GB2051059A - Process for producing dichlorobutene - Google Patents

Abstract

Dichlorobutene is produced by feeding chlorine and 1,3-butadiene into a solution of benzonitrile containing a copper chloride. The yield is high and the normally expected by- products of tar and carbonized solids are not formed. The copper chloride is preferably used in an amount of 0.1 to 25 wt. parts per 100 wt. parts of benzonitrile.

Description

SPECIFICATION Process for producing dichlorobutene The present invention relates to a process for producing dichlorobutene by a chlorination of 1,3butadiene in the liquid phase.

Dichlorobutene can be produced by reacting chlorine with 1 3-butadiene at 1 50 ro 3000C in the vapor phase. This process produces undesirabie by-products of tar and carbonized solids though the yield is high.

It is also known to carry out a chlorination of 1,3-butadiene with chlorine in the liquid phase at a low temperature, for example, chlorination at a 1:1 moiar ratio in carbon tetrachloride with sulfur at 200C as disclosed in Japanese Examined Patent Publication No. 1 9564/1 967, and introducing 1,3butadiene into a chlorinated organic solvent in the presence of a catalyst such as ferric chloride at OOC, as disclosed in Japanese Unexamined Patent Publication No. 83,304/1975. No carbonized solid is formed in these processes, which are easy to carry out. It is, however, necessary to carry out the reaction at low temperature and a large quantity of expensive coolant is required in order to give a yield higher than about 90%.

It is an object of the present invention to overcome such disadvantages and to provide a process for producing dichlorobutene in high yield without forming carbonized by-products, and if desired at a relatively higher temperature.

The present invention provides a process for producing dichlorobutene which comprises feeding chlorine and 1 ,3-butadiene into a solution of benzonitrile containing a copper chloride.

The copper chlorides used in the present invention can be cuprous chloride or cupric chloride. The precise content of copper chloride is not critical, but when it is too small, the yield of dichlorobutene is low whereas when it is too high a slurry of the copper chloride is formed which gives rise to operational difficulties. Therefore the content of the copper chloride is preferably in a range of 0.1 to 25 wt. parts based on 100 wt. parts of benzonitrile.

The concentration of benzonitrile is not critical. It is possible to use a solvent which is substantially inert to chlorine, by mixing it with benzonitrile. It is, however, preferable to use benzonitrile in the substantial absence of any other solvent since the yield is low when the concentration of benzonitrile is too low. The solvent mentioned above does not include the reaction product.

The reaction temperature is not critical but is preferably in a range of O to 1 500 C. When it is lower than OOC, an expensive coolant is required for removing the heat of reaction and the yield is too low whereas when it is higher than 1 500 C, the yield is also too low.

In the process of the present invention, the pressure for the reaction is not critical and can be atmospheric pressure, a reduced pressure or an elevated pressure.

The pressure can be selected according to the method used for separation of the dichlorobutene from the reaction mixture. For example, when a reactor equipped with a distillation tower is used to separate dichlorobutene by distillation at the time of the reaction, a reduced pressure can be selected.

When dichlorobutene is not separated at the time of the reaction, the reaction can be carried out under atmospheric pressure, a reduced pressure or an elevated pressure.

The purity of 1 ,3-butadiene used in the process of the present invention is not critical and, for example, a mixed gas of 1 ,3-butadiene and butene can be used. The ratio of 1 ,3-butadiene to chlorine is preferably more than equimolar, but it is not critical.

EXAMPLES 1 to 8 In a 500 ml. reactor equipped with a stirrer, a condenser, a thermometer, a chlorine inlet and a butadiene inlet, 200 ml. of benzonitrile and cuprous chloride were added and the mixture was thoroughly mixed until a predetermined temperature was reached. 1 ,3-Butadiene and chlorine were fed into the reactor to initiate the reaction. After the reaction had been allowed to proceed for two hours by feeding 1 ,3-butadiene and chlorine, the feeding of 1 ,3-butadiene and chlorine was stopped. The reaction mixture was analyzed by gas chromatography. The conditions and the compositions of the reaction products are shown in Table 1 wherein the references are as follows: MCB: monochlorobutene and monochlorobutadiene: DCB: dichlorobutene: TrCB: trichlorobutene: TeCB: tetrachlorobutane: PCB: pentachlorobutane and higher boiling components.

TABLE 1

Example 1 2 3 4 5 6 7 8 1 I Amount of cuprous 7.95 7.95 7.95 7.95 7.95 7.95 7.95 15.90 chloride (g) Rate of chlorine 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 (molihr.) Ratio of 1,3-butadiene/ 1.1 1.1 1.1 1.1 2.0 3.0 2.0 1.1 chlorine (mol/mol) Reaction temperature 10 30 50 80 80 80 105 80 ( C) Composition of Reaction products:: (mol %) MCB 0.1 0.2 0.0 0.1 0.1 0.1 0.8 0.2 DCB 95.7 96.1 96.3 95.3 97.3 97.2 95.0 98.5 TrCB 0.1 0.2 0.3 1.3 0.2 0.3 1.7 0.2 TeOB 4.1 3.5 3.3 3.0 2.3 2.3 2.4 3.1 PCB 0.0 0.0 0.1 0.3 0.1 0.1 0.1 0.0 REFERENCE In the reactor used in Examples 1 to 8, 200 ml. of benzonitrile was charged and mixed to heat it to 800 C. 1 ,3-Butadiene and chlorine were respectively fed at rates of 24.6 liter/hr. and 22.4 liter/hr. to initiate the reaction. After the reaction was continued two hours, the feeding of butadiene and chlorine was stopped. The reaction mixture was analyzed by a gas chromatography.

The composition of the reaction products was as follows.

MCB : 2.4 mol% DCB : 88.1 mol% TrCB : 3.0 mol % TeCB : 4.7 mol% PCB : 1.8 mol%.

Claims (5)

1. A process for producing dichlorobutene which comprises feeding chlorine and 1 > 3-butadiene into a solution of benzonitrile containing a copper chloride.

2. A process according to claim 1 wherein the copper chloride is cuprous chloride or cupric chloride in an amount of 0.1 to 25 wt. parts per 100 wt. parts of benzonitrile.

3. A process according to claim 1 or claim 2 wherein the reaction is carried out at 0 to 1 60 G.

4. A process for producing dichlorobutene according to any preceding claim wherein the molar ratio of 1 ,3-butadiene to chlorine is higher than 1:1.

5. A process according to claim 1 substantially as herein described with reference to the Examples.