JP2674699B2 - Ethyl acetate manufacturing method and its manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ethyl acetate and an apparatus for producing the same, and particularly to produce ethyl acetate with high yield and high efficiency by addition reaction of ethylene and acetic acid in the presence of a catalyst. The present invention relates to a manufacturing method and a reactor used for the manufacturing method.

[0002]

2. Description of the Related Art The present inventors previously submitted a process for producing ethyl acetate in a high yield by subjecting ethylene and acetic acid to an addition reaction in the gas phase in the presence of a solid catalyst (Japanese Patent Application Laid-Open No. Hei. Thirteen
9149). This manufacturing method comprises a step of contacting ethylene and acetic acid in the gas phase with a solid catalyst composed of a heteropolyacid or a heteropolyacid salt. When the manufacturing method is industrially carried out, the process shown in FIG. An isothermal type reactor using a shell-tube type reactor as shown is adopted. FIG. 2 shows an example of the above-mentioned isothermal reactor, which comprises a heater 2 for heating a mixed gas 1 of ethylene and acetic acid to a reaction start temperature, and a heated mixed gas 1 for a solid catalyst. It comprises a shell-tube type reactor 30 which is brought into contact with and reacted. This shell-tube type reactor 30 has a structure of a multi-tube heat exchanger, in which a group of parallel inner tubes 40 is filled with a granular solid catalyst, and one end of the group of inner tubes 40 The mixed gas 1 is circulated to the end portion, and the gas 50 that has undergone a contact reaction during this period is allowed to flow out. Since the addition reaction of ethylene and acetic acid is an exothermic reaction, in order to remove the reaction heat and keep the system isothermal, each inner tube constituting the inner tube group 40 is cooled by the introduction of the cooling medium 6 from the surroundings. The reaction temperature is maintained at a suitable temperature.

[0003]

Since the shell-tube type reactor 30 described above has a complicated structure and is expensive to install, a device having a simpler structure is required. The inner tube of the shell-tube type reactor has an elongated shape in order to enhance heat exchange efficiency.On the other hand, in this type of catalytic reaction, the solid catalyst generally undergoes gradual condensation during operation, resulting in catalytic activity. It reduces the gas flow rate and reduces the space velocity (SV value), so it is necessary to replace the catalyst after a certain period of operation. At this time, condensation occurs in the elongated tube. It takes a lot of labor and time to take out the spent catalyst, and the maintenance and management of the device is very expensive. Therefore, it is difficult to apply this device to a large-scale manufacturing process.

On the other hand, if an adiabatic reactor can be used instead of the shell-tube reactor, the adiabatic reactor is usually a single tube type, so the structure is simple and inexpensive, and the waste catalyst can be taken out. It will be easier. But,
When the adiabatic reactor is used in a usual manner, the reaction heat cannot be controlled, so that the catalyst layer in the reactor gradually becomes overheated during operation, and undesired side reactions such as polymerization and decomposition of ethylene occur, Not only does the conversion to ethyl acetate decrease, but so-called "runaway reaction" occurs, in which carbonaceous matter is deposited on the catalyst and the catalyst activity decreases, which further promotes side reactions. This can happen and this method cannot be adopted. The present invention has been made to solve the above problems, and an object thereof is to provide a production method capable of producing ethyl acetate with high yield and high efficiency using an adiabatic reactor, and an apparatus for producing the same. To provide.

[0005]

Means for Solving the Problems The above-mentioned problems are caused by sequentially flowing a mixed gas containing ethylene and acetic acid through at least two stages of adiabatic catalyst layers in series for reaction, and the above-mentioned two-stage adiabatic catalysts before and after the reaction. The problem can be solved by providing a cooling unit between the layers and providing a method for producing ethyl acetate which is cooled by the cooling unit to cool the mixed gas heated by the reaction heat in the adiabatic catalyst layer in the first stage and then flows in the second stage. In the above,
It is preferable to cool the mixed gas in the cooling unit so that the reaction temperature in the subsequent adiabatic catalyst layer rises to 30 ° C. or less. In the above reaction, it is preferable to adjust the space velocity (SV value) of the mixed gas flowing so that the total ethyl acetate conversion rate in each adiabatic catalyst layer is 50 to 90%. Further, the present invention is inserted between at least two stages of adiabatic reactors in series containing an adiabatic catalyst layer for circulating and reacting the above mixed gas, and two stages of adiabatic reactors before and after the adiabatic reactor. The present invention provides an apparatus for producing ethyl acetate, which comprises a cooler for cooling a mixed gas whose temperature is raised by reaction heat in an adiabatic reactor. In the above, it is preferable that the cooler suppresses the rise in the outlet temperature in the adiabatic reactor in the subsequent stage to 30 ° C. or less. In this manufacturing apparatus, the total conversion rate of ethyl acetate in each adiabatic reactor is 50 to 90%,
It is preferable that a means for adjusting the space velocity (SV value) of the mixed gas flowing is provided.

[0006]

[Function] Since the catalytic addition reaction between ethylene and acetic acid is an exothermic reaction, when an ordinary adiabatic catalyst layer is used to obtain ethyl acetate at a practical conversion rate, the temperature in the system gradually increases due to the heat of reaction. When it rises and exceeds the allowable limit, side reactions and runaway reactions finally occur. At this time, the adiabatic catalyst layer containing the required amount of catalyst is appropriately divided in the gas flow direction, and a cooling unit is provided between them to cool the mixed gas heated by the reaction heat in the preceding catalyst layer in the intermediate portion of the reaction system. By doing so, the heat of reaction in this addition reaction is relatively small, so that it is possible to prevent the temperature from exceeding the allowable limit and becoming excessive throughout the entire reaction system.

In the above system, it is effective to control the temperature of the mixed gas at the inlet of the system in order to prevent the temperature rise in the subsequent adiabatic catalyst layer from becoming excessive. It was found that when the temperature rise in the adiabatic catalyst layer exceeds 30 ° C., undesired phenomena such as side reactions, carbonaceous deposits, and runaway reactions appear, so that the reaction temperature rise in the adiabatic catalyst layer in the subsequent stage is 30 ° C. or less. Cooling the mixed gas in the cooling section is effective for improving the ethyl acetate conversion rate.

At this time, the total conversion rate of acetic acid to ethyl acetate in each adiabatic catalyst layer should be 50 to 90%.
When the space velocity (SV value) of the mixed gas flowing is adjusted,
The space-time yield (STY) can be increased while maintaining the entire reaction system within a preferable constant temperature range.

Next, the method for producing ethyl acetate of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the device of the present invention. This ethyl acetate production apparatus comprises a heater 2 which heats a mixed gas 1 of ethylene and acetic acid to an initial reaction temperature and introduces it into an adiabatic reaction system, three stages of adiabatic reactors 3, 13 and 23 in series, It is provided with coolers 12 and 22 inserted between two stages of adiabatic reactors (3-13) and (13-23) arranged in front and rear. The adiabatic reactors 3, 13, and 23 respectively accommodate adiabatic catalyst layers 4, 14, and 24 containing a solid catalyst composed of a heteropolyacid or a heteropolyacid salt that allows the mixed gas 1 to flow and react in the gas phase. . Further, the coolers 12 and 22 are adapted to cool the mixed gas whose temperature has been raised by the heat of reaction in the adiabatic reactors 3 and 13 in the preceding stages, respectively.

Next, an example of a method for producing ethyl acetate using the above apparatus will be described. First, a mixed gas 1 of ethylene and acetic acid is supplied to the heater 2. The heater 2 heats the mixed gas 1 to a temperature (initial temperature) at which the reaction smoothly starts in the presence of the catalyst. The heated mixed gas is then introduced into the first adiabatic reactor 3. Since this reactor contains the adiabatic catalyst layer 4 filled with the solid catalyst composed of heteropolyacid or heteropolyacid salt, a part of the mixed gas reacts here to be converted into ethyl acetate and also generates heat. The temperature rises above the initial temperature. The mixed gas 5 that has risen in temperature and flows out is then cooled by the cooling unit (cooler 12) provided between the two stages of the adiabatic catalyst layers (4-14) located in front of and behind it. The cooled mixed gas is then passed through the adiabatic catalyst layer 14 in the subsequent stage, where unreacted ethylene and acetic acid are partially converted to ethyl acetate. The heated mixed gas 15 flowing out from the adiabatic catalyst layer 14 is cooled by the cooling unit (cooler 22) provided between the two adiabatic catalyst layers (14-24) in the front and rear, and then in the subsequent stage. Part of the ethylene and acetic acid that remain in the heat-insulating catalyst layer 24 and remain unreacted is converted into ethyl acetate, and is recovered as the product gas 25.

The ethylene and acetic acid used in the production method of the present invention may be produced by any production method and are not particularly limited. It is preferable to add steam to the mixed gas 1 in order to maintain the activity of the catalyst. Also, vapor phase acetic acid necessarily contains water vapor. The preferable supply amount of the mixed gas to be introduced into the device of the present invention is 1 in terms of space velocity (SV value) with respect to the total amount of catalyst charged in the device.
000-2800 / hour, more preferably 1400-2
It is about 300 / hour. Further, the pressure of this apparatus is selected so that the gas in the system, including the water content, maintains a gas phase state and a sufficient reaction temperature and reaction rate are obtained.
Generally, it is preferable to operate at 5 to 12 atm. A suitable initial temperature for heating the mixed gas 1 with the heater 2 is, for example, 1
It is 30-170 degreeC. If it is lower than 130 ° C, the reaction in the adiabatic reactor 3 does not proceed sufficiently, and if it exceeds 170 ° C, side reactions increase, which is not preferable.

The adiabatic catalyst layers 4, 14 and 24 are formed by filling a solid catalyst composed of a heteropolyacid or a heteropolyacid salt. Examples of this heteropolyacid include phosphomolybdic acid, phosphotungstic acid, silicotungstic acid and the like. Examples of the heteropolyacid salt include phosphomolybdic acid, phosphotungstic acid,
Mention may be made of cesium salts of silicotungstic acid, rubidium salts, thallium salts, ammonium salts, potassium salts and the like, or combinations thereof. It is particularly preferable to use the above-mentioned heteropolyacid salt. The form of the catalyst used may be any as long as it can form an adiabatic catalyst layer, for example, spherical, cylindrical extruded form, granules, pellets,
Granules and tablets can be used. However, a spherical shape, an extruded shape, and the like, which have high catalyst strength and are capable of uniformly filling the reactor, are particularly preferable.

In the cooling section (coolers 12, 22),
It is preferable to cool the mixed gas so that the reaction temperature in the subsequent adiabatic catalyst layers 14, 24 rises to 30 ° C. or less. This is achieved by adjusting the temperature of the gas flowing out from each cooling unit to 140 to 180 ° C. under the above reaction conditions. If it is lower than 140 ° C, the conversion rate to ethyl acetate is remarkably lowered, and if it exceeds 180 ° C, the reaction in the adiabatic catalyst layer becomes so radical that the outlet temperature rises above 30 ° C. In this case, the so-called runaway reaction of the catalyst occurs and the temperature is likely to rise rapidly. For example, the generation rate of ethyl alcohol, which is a by-product, is 1.5 at the gas outflow portion of the adiabatic catalyst layer compared to the gas introduction portion. It will be more than doubled.

It is preferable that each of the adiabatic catalyst layers 4, 14 and 24 has a similar structure. Here, "similar" means that they have the same function of reacting ethylene and acetic acid to produce ethyl acetate, and their structure, shape, and type of solid catalyst composed of heteropolyacid or heteropolyacid salt. The filling amount, the filling density, the presence or absence of other fillings, the space velocity with respect to the supply gas, the reaction initiation temperature, and the like may be the same or different from each other.

In the apparatus of the embodiment, three stages of adiabatic reactors are connected. However, the number may be two or more, and for example, it is preferably 3 to 5. The number of stages is set to a desired constant value for the entire adiabatic catalyst layer in consideration of the degree of temperature rise in each adiabatic catalyst layer 4, 14, 24, ... And the gas temperature in each cooling unit (cooler 12, 22, ...). While maintaining the temperature range, at the above space velocity (SV value), the ethyl acetate conversion rate was 50 to 90 throughout the entire apparatus.
It is preferably selected so as to be%.

Each adiabatic catalyst layer 4, 14, 24, ...
The ethyl acetate conversion rate of acetic acid in (2) is not particularly limited, but it is preferable to make them substantially equal to control not only easy but also to suppress side reactions and obtain a high total conversion rate. The total conversion rate in this device is 50-
It is preferable to adjust the SV value so that it becomes 90%.
It is generally considered that a higher conversion rate is preferable, but 9
When the content exceeds 0%, the reaction rate decreases and the reverse reaction increases, so that the space-time yield of ethyl acetate (STY)
Is lowered, and an extremely large amount of catalyst is required to compensate for this, which is not preferable. From this viewpoint, the preferable conversion rate is about 70%. This conversion can be achieved by controlling the SV value in the constant manufacturing apparatus of the present invention.

In the above ethyl acetate producing apparatus, the type of the adiabatic reactors 3, 13, 23, ... For accommodating the adiabatic catalyst layer is not particularly limited, but it is a covered cylindrical body having an adiabatic wall. It is preferable that the one end has a gas introduction hole, the other end has a gas outflow hole, and the heat insulating catalyst layer is housed in the center of the cylinder. In particular, it is preferable that the adiabatic catalyst layer is composed of a catalyst deposit whose both ends are supported by removable meshes so that the catalyst can be easily replaced. The adiabatic reactor may be installed vertically or horizontally, but the vertical type is advantageous in that it requires a smaller installation area.

In this device, the coolers 12, 22, ...
Any of those known as ordinary gas heat exchangers such as double pipe type, multi-pipe type, spiral pipe type, finned pipe type, layered type can be used, and its refrigerant is also used. ,
Any of air, water, oil, volatile refrigerant, and the like can be used as long as the gas passing therethrough can be cooled to a predetermined temperature. Further, instead of using a separate cooler, a jacket for passing a refrigerant is provided on the outer periphery in the vicinity of the gas introduction hole or gas outflow hole of the adiabatic reactor, thereby providing a cooling unit for cooling the introduced gas. It may be. Further, it is also possible to use an apparatus in which a heat insulating catalyst layer accommodated in one elongated heat insulating reactor is divided into front and rear two stages, and a cooling unit such as a multi-tube type is provided in the middle of the heat insulating reactor. it can. However, acetic acid and water condense on the wall surface where heat is exchanged and contact with the catalyst deteriorates the catalyst.Therefore, the cooling unit is preferably separated from the adiabatic reactor as a cooler, and the temperature of the refrigerant is It is preferable that the dew point of the mixed gas flowing through the cooler is exceeded. The use of pressurized hot water as the refrigerant is advantageous not only in this respect but also because the amount of temperature rise after heat exchange can be recovered as steam.

The means for adjusting the SV value so that the total conversion rate of ethyl acetate in the adiabatic reactor is 50 to 90% is determined by the inlet / outlet temperature of each adiabatic reactor of the production apparatus and the mixing at the outlet. A measuring instrument that continuously measures the ethyl acetate concentration of the gas during the operation period, and control the temperature at each cooling unit outlet so that the concentration at the final adiabatic reactor outlet is maintained at the set value. It is preferable to have a control mechanism for automatically controlling the gas flow rate throughout the apparatus.

[0020]

Next, an embodiment of the present invention will be described. (Experimental device) An ethyl acetate production device was constructed by connecting three vertical tubular reactors having an inner diameter of 24 mm in series. Each reactor is referred to as a first reactor, a second reactor, and a third reactor in this order in the reaction gas flow direction. A temperature control unit was provided at the top of each of the reactors, and a catalyst was filled in the lower stage to form an adiabatic catalyst layer. (Catalyst) The catalyst used in this example is a tableting type of cesium phosphotungstic acid salt having a diameter of 5 mm. This catalyst was prepared as follows. In a 300 ml flask, 150 g (about 0.0438 mol) of a commercially available phosphotungstic acid reagent (manufactured by Wako Pure Chemical Industries) and 60 ml of pure water were mixed and dissolved. Separately, cesium nitrate (CsNO ₃ )
21.5 g (0.110 mol) was dissolved in water, and this was added dropwise to the above phosphotungstic acid aqueous solution with stirring using a dropping funnel. Simultaneously with the dropwise addition, white fine-grained crystals of cesium phosphotungstic acid salt were deposited. The flask is immersed in a hot water bath to evaporate the water content, and the remaining lumps are placed in a petri dish and placed in a drier.
Dried for hours. The dried product obtained was crushed and made into tablets having a diameter of 5 mm using a tableting machine.

(Example 1) Using the above-mentioned reactor, the reaction was carried out in each reactor as follows. (First Reactor) Under the condition of pressure of 9.3 atm, ethylene, acetic acid, water and an inert gas were each added to 80.0:
6.7: 3.0: 10.3 mixed at a molar ratio of 231 g /
At a flow rate of hr, it flows through the temperature control section of the first reactor to 158
The catalyst was heated to 0 ° C., and then the above catalyst was passed through the catalyst layer filled with 30 cm ³ from the top for reaction. The amount of ethyl acetate produced in this reactor was 8.8 g / hr. The outlet temperature of the catalyst layer was 173 ° C.

(Second Reactor) The mixed gas flowing out of the first reactor was circulated through the temperature control section of the second reactor and cooled to 160 ° C., and then the catalyst layer filled with 40 cm ^{3 of the} above catalyst was charged from the top. It was distributed and reacted. The amount of ethyl acetate produced in this reactor was 11.4 g / hr. The outlet temperature of the catalyst layer was 179 ° C.

(Third Reactor) The mixed gas flowing out of the second reactor was circulated through the temperature control section of the third reactor to be cooled to 163 ° C., and then the above catalyst was charged in 40 cm ^{3 of} the third reactor. The catalyst layer was circulated from the top and reacted. The amount of ethyl acetate produced in this reactor was 10.3 g / hr. The outlet temperature of the catalyst layer was 179 ° C., and the outlet pressure was 8.9 atm.

When the total reaction rate of the addition reaction of ethylene and acetic acid in the adiabatic reactor comprising the above three reactors was calculated, the conversion rate of acetic acid was 66.1%, and ethylene to ethyl acetate was obtained. The selectivity was 94.3%. In addition,
The total SV value is 1730 / hr, and the space-time yield (S
TY is 277 g (ethyl acetate production amount) / l (catalyst amount)
/ Hr.

The results of the above examples show that the heat of reaction generated during the catalytic reaction is generated by allowing the mixed gas, which has been heated in the adiabatic catalyst layer in the preceding stage, to be cooled in the cooling section and then passed through the adiabatic catalyst layer in the subsequent stage. It shows that ethyl acetate could be produced in high yield and high efficiency by being effectively removed successively and maintaining a certain range of reaction temperature.

(Comparative Example 1) Using the same experimental equipment as in the example and the catalyst prepared in the same manner, the reaction was carried out as follows. (First Reactor) Under the condition of pressure of 9.3 atm, ethylene, acetic acid, water and an inert gas were each added to 80.0:
6.8: 3.1: 10.1 mixed at a molar ratio of 238 g /
159 at a flow rate of hr
The catalyst was heated to 0 ° C., and then the above catalyst was passed through the catalyst layer filled with 30 cm ³ from the top for reaction. The amount of ethyl acetate produced in this reactor was 9.1 g / hr. The outlet temperature of the catalyst layer was 175 ° C. (Second reactor) Without cooling the mixed gas flowing out from the first reactor, the outlet temperature of the first reactor is maintained and the catalyst layer of the second reactor is filled with 40 cm ³ of the above-mentioned catalyst and is circulated from the top. And reacted. At this time, the outlet temperature of the second reactor continued to rise. When the outlet temperature of the second reactor reached 226 ° C, the flow of the mixed gas was stopped and the catalyst layer was replaced with an inert gas. After cooling, the reactor was opened and the catalyst was observed. As a result, carbonaceous deposits were found on the catalyst in the second reactor, and catalyst deterioration was observed. The results of the above comparative examples show that a runaway reaction occurs unless proper cooling of the mixed gas is performed between the adiabatic reactors.

[0027]

According to the method for producing ethyl acetate of the present invention, a cooling unit is provided between the two adiabatic catalyst layers in the front and back to cool the mixed gas heated by the reaction heat in the preceding adiabatic catalyst layer. Therefore, the temperature of the mixed gas is always maintained within a certain range, side reactions due to temperature rise are prevented, and ethyl acetate can be produced at a high conversion rate. At this time, the reaction temperature in the subsequent adiabatic catalyst layer rises by 30 ° C.
If the mixed gas is cooled in the cooling section as described below,
The runaway reaction is prevented, the conversion rate of ethyl acetate is improved, and the deposition of carbonaceous material on the catalyst is prevented, so that the catalyst life can be extended.

The apparatus for producing ethyl acetate according to the present invention comprises at least two stages of adiabatic reactors in series containing an adiabatic catalyst layer for allowing a mixed gas to flow therethrough for reaction, and two stages of adiabatic reactors before and after the reactor. Since it has a cooler which is inserted between them and cools the gas mixture heated in the adiabatic reactor in the previous stage, the reaction heat generated during the catalytic reaction is effectively effective in the intermediate stage of the reaction. Can be removed, and despite the use of an adiabatic reactor with a simple structure, side reactions are suppressed and the catalyst life can be extended. If this cooler suppresses the rise of the outlet temperature in the subsequent adiabatic reactor to 30 ° C. or less, precipitation of carbonaceous matter or runaway reaction in the adiabatic reactor is prevented, and acetic acid is efficiently and smoothly transferred. Ethyl can be produced. As described above, the adiabatic reactor of the present invention has a simple structure as compared with the conventional shell-tube reactor and the like, so that not only the equipment cost is low, but also the filling and replacement of the catalyst are extremely easy. Therefore, the maintenance cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a process drawing showing an embodiment of the method for producing ethyl acetate and the production apparatus of the present invention.

FIG. 2 is a process drawing showing an example of a conventional ethyl acetate production method and production apparatus.

[Explanation of symbols]

1 ... Mixed gas, 4, 14, 24 ... Adiabatic catalyst layer, 12, 2
2 ... Cooling unit.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-55-102536 (JP, A) JP-A-4-139149 (JP, A) JP-A-5-255185 (JP, A) JP-B-47- 38414 (JP, B1)

Claims (4)

(57) [Claims] 1. When producing ethyl acetate, a mixed gas containing ethylene and acetic acid is sequentially passed in a gas phase through at least two stages of adiabatic catalyst layers in series containing a solid catalyst composed of heteropolyacid or heteropolyacid salt. The reaction is performed by allowing the reaction to occur, and a cooling unit is provided between the two preceding and following adiabatic catalyst layers. The mixed gas heated by the heat of reaction in the adiabatic catalyst layer in the preceding stage is cooled in this cooling unit and then cooled in the subsequent stage. A method for producing ethyl acetate, which is characterized in that 2. The method for producing ethyl acetate according to claim 1, wherein the reaction temperature in the subsequent adiabatic catalyst layer increases by 30 ° C.
A method for producing ethyl acetate, characterized in that the mixed gas is cooled in the cooling section as described below. 3. An apparatus for producing ethyl acetate, comprising at least two stages of adiabatic catalyst layers containing a solid catalyst composed of a heteropolyacid or a heteropolyacid salt which causes a mixed gas containing ethylene and acetic acid to flow and react. It has an adiabatic reactor in series and a cooler that is inserted between the two adiabatic reactors in front of and behind the adiabatic reactor, and cools the mixed gas heated by the reaction heat in the adiabatic reactor in the previous stage. Equipment for producing ethyl acetate. 4. The apparatus for producing ethyl acetate according to claim 3, wherein the cooler suppresses an increase in the outlet temperature of the subsequent adiabatic reactor to 30 ° C. or lower.