JP2012072096A - Method of producing ethylene oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique in which the concentration of a reaction accelerator used for a reaction is controlled, and which can thereby raise the selectivity to ethylene oxide in a method in which under the presence of a silver catalyst, the contact vapor phase oxidation of ethylene by oxygen-containing gas is carried out to produce ethylene oxide.SOLUTION: The amount of a water-soluble alkali component contained in a catalyst, and a reaction accelerator concentration used for a reaction is controlled to become a specific relation, thereby ethylene oxide can be produced with the selectivity higher than that of an initial stage.

Description

  The present invention relates to a process for producing ethylene oxide from ethylene with high selectivity. Specifically, the present invention relates to a method for producing ethylene oxide from ethylene with high selectivity by optimally adjusting the concentration of the organic halide in the reaction gas.

  It is widely used industrially to produce ethylene oxide by catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst. As for the silver catalyst used for this catalytic gas phase oxidation, many techniques have been proposed regarding the additive component of the catalyst, the carrier, the supporting method, the kind of the reaction accelerator, etc. (Patent Document 1).

  When ethylene oxide is produced using a silver catalyst, after filling the reactor with the silver catalyst, an inert gas such as ethylene, oxygen, carbon dioxide, water and nitrogen, and / or lower hydrocarbons such as methane and ethane, etc. A gas containing a small amount of reaction accelerator is supplied. In general, organic chlorides such as ethyl chloride, vinyl chloride, ethylene dichloride, and methyl chloride are used as reaction accelerators, and the selectivity from ethylene to ethylene oxide is increased by controlling the concentration of the addition. It is known to change, and when changing the feed gas composition, gas concentration, or reaction temperature, techniques for changing the reaction accelerator concentration are disclosed (Patent Documents 2 and 3). Patent Document 2 discloses a method of determining the reaction accelerator concentration when the feed gas and / or reaction gas composition is changed and the reaction temperature is changed. On the other hand, Patent Document 3 discloses a method for determining the reaction accelerator concentration when the feed gas composition is changed.

Japanese Patent No. 2619660 Patent 4516313 Patent No. 4516751

  In the above method, it is difficult to say that high selectivity to ethylene oxide can be sufficiently achieved, and it is not sufficient to obtain high selectivity particularly from the initial stage of the reaction. The object of the present invention is to provide a process for producing ethylene oxide from ethylene with high selectivity from the reaction initiation stage.

  In general, when ethylene oxide is produced using a silver catalyst, an inert gas such as ethylene, oxygen, carbon dioxide, water, and nitrogen and methane, ethane, etc. The reaction is started by adding a small amount of a lower hydrocarbon or other organic halide as a reaction accelerator. At that time, since the high selectivity cannot be obtained unless the reaction accelerator concentration is optimized, it is necessary to adjust for each catalyst so as to obtain the highest possible selectivity. Since the reaction accelerator concentration varies from catalyst to catalyst, the work to find the optimum value is very laborious. However, if the operation is performed outside the optimum value, not only high selectivity but also durability can be obtained. There was also a problem with respect to the surface. The production scale of ethylene oxide is very large, so if high selectivity can be stably expressed from the initial stage of the reaction and high selectivity can be obtained for a long period of time, the amount of raw material ethylene used can be significantly saved, and its economic effect Is very big. Under these circumstances, a method for optimizing the reaction accelerator concentration is desired.

  As a result of intensive studies to solve the above problems, the present inventors have selected a high concentration from the initial stage of the reaction by determining the concentration of the reaction accelerator according to the concentration of the water-soluble alkali component contained in the catalyst. As a result, the present invention has been completed.

  Under the condition that the YX conditional expression of the following mathematical formula 1 is satisfied, the gas containing ethylene, molecular oxygen, and the reaction accelerator is converted into a catalytic gas phase using silver and a silver catalyst containing an alkali component containing a water-soluble alkali component. An ethylene oxide production method characterized in that it is oxidized to produce ethylene oxide.

Ｘ：水溶性アルカリ成分濃度［μｍｏｌ／ｇ−ｃａｔ］
Ｙ：反応促進剤濃度［ｍｏｌｐｐｍ］
Ａ：０．０１以上３未満
Ｂ：ガス組成により決定される定数

X: Water-soluble alkali component concentration [μmol / g-cat]
Y: Reaction accelerator concentration [molppm]
A: 0.01 or more and less than 3 B: Constant determined by gas composition

  The ethylene oxide production method of the present invention can produce ethylene oxide with high selectivity by optimally adjusting the reaction accelerator concentration according to the catalyst composition.

It is a figure which shows the relationship between X and Y obtained from the evaluation result of the catalyst. It is a figure which shows the selectivity to the reaction accelerator and ethylene oxide in catalyst performance evaluation 2.

  The present invention relates to a method for controlling the concentration of a reaction accelerator capable of obtaining a high selectivity in a process for producing ethylene oxide by catalytic vapor phase oxidation of ethylene with an oxygen-containing gas in the presence of a catalyst comprising at least silver, an alkali metal, and a support. I will provide a.

  Embodiments of the present invention will be described below. Unless otherwise specified, the physical properties are measured at room temperature (20 to 25 ° C.) / Relative humidity 40 to 50%. Further, “ppm” is “mass ppm” unless otherwise specified.

  In the ethylene oxide production method of the present invention, the reaction accelerator concentration Y [molppm] at which a high selectivity can be obtained is expressed as follows: Y = mol of water-soluble alkali component concentration [μmol / cat-g: μmol per 1 g of catalyst] When the relationship of AX + B is established (the value of B is a constant determined by the gas composition), the value of A represented by Formula 1 can be calculated as 0.01 or more and less than 3. The value of A is preferably 0.02 or more and less than 2, more preferably 0.03 or more and less than 1, and most preferably 0.05 or more and less than 0.6.

  The value B varies depending on the reaction conditions. By setting the value A within the range indicated by the present invention, high selectivity to ethylene oxide can be obtained regardless of the reaction conditions.

In order to obtain the YX conditional expression of Formula 1, it is preferable to perform the reaction under the following conditions.
(1) When producing ethylene oxide from a gas containing ethylene, molecular oxygen and a reaction accelerator in the presence of the silver catalyst, determining the concentration of the reaction accelerator that maximizes the ethylene oxide selectivity. However, react under the same conditions except changing the concentration of the reaction accelerator.
(2) Obtain the concentration of the reaction accelerator that maximizes the ethylene oxide selectivity in the same manner as in (1) except that the amount of the water-soluble alkali component in the silver catalyst is changed in (1).
(3) To illustrate the relationship between the amount of the water-soluble alkali component (X axis) in the silver catalyst obtained by repeating the above (2) and the concentration of the reaction accelerator (Y axis).
(4) The slope of the straight line obtained by the above (3) is A, the intercept is B, and the YX conditional expression of Formula 1 is obtained.

(Reactive gas)
The reaction gas used in the present invention is a gas containing ethylene, molecular oxygen and a reaction accelerator, and other components which may be contained include inert gases such as carbon dioxide, water, nitrogen and / or argon. Lower hydrocarbons such as ethane and / or methane. In the reaction gas, ethylene is 5 to 50% by volume, preferably 10 to 32% by volume, molecular oxygen is 2.5 to 25% by volume, preferably 5 to 16% by volume, and carbon dioxide is 1 to 15% by volume. %, Preferably 2 to 8% by volume, and the reaction accelerator is 0.1 to 100 molppm (mol · ppm), preferably 0.5 to 20 molppm. Further, these gases can be used after being diluted with an inert gas such as nitrogen and / or argon, methane and / or ethane, etc., so that the total amount of the gas becomes 100% by volume.

(Reaction accelerator)
As the reaction accelerator used in the present invention, organic halogen compounds, organic nitrogen compounds, nitrogen oxides and the like can be used, but organic halides are preferred. The organic halide includes fluoride, chloride, bromide, etc. Among them, organic chloride is preferable, and it is preferable to select methyl chloride, ethyl chloride, ethylene dichloride, vinyl chloride or a mixture thereof.

  The above reaction accelerator is used by adding a small amount to ethylene, oxygen, carbon dioxide, water, and other gases containing nitrogen, methane, ethane, etc. as dilution gases. May form the following compounds. When an organic halogen compound is used as a reaction accelerator, the greater the number of halogen atoms contained in one molecule, the stronger the action on the catalyst. Therefore, the concentration Y (mol ppm) of the reaction accelerator is the reaction modification. It is derived on the basis that the number of halogen atoms present per molecule of the agent is 1. For example, when the number of halogen atoms such as ethylene dichloride is 2, the reaction accelerator concentration can be calculated by halving.

(Catalyst component)
The catalyst used in the present invention is a solid catalyst comprising at least silver and an alkali metal. Here, the alkali metal is lithium, sodium, potassium, rubidium or cesium, preferably lithium, sodium or cesium. Of these, only one type of element may be added, or two or more types may be used in combination. The alkali metal is classified into water-soluble and insoluble alkali components. A water-soluble alkaline component is an alkaline component extracted into water. Note that the alkali component that is not extracted into water is an insoluble alkali component that is immobilized in the catalyst.

  In the case of sodium and cesium, the ratio of the water-soluble cesium concentration to the water-soluble sodium ratio is preferably 0.1 or more and less than 5. If it is less than 0.1, sufficient performance is often not obtained, and even if it is 5 or more, sufficient performance is often not obtained.

  The amount of the water-soluble alkali component can be calculated according to the following conditions. The solid catalyst containing a predetermined component is crushed into a size of 0.6 to 0.85 mm, and about 1 g is weighed. Thereafter, the weighed catalyst is put into an extraction glass cylinder, set in a Soxhlet extraction apparatus, and the catalyst component is extracted with 170 g of pure water for 2.5 hours. The extracted solution was filtered using a membrane filter having a pore size of 0.45 μm, and the alkali component concentration in the filtrate was measured by cation chromatography (manufacturer: Dionex DX-320, column: CS12A). The water-soluble alkali concentration [μmol / g-cat] is calculated.

  The water-soluble alkali component concentration [μmol / g-cat] is not particularly limited, but is preferably 1 to 50 μmol / g-cat, more preferably 3 to 40 μmol / g-cat. . When it is 50 μmol / g-cat or more, not only sufficiently high performance cannot be obtained, but also the reaction accelerator concentration becomes relatively high, which may adversely affect the catalyst life. Moreover, since it is insufficient for an alkali component as it is less than 1 micromol / g-cat, sufficient performance is often not obtained.

  In general, insoluble alkali components vary depending on the processing temperature during catalyst preparation and the constituent elements of the catalyst, so even if the prepared alkali components are the same catalyst, the water-soluble alkali component concentration and the insoluble alkali component concentration Are not the same. Further, depending on the preparation method, the concentration of the water-soluble alkali component changes, and the optimum reaction accelerator concentration changes accordingly, and it is determined after the catalyst preparation.

  The method for adding the alkali component is not particularly limited, and it may be added at the time of preparing the catalyst, or may be previously contained in the carrier.

  The catalyst used in the present invention is a solid catalyst comprising at least silver and an alkali metal, and is preferably used with a catalyst component supported on a carrier. As the carrier, alumina, silica, magnesia, zirconia, titania, calcium carbonate, silicon carbide, zeolite and the like can be used, and a carrier mainly composed of α-alumina is preferable. As the carrier component, in addition to α-alumina, silicon (Si), alkali metal and alkaline earth metal, oxides thereof, transition metals and oxides thereof can be used. These contents are not particularly limited, but the silicon content is 0.01 to 10% by mass, and the alkali metal and alkaline earth metal content is preferably 0 to 5 mass in terms of oxide. %, More preferably 0.01 to 4% by mass. The transition metal content is preferably 0.01 to 5% by mass in terms of oxide.

  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).

  There are water-soluble alkali metals contained in the catalyst component and the carrier.

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

The specific surface area (BET specific surface area) of the carrier is 0.2 to 5.0 m ² / g. By using such a carrier, a high selectivity can be expressed. Preferably, the support has a specific surface area (BET specific surface area) of 0.5 to 3.0 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. On the contrary, when the specific surface area of the carrier exceeds the above upper limit, isomerization reaction of ethylene oxide tends to occur, which is not preferable.

(Carrier)
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 support is not particularly limited, but is preferably 0.2 to 0.6 mL / g (pore volume: milliliter per 1 g of catalyst), more preferably 0.3 to 0.5 mL / g. . If the pore volume of the carrier is 0.2 mL / g or more, it is preferable in that the catalyst component can be easily supported. On the other hand, if the pore volume of the carrier is 0.6 mL / g or less, it is preferable in that the strength of the carrier can be ensured to a practical level. As the pore volume value of the carrier, a carrier deaerated at 200 ° C. for at least 30 minutes by a mercury intrusion method is used as a sample, and Autopore III9420W (manufactured by Shimadzu Corporation) is used as a measuring device. 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 method for preparing the carrier is not particularly limited. For example, the composition of the carrier can be controlled by adopting 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.

  Hereinafter, preferred embodiments of the method for preparing the carrier will be described.

  Add at least α-alumina powder and binder mainly composed of α-alumina, silicon compound as a raw material to provide silica, complete combustion agent, and appropriate amount of water, and knead well, then extrusion forming After forming into a predetermined shape, for example, a spherical shape, a pellet shape, etc. by a method, etc., the carrier is dried as necessary and calcined in an inert gas such as helium, nitrogen, and argon and / or a gas atmosphere such as air. A precursor 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 primary particle diameter of α-alumina is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.1 to 3 μm. The secondary particle size is not particularly limited, but is preferably 1 to 100 μm, more preferably 30 to 70 μm.

  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.

  Examples of the silicon compound 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.

  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 complete combustor 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 plastic (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 complete combustors.

  The carrier precursor thus obtained is calcined at 1,000 to 1,800 ° C., preferably 1,300 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 can be produced.

(Other catalyst components)
The catalyst used in the present invention has a configuration that is a solid catalyst containing at least silver (Ag) and other catalyst components in addition to the above-described alkali component. The specific form of the catalyst component is not particularly limited, and conventionally known knowledge can be appropriately referred to, but as the catalyst component, in addition to the above-described alkali component, at least silver, thallium, sulfur, chromium, niobium, titanium, Zirconium, vanadium, manganese, molybdenum, tungsten, rhenium, cobalt, nickel, copper, and the like can also be used. As for these catalyst components, only 1 type may be used independently and 2 or more types may be used together. Among these, it is preferable to use sulfur, niobium, molybdenum, tungsten, or rhenium.

  There is no restriction | limiting in particular about content of silver, an alkali component, and other catalyst components, What is necessary is just to carry | support with the quantity effective for manufacture of ethylene oxide. For example, in the case of silver, the supported amount is 1 to 30% by mass, preferably 5 to 25% by mass, based on the mass of the catalyst for producing ethylene oxide. The content of alkali components and / or other catalyst components (excluding silver and alkali components) is usually 10 to 20000 ppm by mass, preferably 50 to 15000 ppm by mass, based on the mass of the ethylene oxide production catalyst. More preferably, it is 100-12000 mass ppm.

(Catalyst preparation method)
Next, a method for preparing the catalyst used in the present invention will be described. First, the precursor of each catalyst component is dissolved in an appropriate solvent to prepare a catalyst precursor solution. The precursor of each catalyst component is not particularly limited as long as it is in a form that dissolves in a solvent. For example, when preparing a catalyst containing cesium as an alkali metal and rhenium as the other component in addition to silver, silver nitrate, silver carbonate, silver oxalate, silver acetate, silver propionate, silver lactate, Examples include acid silver and silver neodecanoate. Of these, silver oxalate and silver nitrate are preferred. Examples of the cesium precursor include cesium nitrate, nitrite, carbonate, oxalate, halide, acetate, and sulfate. Of these, cesium nitrate and cesium carbonate are preferred. Examples of rhenium precursors 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.

  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 such as 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 is impregnated with the catalyst precursor solution thus prepared. Here, the catalyst precursor solution may be prepared by preparing a precursor solution for each catalyst component and impregnating the support. Alternatively, all the precursors of each catalyst component may be dissolved in one solvent to form one catalyst precursor solution, which may be impregnated on the support.

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). The firing is performed in an atmosphere of air, oxygen, or an inert gas (for example, nitrogen) at a temperature of 150 to 700 ° C., preferably at a temperature of 200 to 600 ° C. for 0.1 to 100 hours, preferably 1 It is preferable to carry out for about 20 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 350 ° C. for 0.1 to 10 hours, and the second stage firing is performed in an air atmosphere at 250 to 450 ° C. for 0.1 to 10 hours. The conditions for 10 hours are mentioned. More preferably, after firing in such an air atmosphere, firing may be performed at 450 to 700 ° C. for 0.1 to 10 hours in an inert gas (eg, nitrogen, helium, argon, etc.) atmosphere. The method for producing ethylene oxide of the present invention can be carried out according to a conventional method except that the reaction accelerator concentration is optimized by the method of the present invention.

For example, general conditions on an industrial production scale, that is, a reaction temperature of 150 to 350 ° C., preferably 180 to 280 ° C., a reaction pressure of 0.2 to 4 MPaG, preferably 0.5 to 3 MPaG, and a space velocity of 1,000 to 30. , 000 hr ⁻¹ (STP), preferably 3,000 to 8,000 hr ⁻¹ (STP) is employed. As a raw material gas to be brought into contact with the catalyst, in addition to the reaction accelerator optimized in the present invention, ethylene 5 to 50% by volume, oxygen 2.5 to 25% by volume, carbon dioxide 1 to 15% by volume, the balance Nitrogen, water vapor, and lower hydrocarbons such as methane and ethane are included. The molecular oxygen-containing gas used in the present invention includes air, oxygen and enriched air.

  The effect of this invention is demonstrated using a following example. However, the technical scope of the present invention is not limited only to the following examples. The measurement of various parameters of the catalyst was performed by the following method.

<Measurement of specific surface area of carrier>
After pulverizing the carrier, about 1.0 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 SiO ₂ , Na ₂ O, Ag, Cs, Re, and W Content in Support>
Measured by fluorescent X-ray analysis.

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

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

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

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

  d) Using the W1 and W2 obtained above, the water absorption was calculated according to the following formula 2.

（触媒Ａの調製）
シュウ酸銀１４．６ｇ、硝酸セシウム０．２５６４ｇ、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、約１４ｍｌ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。

(Preparation of catalyst A)
14.6 g of silver oxalate, 0.2564 g of cesium nitrate, 0.0457 g of ammonium perrhenate, and 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. Catalyst precursor solution A was prepared.

This catalyst precursor solution A was mixed with carrier A (α-alumina carrier, specific surface area = 0.7 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O = 0.4 mass%, water absorption = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, the catalyst A was obtained by heat treatment at 550 ° C. for 3 hours in a nitrogen stream.

  The content (catalyst basis) of each component of the catalyst A thus prepared was: Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 2780 mass ppm, Re (Re conversion) = 450 It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst B)
14.6 g of silver oxalate, 0.2777 g of cesium nitrate, 0.0457 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. Catalyst precursor solution B was prepared.

This catalyst precursor solution B was mixed with carrier A (α-alumina carrier, specific surface area = 0.7 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O = 0.4 mass%, water absorption = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, it heat-processed for 3 hours at 550 degreeC in nitrogen stream, and the catalyst B was obtained.

  Thus, the content (catalyst reference) of each component of the catalyst B prepared was Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 3010 mass ppm, Re (Re conversion) = 450. It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst C)
14.6 g of silver oxalate, 0.2991 g of cesium nitrate, 0.0457 g of ammonium perrhenate, and 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. A catalyst precursor solution C was prepared.

This catalyst precursor solution C was mixed with carrier A (α-alumina carrier, specific surface area = 0.7 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O = 0.4 mass%, water absorption = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, the catalyst C was heat-treated at 550 ° C. for 3 hours in a nitrogen stream.

  The content (catalyst basis) of each component of the catalyst C prepared in this way is: Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 3240 mass ppm, Re (Re conversion) = 450 It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst D)
14.6 g of silver oxalate, 0.2564 g of cesium nitrate, 0.0457 g of ammonium perrhenate, and 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. A catalyst precursor solution D was prepared.

This catalyst precursor solution D was mixed with carrier B (α-alumina carrier, specific surface area = 0.8 m ² / g, SiO ₂ content = 2.1% by mass, Na ₂ O = 0.2% by mass, water absorption = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, it heat-processed for 3 hours at 550 degreeC in nitrogen stream, and the catalyst D was obtained.

  The content (catalyst basis) of each component of the catalyst D prepared in this way is: Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 2780 mass ppm, Re (Re conversion) = 450 It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst E)
14.6 g of silver oxalate, 0.2777 g of cesium nitrate, 0.0457 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. A catalyst precursor solution E was prepared.

This catalyst precursor solution E was mixed with carrier B (α-alumina carrier, specific surface area = 0.8 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O = 0.2 mass%, water absorption rate = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, it heat-processed at 550 degreeC for 3 hours in nitrogen stream, and the catalyst E was obtained.

  Thus, the content (catalyst basis) of each component of the catalyst E prepared was as follows: Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 3010 mass ppm, Re (Re conversion) = 450 It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst F)
14.6 g of silver oxalate, 0.1709 g of cesium nitrate, 0.0555 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. A catalyst precursor solution F was prepared.

This catalyst precursor solution F was mixed with support C (α-alumina support, specific surface area = 0.9 m ² / g, SiO ₂ content = 0.7 mass%, Na ₂ O = 0.1 mass%, water absorption rate = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, the catalyst F was heat-treated at 550 ° C. for 3 hours in a nitrogen stream.

  Thus, the content (catalyst reference) of each component of the catalyst F prepared was Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 1850 mass ppm, Re (Re conversion) = 550. It was mass ppm and W (W conversion) = 350 mass ppm.

(Preparation of catalyst G)
14.6 g of silver oxalate, 0.2136 g of cesium nitrate, 0.0555 g of ammonium perrhenate, 0.0308 g of ammonium metatungstate are dissolved in about 14 ml of water, and 6.8 ml of ethylenediamine is added as a complexing agent. A catalyst precursor solution G was prepared.

This catalyst precursor solution G was mixed with carrier D (α-alumina carrier, specific surface area = 0.9 m ² / g, SiO ₂ content = 2.1 mass%, Na ₂ O = 0.2 mass%, water absorption rate = 40%) After impregnating 52.2 g, it was heat-treated in an air stream at 300 ° C. for 0.25 hour. Furthermore, the catalyst G was heat-treated at 550 ° C. for 3 hours in a nitrogen stream.

  Thus, the content (catalyst reference) of each component of the catalyst G prepared was Ag (silver conversion) = 16.5 mass%, Cs (Cs conversion) = 2320 mass ppm, Re (Re conversion) = 550. It was mass ppm and W (W conversion) = 350 mass ppm.

[Catalyst performance evaluation 1]
The catalysts A to F were each pulverized to 600 to 850 μm, and 1.2 g of each pulverized product was charged into a heating double tube stainless steel reactor having an inside diameter of 3 mm and a tube length of 300 mm. Next, in order to investigate the optimum vinyl chloride concentration for each catalyst, this packed bed was subjected to a reaction accelerator (24% by volume of ethylene, 7% by volume of oxygen, 2.1% by volume of carbon dioxide, the balance being nitrogen and a trace amount). The reaction was carried out under the conditions of a reaction pressure of 1.6 MPaG and a space velocity of 5500 hr ⁻¹ such that the ethylene conversion amount was 2.5% by volume. The vinyl chloride concentration was varied in the range of 1.5 molppm to 4.5 molppm, and the vinyl chloride concentration that gave the highest selectivity for each catalyst was determined. Table 1 shows the water-soluble alkali concentrations of the catalysts A to F, the vinyl chloride concentration at which the highest selectivity was obtained, and the highest selectivity at that time. The selectivity was calculated according to the following formula 3. “Ethylene conversion amount 2.5 vol%” corresponds to an ethylene conversion rate of 8.3% (calculated according to the following formula 4).

  The relationship between the water-soluble alkali concentration X obtained from the catalysts A to F and the relationship Y between the optimum vinyl chloride concentration is shown in FIG. The value of A represented by Formula 1 was 0.24. Moreover, the value of B was −0.38.

［触媒性能評価２］
上記触媒Ｇの水溶性アルカリ濃度を測定したところ、水溶性ナトリウム濃度６．７μｍｏｌ／ｇ−ｃａｔ、水溶性セシウム ５．４μｍｏｌ／ｇ−ｃａｔから、水溶性アルカリ濃度は、１２．１μｍｏｌ／ｇ−ｃａｔとなった。触媒Ａ〜Ｆを用いた触媒性能評価１にて得られた導出式より、最適なビニルクロライド濃度は、２．５ｍｏｌｐｐｍと算出された。

[Catalyst performance evaluation 2]
When the water-soluble alkali concentration of the catalyst G was measured, the water-soluble alkali concentration was 12.1 μmol / g-cat from the water-soluble sodium concentration of 6.7 μmol / g-cat and the water-soluble cesium of 5.4 μmol / g-cat. It became. From the derivation formula obtained in the catalyst performance evaluation 1 using the catalysts A to F, the optimum vinyl chloride concentration was calculated to be 2.5 molppm.

[Catalyst performance evaluation 3]
Next, in the catalyst performance evaluation 1, the results when the catalyst G is evaluated under the same gas conditions and the same reaction conditions except that the vinyl chloride concentration is changed from 0.4 to 5.5 molppm are shown in FIG. Shown in In the experiment, when the vinyl chloride concentration was 2.5 mol ppm, the performance with the maximum selectivity of 88.1 mol% was obtained, and the optimum vinyl chloride concentration (2.P) calculated from the relational expression derived from the catalysts A to F was obtained. 5 mol ppm), which is an equivalent value.

  In the case of this catalyst, it can be seen that when A is set in the range of 0.07 to 0.45, a high selectivity can be obtained (selectivity 83% or more).

  Therefore, by examining the value of the water-soluble alkali concentration in advance, it is possible to know the optimum vinyl chloride concentration, so that a high selectivity can be obtained at the optimum chloride concentration from the beginning of the reaction.

  The present invention relates to a technique for producing ethylene oxide by catalytic vapor phase oxidation of ethylene.

Claims (5)

Ethylene oxide is obtained by catalytic vapor phase oxidation of ethylene using a silver catalyst containing an alkali component containing silver, a water-soluble alkali component, and a gas containing ethylene, molecular oxygen and a reaction accelerator under conditions that satisfy the following YX conditional expression. The manufacturing method of ethylene oxide characterized by manufacturing.

X: Water-soluble alkali component concentration [μmol / g-cat]
Y: Reaction accelerator concentration [molppm]
A: 0.01 or more and less than 3 B: Constant determined by gas composition 2. The method for producing ethylene oxide according to claim 1, wherein A is obtained under the following conditions.
(1) When producing ethylene oxide from a gas containing ethylene, molecular oxygen and a reaction accelerator in the presence of the silver catalyst, determining the concentration of the reaction accelerator that maximizes the ethylene oxide selectivity. However, react under the same conditions except changing the concentration of the reaction accelerator.
(2) Obtain the concentration of the reaction accelerator that maximizes the ethylene oxide selectivity in the same manner as in (1) except that the amount of the water-soluble alkali component in the silver catalyst is changed in (1).
(3) To illustrate the relationship between the amount of the water-soluble alkali component (X axis) in the silver catalyst obtained by repeating the above (2) and the concentration of the reaction accelerator (Y axis).
(4) The slope of the straight line obtained by the above (3) is A, the intercept is B, and the YX conditional expression of Formula 1 is obtained. The gas containing ethylene, molecular oxygen and a reaction accelerator is ethylene 5 to 50% by volume, molecular oxygen 2.5 to 25% by volume, and reaction accelerator 0.1 to 100 molppm. The method for producing ethylene oxide according to 1. 2. The method for producing ethylene oxide according to claim 1, wherein the silver catalyst comprises silver, an alkali component containing a water-soluble alkali component, and a catalyst component containing rhenium and a support. The method for producing ethylene oxide according to claim 1, wherein the reaction temperature is 150 to 320 ° C and the reaction pressure is 0.2 to 4 MPa.

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