JP2013202592A - Catalyst for ethylene oxide production and method for production of ethylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve a performance of a catalyst for ethylene oxide production.SOLUTION: There is provided a method for producing a catalyst for ethylene oxide production, which is obtained by impregnating a solution containing silver and rhenium in an alumina carrier whose Si content rate is 0.1-4.5 wt.% by SiOconversion, Na content rate is 0.01-0.4 wt.% by NaO conversion and specific surface area is 0.5-3.0 m/g and performing heating at 275-450°C in an atmosphere containing 5-30% of oxygen, and in which the content rate of silver is 5.0-30.0 wt.%, and a silver surface area per gram of silver defined by expression (I): the silver surface area per gram of silver={catalyst specific surface area-carrier specific surface area×(1-silver content rate)}/silver content rate, is 0.5-7.0 m/g.

Description

  The present invention relates to a catalyst for producing ethylene oxide and a method for producing ethylene oxide.

A catalyst used when industrially producing ethylene oxide by vapor-phase catalytic oxidation of ethylene with molecular oxygen is a silver catalyst. In order to efficiently produce ethylene oxide, there is a strong demand for improvement of this silver catalyst, and various methods have been proposed in the past, and various studies have been conducted on catalyst preparation methods.
For example, Patent Document 1 describes a method in which a catalyst is brought into contact with a treatment material containing oxygen at a temperature of at least 350 ° C. for at least 5 minutes in order to develop high selectivity at an early stage. Patent Document 2 describes a method of heat treatment at 200 ° C. to 600 ° C. in an atmosphere containing 10 ppm by volume to 5% by volume of oxygen in order to improve catalyst performance (activity, selectivity, catalyst life). ing. Further, in Patent Document 3, in order to improve the activity, selectivity and stability of the catalyst, the atmosphere contains water vapor and oxygen, and the oxygen content is 0.2 vol% or more and 7 vol% or less. Among them, a method of firing at a temperature of 175 ° C. or higher and 400 ° C. or lower is described.

Special table 2009-525848 gazette Special table 2008-540098 gazette JP 2010-036104 A

  In ethylene oxide production, selectivity is a very important factor that determines plant economics. For example, increasing the selectivity by 1 percent can significantly reduce the annual operating cost of an ethylene oxide production plant. Therefore, even though various studies and improvements have been made so far, further improvement of the performance of the catalyst for producing ethylene oxide is desired.

  As a result of intensive studies to solve the above problems, the present inventors have impregnated a solution containing silver and rhenium into an alumina carrier containing a predetermined amount of Si and Na and having a specific surface area. By heating in an atmosphere containing a predetermined amount of oxygen, it becomes possible to manufacture a catalyst for ethylene oxide production containing a predetermined silver and having a predetermined silver surface area. The inventors have found that the selectivity to ethylene oxide is high and ethylene oxide can be produced efficiently, and the present invention has been achieved.

That is, the gist of the present invention resides in the following [1] to [5].
[1] silver, a solution containing the rhenium, Si content of from 0.1 to 4.5 wt% in terms of SiO _2, 0.01 to 0.4 wt% Na content in terms of Na ₂ O It is obtained by impregnating an alumina carrier having a specific surface area of 0.5 to 3.0 m ² / g and heating at 275 to 450 ° C. in an atmosphere containing 5 to 30% oxygen. Ethylene oxide, wherein the content is 5.0 to 30.0% by weight, and the silver surface area per 1 g of silver defined by the following formula (I) is 0.5 to 7.0 m ² / g A method for producing a catalyst for production.

(I) Silver surface area per 1 g of silver = {catalyst specific surface area−support specific surface area × (1−silver content)} / silver content
[2] The process for producing a catalyst for ethylene oxide production according to [1], wherein the time for heating at 275 to 450 ° C. in an atmosphere containing 5 to 30% oxygen is 1 to 50 hours.
[3] The method for producing an ethylene oxide production catalyst according to [1] or [2], wherein the alumina support is washed in advance before impregnation with silver or rhenium, or an alkali metal is previously supported on the alumina support. .

[4] The alumina support impregnated with a solution containing silver and rhenium is heated at 100 to 250 ° C. in advance before being heated at 275 to 450 ° C. in an oxygen-containing atmosphere. [3] The method for producing a catalyst for producing ethylene oxide according to any one of [3].
[5] A method for producing ethylene oxide using a catalyst for producing ethylene oxide produced by the production method according to any one of [1] to [4].

  When ethylene oxide is produced using the ethylene oxide production catalyst produced according to the present invention, ethylene oxide can be produced with high selectivity.

Embodiments of the present invention will be described in detail below. However, the description of the constituent elements described below is an example of embodiments of the present invention, and the present invention is limited to the following contents as long as the gist thereof is not exceeded. Not.
In the present invention, a solution containing silver and rhenium has a Si content of 0.1 to 4.5 wt% in terms of SiO ₂ and a Na content of 0.01 to 0.4 wt in terms of Na ₂ O. Is obtained by impregnating an alumina carrier having a specific surface area of 0.5 to 3.0 m ² / g and heating at 275 to 450 ° C. in an atmosphere containing 5 to 30% oxygen. Of the catalyst for ethylene oxide manufacture whose content rate of 5.0-30.0 weight% and the silver surface area per 1g of silver defined by following formula (I) are 0.5-7.0m < ² > / g. Is the method.

(I) Silver surface area per 1 g of silver = {catalyst specific surface area−support specific surface area × (1−silver content)} / silver content (catalyst component)
The catalyst component used for the ethylene oxide production catalyst in the present invention contains silver as a main component, and rhenium is an essential component in addition to this silver. Catalyst components include silver, rhenium, nitrogen, sulfur, phosphorus, boron, fluorine, alkali metals, alkaline earth metals, molybdenum, tungsten, chromium, titanium, hafnium, zirconium, vanadium, thallium, thorium, tantalum Niobium, gallium, and germanium are preferably included. Each of these may be used alone or in combination of two or more.

Here, a main component is a component contained most with respect to a catalyst component in a catalyst component.
The silver content with respect to the total catalyst for ethylene oxide production is 5.0 to 30.0% by weight, preferably 8.0 to 20.0% by weight from the viewpoints of effect and economy, and 10.0 to 15.0. Weight percent is more preferred.

Examples of the compound that provides silver include various compounds such as silver oxide, silver nitrate, silver carbonate, and silver oxalate. Among these, silver oxalate is particularly preferable.
The rhenium content in the ethylene oxide production catalyst is preferably 100 to 1000 ppm by weight, more preferably 200 to 800 ppm by weight. If the rhenium content is too small, a sufficient selectivity tends to be difficult to obtain, whereas if the rhenium content is too high, the activity of the catalyst tends to decrease.

Examples of the compound that provides rhenium include perrhenic acid compounds, rhenium oxide, rhenium chloride, and the like. Among these, ammonium perrhenate is preferable.
Examples of the alkali metal include lithium, potassium, rubidium and cesium, preferably cesium, more preferably a combination of cesium and lithium. The content of cesium with respect to the entire catalyst for producing ethylene oxide is preferably 100 to 10,000 ppm by weight, more preferably 250 to 3000 ppm by weight, and still more preferably 500 to 1500 ppm by weight. The lithium content relative to the total ethylene oxide production catalyst is preferably 10 to 10,000 ppm by weight, more preferably 100 to 1,000 ppm by weight, and most preferably 200 to 700 ppm by weight.

Examples of the compound that provides the alkali metal include various compounds such as hydroxide, nitrate, carbonate, acetate, chloride, oxide, and oxalate. Among these, hydroxide and nitrate are preferable.
In addition, a part of the alkali metal or a compound thereof may be supported by a carrier treatment as described later before impregnating the catalyst component.

(Catalyst component solution)
When the catalyst component is supported on the carrier, the catalyst component is dissolved in an appropriate solvent in which each component can be dissolved to obtain a catalyst component solution. Examples of the solvent include water or alcohols such as methanol and ethanol, and water is preferable because of easy handling. Further, a mixed solution of water and alcohols may be used.

In the catalyst component solution, the higher the silver concentration in the solution, the higher the silver content when the carrier is impregnated, which is preferable. Therefore, a complex forming agent is used so that the silver component can be dissolved in the solvent at a high concentration. The complex-forming agent reacts with silver to form a complex that is easily dissolved in the solvent.
Examples of such a complex-forming agent include nitrogen-containing compounds. Specific examples of the nitrogen-containing compound include C1-C6 monoamines such as ethylamine and butylamine, C1-C6 alkanolamines such as ethanolamine, ethylenediamine, 1,3-propanediamine and the like. 6 polyamines, ammonia, pyridine, and acetonitrile. Among these, ammonia, pyridine, polyamines having 1 to 6 carbon atoms, and monoamines having 1 to 6 carbon atoms are preferable, and ethylenediamine, 1,3-propanediamine, or these What mixed 2 types is more preferable.

(Porous carrier)
Examples of the carrier for supporting the catalyst component include a porous carrier. Examples of the porous carrier include alumina such as α-alumina, and porous refractories such as silicon carbide, titania, zirconia, and magnesia. Among these, alumina whose main component is α-alumina is preferable. Further, the alumina is Si component in terms of SiO _2, it is usually contain 0.1 to 4.5 wt%. The porous carrier usually contains 0.01 to 0.4% by weight of Na component in terms of Na ₂ O.

The support may have a great influence on the catalytic activity of the resulting catalyst depending on its physical properties. The specific surface area of the carrier is usually 0.5~3.0m ² / g, preferably from ^{1.0~2.5m 2 / g, 1.0~1.5m 2 /} g is more preferable. If the specific surface area of the support is too small, the supported silver particles become too large, and the activity may be reduced. On the other hand, if the size is too large, the pore diameter of the support becomes small, which is disadvantageous in terms of mass transfer and heat dissipation, and the catalyst performance may be reduced.

Further, the water absorption rate of the carrier is preferably 20 to 60%, more preferably 25 to 50%, from the viewpoint of facilitating the impregnation operation of the catalyst component. If the absorption rate of the carrier is too small, the amount of silver that can be supported by a single impregnation operation decreases, and the target silver content may not be achieved. On the other hand, if it is larger than the above range, the strength of the carrier may be lowered.
A method for preparing a carrier satisfying these characteristics is not particularly limited, and examples thereof include the following preparation methods. The main raw material powder, the Si component-containing compound, the pore-forming agent, and the like are mixed with an appropriate amount of water, and then the mixture is formed into a predetermined shape by extrusion or the like and then fired in an air atmosphere.

For example, in the case of an α-alumina carrier, a low soda alumina powder can be used as the main raw material powder. The pore-forming agent burns and removes from the carrier by firing in an air atmosphere to give controlled pores to the carrier. However, when the firing temperature is too high, the specific surface area of the carrier tends to decrease. The Si content and the Na content in the carrier can be adjusted by the blending ratio of the raw materials used for the carrier preparation. The larger the blending ratio, the higher the content. For example, the Si content can be increased by increasing the blending ratio of the Si component-containing compound.

(Carrier treatment)
The support may be first impregnated with the catalyst component solution, but before impregnating the catalyst component solution, the support is loaded with an alkali metal that is a part of the catalyst component, or deionized water is used to support the support. It is preferable to carry out carrier treatment such as washing, which leads to improvement in the performance of the catalyst.
Examples of the alkali metal used in the carrier treatment include lithium and cesium. Each of these metals may be used alone or in combination of two.

  Examples of the compound for providing lithium and cesium used in the carrier treatment include a lithium compound and a cesium compound. These compounds are preferably those having low solubility in the catalyst component solution so as not to re-elut when the support is impregnated with the catalyst component solution. Specifically, both the lithium compound and the cesium compound are preferably carbonates. Moreover, as a solvent which melt | dissolves a lithium compound and a cesium compound, water is preferable from the ease of handling.

The deionized water used for the carrier washing is 0 to 100 ° C, preferably 60 to 100 ° C, more preferably 80 to 100 ° C. The weight of deionized water used per carrier washing is preferably equal to or more than the carrier weight, more preferably 2 times or more, and more preferably 3 times or more. The carrier washing is preferably 3 times or more, more preferably 5 times or more than once.
After carrying out the carrier treatment, the carrier is taken out from the excess lithium compound, cesium compound-containing solution, or deionized water, and then subjected to drying treatment such as reduced pressure drying or heat treatment. The heat treatment temperature is 100 to 300 ° C, preferably 100 to 250 ° C, more preferably 110 to 220 ° C. The heating atmosphere can be air, superheated steam, nitrogen, argon, krypton, helium, and combinations thereof, but superheated steam is preferred.

Next, the catalyst component solution is impregnated into the carrier or the carrier subjected to the carrier treatment, and heated in an oxygen-containing atmosphere to obtain a catalyst.
(Catalyst component impregnation)
Examples of the catalyst component impregnation step include a method of immersing the catalyst component solution in a carrier or a carrier subjected to carrier treatment, and a method of spraying. Furthermore, it is also possible to combine a decompression process as needed. By this catalyst component impregnation step, a catalyst component-impregnated support is obtained.

(Oxygen-containing atmosphere heating process)
The support impregnated with the catalyst component solution is usually heated at 275 to 450 ° C. in an oxygen-containing atmosphere to change the silver compound to metallic silver, thereby obtaining a catalyst for producing ethylene oxide. The heating in the oxygen-containing atmosphere is preferably 335 ° C. or higher from the viewpoint of ethylene oxide selectivity and 385 ° C. or lower from the economical viewpoint. As a result, the metallic silver containing the catalyst component of silver and rhenium has a silver surface area per 1 g of silver defined by the following formula (I), usually 0.5 to 7.0 m ² / g, and the ethylene oxide selectivity is Get higher. Silver surface area per silver 1g is 1.0~6.0m ² / g are preferred, 1.5~6.0m ² / g is more preferable. The catalyst specific surface area and the support specific surface area can be measured by the BET method.

(I) Silver surface area per gram of silver = {catalyst specific surface area−support specific surface area × (1−silver content)} / silver content The oxygen-containing atmosphere only needs to contain 5 to 30% of oxygen, and the rest Is nitrogen, argon, helium, carbon dioxide, or a mixture thereof. The oxygen concentration in the oxygen-containing atmosphere is preferably 15 to 25%. For the oxygen-containing atmosphere, it is optimal to use air for simplicity.

  The heat treatment time in the oxygen-containing atmosphere is preferably 1 to 50 hours. From the viewpoint of ethylene oxide selectivity, 1.2 hours or more is more preferable, and 2.2 hours or more is more preferable. From the economical viewpoint, it is preferably within 20 hours, more preferably within 10 hours, and most preferably within 5 hours. The heating time is the total time held at a certain target temperature. However, when the target temperature is set to a lower limit temperature of 275 ° C. and an upper limit temperature of about 450 ° C. in the oxygen-containing atmosphere, the time below the lower limit temperature and the upper limit temperature is preferably 5 minutes or less, and further 3 minutes or less. is there.

As an apparatus used in the heating process, a general electric furnace such as a muffle furnace can be used. Industrially, roller hearth kiln is appropriate from the viewpoint of continuous production.
(Preheating)
The carrier impregnated with the catalyst component generates a vapor of a nitrogen-containing compound used as a silver complexing agent at the initial stage of the heating step. In order to prevent the mixed gas of the nitrogen-containing compound vapor and the oxygen-containing atmosphere from entering the combustion range, it is preferably held in advance in an oxygen-containing atmosphere or an inert gas atmosphere at 275 ° C. or lower for 5 to 60 minutes. The inert gas atmosphere is an atmosphere that does not substantially contain oxygen, for example, an atmosphere having an oxygen concentration of less than 5%. As the inert gas atmosphere, superheated steam is particularly preferable. The preheating temperature is particularly preferably 100 to 250 ° C. The preheating time is particularly preferably 10 to 30 minutes. It is also possible to continuously perform the oxygen-containing atmosphere heating step without cooling after the preheating.

(Ethylene oxide production)
The reaction for converting ethylene to ethylene oxide using the ethylene oxide production catalyst of the present invention can be carried out by a generally known method. Generally, the reaction pressure is 0 to 4 MPa (gauge pressure), and the reaction temperature is 180 to 350 ° C. The composition of the raw material gas is an inert gas such as methane, nitrogen, carbon dioxide, and argon as a diluent in a mixed gas of 1 to 40% by volume of ethylene and 1 to 20% by volume of oxygen. Air or industrial oxygen is used as the oxygen source. Further, by adding 0.1 to 50 ppm by volume of halogenated hydrocarbon as a reaction modifier, formation of hot spots in the catalyst is prevented, and catalyst performance, particularly catalyst selectivity, is greatly improved.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example, unless the summary is exceeded.
In the following, the physical properties and characteristics of the support and the catalyst were evaluated by the following methods.
(Measurement of carrier composition)
The Si contents of the carriers A and B shown in Table 1 were measured by ICP emission method after sodium carbonate and boric acid were added and melted by heating, extracted with hydrochloric acid. On the other hand, the Na content was extracted with sulfuric acid, phosphoric acid and hydrofluoric acid and measured by atomic absorption. The Si content and Na content of the carrier C were measured by the fluorescent X-ray method.

The water absorption rates of the carriers A, B and C shown in Table 1 were measured by a method based on JIS R2205.
(Measurement of catalyst composition)
The silver content was measured by extracting the silver with nitric acid and measuring the potential difference. The contents of cesium, rhenium, and lithium were measured by extracting the above components with nitric acid, cesium and lithium with an atomic absorption method, and rhenium with an ICP emission method.

(Measurement of catalyst specific surface area and support specific surface area)
Sample that has been pretreated (250 ° C., nitrogen gas flow for 15 minutes) was used with a MOTTEC, Macsorb HM Model-1201, BET 1 point method (adsorption gas: nitrogen)
The specific surface area of the catalyst and the specific surface area of the support were measured.
(Calculation of silver surface area per gram of silver)
Using the catalyst specific surface area, the support specific surface area, and the silver content, the silver surface area per 1 g of silver was determined by the following formula (I).

  (I) Silver surface area per 1 g of silver = {catalyst specific surface area−support specific surface area × (1−silver content)} / silver content

(Catalyst performance)
The composition of the source gas and product gas was analyzed by gas chromatography. The selectivity for ethylene oxide was expressed as the ratio of the number of moles of ethylene oxide produced to the number of moles of ethylene consumed. The reaction temperature was adjusted so that 1 L of catalyst and ethylene oxide production amount (STY) per hour became a target value.

[Example 1]
(Carrier treatment)
2000 g of carrier A shown in Table 1 was immersed in 6000 ml of boiling deionized water for 20 minutes, the carrier was taken out from the deionized water, and the carrier was washed. This operation was repeated, and the carrier was washed 5 times in total. Subsequently, this carrier was heated and dried with superheated steam at 150 ° C. for 20 minutes at a flow rate of 2 m / sec to obtain 2000 g of a washing carrier. This operation was performed 6 times to obtain 12000 g of washing carrier A.

(Preparation of catalyst component solution)
2590 g of silver nitrate (AgNO ₃ ) was dissolved in 9200 ml of deionized water, and the temperature was adjusted to 50 ° C. To this silver nitrate aqueous solution, an aqueous sodium hydroxide solution (633 g of sodium hydroxide, 3570 ml of deionized water) maintained at 50 ° C. was added dropwise to obtain a silver hydroxide precipitate. The supernatant was replaced, and the silver hydroxide was washed until the pH of the supernatant was 10 or less and the conductivity was 45 μΩ / cm or less. To the silver hydroxide precipitate, 2300 ml of deionized water and 960 g of oxalic acid dihydrate were added, and the pH became 8.0. During the addition of oxalic acid dihydrate, the temperature was adjusted to 50 ° C. or lower. A silver oxalate precipitate was thus obtained. The precipitate was filtered off and washed with deionized water to obtain a silver oxalate slurry (water content 21.4% by weight). The silver oxalate slurry 2949.9 g thus obtained was gradually added and dissolved in an aqueous solution consisting of 826 g of ethylenediamine, 226 g of 1,3-diaminopropane and 960 g of water to prepare a silver complex solution. The specific gravity of this silver complex solution was 1.65 g / ml.

To the obtained silver complex solution, 100 ml of an aqueous solution having a cesium hydroxide monohydrate (CsOH.H ₂ O) concentration of 11.7% by weight and an aqueous solution having an ammonium perrhenate (NH ₄ ReO ₄ ) concentration of 6.8% by weight 100 ml, 230 ml of an aqueous solution having a lithium hydroxide monohydrate (LiOH.H ₂ O) concentration of 12.0% by weight, and 480 ml of deionized water were added to obtain a catalyst component-containing solution.
(Preparation of catalyst component impregnated carrier)
The catalyst component solution thus obtained was impregnated by heating to 40 ° C. under reduced pressure in an evaporator with 12,000 g of the above washing carrier A.

(Preheating of catalyst component impregnated carrier)
The catalyst component-impregnated support was calcined in superheated steam at 200 ° C. for 20 minutes at a flow rate of 2 m / sec to obtain a catalyst precursor.
(Oxygen-containing atmosphere heating process)
The obtained catalyst precursor was then heated in a heating furnace at 300 ° C. for 2.5 hours under an air atmosphere, and then cooled to room temperature to obtain a catalyst. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the obtained catalyst were 12.0 wt%, 770 wtppm, 370 wtppm, and 380 wtppm, respectively. The silver surface area per 1 g of silver was 2.4 m ² / g.

(Manufacture of ethylene oxide)
12.7 L of the catalyst prepared as described above was charged into a carbon steel reaction tube having an inner diameter of about 40 mm, and a reaction gas (ethylene 30% by volume, oxygen 8.0% by volume, carbon dioxide 3.0% by volume, remaining nitrogen) At a pressure of 1.8 MPa (gauge pressure). As a reaction modifier, a chlorine compound having 1 to 3 carbon atoms such as vinyl chloride was added to the reaction gas. The concentration of the reaction modifier was adjusted so as to maximize the ethylene oxide selectivity. The reaction temperature was adjusted so that the amount of ethylene oxide produced per hour (STY) of the catalyst was 0.19 kg-EO / L-cat · h (reaction condition A). The reaction results are shown in Table 2.

[Comparative Example 1]
(Carrier treatment)
In the same manner as in Example 1, carrier A was subjected to carrier treatment, and carrier A 120 subjected to carrier treatment was used.
00 g was obtained.
(Preparation of catalyst component solution)
Silver nitrate (AgNO ₃ ) 2590 g and potassium oxalate monohydrate (K ₂ C ₂ O ₄ .H ₂
O) 1540 g was dissolved in 11.5 L and 13 L of water, respectively, and then gradually mixed while heating to 60 ° C. in a hot water bath to obtain a white precipitate of silver oxalate (AgC ₂ O ₄ ). . The precipitate was collected by filtration and then washed with deionized water to obtain a silver oxalate slurry (water content 18.7% by weight). The silver oxalate slurry 2949.9 g thus obtained was gradually added and dissolved in an aqueous solution consisting of 826 g of ethylenediamine, 226 g of 1,3-diaminopropane and 960 g of water to prepare a silver complex solution. The specific gravity of this silver complex solution was 1.65 g / ml.

To the obtained silver complex solution, 100 ml of an aqueous solution with a cesium nitrate (CsNO ₃ ) concentration of 13.3% by weight, 100 ml of an aqueous solution with an ammonium perrhenate (NH ₄ ReO ₄ ) concentration of 6.8 wt%, lithium nitrate (LiNO ₃ ) 100 ml of an aqueous solution having a concentration of 34.0% by weight and 760 ml of deionized water were added to obtain a catalyst component-containing solution.
A catalyst precursor was obtained in the same manner as in Example 1 except that the obtained catalyst component solution was used.

(Oxygen-containing atmosphere heating process)
The catalyst precursor was then heated in an oven at 250 ° C. for 1.0 hour in an air atmosphere, and then cooled to room temperature to obtain a catalyst. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the obtained catalyst were 12.2 wt%, 810 wtppm, 400 wtppm, and 390 wtppm, respectively. Moreover, the silver surface area per 1g of silver was 0.4m < ² > / g. The results of producing ethylene oxide in the same manner as in Example 1 are shown in Table 2.

[Comparative Example 2]
A catalyst (catalyst precursor) was produced in the same manner as in Comparative Example 1 except that the carrier B was used as the carrier and the oxygen-containing atmosphere heating step was not performed, and the reaction was evaluated. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the catalyst precursor were 11.7 wt%, 740 wt ppm, 340 wt ppm, and 350 wt ppm, respectively. The silver surface area per gram of silver was 4.4 m ² / g. The results of producing ethylene oxide in the same manner as in Example 1 are shown in Table 2.

From Table 2 that Comparative Example was heated in an air atmosphere at 300 ° C., in the first embodiment the silver surface area was 2.4 m ² / g, the silver surface area heated under air atmosphere 250 ° C. is 0.4 m ² / g 1. It turns out that ethylene oxide selectivity is high compared with the comparative example 2 which did not implement oxygen-containing atmosphere heating but the silver surface area became 4.4 m < ² > / g.
[Example 2]
The same catalyst as in Example 1 was crushed to 6 to 10 mesh, and 3 ml of the catalyst was filled into a SUS reaction tube having an inner diameter of 7.5 mm, and reaction gas (ethylene 30 vol%, oxygen 8.5 vol%, carbon dioxide 3
. 0% by volume, remaining nitrogen) was flowed with GHSV 4300 hr-1, pressure 0.7 MPa gauge. Further, vinyl chloride was added to the reaction gas as a reaction modifier. The concentration of the reaction modifier was adjusted so as to maximize the ethylene oxide selectivity. The reaction temperature was adjusted so that the amount of ethylene oxide produced per hour (STY) of the catalyst was 0.2 kg-EO / L-cat · h (reaction condition B). The reaction results are shown in Table 3.

[Example 3]
(Carrier treatment)
100 g of support A shown in Table 1 was immersed in 200 ml of an aqueous solution in which 0.08 g of cesium carbonate (Cs ₂ CO ₃ ) and 1.67 g of lithium carbonate (Li ₂ CO ₃ ) were dissolved, and then the excess liquid was cut off. This was heated and dried with superheated steam at 150 ° C. for 15 minutes at a flow rate of 2 m / sec to carry lithium and cesium components.

(Preparation of catalyst component solution)
A silver complex solution was prepared in the same manner as in Comparative Example 1. The specific gravity of this silver complex solution was 1.64 g / ml.
To 12.0 g of the obtained silver complex solution, 0.6 ml of an aqueous solution having a cesium nitrate (CsNO ₃ ) concentration of 5.5% by weight, and 0.6 ml of an aqueous solution having an ammonium perrhenate (NH ₄ ReO ₄ ) concentration of 3.0% by weight. And 1.3 ml of deionized water were added to obtain a catalyst component-containing solution.

(Preparation of catalyst component impregnated carrier)
The obtained catalyst component solution was impregnated by heating at 40 ° C. under reduced pressure in an evaporator with 30 g of the carrier treated as described above.
(Preheating)
The catalyst component-impregnated support was calcined in superheated steam at 200 ° C. for 15 minutes at a flow rate of 2 m / second to obtain a catalyst precursor. The silver surface area per gram of silver was 8.3 m ² / g.

(Oxygen-containing atmosphere heating process)
The obtained catalyst precursor was then heated in an oven at 370 ° C. for 4.0 hours in a heating furnace, and then cooled to room temperature to obtain a catalyst. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the obtained catalyst were 11.6 wt%, 780 wtppm, 360 wtppm, and 410 wtppm, respectively. Moreover, the silver surface area per 1g of silver was 3.5m < ² > / g. Silver surface area was decreased from 8.3 m ² / g to 3.5 m ² / g by the heating step. The results of producing ethylene oxide in the same manner as in Example 2 are shown in Table 3.

[Comparative Example 3]
A catalyst was produced in the same manner as in Example 3 except that the oxygen-containing atmosphere heating was not performed to obtain a catalyst precursor. The silver surface area per gram of silver was 8.3 m ² / g. Reaction evaluation was performed using this. The reaction results are shown in Table 3.
[Example 4]
Except that the carrier C shown in Table 1 was used as the carrier, and that cesium carbonate (Cs ₂ CO ₃ ) and lithium carbonate (Li ₂ CO ₃ ) used in the carrier pretreatment were 0.23 g and 2.33 g, respectively. Prepared a catalyst in the same manner as in Example 3 and heated in an oxygen-containing atmosphere to obtain a catalyst. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the obtained catalyst were 11.8 wt%, 1000 wtppm, 360 wtppm, and 650 wtppm, respectively. The silver surface area per gram of silver was 4.4 m ² / g. The results of producing ethylene oxide in the same manner as in Example 2 are shown in Table 3.

[Example 5]
(Carrier treatment)
The carrier A was washed by immersing 100 g of carrier A shown in Table 1 in 300 ml of boiling deionized water for 20 minutes. Subsequently, the support | carrier was removed and it immersed in 300 ml boiling water for another 20 minutes. This procedure was performed a total of 5 times to separate the water from the support, which was then heat dried with superheated steam at 150 ° C. for 15 minutes at a flow rate of 2 m / sec.

(Preparation of catalyst component solution)
A silver complex solution was prepared in the same manner as in Example 1. The specific gravity of this silver complex solution was 1.62 g / ml.
To 12.1 g of the obtained silver complex solution, 0.6 ml of an aqueous solution containing 5.5% by weight of cesium hydroxide monohydrate (CsOH.H ₂ O), ammonium perrhenate (NH ₄ ReO ₄ ) concentration of 3
. Add 0.6 ml of 0% by weight aqueous solution, 0.6 ml of lithium hydroxide monohydrate (LiOH.H ₂ O) concentration of 13.1% by weight, and 1.3 ml of deionized water, and contain silver components A solution was obtained.

Preparation of the catalyst component-impregnated support using the catalyst component solution and preheating of the catalyst component-impregnated support were performed in the same manner as in Example 3. The oxygen-containing atmosphere heating step was performed in the same manner as in Example 3 except that the heating time was 2.0 hours to obtain a catalyst. The contents of silver, cesium, rhenium, and lithium (catalyst standard) in the obtained catalyst were 12.0 wt%, 770 wtppm, 360 wtppm, and 410 wtppm, respectively. The silver surface area per gram of silver was 2.6 m ² / g. The results of producing ethylene oxide in the same manner as in Example 2 are shown in Table 3.

From Table 3, Example 2 (catalyst similar to Example 1) heated at 300 ° C. in an air atmosphere and having a silver surface area of 2.4 m ² / g did not perform oxygen-containing atmosphere heating and had a silver surface area of 8 It can be seen that the ethylene oxide selectivity is higher than that of Comparative Example 3 which is .3 m ² / g. Also in the reaction condition B, the same effect as in the reaction condition A (Table 2) is confirmed. On the other hand, was heated under 370 ° C. air atmosphere, silver surface area in Embodiment 3-5 is 2.6~4.4m ² / g, the silver surface area without performing an oxygen-containing atmosphere heating 8.3 m ² / g Compared with Comparative Example 3 that was, the ethylene oxide selectivity was high. When heated at 370 ° C. in an air atmosphere, the heating time is 4.0 hours, and in Examples 3 and 4 supporting Li and Cs as the carrier treatment, the heating time is 2.0 hours compared to Example 5 where the heating time is 2.0 hours. The selectivity was high.

Claims (5)

Silver, a solution containing the rhenium, Si content of from 0.1 to 4.5 wt% in terms of SiO _2, Na content of from 0.01 to 0.4 wt% in terms of Na ₂ O, The silver content obtained by impregnating an alumina carrier having a specific surface area of 0.5 to 3.0 m ² / g and heating at 275 to 450 ° C. in an atmosphere containing 5 to 30% oxygen. A catalyst for ethylene oxide production, characterized in that it is 5.0 to 30.0% by weight, and the silver surface area per 1 g of silver defined by the following formula (I) is 0.5 to 7.0 m ² / g. Manufacturing method.
(I) Silver surface area per 1 g of silver = {catalyst specific surface area−support specific surface area × (1−silver content)} / silver content   The method for producing an ethylene oxide production catalyst according to claim 1, wherein the time for heating at 275 to 450 ° C in an atmosphere containing 5 to 30% oxygen is 1 to 50 hours.   The method for producing an ethylene oxide production catalyst according to claim 1 or 2, wherein the alumina support is washed in advance before impregnation with silver or rhenium, or an alkali metal is supported on the alumina support in advance.   The alumina carrier impregnated with a solution containing silver and rhenium is heated at 100 to 250 ° C in advance before being heated at 275 to 450 ° C in an oxygen-containing atmosphere. 2. A process for producing a catalyst for producing ethylene oxide according to item 1.   The manufacturing method of ethylene oxide by the catalyst for ethylene oxide manufacture manufactured by the manufacturing method of any one of Claims 1-4.