support.

The catalyst of the present invention contains silver as silver metal in a weight ratio of 1 based on the total catalyst.
Contains ~25%.

Preferably the catalyst contains 2-20% silver by weight, most preferably 4-16% silver.

Although the use of silver in amounts greater than 25% by weight is not precluded, it is usually not economically interesting.

The silver must be deposited over the inner and outer surfaces of the catalyst support and must be evenly distributed over these surfaces.

The exact physical form of the silver on the carrier may vary;
It is not believed to be critical to the invention.

However, when the silver is present in the form of uniformly spaced, discontinuous, cohesive discrete particles with uniform diameters of less than 1 micron (10,000 Å), the controlled Very good results are obtained using surface alkali metal containing catalysts.

Best results are obtained using this type of catalyst when the silver particles have a diameter of 1000 to 10000 Å, with the most preferred catalysts containing silver particles having an average diameter in the range of 1500 to 7500 Å.

The support used in the catalyst of the present invention is selected from a number of conventional porous refractory catalyst supports or support materials that are necessarily inert in the presence of the ethylene oxide feedstock, product and reaction conditions.

The above-mentioned commonly used substances may be natural or synthetic, and preferably have a macroporous structure, that is, a surface area of 10 m2/
The structure is preferably 7 m2/g or less.

These support materials typically have an apparent porosity of greater than 20%.

A highly preferred support is of silicic and/or aluminous composition.

A particular list of suitable carriers are aluminum oxide (including the material sold under the trade name "alantum"), charcoal, pumice, magnesia, zirconia,
diatomaceous earth, Fuller's earth, silicon carbide, porous conglomerate rock containing silicon and/or silicon carbide, magnesia,
Selected clays, man-made and natural zeolites and ceramics.

Refractory supports particularly useful in the preparation of the catalysts of this invention consist of aluminous materials, particularly those containing alpha-alumina.

In the case of α-alumina containing supports, B. E. T. Preferably, the specific surface area measured by the method is in the range of 0.1 to 7 m2/g, and the apparent porosity as determined by conventional mercury or water adsorption techniques is in the range of 10 to 50% by volume.

B. Measuring specific surface area. E. T. Brunauer, S., Emmett P.H.
mmett, P. H. ) and Telle
r, E. ) article [Journal of the American Chemical Society (J. Am. Chem
．． Soc. ) Volume 60 (1938), 309-319
page].

Regardless of the nature of the support used, the catalyst is preferably formed into particles, pieces, pellets, pellets, rings, spheres, etc. of a size suitable for use in fixed bed equipment.

Conventional commercial fixed bed ethylene oxide reactors are typically about 2.5 to 5 cm in diameter and about 7 to 5 cm long, packed with catalyst.
Several 14m parallel enlarger tubes (encased in suitable shells)
It has the shape of

In the above reactor, the shape is circular, for example, 2.5 to 20 m in diameter.
It is preferable to use carriers shaped into m spheres, pellets, rings, tablets, etc.

The catalyst of the present invention is made by a technique in which the desired higher alkali metal is deposited on the surface of the catalyst support prior to depositing the silver.

Therefore, the present invention also provides that (a) a porous refractory support having a surface area within the range of 0.03 to 10 m2/g is treated with a solution of an alkali metal compound having an atomic number of 19 to 55, arbitrarily by the following process. After performing either step (B) or (C) and extraction with a solvent, the final catalyst contains an alkali metal content of 1 to 9 cm per 1 kg of total catalyst per 1 m2 of supported surface area per 1 g of catalyst carrier. Equivalent weight ((mgew/kg)/(m2
(b) the impregnated carrier of step (a) is at least partially dried; and (c) the product of step (b) is treated with the dissolved silver compound or contacting with a slurry of silver particles or a liquid phase containing a silver compound to deposit 1 to 25% by weight of silver, based on the total catalyst, on the surface of the support, and (d) heat-treating the product of step (c). The present invention relates to a method of making a silver catalyst comprising converting a silver compound to silver metal.

Since the amounts of higher alkali metal compounds and silver compounds deposited depend in part on the porosity and surface area of the catalyst support, the higher alkali metal compounds used in the impregnation solutions used in steps (a) and (c) above The exact concentrations of silver and silver compounds usually require some routine experimentation.

However, methods for varying the amounts of higher alkali metals and silver deposited are just as commonplace as analytically measuring the amounts of the substances actually present.

Another method is to deposit a higher alkali metal salt in an amount larger than that required by the above general production method, and then subject the obtained catalyst particles to either the above step (b) or step (d). This includes contacting with a suitable solvent such as anhydrous alkanol having 1 to 2 carbon atoms per molecule, methyl or ethyl acetate or tetrahydrofuran.

Higher alkali metals are soluble in the above solvents, and when washed with these solvents once or twice, excess higher alkali metals are removed, and just the amount remaining on the surface of the carrier is critical for the present invention. It is soluble to a sufficient extent that it is within a range of suitable concentrations.

This method therefore reduces the concentration of higher alkali metals to 9 (■ew/kg)/(m
2/g) to a level in excess of 1 to 9 (mge
w/kg)/(m2/g) by a method that can be easily applied to the operation of large plants.

An excellent method of adding the desired higher alkali metal is to dissolve the compound of the higher alkali metal in the aqueous phase in an amount adjusted to add the desired alkali metal to the final catalyst when the support comes into contact with it. It is.

Suitable higher alkali metal compounds include all compounds that are normally soluble in the aqueous phase.

Therefore, no particular effect is observed no matter which anion is used in the alkali metal compound.

For example, hydroxides, nitrates, nitrites, chlorides, iodides, bromates, bicarbonates, oxalates, acetates, tartrates,
Lactate or isoproboxide may also be used.

After impregnation with the higher alkali metal, the support is heated in any suitable manner, preferably by increasing the temperature to a value within the range of 100-200°C, for example over a period of 0.5-8, especially 0.5-4 hours. Drying can be carried out by increasing the temperature, preferably in stages, and introducing an inert gas onto the heated carrier.

Suitable inert gases are nitrogen, air, hydrogen, noble gases, carbon dioxide, methane and mixtures of these gases.

Drying can be carried out at atmospheric, subatmospheric and superatmospheric pressures.

Vacuum drying and freeze drying can also be suitably used.

A number of different methods of adding silver to a carrier are known.

In a typical method, the support is impregnated with an aqueous solution of silver nitrate, dried, and the silver can be reduced with hydrogen or hydrazine, as described in US Pat. No. 3,575,888.

In another technique, the support can be impregnated with an ammonia solution of silver oxalate or silver carbonate, and the silver metal can be formed by applying heat to decompose the salt.

Silver or may be added by the techniques disclosed in U.S. Pat. No. 3,702,259, in which the carrier is a silver salt and ammonia, vicinal alkanolamines and/or
Alternatively, it is impregnated with a special aqueous solution of a combination of picinal alkyl diamines, and then heat treated.

Other possible methods of adding silver are described in Japanese Patent Publication 1973.
impregnating the carrier with an ethanolamine-containing solution of silver salts, as disclosed in U.S. Pat. The silver can then be thermally decomposed, or silver can be added in the form of "tassels" of silver, as described in US Pat. No. 3,781,317.

In each of these techniques, silver is added to the carrier when the carrier is contacted with a liquid phase containing either a silver solution or a slurry of silver particles or a silver compound.

A particularly effective method of depositing silver is when the silver is added to the support from a basic solution, especially a nitrogen base-containing basic solution.

Examples of these nitrogenous bases are ammonia, alkylamines and alkanolamines.

In a particularly preferred variant, the addition of silver to the catalyst support is carried out by a technique such as that disclosed in US Pat. No. 3,702,259.

This preferred process involves impregnating an alumina support with an aqueous solution of some silver salt and then thermally reducing the silver salt.

The silver impregnation solution necessarily consists of (a) a silver salt of a carboxylic acid, (b) an organic amine alkaline solubilizing/reducing agent, and (c) any additional aqueous solvent needed to reach the desired silver level.

Suitable silver salts of carboxylic acids include silver carbonate and silver salts of monobasic and polybasic carboxylic acids and hydroxycarboxylic acids containing up to about 16 carbon atoms per molecule.

Silver carbonate and silver oxalate are particularly useful silver salts, with silver oxalate being the most preferred.

An organic amine solubilizing/reducing agent is present in the impregnating solution used in this process.

Suitable organic amine silver solubilizing/reducing agents include lower alkylene diamines having 1 to 5 carbon atoms per molecule;
-5 lower alkanolamines and lower alkylene diamines having 1 to 5 carbon atoms, and mixtures of ammonia and lower alkanolamines or lower alkylene diamines having 1 to 5 carbon atoms.

Four types of organic amine solubilizing/reducing agents are preferred.

They are as follows. (a) Vicinal alkylene diamines having 2 to 4 carbon atoms (b) (1) Vicinal alkanolamines having 2 to 4 carbon atoms and (2) Vicinal alkylene diamines having 2 to 4 carbon atoms (c) A mixture of vicinal alkylene diamimines having 2 to 4 carbon atoms and ammonia, and (d) A mixture of vicinal alkanolamines having 2 to 4 carbon atoms and ammonia. Preferred solubilization of these /The reducing agent is usually added in an amount within the range of 0.1 to 10 moles per mole of silver contained.

Highly preferred solubilizing/reducing agents are as follows.

(a) Ethylenediamine (b) Ethylenediamine in combination with ethanolamine (c) Ethylenediamine in combination with ammonia, and (d) Ethanolamine in combination with ammoniaEthylenediamine alone or in combination with ethanolamine is most preferred.

When ethylenediamine is used alone as a solubilizing/reducing agent, it is necessary to add the amine in amounts ranging from 0.1 to 5.0 moles of ethylenediamine per mole of silver.

When using ethylenediamine and ethanolamine together as solubilizing/reducing agents, use 0.1 to 3.0 moles of ethylenediamine per mole of silver and 0.1 to 2.0 moles of ethanolamine per mole of silver. is preferable.

When ethylenediamine or ethanolamine is used with ammonia, it is usually useful to add at least about 2 moles of ammonia per mole of silver, and most preferably from about 2 to about 10 moles of ammonia per mole of silver.

As already mentioned, the higher alkali metals of the present invention need to be present in limited amounts, and these amounts are a function of the surface area of the catalyst support.

These quantities control the addition of alkali metal to the support during the initial impregnation step, or remove excess alkali metal from the impregnated catalyst support either before or after the silver impregnation step. This is achieved by controlling the

The heat treatment in step (d) is from 100 to 500°C, preferably at 10°C.
The time necessary to decompose the silver salt and produce adherent particle deposits of metallic silver on the surface at a temperature in the range of 0 to 375°C, more preferably 125 to 325°C, typically 0.5°C.
It is best to do this for ~8 hours.

Low temperatures do not fully decompose the silver salt and must be avoided.

More than one temperature can be used.

Silver catalysts promoted with higher alkali metals have been found to be particularly selective catalysts for the direct oxidation of ethylene to ethylene oxide using molecular oxygen.

Conditions for carrying out the above oxidation reaction in the presence of the silver catalyst of the present invention include conditions widely reported in the art.

This includes, for example, suitable temperatures, pressures, residence times, nitrogen,
The presence or absence of carbon dioxide, diluents such as water vapor, argon, methane or other saturated hydrocarbons, moderating agents that control catalytic activity, such as 1,2-dichloroethane, vinyl chloride or chlorinated polyphenyl compounds, and the presence or absence of recirculation operations. The intention is to increase the yield of ethylene oxide by continuous conversion or in a separate reactor, and any other special conditions that may be selected in other ethylene oxide production processes.

Pressures in the range of about 1 atmosphere to about 35 bar (absolute) are typically used.

However, higher pressures may be used within the scope of the invention.

The preferred oxygen source is relatively pure oxygen, mostly oxygen;
It necessarily consists of a rich oxygen stream or another oxygen-containing stream such as air, containing small amounts of one or more diluents such as nitrogen, argon, etc.

The use of the novel silver catalyst of the present invention in the ethylene oxidation reaction is by no means limited to the use of specific conditions among those known to be effective.

Preferred uses of the silver catalyst of ethylene oxide of the present invention include:
Oxygen containing not less than 95% oxygen gas in the presence of the catalyst of the invention at 210-285°C, preferably at 225°C.
Contact with ethylene is carried out at a temperature in the range of ~270°C.

The resulting ethylene oxide is separated and recovered from the reaction product by conventional methods known and used in the art.

Use of the silver catalyst of the present invention in an ethylene oxide production process provides a higher degree of overall ethylene oxidation selectivity to ethylene oxide for a given ethylene conversion than is obtained using conventional catalysts.

Although the reasons for these higher selectivities observed using the catalysts of the present invention are not completely understood, experiments have shown that conventional silver catalysts (free of higher alkali metals) However, the higher alkali metal-containing silver catalyst of the present invention does not cause further combustion of ethylene oxide.

Next, the following examples will be shown to explain the present invention in more detail.

Column ■ A series of catalysts were prepared using alumina supports with different surface areas.

The physical properties of these carriers are shown in Table 1.

Catalysts A-1, A-2...B-1 etc. were prepared according to the invention, ie by sequentially depositing alkali metal and silver.

Catalysts NA-0, NB-0, . . . NI-0, etc. were not based on the present invention in that they did not contain an alkali metal.

Catalysts NA-1, NA-2...NB-1, etc. were also not based on the present invention in that they deposited alkali metal and silver at the same time.

To illustrate the preparation of the catalyst according to the invention, the preparation of the catalyst using support C is shown below.

Other inventive catalysts were prepared in a similar manner.

30 g of carrier C with a surface area of 1.07 m2/g was first placed in a rotary evaporator to form an aqueous solution containing 3 cm of cesium hydroxide per ml of solution. 5 ml with a pressure of 0.04 bar (absolute)
Impregnation treatment was carried out under

The impregnated support was dried by heating at 110° C. for 30 minutes and then at 150° C. for 2 hours in a nitrogen stream.

The carrier was then impregnated with an aqueous solution of silver salt.

This solution was prepared by the following technique.

That is, 6 g of anhydrous silver nitrate and potassium oxalate (K2C20
4./H20) was separately dissolved in 100 ml of water.

The resulting solutions were mixed and heated on a steam bath.

The silver oxalate precipitate was centrifuged and the liquid present on the surface was decanted.

The precipitate was then dissolved in 100 ml of hot (60-90°C) distilled water.
Washed twice.

The precipitate was centrifuged and the water was decanted after each wash.

Next, the precipitate was mixed with 75% by volume of 1,2-diaminoethane and 25% of water.
A mixture consisting of 10% by volume and cooled in ice
ml.

30 g of the cesium-containing support are then placed in a rotary evaporator and impregnated with 8.5 ml of the latter liquid under a pressure of 0.04 bar (absolute), while being rotated by indirect heat exchange with boiling water. Warm again to a temperature of 60°C at 0.04 bar (absolute) to partially remove the solvent, pour out onto a large filter paper, shake gently to remove excess moisture and heat to a temperature of 300°C in a stream of nitrogen. Heat for 2 hours until
It was kept at 0°C for 2 hours.

The catalyst was then cooled to ambient temperature. The cesium content amounted to 3.35 mgew/kg of catalyst.

As a result of examining the catalyst with an electron microscope, the silver content was 0.05 to 0.3.
It was found that they were deposited on the support as discrete particles with uniform diameters of microns (500-3000 Å).

The silver particles were evenly spaced on the support surface.

NA-0…………NI that does not contain any alkali metals
To make the -0 series of catalysts, the initial impregnation step with the cesium hydroxide solution described above was omitted, but the subsequent steps were generally similar.

NA-1, NA-2, ......NB not based on the present invention
To make the -5 series of catalysts, the first impregnation step with cesium hydroxide described above was also omitted.

Subsequent steps followed a similar procedure except that cesium hydroxide was added to the silver-ethylenediamine-water solution in an amount sufficient to provide the desired alkali metal content in the final catalyst product.

The catalyst prepared as described above was tested comparatively for the production of ethylene oxide.

The reactor consisted of a tube with an internal diameter of 5 mm, and in each experiment the size was 0.
．． A length of 12 cm was filled with catalyst particles ranging from 4 to 0.8 m.

These catalyst particles were obtained by pulverizing the catalyst particles produced as described above.

A mixture containing oxygen and ethylene was passed over the catalyst in the presence of a small amount of vinyl chloride as a softening agent under the following conditions.

Pressure 14.5 bar (absolute)
Space velocity 3300h-1 Ethylene in raw material 30 mol% Oxygen in raw material 8.5 mol% Nitrogen in raw material
61.5 mol% relaxant concentration, raw material 10
10 ppm by volume of vinyl chloride per 0,000 parts The reaction temperature was adjusted so that 52% oxygen conversion occurred;
Selectivity to ethylene oxide was determined.

The selectivity to ethylene oxide expressed as a percentage is 1
00 moles of converted ethylene is also defined as the number of moles of ethylene oxide formed.

The results of the above experiments are shown in Tables 2 to 6.

As can be seen from these tables, at the smallest carrier surface area used, the sequential deposition method of the invention gives similar results to the simultaneous deposition method.

However, with the even more desirable high surface area supports, the approach of the present invention yields catalysts that are far superior to those made not in accordance with the present invention.

The above results are also reflected in the attached line in which the cesium content in ppm of the catalyst is plotted along the horizontal axis and the selectivity in terms of ethylene oxide is plotted along the vertical axis. Shown in the figure.

The selectivities of catalysts made from five different aluminas shown in Table 1 are shown in the diagram with five different symbols.

Five lines, each drawn based on a set of symbols, are
The selectivity is expressed as a function of the cesium content versus the surface area drawn near the respective line.

Surface area 0.19, 0.51, 1.07 and 1.32m
The four lines for 2/g are based on the left and lower scales, while the line for surface area 6.55 m2/g is based on the left and upper scales.

The vertical arrows pointing to each of the five curves indicate the optimal cesium content for each of the four catalysts.

These optimum cesium contents are shown in Table 7.

EXAMPLE ■ Using the raw materials and general manufacturing techniques of Example ■, catalysts of the invention containing various amounts of potassium as the higher alkali metal component were prepared.

Instead of adding cesium to the initial impregnation solution, potassium was added as potassium hydroxide.

The catalyst composition thus prepared was tested as an ethylene oxide catalyst using the equipment and procedure of Example 1.

The compositions and test results of these catalysts are shown in Table 8.

EXAMPLE ■ Using the raw materials and general manufacturing techniques of Example ■, catalysts of the invention containing various amounts of rubidium as the higher alkali metal component were prepared.

Instead of adding cesium hydroxide to the initial impregnation solution, rubidium was added as rubidium hydroxide.

The catalyst composition thus prepared was tested as an ethylene oxide catalyst using the equipment and procedure of Example 1.

The composition of the catalyst and the test results are shown in Table 9.

Example ■ Starting from supports B, C, D and E as listed in Table 1, Example I
A series of catalysts were prepared in the same manner as described, but using cesium nitrate instead of cesium hydroxide.

Catalysts A, F, K and P, which contain no cesium, are included in Table 10 for comparison.

The catalyst had the properties shown in Table 10.

The prepared catalyst was subjected to comparative tests for ethylene oxide production in a fixed bed.

The reactor consists of a tube with an inner diameter of 5 mm, with a maximum diameter of 0.4~
Length 16c with medium particles varying within a range of 0.8mm
It was filled to m.

A small amount of 1, with a mixture containing oxygen and ethylene as a relaxation agent.
It was introduced through the catalyst bed in the presence of 2-dichloroethane under the following conditions.

Pressure 14.5 bar (absolute) Space velocity 3000 h-1 Ethylene in feed 30 mol% Oxygen in feed 7.8 mol% Nitrogen in feed
62.2 mol% relaxant concentration, raw material 100
1.5 ppm by weight of chlorine per million parts The reaction temperature was adjusted so that 40% oxygen conversion occurred;
Selectivity to ethylene oxide was determined.

The values of S40 and T40 thus obtained are shown in Table 10 together with the number of test hours that have elapsed at the time of the measurement.

Catalysts containing various amounts of sodium, an alkali metal outside the scope of the present invention, were prepared using the raw materials and general manufacturing techniques of Example 2, which is not based on the present invention.

Instead of adding cesium hydroxide to the initial impregnation solution, sodium was added as sodium hydroxide.

The catalyst composition thus prepared was tested as an ethylene oxide catalyst using the equipment and procedure of Series 1.

The compositions and test results of these catalysts are shown in Table 11 below.

[Brief explanation of drawings]

The figure is a diagram showing the relationship between the selectivity and cesium content of the catalyst of the present invention-Example.

Claims (1)

[Scope of Claims] 1. A silver catalyst for producing ethylene oxide in which silver and one or more alkali compounds are supported on a porous refractory carrier, in which the above catalyst is used in the following steps, namely (a) 0.03~ After carrying out either of the following steps (b) or (c), a solution of an alkali metal compound having an atomic number of 19 to 55 is applied to a porous refractory carrier having a surface area within the range of 10 m2/g, and if necessary After extraction with a solvent depending on
/kg)/(m2/g)); (b) drying at least a portion of the impregnated carrier in step (a);
(c) a slurry of the product of step (b) and silver compound in solution or particles of silver or silver compound sufficient to deposit 1 to 25% by weight of silver, based on the total catalyst, on the surface of the support; The above-mentioned method is characterized in that it is produced by a method comprising contacting the silver compound with a liquid phase containing an amount of the silver compound and heat-treating the product of step (d) and (c) to convert the silver compound into silver metal. silver catalyst.