JPS5943449B2 - Dichlorobutene isomerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for the isomerization of 3,4-dichlorobutene-1 to 1,4-dichlorobutene-2 and vice versa.

The purpose of the present invention is to suppress the by-product of tar-like high-boiling substances and prevent clogging of the equipment by reacting dichlorobutene at a relatively low temperature in the presence of a highly active catalyst in a method for isomerizing dichlorobutene. The objective is to obtain the target dichlorobutene in good yield.

Conventionally, copper, iron,
There is a method in which one or more metal salts such as zinc or aluminum are added to dichlorobutene and heated. However, since these generally have low catalytic activity, various additives are added to the metal salt to increase the activity. For example, British Patent No. 7
In No. 98889, an organic amine was added to a copper salt, and JP-A-46-1
In 514, organic nitrile was added to copper naphthenate, and JP-A-47
-11560 uses organic dihydroxy compounds in JP-A No. 4
No. 7-18808 added a chlorinated derivative of aniline, and Japanese Patent Publication No. 48-42853 added amine hydrochloride to cuprous chloride. As a result of various studies conducted by the present inventor, amines have many tar-like high boiling point by-products, and the catalysts shown in the comparative examples shown in Table 3 do not exhibit sufficient activity unless the catalyst concentration is increased. However, the examples shown in Table 1 showed high activity even at low catalyst concentrations.

In addition to being active, the isomerization catalyst is required to have low decomposition of dichlorobutene, little by-product of high-boiling substances, and no corrosivity to the equipment. Decomposition of dichlorobutene and generation of tar-like high-boiling substances not only reduce the yield of dichlorobutene but also clog the equipment and reduce its operating rate. Further, although the larger the amount of catalyst added, the higher the catalytic activity is in many cases, it is desirable to keep the amount as small as possible in consideration of economy and waste catalyst recovery treatment. The present inventors have discovered a catalyst that satisfies these requirements and have completed the isomerization method of the present invention.

That is, the method for isomerizing dichlorobutene of the present invention includes 3, 4
The present invention is characterized in that cuprous chloride and α-pipecoline are used as isomerization catalysts in isomerizing between -dichlorobutene-1 and 1,4-dichlorobutene-2.

The catalyst used in the present invention had high catalytic activity despite the low catalyst concentration in dichlorobutene, produced little tar-like and solid by-products, and was hardly corrosive to equipment.

The concentration of the catalyst is 0.0 cuprous chloride to cyclobutene.
The concentration of α-pipecoline is preferably 0.05 to 4% by weight, particularly preferably 0.1 to 1% for cuprous chloride and 0.1 to 1% for α-pipecoline. The isomerization reaction temperature is 8
The temperature is 0 to 120°C, preferably 85 to 95°C. When the temperature is low, the reaction rate is low, and when the temperature is high, the decomposition of dichlorobutene and the amount of by-products of high-boiling substances increase. The reaction pressure can be atmospheric pressure, increased pressure, or reduced pressure. The present invention may be carried out by either a batch method or a continuous method using a distillation column, but industrially the most preferred method is a method in which a catalyst is added to the bottom of the distillation column and the desired isomer is taken out as a distillate or bottom product. It is.

In this case, the distillation is carried out, for example, from 40 to 100 m77tIg (
(absolute pressure), the reaction is preferably carried out at the boiling point of dichlorobutene. If necessary, a reactor may be provided, and dichlorobutene may be circulated between the reactor and the bottom of the column. When a continuous method is used, it is necessary to extract a portion of the liquid at the bottom of the column to the outside of the system in order to prevent the accumulation of high-boiling substances. At this time, the catalyst is also lost, so it is desirable to add new catalyst to maintain a constant catalyst concentration. The present invention will be explained in more detail below by giving Examples and Comparative Examples. Example 250 ml of 1,4-dichlorobutene-2 or 3,4-dichlorobutene-1 was charged into a 300 ml four-walled flask equipped with a stirrer and a condenser, and heated while stirring.

Cuprous chloride and α-pipecoline were simultaneously added to the flask while controlling the desired reaction temperature. Even after the addition of the catalyst, the mixture was allowed to react for 60 minutes while maintaining a predetermined reaction temperature, and then sampled and analyzed using gas chromatography. The results of the examples are shown in Tables 1 and 2. Table 1 is 1,
Table 2 shows isomerization of 4-dichlorobutene-2 and 3,4-dichlorobutene-1. In the table, 3,4-DC
B represents 3,4-dichlorobutene-1, and 1,4-DCB represents 1,4-dichlorobutene-2. Also,
The composition of dichlorobutene used in the test is shown as a raw material in the catalyst column. Concentrations of catalyst and additives are in weight percent relative to cyclobutene. Comparative Example Measurement was performed using a known isomerization catalyst in exactly the same manner as in the example.

The results of the comparative examples are shown in Tables 3 and 4. Table 3 is 1,4
Table 4 shows isomerization of 3,4-dichlorobutene-1. A commercially available copper naphthenate containing 10% copper was used.

Claims (1)

[Claims] 1 Isomerization of dichlorobutene characterized by using cuprous chloride and α-pipecoline as an isomerization catalyst in performing isomerization between 3,4-dichlorobutene-1 and 1,4-dichlorobutene-2 Method.