JPS5827258B2 - Diacetoxybutene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating diacetoxybutene by distillation.

Specifically, the present invention relates to a method for distilling and separating a fraction containing 1,4-diacetoxybutene-2 as a main component from a reaction product obtained by reacting butadiene, acetic acid, and molecular oxygen.

Diacetoxybutene is an important starting material for the production of butanediol, which is used as a solvent or a raw material for industrially useful industrial chemicals, and various methods have been proposed for its production. A typical example is a method in which butadiene, acetic acid, and oxygen or an oxygen-containing gas are reacted in the presence of a palladium-based catalyst.

It is necessary to obtain the desired diacetoxybutene from the acetoxylation reaction product obtained by such a reaction method, but both the unreacted material and the desired material contained in the reaction product are compounds having unsaturated groups. Depending on how it is handled, a polymer may be formed, which may not only cause a decrease in yield but also cause operational problems.

As a result of intensive study on a method for obtaining desired diacetoxybutenes from acetoxy reactants, the present inventors found that diacetoxybutenes decompose, polymerize, etc. at a certain temperature and above that temperature. However, we have found that it can exist relatively stably at lower temperatures.

The present invention has been achieved based on this knowledge, and the gist of the present invention is to obtain 1,4- A method for separating diacetoxybutene, which comprises controlling the internal pressure of a distillation column and maintaining the bottom temperature at 190°C or lower when separating a fraction containing diacetoxybutene-2 as a main component by distillation. exists in

Next, the present invention will be explained in more detail.

The reaction product in the method of the present invention is an acetoxylation product obtained by reacting butadiene, acetic acid, and molecular oxygen in the presence of a palladium-based catalyst.

The acetoxylation reaction is not particularly limited and is carried out according to known methods.

Butadiene used as a raw material for the acetoxylation reaction may be pure or may contain an inert gas such as nitrogen or a saturated hydrocarbon such as methane, ethane, or bumene.

Further, acetic acid, which is one of the reaction raw materials, is not particularly limited, but it is desirable to use it in an anhydrous state as much as possible.

The catalyst used in this reaction is preferably palladium metal alone or a catalyst in which palladium metal and at least one promoter metal selected from bismuth, selenium, antimony, and tellurium are supported on a carrier.

Any carrier can be selected as the catalyst carrier, and specific examples thereof include activated carbon, silica gel, silica alumina, alumina, viscosity, bauxite, magnesia, diatomaceous earth, and pumice.

The amount of catalyst metal supported in the catalyst is usually 0 for palladium metal.
．． 1-20% (by weight), other promoter metals 0.01-3
It is selected at a concentration of 0 (weight)%.

These reactions are carried out by any method such as a fixed bed method, a fluidized bed method, or a suspended catalyst method.

The molecular oxygen blown into the reaction system is not necessarily pure oxygen, but may be oxygen diluted with an inert gas, such as air.

The reaction is usually carried out at a temperature of 40 to 180°C, preferably 60 to 150°C.
The test is carried out at a temperature range of ℃ and under pressure above normal pressure.

The acetoxylation reaction product obtained in this way contains unreacted butadiene, etc., so the reaction product is degassed to remove butadiene and impurities with boiling points close to butadiene, and then distilled according to the method of the present invention. It is desirable to do so.

The reactant after degassing treatment contains 1.4 as a reaction product.
-Diacetoxybutene-2 and isomers of diacetoxybutene, water produced by the reaction, acetic acid, and other high-boiling substances are included.

The proportion of these substances contained in the product varies depending on the reaction conditions, etc., and it is not possible to specify a uniform range, but it is usually found in butadiene derivatives including diacetoxybutenes, high-boiling substances, etc. is about 0.5 to 50% (by weight), and the amount of water** is about 0.05 to 20% (by weight).

In addition, the proportion of diacetoxybutenes in the butadiene derivative is 1,4-diacetoxybutene 250 to 95% (by weight), diacetoxybutene isomer 5 to 45% (by weight), based on the total weight of the derivative. High-boiling substances 0.1-10 (weight)%
It is.

Such acetoxylation reaction products are distilled according to the present method to obtain the desired product, although it is generally preferred to use a plurality of consecutive distillation columns.

For example, when diacetoxybutenes are desired, two distillation columns are used: a water and acetic acid distillation separation column (hereinafter referred to as A column) and a high-boiling substance separation column (hereinafter referred to as C column). The columns can be applied to any combination of A-C and C-A series.

However, it is preferable to apply the series A to C because trace amounts of high-boiling substances generated during distillation can be more fully removed.

When the purpose is to obtain 1,4-diacetoxybutene-2, a diacetoxybutene isomer separation column (hereinafter referred to as B column) is used in addition to the A column and C column.

In this case, the columns can be combined in any series of 1-B-C, C-A-B, and 1-CB, but it is preferable to operate in the order of AB-C.

In either case, Tower A will, as necessary,
Furthermore, it can be divided into two groups: a normal pressure group and a reduced pressure group.

During distillation according to the method of the present invention, it is necessary to adjust the pressure inside the column to maintain the bottom temperature of each distillation column at 190° C. or lower.

This is because, as is clear from Table 1 below, the thermal stability of diacetoxybutene-containing products is significantly lost at temperatures above 200°C.

(In this example, the total amount of diacetoxybutenes contained in the sample before heating to a predetermined temperature is 100, and the total amount of diacetoxybutenes after heating is shown.

) Experimental method Internal volume 300 m1. A Pyrex condenser and a temperature sensor for measuring the internal temperature of the Kolben were attached to the top of the three Pyrex Rokolben, and a nitrogen seal pipe was connected to the top of the reflux condenser.

Diacetoxybutene-containing liquids having the compositions shown in Table 1 were each placed in 150 gcolben, and after the air was replaced by bubbling with nitrogen, the mixture was sealed while nitrogen was flowing.

Next, the temperature was raised to a predetermined temperature using a heating medium, maintained at that temperature for 10 hours, and then allowed to cool to room temperature.

A portion of the contents was collected and analyzed by gas chromatography.

Sample liquid composition (wt%) Sample ■ 1 ・ 4 Butenediacetoxy 79.6 Sample ■ 3 ・ 4 Fan acetic acid and others ■ ・ 4 Fan and other diacetoxy Diacetoxy 10.2 8.2 2.0 98.5 1.5 Therefore, if the bottom temperature during distillation exceeds this temperature, the boiling point will decrease due to decomposition of diacetoxybutenes and the boiling point will increase due to polymerization, and the loss of diacetoxybutenes by distillation will be significantly large, which is economically disadvantageous. Furthermore, it becomes difficult to maintain stable distillation operating conditions due to the formation of low-boiling substances and the adhesion of high-boiling substances to the heating surface.

Furthermore, as the amount of high-boiling substances produced increases, the bottom temperature of the column must be raised to a higher temperature in order to effectively distill diacetoxybutene, and on the other hand, higher boiling temperatures promote higher boiling. This is undesirable because the amount of diacetoxybutenes is entrained in the high-boiling substances and is lost, which is disadvantageous.

As described above, it is necessary to maintain the bottom temperature at 190°C or lower, but it is usually desirable to maintain the temperature in the range of 190°C to 120°C.

At temperatures below 120'C, the operating pressure of the distillation column is 10To
rr or less, which is extremely disadvantageous for industrial operations, and also lowers the tower top temperature, which may undesirably cause acetic acid and 1,4-diacetoxybutene-2 to coagulate in the condenser.

The operating conditions for the distillation column are usually a column bottom temperature of 120 to 190°C.
The operating pressure was maintained at A tower 3o~250 (Torr),
B tower 10-230 (Torr), C tower 2-100 (T
orr).

Of course, the operating conditions can exceed this range, for example, by setting the A column to normal pressure and increasing the diacetoxybutene concentration.

As described above, the method of the present invention maintains the bottom temperature of each distillation column below a specific temperature when distilling the acetoxylation reactant to obtain the desired product, thereby decomposing or decomposing the product. The desired product can be obtained extremely effectively without causing side reactions such as polymerization.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example I Using a glass sieve tray type distillation column with 13 plates as the A column and a glass sieve tray type distillation column with 25 plates as the C column, the acetoxylation reaction product was continuously distilled under the following conditions. Diacetoxybutenes were obtained with a yield of 98%.

The acetoxylation reaction product subjected to distillation was prepared using a catalyst consisting of palladium and antimony supported on activated carbon (1% as palladium).
0 mmol/100 ft activated carbon, antimony 3
mmol/100? It is obtained by reacting butadiene, acetic acid, and oxygen in the presence of activated carbon), and its composition is 36.3% (by weight) of diacetoxybutenes, 0.7% (by weight) of high boilers, and the remainder is acetic acid and a very small amount of low-boiling impurities.

Comparative example Using the same equipment as in the previous example, Ace of the same composition The toxylated reaction product was continuously distilled under the following conditions.

As a result, the diacetoxybutenes extracted from the bottom of Column A were significantly colored and had high viscosity, making distillation operations in Column C difficult.

The yield of diacetquin butenes was 54%.

Claims (1)

[Claims] 1.1.4 from the reaction product obtained by reacting butadiene, acetic acid, and molecular oxygen in the presence of a palladium-based catalyst
- Separation of diacetoxybutene characterized by adjusting the internal pressure of the distillation column and maintaining the bottom temperature at 190°C or less when separating the fraction mainly composed of diacetoxybutene-2. Method.