JP2010234264A - Catalyst for producing ethylene oxide and method for producing ethylene oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for producing ethylene oxide which is excellent in catalyst selectivity and the life of a catalyst (durability). <P>SOLUTION: The catalyst for producing ethylene oxide carries a catalytic component, which contains silver (Ag), cesium (Cs), rhenium (Re) and molybdenum (Mo), on a carrier which is 1.0-3.0 m<SP>2</SP>/g in specific surface area and contains 0.1-1.0 mass% of Si (as SiO<SB>2</SB>) and 0.001-0.15 mass% of Na (as Na<SB>2</SB>O). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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.

For example, paying attention to a catalyst component, a technique for improving the selectivity of a catalyst by using an alkali metal and rhenium in combination as an accelerator is disclosed (Patent Documents 1 and 2). Patent Document 1 discloses a catalyst composition for producing ethylene oxide containing, as a catalyst component, rhenium / a compound thereof and another metal / a compound thereof such as an alkali metal, and a support having a surface area of less than 20 m ² / g. The In Patent Document 2, silver metal, rhenium, tungsten, molybdenum / a compound thereof, and a component obtained by substituting a part of rubidium or cesium with potassium are deposited on a carrier having a surface area of 500 m ² / kg or more. A catalyst composition for producing ethylene oxide is disclosed.

On the other hand, a technique for improving the activity and selectivity of a catalyst has been disclosed by paying attention to a carrier in a catalyst using silver or rhenium as a catalyst component (Patent Documents 3 and 4). In Patent Document 3, attention is paid to the fact that the pore size distribution and the properties of the pore volume provided by the pores of the carrier, particularly those having a pore size within a specific range, play an important role, and at least 1 m ² / g The surface area and pores having a diameter in the range of 0.2 μm to 10 μm represent at least 70% of the total pore volume, and the pores together represent at least 0.27 ml / Disclosed is a catalyst comprising silver deposited on a support having a pore size distribution that provides g pore volume, in an amount of at least 10 g / kg based on the weight of the catalyst. Patent Document 4 discloses that, in an ethylene oxide production catalyst containing silver (Ag), cesium (Cs), and rhenium (Re) as catalyst components, by adjusting the content of Si and Na components in the carrier, Re The selectivity can be improved by enhancing the cocatalyst action of the catalyst, and the specific surface area is 0.6 to 3.0 m ² / g as the carrier and ₂ to 50 in terms of SiO ₂ / Na ₂ O. The use of certain carriers is disclosed.

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

  The above-mentioned Patent Documents 1 and 2 focus on rhenium as a co-catalyst and focus on improving the selectivity of the catalyst. However, a catalyst to which rhenium has been added has a problem in terms of durability of the catalyst because the oxidation state of rhenium, migration and aggregation are likely to occur. In Patent Documents 1 and 2, the selectivity of the catalyst is claimed without mentioning this problem at all.

In Patent Document 3, a carrier having a surface area of at least 1 m ² / g and a pore having a diameter ranging from 0.2 μm to 10 μm corresponds to at least 70% of the total pore volume is used as the carrier. The Here, the surface area of the carrier is most preferably 1.6 to 2.2 m ² / g (paragraph “0022”). However, such a large surface area is effective for supporting silver. However, when rhenium is used as a catalyst component, the catalyst component may move depending on the catalyst composition, and the durability of the catalyst is significantly reduced. To do.

Furthermore, in Patent Document 4, from the viewpoint of improving the selectivity of the catalyst, the Na content in the support is usually 0.05 to 0.50 wt%, preferably 0.16 to 0.45 wt in terms of Na ₂ O. % (Claim 3, paragraph “0016”). However, at such Na content, the movement of a small amount of sodium component from the inside of the support to the surface, which proceeds with the catalytic reaction, changes the interaction between silver on the catalyst surface and the promoter, and depending on the catalyst composition, There is a problem of causing a sharp drop in selectivity and activity.

  Therefore, although development of a catalyst for ethylene oxide production that sufficiently satisfies both catalyst selectivity and catalyst life (durability) is desired, it has not been realized yet.

  Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst for producing ethylene oxide which is excellent in catalyst selectivity and catalyst life (durability).

  Another object of the present invention is to provide a method for producing ethylene oxide using the above catalyst.

  As a result of intensive studies to solve the above problems, the present inventors have found that the ratio of the carrier used in the catalyst containing silver, cesium (Cs), rhenium (Re) and molybdenum (Mo) as catalyst components. By controlling the surface area, silicon (Si) content and sodium (Na) content to specific ranges, it is possible to obtain a catalyst for ethylene oxide production that sufficiently satisfies both selectivity and catalyst life (durability). The headline and the present invention were completed.

That is, the above-mentioned purpose is that the specific surface area is 1.0 to 3.0 m ² / g, the Si content (SiO ₂ conversion) is 0.1 to 1.0% by mass, and the Na content (Na ₂ O conversion). It is achieved by an ethylene oxide production catalyst comprising a carrier having a content of 0.001 to 0.15% by mass and carrying a catalyst component containing silver (Ag), cesium (Cs), rhenium (Re) and molybdenum (Mo). The

  The above object can also be achieved by a method for producing ethylene oxide, which comprises vapor-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of the catalyst of the present invention.

  The ethylene oxide production catalyst of the present invention is excellent in selectivity and catalyst life (durability). For this reason, by using the catalyst of the present invention, ethylene oxide can be produced with high selectivity over a long period of time.

In the present invention, the specific surface area is 1.0 to 3.0 m ² / g, the Si content (SiO ₂ conversion) is 0.1 to 1.0% by mass, and the Na content (Na ₂ O conversion) is 0.00. Provided is a catalyst for producing ethylene oxide, comprising a carrier of 001 to 0.15% by mass carrying a catalyst component containing silver (Ag), cesium (Cs), rhenium (Re) and molybdenum (Mo).

  In general, catalyst selectivity and catalyst life are in conflict. For this reason, as described above, it has been difficult to realize an ethylene oxide production catalyst that is excellent in both selectivity and catalyst life (durability). is there. The production scale of ethylene oxide is very large at 18 million tons per year. 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 superior catalyst performance (selectivity and durability) has been a continuous theme for researchers in the technical field.

  In the field of catalysts, it is generally known that the catalyst exhibits different performances depending on the combination of the physical properties and composition of the support and the types and amounts of the catalyst components. It is difficult. Here, the selectivity of the catalyst containing silver, cesium (Cs) and rhenium (Re) (Ag / Cs / Re catalyst) is improved as compared with the catalyst containing silver and Cs (Ag / Cs catalyst). Further, a catalyst (Ag / Cs / Re / Mo catalyst) obtained by adding molybdenum (Mo), which is an auxiliary promoter for Re, to the above catalyst improves the selectivity, particularly the initial selectivity. However, such an Ag / Cs / Re / Mo catalyst has a problem in terms of durability because the deterioration rate becomes very fast as compared with an Ag / Cs / Re catalyst not containing Mo. As a result of intensive studies to solve the above problems, the present inventors have found an optimal carrier composition for an Ag / Cs / Re / Mo catalyst. By using the support, even with an Ag / Cs / Re / Mo catalyst, the deterioration rate can be significantly reduced and the life of the catalyst can be improved.

That is, the catalyst of the present invention contains silver, cesium (Cs), rhenium (Re) and molybdenum (Mo) as catalyst components. For this reason, the catalyst of the present invention can achieve excellent selectivity. Further, as the carrier, specific surface area 1.0~3.0m ² / g, Si content (SiO ₂ equivalent) 0.1 to 1.0 wt%, and Na content (Na ₂ O equivalent) 0 A carrier that is 0.001 to 0.15% by weight is used. Among the catalyst components, rhenium and molybdenum have an effect of inducing catalyst deterioration. By using such a carrier, it is possible to suppress / prevent a decrease in catalyst performance. The mechanism by which such an effect can be achieved is unknown, but is presumed as follows. The present invention is not limited by the following estimation. That is, in a catalyst containing rhenium, when used for a long period of time, rhenium and molybdenum move or aggregate in the catalyst, or a state change occurs in which the valence of the catalyst changes, resulting in a decrease in catalyst performance. However, when the carrier as described above is used, the catalyst component is supported on a carrier having a relatively large surface area, so that the dispersibility of the catalyst component is kept good and excellent initial performance can be obtained. On the other hand, when the surface area becomes too small, there is a problem that the dispersibility of the catalyst component is lowered and it is difficult to carry the catalyst sufficiently. Also, it is assumed that rhenium interacts with cesium on the catalyst and exists in the form of cesium perrhenate. In fact, when the catalysts were examined, agglomerates of cesium perrhenate were often generated in the catalyst after the reaction. On the other hand, in the carrier according to the present invention, the silica, and a small amount of sodium in the carrier interact with the cation component and the anion component in the catalyst, so that aggregation, movement, and state change of rhenium and molybdenum are suppressed. It is estimated that the degree of performance deterioration is small.

  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.

  Embodiments of the present invention will be described below. In the present specification, “mass” and “weight”, “mass%” and “wt%”, and “part by mass” and “part by weight” are synonymous, and there are no particular restrictions on the measurement of physical properties and the like. When there is not, it measures at room temperature (20-25 degreeC) / relative humidity 40-50%. Further, “ppm” is “mass ppm” unless otherwise specified.

In the present invention, the carrier composition has α-alumina as a main component, silicon (Si) in an amount of 0.1 to 1.0% by mass in terms of SiO ₂ , and sodium (Na) in an amount of 0.001 in terms of Na ₂ O. If it contains -0.15 mass%, it will not restrict | limit in particular. In addition, both Si content and Na content are based on the total mass of the support of 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. Although it does not restrict | limit especially as another component, For example, an alkali metal (except Na), an alkaline-earth metal, these oxides, a transition metal, this oxide, etc. are mentioned. 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% by mass or less (the lower limit is 0% by mass). The alkaline earth metal content (as oxide) is preferably 0 to 5% by mass, more preferably 0.001 to 0.5% by mass, based on 100% by mass of the total mass of the carrier. It is. The transition metal content (as oxide) is preferably 0.001 to 1.0% by mass with respect to 100% by mass of the total mass of the carrier.

The specific surface area (BET specific surface area) of the carrier is 1.0 to 3.0 m ² / g. By using such a carrier, there is an advantage that the catalyst component such as rhenium and molybdenum can be suppressed / prevented and a decrease in performance can be suppressed while supporting a sufficient amount of the catalyst component. Preferably, the specific surface area (BET specific surface area) of the carrier is 1.0 to 3.0 m ² / g, more preferably 1.2 to 2.0 m ² / g. In addition, when the specific surface area of a support | carrier is less than the said minimum, water absorption rate cannot fully be ensured and there exists a possibility that loading of a catalyst component may become difficult. Conversely, when the specific surface area of the support exceeds the above upper limit, the catalyst component moves due to thermal degradation or the like, and the supported state of the catalyst during the reaction is likely to change compared to before the reaction. There is a risk that the degree of decrease will increase. In the present specification, “specific surface area” represents a BET specific surface area. Here, "BET specific surface area" E. T. T. Specifically, it is a value measured in the following examples.

Carrier, silicon (Si), 0.1 to 1.0 mass% in terms of SiO _2, including. By including silicon in such an amount, it is possible to suppress and prevent a decrease in the catalytic function of rhenium and molybdenum, 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 1.0% by mass, preferably 0.5 to 1.0% by mass with respect to 100% by mass of the total mass of the carrier. . 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.

Further, the carrier, sodium (Na), from 0.001 to 0.15% by mass in terms of Na ₂ O, including. By including sodium in such an amount, there is an advantage that deterioration in catalyst performance can be suppressed / prevented. Preferably, the Na content (in terms of Na ₂ O) in the carrier is 0.001 to 0.045% by mass, more preferably 0.001% by mass or more and 0.05% with respect to 100% by mass of the total mass of the carrier. It is less than mass%, even more preferably 0.001 to 0.045 mass%, particularly preferably 0.005 to 0.045 mass%, and most preferably 0.01 to 0.04 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.

  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 and PW2404 manufactured by PHILIPS can be used as a measuring apparatus, and measurement can be performed by the fundamental parameter method (FP method) and the calibration curve method.

  The shape of the carrier is not particularly limited, and conventionally known knowledge can be appropriately referred to in addition to a ring shape, a spherical shape, a cylindrical shape, and a pellet shape. Moreover, there is no restriction | limiting in particular also about the size (average diameter) of a support | carrier, Preferably it is 3-20 mm, More preferably, it is 4-10 mm.

  The 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 further preferably 0.3 to 0.6 mL. / G. If the 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 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. As the pore volume value of the carrier, a carrier deaerated at 200 ° C. for at least 30 minutes by a mercury intrusion method is used as a sample, and Autopore III9420W (manufactured by Shimadzu Corporation) is used as a measuring device. A value measured at a pressure range of ˜60,000 psia and 60 measurement points shall be adopted.

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

  Although there is no restriction | limiting in particular also about the water absorption rate of a support | carrier, Preferably it is 10 to 70%, More preferably, it is 20 to 60%, More preferably, it is 30 to 50%. If the water absorption rate of the carrier is 10% or more, the catalyst component can be easily supported. On the other hand, if the water absorption rate of the carrier is 70% or less, the strength of the carrier can be ensured to a practical level. In addition, as a value of the water absorption rate of the carrier, a value obtained by a method described in Examples described later is adopted.

  The catalyst of the present invention has a structure in which a catalyst component containing at least silver (Ag), cesium (Cs), rhenium (Re), and molybdenum (Mo) 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 3000 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.

  Molybdenum (Mo) acts as an auxiliary promoter for rhenium. Thus, when each catalyst component interacts, the catalyst of the present invention can exhibit high selectivity. The molybdenum (Mo) content (loading amount) is not particularly limited, and may be supported in an amount effective for the production of ethylene oxide. The molybdenum content (supported amount) is not particularly limited, but is preferably 10 to 500 ppm, more preferably 30 to 300 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, tungsten, 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. . In addition, it is preferable that the said catalyst component does not contain alkali metals other than cesium substantially, More preferably, content (in oxide conversion) of alkali metals other than cesium is 5 ppm or less on the mass basis of the catalyst for ethylene oxide manufacture. (The lower limit is 0 ppm).

  The catalyst for producing ethylene oxide of the present invention can be prepared according to a conventionally known method for producing a catalyst for producing ethylene oxide, except that the above-described carrier is used. Hereinafter, preferred embodiments of the method for producing a catalyst of 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.

  The method for preparing the carrier according to the present invention is not particularly limited. For example, the carrier composition can be controlled by employing the following preparation method. That is, 1) a method of adding a pore-forming agent having a desired size and amount to a mother powder mainly composed of α-alumina, and 2) preparing at least two kinds of mother powders having different physical properties at a desired mixing ratio. 3) a method of firing the carrier at a desired temperature for a desired time, and the like. In addition, although these methods may be used independently, you may combine these suitably. These preparation methods are described in, for example, “Characteristics of Porous Materials and Their Application Technologies”, supervised by Satoshi Takeuchi, published by Fuji Techno System Co., Ltd. (1999). Reference can also be made to JP-A-5-329368, JP-A-2001-62291, JP-A-2002-136868, JP-A-2984740, JP-A-3256237, JP-A-3295433, and the like. Alternatively, the carrier having a specific composition according to the present invention may be obtained by ordering from the carrier manufacturer.

  Hereinafter, preferred embodiments of the method for preparing the carrier according to the present invention will be described. However, the present invention is not limited to the following preferred embodiments, and the carrier according to the present invention can be produced by appropriately modifying or by other known methods.

  An α-alumina powder containing at least α-alumina as a main component and a binder, a silicon compound as a raw material for providing silica, other pore forming agents, and an appropriate amount of water are added and kneaded sufficiently, followed by an extrusion forming method. After forming into a predetermined shape, for example, a spherical shape, a pellet shape, etc., etc., it is dried as necessary, and calcined in an inert gas such as helium, nitrogen, argon and / or a gas atmosphere such as air, etc. The body is obtained.

  The α-alumina powder constituting the carrier containing α-alumina as a main component has a purity of 90% or more, preferably 95% or more, more preferably 99% or more, particularly preferably 99.5% or more. Is used. The particle diameter of the α-alumina powder as the carrier material 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.

  In addition to the α-alumina powder, the carrier mainly composed of α-alumina is alumina oxide, particularly amorphous alumina, silica, silica aluminum, mullite, zeolite, etc. (these are referred to as “amorphous alumina”). Generic names); alkali metal oxides and alkaline earth metal oxides such as potassium oxide, sodium oxide and cesium oxide (these are generically referred to as “alkali 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 grasping the amount of sodium in the powder in advance, a carrier can be prepared by adding a sodium compound at the time of carrier preparation so as to obtain a specific amount of sodium.

Examples of the silicon compounds include covalently bonded compounds such as silicon oxide, silicon nitride, silicon carbide, silane, and silicon sulfide; such as sodium silicate, ammonium silicate, sodium aluminosilicate, ammonium aluminosilicate, sodium phosphosilicate, and ammonium phosphosilicate. Silicates; 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 SiO ₂ ) as described above is obtained.

  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, carboxymethyl cellulose, corn starch or an alkali metal salt thereof. Among these, it is preferable to use carboxymethylcellulose, sodium carboxymethylcellulose, and the like.

  A pore-forming agent is a material that is completely removed from the support during firing and added to the mixture so that controlled pores remain in the support. 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 precursor thus obtained is calcined at 1,000 to 1,800 ° C., preferably 1,400 to 1,700 ° C. in an inert gas such as helium, nitrogen and argon, and a gas atmosphere such as air. By doing so, the carrier according to the present invention can be produced.

  The surface area of the support may be adjusted so as to fall within the scope of the present invention by appropriately selecting the surface area of the powder mainly composed of α-alumina, the binder component, the firing temperature, and the like.

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 retrofitting a silicon compound or a compound containing sodium to the carrier containing SiO ₂ or Na ₂ O thus obtained. It is more preferable to add a sodium compound.

  Further, the shape of the support for the ethylene oxide production catalyst of the present invention is not particularly limited, and the shape of the support generally used for the preparation of the ethylene oxide production catalyst, for example, a ring shape, a saddle shape, a spherical shape, a pellet shape, etc. It can be appropriately selected in consideration of industrial points such as loss and strength.

  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 method for producing the catalyst of the present invention using the above-mentioned carrier 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 rhenium, examples thereof include ammonium perrhenate, sodium perrhenate, potassium perrhenate, perrhenic acid, rhenium chloride, rhenium oxide, and cesium perrhenate. Of these, ammonium perrhenate and cesium perrhenate are preferred. In the case of cesium, nitrates, nitrites, carbonates, oxalates, halides, acetates, sulfates, perrhenates, molybdates, and the like of cesium are included. Of these, cesium nitrate, cesium perrhenate, and cesium molybdate are preferable. In the case of molybdenum, examples include molybdenum oxide, molybdic acid, molybdate, and other heteropolyacids such as silicomolybdic acid and phosphomolybdic acid and / or salts of heteropolyacid. Of these, ammonium paramolybdate, cesium paramolybdate, ammonium phosphomolybdate, cesium phosphomolybdate, ammonium silicomolybdate, and cesium silicomolybdate 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 obtain one catalyst precursor solution. And this may be impregnated into the carrier.

  Subsequently, the 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. It is preferable to carry out for about 1 to 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 a nitrogen 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 process for producing ethylene oxide, which comprises vapor-phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of the catalyst of the present invention.

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

For example, general conditions on an industrial production scale, that is, a reaction temperature of 150 to 300 ° C., preferably 180 to 280 ° C., a reaction pressure of 0.2 to 4 MPa, preferably 0.5 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) is employed. 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 alkyl chloride such as ethyl chloride, ethylene dichloride, vinyl chloride and methyl chloride as reaction inhibitors. Examples of the molecular oxygen-containing gas used in the production method of the present invention include air, oxygen, and enriched air.

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

<Measurement of specific surface area of carrier>
After pulverizing the carrier, about 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. Measurement was performed by a calibration curve method using PW2404 manufactured by PHILIPS as a measuring apparatus.

<Measurement of content (supported amount) of alkali metal, rhenium, molybdenum and silver in the catalyst>
The same fluorescent X-ray analysis method as described above was used.

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

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

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

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

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

Example 1: Preparation of catalyst A 20 g of silver oxalate, 0.1645 g of cesium nitrate, 0.0359 g of ammonium perrhenate, 0.0107 g of ammonium paramolybdate tetrahydrate were dissolved in 10 g of water and further complexed. 6.8 ml of ethylenediamine was added as an agent to prepare catalyst precursor solution A.

This catalyst precursor solution A was mixed with carrier A (α-alumina carrier, specific surface area = 1.64 m ² / g, SiO ₂ content = 0.69% by mass, Na ₂ O content = 0.038% by mass, water absorption After impregnating 52.2 g (rate = 39.5%, pore volume = 0.40 ml / g, average pore diameter = 0.91 μm), 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 basis) was: Ag (silver equivalent) = 14.8 mass%, Cs (Cs equivalent) = 1870 mass ppm, Re (Re Conversion) = 360 mass ppm, and Mo (Mo conversion) = 100 mass ppm.

Comparative Example 1: Preparation of Catalyst B 20 g of silver oxalate, 0.2136 g of cesium nitrate, 0.0457 g of ammonium perrhenate, and 0.0107 g of ammonium paramolybdate tetrahydrate were dissolved in 10 g of water and further complexed. 6.8 ml of ethylenediamine was added as an agent to prepare catalyst precursor solution B.

This catalyst precursor solution B was mixed with carrier B (α-alumina carrier, specific surface area = 0.87 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O content = 0.179 mass%, water absorption After impregnating 52.2 g (rate = 39.1%, pore volume = 0.35 ml / g, average pore diameter = 1.83 μm), 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) = 2430 mass ppm, Re (Re Conversion) = 480 mass ppm, and Mo (Mo conversion) = 100 mass ppm.

Comparative Example 2: Preparation of Catalyst C A catalyst (C) was obtained in the same manner as in Comparative Example 1, except that the amount of ammonium perrhenate added was changed from 0.0457 g to 0.0359 g.

  The content of each component of the catalyst (C) thus prepared (catalyst mass basis) was: Ag (silver equivalent) = 14.8 mass%, Cs (Cs equivalent) = 2430 mass ppm, Re (Re Conversion) = 370 mass ppm, and Mo (Mo conversion) = 100 mass ppm.

[Catalyst performance evaluation]
The catalysts (A) to (C) produced in Example 1 and Comparative Examples 1 and 2 were each crushed to 600 to 850 μm. Next, 1.20 g of the crushed catalyst was charged into a heating type double tube stainless steel reactor each having an inner diameter of 3 mm and a tube length of 300 mm, and this packed bed was filled with 30% ethylene and 7.6% oxygen. %, Carbon dioxide 2.0% by volume, ethyl chloride 2.4 ppm, the balance of methane, nitrogen, argon and ethane was introduced, and the ethylene conversion was 0.8 MPa at a space velocity of 5500 hr ^−1. The reaction was carried out so that the concentration was about 8.3 mol%. The selectivity at the start of the reaction and the reaction temperature (initial performance), the selectivity after the reaction for 120 hours and the reaction temperature (the performance after 120 hours) are converted into the conversion rate during the production of ethylene oxide (Formula 2) according to the following formulas 2 and 3. ) And selectivity (Formula 3) were calculated. The initial performance and performance after 120 hours are shown in Table 1 below.

  From the results shown in Table 1 above, the catalyst A of the present invention is not only high in initial selectivity and activity as compared with the catalyst B and catalyst C, but also selected after 120 hours (5 days) of reaction. It can be seen that there is no decrease in rate.

  Further, regarding the catalyst A of the present invention, the selectivity and reaction temperature after 600 hours (25 days) were measured under the same conditions as described in the above-mentioned catalyst performance evaluation. The selectivity was 91.9%. The reaction temperature is 255 ° C., and it can be seen that the catalyst A of the present invention maintains high activity and does not show a decrease in selectivity even after the reaction for 600 hours (25 days). Regarding the catalysts B and C, the performance of the catalyst was severely deteriorated after 120 hours (5 days) of the reaction.

  From the above results, according to the present invention, a catalyst for producing ethylene oxide having excellent activity and selectivity can be provided, and according to the method for producing ethylene oxide using the catalyst, ethylene oxide can be produced with high selectivity. It is considered that there is.

Claims (3)

The specific surface area is 1.0 to 3.0 m ² / g, the Si content (SiO ₂ conversion) is 0.1 to 1.0% by mass, and the Na content (Na ₂ O conversion) is 0.001 to 0.00. A catalyst for producing ethylene oxide, comprising a carrier of 15% by mass carrying a catalyst component containing silver (Ag), cesium (Cs), rhenium (Re) and molybdenum (Mo). The catalyst for ethylene oxide production according to claim 1, wherein the Na content (Na ₂ O conversion) is 0.001% by mass or more and less than 0.05% by mass.   A method for producing ethylene oxide, comprising vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of the catalyst according to claim 1.