JP5194727B2 - Process for continuous production of olefin oxide - Google Patents

Description

  The present invention relates to a process for producing an olefin oxide by gas phase catalytic oxidation of an olefin, particularly ethylene.

  A method for producing ethylene oxide by vapor-phase catalytic oxidation of ethylene is performed on a large scale. As the catalyst, a supported catalyst in which silver is mainly used and various promoter components are added thereto is mainly used. For example, Patent Document 1 describes that a catalyst in which an alkali metal such as potassium, rubidium, and cesium is simultaneously supported on silver on a porous carrier gives ethylene oxide with high selectivity. Patent Document 2 describes that when silver, sodium, potassium, rubidium, cesium, or the like is contained, the activity and selectivity of the catalyst are improved. As promoter components other than alkali metals, rhenium (Patent Literature 3), molybdenum (Patent Literatures 4 and 5), tungsten (Patent Literatures 6 and 7) and the like are known.

  In conducting this reaction, it is known that a trace amount of an organic halogen compound is preferably contained in the raw material gas, and various methods for controlling the content have been studied. In particular, it is known that a catalyst using rhenium as a co-catalyst other than an alkali metal strongly depends on the concentration of the organic halogen compound (Patent Documents 8 to 10). For example, Patent Documents 8 and 9 disclose an operation method for optimizing the concentration of the organic halogen compound during the use period of the catalyst. Patent Document 10 discloses an optimum operation method using an organic halogen compound by paying attention to the relationship between the concentration of hydrocarbons such as ethylene and ethane in the source gas and the concentration of the organic halogen compound. In this case, the optimum organic halogen compound concentration is said to vary greatly depending on ethane, propane, and the like.

  Furthermore, when performing this reaction, it is known that it is preferable to control the carbon dioxide concentration of the reaction system (Patent Document 11), and a method for reducing the carbon dioxide concentration is also disclosed (Patent Document 12). On the other hand, in the case of a catalyst using rhenium, there is a report that the inner diameter of the reaction tube filled therewith is preferably larger than 40 mm (Patent Document 13).

Japanese Patent Laid-Open No. 49-30286 JP-A-53-1191 JP 63-126552 A JP-A-2-131140 Japanese Patent No. 241544 JP-A-6-296867 Japanese Patent No. 343864 JP-A-2-104579 JP 2002-248351 A JP-T-2005-518356 JP-T-2006-521380 JP-T-2006-520816 WO2006-102189

  By the way, in this olefin oxide production process, the raw material gas is reacted in an oxidation reactor, olefin oxide and carbon dioxide are removed from the obtained reaction gas, and the remaining gas is returned to the oxidation reactor, whereby the remaining raw material is recycled. Adopting a process for utilization.

  In this case, water is generated in the reaction of the oxidation reactor, and water is used in the process of removing olefin oxide and carbon dioxide.

  It is described in Patent Document 11 that water adversely affects catalyst activity. Patent Document 11 describes that water affects not only catalyst activity but also selectivity and catalyst life. For this reason, it is preferable to reduce water.

  However, water is used for the olefin oxide absorbent used in the process of removing olefin oxide and the carbon dioxide absorbent that absorbs carbon dioxide. That is, the reaction gas comes into direct contact with water. For this reason, the gas returning to the oxidation reactor can contain the maximum amount of water corresponding to the saturated water vapor pressure at that temperature. In order to remove water, it is conceivable to provide a new water removal tower, but for that purpose, a great investment in equipment is required.

  Therefore, the present invention does not provide a new water removal tower and presupposes that water enters the oxidation reactor, and suppresses the decrease in selectivity of the olefin oxide production reaction, and keeps this selectivity as much as possible. The purpose is to find a control method.

  In this invention, an oxidation reactor for synthesizing olefin oxide by contacting a raw material gas containing olefin, oxygen and a halogen compound with a catalyst in which each component of silver, rhenium and cesium is supported on a carrier, and olefin oxide is absorbed. Having an olefin oxide absorption tower and a carbon dioxide absorption tower that absorbs carbon dioxide, the reaction gas obtained in the oxidation reactor is sent to the olefin oxide absorption tower, and using an olefin oxide absorbent containing water, Absorbs olefin oxide, then sends part or all of the first residual gas of the olefin oxide absorption tower to the carbon dioxide absorption tower, absorbs carbon dioxide with a carbon dioxide absorbent containing water, and The olefin oxide returned to the oxidation reactor using the second residual gas of the carbon dioxide absorption tower as part of the raw material gas In the production method, the amount of halide contained in the gas at the inlet of the oxidation reactor is set to the amount of the oxidation before the increase in water with respect to an increase of 0.1% by volume of water contained in the gas at the inlet of the oxidation reactor. By reducing the amount of halide in the gas at the inlet of the reactor by 0.4 to 4.8%, the above problem could be solved.

  According to the present invention, the supply amount of the halide is decreased by a predetermined amount in accordance with the increase amount of the moisture amount in the oxidation reactor, so that the reduction in the selectivity of the olefin oxide can be suppressed. For this reason, the selectivity can be maintained without providing a new water removal tower.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, an olefin oxide production method according to the present invention comprises an oxidation reactor for synthesizing olefin oxide by bringing a raw material gas containing olefin into contact with a predetermined catalyst, and olefin oxide absorption for absorbing olefin oxide. It is the method manufactured using the manufacturing apparatus containing the tower | column and the carbon dioxide absorption tower which absorbs a carbon dioxide.

  The catalyst is a catalyst in which a silver component is a main catalyst and at least a rhenium component and a cesium component are supported on a carrier as a promoter. The present invention is effective for a catalyst containing a rhenium component as a promoter. The cocatalyst preferably contains lithium in addition to the cocatalyst component.

  As the silver component used as the main catalyst, a complex is formed with a compound having ammonia, amino group, carbonyl group, carboxyl group, etc., dissolved in water or an organic solvent, and decomposed and deposited at a temperature of 500 ° C. or lower. Silver compounds are usually used. Among them, it is preferable to use a silver compound that decomposes and precipitates at a temperature of 300 ° C. or lower, particularly 260 ° C. or lower. Examples of such silver compounds include silver oxide, silver nitrate, silver carbonate, silver sulfate, silver acetate and silver oxalate. Among these, silver oxalate is preferable.

  As the compound having an amino group used for forming the complex, pyridine, monoamine, polyamine, alkanolamine and the like are usually used. Examples of the monoamine include alkylamines having 1 to 6 carbon atoms. Examples of the polyamine include ethylenediamine and 1,3-diaminopropane. Examples of the alkanolamine include ethanolamine and propanolamine. Among these, it is preferable to use ethylenediamine or 1,3-diaminopropane, and it is more preferable to use a mixture of both.

  Further, β-diketone such as acetylacetone is usually used as the compound having a carbonyl group used for forming the above complex, and neodecanoic acid is usually used as the compound having a carboxyl group used for forming the above complex. .

  As the rhenium component used as the promoter, rhenium oxide, ammonium salts of perrhenic acid, alkali metal salts and the like are usually used. As the cesium component used as the promoter, hydroxides, halides, nitrates, acetates, carbonates, bicarbonates, sulfates and the like are usually used, and the support is impregnated as an aqueous solution.

Examples of the carrier include conventional refractory carriers such as alumina, titania, zirconia, magnesia, and silicon carbide. Among these, alumina, particularly α-alumina is preferably used. The specific surface area of the carrier is, 0.1~3.0m ² / g C., preferably ^{0.5~2.0m 2 / g, 0.8~1.7m 2 /} g is particularly preferred.

  The above carrier may be used as it is for supporting silver, rhenium and cesium in the next step as it is, but it supports an alkali component in advance before supporting silver (hereinafter referred to as “pretreatment”). Is preferable in terms of catalyst performance. As the alkali metal used in this pretreatment, cesium and lithium are preferable, and the combined use of cesium and lithium is more preferable. The content of cesium and lithium in the carrier is usually 10 to 10000 ppm by weight, preferably 100 to 1000 ppm by weight.

  As the pretreatment, drying after impregnating the alkali component solution may be performed in an inert gas such as nitrogen, helium, or argon, or in air or superheated steam. Among these, it is preferable to carry out in superheated steam. Drying is preferably performed at 120 to 500 ° C, particularly 120 to 250 ° C.

  Supporting each component of silver, rhenium and cesium on a carrier can be carried out according to a conventional method. Usually, the carrier is impregnated with each component alone or as a mixed solution with other components. The order of impregnation is arbitrary. For example, after the silver component is first supported, the cesium component and the rhenium component may be supported, but it is preferable to support the cesium component and the rhenium component together with the silver component.

  The alkali metal used in the pretreatment of the carrier is present on the surface of the carrier to adjust the properties of the carrier, whereas cesium supported simultaneously with silver is present on the silver surface or inside the silver. Conceivable. Therefore, it is assumed that the alkali metal used in the carrier pretreatment process and the silver supporting process have different action mechanisms.

  The silver, rhenium and cesium components are all preferably impregnated in the support as a solution, and then heated to be supported on the support. By this treatment, the silver component is precipitated from the compound as a metal simple substance and is supported on the support. However, the silver simple substance by heating is deposited at 120 to 500 ° C. in air or an inert gas such as nitrogen, argon or helium. It may be performed for 24 minutes. Precipitation is preferably performed by heating at 120 to 300 ° C., particularly 130 to 260 ° C. for 1 minute to 3 hours, particularly 3 minutes to 30 minutes, under a flow of superheated steam at 0.3 to 5 m / second. When superheated steam is used, a catalyst with good performance is generally obtained. This is considered because the distribution of silver, rhenium, and cesium components in the catalyst becomes uniform. Usually, a catalyst impregnated with a catalyst component is accommodated in a heat treatment apparatus of a fixed bed type or a moving bed type, and a catalyst is prepared by circulating a heated gas in the bed.

  The silver content is preferably supported on the carrier so as to be 5 to 30% by weight with respect to the finally produced catalyst. The content of cesium is usually 20 to 50,000 ppm by weight, preferably 200 to 5,000 ppm by weight. The content of rhenium is usually 10 to 10,000 ppm by weight, preferably 100 to 1,000 ppm by weight.

  The said oxidation reactor is a reactor for arranging the said catalyst in the inside and oxidizing an olefin. In this oxidation reactor, raw materials such as olefin and oxygen, and nitrogen or methane as a diluent are supplied as raw material gases, and an oxidation reaction for synthesizing olefin oxide is performed. Further, a halide is added to the raw material gas as a reaction modifier.

  Examples of the olefin include ethylene, propylene, butadiene and the like. When ethylene is used as the olefin, the composition of the raw material gas is 1 to 40% by volume of ethylene and 1 to 20% by volume of oxygen, with the remainder being the diluent. However, in reality, alkanes such as ethane are several percent as impurities of ethylene, and for the reasons described later, carbon dioxide is usually 0.1% by volume or more and maximum, as described in Patent Document 11 above. About 10% by volume is included. Further, as described in Patent Document 11, water is often contained in an amount of 0.01 to 1.5% by volume.

  The amount of the halogen compound contained as a reaction modifier in the raw material gas is preferably about 1 to 50 ppm by volume. As the halogen compound, chlorine compounds such as chlorine, hydrogen chloride, and organic chlorine compounds having 1 to 5 carbon atoms are usually used. Among them, an organic chlorine compound having 1 to 5 carbon atoms, particularly from the viewpoint of easy handling, methyl chloride, ethyl chloride, propyl chloride, vinyl chloride, 1,2-dichloroethane, 1,2-dichloropropane, 1, C1-C3 chlorinated hydrocarbons such as 3-dichloropropane are preferably used. Moreover, you may use these 2 or more types together as desired. When these organic chlorine compounds are used, the concentration in the raw material gas is more preferably about 0.5 to 10 ppm by volume.

  By the way, as disclosed in Patent Document 12, when the source gas is recycled, various compounds that function as a reaction modifier and may exist in the feedstock may be generated. For example, when using ethyl chloride in an ethylene oxide process, the feed may actually contain ethyl chloride, vinyl chloride, ethylene dichloride (1,2-dichloroethane), methyl chloride, and the like.

The oxidation reaction is usually performed at a temperature of 180 to 350 ° C., preferably 200 to 300 ° C., under a pressure of 0.1 to 4 MPa. The superficial velocity (GHSV) of the source gas is usually 1,000 to 10,000 hr ⁻¹ at 0 ° C. and 1 atm.

  The reaction gas obtained in the oxidation reactor is sent to the olefin oxide absorption tower. Then, in this olefin oxide absorption tower, the olefin oxide is absorbed by the olefin oxide absorbent by bringing the reaction gas into contact with the olefin oxide absorbent. Water is used as the olefin oxide absorbent.

  And the olefin oxide absorbent which absorbed said olefin oxide is taken out from this olefin oxide absorption tower, is sent to an olefin oxide recovery process, and olefin oxide is collect | recovered.

  The residual gas from which the olefin oxide has been removed in the olefin oxide absorption tower (hereinafter referred to as “first residual gas”) is partly or wholly sent to the carbon dioxide absorption tower. The amount of the first residual gas sent to the carbon dioxide absorption tower is determined according to the amount of carbon dioxide absorbed. In the above-mentioned Patent Document 12, it is usually at least 30% by volume, preferably 40% by volume or more, and most preferably 50% by volume or more. On the other hand, the upper limit of the amount to be sent is the total amount, that is, 100% by volume.

  Next, in this carbon dioxide absorption tower, the carbon dioxide absorbent is made to absorb carbon dioxide by bringing the first residual gas into contact with the carbon dioxide absorbent. As this carbon dioxide absorbent, an agent containing water is used, and examples thereof include an aqueous potassium carbonate solution.

  Then, the carbon dioxide absorbent that has absorbed carbon dioxide is sent to the carbon dioxide emission process and processed.

  Thus, by removing carbon dioxide from the first residual gas, the carbon dioxide concentration of the gas returned to the oxidation reactor can be reduced as will be described later. Since carbon dioxide affects the catalyst in the oxidation reactor and affects the selectivity of olefin oxide, it is possible to exert an effect in maintaining this selectivity by reducing the carbon dioxide concentration.

  The residual gas from which carbon dioxide has been removed by the carbon dioxide absorption tower (hereinafter referred to as “second residual gas”) contains unreacted olefin, oxygen, methane, halide, and the like. The remaining raw material can be reused by returning the second residual gas to the oxidation reactor as a part of the raw material gas. As a result, carbon dioxide remains in the raw material gas depending on the carbon dioxide absorption capacity of the carbon dioxide absorption tower. In the present invention, the lower limit of the carbon dioxide concentration in the raw material gas is a concentration as described in the specification of Patent Document 11, that is, 0.1% by volume, preferably 0.2% by volume, particularly preferably Patent Document. It is effective at a concentration as described in 11 Example 1, ie 1% by volume. On the other hand, the upper limit of the carbon dioxide concentration in the raw material gas is a concentration as described in Example 1 of Patent Document 11, that is, 7% by volume, preferably 5% by volume.

  As described above, the reaction gas in the oxidation reactor is contacted with the olefin oxide absorbent containing water in the olefin oxide absorption tower, then in contact with the carbon dioxide absorbent containing water in the carbon dioxide absorption tower, and then oxidized. Return to reactor. And since the gas returned to the said oxidation reactor contacts with water in an olefin oxide absorption tower and a carbon dioxide absorption tower, it will contain water. The concentration of water is based on the gas flow rate and water concentration at the top of the olefin oxide absorption tower, and the gas flow rate and water concentration at the top of the carbon dioxide absorption tower. Incidentally, the water concentration at the top of the olefin oxide absorption tower and the carbon dioxide absorption tower is a saturated vapor pressure determined by temperature and pressure in a normal operation state. Therefore, in the normal operation state where the above hypothesis holds, the water concentration at the oxidation reactor inlet may be directly measured by a gas chromatograph, a dew point meter, etc., but the olefin oxide absorption tower and the carbon dioxide absorption tower It is convenient to obtain the saturated water vapor pressure from the temperature and pressure at the top of the column and calculate from the respective gas flow rates. However, when the above hypothesis does not hold, that is, when the water concentration at the oxidation reactor inlet cannot be obtained by the above calculation, it is necessary to directly measure with a gas chromatograph, a dew point meter or the like.

  The concentration of this water is generally 0.01 to 1.5% by volume, as described in Patent Document 11. The present invention is particularly effective when the water concentration is 0.45 to 0.75% by volume.

  By the way, in the above oxidation reactor, when an oxidation reaction is performed using a catalyst under the above conditions, the selectivity of olefin oxide in the reaction in which olefin and oxygen react to produce olefin oxide (hereinafter simply referred to as “selectivity”). Is gradually increased from the start of the reaction and reaches a maximum value. And after the selectivity of olefin oxide reaches the maximum value, the selectivity gradually decreases. This decrease in selectivity is also affected by changes in the amount of water in the oxidation reaction vessel.

  That is, when the moisture content of the gas at the inlet of the oxidation reactor (hereinafter referred to as “inlet gas”) increases, the selectivity decreases. At this time, the amount of halide contained in the inlet gas is 0.1% by volume of water contained in the inlet gas, and the amount of halide contained in the inlet gas before the increase in water is 0.4%. By reducing the volume% or more, the selectivity increases and can be recovered to near the selectivity before the increase in the amount of water. The reduction amount of the halide is preferably 1.2% by volume or more. If the reduction amount of the halide is less than 0.4% by volume, the selectivity hardly increases and the effect becomes insufficient. On the other hand, the upper limit of the reduction amount of the halide is required to be 4.8% by volume, and preferably 3.6% by volume. When the amount is decreased more than 4.8% by volume, the selectivity tends to decrease. By setting the reduction amount of the halide within the upper limit range, it is possible to suppress the decrease in selectivity and maintain the selectivity.

  Conversely, if the amount of water contained in the inlet gas is reduced by 0.1% by volume, the halide concentration is increased by 0.4% or more by volume. The upper limit of the increase amount of the halide is required to be 4.8% by volume, and preferably 3.6% by volume.

  The implementation method in the plant of this invention is as follows. Olefin oxide is produced by using a catalyst in which silver, rhenium and cesium are supported on a carrier according to the operating conditions of the plant. At this time, since the olefin oxide absorption tower and the carbon dioxide absorption tower are in operation, moisture according to the plant operating conditions is introduced into the oxidation reactor inlet. This water concentration is directly measured as described above, or is calculated from the plant operating conditions in the case of a normal operating state as described above.

  Next, the halide concentration is changed so that the selectivity is high or the activity is high, that is, the reaction temperature is low, or the selectivity is high and the activity is high. Determine the halide concentration. Thereafter, when changing the operation conditions of the plant, after the change, the water concentration is directly measured or calculated from the operation conditions in the same manner as before the change, and the amount of change in the water concentration is obtained. And according to this invention, the halide density | concentration is changed according to the variation | change_quantity of water concentration.

  Hereinafter, the present invention will be described more specifically with reference to examples. The catalyst used in the examples was prepared as follows.

[Preparation of catalyst]
12 kg of α-alumina support (cylindrical surface area 1.4 m ² / g, water absorption 36.2%, outer diameter 8 mm, inner diameter 3 mm, height 8 mm), 280 g of lithium carbonate (Li ₂ CO ₃ ) and cesium carbonate ( Cs ₂ CO ₃ ) 27.7 g of an aqueous solution in which 27.7 g was dissolved was added, and the carrier was impregnated with the aqueous solution. The carrier was taken out and dried by contacting with 150 ° C. superheated steam at 2 m / second for 15 minutes.

Next, an aqueous solution prepared by dissolving 12 L of an aqueous silver nitrate (AgNO ₃ ) solution (Ag 137 g / L) and 1550 g of potassium oxalate (K ₂ C ₂ O ₄ .H ₂ O) in 13.2 L of water was prepared. Were gradually mixed at 60 ° C. to form a white precipitate of silver oxalate. The precipitate was collected by filtration and washed with distilled water to obtain a silver oxalate precipitate (Ag ₂ C ₂ O ₄ , water content 20.9%).

Next, 2930 g of the hydrous precipitate of silver oxalate obtained above was gradually added and dissolved in a mixed amine aqueous solution consisting of 826 g of ethylenediamine, 226 g of 1,3-diaminopropane and 960 g of water to prepare a silver amine complex solution. To this was added 100 mL of an aqueous solution in which 13.3 g of cesium nitrate (CsNO ₃ ) was dissolved, 100 mL of an aqueous solution in which 7.31 g of ammonium perrhenate (NH ₄ ReO ₄ ) was dissolved, and 810 mL of water, and silver, rhenium and A solution containing cesium was obtained. This solution was put into an evaporator, and the total amount of the carrier carrying lithium and cesium prepared above was added thereto, and kept at 40 ° C. under reduced pressure to impregnate the carrier with the solution. Next, this support was taken out and contacted with 200 ° C. superheated steam at 2 m / second for 15 minutes to prepare a catalyst. The supported amounts of silver, rhenium, cesium and lithium in the obtained catalyst were 11 wt%, 340 wt ppm, 980 wt ppm and 550 wt ppm, respectively.

(Reference experiment 1)
A reaction tube having an inner diameter of about 38.9 mm, which is the same as the above-mentioned Patent Document 13, is charged with 12 L of catalyst. ) 1.5 vol ppm, carbon dioxide 3.0 vol%, water 0.6 vol%, balance nitrogen) is supplied as GHSV at 0 ° C. and 1 atm at 4000 hr ⁻¹ , pressure 1.8 MPa (gauge pressure). The reaction temperature was controlled so that the space-time yield (STY) per liter of the ethylene oxide catalyst was 0.19 kg-ethylene oxide / hr. At this time, the obtained reaction gas did not recover olefin oxide and carbon dioxide from the reaction gas as shown in FIG. 1 and did not return it to the reaction tube for the second residual gas.
Table 1 shows the results obtained by optimizing the chlorine compound concentration and evaluating for about 6 months.
Here, the selectivity represents the ratio of the produced ethylene oxide to the ethylene consumed by the reaction in percent.

In Table 1, “X1” means the reduction rate (%) of halide, and “X2” means the reduction rate (%) of halide per 0.1 volume% of water. . These are calculated from the following equations.
X1 (%) = reduction amount of halide (volume ppm) / addition amount of halide in standard experiment 1 (volume ppm) × 100
X2 (%) = X1 (%) / (increase amount of water (volume%) / 0.1 (volume%))

[First Experiment Group]
(Comparative Example 1, Example 1)
In Reference Experiment 1, the amount of water added to the raw material gas was changed as shown in Table 1, and the amount of halide (chlorine compound) was changed to the amount shown in Table 1. The performance at that time is shown in Table 1.

[Second Experiment Group]
(Examples 2 to 4)
In Reference Experiment 1, the amount of water added to the raw material gas was changed as shown in Table 1, and the halide (chlorine compound) was changed to the amount shown in Table 1. The performance at that time is shown in Table 1.

(result)
Compared to the standard experiment 1, the water concentration was increased to 0.3% by volume, but in Comparative Example 1 in which the halide (chlorine compound) concentration was not changed, the selectivity decreased by 1.3%. On the other hand, in Example 1 in which the halide (chlorine compound) concentration was lowered to 2.05 ppm by volume, the decrease in halide (chlorine compound) per 0.1 vol% of water was equivalent to 0.8 vol%, The selectivity was 85.6%, an improvement of 0.2% compared to Comparative Example 1.

  On the other hand, in Examples 2-4, with respect to the reference | standard experiment 1, water concentration was increased to 0.6 volume% and chlorine compound concentration was set to 2.0 volume ppm, 1.9 volume ppm, 1.8 respectively. The volume was reduced to ppm. The reduction amounts of halide (chlorine compound) per 0.1% by volume of water were 0.8%, 1.6%, and 2.4%, respectively. As a result, the selectivities were 84.1% and 85%, respectively. 5% and 85.8%. When the amount of increase in water concentration is 0.6% by volume, the amount of decrease in chlorine compounds per 0.1% by volume of water is preferably 1.6% in terms of selectivity than the case of 0.8%, It was found that 2.4% is more preferable.

Flow chart showing an example of a part of the production process of the continuous production method of olefin oxide according to the present invention

Claims (1)

An oxidation reactor for synthesizing olefin oxide by bringing a raw material gas containing olefin, oxygen and a halogen compound into contact with a catalyst in which each component of silver, rhenium and cesium is supported on a carrier, and an olefin oxide absorption tower for absorbing olefin oxide And having a carbon dioxide absorption tower for absorbing carbon dioxide,
Send the reaction gas obtained in the oxidation reactor to the olefin oxide absorption tower, absorb olefin oxide using an olefin oxide absorbent containing water,
Next, part or all of the first residual gas of the olefin oxide absorption tower is sent to the carbon dioxide absorption tower, and carbon dioxide is absorbed using a carbon dioxide absorbent containing water,
And in the manufacturing method of the olefin oxide which returns the said 2nd residual gas of the said carbon dioxide absorption tower as a part of raw material gas to the said oxidation reactor,
When water contained in the gas at the inlet of the oxidation reactor increases, the amount of halide contained in the gas at the inlet of the oxidation reactor is increased with respect to the increase of 0.1% by volume. 0.4 to 4.8% reduction relative to the amount of halide in the gas at the inlet of the oxidation reactor,
When the water contained in the gas at the inlet of the oxidation reactor is reduced, the amount of halide contained in the gas at the inlet of the oxidation reactor is reduced by 0.1% by volume with respect to the reduction amount of 0.1% by volume. A method for producing an olefin oxide, characterized by increasing 0.4 to 4.8% with respect to the amount of halide in the gas at the inlet of the oxidation reactor.

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