JP5388925B2 - Catalyst for producing ethylene oxide and method for producing ethylene oxide - Google Patents

Description

  The present invention relates to an ethylene oxide production catalyst and an ethylene oxide production method.

  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. With regard to the silver catalyst used for this catalytic gas phase oxidation, many techniques have been proposed with respect to the carrier, the loading method, the type of reaction accelerator, the amount added, and the like.

Many proposals have been made using silver as a main component and using other metals / compounds such as rhenium / compounds and alkali metals as other components (Cited Document 1 and others). The catalyst component is supported on a carrier to form a catalyst, and the following techniques have been proposed for the carrier. For example, a catalyst composition for producing ethylene oxide using a support having a surface area of less than 20 m ² / g is disclosed (Cited document 1). As a combination of a catalyst component and a support, silver metal, rhenium, tungsten, molybdenum or a compound thereof, and a component in which a part of rubidium or cesium is substituted with potassium are placed on a support having a surface area of 500 m ² / kg or more. A catalyst composition for producing ethylene oxide is disclosed (Cited document 2).

Further, as a technique for examining the support, pores having a surface area of at least 1 m ² / g and a diameter in the range of 0.2 μm to 10 μm correspond to at least 70% of the total pore volume, and the pores In addition, a catalyst using a carrier having a pore size distribution that gives a pore volume of at least 0.27 ml / g based on the weight of the carrier is disclosed (Cited document 3). It is also disclosed to use a carrier having a specific surface area of 0.6 to 3.0 m ² / g and ₂ to 50 in terms of SiO ₂ / Na ₂ O (Cited document 4). These are not sufficiently satisfactory because their activity and durability are affected by the relationship between the carrier and the catalyst component and the preparation of the catalyst.

JP 63-126552 A JP-T-2006-521927 JP 2005-518276 A JP 2007-301553 A

  In the above Patent Documents 1 and 2, there is a problem in terms of durability of the catalyst because the oxidation state of rhenium, movement and aggregation are likely to occur. Further, in Patent Document 3, depending on the catalyst composition, movement of catalyst components or the like occurs, and the durability of the catalyst is likely to be significantly reduced. Furthermore, in Patent Document 4, at such a Na content, the movement of a small amount of sodium component from the inside of the support to the surface that proceeds with the catalytic reaction changes the interaction between silver on the catalyst surface and the cocatalyst, Depending on the catalyst composition, there is a problem in that the selectivity and activity are rapidly reduced. In these technologies, various catalyst compositions and physical properties have been proposed, but only focusing on the catalyst composition, etc., and taking full advantage of the correlation between the catalyst composition and the physical properties that meet the reaction gas conditions. is not. An object of the present invention is to provide a method for producing ethylene oxide by proposing a catalyst composition and physical properties suitable for the reaction gas conditions, and thereby obtaining high selectivity to ethylene oxide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors controlled the above-mentioned problem by controlling the finer pore diameter, not the pore diameter of the catalyst support obtained by the mercury intrusion method that is generally measured. It came to solve. The present invention is specified as follows.

In the present invention, the pore volume having a pore diameter of 0.5 to 2.0 nm calculated by SF method analysis from an argon adsorption isotherm measured at liquid nitrogen temperature is 0.1 × 10 ^{−4 to} 8.0 × 10. ^A catalyst for ethylene oxide production obtained by supporting a catalyst component containing silver (Ag), cesium (Cs), rhenium (Re), and tungsten (W) on a carrier having ⁻⁴ cm ³ / g is there. Moreover, it is the manufacturing method of the said catalyst, and the manufacturing method of ethylene oxide using the said catalyst.

  By using the catalyst of the present invention, ethylene oxide can be produced with high selectivity. Furthermore, the selectivity becomes remarkable under the reaction conditions proposed by the present invention. The production scale of ethylene oxide is estimated to be about 18 million tons per year and is very large. For this reason, for example, even if the decrease in selectivity after 100 days is suppressed by only 1%, the amount of raw ethylene used is significantly saved, and its economic effect is very large. Under such circumstances, the development of silver catalysts having better selectivity has been a continuous theme for researchers in the technical field.

FIG. 1 shows the pore diameter (horizontal axis) and pore volume (vertical axis: integrated value of pore volume, so-called integral display) of the support.

  The present invention will be specifically described below, but is not limited to the following description as long as the effects of the present invention are exhibited.

(Carrier)
In the present invention, the carrier composition only needs to have α-alumina as a main component. In addition to α-alumina, silicon (Si) is added in an amount of 0.1 to 5.0% by mass in terms of SiO ₂ , sodium ( Na) may be contained in an amount of 0.001 to 1.0% by mass in terms of Na ₂ O. Hereinafter, it is expressed in “%”, but unless otherwise specified, the whole carrier is 100% by mass. The carrier “having α-alumina as a main component” means that the content of α-alumina in the carrier is 70% by mass or more (upper limit = 100% by mass) with respect to 100% by mass of the total mass of the carrier. It means that there is. The content of α-alumina in the support is preferably 90% by mass or more (upper limit = 100% by mass), more preferably 95% by mass or more (upper limit = 100% by mass). The carrier may further contain other components as long as it contains α-alumina as a main component and Si and Na in the above content.

  Other components other than the above components are not particularly limited, and examples thereof include alkali metals (excluding Na) and alkaline earth metals, oxides thereof, transition metals and oxides thereof. There is no restriction | limiting in particular about these content. Among these, it is preferable that alkali metals other than sodium and cesium are substantially not included, and more preferably, the content of alkali metals other than sodium and cesium (as oxide) is based on 100% by mass of the total mass of the carrier. 0.001 to 5% by mass. Moreover, preferable content (in oxide conversion) of alkaline-earth metal is 0.001-5 mass% with respect to 100 mass% of total mass of a support | carrier. Moreover, preferable content (in oxide conversion) of a transition metal is 0-5 mass% with respect to 100 mass% of the total mass of a support | carrier.

  The carrier raw material α-alumina is usually a powder having a purity of 90% or higher, preferably 95% or higher, more preferably 99% or higher, particularly preferably 99.5% or higher. In addition to α-alumina powder, alumina oxide, particularly amorphous alumina, silica, silica aluminum, mullite, zeolite, etc. (these are collectively referred to as “amorphous alumina etc.”); potassium oxide, sodium oxide, cesium oxide, etc. Alkali metal oxides and alkaline earth metal oxides (collectively referred to as “alkalis etc.”); transition metal oxides such as iron oxide and titanium oxide may be included. The raw material α-alumina powder before forming the carrier into a molded body may contain a small amount of sodium (sodium oxide). In this case, by previously grasping the amount of sodium in the powder, a carrier can be obtained by adding a sodium compound at the time of preparing the carrier so as to obtain a specific amount of sodium.

  The particle diameter of the carrier raw material α-alumina powder is not particularly limited, but the primary particle diameter of the α-alumina powder is preferably 0.01 to 100 μm, more preferably 0.1 to 20 μm. More preferably, it is 0.5-10 micrometers, Most preferably, it is 1-5 micrometers. The secondary particle size of the α-alumina powder 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. It is.

The specific surface area of the carrier raw material α-alumina powder is not particularly limited, but the specific surface area of the α-alumina powder is preferably 0.01 to ²⁰ m ² / g, more preferably 0.1 to 10 m. ² / g, more preferably 0.1 to ⁵ m ² / g, and particularly preferably 0.3 to ⁴ m ² / g.

The volume of pores having a pore diameter of 0.5 to 2.0 nm of the α-alumina powder as a support raw material is not particularly limited, but preferably 0.1 × 10 ⁻⁴ to 10 × 10 ⁻⁴ cm. ³ / g more preferably 0.5 × 10 ^{−4 to} 8.0 × 10 ⁻⁴ cm ³ / g, still more preferably 1.0 × 10 ^{−4 to} 7.0 × 10 ⁻⁴ cm ³ / g, particularly preferably Is 1.0 × 10 ^{−4 to} 6.0 × 10 ⁻⁴ cm ³ / g. About the volume of the pore which has the pore diameter of 0.5-2.0 nm shown here, the method computed by SF method analysis from the argon adsorption isotherm of the sample measured at the liquid nitrogen temperature mentioned later was used. In addition, pores having a diameter in the above nanometer order range may be hereinafter referred to as fine pores.

  Moreover, the linear shrinkage rate of the α-alumina powder as the carrier material is preferably 12 to 20%. “Linear shrinkage” shown here is about 1-5 mass% flux added to α-alumina powder, molded at a pressure of about 50 MPa, and then fired at about 1600-1700 ° C. for 2-3 hours. It refers to the contraction rate in the length direction.

Carrier, a silicon (Si), but may also include 0.1 to 5.0 wt% in terms of SiO _2. By including silicon in such an amount, it is possible to suppress and prevent a decrease in the catalytic function of rhenium and tungsten, and there is an advantage that high selectivity can be stably maintained for a long period of time. Preferably, the Si content (in terms of SiO ₂ ) in the carrier is 0.1 to 3.0% by mass, more preferably 0.5 to 2.5% by mass with respect to 100% by mass of the total mass of the carrier. is there. When the Si content in the carrier (in terms of SiO ₂ ) is below the lower limit, sufficient life stability may not be obtained. Conversely, when the upper limit is exceeded, high selectivity is obtained from the beginning. May not be obtained.

  In addition, the silicon raw material includes covalently bonded compounds such as silicon oxide, silica sol, silicon nitride, silicon carbide, silane, and silicon sulfide; sodium silicate, ammonium silicate, sodium aluminosilicate, ammonium aluminosilicate, sodium phosphosilicate, and phosphorus silicate. Mention may be made of silicates such as ammonium acid; double salts of silica containing silicon such as feldspar and clay; and silica mixtures. Among these, it is preferable to use a double salt of silica containing silicon such as silicon oxide, sodium silicate, or clay. Here, the addition amount of the silicon compound is adjusted to such an amount that the Si content (in terms of SiO2) is obtained.

Sodium (Na) contained in the carrier may be contained in an amount of 0.001 to 1.0% by mass in terms of Na ₂ O, and by containing sodium in such an amount, deterioration in catalyst performance is suppressed / prevented. There are advantages you can do. Preferably, the Na content (Na ₂ O equivalent) in the carrier is 0.001 to 0.9% by mass, more preferably 0.001% by mass or more and 0.8% with respect to 100% by mass of the total mass of the carrier. It is less than mass%, still more preferably 0.001 to 0.75 mass%, particularly preferably 0.005 to 0.7 mass%. Incidentally, Na content in the carrier when the (Na 2 _O equivalent) is less than the above lower limit, there is a possibility that sufficient life stability is obtained, if it exceeds the upper limit, on the other hand, high selectivity from the initial May not be obtained. Further, sodium contained in such an amount acts as a flux during the firing of the carrier, and also has a function of keeping the fine pore volume of the carrier within the scope of the present invention.

  As the sodium raw material, inorganic salts such as sodium nitrate, sodium carbonate, and sodium hydroxide, organic acids such as sodium acetate, sodium formate, and sodium citrate, and polymer carboxylates such as sodium carboxymethyl cellulose can be used. .

  The composition of the carrier and the content of each component described above can be determined using a fluorescent X-ray analysis method. More specifically, RIX2000 manufactured by RIGAKU can be used as a measuring apparatus, and measurement can be performed by a fundamental parameter method (FP method) or a calibration curve method.

  The carrier is produced by mixing the above components and forming into a certain shape, but it can also be produced by adding a binder at the time of forming. For example, the binder facilitates the extrusion process by imparting lubricity. Inorganic binders include alumina gels combined with a peptizer such as nitric acid or acetic acid. Examples of the organic binder include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, corn starch or an alkali metal salt thereof. Among these, it is preferable to use carboxymethylcellulose, sodium carboxymethylcellulose, and the like.

  It is also preferable to add a pore-forming agent when producing the carrier. The pore-forming agent is a material that is completely removed from the carrier during firing and added to the mixture so that controlled pores remain in the carrier. These materials include coke, carbon powder, graphite, powder plastics (such as polyethylene, polystyrene, polycarbonate, etc.), cellulose and cellulose-based materials, sawdust, and other plant materials such as ground nuts, cashews, walnuts) , Like carbonaceous material. Carbon based binders can also serve as pore formers.

  The carrier is prepared by the following method. An α-alumina powder and binder containing at least α-alumina as a main component, a silicon compound as a raw material for providing silica, a pore forming agent, and an appropriate amount of water are added and kneaded sufficiently, followed by an extrusion molding method. After forming into a predetermined shape such as a spherical shape, a pellet shape, etc., etc., it is dried as necessary, and is 1,000 to 1, under a gas atmosphere such as an inert gas such as helium, nitrogen and argon and / or air. The carrier according to the present invention can be produced by firing at 800 ° C., preferably 1,400 to 1,700 ° C.

  In order to obtain a carrier having a fine pore volume according to the present invention, (1) selection of raw material α-alumina powder having a specific specific surface area, and (2) α-alumina powder having a specific fine pore volume. The methods such as (3) adjustment of the baking temperature, and (4) adjustment of the baking time may be carried out independently or may be combined appropriately.

The silica content in the carrier can be calculated from the amount of silica contained in the powder mainly composed of α-alumina and the silicon compound. The sodium content in the carrier may be adjusted in consideration of the amount of sodium contained in the silicon compound, organic binder and α-alumina. Furthermore, the content may be adjusted by post-adding a silicon compound or a compound containing sodium to the carrier containing SiO ₂ or Na ₂ O thus obtained. Sodium compounds can also be added.

The specific surface area of the support (measured by the BET method using nitrogen gas, hereinafter abbreviated as BET specific surface area) is 0.5 to 3.0 m ² / g. By using such a carrier, there is an advantage that the catalyst component such as rhenium and tungsten can be suppressed / prevented from moving while a sufficient amount of the catalyst component is supported, and the performance deterioration can be suppressed. Preferably, the BET specific surface area of the support is 0.5 to ^2.5 m ² / g, more preferably 0.5 to 2.0 m ² / g.

  If the BET specific surface area of the support is less than the above lower limit, the water absorption rate cannot be sufficiently secured, and it may be difficult to support the catalyst component, or the dispersed state of the catalyst component may be deteriorated and the performance may be deteriorated. . Conversely, when the BET specific surface area of the support exceeds the above upper limit, the catalyst component moves due to thermal degradation, etc., and the supported state of the catalyst during the reaction is likely to change compared to before the reaction. There is a possibility that the degree of decrease in the increase.

(Carrier shape)
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 4-10 mm.

(Measurement of pore volume of carrier by mercury porosimetry)
In the mercury intrusion method, the pore diameter and the pore volume can be measured, and it is necessary to distinguish from the “pore diameter and pore volume calculated by the SF method analysis from the argon adsorption isotherm measured at the liquid nitrogen temperature” according to the present invention. Therefore, these are described as “Hg method pore diameter” and “Hg method pore volume”. In the mercury intrusion method, a carrier deaerated at 200 ° C. for at least 30 minutes is used as a sample, and Autopore III 9420W (manufactured by Shimadzu Corporation) is used as a measuring device, and a pressure range of 1.0 to 60,000 psia and 60 The value measured at this measurement point shall be adopted.

  The Hg method average pore diameter of the carrier is not particularly limited, but is preferably 0.1 to 10 μm, more preferably 0.2 to 4.0 μm, and further preferably 0.3 to 3.0 μm. If the Hg method average pore diameter of the support 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 Hg method average pore diameter of the carrier is 10 μm or less, the strength of the carrier can be ensured to a practical level.

  The Hg pore volume of the carrier is not particularly limited, but is preferably 0.1 to 1.0 mL / g, more preferably 0.2 to 0.8 mL / g, and still more preferably 0.3 to 0.6 mL / g. If the Hg pore volume of the carrier is 0.1 mL / g or more, it is preferable in that the catalyst component can be easily supported. On the other hand, if the Hg pore volume of the carrier is 1.0 mL / g or less, it is preferable in that the strength of the carrier can be ensured to a practical level.

(Measurement of argon adsorption isotherm of carrier and raw material α-alumina powder at liquid nitrogen temperature)
The “pore volume and pore diameter calculated from the SF method by the argon adsorption isotherm measured at liquid nitrogen temperature” specified by the present invention are abbreviated as “A method pore volume” and “A method pore diameter”, respectively. Sometimes described. In addition, the measurement was performed in the following procedures using the Nippon Bell Co., Ltd. high-accuracy specific surface area / pore distribution measuring apparatus and product surface “BELSORP-max”. A predetermined amount of sample was put in a quartz tube, and the system was evacuated and heated at 250 ° C. for 4 hours. After cooling the sample tube with liquid nitrogen, a predetermined amount of argon is introduced into the system, and the amount of argon adsorbed on the carrier is measured from the pressure at that time. This measurement was performed in a relative vapor pressure range of about 10 ^{−7 to} 0.99, and an adsorption isotherm was created. Based on the obtained adsorption isotherm, A method pore volume and A method pore diameter were calculated by SF method (Saito-Foley method) analysis. In addition, the volume of the pore in the range of the pore diameter of 0.5 nm to 2.0 nm may be abbreviated as Vp _0.5 nm to 2.0 nm by the SF method analysis. Here, the SF method analysis is a calculation of the pore volume and the pore diameter using a cylindrical micropore based on the adsorption potential theory as a model. The details are described in, for example, American Institute of Chemical Engineers, Vol. 32, p. 429, published in 1991.

Vp _{0.5 nm to 2.0 nm} of the carrier is 0.1 × 10 ^{−4 to} 8.0 × 10 ⁻⁴ cm ³ / g, and by using such a carrier, high selectivity is stable for a long time. There is an advantage that can be maintained. More preferably, Vp 0.5 _{nm to 2.0 nm} of the carrier is 0.5 × 10 ^{−4 to} 6.0 × 10 ⁻⁴ cm ³ / g, more preferably Vp _{0.5 nm to 2.0 nm} of the carrier. Is 1.0 × 10 ^{−4 to} 5.0 × 10 ⁻⁴ cm ³ / g. In addition, when Vp _{0.5nm-2.0nm of} a support _| carrier exceeds the said upper limit, there exists a possibility that high selectivity may not be obtained, and there exists a possibility that sufficient activity may not be obtained conversely when it falls below a minimum.

(Catalyst component)
The catalyst of the present invention has a configuration in which a catalyst component containing at least silver (Ag), cesium (Cs), rhenium (Re), and tungsten (W) is supported on the above-described support.

  Among the catalyst components, silver mainly plays a role as a catalyst active component. Here, the silver content (supported amount) is not particularly limited, and may be supported in an amount effective for the production of ethylene oxide. The silver content (supported amount) is not particularly limited, but is preferably 1 to 30% by mass based on the mass of the ethylene oxide production catalyst (based on the total mass of the carrier and the catalyst component; the same applies hereinafter). Is 5 to 20% by mass. Within such a range, it is possible to efficiently catalyze the reaction of producing ethylene oxide by vapor phase oxidation of ethylene with a molecular oxygen-containing gas.

  Cesium (Cs) and rhenium (Re) generally act as silver reaction accelerators. These contents (supported amounts) are not particularly limited, and may be supported in an amount effective for producing ethylene oxide. The cesium content (supported amount) is not particularly limited, but is 500 to 5000 ppm, preferably 1000 to 4000 ppm, based on the mass of the ethylene oxide production catalyst. Within such a range, the reaction for producing ethylene oxide by vapor-phase oxidation of ethylene with a molecular oxygen-containing gas can be effectively promoted. The rhenium content (supported amount) is not particularly limited, but is 50 to 2000 ppm, preferably 100 to 1000 ppm, based on the mass of the catalyst for producing ethylene oxide. Within such a range, the reaction for producing ethylene oxide by vapor-phase oxidation of ethylene with a molecular oxygen-containing gas can be effectively promoted. In particular, rhenium is considered to be an important factor in terms of catalyst selectivity. For this reason, the selectivity of the catalyst can be effectively improved by controlling the amount of rhenium within the above range. When Re exceeds the above range, not only the selectivity is not increased, but also the reaction temperature needs to be increased, which may adversely affect the life performance.

  Tungsten (W) acts as an auxiliary promoter for rhenium. Thus, when each catalyst component interacts, the catalyst of the present invention can exhibit high selectivity. The content (supported amount) of tungsten (W) is not particularly limited, and it may be supported in an amount effective for the production of ethylene oxide. The content (supported amount) of tungsten is not particularly limited, but is preferably 10 to 2000 ppm, more preferably 50 to 1000 ppm, based on the mass of the catalyst for producing ethylene oxide. Within such a range, the effect of rhenium (the effect of improving the selectivity of the catalyst) can be promoted when ethylene oxide is produced by vapor-phase oxidation of ethylene with a molecular oxygen-containing gas.

  The catalyst of the present invention may contain other catalyst components in addition to the above catalyst components. Here, the other catalyst components are not particularly limited, and examples thereof include vanadium, chromium, manganese, cobalt, nickel, copper, niobium, molybdenum, tin, antimony, tantalum, bismuth, titanium, and zirconium. Further, the content (supported amount) of such other catalyst component is not particularly limited as long as the effect of the catalyst component according to the present invention is not impaired, but is preferably 10 to 1000 ppm based on the mass of the catalyst for producing ethylene oxide. .

(Catalyst production method)
Next, the catalyst for producing ethylene oxide of the present invention is produced using the carrier according to the present invention produced as described above, and the production method thereof is conventionally known except that the carrier as described above is used. It can be prepared according to a method for producing a catalyst for producing ethylene oxide. Hereinafter, preferred embodiments of the catalyst according to the present invention will be described. However, the present invention is not limited to the following preferred embodiments, and a catalyst can be produced by appropriately modifying or using the carrier according to the present invention in other known methods.

  First, the precursor of each catalyst component is dissolved in an appropriate solvent to prepare a catalyst precursor solution. Here, the precursor of each catalyst component is not particularly limited as long as it is dissolved in a solvent. For example, in the case of silver, for example, silver nitrate, silver carbonate, silver oxalate, silver acetate, silver propionate , Silver lactate, silver citrate, silver neodecanoate and the like. Of these, silver oxalate and silver nitrate are preferred. In the case of cesium, cesium nitrate, nitrite, carbonate, oxalate, halide, acetate, sulfate, perrhenate, tungstate and the like can be mentioned. Of these, cesium nitrate, cesium perrhenate, and cesium tungstate are preferable. In the case of rhenium, examples thereof include ammonium perrhenate, sodium perrhenate, potassium perrhenate, perrhenic acid, rhenium chloride, rhenium oxide, cesium perrhenate, and the like. Of these, ammonium perrhenate and cesium perrhenate are preferred. In the case of tungsten, heteropolyacids such as tungsten oxide, tungstic acid, tungstate, phosphotungstic acid, silicotungstic acid and / or salts of heteropolyacids can be used. Of these, ammonium metatungstate, cesium metatungstate, ammonium paratungstate, cesium paratungstate, ammonium phosphotungstate, cesium phosphotungstate, ammonium silicotungstate, and cesium silicotungstate are preferred. Each of the above catalyst components may be used alone or in the form of a mixture of two or more. Moreover, the addition amount of each said catalyst component can be suitably determined so that it may become the above-mentioned predetermined catalyst composition.

  The solvent that dissolves the precursor of each catalyst component is not particularly limited as long as it can dissolve each catalyst component. Specific examples include water, alcohols such as methanol and ethanol, and aromatic compounds of toluene. Of these, water and ethanol are preferred.

  Here, the catalyst precursor solution may further contain a complexing agent for forming a complex, if necessary, in addition to the catalyst component. The complexing agent is not particularly limited, and examples thereof include monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and propylenediamine. The complexing agent may be used alone or in the form of a mixture of two or more.

  Next, the support prepared as described above is impregnated with the catalyst precursor solution thus prepared. Here, the catalyst precursor solution may be prepared separately for each catalyst precursor solution and impregnated on the support sequentially, or each catalyst precursor may be dissolved in one solvent to form one catalyst precursor solution. The carrier may be impregnated with this.

  Subsequently, the impregnated carrier is dried and fired. Drying is preferably performed at a temperature of 80 to 120 ° C. in an atmosphere of air, oxygen, or an inert gas (for example, nitrogen) under reduced pressure if necessary. The firing is performed in an atmosphere of air, oxygen, or an inert gas (for example, nitrogen) at a temperature of 100 to 800 ° C., preferably at a temperature of 100 to 600 ° C. for 0.1 to 100 hours, preferably 0. .1 to about 10 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 100 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 800 ° C. for 0.1 to 10 hours in an inert gas (eg, nitrogen, helium, argon, etc.) atmosphere. Good.

  The catalyst of the present invention thus obtained is excellent in selectivity and catalyst life (durability). Therefore, by using the catalyst for producing ethylene oxide of the present invention, ethylene oxide can be produced with high selectivity over a long period of time, which is very useful industrially.

  Therefore, the present invention also provides a method for producing ethylene oxide in which ethylene is vapor-phase oxidized using a molecular oxygen-containing gas in the presence of the catalyst of the present invention.

(Method for producing ethylene oxide)
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, a reaction temperature of 150 to 300 ° C., preferably 180 to 280 ° C., a reaction pressure of 0.2 to 4 MPa, preferably 0.9 to 3 MPa, and a space velocity of 1, 000 to 30,000 hr ⁻¹ (STP), preferably 3,000 to 8,000 hr ⁻¹ (STP).

  The raw material gas to be brought into contact with the catalyst is 0.5 to 40% by volume of ethylene, 3 to 10% by volume of oxygen, 1 to 30% by volume of carbon dioxide, the remaining inert gas such as nitrogen, argon and water vapor, methane, ethane, etc. And those containing 0.1 to 10 ppm by volume of an organic chlorine compound such as ethyl chloride, ethylene dichloride, vinyl chloride, and methyl chloride as a reaction inhibitor. 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 as long as the effects of the present invention are achieved. Below, each measuring method used for the Example and the comparative example is demonstrated.

(Measurement of specific surface area of carrier)
After pulverizing the carrier, about 0.2 g 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 alkali metal and silica (SiO ₂ ) content in support)
This was performed using fluorescent X-ray analysis. RIX2000 manufactured by RIGAKU was used as a measuring apparatus, and measurement was performed by a fundamental parameter method (FP method).

(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 was put in a drier kept at 120 ° C., and the mass when reaching a constant weight was measured (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.

（実施例１）
以下に、触媒Ａの調製手順を示す。シュウ酸銀２０ｇ、硝酸セシウム０．２１３６ｇ、過レニウム酸アンモニウム０．０４５７ｇ、メタタングステン酸アンモニウム０．０３０８ｇを、１０ｇの水に溶解し、さらに錯化剤としてエチレンジアミン６．８ｍｌを加え、触媒前駆体溶液Ａを調製した。

Example 1
Below, the preparation procedure of the catalyst A is shown. 20 g of silver oxalate, 0.2136 g of cesium nitrate, 0.0457 g of ammonium perrhenate and 0.0308 g of ammonium metatungstate are dissolved in 10 g of water, and 6.8 ml of ethylenediamine is further added as a complexing agent. Solution A was prepared.

This catalyst precursor solution A was mixed with carrier A (α-alumina carrier, SiO ₂ content = 1.91% by mass, Na ₂ O content = 0.19% by mass, water absorption = 37.1%, Hg method fine Pore volume = 0.40 ml / g, Vp _{0.5 nm} - _{2.0 nm} = 2.09 × 10 ⁻⁴ cm ³ / g, specific surface area of raw material α-alumina powder = 1.07 m ² / g, raw material α- After impregnating 52.2 g of alumina powder (Vp _{0.5 nm to 2.0 nm} = 2.69 × 10 ⁻⁴ cm ^{3 /} g), it was dried under reduced pressure at 90 ° C. This was heat-treated at 300 ° C. for 0.25 hours in an air stream, and then heat-treated at 570 ° C. for 3 hours in a nitrogen stream to obtain a catalyst (A).

  The content of each component of the catalyst (A) thus prepared (catalyst mass standard) was: Ag (silver equivalent) = 14.8 mass%, Cs (Cs equivalent) = 2350 mass ppm, Re (Re Conversion) = 460 mass ppm, W (W conversion) = 360 mass ppm.

(Example 2)
Below, the preparation procedure of the catalyst B is shown. 20 g of silver oxalate, 0.1709 g of cesium nitrate, 0.0457 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in 10 g of water, and 6.8 ml of ethylenediamine is further added as a complexing agent. Solution B was prepared.

This catalyst precursor solution B was mixed with carrier B (α-alumina carrier, SiO ₂ content = 0.69% by mass, Na ₂ O content = 0.03% by mass, water absorption = 39.5%, Hg method fine Pore volume = 0.40 ml / g, Vp _{0.5 nm to 2.0 nm} = 3.75 × 10 ⁻⁴ cm ³ / g, specific surface area of raw material α-alumina powder = 1.96 m ² / g, raw material α- After impregnating 52.2 g of alumina powder (Vp _{0.5 nm to 2.0 nm} = 4.96 × 10 ⁻⁴ cm ^{3 /} g), it was dried under reduced pressure at 90 ° C. This was heat-treated at 300 ° C. for 0.25 hours in an air stream, and then heat-treated at 570 ° C. for 3 hours in a nitrogen stream to obtain a catalyst (B).

  The content of each component of the catalyst (B) thus prepared (catalyst mass standard) was: Ag (silver equivalent) = 14.8 mass%, Cs (Cs equivalent) = 1880 mass ppm, Re (Re Conversion) = 460 mass ppm, W (W conversion) = 360 mass ppm.

(Comparative Example 1)
The preparation procedure of catalyst C is shown below. 20 g of silver oxalate, 0.2350 g of cesium nitrate, 0.0457 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in 10 g of water, and 6.8 ml of ethylenediamine is further added as a complexing agent. Solution C was prepared.

This catalyst precursor solution C was mixed with carrier C (α-alumina carrier, SiO ₂ content = 0.85% by mass, Na ₂ O content = 0.09% by mass, water absorption = 41.1%, Hg method fine Pore volume = 0.40 ml / g, Vp _{0.5 nm to 2.0 nm} = 8.54 × 10 ⁻⁴ cm ³ / g, specific surface area of raw material α-alumina powder = 4.26 m ² / g, raw material α- After impregnating 52.2 g of alumina powder (Vp _{0.5 nm to 2.0 nm} = 10.2 × 10 ⁻⁴ cm ^{3 /} g), it was dried under reduced pressure at 90 ° C. This was heat-treated at 300 ° C. for 0.25 hours in an air stream, and then heat-treated at 570 ° C. for 3 hours in a nitrogen stream to obtain a catalyst (C).

  The content of each component of the catalyst (C) thus prepared (catalyst mass standard) was: Ag (silver equivalent) = 14.8 mass%, Cs (Cs equivalent) = 2580 mass ppm, Re (Re Conversion) = 460 mass ppm, W (W conversion) = 360 mass ppm.

  Example 1 and 2 and Comparative Example 1 Supports a pore volume with a pore diameter of 0.5 to 2.0 nm and a Hg method pore volume, and selectivity to ethylene oxide when the catalyst is used in the reaction. The reaction temperatures are shown in Table 1. Further, FIG. 1 shows integral display of the data of the method A pore volume of the carriers according to Examples 1 and 2 and Comparative Example 1.

(Catalyst performance evaluation)
The catalysts (A) to (C) produced in Examples 1 and 2 and Comparative Example 1 were each crushed to 0.6 to 0.85 mm. Next, 3.0 g of the crushed catalyst was charged into a heating type double tube stainless steel reactor having an inner diameter of 5 mm and a tube length of 300 mm, respectively, and this packed bed was 24% by volume of ethylene and 7.0% by volume of oxygen. %, Carbon dioxide 2.0 volume%, ethyl chloride 2.6 volume ppm, the balance of nitrogen was introduced, and the ethylene conversion rate was about 11 mol% at 1.6 MPa and a space velocity of 5500 hr ^−1. The reaction was carried out as follows. According to the following formula 2 and formula 3, the conversion rate (formula 2) and the selectivity (formula 3) during ethylene oxide production were calculated. The performance of each catalyst is shown in Table 1 below.

  The present invention provides a catalyst used in a technique for producing ethylene oxide by oxidizing ethylene, and also provides a method capable of producing ethylene oxide.

Claims (4)

The pore volume with a pore diameter of 0.5 to 2.0 nm calculated by the SF method analysis from the argon adsorption isotherm measured at the liquid nitrogen temperature is 0.1 × 10 ^{−4 to} 8.0 × 10 ⁻⁴ cm ^3. The catalyst for ethylene oxide production obtained by carrying | supporting the catalyst component containing silver (Ag), cesium (Cs), rhenium (Re), and tungsten (W) on the support | carrier which is / g. The catalyst for ethylene oxide production according to claim 1, wherein the carrier contains α-alumina and silica. The raw material of the α-alumina has a pore volume of 0.1 × 10 ⁻⁴ to 10 with a pore diameter of 0.5 to 2.0 nm calculated by SF method analysis from an argon adsorption isotherm measured at liquid nitrogen temperature. The method for producing an ethylene oxide production catalyst according to claim 1, wherein the α-alumina powder is 0.0 × 10 ⁻⁴ cm ³ / g. A method for producing ethylene oxide, wherein ethylene is converted to ethylene oxide using the catalyst according to claim 1.

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