JPS6171837A - Catalyst and method for preparing ethylene oxide from ethylene - Google Patents

Abstract

PURPOSE:To enhance the selectivity of reaction, by supporting silver particles by the outer surface of a porous carrier and the inner surfaces of fine pores thereof while adjusting the average particle size of the silver particles on the inner surfaces of the fine pores to 0.05-0.4mum and specifying the silver support ratios thereof. CONSTITUTION:A porous carrier comprising a molded body of a refractory substance is impregnated with an aqueous solution containing a silver salt and amine being a complex forming agent and the impregnated carrier is contacted with overheated steam at 120-500oC to obtain a catalyst for preparing ethylene oxide wherein silver is distributed on the outer surface of the porous carrier and the inner surfaces of fine pores thereof. In the obtained catalyst, silver particles with a particle size of 0.05-0.4mum are distributed on the outer surface of the carrier and the inner surfaces of the fine pores thereof and the relation of I>=0.65S is present between the silver support ratio S of the outer surface of the catalyst and the silver support ratio I of the innermost layer part thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel silver catalyst for producing ethylene oxide by oxidizing ethylene with molecular oxygen and a method for producing the same.

Recently, as a method for preparing the silver catalyst used in the above reaction, a porous refractory carrier is soaked with an aqueous solution in which a silver salt is complexed with an amine containing ammonia, and then the silver catalyst is heated with air or the like and placed on the carrier. Methods of depositing silver are known. By using an amine, a silver salt that is decomposed and reduced at low temperatures can be made into a homogeneous aqueous solution as the amine complex, and for this reason, fine and uniform silver particles can be transferred to a porous carrier made of a molded body of a refractory material. It is said that it is possible to prepare an excellent catalyst by precipitating it on the surface. According to Japanese Patent Publication No. 55-22146, in order to precipitate silver from a silver salt-containing aqueous solution and use it as a catalyst, heating for 2 to 8 hours at 100 to 37 S°C is required, and air is used as the heating medium. ing. According to the present inventors, the heating method described above causes non-uniform distribution of the amount of silver supported within the catalyst particles, and furthermore, when the heating temperature and time described in the examples of the same publication are adopted, the aggregation and growth of the silver particles occur. was observed to occur. For example, 27 in the air
In a catalyst prepared by baking at 0°C for 2 hours and supporting 13% by weight of AQ on a carrier with a surface area of 0.4/9, most of the supported silver particles had a particle size of 0.4μ or more. It is confirmed that the silver particles are large and non-uniformly distributed in the catalyst particles. For this reason, sufficient catalytic performance cannot be obtained.

According to the present invention, the silver particles supported on the carrier are minute and uniform, and therefore have high activity as a catalyst, and furthermore, the amount of silver particles supported is extremely uniform from the outer surface layer to the inner layer of the catalyst. , the rate of aggregation of silver particles accompanying the reaction is slow;
A novel catalyst for producing ethylene oxide from ethylene with a long catalyst life and a method for producing the same are provided.

Furthermore, the catalyst of the present invention has a uniform distribution within the catalyst particles of the supported amounts of cationic components and anionic components, which have the effect of modifying silver, which is a reaction active species, and improving the selectivity of the reaction. The modification improves the selectivity of the ethylene oxide produced.

Furthermore, the production method of the present invention has the advantage that a catalyst having the above-mentioned characteristics that overcomes the drawbacks of the prior art can be produced particularly at low temperatures and in a short time.

The present invention will be explained in detail below.

According to the present invention, an aqueous solution containing a silver salt and an amine as a complexing agent is impregnated into a porous carrier made of a shaped body of a refractory material, and the carrier is heated with superheated steam to deposit silver onto the carrier. A catalyst for the production of ethylene oxide can be produced from ethylene having the above-mentioned characteristics and advantages by precipitating it.

In the production method of the present invention, the porous carrier impregnated with an aqueous solution containing a silver salt and an amine as a complex forming agent contains at least a part of the aqueous solution for 12
Preferably, silver is deposited on the support by contacting it with superheated steam at a temperature of 0° C. or higher. In particular, the porous carrier impregnated with an aqueous solution containing a silver salt and an amine as a complex forming agent has a drying rate (removal rate) of the aqueous medium in the aqueous solution of 0 to 70% by weight, preferably 0 to 70% by weight. Silver is precipitated on the carrier by contacting the porous carrier with superheated steam at a temperature of 120 to 500°C, preferably 120 to 300°C, particularly 150 to 260°C, in a state of 50% by weight. That is advantageous.

As the silver salt used in the above production method of the present invention, amine (
A silver salt that can decompose and precipitate silver at a temperature of 500°C or lower, preferably 300°C or lower, particularly preferably 260°C or lower, when it forms a soluble complex in an aqueous medium with ammonia (including ammonia). It can be anything. Examples of such silver salts include silver oxide, silver nitrate, and silver carboxylates such as silver carbonate, silver oxalate, and silver acetate, and silver carboxylates are particularly preferred.

The amine as a complex forming agent may be any amine that acts as a ligand to maintain the silver in solution, such as pyridine, acetonitrile, or secondary or secondary amines having 1 to 6 carbon atoms. Amines or ammonia are destroyed. Preferred amines include monoamines such as ammonia, pyridine and butylamine, alkanolamines such as ethanolamine, alkylene diamines having 2 to 4 carbon atoms, and polyamines, with diamines having 2 to 4 carbon atoms being particularly preferred, such as ethylene diamine, 1
, 3-propanediamine is preferred. Among these, the combination of ethylenediamine and 1,3-propanediamine is most preferred. Of course, combination use with other amines and addition of a trace amount of other compounds, such as dimethylformamide, are also effective.

The above silver salt and amine are preferably made into a uniform aqueous solution. In addition to water, a mixed solvent of water and a water-soluble organic solvent such as alcohol can also be used. This is impregnated into a porous refractory carrier.

Porous refractory carriers include α-alumina, silicon carbide, titania, zirconia, magnesia, etc., and in particular, those having a surface area of 0.01 to 27 FL'/i, preferably 0.2
~0.7 d/i with a pore volume of 0.2-0.5 ml/
I, an α-alumina support having an average pore diameter of 0.1 to 20 μm is preferred. Its shape is spherical, ring-shaped, cylindrical, etc.
It is a molded product of about ~15u.

Impregnation is carried out by methods known to those skilled in the art, and if necessary, under reduced pressure or
Use operations and equipment such as heating and rotary spraying. The silver concentration and weight of the impregnating solution are adjusted so that the amount of silver supported on the finished catalyst is 5 to 15 percent by weight. An amount of amine sufficient to complex the silver salt (usually 2 amine groups correspond to 1 mole of silver) is added (usually the amine is added in an excess of 10 to 30% rather than the equivalent amount).

In the production method of the present invention, a porous carrier made of a molded body of a refractory material is impregnated with an aqueous solution containing a silver salt as described above and an amine as a complex forming agent, and the carrier is heated with superheated steam to preferably 120% The precipitation of silver onto the support is substantially completed without heating to a temperature above .degree.

Therefore, JP-A-53-1191 discloses that a carrier is impregnated with an aqueous solution of a thermally decomposable silver complex compound, a sodium compound, and a heavy alkali metal compound to prevent water loss from occurring in the impregnated carrier. is treated with steam, especially saturated steam, until the silver compound starts to decompose, and then Co,
, N, or air, etc., at a temperature of 150 to 300°C until it reaches a constant weight. However, the production method of the present invention is different from such a method. They are clearly different.

In the present invention, for example, the precipitation reaction of silver from an impregnated aqueous solution in which silver oxalate is complexed with 1,3-propanediamine occurs at around 120°C, and the amount of heat required to complete the reaction is absorbed by superheated steam. Once supplied, the catalyst can be prepared by heating with superheated steam at that temperature.

Agglomeration of silver particles precipitated on a carrier occurs significantly when heated in air, especially at a high temperature of 200°C or higher, but when heated in superheated steam as in the present invention, aggregation of silver particles precipitated on a carrier is extremely likely to occur. It has the advantage of being effectively suppressed.

However, even in heating with superheated steam, the higher the temperature of the superheated steam is, for example, 260°C or higher, or the longer the heating time, the more agglomeration of silver particles tends to increase. It is preferable to control the conditions so that aggregation does not occur as much as possible.

The amount of silver supported on the catalyst carrier is advantageously 5 to 20% by weight, preferably 8 to 15% by weight of silver particles, based on the entire catalyst.

According to the method of the present invention, the typical diameter of silver particles deposited on a support (if not spherical, the shorter diameter) d(μ)
was found to be mainly influenced by the AQ loading rate and the carrier surface area. In the present invention, the preferred range is A(E) loading rate of 8 to 15 cm, carrier surface area of 0.2 to 0.6
rr? / I range, the relationship is: If the diameter of the silver particle is d (μ), then the supported amount of dαCArt]0″2[
It seems that it can be approximated by the formula: carrier surface area) - 1j.

Japanese Patent Publication No. 53-33565 discloses that α) impregnating inert support particles with a thermally decomposable silver salt, b) drying at a temperature not exceeding 160°C, and ") maintaining the temperature at 270 to 350°C. Discloses a method for preparing a catalyst by flowing superheated steam to a selected value, d) replacing the catalyst with air at the same temperature for at least 1 hour, and ') flowing heated air at the same temperature for at least 30 minutes. This method requires a very complicated and long heat treatment during catalyst preparation, and a good catalyst can only be obtained by this method.

Further, the publication does not describe the use of a silver salt complexed with an amine as a thermally decomposable silver salt. Therefore, from the viewpoint of the present inventors who use the amine complex salt, the method disclosed in the publication employs heat treatment at a high temperature and for a long time, which is undesirable. For example, while the preferred temperature range of the present invention is 150-260'C for a short time of about 115 minutes, the method of the publication uses 270-350'C.
'C, preferably 290 to 320'C, and a heated air treatment for at least 1.5 hours are required. When the amine complex of the silver salt used in the present invention is subjected to such a treatment, significant agglomeration of the precipitated silver particles and severe intra-particle non-uniform distribution are brought about. The former is used for high temperature air treatment, and the latter is used for the temperature of the impregnated carrier during water evaporation (I
00℃) and the superheated steam (
This book is thought to be mainly derived from the book "For this reason, water evaporates too rapidly".

Furthermore, the method disclosed in the same publication takes a sufficiently long time (I~10
Drying operation by dry heating (time) is essential before heat treatment with superheated steam, and the treatment method is completely different from heating with superheated steam with moisture remaining in the impregnated carrier as in the present invention. ing.

In the production method of the present invention, in addition to silver particles, (D) cation components (7)'-1) lithium, sodium, potassium, rubidium, and cesium ( alkali metal elements), (D
-2) It is preferable to support at least one element selected from the group consisting of calcium and barium (alkaline earth metal elements), and (D-a) thallium, tin, and antimony.

The cation component in (D) above is: 1) at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, or 11) at least one of the above i) A combination of an alkali metal element and barium is preferred.

As the cation component of group i) above, particularly preferred are sodium-cesium combination, sodium-potassium combination, sodium-rubidium combination, potassium-cesium combination, and lithium-cesium combination. As the group 11) above, a combination of the above two elements of group ;) further combined with barium, particularly a combination of sodium-cesium-barium, is preferable.

In addition, in the production method of the present invention, in addition to silver particles, (D) a cationic component (D-1) consisting of lithium, sodium, potassium, rubidium, and cesium is added to the porous carrier of the molded body of the refractory material. at least one alkali metal element selected from the group, (D-2) at least one alkaline earth metal element selected from calcium and barium, and (D-3) at least one of thallium, tin, and antimony. (E) at least one selected from the group consisting of fluorine, chlorine and bromine as an anion component;
It is more preferable to support the element s.

In order to support a cationic component on a porous carrier, it is generally desirable to add it in the form of a water-soluble compound, especially nitrate,
Common examples include halides, hydroxides, carbonates, bicarbonates, and carboxylates. Oxides can also be used. For example, lithium carbonate, sodium carbonate, sodium bicarbonate,
Examples include sodium acetate, potassium nitrate, cesium nitrate, cesium chloride, rubidium nitrate, barium nitrate, barium hydroxide, calcium hydroxide, calcium oxide, thallium chloride, tin bromide, and antimony chloride.

Appropriate amounts of each of the above compounds can be added simultaneously or separately to the impregnating liquid and supported on the porous carrier.

Alternatively, it is also possible to support these additives on the carrier before or after the silver, and these additives can be heated and supported by a known method, but when superheated steam is used, the cationic components are particularly absorbed in the catalyst particles. It is preferable in terms of performance that the distribution of

Addition of the anionic component can also be carried out in the same manner as the addition of the cationic component. The anionic component is generally preferably added in the form of a water-soluble compound, and the above cationic components are particularly preferably added, such as alkali metal elements such as lithium, sodium, potassium, rubidium, and cesium, and alkaline earth elements such as barium and calcium. Preferably, it is added in the form of a salt with the metal elements thallium, tin, and antimony. Ammonium salts can also be used. - Examples include lithium bromide, IJium chloride, potassium fluoride, cesium chloride, thallium chloride, and ammonium chloride.

An appropriate amount of the above compound can be added to the impregnating solution so that it can be supported on the porous carrier at the same time as silver.

Alternatively, it is also possible to support these additives on the carrier before or after the silver, and these additives can be heated and supported by a known method, but if superheated steam is used, the anionic components may be particularly absorbed in the catalyst particles. distribution becomes uniform, which is favorable in terms of performance.

According to the present invention, there is provided a catalyst in which at least silver particles are supported on a porous carrier made of a molded body of a refractory material, which is produced by the above-described production method, and (A) the silver is on the outer surface of the carrier. and distributed on the inner surface of the pores, and (B) the average diameter of the silver particles distributed on the inner surface of the pores of the carrier is within the range of 0.05 to 0.4 microns, preferably 0.1 micron. and <C> between the silver support rate (S) in the outer surface layer of the catalyst and the silver support rate (I) in the innermost layer of the enemy medium according to the following formula, I≧0.65.5. A catalyst for producing ethylene oxide from ethylene is obtained, which preferably satisfies I≧0.7S.

The average diameter of the silver particles distributed on the inner surface of the carrier pores in (E) above can be measured by scanning electron microscopy on a cross section of the catalyst particles.

In the present invention, for example, regarding silver particles clearly observed in a scanning electron micrograph (e.g., magnification t o, o o o times), about 30 large silver particles and about 30 small silver particles are selected. Read the diameter of the particle (or the shorter diameter if it is not spherical) and calculate the sum as the total number of particles (
60) (average).

The silver support rate (S) in the outer surface layer of the catalyst of the present invention defined in (C) above and the silver support rate (I) in the innermost layer of the catalyst are:
The catalyst of the present invention is gradually scraped away from the outer surface toward the inner layer, and the unit type f! It can be determined by quantifying the content (weight) of steel per c (for example, 1 gram, ).

In the present invention, the outer surface layer of a catalyst is defined as an average 5-fold layer distributed as uniformly as possible from the outer surface of the catalyst (carrier) toward the inner layer, assuming that the weight of one catalyst particle is 100 inches. (range of 4-6%) is shown. In addition, the innermost layer of the catalyst is about 60% by weight on average as uniformly as possible from the outer surface of the catalyst particles (carrier) toward the inner layer.
(Range of 50-70%, preferably 55-65%)
It means the inner layer (innermost layer) of the catalyst that remains after scraping off.

As a simple method for measuring S and I, for example, catalyst particles 30
Take ~50 catalyst particles (measure their total weight), rotate them in a rotating container, scrape off from the surface of each catalyst particle toward the inner layer, and calculate S as the average value of all catalyst particles according to the method described above. and I can be obtained.

The catalyst of the present invention has the following formula I≧0.655 between the silver support rate (S) in the outer surface layer of the catalyst and the silver support rate (I) in the innermost layer of the catalyst described above. More preferably, the relationship I≧0.7S is satisfied. In the above formula I≧0.655, it is preferable that I is larger than 0.655.

It is clear from this that in the catalyst of the present invention, silver particles are extremely uniformly supported from the surface layer of the catalyst particles to the innermost layer thereof.

Furthermore, as is clear from the average diameter of (B),
It is clear that in the catalyst of the present invention, the silver particles distributed on the inner surface of the pores of the catalyst carrier are hard, fine and uniform, and do not substantially contain large aggregates.

According to the present invention, the average diameter of the silver particles deposited on the carrier is preferably as small as 0.3μ or less, particularly 0.2μ or less, so that the activity as a catalyst is high, and furthermore, the distribution of silver particles within the catalyst particles is , typically I≧0.7S1 preferably I≧0
．． 7S5 is very uniform, and the rate of aggregation of silver particles during the reaction is slow, resulting in a long catalyst life. Moreover, in a preferred embodiment, a cation component and an anion component are used which have the effect of modifying silver, which is a reactive species, and improving the selectivity of the reaction.

Thus, according to the invention, highly preferred catalysts include:
In addition to supporting at least silver particles on a porous carrier made of a molded body of a refractory material, (D) as a cation component, (D-1) selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. At least one selected alkali metal element, (D-2) at least one alkaline earth metal element consisting of calcium and barium, and (D-3) at least one element selected from thallium, tin, and antimony. A catalyst on which is supported is obtained.

As the cationic component of (D) above, special K, i)
(D-1) At least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, or 11) At least one alkali metal element of the above CD-1) and (D -2) barium is preferred.

A more preferable catalyst of the present invention has at least silver particles supported on a porous carrier made of a molded body of a refractory material, and in addition, as a cationic component (D-1) lithium, sodium, potassium, At least one alkali metal element selected from the group consisting of rubidium and cesium, (D-2) at least one alkaline earth metal element of calcium and barium, and (D-3) thallium, tin, and antimony. (E) at least one element selected from the group consisting of fluorine, chlorine, and bromine as an anion component;
It carries seed elements.

The cation component is preferably one or more of lithium, sodium, and barium, and/or at least one of potassium, rubidium, and cesium.

In particular, a cation component is supported on the outer surface and the inner surface of the pores, and the supporting ratio of the alkali metal element as the cation component in the outer surface layer of the catalyst on the inner surface of the pores (
Sc) and the supporting ratio (Ic) of the alkali metal element as a cation component in the innermost layer of the catalyst on the inner surface of the pores, which satisfies the following formula, Ic≧0.3 S a , according to the present invention. is a preferred catalyst. The above-mentioned measurements of Sc and Ic can be performed by the same measuring method as the measurement of S and I regarding the distribution of silver particles in the catalyst described above.

In the catalyst of the present invention, when at least one cation component of lithium, sodium, and barium is supported on the outer surface of the carrier and the inner surface of the pores, the outer surface layer of the catalyst on the inner surface of the pores is The following formula 1 formula % is satisfied between the lithium and/or sodium loading rate (Sc) and the lithium and/or sodium loading rate (Ic) in the innermost layer of the catalyst on the inner surface of the pores, In addition, when at least one alkali metal element of potassium, rubidium, and cesium is supported on the outer surface and the inner surface of the pores, the alkali metal element in the outer surface layer of the catalyst on the inner surface of the pores. Element loading rate (
It is particularly advantageous that the following formula % is satisfied between Sc) and the supporting ratio (Ic) of the alkali metal element in the innermost layer of the catalyst on the inner surface of the pores.

The supported amount of the cation component is based on the entire catalyst: 1) 0.1 to 1% by weight in the case of sodium and lithium, 2) 0.1% by weight or less in the case of potassium, rubidium, cesium, and thallium. 3) In the case of barium, it is preferably 1% by weight or less, and the amount of anion component supported is preferably 0.05% by weight or less.

According to the present invention, as shown in FIG.
When the impregnated carrier is in a low temperature state, its temperature is rapidly raised and the entire carrier layer is heated uniformly. Normally, in the catalyst production method of the present invention, the evaporation of water and the precipitation of silver by decomposition of the silver complex occur during the heating process, but the superheated steam uniformly performs the evaporation of water and the precipitation of silver simultaneously or separately. This method is superior to the conventional method in that the silver particles deposited are fine as shown in Figure 2-A, and the silver and other additive components are uniform as shown in Figure 3. It has a distribution. The catalyst produced according to the invention therefore has the following characteristics:
It has high activity, excellent selectivity, and long life.

It is practical for the superheated steam used in the present invention to have a pressure near normal pressure in the industrial preparation method of the catalyst, and its temperature is preferably 120 to 500°C, particularly 120 to 300°C. Particularly preferably the temperature is 150 to 260°C. The heating time is preferably about 1 minute to 3 hours, and from a practical standpoint and the performance of the catalyst, the shorter the better, and usually about 3 hours.
minutes to 15 minutes is most preferred. Of course, the amount of impregnated carrier to be heated, the temperature of the steam and its flow rate will determine the minimum time required. Steam flow velocity is 0.3m/sec ~ 5m
/second is preferable from the performance and practical standpoints of the produced catalyst.

As a heating method using superheated steam in the present invention,
The impregnated support can be stacked in single or multilayer form in the form of a fixed bed or a moving bed and can be passed through superheated steam from above or below or from the side. Since superheated steam can heat the entire layer at a uniform temperature, there is no non-uniform distribution of iron between the layers, and multi-layer firing is economical from a practical standpoint. It is also possible to mix a certain amount of nitrogen, air, etc. into the superheated steam.

Additionally, the exit steam contains amines and other decomposition products produced by the decomposition of silver salts, and although a certain amount of purging may be necessary to prevent their accumulation, it is generally recommended that the superheated steam be recycled. It is possible and economical. For example, 90% recycling is possible, although it varies depending on the steam environment and the amount of impregnated carrier.

In the method of the present invention, a porous carrier impregnated with an aqueous solution containing a silver salt and an amine as a complexing agent or an aqueous solution of a cation and/or anion component therein is used to dry the aqueous medium in the aqueous solution. so that the removal rate (removal rate) is 0 to 70% by weight, preferably 0 to 50% by weight.
The impregnated carrier may be heated with superheated steam as it is or after draining off the excess impregnating liquid, or it may be dried at a temperature of 100° C. or lower, for example in circulating air, and then heated with superheated steam according to the method described above. Preferably, silver is deposited on a carrier.

The reaction of converting ethylene to ethylene oxide using the catalyst of the present invention can be carried out using conventional procedures.

For example, the pressure is 9/crl from 1 to 35, and the temperature is from 180 to 9/crl.
The temperature is 300°C, preferably 200-260°C.

Ethylene is 1-40Vo1%, oxygen is 1-20Vo1%
In general, a diluent such as methane is added in a certain proportion, for example 20~
It is preferable to make it exist at 1% of 10Vo. Oxygen may be supplied in the form of air or as industrial oxygen. By adding, for example, ethylene dichloride as a reaction modifier, the formation of hot spots in the catalyst can be prevented and the performance of the catalyst, particularly the selectivity, can be greatly improved. The amount added is preferably about several ppfrL (weight i) to several tens of pptn.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example I Nα, CO326.9fl was dissolved in 11 parts of water, and α-alumina carrier (8φ x 3φ x 8 ring shape. Surface area 0,5
m/l N pore volume 0.4 mg/P) Ilg
Soaked. After dripping off the excess liquid and cutting 14
It was dried with superheated steam at 0° C. for 15 minutes.

On the other hand, AQNO8248N and potassium oxalate (:KtCtO
*・Hρ)148. ? After dissolving each of 11 in water, they were mixed and heated to 60°C in a water bath to obtain a white precipitate of silver oxalate. After filtration, the precipitate was washed with distilled water to remove potassium in the precipitate. Separately, 1,3-pronochlorodiamine 21.
7 g of ethylenediamine and 79.11 g of ethylenediamine were dissolved in water to prepare an aqueous solution 200-, which was added little by little to the silver oxalate precipitate while cooling on ice to prepare a silver oxalate-amine complex solution. To this, barium nitrate 1.49#, cesium chloride 0.23
After mixing the aqueous solution 40- in which Ii was dissolved, it was transferred to a rotary evaporator, and the above-mentioned α-alumina carrier, which had been impregnated with Na and Ca9 and dried, was added thereto, and an impregnation operation was carried out at 50° C. under rotation. Reduce the pressure at the beginning of the impregnation operation101
00fiH, the pressure was returned to normal, and the sample was taken out after 5 minutes. The impregnated α-alumina carrier taken out was heated in superheated steam at 200° C. for 10 minutes at a flow rate of 2 m/sec to prepare the catalyst of the present invention. The loading rates of AQ, Nα, Bα, Cs and Ct are respectively 13.5 cm, 0.4 k, 6 TOY)7) m, 1
They were 58 ppm and 42 ppm. FIG. 1 (solid line) shows the heating curve at that time.

This heating curve shows that the impregnated carrier was rapidly heated by the superheated steam to the boiling temperature of water. It is thought that for this reason, water evaporates from the entire surface of the carrier, making it possible to obtain a uniform distribution of catalyst components. then 20
Evaporation of water and decomposition of the silver complex occur continuously until heating to 0°C. Figure 2-A is a scanning electron micrograph (10.000x magnification) of the prepared catalyst. Silver particles are precipitated in the form of uniform fine particles on the inner surface of the pores of the carrier.

The distribution of silver shown in Figure 2-A is maintained throughout the metal bodies within the catalyst particles, and the average diameter thereof is 0.15μ, and almost all the silver particles are in the range of 0.05 to 0.3μ. there were. The BET surface area of the catalyst was 0.95 m'/9. FIG. 3 (solid line) shows the distribution of silver support within the catalyst particles. Up to 6% by weight of A from the outer surface of the catalyst particles toward the inside
g, Ca, Nh catalyst support ratio, S, Sc8,
SNα is 15.0%, 177ppm, and 435, respectively.
0ppm, and 60% by weight from the outer surface to the inside.
Each loading rate in the above, I, IC8, INcL
are 110%, 134ppm, and 3500ppm, respectively.
I failed. Therefore, Iki 0.87S, Io, medium 0.76
5C1l”N (calculated as 0.835NcL in L,
It is shown that each component is uniformly distributed from the outer surface layer to the innermost layer of the catalyst particles.

The above catalyst was crushed into 4 to 9 meshes, and the 5 meshes were filled into a steel reaction tube with an inner diameter of 20 mesh, and the reaction gas (ethylene 30V1%
, oxygen 8Vo 1%, vinyl chloride 2ppm, balance 9 nitrogen)
was passed under a pressure of 18klI/crIG at 5V for 4000h. Activity is expressed immediately after passage begins. Bath temperature 21
After one week of reaction at 2°C, an oxygen conversion rate of 40% and an ethylene oxide selectivity of 81.7% were obtained. The BET surface area of the catalyst after reaction was 0.84 rl/i. In order to maintain an oxygen conversion rate of 40 cm during continuous operation for 1.5 months, the bath temperature was increased by 2°C, but there was no change in selectivity.

Examples 2-6 Catalysts were prepared in exactly the same manner as in Example 1, except that barium nitrate was not added. However, the temperature and passage time of the superheated steam during the final heating were changed. Conditions for treating these catalysts with superheated steam and I of each catalyst obtained
Table 1 shows the ratio of S and S, and the results when the reaction was carried out in the same manner as in Example 1. Note that A has 1. The supporting rates of Nα, Cs, and Cl are each 13.5'u) e %z O-4
1.158 pp''% was 42 ppm. 140 + 540 in the table indicates the bath temperature (°C) and selectivity (ch) when the oxygen conversion rate was 40%.

Table 1 740 of the catalyst of Example 2 after three months of continuous operation is 218°
G, 540 was 80.8%.

Examples 7-8 A silver-CsC1-containing catalyst was prepared in exactly the same manner as in Example 1, except that a carrier not carrying Na2CO3 was used and barium nitrate was not added. The respective loadings were determined to be 13.5 wt % and 200 ppm. However, two types of catalysts were created by changing the passage time of superheated steam during heating.

The reaction results are also shown in Table 2.

Table 2 Comparative Example 1 This Comparative Example 1 shows the differences between the catalyst of the present invention and the catalyst prepared by the short-time air heating method according to the invention of the present inventors, rather than by the conventionally known air heating method of the impregnated carrier. It is filled with things that make it clear.

Instead of performing the final heating with superheated steam at 200℃,
A catalyst was prepared in exactly the same manner as in Example 2, except that heated air at 200° C. was flowed at a flow rate of 2 m/sec for 10 minutes. The composition is also the same as in Example 2. The heating curve (control catalyst) is shown by the dashed line in FIG. As shown by the broken line in FIG. 1, compared to the case where superheated steam is used (solid line in FIG. 1), the temperature rise rate is slow in the early stage of heating, and constant rate drying progresses below the boiling temperature. In this state, drying mainly occurs on the outer surface of the carrier particles, so that the catalyst components are thought to migrate to the outer surface of the particles. Thereafter, decomposition of the silver salt complex proceeds.

FIG. 2-B and FIG. 2-C show scanning electron micrographs of the obtained catalyst. Figure 2-B shows the inner surface of the pore near the outer surface, and Figure 2-C shows the inner surface of the pore, and it is clear that the AQ particles are unevenly distributed within the catalyst particles.

Figure 3 (dashed line) shows the intraparticle distribution of A(J).S of AQ up to 6% by weight from the outer surface layer to the inside of the catalyst particle is 18.8%, and from the outer surface layer to the inside 60% by weight
The internal I was 12 inches and the I/S key was 0.64. From the above, it can be seen that AQ precipitated on the carrier is distributed non-uniformly in air firing compared to superheated steam firing.

When the reaction was carried out in the same manner as in Example 1 using the above catalyst (Comparative Example 1), T40=21 at the initial stage of the reaction.
7° CI 540 = 81.3%, but after three months of continuous operation, T2O was 227°C and S4o was 79.8%. It can be seen that compared to the catalyst of Example 2, the increase in temperature was large and the selectivity decreased significantly.

Comparative Example 2 For supporting Ha2Co on the carrier, the same temperature air was used instead of 140°C superheated steam, and for the final heating, 300°C heated air was used instead of 300°C superheated steam. A catalyst was prepared using the same method and composition as the catalyst of Example 6, except that the test was carried out for 2 hours. 2nd-D
The figure shows scanning electron micrographs (magnifications t o, o o
o times). It can be seen that Ag particles are significantly aggregated.

The average diameter of Ag particles is 0.4μ, and the distribution is 0.4μ.
It ranged from 15μ to 0.7μ. The BET surface area of the catalyst is 0
．． It was small at 53g/I. 0.0 in IIS within catalyst particles.
It was confirmed that the distribution of AQ and Nα in the catalyst particles was non-uniform at 0.22 in 60, 12, and ZSNa.

This catalyst was reacted in the same manner as in Example 1, but very low performance was obtained at 250° C., with an oxygen conversion rate of 8 cm and a selectivity of 72 cm.

[Brief explanation of the drawing]

FIG. 1 shows the temperature increase patterns of the catalyst of the present invention (Example 1) and the control catalyst (Comparative Example 1) by air heating. Figures 2-A to 2-D are scanning electron micrographs (10.000x magnification), and Figure 2-A shows the internal porous surface of the catalyst of the present invention (Example 2). . Figure 2-B and Figure 2-C show the inner surface of the pores near the outer surface and inside the control catalyst (Comparative Example 1), respectively, and Figure 2-D shows the inner surface of the pores in the control catalyst (Comparative Example 2). Shows a porous surface. FIG. 3 shows the distribution of silver within the catalyst particles of the catalyst of the present invention (Example 2) and the control catalyst subjected to air heating (Comparative Example 1). Kaya 2'=Figure A, ¥・L-BZ Figure 2C Figure 2'-D Figure 3 Procedural amendment (method) % formula % 1. Display of the case Showa 5 Information Patent II No. 191732 2. Invention Name 3. Relationship with the person making the amendment Patent applicant name (605) Mitsubishi Yuka Co., Ltd. 4, Agent
107 (and 1 other person) Telephone: 585-2256 5. Date of amendment order: January 29, 1985 (shipment date) 6. @Object of correction 4. Brief explanation of the drawing〈: 7. Contents of amendment ( I) Page 45 of the specification, lines 6 to 10, “Figure 2-A is...
......Indicates a porous surface. ” and “2nd-
Figure A shows the particle structure of the internal porous surface of the catalyst of the present invention (Example 2). Figures 2-D and 2-C show the control catalyst (
Figure 2-D shows the particle structure near the outer surface and on the inner surface of the pores of Comparative Example 1), and Figure 2-D shows the particle structure of the control catalyst (Comparative Example 2).
) shows the particle structure of the internal porous surface. ” he corrected.

Claims (1)

[Scope of Claims] 1. A catalyst in which at least silver particles are supported on a porous carrier made of a molded body of a refractory material, which includes: (A) silver on the outer surface and inner surface of the pores of the carrier; (B) the average diameter of the silver particles distributed on the inner surface of the pores of the carrier is within the range of 0.05 to 0.4 microns, and (C) the outer surface of the catalyst is A method for producing ethylene oxide from ethylene, characterized in that the following formula, I≧0.65S, is satisfied between the silver support rate (S) and the silver support rate (I) in the innermost layer of the catalyst. catalyst. 2. The catalyst according to claim 1, wherein the average diameter of the silver particles distributed on the inner surface of the pores of the support (B) is in the range of 0.1 to 0.3 microns. 3. Silver support rate (S) in the outer surface layer of the catalyst (C) above;
The catalyst according to claim 1 or 2, wherein the following formula, 1≧0.7S, is satisfied between the silver support rate (I) in the innermost layer of the catalyst. 4. In addition to supporting at least silver particles on a porous carrier made of a molded body of a refractory material, (D) cation components include (D-1) lithium, sodium, potassium, rubidium, and cesium (alkali). (D-2) calcium and barium (alkaline earth metal elements); and (D-3) at least one element selected from the group consisting of thallium, tin, and antimony. The catalyst according to items 1 to 3 of the range. 5. In addition to supporting at least silver particles on a porous carrier made of a molded body of a refractory material, (D) as a cation component, (D-1) lithium, sodium, potassium, rubidium, and cesium. At least one element selected from the group consisting of (alkali metal element), or at least one element (D-1) and barium (D-2) are supported. Catalysts as described in section. 6. In addition to supporting at least silver particles on a porous carrier made of a molded body of a refractory material, (D) cation components (D-1) lithium, sodium, potassium, rubidium, and cesium (alkali metal (D-2) calcium and barium (alkaline earth metal elements), and (D-3) at least one element selected from the group consisting of thallium, tin, and antimony; and (E)
At least one selected from the group consisting of fluorine, chlorine and bromine as an anion component
The catalyst according to any one of claims 1 to 5, in which a seed element is supported. 7. A cation component is supported on the outer surface and the inner surface of the pores, and the supporting ratio of the alkali metal element as the cation component (S
Claims 1 to 6, wherein the following formula, Ic≧0.3Sc, is satisfied between c) and the supporting ratio (Ic) of the alkali metal element in the innermost layer of the catalyst on the inner surface of the pores. The catalyst according to any one of. 8. At least one cationic component of lithium, sodium, and barium is supported on the outer surface and the inner surface of the pores, and the cation components of lithium and/or sodium in the outer surface layer of the catalyst on the inner surface of the pores are supported. Claim 1, wherein the following formula Ic≧0.3Sc is satisfied between the loading rate (Sc) and the loading rate (Ic) of lithium and/or sodium in the innermost layer of the catalyst on the inner surface of the pores. The catalyst according to any one of items 6 to 6. 9. At least one cationic component (alkali metal element) of potassium, rubidium, and cesium is supported on the outer surface and the inner surface of the pores, and Claim 1, in which the following formula Ic≧0.5Sc is satisfied between the cation component support rate (Sc) and the cation component support rate (Ic) in the innermost layer of the catalyst on the inner surface of the pores. The catalyst according to any one of Items 1 to 6 and 8. 10. A catalyst in which at least silver particles are supported on the porous carrier, wherein the silver particles are supported in an amount of 5 to 20% by weight based on the entire catalyst. Catalyst according to any one of the above. 11. Impregnating a porous carrier made of a molded body of a refractory material with an aqueous solution containing a silver salt and an amine as a complexing agent, and heating the carrier with superheated steam to precipitate silver on the carrier. A method for producing a catalyst for producing ethylene oxide from ethylene, characterized by: 12. The porous carrier impregnated with an aqueous solution containing a silver salt and an amine as a complex forming agent is brought into contact with superheated steam at a temperature of 120°C or higher while containing at least a part of the aqueous solution. 12. The method according to claim 11, wherein silver is deposited on the carrier. 13. The porous carrier impregnated with an aqueous solution containing a silver salt and an amine as a complex forming agent is prepared in a state where the drying rate (removal rate) of the aqueous medium in the aqueous solution is 0 to 80% by weight. 12. The method according to claim 11, wherein silver is deposited on a porous carrier by contacting the carrier with superheated steam at 120 to 500°C.