JP3403476B2 - Method for producing ethylene oxide - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing ethylene oxide. More specifically, when ethylene is produced by catalytic gas-phase oxidation of ethylene with a gas containing molecular oxygen, an abnormal reaction is prevented by mixing an inert gas with the gas retention part existing in the reaction product gas flow zone. The present invention relates to a safe method for producing ethylene oxide.

[0002]

2. Description of the Related Art In the catalytic gas phase oxidation reaction of ethylene, for example, in the process of producing ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen in the presence of a silver catalyst, in addition to ethylene, saturation of methane, ethane, etc. hydrocarbon,
A hydrocarbon-containing gas containing nitrogen, carbon dioxide, argon, oxygen, etc. and a molecular oxygen-containing gas consisting of air, oxygen-enriched air or pure oxygen are mixed at a predetermined ratio, and then a silver catalyst is filled. The catalytic gas phase reaction introduced into the reactor is carried out. At that time, when ethylene is reacted with molecular oxygen in the presence of a silver catalyst,

[0003]

[Chemical 1]

[0004]

[Chemical 2]

An exothermic reaction represented by

Of these exothermic reactions, in order to improve the yield of ethylene oxide, the rate at which the reaction represented by the reaction formula (1) proceeds should be increased, and the silver catalyst and the reaction method should be examined. Has been done. However, at present, it is unavoidable that the reaction formula (2), that is, the complete oxidation reaction of ethylene, which has a large reaction heat, simultaneously occurs.

In addition to the above reaction formulas (1) and (2), there are reactions that affect the yield of ethylene oxide. It is an isomerization reaction of the produced ethylene oxide to acetaldehyde, which proceeds according to the following reaction formula (3).

[0008]

[Chemical 3]

Therefore, no matter how high the selectivity of ethylene to ethylene oxide is, if the isomerization reaction of the produced ethylene oxide to acetaldehyde is large, the yield of ethylene oxide is lowered.

Further, there is an abnormal reaction to carbon monoxide, hydrocarbons (methane, ethane, ethylene, etc.), hydrogen and water which proceed according to the reaction formula shown in the following reaction formula (4). Since the reaction product gas flow zone downstream of the reaction tube outlet of the reactor has a high temperature, eliminating an abnormal reaction is one of the major problems in ethylene oxide production.

[0011]

[Chemical 4]

Since the demand for ethylene oxide is increasing in recent years, and in order to reduce the production cost of ethylene oxide, the ethylene oxide production plant is being enlarged. Therefore, how to safely operate the ethylene oxide production plant poses a serious safety and economic problem in producing ethylene oxide by catalytic gas phase oxidation of ethylene with molecular oxygen.

Generally, in the catalytic gas phase oxidation of hydrocarbons with molecular oxygen, a method is known in which a reaction product gas is passed through a cooling zone filled with a filler in order to suppress abnormal reactions and side reactions (special feature: Kosho 39-17254). It is also known to apply such a method to a method for producing ethylene oxide by a catalytic gas phase oxidation method of ethylene with molecular oxygen. For example, JP-A-51-41
According to No. 01, the reaction product obtained in the reaction zone is passed through a cooling zone which may or may not be adjacent to the reaction zone and may or may not contain an inert material. Further, according to Japanese Patent Laid-Open No. 53-2409, the reaction product is passed through a cooling zone filled with inert refractory particles having a surface area of 0.1 m ² / g or less.

[0014]

The multitubular heat exchange type reactor, which has been conventionally used for producing ethylene oxide by catalytic gas phase oxidation with ethylene and molecular oxygen, has a safety and workability. Sex manhole (Japanese Patent Laid-Open No. 54-32)
No. 408, Japanese Patent Application Laid-Open No. 63-190881), a safety valve for preventing abnormal pressure rise and a rupture plate, a pressure gauge, a thermometer, and an expansion joint for preventing destruction of piping due to thermal stress. , There is a gas retention section. However, there is a problem that an abnormal combustion reaction occurs in these gas retention parts.

In the present invention, the gas existing in the reaction product gas flow zone at 200 to 300 ° C. downstream of the reaction tube outlet of the reactor in the case of producing ethylene oxide by catalytic gas phase oxidation with ethylene and molecular oxygen described above. An object of the present invention is to provide a method for producing ethylene oxide that prevents abnormal combustion reaction in the retention part.

[0016]

In the present invention, ethylene is reacted with a molecular oxygen-containing gas at a reaction pressure of 0.59 to 4.02 M.
Working manhoe existing in the reaction product gas flow zone downstream from the reaction tube outlet of the reactor used to produce ethylene oxide by catalytic gas phase oxidation at Pa and up to the cooler.
, Safety valve, rupture disc, pressure gauge, thermometer and expander
At least one <br/> gas residence portion selected from the group from the Deployment joint, the method of manufacturing ethylene oxide which comprises suppressing the isomerization reaction to ethylene oxide of acetaldehyde generation by supplying an inert gas .

In the present invention, the gas retention portion at the gas outlet of the reactor is a reactor used for producing ethylene oxide by catalytic gas-phase oxidation with ethylene and molecular oxygen, for example, a tubular heat exchange type. There are a manhole for a passage installed at the reaction tube outlet of the reactor, a safety valve, a rupture plate, a pressure gauge, a thermometer, and an expansion joint for preventing destruction of piping due to thermal stress. The temperature of such a gas retention part is 200 to 300 ° C., preferably 210 to 300 ° C.
280 ° C.

Examples of the inert gas used in the present invention include nitrogen, carbon dioxide, methane and argon.
Preferred is nitrogen. The inert gas is supplied to the reaction product gas so that the gas retention time defined by the following formula is 12 hours or less, preferably 1 to 10 hours, more preferably 3 to 8 hours. be able to.

[0019]

[Equation 1]

The inert filling material to be filled in the preheating portion and the inert material filling portion of the reactor of the present invention may be an inert refractory material, and may be spheres, hemispheres, pellets, rings or amorphous shapes. Any of them can be used, but alumina, silica-alumina, zirconia, magnesia, silicon carbide and the like which are usually used as a carrier for silver catalysts are preferable, and stainless steel, α-alumina and zirconia are particularly preferable. The shape, dimensions of these inert refractory carriers,
The pores, specific surface area, apparent porosity, etc. can be appropriately selected in consideration of pressure loss and mechanical strength when the reaction tube is filled. The average particle size is usually 1/16 to 1/2 inch, preferably 3/16 to 1/2 inch, and spherical or ring-shaped material is preferable. Further, those obtained by precipitating at least one selected from sodium, potassium, rubidium, cesium, lithium, calcium, strontium, barium and thallium on the above inert refractory carrier can be preferably used, and particularly sodium, potassium and rubidium. , Cesium and thallium are preferred. It is particularly preferable to fill these in the reaction tube of the inert material filling section.

As the process and reaction conditions to which the method of the present invention can be applied, any of the process and reaction conditions conventionally known in this field can be applied. For example, a process for producing ethylene oxide by catalytic vapor-phase oxidation of ethylene with molecular oxygen includes an air oxidation method using air as an oxygen source and an oxygen oxidation method using pure oxygen. Can be effectively applied to. In particular, the oxygen oxidation method, which can increase the reaction amount per one pass of the catalyst layer and increase the ethylene oxide concentration, can be effectively applied.

The operating conditions are that the source gas mixture is ethylene,
It is composed of reaction inhibitors such as oxygen, carbon dioxide, nitrogen, argon, methane, ethane and ethane dichloride, and the higher the ethylene concentration is, the more advantageous it is, but 40% by volume or less, particularly 15 to 35% by volume. . Carbon dioxide is 10% by volume or less, particularly 4 to 8% by volume. Also, when methane or ethane is present in the gas, methane has the effect of shifting the explosion range to the safe side and narrowing the explosion range, so it is effective to be present in a considerably high concentration as a reaction gas diluent. .

The reaction pressure is 0.59 to 4.02 MPa, preferably 1.08 to 3.04 MPa. The reaction temperature is 150 to 300 ° C, preferably 180 to 280 ° C. The space velocity is 1000 to 10000 hr ^-1 , preferably 2000 to 8000 hr ^-1 .

As the catalyst to be filled in the reaction part, any conventionally known silver catalyst can be used, but the specific surface area is 20 m ² / g or less, preferably 0.01 to 10 m ² / g, and the apparent porosity is 20% by volume. As mentioned above, it is preferable to deposit and support a trace amount of metallic silver on an inert refractory carrier of preferably 30 to 70% by volume, and at least one alkali metal selected from cesium, potassium and rubidium as a reaction accelerator,
It is preferable to add at least one selected from alkaline earth metals, thallium, antimony, tin and the like. As the carrier material, an inert refractory carrier such as alumina, silica-alumina, silicon carbide, zirconia or magnesia can be used, and an inert refractory carrier containing α-alumina as a main component is particularly preferable. The shape of the carrier includes spheres, hemispheres, rings, pellets and the like, but spheres or rings are preferred.
The average particle size is preferably 1/16 to 1/2 inch, and particularly preferably 3/16 to 5/16 inch. The amount of silver supported may be 1 to 20% by weight in the catalyst, especially 5 to
The range of 15% by weight is practically economical.

The present invention will be described in more detail with reference to the drawings. The drawings show one embodiment of the catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas in the presence of a silver catalyst and one of the apparatuses used, and the present invention is not restricted thereto.

In FIG. 1, a large number of reaction tubes are provided,
In addition, the preheating section 4 filled with an inert substance at the inlet of the reaction tube, the reaction section 5 filled with a silver catalyst between the inlet and the outlet of the reaction tube, or the inert filler at the outlet of the reaction tube In the reaction tube 3 of the vertical multitubular heat exchange reactor 2 provided with the inert packing material filling section 6 filled with ethylene, oxygen, carbon dioxide gas,
A raw material gas containing nitrogen and a reaction inhibitor such as argon, methane, ethane, ethane dichloride and the like at a temperature of 100 to 200 ° C., preferably 150 to 190 ° C. is introduced from a raw material gas supply conduit 1, a preheating part 4, a reaction part. 200 to 3 through the reaction product gas conduit 7 via
The reaction product gas at 00 ° C., preferably 210 to 280 ° C., is sent to the cooler 11 for cooling.

The present invention is composed of a large number of reaction tubes 3, and a preheating section 4 in which the inlet of the reaction tube is filled with an inert substance, and a silver catalyst is filled between the inlet and the outlet of the reaction tube. Adjacent to the reaction section 5 or the reaction section 5 of the vertical multitubular heat exchange reactor 2 provided with the inert packing filling section 6 filled with the inert packing at the exit of the reaction tube Without adjoining it, a process in which a cooler 11 for cooling the reaction product gas is installed in a separate place, or adjacent to the inert packing filling part 6 filled with the silver catalyst in the vertical multitubular heat exchange type reactor 2. Instead, it is effective for a process in which a cooler for cooling the reaction product gas is installed at a remote place. The cooler 11 includes a boiler for recovering heat, a heat exchanger for exchanging heat between the raw material gas supplied to the reactor and the reaction product gas, a cooler using water, air, or the like.

The inert gas is supplied to the heat exchanger 11 downstream of the reaction tube outlet of the vertical multitubular heat exchange reactor 2 according to the present invention.
Between the reaction product gas flow zone of 200-300 ° C between the working space, the safety valve, the rupture plate, the pressure gauge, the thermometer and the expansion joint for preventing the destruction of the piping due to the thermal stress An inert gas can be supplied to the gas retention part. In FIG.
The inert gas is supplied to the gas retention portion 9 of the expansion joint 8 from the inert gas supply conduit.

Downstream from the reaction tube outlet of the reactor of the present invention 20
The gas retention portion existing in the reaction product gas flow zone of 0 to 300 ° C. can be filled with a net, pole ring, Raschig ring, or saddle-shaped inert substance.

FIG. 2 shows another embodiment of the present invention, in which the gas retention part 12 is provided in the manhole 14 at the bottom of the reactor 2.
Is formed, and the inert gas is supplied to the gas retention portion from the inert gas supply conduit 13. In the figure, the same reference numerals as those in FIG. 1 represent the same members.

[0031]

According to the present invention, the reaction product gas flow zone below the outlet of the reaction tube of the reactor and up to the heat exchanger at the time of producing ethylene oxide by catalytic gas-phase oxidation with ethylene and molecular oxygen described above. Presenting the effect of eliminating the occurrence of abnormal combustion reaction in the gas retention portion existing in, and stabilizing the thermal efficiency and increasing the effect of suppressing the isomerization reaction to acetaldehyde which is an impurity Is.

[0032]

The present invention will be described in more detail with reference to the following examples. However, this embodiment is one aspect of the invention and does not limit the invention.

Example 1 In FIG. 1, a source gas of 2.36 MPa preheated to a temperature of 180 ° C. containing 20% by volume of ethylene, 8% by volume of molecular oxygen and 6% by volume of carbon dioxide is a source gas supply conduit 1
Through the reaction tube 3 of the vertical multitubular heat exchange reactor 2 at a space velocity of 5000 hr ⁻¹ , a preheating part 4 filled with an inert substance, a reaction part 5 filled with a silver catalyst and an inert substance. The reaction product gas at 242 ° C. containing 2% by volume of produced ethylene oxide was sent to the cooler 11 through the reaction product gas conduit 7 via the filling section 6.

On the other hand, the gas retention part 9 of the expansion joint part 8 for preventing thermal stress in the pipe installed between the reaction product gas conduit 7 and the reaction product gas conduit 10 at the reaction tube outlet of the multitubular heat exchange type reactor 2. (Φ650mm × 660mm,
0.22 m ³ ) (temperature 242 ° C.) was supplied with nitrogen gas through the inert gas supply conduit 10. After 1000 hours of operation, analysis was conducted in the reaction product gas conduit 7 on the downstream side of the expansion joint 8 for preventing thermal stress on pipes. As a result, carbon monoxide was 0.05 ppm by volume and aldehyde was 2 ppm by volume. Further, as a result of open inspection of the gas retention part 7, no adhesion formation of carbide was found. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1 In Example 1, the inert gas supply conduit 1 was installed in the gas retention portion 9 of the expansion joint portion 8 for preventing thermal stress on piping.
Example 1 was repeated except that the nitrogen gas was not supplied through 0. After operating for 13 hours, the temperature of the reaction product gas suddenly rose to 316 ° C., and the emergency operation was stopped. As a result of analysis in the reaction product gas conduit 7 on the downstream side of the expansion joint 8 for preventing thermal stress in the pipe, carbon monoxide 5000
Volume ppm, aldehyde (as acetaldehyde) 1
It was 000 ppm by volume. Further, as a result of open inspection of the gas retention section 9, adhesion formation of carbide was observed. The results are shown in Table 1.
Shown in.

[0036]

[Table 1]

Example 2 In FIG. 2, a source gas of 2.36 MPa preheated to a temperature of 180 ° C. containing 20% by volume of ethylene, 8% by volume of molecular oxygen and 6% by volume of carbon dioxide is a source gas supply conduit 1.
Is introduced into the reaction tube 3 of the vertical multitubular heat exchange reactor 2 at a space velocity of 5000 hr ⁻¹ , and is produced through a preheating section 4 filled with an inert substance and a reaction section 5 filled with a silver catalyst. A 244 ° C. reaction product gas containing 2% by volume of ethylene oxide was sent through a reaction product gas conduit 7 to a cooler (not shown).

On the other hand, the manhole 1 installed between the reaction tube outlet of the multi-tube heat exchange reactor 2 and the reaction product gas conduit 7.
4 gas retention section 12 (φ600 mm × 600 mm, 0.
Carbon dioxide gas was supplied to 17 m ³ ) through an inert gas supply conduit 13. After running for 1200 hours, the reaction product gas conduit 7 on the downstream side of the manhole 8 analyzed the results and found that carbon monoxide was 0.05 ppm by volume or less and aldehyde was 2 ppm by volume. In addition, as a result of open inspection of the gas retention section 12, no adhesion formation of carbide was found. The results are shown in Table 2.

Comparative Example 2 The same procedure as in Example 2 was carried out except that carbon dioxide gas was not supplied to the gas retention portion 12 of the manhole 14 through the inert gas supply conduit 13. After 20 hours of operation, the temperature of the reaction product gas suddenly rose to 314 ° C., so the emergency operation was stopped. As a result of analysis in the reaction product gas conduit 7 on the downstream side of the gas retention section 12 of the manhole 14, carbon monoxide 6
000 volume ppm and aldehyde (as acetaldehyde) were 1300 volume ppm. Further, as a result of open inspection of the gas retention section 9, adhesion formation of carbide was observed. The results are shown in Table 2.

[0040]

[Table 2]

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, the above-mentioned high temperature portion of 200 to 300 ° C., which is present at the outlet of the reaction tube of the reactor at the time of catalytic vapor phase oxidation with ethylene and molecular oxygen to produce ethylene oxide, is cooled and cooled. Eliminate the occurrence of abnormal combustion reaction in the gas retention area that exists in the reaction product gas flow zone up to the reactor, stabilize the thermal efficiency, and increase the effect of suppressing the isomerization reaction to acetaldehyde which is an impurity It has the effect that

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for producing ethylene oxide according to the present invention.

FIG. 2 is an explanatory view showing another embodiment of the method for producing ethylene oxide according to the present invention.

[Explanation of symbols]

1: raw material gas supply conduit, 2: Vertical multi-tube heat exchange reactor, 3: reaction tube, 4: Preheating section, 5: Reaction part, 6: Inert substance filling section, 7: reaction product gas conduit, 8: Expansion joint for preventing thermal stress in piping, 9, 12: gas retention section, 10, 13: inert gas supply conduit, 11: cooler, 14: Manhole.

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-5-117217 (JP, A) European Patent Application Publication 567273 (EP, A 1) US Patent 4206128 (US, A) US Patent 4879396 (US, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C07D 301/08 C07D 303/04

Claims (3)

(57) [Claims] 1. A reactor used for producing ethylene oxide by catalytic vapor phase oxidation of ethylene with a molecular oxygen-containing gas at a reaction pressure of 0.59 to 4.02 MPa, downstream of the reaction tube outlet of the reactor and to a cooler. Manholes, safety valves, rupture discs, pressures in the reaction product gas flow zone between
More than a meter, thermometer and expansion joint
At least one gas retention portion selected et method of ethylene oxide which comprises suppressing the isomerization reaction to ethylene oxide of acetaldehyde generation by supplying an inert gas. 2. The temperature of the gas retention section is 200 to 300 ° C.
The method of claim 1, wherein 3. The residence time of the gas in the retention section is 1
The method according to claim 1 or 2 , which is within 2 hours.