JP2016165696A - Ethylene oxide production catalyst and method for producing ethylene oxide using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylene oxide production catalyst in which stability of catalyst performance is improved and good reaction characteristics are obtained over a long period from the initial reaction stage without accompanying an extreme increase in the reaction temperature.SOLUTION: Provided is an ethylene oxide production catalyst comprising a carrier, silver and rhenium, in which the carrier contains therein silicon in an amount of 0.01 wt.% to 1.0 wt.% in terms of SiO, and the carrier has, in a pore distribution measured by mercury press-in method, at least two peaks having a maximal value of log differential pore volume of 0.2 ml/g or more in a range of pore diameter of 0.01 μm to 100 μm, where at least one of the peaks is present in a range of 0.5 μm to 3.0 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a catalyst for producing ethylene oxide from ethylene and a method for producing ethylene oxide using the same.

  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 the appearance of a catalyst that maintains high selectivity continuously from the beginning of the reaction is desired. For this reason, various studies have been made conventionally.

  For example, Patent Document 1 describes a catalyst in which silver is supported on a carrier having a specific surface area and a specific pore size distribution. Patent Document 2 describes a catalyst carrier having a specific surface area, a specific water absorption rate, and a specific pore size distribution. Patent Document 3 describes a catalyst comprising a support having at least two peaks in the pore distribution. Patent Document 4 describes a catalyst carrier having a specific pore volume. Furthermore, Patent Document 5 describes a catalyst containing a carrier having a bimodal pore size distribution and a catalyst component such as silver or rhenium.

Special table 2008-545533 Special table 2005-518275 gazette JP 2008-86877 A Special table 2010-537807 Special table 2010-537993 gazette

However, the catalyst obtained by the prior art has a decrease in the catalyst performance when the reaction is continued for a long time even if the catalyst performance is good at the beginning of the reaction.
Although attempts have been made to increase the reaction temperature in order to compensate for the catalyst performance, the increase in temperature deteriorates the thermal efficiency and shortens the catalyst life.

  The present invention solves the above-mentioned conventional problems, and provides a catalyst for producing ethylene oxide that can improve the stability of catalyst performance and can obtain good reaction characteristics for a long period of time from the beginning of the reaction without causing an extreme increase in the reaction temperature. The purpose is to do.

As a result of repeated research, the present inventors have found that in a catalyst for producing ethylene oxide containing support, silver and rhenium, the support contains a specific amount of silicon in the support, and there are at least two peaks of log differential pore volume. The above problems have been solved by using a catalyst for producing ethylene oxide, which is a carrier in which at least one of the peaks is in a specific range.
That is, the gist of the present invention resides in the following [1] to [5].
[1] A catalyst for producing ethylene oxide containing a carrier, silver and rhenium,
The carrier contains 0.01% to 1.0% by weight of silicon in terms of SiO _{2 in the} carrier, and in the pore distribution measured by the mercury intrusion method, the log has a diameter in the range of 0.01 μm to 100 μm. A catalyst for producing ethylene oxide, wherein at least two peaks having a maximum value of the differential pore volume of 0.2 ml / g or more are present, and at least one of the peaks is in a range of 0.5 µm to 3.0 µm.

[2] The specific surface area of the carrier is 0.8m ² /g~1.8m ² / g, a catalyst for production of ethylene oxide according to [1].
[3] The catalyst for producing ethylene oxide according to [1] or [2], wherein the carrier has a water absorption rate of 40% by weight to 70% by weight.
[4] The catalyst for producing ethylene oxide according to any one of [1] to [3], wherein the carrier further contains sodium, and the sodium content in the carrier is 10 ppm by weight to 1500 ppm by weight in terms of Na ₂ O.

[5] A method for producing ethylene oxide, wherein ethylene is oxidized to ethylene oxide in the presence of the ethylene oxide production catalyst according to any one of [1] to [4].

  When ethylene oxide is produced from ethylene using the catalyst for producing ethylene oxide according to the present invention, reduction in catalyst performance is suppressed, and ethylene oxide is produced with high selectivity without causing an extreme temperature rise for a long period of time from the beginning of the reaction. Can do.

2 is a graph showing the pore distribution (log differential pore volume) of carrier A used in Example 1. FIG. 2 is a graph showing the pore distribution (cumulative pore volume) of the carrier A used in Example 1. FIG. 6 is a graph showing the pore distribution (log differential pore volume) of the carrier B used in Comparative Example 1. 6 is a graph showing the pore distribution (cumulative pore volume) of the carrier B used in Comparative Example 1.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention is an invention of an ethylene oxide production catalyst for producing ethylene oxide from ethylene and an ethylene oxide production method using the same.

(Carrier)
The carrier contained in the catalyst for producing ethylene oxide (hereinafter sometimes referred to as “catalyst”) of the present invention is a carrier for carrying a catalyst component for producing ethylene oxide from ethylene, and a porous carrier is preferred. Examples of the porous carrier include porous refractories such as alumina, silicon carbide, titania, zirconia, and magnesia. Among these, it is preferable to contain alumina, and it is more preferable to include α-alumina.

  The carrier is manufactured by firing a raw material containing a ceramic component. This ceramic component includes an alumina raw powder having an α-alumina structure (hereinafter sometimes simply referred to as “alumina raw powder”), an α-alumina precursor, and the like. The alumina raw powder having the α-alumina structure refers to α-alumina powder that retains the α-alumina structure even after sintering. The precursor of α-alumina refers to a material that becomes α-alumina upon firing, and examples thereof include alumina hydrates.

  The alumina raw powder having the α-alumina structure (alumina raw powder) contains an alumina raw powder having a specific α-alumina structure (hereinafter sometimes referred to as “specific alumina raw powder”).

  The specific alumina raw powder is preferably contained in an amount of 50% by weight or more, more preferably 70% by weight or more, and more preferably 80% by weight or more based on the whole alumina raw powder having the α-alumina structure. The content is preferably 90% by weight or more. If it is less than 50% by weight, there may be a problem that the obtained support or catalyst does not have an industrially usable crushing strength. On the other hand, since the total amount of the ceramic component contained in the raw material may be the alumina raw powder, the upper limit of the content ratio is 100% by weight.

  Moreover, the average particle diameter of the secondary particles in which the primary particles of the specific alumina raw powder are aggregated is preferably 1.0 μm or more, and more preferably 1.5 μm or more. If it is smaller than 1.0 μm, fine pores exist in the obtained carrier, and there may be a problem that sufficient mechanical strength for industrial use cannot be obtained. On the other hand, the upper limit of the average particle diameter is preferably 10 μm, more preferably 7.5 μm. If it is larger than 10 μm, the obtained carrier may cause a problem that sufficient mechanical strength for industrial use cannot be obtained.

  In the raw material, it is preferable to contain an organic substance such as cellulose, walnut, starch, petrolatum or the like in terms of ease of carrier molding, and among these, cellulose is more preferable. The content of the organic material is preferably 60% by weight or less, and more preferably 40% by weight or less based on the raw material. If it is more than 60% by weight, there may be a problem that sufficient mechanical strength for industrial use cannot be obtained.

In the pore distribution measured by the mercury intrusion method, the carrier has at least two peaks in which the maximum value of the log differential pore volume exceeds 0.2 ml / g in the pore diameter range of 0.01 μm to 100 μm. .
The range of the pore diameter is preferably 0.05 μm to 50 μm, more preferably 0.1 μm to 40 μm, and still more preferably 0.1 μm to 30 μm. By setting it in the above range, there is a possibility of becoming a catalyst for producing ethylene oxide with high selectivity.
Furthermore, the interval between an arbitrary peak and a peak nearest to the peak is preferably 0.01 μm to 20 μm, more preferably 0.05 μm to 15 μm, and still more preferably 0.1 μm to 13 μm. By setting it in the above range, there is a possibility that the catalyst is prevented from being deteriorated in catalyst performance.
In addition, the difference between the minimum value between the peaks and the maximum value of the peak forming the minimum value is preferably 0.02 ml / g or more, more preferably 0.05 ml / g or more, and 0 More preferably, it is 1 or more.

  In the present invention, the pore distribution of the carrier can be measured by a mercury intrusion method. In the mercury intrusion method, the pore diameter is measured on the assumption that all the pores are cylindrical, the pore diameter is represented by diameter D, and the pore volume is represented by V. The “log differential pore volume distribution” is suitable for expressing a wide range of pore distribution, and is a value obtained by dividing the differential pore volume dV by the logarithmic difference value d (logD) of the pore diameter. This is plotted against the average pore diameter of each section. “Differential pore volume dV” refers to an increase in pore volume between measurement points. For example, as shown in FIG. 1, the horizontal axis indicates the pore diameter (logarithmic scale), and the vertical axis indicates the log differential pore volume. The cumulative pore volume distribution is obtained by plotting the pore diameter on the horizontal axis and the pore volume ΣV on the vertical axis. For example, as shown in FIG. 2, the horizontal axis indicates the pore diameter (logarithmic scale), and the vertical axis indicates the integrated pore volume. In addition, as a specific technique of the mercury intrusion method for obtaining the pore distribution, the technique described in Examples described later is adopted.

  In the pore distribution measured by the mercury intrusion method, “peak” means that the maximum value of the log differential pore volume is 0.2 ml / g or more and the maximum value is less than 0.2 ml / g. Are not included in the “peak”.

The carrier has a pore diameter in the range of 0.01 μm to 100 μm, and at least one of the peaks having a maximum log differential pore volume of 0.2 ml / g or more is in the range of 0.5 μm to 3.0 μm. To do.
The range is preferably 0.5 μm to 2.0 μm, more preferably 0.6 μm to 2.0 μm, and still more preferably 0.6 μm to 1.8 μm. By being in the above range, there is a possibility that the catalyst is suppressed from lowering the ethylene oxide selectivity due to long-term use.
The peak having a maximum log differential pore volume of the carrier of 0.2 ml / g or more may be present outside the above range, preferably 4.0 μm to 100 μm, more preferably 4.0 μm. It is the range of -50 micrometers, More preferably, it is the range of 4.0 micrometers-20 micrometers.

Preferably the specific surface area of the carrier is 0.8m ² /g~1.8m ² / ^g, more preferably ^{0.8m 2 /g~1.7m 2 / g, 1.0m} 2 / more preferably g~1.7m is ² / ^g, particularly preferably 1.3m ² /g~1.7m 2 / g. If the specific surface area is too small, when silver is supported on the support as a catalyst component, the supported silver particles become too large, and it is necessary to increase the reaction temperature in order to increase the conversion of ethylene, resulting in the selection of ethylene oxide. The rate may decrease. 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 ethylene oxide selectivity may be lowered.

  The water absorption of the carrier is preferably 40% by weight to 70% by weight, more preferably 45% by weight to 65% by weight, and still more preferably 50% by weight to 65% by weight. If it is smaller than the above range, the number of catalyst components that can be supported at one time decreases, and the number of catalyst component impregnation steps described later may increase. On the other hand, if it is larger than the above range, the required surface area may not be maintained.

The silicon content of the carrier is 0.01 wt% to 1.0 wt% in terms of SiO _2, preferably 0.01 wt% to 0.9 wt%, 0.01 wt% to 0.8 % By weight is more preferable, and 0.01% by weight to 0.5% by weight is more preferable. If the silicon content is too high, the ethylene oxide selectivity may decrease. If the silicon content is too low, the reaction temperature must be increased to increase the ethylene conversion, resulting in a decrease in ethylene oxide selectivity. there's a possibility that.
The silicon content in the catalyst carrier can be measured by inductively coupled plasma emission spectroscopy.

The sodium content in the carrier is preferably 10 ppm by weight to 1500 ppm by weight in terms of Na ₂ O, more preferably 10 ppm by weight to 1000 ppm by weight, still more preferably 50 ppm by weight to 1000 ppm by weight, more preferably 210 ppm by weight. Particularly preferred is ppm to 800 ppm by weight. By setting it as the above range, there is a possibility that the catalyst has high ethylene oxide selectivity.
The sodium content in the carrier can be measured by atomic absorption spectroscopy.

(Catalyst component)
The catalyst for producing ethylene oxide of the present invention contains silver and rhenium as catalyst components supported on a carrier.

  The content of silver is preferably 5.0% by weight to 30.0% by weight, more preferably 10.0% by weight to 30.0% by weight, and more preferably 11.0% by weight to 27% by weight based on the total catalyst for producing ethylene oxide. More preferred is 0.0% by weight. When the content of silver is small, the catalyst performance tends to decrease.

  As the compound for donating silver, various compounds such as silver oxide, silver nitrate, silver carbonate, silver oxalate and the like can be used. Among these, silver oxalate is particularly preferable.

  The content of rhenium with respect to the whole catalyst for producing ethylene oxide is preferably 10 ppm by weight to 1000 ppm by weight, more preferably 100 ppm by weight to 900 ppm by weight, and even more preferably 200 ppm by weight to 800 ppm by weight. When the rhenium content is low, there is a tendency that sufficient selectivity cannot be obtained. On the other hand, if the content of rhenium is large, it is necessary to increase the reaction temperature in order to increase the conversion rate of ethylene, and as a result, the ethylene oxide selectivity may decrease.

  Examples of compounds that donate rhenium include perrhenic acid compounds, rhenium oxide, and rhenium chloride. Among these, ammonium perrhenate is preferable.

In addition to silver and rhenium, the catalyst for producing ethylene oxide of the present invention preferably contains an element belonging to Group 1 of the long-period periodic table from the viewpoint of obtaining a high ethylene oxide selectivity, and among these, cesium and lithium are more preferable.
The content of cesium with respect to the entire catalyst for producing ethylene oxide is preferably 10 ppm by weight to 2000 ppm by weight, more preferably 100 ppm by weight to 1500 ppm by weight, and even more preferably 300 ppm by weight to 1200 ppm by weight. If the cesium content is too small, sufficient selectivity tends to be difficult to obtain. On the other hand, when the content of cesium is too large, it is necessary to increase the reaction temperature in order to increase the conversion rate of ethylene, and as a result, the ethylene oxide selectivity may decrease.

  Examples of compounds that donate cesium include various compounds such as hydroxide, nitrate, carbonate, acetate, chloride, oxide, and oxalate. Among these, hydroxide is preferable.

  The content of lithium with respect to the whole catalyst for producing ethylene oxide is preferably 10 ppm by weight to 1000 ppm by weight, more preferably 20 ppm by weight to 800 ppm by weight, and even more preferably 50 ppm by weight to 500 ppm by weight. If the lithium content is too small, sufficient ethylene oxide selectivity tends to be difficult to obtain. On the other hand, if the lithium content is too high, it is necessary to increase the reaction temperature in order to increase the conversion rate of ethylene, and as a result, the ethylene oxide selectivity may decrease.

  Examples of the compound that donates lithium include various compounds such as hydroxide, nitrate, carbonate, acetate, chloride, oxide, and oxalate. Among these, hydroxide is preferable.

(Catalyst production method)
When the catalyst component is supported on the carrier, the catalyst component is preferably dissolved in an appropriate solvent to prepare a catalyst component-containing solution. As the solvent, water is usually selected for ease of handling, but alcohols such as methanol and ethanol, and a mixed solution of water and alcohol can also be used.

  In the catalyst component-containing solution, the higher the silver concentration in the solution, the higher the silver concentration when impregnated on the carrier is preferable. Therefore, it is preferable to use a complex forming agent so that the catalyst component is easily dissolved in the solvent. As the complex-forming agent, a compound that easily forms a complex with silver and the resulting complex is easily dissolved in the solvent is preferable.

Examples of such a complex-forming agent include amine compounds. Specific examples of this amine compound include C1-C6 monoamines such as ammonia, pyridine, acetonitrile and butylamine, C1-C6 alkanolamines such as ethanolamine, carbons such as ethylenediamine and 1,3-propanediamine. Among them, ammonia, pyridine, butylamine, ethanolamine, ethylenediamine, 1,3-propanediamine and the like are preferable, and one kind selected from ethylenediamine and 1,3-propanediamine is preferable. Use or mixed use of two kinds is more preferable. The density | concentration of said each component is suitably determined according to content for every component.

  The support may be impregnated with the catalyst component-containing solution as it is, but before impregnating the catalyst component-containing solution, the support is washed with ion-exchanged water or is a part of the catalyst component. Lithium or lithium and cesium are preferably supported on a carrier (support treatment), which leads to an improvement in catalyst life.

  The lithium compound and cesium compound used for the carrier treatment are preferably those having low solubility in the catalyst component-containing solution because the re-elution is small when the carrier is impregnated with the catalyst component-containing solution. Specifically, it is optimal that both the lithium compound and the cesium compound are carbonates. Moreover, as a solvent which melt | dissolves a lithium compound and a cesium compound, water is preferable from the ease of handling.

  The temperature of ion-exchanged water used for carrier washing is preferably 0 ° C to 100 ° C, more preferably 60 ° C to 100 ° C, and still more preferably 80 ° C to 100 ° C. The weight of ion-exchanged water used per carrier washing is preferably equal to or more than the weight of the carrier, more preferably 2 times or more, still more preferably 3 times or more. The carrier washing is preferably 3 times or more, more preferably 5 times or more.

  After carrying out the above carrier treatment, the carrier, the excess lithium compound and the cesium compound-containing solution are separated, and then a drying treatment such as reduced pressure drying or heat treatment is performed. This heat treatment is preferably performed using air, an inert gas such as nitrogen, or superheated steam at 100 ° C. to 300 ° C., more preferably 110 ° C. to 220 ° C. Particularly preferred is a method using superheated steam.

(Catalyst component loading process)
Next, the step of supporting the catalyst component on the carrier (catalyst component supporting step) will be described. In this catalyst component loading step, the catalyst component-containing solution is impregnated into a carrier or a carrier that has been subjected to carrier treatment (catalyst component impregnation step), and then heated in an atmosphere containing at least an inert gas (preheating step). Furthermore, it is a process including heating in an oxygen-containing atmosphere (heat treatment process).

  Examples of the catalyst component impregnation step include a method of immersing the catalyst component-containing solution in a carrier or carrier-treated carrier, and a method of spraying the catalyst component-containing solution on a carrier or carrier-treated carrier in a spray form. 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.

  The atmospheric gas in the preheating step is preferably an inert gas such as nitrogen or water vapor, but may contain oxygen. As the oxygen source, high-purity oxygen or air can be used, but air is preferred from the viewpoint of safety and economy.

  The oxygen concentration can be measured using an oximeter or a gas chromatograph. As will be described later, when the atmosphere of the preheating step is a mixed gas of oxygen or air and water vapor, sampling the atmospheric gas and liquefying the water vapor by cooling, the remaining gas phase part volume and It is convenient to obtain the concentration of oxygen or air in the preheating atmosphere from the volume ratio.

The temperature and time of the preheating step are selected so that the size of the silver particles to be deposited is appropriate. In particular, the preheating temperature greatly affects the size of the silver particles deposited. The lower limit of the preheating temperature is preferably 100 ° C, more preferably 125 ° C, and further preferably 150 ° C. If the preheating temperature is lower than 100 ° C., silver particles may not be sufficiently precipitated. This is presumably because the amount of heat required to deposit the metallic silver particles is not sufficiently supplied due to the low temperature. On the other hand, the upper limit of the preheating temperature is preferably 300 ° C, more preferably 200 ° C. When preheating temperature becomes higher than 300 degreeC, there exists a tendency for the conversion rate of ethylene to fall and the yield of ethylene oxide to fall. This is presumably because the deposited silver metal particles were too large.
The time for the preheating step is preferably 5 minutes to 60 minutes, more preferably 10 minutes to 30 minutes.

  In the apparatus used in the preliminary heating process, a predetermined amount of atmospheric gas is continuously supplied and exhausted outside the apparatus. From the viewpoint of suppressing environmental deterioration and improving efficiency, it is preferable to discharge outside the apparatus as a part of the atmospheric gas and to circulate the remainder. The exhaust ratio of the atmospheric gas is preferably 5% to 30%.

  In the preliminary heating step, the gas linear velocity is preferably 0.5 m / sec to 5 m / sec, and more preferably 1 m / sec to 3 m / sec. When the gas linear velocity is smaller than the above range, the moisture, the complex forming agent, or the decomposition product thereof contained in the impregnated support may not be sufficiently removed. On the other hand, if it is larger than the above range, about 5 m / sec is sufficient because there is almost no effect of increasing the gas linear velocity.

  Industrially, it is preferable that the catalyst component-impregnated support is continuously supplied to the preheating device, stays in the device for a certain time, and is discharged outside the device. As the equipment, the catalyst component impregnated carrier is loaded on a horizontally moving band and moved and heated (band dryer), or loaded in an inclined rotating cylinder and moved obliquely downward and heated (rotary drying). ("Chemical Engineering Handbook (5th revised edition)" 1988, edited by Chemical Engineering Association, Maruzen Co., Ltd., issued March 18, 1988, p674-683). Among these, it is preferable to use a band drier (aeration band drier) that allows the heated atmospheric gas to be vented because of easy contact between the impregnated carrier and the atmospheric gas.

  In the heat treatment step, the carrier carrying the catalyst component obtained in the preheating step is further heated in an oxygen-containing atmosphere to change the silver compound to metallic silver to obtain an ethylene oxide production catalyst. The heat treatment temperature is preferably in the range of 275 ° C. to 450 ° C., and the lower limit temperature is more preferably 335 ° C. because the ethylene oxide selectivity can be increased. The upper limit temperature is 385 ° C. from the viewpoint of energy efficiency and economy. More preferred.

  The oxygen concentration in the heat treatment step is preferably 5% by volume to 30% by volume, and more preferably 15% by volume to 25% by weight. Other gas components are preferably nitrogen, argon, helium, carbon dioxide, or a mixture thereof, but are not particularly limited as long as the object and effect of the present invention are not impaired. The gas used in the heat treatment process is preferably air for simplicity.

The heat treatment time in the heat treatment step is preferably 1 hour to 50 hours. Since ethylene oxide selectivity can be increased, 1.2 hours or more is more preferable, and 2 hours or more is even more preferable. Further, from the viewpoint of energy efficiency and economy, it is more preferably 20 hours or less, further preferably 10 hours or less, and most preferably 5 hours or less. Note that the heat treatment time is a time during which the heat treatment is held in the predetermined temperature range. The heat treatment may be carried out in a plurality of times. In this case as well, the time outside the preferred lower limit temperature of 275 ° C. and the preferred upper limit temperature of 450 ° C. is 5% or less of the heat treatment time. It is preferable to set it to 3% or less. If the time outside the predetermined temperature range becomes long, the catalyst may not be sufficiently activated.

  As an apparatus used in the heat treatment 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.

The sodium content in the ethylene oxide production catalyst is preferably 1500 ppm by weight or less, more preferably 1000 ppm by weight or less, further preferably 800 ppm by weight or less, and particularly preferably 500 ppm by weight or less in terms of Na ₂ O. If it exceeds 1500 ppm by weight, the catalyst may not exhibit a high ethylene oxide selectivity.
The sodium content in the ethylene oxide production catalyst can be measured by atomic absorption spectroscopy.

The content of silicon in the ethylene oxide production catalyst is preferably 1% by weight or less, more preferably 0.8% by weight or less, still more preferably 0.8% by weight or less, and 0.5% by weight in terms of SiO _2. % Or less is particularly preferable. If it is more than 1% by weight, the ethylene oxide selectivity may be lowered.
The silicon content in the ethylene oxide production catalyst can be measured by inductively coupled plasma emission spectroscopy.

(Reaction using catalyst for ethylene oxide production)
The reaction for converting ethylene to ethylene oxide using the catalyst for producing ethylene oxide of the present invention can be carried out by a generally known method. The reaction pressure is usually 0.1 MPa to 3.6 MPa (0 to 35 kg / cm ² G), and the reaction temperature is usually 180 ° C. to 350 ° C., preferably 200 ° C. to 300 ° C. The composition of the reaction raw material gas is generally a mixed gas of 1% to 40% by volume of ethylene and 1% to 20% by volume of molecular oxygen, and is generally a diluent such as methane or nitrogen. The active gas can be present in a certain proportion, for example, 1% to 70% by volume. As the molecular oxygen-containing gas, air or industrial oxygen is usually used. Furthermore, as a reaction modifier, for example, by adding about 0.1 to 50 ppm of halogenated hydrocarbon to the reaction raw material gas, the formation of hot spots in the catalyst can be prevented, and the performance of the catalyst, particularly the catalyst selectivity is greatly increased. Can be improved.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. First, analysis / measurement and measurement methods and raw materials will be described.

<Analysis, measurement and evaluation methods>
(1) Log differential pore volume distribution and integrated pore volume distribution of carrier The carrier sample was subjected to reduced pressure treatment under reduced pressure (50 μmHg or less) for 10 minutes using Micromeritex Autopore IV 9520, and then mercury. The indentation / retraction curve was measured, and the log differential pore volume distribution and the integrated pore volume distribution of the support were calculated.

(2) Measurement of specific surface area of carrier The carrier sample subjected to pretreatment (250 ° C., nitrogen gas flow for 15 minutes) was subjected to a BET one-point method (adsorbed gas: nitrogen) using Maxsorb HM Model-1201 manufactured by Mountech. The specific surface area of the carrier was measured.

(3) Measurement of silica content in carrier After adding sodium carbonate and boric acid to a carrier sample and melting it by heating, the silica component was extracted with hydrochloric acid and pure water and measured by ICP emission method. Measurements are in terms of SiO _2.

(4) Measurement of sodium content in carrier After adding sulfuric acid, phosphoric acid and hydrofluoric acid to a sample obtained by pulverizing the carrier and heating and extracting, the extract was measured by atomic absorption method. Measurements are in terms of Na ₂ O.

(5) Measurement of water absorption rate of carrier After measuring the weight (α) of the carrier sample, adding a sufficient amount of water to the carrier sample, heating at 40 ° C under reduced pressure in an evaporator and holding for 3 minutes, This was taken out and the weight (β) of the carrier was measured. The water absorption was calculated by the following formula.

(6) Measurement of ethylene oxide selectivity The ethylene oxide selectivity was expressed as the ratio of the number of moles of ethylene oxide produced to the number of moles of ethylene consumed.

(7) Adjustment of reaction temperature The reaction temperature was adjusted so that the amount of ethylene oxide produced per hour (STY) of the catalyst was 1 L.

Example 1
(Preparation of catalyst)
(Carrier processing step)
100 g of carrier A shown in Table 1 was immersed in 300 ml of boiling deionized water for 20 minutes, the carrier was taken out from the deionized water, and washed with deionized water. This operation was repeated 5 times. Subsequently, the support | carrier which repeated immersion-washing operation 5 times was heat-dried with the superheated steam of 150 degreeC for 20 minutes at the flow rate of 2 m / sec, and 100 g of washing | cleaning support | carrier A was obtained.

(Preparation of silver complex solution)
2590 g of silver nitrate (AgNO ₃ ) was dissolved in 9240 ml of deionized water to form an aqueous silver nitrate solution, 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 with deionized water, and the silver hydroxide precipitate was washed until the pH of the supernatant was 10 or less and the conductivity was 45 μΩ / cm or less. When 2290 ml of deionized water and 961 g of oxalic acid dihydrate were added to the silver hydroxide precipitate, the pH became 9.8, and the silver hydroxide precipitate became a silver oxalate precipitate. During the addition of oxalic acid dihydrate, the temperature was adjusted to 50 ° C. or lower. The silver oxalate precipitate was filtered off and washed with deionized water to obtain a silver oxalate slurry (water content 23.0% by weight). A silver complex solution was prepared by gradually adding and dissolving 262 g of the silver oxalate slurry in an aqueous solution consisting of 72.8 g of ethylenediamine, 20.0 g of 1,3-diaminopropane, and 92.9 g of water. The specific gravity of this silver complex solution was 1.57 g / ml.

(Preparation of catalyst component-containing solution for the first impregnation)
To 16.7 g of the silver complex solution obtained by the above operation, 3.8 ml of deionized water was added, and 1
A catalyst component-containing solution for the second impregnation was obtained.

(First preparation of catalyst component impregnated support and catalyst intermediate)
The catalyst component-containing solution was impregnated into 30 g of the washing carrier A, and heated to 40 ° C. under reduced pressure in an evaporator. The first catalyst component-impregnated support thus obtained was calcined in superheated steam at 200 ° C. for 15 minutes at a flow rate of 2 m / sec. Subsequently, it heated at 300 degreeC for 2 hours in the heating furnace in air atmosphere, and obtained the catalyst intermediate body.

(Preparation of catalyst component-containing solution for second impregnation)
To 14.6 g of a silver complex solution having a specific gravity of 1.57 g / ml, 0.3 ml of an aqueous solution having a cesium hydroxide monohydrate (CsOH.H ₂ O) concentration of 13.0 wt%, ammonium perrhenate (NH ₄ ReO ₄ ) 0.6 ml of an aqueous solution with a concentration of 4.9 wt%, 0.3 ml of an aqueous solution with a lithium sulfate monohydrate (Li ₂ SO ₄ .H ₂ O) concentration of 3.4 wt%, ammonium metatungstate (H ₂₆ N ₆ O ₄₀ W ₁₂ · xH ₂ O) 2.0% by weight aqueous solution 0.3 ml, lithium carbonate (Li ₂ CO ₃ ) 0.02 g, and deionized water 3.1 ml were added, and the catalyst component for the second impregnation A containing solution was obtained.

(Second preparation of catalyst component impregnated support and catalyst precursor)
The catalyst component-containing solution of the second impregnation was impregnated into 35.6 g of the catalyst intermediate, and heated to 40 ° C. under reduced pressure in an evaporator. The catalyst component-impregnated support thus obtained was calcined in 200 ° C. superheated steam for 15 minutes at a flow rate of 2 m / sec to obtain a catalyst precursor.

(Heat treatment process)
The obtained catalyst precursor was then heated in an oven at 370 ° C. for 2 hours in a heating furnace, and then cooled to room temperature to obtain a catalyst.

(Manufacture of ethylene oxide)
The obtained catalyst 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% by volume, oxygen 8.5% by volume, 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 1 L of catalyst and ethylene oxide production (STY) per hour were 0.2 kg-EO / L-cat · h. The reaction results are shown in Table 1.

(Comparative Example 1)
(Preparation of catalyst)
(Carrier processing step)
13,000 g of carrier B shown in Table 1 is placed in 29000 ml of boiling deionized water.
It was immersed for 0 minutes, the carrier was taken out from 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 13000 g of washing carrier B.

(Preparation of silver complex solution for the first impregnation)
2310 g of silver oxide (Ag ₂ O) was dissolved in 13000 ml of deionized water, and the temperature was adjusted to 50 ° C. To this, 1256 g of oxalic acid dihydrate was added, and the pH became 9.7. During the addition of oxalic acid dihydrate, the temperature was adjusted to 50 ° C. or lower. A silver oxalate precipitate was thus obtained. After the precipitate is filtered off, it is washed with deionized water, and a silver oxalate slurry (water content 21
. 3% by weight) was obtained. The silver oxalate slurry thus obtained (3846 g) was gradually added and dissolved in an aqueous solution consisting of 1095 g of ethylenediamine, 300 g of 1,3-diaminopropane, and 1396 g of water to prepare a silver complex solution. The specific gravity of this silver complex solution was 1.61 g / ml.

(Preparation of catalyst component-containing solution for the first impregnation)
To 6570 g of the silver complex solution obtained by the above operation, 426 ml of deionized water was added to obtain a catalyst component-containing solution for the first impregnation.

(First preparation of catalyst component impregnated support and catalyst intermediate)
The obtained catalyst component-containing solution was impregnated into 12,000 g of the washing carrier A and heated to 40 ° C. under reduced pressure in an evaporator. The first catalyst component-impregnated support thus obtained was calcined in 200 ° C. superheated steam for 15 minutes at a flow rate of 2 m / sec to obtain a catalyst intermediate.

(Preparation of second-impregnated silver complex solution)
2029 g of silver oxide (Ag ₂ O) was dissolved in 11500 ml of deionized water, and the temperature was adjusted to 50 ° C. To this, 1103 g of oxalic acid dihydrate was added, and the pH became 9.5. During the addition of oxalic acid dihydrate, the temperature was adjusted to 50 ° C. or lower. A silver oxalate precipitate was thus obtained. After the precipitate is filtered off, it is washed with deionized water, and a silver oxalate slurry (water content 18
. 1% by weight) was obtained. The silver oxalate slurry 3246 g thus obtained was gradually added and dissolved in an aqueous solution consisting of 961 g of ethylenediamine, 264 g of 1,3-diaminopropane, and 1226 g of water to prepare a silver complex solution. The specific gravity of this silver complex solution was 1.63 g / ml.

(Preparation of catalyst component-containing solution for second impregnation)
To 5648 g of the silver complex solution obtained by the above operation, 120 ml of an aqueous solution having a cesium hydroxide monohydrate (CsOH.H ₂ O) concentration of 13.0 wt% and an ammonium perrhenate (NH ₄ ReO ₄ ) concentration of 4.9 240 ml by weight aqueous solution, 120 ml aqueous solution having a lithium sulfate monohydrate (Li ₂ SO ₄ .H ₂ O) concentration of 3.4 wt%, ammonium metatungstate (H ₂₆ N ₆ O ₄₀ W ₁₂ · xH ₂ O) 120 ml of an aqueous solution having a concentration of 2.0% by weight, 120 ml of an aqueous solution having a lithium hydroxide (LiOH) concentration of 6.4% by weight, and 100 ml of deionized water were added to obtain a catalyst component-containing solution for the second impregnation.

(Second preparation of catalyst component impregnated support and catalyst precursor)
180 ml of deionized water was added to 5434 g of the catalyst component-containing solution for the second impregnation thus obtained, then impregnated into 11692 g of the catalyst intermediate, and heated to 40 ° C. under reduced pressure in an evaporator. The catalyst component-impregnated support thus obtained was calcined in 200 ° C. superheated steam for 15 minutes at a flow rate of 2 m / sec to obtain a catalyst precursor.

(Heat treatment process)
The obtained catalyst precursor was then heated in an oven at 370 ° C. for 2 hours in a heating furnace, and then cooled to room temperature to obtain a catalyst. Table 1 shows the physical properties of the carrier.

(Manufacture of ethylene oxide)
Ethylene oxide was produced in the same manner as in Example 1 except that the catalyst obtained in Comparative Example 1 was used. The reaction results are shown in Table 2.

  From the results shown in Tables 1 and 2, according to the present invention, the stability of the catalyst performance is improved, and ethylene oxide can be obtained with good reaction characteristics for a long period of time from the initial stage of the reaction without causing an extreme increase in the reaction temperature. A production catalyst may be provided.

Claims (5)

A catalyst for ethylene oxide production comprising a support, silver and rhenium,
The carrier contains 0.01% to 1.0% by weight of silicon in terms of SiO _{2 in the} carrier, and in the pore distribution measured by the mercury intrusion method, the log has a diameter in the range of 0.01 μm to 100 μm. A catalyst for producing ethylene oxide, wherein at least two peaks having a maximum value of the differential pore volume of 0.2 ml / g or more are present, and at least one of the peaks is in a range of 0.5 µm to 3.0 µm. The specific surface area of the carrier is 0.8m ² /g~1.8m ² / g, a catalyst for production of ethylene oxide according to claim 1.   The ethylene oxide production catalyst according to claim 1 or 2, wherein the carrier has a water absorption rate of 40 wt% to 70 wt%. The catalyst for ethylene oxide production according to any one of claims 1 to 3, wherein the carrier further contains sodium, and the sodium content in the carrier is 10 ppm by weight to 1500 ppm by weight in terms of Na ₂ O.   The manufacturing method of ethylene oxide which oxidizes ethylene to ethylene oxide in presence of the catalyst for ethylene oxide manufacture of any one of the said Claims 1 thru | or 4.

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