JP2002187869A - Method for producing diacetoxybutene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the production efficiency of diacetoxybutene per catalyst in producing diacetoxybutene by reacting butadiene with acetic acid and oxygen in the presence of a solid catalyst containing palladium. SOLUTION: A reaction zone is made into a state that a solid catalyst exists in a liquid phase containing acetic acid and butadiene and an oxygen-containing gas containing >=7 mol% oxygen is introduced into the liquid phase so as to form fine bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing diacetoxybutene by reacting butadiene, acetic acid and oxygen. Diacetoxybutene is an important compound as an intermediate for producing 1,4-butanediol and tetrahydrofuran.

[0002]

2. Description of the Related Art In the presence of a solid catalyst containing palladium,
It is known to react butadiene, acetic acid and oxygen to produce diacetoxybutene. Since the reaction proceeds in the liquid phase, it is important to maintain the oxygen concentration in the liquid phase high by promoting the transfer of oxygen from the gas phase to the liquid phase in order to carry out the reaction efficiently. From this point of view, it is considered preferable that the reaction be carried out in such a manner that the catalyst is housed as a fixed bed in an atmosphere containing oxygen, and a liquid containing butadiene and acetic acid flows down on the catalyst surface. According to this type of reaction, the liquid level is always in contact with the oxygen atmosphere, and the liquid level is constantly renewed as it flows down, so that the dissolution of oxygen in the liquid is expected to be promoted.

[0003]

However, in the above reaction type, there is a risk of explosion, so that the oxygen concentration in the atmosphere must be lower than the lower explosion limit. The low oxygen concentration in the atmosphere naturally hinders the dissolution of oxygen in the liquid. Accordingly, an object of the present invention is to provide a method for promoting the dissolution of oxygen in a liquid to efficiently produce diacetoxybutene.

[0004]

According to the present invention, when diacetoxybutene is produced by supplying butadiene, acetic acid and oxygen to a reaction zone in which a solid catalyst containing palladium is present, the reaction zone is made to have an acetic acid state. And butadiene are formed in a state where the solid catalyst is present in the liquid phase, and an oxygen-containing gas containing 7 mol% or more of oxygen is introduced into the liquid phase so as to form fine bubbles. Diacetoxybutene can be produced efficiently.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, diacetoxybutene is produced by forming a reaction zone in a state where a solid catalyst is present in a liquid phase containing butadiene and acetic acid, and introducing an oxygen-containing gas into the reaction zone. Let it. That is, the reaction zone is entirely occupied by the liquid phase, into which oxygen-containing gas is introduced so as to form fine bubbles. This reaction method is different from the conventional reaction method described above, that is, a method in which a solid catalyst is held in a gaseous phase containing oxygen and a liquid phase containing butadiene and acetic acid flows down along the surface of the solid catalyst. This is a completely opposite reaction method from the viewpoint of dissolving oxygen into the gas. Introducing the oxygen-containing gas into the liquid phase as fine bubbles as in the present invention is extremely effective in promoting the dissolution of oxygen in the liquid. One of the reasons is that fine bubbles have a very large surface area per unit volume. Since the dissolution of oxygen from the gas phase to the liquid phase is performed via the interface between the two phases, a large surface area per unit volume of the oxygen-containing gas greatly promotes the dissolution of oxygen in the liquid phase. One of the other reasons is that a gas containing high concentration of oxygen can be used as the oxygen-containing gas. This utilizes the phenomenon that even if an oxygen-containing gas that forms an explosive composition under reaction conditions does not explode when present in the liquid as fine bubbles. Therefore, it is safe to introduce a gas containing a high concentration of oxygen as fine bubbles into a liquid phase containing butadiene and acetic acid. In addition, since the oxygen in the bubbles is immediately dissolved in the surrounding liquid phase, the oxygen concentration in the bubbles rapidly decreases. Therefore, if the residence time of the bubbles in the reaction zone is appropriate, the oxygen concentration in the bubbles will be significantly reduced by the time the bubbles flow out of the reaction zone, and sufficiently fall below the lower limit of the explosive composition.

[0006] The diameter of the bubble is usually 10 mm or less, preferably 5 mm or less, more preferably 3 mm or less, and particularly preferably 1 mm or less. As described above, in the present invention, since there is no possibility of causing an explosion, a high-concentration oxygen-containing gas can be used. Usually 7 mol% or more, preferably 1 mol%
An oxygen-containing gas containing 2 mol% or more of oxygen, for example, air is used. If desired, oxygen-enriched air or oxygen gas can be used. In a preferred embodiment of the present invention, an oxygen-containing gas which forms an explosive composition under the conditions of the reaction zone with a high oxygen concentration is supplied to the reaction zone, and the explosion occurs at the outlet of the reaction zone, taking advantage of the aforementioned characteristics. The residence time of bubbles in the reaction zone is controlled so that the oxygen concentration falls below the lower limit of the composition. In addition, under normal reaction conditions, that is, 3 to 8
Under the condition that the liquid phase is mostly occupied by acetic acid at a temperature of 60 to 120 ° C., the lower limit of the explosive composition can be estimated as a safe value by the following equation. What is necessary is just to determine the concentration of the oxygen-containing gas supplied to the reactor and the concentration of the oxygen-containing gas to be discharged from the reaction zone.

Y = −0.1 ｛(x / 0.098) −1｝ +12 (1) Y = −0.01 ｛(x / 0.098) −1｝ +6.6 (2) , Y is the lower oxygen concentration (mol%) that forms the explosive composition, and x is the reaction zone pressure (MPa). When x ≦ 6 MPa, equation (1) is used, and 6 <x ≦ 8 MPa
In a, the equation (2) is used.

In the present invention, the reaction can be carried out by a conventional method except that the oxygen-containing gas is introduced as fine bubbles into the liquid phase in the reaction zone. As the catalyst, a conventional palladium catalyst with a carrier, that is, a catalyst in which palladium and a cocatalyst such as bismuth, selenium, antimony, tellurium, and copper are supported on a carrier such as silica, alumina, or activated carbon may be used. The palladium content of the supported palladium catalyst is preferably from 0.1 to 20% by weight, and the content of the promoter component bismuth, selenium and the like is preferably from 0.01 to 30% by weight. Preferably, the catalyst is present as a fixed bed in the reaction zone.
Since this reaction is an exothermic reaction, a large amount of acetic acid also serves as a solvent in the reaction zone to facilitate temperature control in the reaction zone. The reaction temperature is controlled by supplying a reaction product flowing out of the reaction zone to a post-treatment step in which part of the reaction product is drawn out of the system to collect diacetoxybutene, and the remainder is cooled and circulated to the reaction zone. It is preferable to use the liquid phase circulation system. Freshly supplied acetic acid and butadiene are preferably mixed with this recycle stream and fed to the reaction zone. Also, the oxygen-containing gas can be introduced into the reaction zone after being dispersed in advance using a static mixer or the like so as to form fine bubbles in the circulation flow. When the oxygen-containing gas is directly introduced into the reaction zone, it is preferable to supply the oxygen-containing gas to the reaction zone from a plurality of locations using a sparger or the like so as to form fine bubbles. The ratio of the liquid phase introduced into the reaction zone, i.e. the circulating stream and the gas phase to the sum of freshly supplied acetic acid and butadiene, regardless of whether they are premixed in the circulating stream and introduced directly into the reaction zone, (Volume ratio) is usually preferably from 0.05 to 1.0. The acetic acid, butadiene and oxygen-containing gas supplied to the reaction zone are usually introduced into the reaction zone in a co-current flow.
If desired, it can also be introduced into the reaction zone in countercurrent.

FIG. 1 shows an example of a flow sheet for producing diacetoxybutene according to the method of the present invention. In the figure, 1
Reference numeral 01 denotes a reactor, which is packed with a solid catalyst containing palladium so as to form a fixed bed. The catalyst bed is preferably formed in a plurality of layers in a direction perpendicular to the flow in order to avoid drift. Reference numeral 102 denotes a supply pipe for the oxygen-containing gas. The supplied oxygen-containing gas is discharged from the lower part of the reactor through the sparger 103 as fine bubbles into the reactor. The gas and liquid phases flowing out of the reactor are:
The gas is introduced into the gas-liquid separator 105 via the conduit 104. The gas phase of the gas-liquid separator is drawn out of the system via a conduit 106. The liquid phase is withdrawn via conduit 107,
8. It is introduced into the reactor from below the reactor via a cooler 109 and a conduit 110. A liquid phase containing an amount of diacetoxybutene corresponding to the diacetoxybutene produced in the reactor is withdrawn from the middle of the conduit 107 via the conduit 111 and sent to a post-treatment step of recovering diacetoxybutene. In the middle of the conduit 110, raw materials butadiene and acetic acid are supplied via conduits 112 and 113, respectively. Note that butadiene and acetic acid may be supplied to the conduit 110 after the cooler 109. Of the liquid phase extracted from the gas-liquid separator,
It is usually 10 to 30 withdrawal from the system through the conduit 111.
% And the remaining 90-70% is recycled to the reaction zone. That is, a large amount of the liquid phase is supplied to the reactor 101 and the gas-liquid separator 1.
05 and the cooler 109, and the temperature of the reactor 101 is controlled to be constant by the circulating flow.

According to the present invention, a high-concentration oxygen-containing gas can be used, and oxygen can be rapidly dissolved in the liquid phase in the reaction zone.
The reaction amount of butadiene per unit time can be increased as compared with the conventional method.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 Diacetoxybutene was produced from butadiene and acetic acid according to the flow sheet shown in FIG. In the reactor, 5% by weight of Pd- with palladium and tellurium supported on silica was used.
1.5 wt% Te / SiO ₂ catalyst was filled so as to form a fixed bed. From the lower part of the reactor, a circulating liquid containing freshly supplied butadiene and acetic acid was placed at 77 ° C. and 6M.
Air was supplied at a flow rate of 20 m / sec through a sparger having a hole diameter of 3 mm so as to form fine bubbles. The supply of fresh butadiene and acetic acid is 1k of catalyst
0.223 kg / hr and 3.23 per g
It was 5 kg / hr. The supply amount of air is 1 kg of catalyst.
And the recycle stream withdrawn from the gas-liquid separator and introduced into the reactor was 14.306 kg / hr per kg of catalyst. The amount of butadiene contained in this circulation stream and introduced into the reactor was 0.055 kg / hr per kg of catalyst. When the reaction was continuously performed in this manner, the reaction rate of butadiene was 0.205 kg / hr per 1 kg of the catalyst. The air bubbles (diameter) blown from the sparger
Was 3-4 mm.

Example 2 In Example 1, the oxygen concentration was changed to 25.
A reaction for producing diacetoxybutene from butadiene and acetic acid was carried out in exactly the same manner as in Example 1 except that 0 mol% of oxygen-enriched air was used. The reaction rate of butadiene was 0.213 kg / hr / kg of catalyst.

Comparative Example 1 Diacetoxybutene was produced from butadiene and acetic acid by the gas circulation system shown in FIG. In the figure, reference numeral 201 denotes a first reactor filled with the same catalyst as in Example 1, and newly supplied butadiene and acetic acid are supplied to the upper portion of the reactor 201 at 77 ° C. and 6 MPa through conduits 202 and 203. did. Air was fed to the top of reactor 201 via conduit 204 and circulating gas conduit 205. The effluent from the reactor 201 was cooled to 77 ° C. in the cooler 206 and then supplied to the second reactor 207 filled with the same catalyst as the first reactor. In each of the first reactor 201 and the second reactor 207, the liquid phase flows down on the catalyst held in the gas phase atmosphere. The effluent from the second reactor was introduced into a gas-liquid separator 209 via a conduit 208. The liquid phase was drawn out of the system via a conduit 210, and the gas phase was circulated to the reactor 201 via a conduit 205. In addition, a cooler 211 and a compressor 212 were installed in the conduit 205, and a part of the circulating gas was extracted out of the system via the conduit 213. The feed rates of fresh butadiene and acetic acid were each 0.187 / kg of catalyst.
kg / hr and 8.111 kg / hr. Also,
The supply amount of air is 0.380 kg / hr per 1 kg of the catalyst.
The supply amount of the circulating gas supplied from the gas-liquid separator via the conduit was 2.708 kg / hr per kg of the catalyst. The amount of butadiene contained in this circulating gas and introduced into the reactor was 0.046 kg / hr per 1 kg of the catalyst. The oxygen concentration of the circulating gas after being mixed with the air supplied through the conduit 204 was 5.6 mol%. The reaction rate of butadiene is 0.186 kg / h per kg of catalyst.
r.

[Brief description of the drawings]

FIG. 1 is an example of a flow sheet when implementing the present invention.

FIG. 2 is an example of a conventional flow sheet.

[Explanation of symbols]

 Reference Signs List 101 reactor 102 oxygen-containing gas supply pipe 103 sparger 105 gas-liquid separator 108 circulation pump 109 cooler 112 butadiene supply pipe 113 acetic acid supply pipe 201 reactor 202 butadiene supply pipe 203 acetic acid supply pipe 204 oxygen-containing gas supply pipe 206 cooling Vessel 207 second reactor 209 gas-liquid separator 211 cooler 212 compressor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuyuki Okubo 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation Yokkaichi office F-term (reference) 4H006 AA02 AC48 BD84 BE30 KA13 4H039 CA66 CF10

Claims (8)

[Claims] 1. A method for producing diacetoxybutene by supplying butadiene, acetic acid and oxygen to a reaction zone in which a solid catalyst containing palladium is present, the reaction zone being formed in a liquid phase containing acetic acid and butadiene. Wherein diacetoxybutene is introduced in such a state that oxygen is contained in the liquid phase so as to form fine bubbles. 2. The process for producing diacetoxybutene according to claim 1, wherein the solid catalyst forms a fixed bed. 3. A method for producing diacetoxybutene by supplying butadiene, acetic acid and oxygen to a reaction zone in which a solid catalyst containing palladium is present, wherein the solid catalyst is fixed in a liquid phase containing acetic acid and butadiene. Acetic acid, butadiene, and oxygen are supplied to the reaction zone existing from below, and oxygen is used as an oxygen-containing gas containing at least 7 mol% of oxygen to form fine bubbles. And the liquid flowing out of the reaction zone is
A method for producing diacetoxybutene, wherein part of the diacetoxybutene is withdrawn to the outside of the system and the remainder is circulated to a reaction zone. 4. Of the liquids flowing out of the reaction zone, 10 to
The method for producing diacetoxybutene according to claim 3, wherein 30% is withdrawn from the system and 90 to 70% is circulated to the reaction zone. 5. The method for producing diacetoxybutene according to claim 1, wherein the oxygen-containing gas contains at least 12 mol% of oxygen. 6. The method according to claim 1, wherein the oxygen-containing gas is finely dispersed in a liquid containing acetic acid and butadiene to be introduced into the reaction zone, and then introduced into the reaction zone. A method for producing diacetoxybutene. 7. The method according to claim 1, wherein the oxygen concentration of the oxygen-containing gas supplied to the reaction zone is equal to or higher than the lower explosion limit, and the oxygen concentration of the oxygen-containing gas flowing out of the reaction zone is lower than the lower explosion limit. 7. The method for producing diacetoxybutene according to any one of claims to 6. 8. The process for producing diacetoxybutene according to claim 1, wherein the volume ratio of the oxygen-containing gas to the liquid supplied to the reaction zone is 0.05 to 1.0. Method.