JP5143610B2 - Method for producing catalyst for producing ethylene oxide - Google Patents

Description

  The present invention relates to a method for producing a catalyst for producing ethylene oxide. Specifically, the present invention relates to a method for producing a catalyst that is excellent in catalyst activity, selectivity, and catalyst life, and that can produce ethylene oxide with high selectivity over a long period of time.

  It is widely used industrially to produce ethylene oxide by catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst. As for the silver catalyst used for this catalytic gas phase oxidation, conventionally, the combination of silver as a main active component and a cocatalyst (alkali metal, etc.) and the optimization of the composition such as the compounding ratio, the improvement of the carrier supporting these, Many techniques, such as examination of preparation methods, such as an impregnation method, are proposed.

  For example, in Patent Document 1, after impregnating a carrier with a silver compound and a complex-forming compound, it is introduced into a continuous heating apparatus capable of supplying and exhausting atmospheric gas as a pre-process, and the heated atmospheric gas is circulated. After the heat treatment, a catalyst production method is disclosed in which a new gas such as heated steam is passed through the impregnated support as a post-process. Patent Document 2 discloses a catalyst having at least 30% by weight or more of silver supported on a refractory solid support. Further, Patent Document 3 discloses a method of impregnating a support with a part of an alkali metal as a promoter, and then impregnating the remaining promoter and silver. Patent Documents 4 and 5 disclose a method of dividing and supporting a part of silver supported on a catalyst.

Although the catalytic activity, selectivity and catalyst life of silver catalysts have already reached a high level, there is still a need for improvement in these performances. For example, if the selectivity is taken as an example, the production scale of ethylene oxide is large, and even if the selectivity is improved by only 1%, the amount of raw material ethylene used is remarkably saved, and its economic effect is great. Under such circumstances, the development of silver catalysts having better catalytic performance has been a continuous theme for researchers in the technical field.
Japanese Patent No. 3823716 Japanese Patent No. 3030512 JP-A-8-224477 JP-A-6-92949 JP 2007-301554 A

  The present invention has been made in view of the above-described conventional technology and its problems, and has means for producing a catalyst having excellent catalytic performance and capable of producing ethylene oxide with high selectivity over a long period of time. The purpose is to provide.

  The present inventors have intensively studied to solve the above-described problems. In the process, the inventors studied focusing on the impregnation method of the catalyst component into the carrier when producing the catalyst for ethylene oxide production. As a result, when impregnating the support with the catalyst component-containing solution containing silver, alkali metal and water, the silver concentration of the solution is adjusted to 1 to 15% by mass in terms of elements, It has been found that a catalyst having excellent catalytic performance can be obtained by impregnating the support twice or more, and the present invention has been completed.

  That is, in the method for producing an ethylene oxide production catalyst of the present invention, an impregnation step of impregnating a support mainly composed of alumina with a catalyst component-containing solution containing silver, an alkali metal and water, and firing the support after impregnation. Firing step. In the impregnation step, the support is impregnated twice or more times with a catalyst component-containing solution having a silver concentration of 1 to 15% by mass in terms of element.

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst which has the outstanding catalyst performance and can manufacture ethylene oxide with high selectivity over a long term can be manufactured. In addition, ethylene oxide can be produced with high productivity by vapor-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a catalyst obtained by such a technique. The above utility value is extremely large.

  Embodiments of the present invention will be described below.

  The present invention provides an ethylene oxide production catalyst comprising an impregnation step of impregnating a support containing alumina as a main component with a catalyst component-containing solution containing silver, an alkali metal and water, and a firing step of firing the support after impregnation. A method for producing an ethylene oxide production catalyst, characterized in that, in the impregnation step, the support is impregnated twice or more with the catalyst component-containing solution having a silver concentration of 1 to 15% by mass in terms of element. Is the method.

  As described above, the production method of the present invention is characterized in that the silver concentration in the catalyst component-containing solution used in the impregnation step is controlled to a value within a predetermined range, and the support is impregnated twice or more. . Therefore, other forms (such as the structure of the carrier and the specific form of the catalyst component) are not particularly limited.

  Hereinafter, although the manufacturing method of this invention is demonstrated in detail in order of a process, the technical scope of this invention is not restrict | limited only to the following form.

[Impregnation process]
In this step, the support is impregnated with the catalyst component-containing solution.

  In this step, first, a carrier is prepared. There is no restriction | limiting in particular about the specific form of a support | carrier, A conventionally well-known knowledge can be referred suitably.

  For example, the composition of the carrier is not particularly limited except that the main component is alumina. Here, the carrier “mainly composed of alumina” means that the content of alumina (preferably α-alumina) in the carrier is 90% by mass or more with respect to 100% by mass of the total mass of the carrier. means. The content of alumina in the support is preferably 95% by mass or more, and more preferably 98% by mass or more. The other composition is not particularly limited as long as it is mainly composed of alumina, but the carrier may contain, for example, an oxide of an alkali metal or alkaline earth metal or an oxide of a transition metal. Although there is no restriction | limiting in particular also about these content, Preferably content of the oxide of an alkali metal or alkaline-earth metal is 0-5 mass% in conversion of an oxide, More preferably, it is 0.01-4 mass %. The content of the transition metal oxide is preferably 0 to 5% by mass, more preferably 0.01 to 3% by mass in terms of oxide.

  The support also usually contains silica (silicon oxide). Although there is no restriction | limiting in particular about content of the silica in a support | carrier, Preferably it is 0.1-5 mass%, More preferably, it is 0.3-3 mass%.

  The composition of the carrier and the content of each component described above can be determined using a fluorescent X-ray analysis method.

  The shape of the carrier is not particularly limited, and conventionally known knowledge can be appropriately referred to in addition to a ring shape, a spherical shape, a cylindrical shape, and a pellet shape. Moreover, there is no restriction | limiting in particular also about the size (average diameter) of a support | carrier, Preferably it is 3-20 mm, More preferably, it is 5-10 mm.

  The particle size of the carrier is not particularly limited, but the primary particle size of the carrier is preferably 0.01 to 100 μm, more preferably 0.1 to 20 μm, and further preferably 0.5 to 10 μm. Especially preferably, it is 1-5 micrometers. The secondary particle size of the carrier is preferably 0.1 to 1,000 μm, more preferably 1 to 500 μm, still more preferably 10 to 200 μm, and particularly preferably 30 to 100 μm.

The BET specific surface area of the carrier is not particularly limited, but is preferably 0.03 to 10 m ² / g, more preferably 0.3 to 5.0 m ² / g, and further preferably 0.6 to 2 0.5 m ² / g. If the BET specific surface area of the support is 0.03 m ² / g or more, the water absorption rate is sufficiently secured and the catalyst component can be easily supported. On the other hand, if the BET specific surface area of the support is 10 m ² / g or less, the pore diameter of the support is maintained at a certain large value, and the sequential oxidation of ethylene oxide during the production of ethylene oxide using the produced catalyst can be suppressed.

  The pore volume of the carrier is not particularly limited, but is preferably 0.2 to 0.6 mL / g, more preferably 0.3 to 0.5 mL / g, and further preferably 0.35 to 0.45 mL. / G. If the pore volume of the carrier is 0.2 mL / g or more, it is preferable in that the catalyst component can be easily supported. On the other hand, if the pore volume of the carrier is 0.6 mL / g or less, it is preferable in that the strength of the carrier can be ensured to a practical level. As the pore volume value of the carrier, a carrier deaerated at 200 ° C. for at least 30 minutes by a mercury intrusion method is used as a sample, and Autopore III9420W (manufactured by Shimadzu Corporation) is used as a measuring device. Values measured at a pressure range of ˜60,000 psia (6895 Pa to 613.7 MPa) and 60 measurement points shall be adopted.

  The size of the pores of the carrier is not particularly limited, but the average pore diameter is preferably 0.1 to 10 μm, more preferably 0.2 to 4.0 μm, and further preferably 0.3 to 3 μm. 0.0 μm. If the average pore diameter is 0.1 μm or more, the sequential oxidation of ethylene oxide accompanying the retention of the product gas during the production of ethylene oxide can be suppressed. On the other hand, if the average pore diameter is 10 μm or less, the strength of the carrier can be ensured to a practical level. As the value of the average pore diameter, a value measured by a method similar to the method (mercury intrusion method) described above as a method for measuring the pore volume of the carrier is adopted.

  Although there is no restriction | limiting in particular also about the water absorption rate of a support | carrier, Preferably it is 20 to 60%, More preferably, it is 30 to 50%. If the water absorption of the carrier is 20% or more, the catalyst component can be easily supported. On the other hand, if the water absorption rate of the carrier is 60% or less, the strength of the carrier can be ensured to a practical level. In addition, as a value of the water absorption rate of the carrier, a value obtained by a technique called Archimedes method is adopted.

  As a method for preparing the carrier, it is known that the physical properties of the carrier can be controlled by adopting the following method. That is, 1) a method of adding a pore-forming agent having a desired size and amount to a mother powder mainly composed of α-alumina, and 2) preparing at least two kinds of mother powders having different physical properties at a desired mixing ratio. 3) a method of firing the carrier at a desired temperature for a desired time, and the like, and a method combining these methods is also known. These preparation methods are described in, for example, “Characteristics of Porous Materials and Their Application Technologies”, supervised by Satoshi Takeuchi, published by Fuji Techno System Co., Ltd. (1999). Reference can also be made to JP-A-5-329368, JP-A-2001-62291, JP-A-2002-136868, JP-A-2984740, JP-A-3256237, JP-A-3295433, and the like.

  Next, a catalyst component-containing solution is prepared. The catalyst component-containing solution is a solution used for supporting a catalyst component on a carrier. In the present invention, the catalyst component-containing solution essentially contains silver, an alkali metal, and water.

  As a method for preparing the catalyst component-containing solution, specifically, a silver compound and an alkali metal-containing compound are added to water as a solvent.

  Although there is no restriction | limiting in particular about the kind of silver compound, For example, silver nitrate, silver carbonate, silver oxalate, silver acetate, silver propionate, silver lactate, silver citrate, silver neodecanoate etc. are mentioned. Among them, silver oxalate, silver acetate, silver propionate, silver lactate, silver citrate and silver neodecanoate which are organic acid silver are preferable, and silver oxalate is particularly preferable. These may be used alone or in combination of two or more.

  Moreover, there is no restriction | limiting in particular also about the kind of alkali metal containing compound, What is necessary is just a compound containing at least 1 element selected from lithium, sodium, potassium, rubidium, and a cesium as an alkali metal. Among these, a compound containing cesium as an alkali metal is preferable. Specific examples include the above-mentioned alkali metal nitrates, carbonates, oxalates, halides, acetates, sulfates, and the like. These may be used alone or in combination of two or more.

  A complexing agent is added to the catalyst component-containing solution as necessary. Examples of the complexing agent include monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, propylenediamine, and pyridine. These may be used alone or in combination of two or more.

  The catalyst component-containing solution essentially contains water as a solvent. The reason why the inclusion of water is an essential constituent requirement is that the yield decreases only with an organic solvent such as a complexing agent, and it becomes difficult to obtain a predetermined amount of support. As a means to solve this, it is theoretically possible to obtain a predetermined amount of silver supported by increasing the silver concentration in the solution. However, in such a case, the catalyst component does not reach the inside of the pores in the end. Instead, the catalyst is locally supported on the outer surface of the carrier and the dispersibility of the catalyst component is greatly reduced. Furthermore, organic solvents are usually expensive and often have high flammability, and it is desirable to reduce them as much as possible in the manufacturing process.

  A reaction accelerator may optionally be added to the catalyst component impregnation solution. Examples of the reaction accelerator include alkaline earth metals, rhenium, tungsten, thallium, chromium, molybdenum, and sulfur. These may be used alone or in combination of two or more.

  One feature of the production method of the present invention is that the silver concentration in the catalyst component-containing solution used in the impregnation step is controlled to a value within a predetermined range. That is, the silver concentration of the catalyst component-containing solution prepared in this step is 1 to 15% by mass in terms of elements. When the silver concentration of the solution is less than 1% by mass, a large amount of solvent is required to obtain the target loading amount, and therefore, it takes a lot of time and energy to remove the solvent, which leads to an increase in production cost. Absent. On the other hand, when the silver concentration of the solution exceeds 15% by mass, it is difficult to make silver fine particles in the obtained catalyst and carry it in a highly dispersed state, and as a result, sufficient catalytic performance may not be obtained. In addition, the silver concentration of the solution is preferably 3 to 15% by mass, more preferably 5 to 15% by mass.

There is no restriction | limiting in particular in the alkali metal density | concentration in a catalyst component containing solution. The alkali metal contained in the catalyst component-containing solution is preferably cesium, but the concentration of cesium in the catalyst component-containing solution particularly when containing cesium is preferably 1 × 10 ^{−3 to} 20 × 10 with respect to 1 mol of silver. ⁻³ mol, more preferably 2 × 10 ⁻³ to 15 × 10 ⁻³ mol, and even more preferably 3 × 10 ⁻³ × 10 × 10 ⁻³ mol. When the cesium concentration in the case of containing cesium is a value within such a range, the catalyst performance can be further improved.

  Next, the catalyst component-containing solution prepared above is impregnated in the carrier prepared as described above. Another feature of the production method of the present invention is that the support is impregnated with the catalyst component-containing solution twice or more. Thus, a desired amount of the catalyst component is supported on the support. Therefore, as long as a desired amount of the catalyst component is finally supported on the carrier, other specific forms are not particularly limited as long as the catalyst component-containing solution is supported on the carrier twice or more.

  The number of times the catalyst component-containing solution is impregnated into the support may be two or more. However, if the number of impregnations is too large, the production efficiency decreases as the number of man-hours for production decreases. The performance improvement effect diminishes with the increase. For this reason, the number of impregnations is preferably 2 to 5 times, more preferably 2 to 3 times, and particularly preferably 2 times.

  Conventionally, when a catalyst component is impregnated in a carrier having a low water absorption rate, in order to achieve a loading rate comparable to that of a carrier having a high water absorption rate, it is usually impregnated using a catalyst component-containing solution containing silver at a high concentration. It was necessary to carry out the process. In contrast, according to the present invention, by performing the impregnation step by dividing the solution into two or more times, even if the support is impregnated with a catalyst component-containing solution having a lower concentration than in the prior art, Dispersion is possible and the catalyst performance is improved.

  The temperature at which the catalyst component-containing solution is impregnated into the support (temperature in the impregnation vessel) is not particularly limited, but is preferably 0 to 100 ° C, more preferably 20 to 80 ° C. Also, the impregnation time in one impregnation is not particularly limited, but is usually 1 to 120 minutes, preferably 5 to 60 minutes.

  In this step, the impregnation operation is performed twice or more. After each impregnation operation, it is preferable to perform the drying step with reference to conventionally known knowledge. Although there is no restriction | limiting in particular about the detail of such a drying process, If an example is given, it will be 0.1 to 2 hours at the temperature of about 80-120 degreeC in inert gas atmosphere, such as air, oxygen gas, or nitrogen. It is good to dry. Although there is no restriction | limiting in the pressure in a drying process, For example, it is preferable to reduce pressure to about 0.01-0.08 MPa, since drying time can be shortened. Moreover, there is also an advantage that the catalyst component can be supported in a highly dispersed manner within the pores of the carrier by performing drying under reduced pressure. Note that the decompression may be performed consistently during the drying process, or may be performed during a part of the drying process. Further, even after the drying process is performed under such conditions, the supported silver is not converted into a metal simple substance, but is converted into a metal simple substance only after a firing process described later.

  In this step, the reaction accelerator may be similarly dissolved in the aqueous solution in which silver ions are dissolved as described above and impregnated on the support at the same time as silver, or before or after supporting silver. It may be supported on a carrier. In the case of supporting separately from silver, a supporting solution (for example, an aqueous solution) may be separately prepared and a carrier may be supported on this.

[Baking process]
Then, the support | carrier with which the catalyst component carry | supported obtained through the said impregnation process (a drying process is included) is baked. This completes the ethylene oxide production catalyst that is the final object of the present invention.

  Firing is preferably performed in an atmosphere of air, oxygen, or an inert gas (for example, nitrogen) at a temperature of 150 to 700 ° C., preferably at a temperature of 200 to 600 ° C. for about 0.1 to 100 hours. In addition, baking may be performed only in one step or may be performed in two or more steps. As preferable firing conditions, the first stage firing is performed in an air atmosphere at 150 to 250 ° C. for 0.1 to 10 hours, and the second stage firing is performed in an air atmosphere at 250 to 450 ° C. for 0.1 to 10 hours. The conditions for 10 hours are mentioned. More preferably, after firing in such an air atmosphere, firing may be performed at 450 to 700 ° C. for 0.1 to 10 hours in an inert gas (eg, nitrogen, helium, argon, etc.) atmosphere. .

[Catalyst for ethylene oxide production]
According to the production method of the present invention, a catalyst having a structure in which a catalyst component is supported on a carrier can be obtained.

  There is no particular limitation on the amount of silver or reaction accelerator supported, and it may be supported in an amount effective for the production of ethylene oxide. For example, in the case of silver, the supported amount is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and further preferably 8 to 15% by mass based on the mass of the ethylene oxide production catalyst. The amount of the reaction accelerator supported is usually 0.001 to 2% by mass, preferably 0.01 to 1% by mass, more preferably 0.1 to 0%, based on the mass of the catalyst for producing ethylene oxide. 0.7% by mass. More specifically, from the viewpoint of further exerting the effects of the present invention, the amount of alkali metal supported when an alkali metal is used as the catalyst component (the total amount supported when two or more alkali metals are used). Is preferably 0.03 to 1.0 mass%, more preferably 0.05 to 0.5 mass%, based on the mass of the catalyst. In particular, the amount of cesium supported when cesium is used as the alkali metal is preferably 0.001 to 2 mass%, more preferably 0.01 to 1 mass%, based on the mass of the catalyst. More preferably, it is 0.02-0.5 mass%. Further, the amount of rhenium supported when rhenium is used as the reaction accelerator is preferably 0.001 to 0.2% by mass, more preferably 0.005 to 0.1% by mass, based on the mass of the catalyst. More preferably, it is 0.01-0.05 mass%.

  According to another aspect of the present invention, there is provided a method for producing ethylene oxide, comprising the step of vapor-phase oxidizing ethylene with a molecular oxygen-containing gas in the presence of the catalyst for producing ethylene oxide of the present invention.

  The method for producing ethylene oxide of the present invention can be carried out according to a conventional method except that the catalyst for producing ethylene oxide of the present invention is used as a catalyst.

For example, general conditions on an industrial production scale, that is, reaction temperature 150 to 300 ° C., preferably 180 to 280 ° C., reaction pressure ^{2 to} 40 kg / cm ² G, preferably 10 to 30 kg / cm ² G, space velocity 1 3,000 to 30,000 hr ⁻¹ (STP), preferably 3,000 to 8,000 hr ⁻¹ (STP) is employed. Examples of the raw material gas to be brought into contact with the catalyst include 0.5 to 40% by volume of ethylene, 3 to 10% by volume of oxygen, 5 to 30% by volume of carbon dioxide, the remaining inert gas such as nitrogen, argon and water vapor, methane, ethane and the like And those containing 0.1 to 10 ppm by volume of halides such as ethylene dichloride and diphenyl chloride as reaction inhibitors. Examples of the molecular oxygen-containing gas used in the production method of the present invention include air, oxygen, and enriched air.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In this example, various parameters of the carrier were measured by the following method.

<Measurement of specific surface area of carrier>
After pulverizing the carrier, about 3.0 g, which was classified to a particle size of 0.85 to 1.2 mm, was accurately weighed. The weighed sample was deaerated at 200 ° C. for at least 30 minutes and measured by the BET (Brunauer-Emmet-Teller) method.

<Measurement of silica content in carrier>
Measured by fluorescent X-ray analysis.

<Measurement of water absorption rate of carrier>
In accordance with the method described in Japanese Industrial Standard (JIS R 2205 (1998)), the measurement was performed by the following method.

  a) The carrier before crushing was placed in a drier kept at 120 ° C., and the mass when reaching a constant weight was weighed (dry mass: W1 (g)).

  b) The carrier weighed in a) above was submerged in water and boiled for 30 minutes or more, and then cooled in room temperature water to obtain a saturated sample.

  c) The saturated sample obtained in the above b) was taken out from the water, and the surface was quickly wiped with a compress, and after removing water droplets, weighed (saturated sample mass: W2 (g)).

  d) The water absorption was calculated according to the following formula 1 using W1 and W2 obtained above.

Example 1
After adding 1 liter of distilled water to 1 liter of alumina carrier A (outer diameter 8 mm, inner diameter 4 mm, length 8 mm) having a surface area of 1.5 m ² / g and a water absorption rate of 45%, boiled and washed under normal pressure for 30 minutes, Removed and washed with distilled water. Furthermore, after this boiling washing was repeated twice, it was dried at 120 ° C. for 3 hours. 100 parts by mass of the carrier after the above treatment was deaerated at 100 ° C. for 1 hour. Hereinafter, the same carrier A was used in Examples 1 to 9 and Comparative Examples 1 to 4.

  On the other hand, 8.0 parts by mass of ethylenediamine and 44.1 parts by mass of water were dissolved in 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate to prepare a catalyst component-containing solution in which silver and cesium coexisted. The silver concentration of this solution was 15% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver. 100 parts by mass of the carrier after the above treatment was placed in an eggplant flask having an internal volume of 1000 ml, and then the catalyst component-containing solution prepared above was added. The eggplant flask to which the carrier and the catalyst component-containing solution were added was set on a rotary evaporator, immersed in an 80 ° C. water bath and impregnated for 30 minutes. Thereafter, the mixture was evaporated with stirring under a reduced pressure of 0.05 MPa to remove excess water.

  Subsequently, the catalyst component-containing solution having the same composition as in the first impregnation step was added to the dried carrier, and the carrier was impregnated under the same conditions as in the first time and dried.

  Then, heat processing was performed at 400 degreeC for 20 minutes in the airflow using the hot air dryer. Furthermore, this was heat-processed at 550 degreeC for 3 hours in nitrogen atmosphere, and the catalyst (A-1) was obtained. The silver supporting rate of the catalyst (A-1) was 15.2% by mass, and the supporting rate of cesium was 0.15% by mass.

(Example 2)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 8 parts by mass of ethylenediamine and 77.3 parts by mass of water to 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate. The silver concentration of this solution was 10% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed twice by the same method as in Example 1 to obtain a catalyst (A-2). The silver supporting rate of the catalyst (A-2) was 15.3% by mass, and the supporting rate of cesium was 0.15% by mass. In addition, compared with Example 1, Example 2 has a low silver concentration of a catalyst component containing solution.

(Example 3)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 8 parts by mass of ethylenediamine and 176.7 parts by mass of water to 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate. The silver concentration of this solution was 5% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Next, impregnation-drying and calcination were performed twice by the same method as in Example 1 to obtain a catalyst (A-3). The silver supporting rate of the catalyst (A-3) was 15.2% by mass, and the supporting rate of cesium was 0.15% by mass. In Example 3, the silver concentration of the catalyst component-containing solution is lower than in Examples 1 and 2.

Example 4
To 9.3 parts by mass of silver oxalate and 0.1 part by mass of cesium nitrate, 5.3 parts by mass of ethylenediamine and 29.3 parts by mass of water were added and dissolved to prepare a catalyst component-containing solution in which silver and cesium coexisted. The silver concentration of this solution was 15% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed three times by the same method as in Example 1 to obtain a catalyst (A-4). The silver support rate of the catalyst (A-4) was 15.4% by mass, and the support rate of cesium was 0.15% by mass. Example 4 is different from Example 1 in that the impregnation step (including the drying step) is performed three times.

(Example 5)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 3.2 parts by mass of ethylenediamine and 17.6 parts by mass of water to 5.6 parts by mass of silver oxalate and 0.06 parts by mass of cesium nitrate. The silver concentration of this solution was 15% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed 5 times by the same method as in Example 1 to obtain a catalyst (A-5). The silver support rate of the catalyst (A-5) was 15.6% by mass, and the support rate of cesium was 0.15% by mass. In addition, Example 5 is different from Examples 1 and 4 in that the impregnation step (including the drying step) is performed five times.

(Example 6)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 5.3 parts by mass of ethylenediamine and 50.4 parts by mass of water to 9.3 parts by mass of silver oxalate and 0.1 parts by mass of cesium nitrate. The silver concentration of this solution was 10% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed three times by the same method as in Example 1 to obtain a catalyst (A-6). The silver supporting rate of the catalyst (A-6) was 15.3% by mass, and the supporting rate of cesium was 0.15% by mass. In Example 6, the silver concentration of the catalyst component-containing solution is the same as that in Example 2, but differs in that the impregnation step (including the drying step) is performed three times.

(Example 7)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 3.2 parts by mass of ethylenediamine and 30.9 parts by mass of water to 5.6 parts by mass of silver oxalate and 0.06 parts by mass of cesium nitrate. The silver concentration of this solution was 10% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed 5 times by the same method as in Example 1 to obtain a catalyst (A-7). The silver support rate of the catalyst (A-7) was 15.4% by mass, and the cesium support rate was 0.15% by mass. In Example 7, the silver concentration of the catalyst component-containing solution is the same as in Examples 2 and 6, but differs in that the impregnation step (including the drying step) is performed five times.

(Example 8)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 5.3 parts by mass of ethylenediamine and 117.4 parts by mass of water to 9.3 parts by mass of silver oxalate and 0.1 parts by mass of cesium nitrate. The silver concentration of this solution was 5% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed three times by the same method as in Example 1 to obtain a catalyst (A-8). The silver supporting rate of the catalyst (A-8) was 15.3% by mass, and the supporting rate of cesium was 0.15% by mass. In Example 8, the silver concentration of the catalyst component-containing solution is the same as that in Example 3, but differs in that the impregnation step (including the drying step) is performed three times.

Example 9
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 3.2 parts by mass of ethylenediamine and 70.5 parts by mass of water to 5.6 parts by mass of silver oxalate and 0.06 parts by mass of cesium nitrate. The silver concentration of this solution was 5% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed 5 times by the same method as in Example 1 to obtain a catalyst (A-9). The silver supporting rate of the catalyst (A-9) was 15.4% by mass, and the supporting rate of cesium was 0.15% by mass. In Example 9, the silver concentration of the catalyst component-containing solution is the same as in Examples 3 and 8, but differs in that the impregnation step (including the drying step) is performed five times.

(Comparative Example 1)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 8 parts by mass of ethylenediamine and 26.0 parts by mass of water to 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate. The silver concentration of this solution was 20.6% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Next, impregnation-drying and calcination were performed twice by the same method as in Example 1 to obtain a catalyst (B-1). The silver supporting rate of the catalyst (B-1) was 15.3% by mass, and the supporting rate of cesium was 0.14% by mass. Comparative Example 1 differs from the production method of the present invention in that the silver concentration of the catalyst component-containing solution is as high as 20.6% by mass.

(Comparative Example 2)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 18 parts by mass of ethylenediamine and 86.2 parts by mass of water to 28 parts by mass of silver oxalate and 0.3 parts by mass of cesium nitrate. The silver concentration of this solution was 15.0 mass%, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Next, impregnation-drying and firing were performed once by the same method as in Example 1 to obtain a catalyst (B-2). The silver support rate of the catalyst (B-2) was 15.1% by mass, and the support rate of cesium was 0.15% by mass. Comparative Example 2 differs from the production method of the present invention in that the impregnation step (including the drying step) is performed only once.

(Comparative Example 3: corresponding to the technique described in Patent Document 4)
34 parts by mass of ethylenediamine was added to 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate and dissolved to prepare a catalyst component-containing solution in which silver and cesium coexisted. The silver concentration of this solution was 20.6% by mass, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Subsequently, impregnation-drying and calcination were performed twice by the same method as in Example 1 to obtain a catalyst (B-3). The silver support rate of the catalyst (B-3) was 13.2% by mass, and the support rate of cesium was 0.12% by mass. Comparative Example 3 is different from the production method of the present invention in that the silver concentration of the catalyst component-containing solution is as high as 20.6% by mass and water is not included as the solvent of the catalyst component-containing solution.

(Comparative example 4: corresponding to the technique described in Patent Document 5)
A catalyst component-containing solution in which silver and cesium coexisted was prepared by adding 8 parts by mass of ethylenediamine and 44.1 parts by mass of water to 14 parts by mass of silver oxalate and 0.15 parts by mass of cesium nitrate. The silver concentration of this solution was 15.0 mass%, and the cesium concentration was 0.008 mol with respect to 1 mol of silver.

  Then, after the first impregnation step (including the drying step), in the same manner as in Example 1 described above, except that the metal silver was deposited on the support by heating at 300 ° C. for 30 minutes in air. Two impregnations-drying and calcination were performed to obtain a catalyst (B-4). That is, in this comparative example, the impregnation-drying-firing was performed twice. The silver support rate of the catalyst (B-4) was 15.0% by mass, and the support rate of cesium was 0.15% by mass.

(Evaluation example)
The catalysts (A-1) to (A-9) and the catalysts (B-1) to (B-4) obtained in Examples 1 to 9 and Comparative Examples 1 to 4 were pulverized, and 600 to 850 mesh. In each case, 1.2 g of each was filled in a stainless steel reaction tube having an inner diameter of 3 mm and a tube length of 600 mm, and ethylene gas phase oxidation reaction was performed under the following conditions. The reaction conditions used for the vapor phase oxidation of ethylene are as follows.

  The reaction temperature and ethylene oxide selectivity when the ethylene conversion is 10% are shown in the following Table 2 (results of the catalyst of the example) and Table 3 (results of the catalyst of the comparative example). In addition, the conversion rate and selectivity at the time of ethylene oxide manufacture are calculated according to the following formula 2 and formula 3, respectively.

  From the results shown in Table 2 and Table 3 above, the catalysts obtained in each Example can obtain higher selectivity even at a lower reaction temperature, compared with the catalysts obtained in each Comparative Example. Therefore, according to the present invention, a catalyst having excellent catalytic performance and capable of producing ethylene oxide with a high selectivity even at a lower reaction temperature (that is, high activity) can be provided. And according to the manufacturing method of ethylene oxide using the said catalyst, it becomes possible to manufacture ethylene oxide with high selectivity instead of reaction temperature, and the industrial utility value is very large from a viewpoint of economical efficiency.

Claims (5)

An impregnation step of impregnating a carrier containing alumina as a main component with a catalyst component-containing solution containing silver, an alkali metal, and water;
A firing step of firing the carrier after impregnation;
A method for producing an ethylene oxide production catalyst comprising:
In the impregnation step, the support is impregnated twice or more with the catalyst component-containing solution having a silver concentration of 1 to 15% by mass in terms of element ,
The method for producing a catalyst for producing ethylene oxide , wherein the firing step comprises two or more steps of firing . The manufacturing method of Claim 1 which performs a drying process after each impregnation operation in the said impregnation process. The production method according to claim 1, wherein the catalyst component-containing solution contains a complexing agent. Wherein the alkali metal is cesium, the content of cesium in the catalyst component-containing solution is 1 × ^{10 -3} ~20 × ¹⁰ -3 mol per mol of silver, any one of claims 1 to 3 The manufacturing method as described in. The manufacturing method of ethylene oxide which has the process of carrying out the gaseous-phase oxidation of ethylene with molecular oxygen containing gas in presence of the catalyst for ethylene oxide manufacture manufactured by the manufacturing method of any one of Claims 1-4 .