JPH0450854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the preparation of a silver catalyst for the production of ethylene oxide by the oxidation of ethylene with oxygen, comprising silver and a promoter on a thermostable porous support material. Regarding the method.

Ethylene oxide is produced industrially on a large scale by direct oxidation of ethylene with oxygen over a silver catalyst. A general description of this method can be found in Kirk-Othmer's "Encyclopedia of Chemical Technology", Volume 9, pp. 432-471, John Willey ( John
Wiley), London/New York (1980).

The ethylene- and oxygen-containing gases are introduced into the reactor from the top. The reactor consists of a bundle of several thousand tubes with a length of 6 to 10 meters or more. Gas generally passes through catalysts present in these tubes.
It is run at a temperature of 150 DEG to 400 DEG C. and an overpressure of 0.15 to 3 MPa, with 5 to 20% of the ethylene used reacting.

In addition to the formation of ethylene oxide, a significant proportion of ethylene - approximately 25% - is oxidized to carbon dioxide and water (complete oxidation). This is demonstrated in the reaction equation below: Formation of ethylene oxide: 2C ₂ H ₄ +O ₂ →2C ₂ H ₄
O Complete oxidation: C ₂ H ₄ +3O ₂ →2CO ₂ +2H ₂ O For temperature control and heat removal, a heat transport medium is used which transports the released heat out of the reactor.
The ethylene oxide- and carbon dioxide-containing reaction gas leaves the reactor and passes through a work-up stage in which ethylene oxide and carbon dioxide are separated off. The gas freed from ethylene oxide and carbon dioxide is enriched again with ethylene and oxygen content and is conveyed again to the reaction group.
Continuous circulation methods using heterogeneous catalysis have become a problem.

A silver-supported catalyst is used as the catalyst. The quality of catalysts of this type is essentially characterized by their selectivity, their activity and their pot life. Selectivity is the mole percent of reacted ethylene that reacts to form ethylene oxide. Activity is indicated by the ethylene oxide concentration at the reactor outlet under otherwise constant conditions (eg, temperature, pressure, gas amount, catalyst amount). The higher the ethylene oxide concentration, the greater the activity. In other words, the lower the temperature required to achieve a particular ethylene oxide concentration, the greater the activity.

The production of supported silver catalysts has been known for a long time. It is particularly advantageous to produce it according to the following method: The carrier material is immersed in a solution of the silver salt.

The immersed carrier material is dried, during which the silver salt is deposited on the carrier material.

The carrier material impregnated with the silver salt in this way is subjected to conditions that cause the decomposition of the silver salt, with the formation of elemental silver present in a finely dispersed state on the carrier. This step is carried out, for example, purely thermally by heating to about 170 DEG -400 DEG C. or by using a reducing agent such as formaldehyde. Thermal reduction can be carried out with the introduction of an inert gas such as air, nitrogen, carbon dioxide or mixtures thereof.

In addition to silver, so-called co-catalysts such as potassium, rubidium and/or cesium are also commonly deposited on the support material. This is because it contributes to significantly improving the performance of the finished catalyst.

It has recently been established that high potency silver catalysts are obtained when the support material is impregnated with specific silver salt-amine complex compounds for silver deposition. Many proposals have been made in this regard to date.

According to German Patent Application No. 2159346, which corresponds to U.S. Pat. Impregnation treatment with an aqueous solution containing various organic amines, in which the solubilizing/reducing organic amine is ethylenediamine, a mixture of ethylenediamine and ethanolamine, a mixture of ammonia and ethylenediamine, or a mixture of ammonia and ethanolamine. is preferred.

The silver catalyst known from DE 2300512 contains silver in an amount of 3 to 20% by weight and potassium as cocatalyst in an amount of 0.003 to 0.05% by weight, each based on the weight of the catalyst. It is composed of rubidium and/or cesium supported on a heat-stable porous carrier, and when producing it, in order to deposit silver on the carrier, silver carboxylate-ethylenediamine-complex salt and/or Alternatively, a silver carboxylate-ethanolamine complex salt is used.

German Patent Application No. 2622228 and German Patent Application No. 2640540 describe alkyl groups having 1 to 8 carbon atoms as complex-forming amines for silver salts which may be organic or inorganic. polyamines of alkanes up to about hexane, cycloaliphatic amines such as cyclohexylamine, heterocyclic amines (e.g. pyrrolidone, piperidine and morpholine)
and especially of the general formula (R,R')-CH- _NH2 (wherein,
R and R' are aliphatic groups).

From the two German patent applications No. 2655738 and No. 2734912, at least one silver carboxylate, at least one silver carboxylate, at least one
It is known to use impregnating solutions containing various amines and at least one cesium compound soluble in the silver carboxylate-amine complex. As amines, certain aliphatic diamines, aliphatic polyamines and certain aliphatic aminoethers are used. The impregnating solution may also contain water.

Furthermore, U.S. Pat. No. 4,235,757 describes the formula NH ₂
-R-NH-R'-OH (wherein R and R' are 2 to 4
is an alkyl group having 5 carbon atoms. ) are mentioned as particularly advantageous complexing agents for depositing silver on carrier materials.

Various methods are disclosed in the above-mentioned publications for depositing silver and promoters on support materials. For example German patent application publication no. 2300512
According to the method of No. 2734912 and the specification of No. 2734912,
Silver (silver salt-amine complex) and cocatalyst (cocatalyst compound) are deposited on the support material simultaneously and in an impregnation process. When producing silver catalysts according to German Patent Application No. 26 40 540, there are no restrictions on the method by which silver and cocatalyst are deposited on the support.
The silver and cocatalyst may be deposited simultaneously and in one impregnation step, or they may be deposited one after another, provided that the cocatalyst is deposited in the first impregnation step and the cocatalyst is deposited in the second impregnation step. Silver is deposited in a treatment stage or silver is deposited in a first impregnation stage and a cocatalyst is deposited in a second impregnation stage.

The prior art for preparing silver catalysts with improved properties using silver salt-amine complexes shows, in short, that many complex-forming amines have already been recommended. Nevertheless, on the one hand, the known amine-complexing agents are often relatively difficult to obtain and, on the other hand, the improvements in activity, selectivity and lifetime achieved with them are still far from complete. There is still a need for further proposals of this kind.

Surprisingly, the inventor has found that as complex-forming (solubilizing and reducing) amines mixtures with at least one tertiary-alkylamine and at least one 2-alkylamine are used, in particular found it to be advantageous. This not only results in unexpectedly high activities, selectivities and long lifetimes, but also surprisingly increases in selectivity for ethylene conversion, which cannot be achieved with amines known in the prior art. A silver catalyst with low dependence is obtained.

The capabilities of the proposed amines (amine mixtures) are independent of the method of depositing the silver and cocatalyst on the support.

3-20% by weight of silver and respectively based on the weight of the catalyst (weight of finished catalyst or total weight of catalyst)
0.003-0.05% by weight of potassium as cocatalyst,
A method for producing a catalyst for producing ethylene oxide by direct oxidation of ethylene with molecular oxygen, comprising rubidium and/or cesium supported on a thermostable porous carrier material, comprising: impregnating a support material with a silver salt-amine complex and a cocatalyst compound, drying the impregnated support material and heating to 170-400° C. to decompose the silver salt-amine-complex into silver metal; and the silver salt. -Amine-As an amine for forming a complex salt (a) 10 to 40% by weight of the general formula () (wherein R ₁ , R ₂ and R ₃ mean an alkyl group having 1 to 4 carbon atoms) and (b) 60 to 90% by weight. General formula for () (In the formula, R ₄ and R ₅ mean an alkyl group having 1 to 4 carbon atoms.)

The solubilizing and reducing amine mixture of the present invention preferably comprises 20-30% by weight of at least one tertiary-alkylamine of formula () and 70-80% by weight of at least one tertiary-alkylamine of formula (). 2-alkylamine.

Among the tertiary-alkylamines and sec- ondary-alkylamines used according to the invention, the alkyl group
_{Methyl ( - _}
Preference is given to those with CH ₃ ) or ethyl (-C ₂ H ₅ ). As the tertiary-alkylamine, tertiary
-butylamine, i.e. and the 2-alkylamine is 2-butylamine, i.e. is particularly advantageous.

The complex-forming amine according to the invention is used in at least the amount required to form the silver salt-amine complex, i.e. in an amount that completely dissolves the silver salt used. One silver cation has the chemical formula Ag (amine) ₂
Since there is a stoichiometric bonding of two amino groups according to (X=anion of the silver salt used), it is necessary to use at least two amino groups per mole of silver cation. Therefore, a small molar excess of solubilizing amine is usually used to ensure complete dissolution. The amount of amine according to the invention is generally 2.05 amines per mole of silver in the silver compound used.
-5 mol, preferably 2.1-3 mol.

In the case of the novel silver catalysts, the amount of silver is preferably from 7 to 14% by weight and the amount of cocatalyst (cation, rubidium or cesium or mixtures thereof) is preferably from 0.008 to 0.035% by weight, respectively based on the weight of the catalyst.
Weight%. The promoter is preferably cesium.

There are no restrictions on the type of silver salt and cocatalyst compound used to impregnate the carrier.

Inorganic salts and/or organic salts can be used as silver salts. Suitable organic salts are silver carboxylates, such as silver formate, silver acetate, silver malonate,
Silver oxalate, silver lactate and/or silver citrate. Suitable inorganic salts include silver carbonate, silver nitrate and/or
Or silver nitrite. Of the silver salts mentioned, particular preference is given to silver acetate, silver lactate, silver oxalate, silver carbonate and/or silver nitrate. That is, they are readily available and relatively inexpensive.

Inorganic and/or organic compounds can be used as promoter compounds, salts and hydroxides being preferred. The anion of the cocatalyst compound has no significance for the catalytic action - ie, the cocatalyst acts in the form of a cation in the deposited cocatalyst compound - so there is no restriction. Suitable promoter salts are carboxylates, such as formates, acetates, malonates, oxalates, lactates, tartrates and/or citrates. Purposeful inorganic salts are carbonates,
bicarbonate, phosphate, nitrate and/or nitrite. Among the co-catalyst compounds mentioned above, acetates and/or nitrates are preferred as they are readily available and relatively inexpensive.

Suitable carrier materials for the silver catalysts of the invention are customary commercially available thermostable porous materials. They are also inert under the reaction conditions prevailing during the oxidation of ethylene and under the compounds present. There is no limit to the support material for producing the silver catalyst of the present invention. Suitable carriers are, for example, charcoal, corundum, silicon carbide, silicon dioxide, aluminum oxide, and mixtures of aluminum oxide and silicon dioxide. α-Aluminum oxide is particularly advantageous because it has a very uniform pore diameter. 0.1~ ^1m2 /
g, especially a specific surface area of 0.2 to 0.6 m ² /g (known as BET
method), 0.1 to 1 cm ³ /g, especially 0.2 to 0.6
cm ³ /g (determined by known mercury or water adsorption methods), an apparent porosity of 20 to 70% by volume, in particular 40 to 60% by volume (determined by known mercury or water adsorption methods). pores with an average pore diameter of 0.3 to 15 μm, in particular 1 to 10 μm and a percentage of pores with a diameter of 0.03 to 10 μm, at least 50% by weight (pore diameter and pore diameter distribution are known as (which can be confirmed from the apparent vacancy rate). The carrier material is advantageously used in the form of granules, spheres, rings, pellets and the like. Examples of advantageous α-aluminum oxide or α-aluminum oxide-containing support materials include those of the type SA5551 and SA5552 provided by Norton Company, USA; There is a SAHM-type manufactured by United Catalyst.

The silver and cocatalyst are deposited on the support material by known impregnation methods. In this case, the carrier material is brought into contact with the impregnating solution, in particular by immersion or irrigation, with the solution penetrating into the pores of the carrier material by absorption and/or capillary action.
Then pour off the excess impregnating solution (e.g.
The carrier material is separated off (by dripping, removal or centrifugation) and then thoroughly sucked out to dry, and the silver compound and/or cocatalyst compound is deposited therein.

The amount of impregnating solution is generally selected to be in volumetric excess relative to the volume of carrier material to be impregnated. Generally 0.5 to the volume of carrier material
~3 times, especially 1 to 2 times, the volume of the impregnating solution is used. Impregnation time - This is the time during which the carrier material remains in contact with the impregnation solution.
should of course be selected so that the required amounts of silver compound and cocatalyst compound to be deposited are deposited on the support. This generally ranges from 3 to 60 minutes and depends, inter alia, on the concentration of the impregnating solution of silver compound and cocatalyst compound, the support material used and its occasional suction capacity. The temperature used during the impregnation process can be varied within a wide range. Impregnation is generally carried out at room temperature. Higher temperatures can also be used. The impregnation temperature is therefore usually between 15 and 80°C, in particular between 20 and 50°C. The impregnation process is usually carried out under atmospheric pressure. In order to accelerate the impregnation process, the impregnation process can also be carried out under reduced pressure.

Suitable solvents for making impregnating solutions include:
There are water, organic liquids and mixtures of water and organic liquids. Particularly preferred solvents are water, methanol, ethanol, propanol, isopropanol and acetone and mixtures thereof.

Drying of the impregnated carrier material from which excess impregnating liquid has been separated off is generally carried out at temperatures of 20 DEG to 150 DEG C., in particular 50 DEG to 120 DEG C. Evaporative removal of the solvent can be carried out, for example, by means of trays, dryers, rotary ovens or by passing in hot inert gases such as nitrogen, air and/or carbon dioxide. The temperature generally follows the boiling point of the solvent in the impregnation solution. According to an advantageous embodiment, the drying is carried out in the presence of an inert gas at a temperature of 50 to 120°C.

The dried impregnated support material is generally heated to a temperature of 170 DEG to 400 DEG C., in particular 200 DEG to 350 DEG C., in order to convert the deposited silver salt-amine complex into silver metal (reduction, pyrolysis). Heating to such temperatures can be carried out, for example, in a tray dryer, in a rotary oven, in electrically heated tubes or by passing a correspondingly heated inert gas, such as air, nitrogen, carbon dioxide or a mixture thereof. This can be done by
Conversion of the silver-amine complex to silver metal can also be carried out using overheated steam. According to a particularly advantageous embodiment, the pyrolysis of the deposited silver compounds is carried out by passing air, nitrogen and/or carbon dioxide over the impregnated support material (precatalyst) heated to 200-350°C. and implement it. The heating time required under the above temperature is generally 0.05~5
time, especially 0.1 to 1 hour. By decomposition of the silver compounds, fixed deposits of fine silver metal particles are formed on the support material (the co-catalyst compounds are not reduced to the corresponding metals, thus the alkali metals potassium, rubidium and cesium are substantially is present in its cationic form and not as a free alkali metal). Silver (silver particles)
are generally present in the form of fixed, substantially uniformly distributed, unconnected, discrete particles.

There are no restrictions on the manner in which the amount of silver (in the form of the silver salt-amine complex used) and the amount of co-catalyst (in the form of the co-catalyst compound used) is deposited within the scope of the impregnation process.
For example, silver and cocatalyst may be deposited on the support simultaneously or at different times, ie one after the other, in any order. If silver and co-catalyst are deposited simultaneously, the entire amount of silver and co-catalyst may be deposited in one impregnation process. It is also possible to use multiple impregnations, in particular two impregnations, with each impregnation depositing only a portion of the total amount of silver and cocatalyst. In such a case, 55-85% by weight of the total amount of silver and 15-45% by weight of the total amount of co-catalyst are simultaneously deposited on the support in the first impregnation step, and after drying the respective amounts are deposited in the second impregnation step. It has been found to be advantageous to deposit the residual amount.
If silver and cocatalyst are deposited in succession, first the silver and then the cocatalyst or first the cocatalyst and then the silver, each in one or more impregnation treatments. be able to. If the silver compound is applied first and then the co-catalyst compound, reduction to silver metal may be performed before the co-catalyst compound is deposited, or only an intermediate drying may be performed. According to another method, the total amount of silver and only a portion of the total amount of promoter may be deposited in one impregnation step and the remaining amount of promoter may be deposited in a second impregnation step. In this case, 15 to 10% of the total amount of silver and total cocatalyst amount is added to the first impregnation step.
It has been found advantageous to deposit 45% by weight and reduce the total amount of cocatalyst to silver metal in a second impregnation step with the remainder of the total amount of cocatalyst. Similarly, only a portion of the total cocatalyst and silver may be deposited in the first impregnation step and the remaining amount of silver may be deposited in the second impregnation step. Furthermore, for example, the silver and cocatalyst may be deposited on the carrier in multiple impregnation treatments in alternating order. For example, a portion of the total amount of silver may be deposited first, then a cocatalyst amount in one or more impregnation treatments, and then the remaining amount of silver. Similarly, a cocatalyst may be used to begin with.

The impregnation solution for the chosen impregnation process can vary within a wide range with respect to the concentration of silver compound and cocatalyst compound. These concentrations are determined, as is known, in particular by the desired content of silver and cocatalyst on the support. The concentration of silver and cocatalyst in the impregnation solution is between 3 and 20% by weight, in particular between 7 and 14% by weight of silver and between 0.003 and 0.05% by weight, depending on the impregnation process.
It should be selected such that only % by weight, in particular 0.008 to 0.035% by weight, of cocatalyst can be deposited. By prior experimentation and analytical determination of the amount of silver compound and cocatalyst compound deposited on the support, the desired concentration can be determined easily and quickly. For example, a suitable impregnation solution for simultaneously depositing silver and silver and cocatalyst on a support in one or multiple impregnation processes may consist essentially of (a) water;
(c) 2.1 to 3 moles of amine of the new amine mixture per mole of silver in the silver compound used and (d) 0.03 to 0.1% by weight of cocatalyst compound (each based on the weight of the solution). %).
For the deposition of silver and cocatalyst in each case one or multiple impregnation treatments, the following solutions are suitable, for example: (a) water, (b) 30-40% by weight of a silver compound and (c)
2.1 to 3 mol of amine of the novel amine mixture per mole of silver in the silver compound used or (a) water or a mixture of water and an organic solvent (in particular methanol, ethanol, propanol, isopropanol and acetone) and (b) 0.03 to 3 mol of amine per mole of silver in the silver compound used 0.1% by weight of co-catalyst compound - the above mentioned weight percentages are in each case based on the weight of the solution -
(In short, the solvent is present in these impregnating solutions in such an amount that the stated amounts of the other components are supplemented to make up 100% by weight).

The silver catalyst of the present invention has high activity and selectivity and long lifetime. What is especially good is that
The dependence of selectivity on ethylene conversion is surprisingly low.

The selectivity of silver catalysts to form ethylene oxide depends, as is known, on the amount of ethylene reacted in the reactor, such that an increase in ethylene conversion reduces the selectivity. This greater or lesser dependence on the silver catalyst is a serious drawback. That is, the economical effort to operate an ethylene oxide unit at constantly high full capacity, that is, at a constantly high ethylene conversion rate, must necessarily be accompanied by a decrease in selectivity and, with it, an increase in ethylene losses. I don't get it. Therefore, the less the decrease in selectivity with increasing ethylene conversion of the silver catalyst, the better.

The silver catalyst of the present invention has a selectivity that is significantly less dependent on the ethylene conversion rate than silver catalysts of the prior art. Associated with this is another great advantage that the amount of catalyst required can be kept relatively low compared to known silver catalysts. This is clearly a significant economic advantage in the case of expensive silver catalysts. Furthermore, the silver catalyst according to the invention can be operated with relatively low gas quantities, which results in energy savings in relation to the gas density.

In summary, when using the silver catalyst of the invention, good selectivities can still be achieved with relatively low gas volumes and relatively high ethylene conversions, while all the other advantages mentioned above are present in this case. join.

The method of the present invention for producing the new silver catalyst is simple and easy to carry out. It does not involve complex or expensive process steps and does not require special impregnating solutions. The amines used in accordance with the present invention are readily available, easy to handle, and inexpensive.

The new silver catalyst has a wide range of advantages such as temperature, pressure, residence time, diluents, inhibitors to control the catalytic oxidation of ethylene with oxygen, recirculation, methodological measures to increase the ethylene oxide yield, etc. Used under conditions known per se. Reaction temperature is generally 150-400
℃, especially 175 to 250℃, and the reaction pressure is 0.15 to 250℃.
3 MPa, especially 1-2 MPa. The feed mixture used generally contains 5 to 30 mole % ethylene, 3 to 15 mole % oxygen and the balance inert gases (e.g. nitrogen, carbon dioxide, water vapor, methane, ethane, argon and the like) and inhibitors. as vinyl chloride, 1,2-dichloroethane and the like. Ethylene oxide is isolated from the reaction product in the customary manner and the gas mixture is purified, if desired, in the customary manner and recycled. According to a particularly advantageous embodiment using the silver catalyst of the invention, 175
Ethylene oxide is produced by oxidizing ethylene at temperatures of ~250°C.

The invention will be explained in more detail in the following examples.

Example 1 To prepare the catalyst of the invention, 21.000 g (26.5655% by weight) water 30.000 g (37.9502% by weight; 0.177 mol silver) 7.000 g silver nitrate (8.8555 % by weight; 0.096 mol) tertiary-butylamine 21.000 g (26.5655 % by weight) (% by weight; 0.287 mol) 0.050 g (0.0633 % by weight) of tert-butylamine A solution consisting of cesium nitrate is prepared (in short, 25% by weight of tert-butylamine and 75% of 2-butylamine based on 0.177 mol of silver). -0.383 with butylamine
moles of the amine of the invention - this is 2.16 moles of this amine per mole of silver).

In this solution, United Catalyst's SAHM - i.e. 0.2 m ² /
A cylindrical .alpha.-aluminum oxide support material having a specific surface area of g is thoroughly immersed at 40.degree. C. for 15 minutes. After dripping off the excess impregnating solution, the wet carrier material is dried for 30 minutes at 110 DEG C. under an air-nitrogen atmosphere. 25 g of the support thus soaked and dried are then filled into a glass tube preheated to 200° C. in order to reduce the silver compounds present on the support. per hour into this tube with an internal diameter of 30 mm and a length of 300 ml.
30 air flows through from below. Approximately 50 mm above the support to be reduced is blown with 60 nitrogen per hour to avoid possible explosions. After 30 minutes of reduction reaction, a usable finished silver catalyst containing 8.7% by weight of silver and 0.014% by weight of cesium is obtained.

20 ml of this catalyst are used for the reaction with an ethylene/oxygen mixture at 185 DEG C. under atmospheric pressure in a glass reactor. The gas used was 30% ethylene by volume.
It contains 8% by volume oxygen, 0.0003% by volume vinyl chloride, and the balance nitrogen. The catalyst loading is 400 gases per hour per catalyst.

The reaction product leaving the reactor contains 1.8% by volume of ethylene oxide. Analytical investigations of the amounts of ethylene oxide, carbon dioxide and reacted ethylene formed yield the selectivity (number of moles of ethylene oxide formed per mole of reacted ethylene) and the ethylene conversion rate (number of moles of ethylene oxide formed per mole of reacted ethylene). (capacity%).
The selectivity is 80.7% under 7.7% ethylene conversion. Even after a two-month experimental period, no decrease in selectivity was still observed.

To test the dependence of the selectivity of this catalyst on ethylene conversion, the reaction temperature is increased from 185°C to 192°C. Ethylene conversion rate is now 12%
(previously 7.7%) and the amount of ethylene oxide formed is 2.9% by volume (previously 1.8% by volume)
It is. A selectivity rate of 79.0% is obtained. in short,
Even though the ethylene conversion increased by 4.3 units, the selectivity decreased by only 1.7 units.

Example 2 To prepare a catalyst according to the invention, 21.000 g (26.9058% by weight) water 30.000 g (38.4369% by weight; 0.179 mol silver) 5.000 g silver acetate (6.4061% by weight; 0.068 mol) tertiary-butylamine 22.000 g ( 28.1871% by weight; 0.301 mol) 0.050 g (0.0641% by weight) of tert-butylamine A solution consisting of cesium acetate is prepared (in short, for 0.179 mol of silver, 18.5% by weight of tert-butylamine and 81.5% by weight of cesium acetate). with 2-butylamine
0.369 moles of the amine of the invention are used, which is 2.06 moles of amine per mole of silver).

Norton SA5552−0.3m ² /g
A cylindrical α-aluminum oxide carrier material having a specific surface area of .

Soaking at 50° C. for 15 minutes, drying and reduction reaction are carried out as in Example 1. A silver catalyst containing 8.8% by weight of silver and 0.015% by weight of cesium is obtained.

This catalyst produces 1.8% by volume of ethylene oxide at 183°C under the experimental conditions of Example 1.
From the analytically determined amounts of ethylene oxide, carbon dioxide and reacted ethylene, a selectivity of 80.5% is calculated at an ethylene conversion of 7.9%. When increasing the temperature to 190° C., a selectivity of 79% is obtained with 2.8% ethylene oxide by volume and an ethylene conversion of 11.7%. in short,
Although the ethylene conversion increased by 3.8 units, the selectivity decreased by only 1.5 units.

Even after a two-month experimental period under these conditions, no decrease in selectivity was still observed.

Example 3 (Comparative example) In this example, in order to compare with the example of the present invention,
Do not use butylamine. Proceed as in Example 2. The impregnation solution is: 21.000g (26.5655% by weight) Water 30.000g (37.9505% by weight; 0.177 mol of silver) Silver nitrate 28.000g (35.4207% by weight; 0.383 mol) Sec-Butylamine 0.050g (0.0633% by weight) Cesium acetate Composed.

The resulting silver catalyst has 8.6% by weight silver and 0.015% by weight cesium.

This catalyst produces 1.8% by volume of ethylene oxide at 193°C under the experimental conditions of Example 1.
A selectivity of 79.5% was calculated at an ethylene conversion of 8%. When the reaction temperature is increased to 195℃,
2.7% by volume of ethylene oxide is produced and a selectivity of 77% is confirmed under 12% ethylene conversion. An increase in ethylene conversion of only 4 units decreased selectivity by 2.5 units. After a two-month experimental period under these conditions, the selectivity decreases by an additional 0.3 units.

Example 4 (comparative example) Instead of the amine mixture according to the invention, a mixture according to German Patent No. 2159346 (corresponding to US Pat. No. 3702259) of 5.0 g of ethanolamine and 12.0 g of ethylenediamine is used. Repeat Example 2 except. The impregnation solution is 21.000g (30.8597% by weight) Water 30.000g (44.0852% by weight; 0.179 mol of silver) Silver acetate 5.000g (7.3475% by weight; 0.082 mol) Ethanolamine 12.000g (17.6341% by weight; 0.200 mol) Ethylenediamine 0.050 g (0.0735% by weight) Composed of cesium acetate. (The 0.082 moles of ethanolamine correspond to 0.46 moles of ethanolamine per mole of silver, and the 0.200 moles of ethylenediamine correspond to 1.12 moles of ethylenediamine per mole of silver. That is, ethylenediamine has two amino groups. ) This catalyst is tested as in Example 1. The test results are summarized below.

Temperature Ethylene Conversion Selectivity °C % % 192 7 78.5 196 11 75.5 Example 5 (Comparative Example) In place of the amine mixture of the present invention, U.S. Pat.
30.0 g of amine _H2N- according to specification 4235757
Example 2 is repeated except using _{CH2CH2 -} NH- _{CH2CH2 -} OH. The impregnation solution was: 21.000 g (25.9099% by weight) Water 30.000g (37.0142% by weight; 0.179 mol of silver) 30.000 g (37.0142% by weight; 0.289 mol) of silver acetate H ₂ N-CH ₂ CH ₂ -NH-CH ₂ CH2 _- OH 0.050g (0.0617% by weight) Composed of cesium acetate. (This 0.289 mole of amine corresponds to 1.61 mole of amine per mole of silver; ie, the amine has two complex-forming amino groups.) The catalyst is tested as in Example 1. The results of the test are summarized below.

Temperature Ethylene Conversion Selectivity °C % % 192 7 79 196 10 76.5 Example 6 To prepare the catalyst according to the invention 91.5 g of aluminum oxide rings as described in Example 1 were mixed with 10.500 g (26.5823% by weight) of water 15.000 g (37.9747% by weight; 0.088 mol of silver) 3.800 g (9.6203% by weight; 0.052 mol) of silver nitrate 10.200 g (25.8227% by weight; 0.0139 mol) of tertiary-butylamine in a solution consisting of 2-butylamine at 40°C. (in short, for 0.088 moles of silver, 0.0191 moles of the amine of the invention consisting of 27% by weight tert-butylamine and 73% by weight sec-butylamine - this is silver). 2.16 moles of this amine are used per mole). After dripping off the excess impregnating solution, it is dried at 110° C. for 30 minutes.
The thus soaked and dried support was then heated for 3 minutes at 40° C. to a solution consisting of 0.670 g (0.0670% by weight) cesium nitrate 994.330 g (99.4330% by weight) methanol 5.000 g (0.500% by weight) water After soaking and allowing excess solution to drip off, it is dried at 110° C. for 15 minutes.
The reduction reaction is carried out as described in Example 1.

All the silver is removed at the beginning during manufacturing (initial impregnation treatment)
Then (second impregnation treatment), this finished catalyst, in which all of the cesium was deposited on the carrier, was 8.7% by weight.
of silver and 0.017% by weight of cesium.

Under the test conditions of Example 1, 1.5% by volume of ethylene oxide is produced at 189°C. In this case, 7
% ethylene conversion, a selectivity of 81% could be achieved.

Example 7 To prepare a catalyst according to the invention, 91.5 g of aluminum oxide rings, as described in Example 1, are placed in a solution consisting of 0.900 g (0.090% by weight) cesium nitrate, 999.100 g (99.910% by weight) water. Soak for 5 minutes at room temperature. After removing the excess solution by decantation, the carrier is dried at 110° C. for 1 hour. Next, to the ring cooled to room temperature were added: 10.500 g (26.5823 wt %) Water 15.000 g (37.9747 wt %; 0.088 mol silver) Silver nitrate 3.500 g (8.8607 wt %; 0.048 mol) Tertiary-butylamine 10.500 g (26.5823 wt %) %; 0.144 mol) 36 g of a silver impregnation solution consisting of 2-butylamine are poured into a stirred drum and stirred gently for 3 minutes at room temperature. (In summary, for 0.088 moles of silver, 0.192 moles of the amine of the invention consisting of 25% by weight tert-butylamine and 75% by weight sec-butylamine - this is 2.16 moles of this amine per mole of silver).
Use - which is mole. ) After a standing time of 5 minutes, the drum contents are dried for 30 minutes at 110 DEG C. and then reduced in an air-nitrogen stream as described in Example 1.

The finished catalyst, which during its manufacture first deposited all the cesium (first impregnation) and then (second impregnation) all the silver on the support, contains 8.6% by weight silver and 0.018% by weight cesium. Contains.

This catalyst was rated at 1.6 at 190°C under the test conditions of Example 1.
Produce % ethylene oxide by volume. In this case, the selectivity is 80.8 at 6% ethylene conversion.
%.

Example 8 To prepare the catalyst of the invention, initially 26.582g (26.5823% by weight) Water 37.975g (37.9747% by weight; 0.223 mol) Silver nitrate 8.860g (8.8607% by weight; 0.121 mol) Tertiary-butylamine 26.590g ( 26.5823% by weight; 0.363 mole) Prepare a solution consisting of 25% by weight tert-butylamine and
0.484 consisting of 75% by weight sec-butylamine
moles of the amine mixture of the invention, which is 2.17 moles of this amine per mole of silver).

90 g of carrier material according to Example 1 and 35.2 g in a rotatable synthetic resin drum in the first impregnation step.
Pour in the above silver-amine impregnation solution.
The carrier material absorbs all of the solution. The drum contents are dried in a drying cabinet at 120° C. for 40 minutes (weight loss is 10 g). With this treatment, the carrier becomes 25.8
The silver salt-amine complex salt of g is attached. After cooling to room temperature, the rings are sprayed in a second impregnation in the stirred drum described above with a cesium impregnation solution of 38 mg of cesium nitrate in 10 g of water.
The entire solution is then sprayed on. Then 120
Dry under °C (weight loss is 9 g).
The entire amount of cesium is deposited in this second impregnation step. After cooling to room temperature, in a third impregnation step 8.6 g of the above silver-amine impregnation solution was deposited as in the first impregnation and then heated at 110° C. for 30 minutes. Dry with.

The crude catalyst thus prepared is reduced as described in Example 1 with an air-nitrogen mixture. The finished catalyst is 10.6
Contains % silver and 0.026% cesium by weight.

This catalyst was tested as in Example 1 and the following results were obtained: Temperature Ethylene Conversion Selectivity (°C) (% by Volume) (%) 193 7 81.3 197 10 79.5 Example 9 Sequence of Impregnation Steps Repeat Example 8 with the following changes: 1st impregnation step: first silver deposition 2nd impregnation step: 2nd silver deposition 3rd impregnation step: cesium deposition The finished catalyst is 10.6 wt% silver and 0.026wt%
Contains mucium.

This catalyst was tested as in Example 1 and the following results were obtained: Temperature Ethylene conversion Selectivity (°C) (% by volume) (%) 194 7 81.1 198 10 79.2

Claims (1)

[Claims] 1. 3 to 20% by weight based on the weight of each catalyst
of silver and 0.003 to 0.05% by weight of potassium, rubidium, cesium or mixtures thereof as promoters on a thermostable porous support by direct oxidation of ethylene with molecular oxygen. In a method for producing a silver catalyst for producing ethylene oxide, the above carrier material is impregnated with a silver salt-amine complex salt and a cocatalyst compound, the impregnated carrier material is dried, and the silver salt-amine complex salt is impregnated with the carrier material. (a) 10 to 40% by weight of the general formula () as an amine to form a silver salt-amine complex; (wherein R ₁ , R ₂ and R ₃ mean an alkyl group having 1 to 4 carbon atoms) and (b) 60 to 90% by weight General formula for % () (In the formula, R ₄ and R ₅ mean an alkyl group having 1 to 4 carbon atoms.) , the above method. 2. The method of claim 1, wherein the tertiary-alkylamine is tertiary-butylamine and the sec- ond-alkylamine is sec-butylamine. 3. A process according to claim 1 or 2, wherein the amount of silver on the support material is from 7 to 14% by weight and the amount of promoter is from 0.008 to 0.035% by weight. 4. The method according to any one of claims 1 to 3, wherein cesium is used as a promoter.