JPS6137254B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention prefers 1.3 to 1.2-dichloropropane.
- Concerning a method for producing dichloropropene. 1,3-Dichloropropene is a compound useful as a raw material for agricultural chemicals and other organic synthesis, and is conventionally known to be obtained as a by-product when producing allyl chloride through high-temperature chlorination of propylene. , when the purpose is to synthesize it, the main method is to chlorinate allyl chloride at high temperature (Japanese Patent Publication No. 38-26355, Japanese Patent Publication No. 47-30682,
USP2688642, USP2430320). However, the method using allyl chloride as a raw material is not economical because allyl chloride is relatively expensive, and is also highly reactive and produces many by-products, making it difficult to obtain a sufficient yield. In addition, because it is unstable to heat, carbon formation and fixation in the reaction system are significant.
There are problems in controlling the reaction and maintaining stable operation over a long period of time, and it is difficult to say that this method is satisfactory as an industrial production method. The present inventors focused on 1,2-dichloropropane, which can be obtained relatively inexpensively and has no suitable use other than being used as a solvent, and used it as a raw material to produce 1,3-dichloropropene. As a result of various experimental studies on methods for industrially advantageous production, the method of the present invention has been completed. That is, the present invention uses 1,2-dichloropropane as
Thermal decomposition is carried out at 450 to 600°C, and components with a boiling point of 30 to 55°C are separated from the decomposition products, and a portion of the remaining 2-chloropropene fraction and unreacted 1,2-dichloropropane fraction are separated. while circulating the fraction to the pyrolysis reactor.
It is an object of the present invention to provide a method for producing 1,3-dichloropropene, characterized in that the separated decomposition product with a boiling point of 30-55°C is reacted with chlorine at 450-560°C. The method of the present invention will be explained in more detail below. When 1,2-dichloropropane is thermally decomposed at high temperatures, a mixture of monochloropropene isomers such as cis1-chloropropene, trans1-chloropropene, 2-chloropropene, and 3-chloropropene (allyl chloride) is produced, and thermal decomposition occurs. It is known that when the temperature is high, further dehydrochlorination reactions occur, producing unsaturated hydrocarbons such as benzene, methylacetylene, cyclopropene, and propadiene, and carbonization reactions such as coking also occur. . Most of the conventionally known research on the thermal decomposition of 1,2-dichloropropane has been aimed at obtaining allyl chloride in high yield, and other monochloropropenes have been treated as by-products with no utility value. In particular, cis- and trans-chloropropene have similar boiling points to allyl chloride, and their separation is extremely difficult, so efforts are being made to suppress their by-products, but the yield of allyl chloride is limited. In other words, the limit is about 50-60%.
The method of the present invention produces allyl chloride, cis and
Trans1-chloropropene is also effectively utilized as an active ingredient and the mixture thereof is simultaneously chlorinated to produce 1,3-dichloropropene, and the yield thereof is greatly improved. Among the isomers of monochloropropene, 2-chloropropene becomes 2,3-dichloropropene when chlorinated, so it needs to be separated before chlorination, but essentially it is 1,2-dichloropropene. It is desirable that the amount of by-products produced during thermal decomposition of dichloropropane is small. Therefore, one of the objects of the present invention is to improve the yield of monochloropropenes during thermal decomposition of 1,2-dichloropropane, and to improve the yield of 2-chloropropene among the monochloropropenes. The aim is to provide a solution to suppress by-products. According to the findings of the present inventors, in the thermal decomposition of 1,2-dichloropropane, the amount of 2-chloropropene produced is generally lower when the decomposition temperature is higher;
At higher temperatures, by-products such as benzene increase, and the allyl chloride produced decomposes, resulting in problems such as a decrease in yield and coking. As a result of various studies, the present inventors found that by thermally decomposing 1,2-dichloropropane at a temperature of 450 to 600°C and coexisting a small amount of 2-chloropropene in the reaction system, cis and trans1 - It has been found that the yield of chloropropene and allyl chloride can be increased, and at the same time, the by-product of 2-chloropropene, which is unnecessary for the purpose of the present invention, can be effectively suppressed. When the thermal decomposition temperature is below 450℃, the selectivity of monochloropropenes is good, but raw materials 1 and 2
- The overall yield is poor because the decomposition rate of dichloropropane is relatively low, and although the decomposition rate improves at temperatures above 600°C, it causes secondary decomposition of the product, which lowers the yield and reduces the benzene This produces hydrocarbon by-products such as coking, coking, etc. Therefore pyrolysis is 450
It must be carried out at a temperature in the range ~600°C, preferably 500-550°C. In addition, in the method of the present invention, a fraction containing 2-chloropropene is separated from the decomposition products, and this is recycled and added to the reactor. - Of the decomposition products of dichloropropane, cis and
There is almost no effect on the amount of trans1-chloropropene and allyl chloride produced, and only the amount of 2-chloropropene as a by-product is significantly reduced. In this case, 1 and 2 of the 2-chloropropene to be added cyclically.
- Weight ratio to dichloropropane is usually 2~
The intended purpose is achieved at about 15%. In addition, if 2-chloropropene gradually accumulates in the reaction system as a result of continuous operation for a long time, it is necessary to appropriately adjust the circulation amount and discharge the excess amount out of the system. In this reaction, the feed rate of the raw material 1,2-dichloropropane is usually 150 to 1000/・ as SV.
About hr is appropriate. The boiling point of the decomposition products thus obtained is 30 to 55°C.
Separate the components of cis and cis contained therein.
trans1-Chlorpropene and allyl chloride are fed as a mixture to a chlorination reactor and reacted with chlorine. The chlorination of monochloropropene is essentially the same as the chlorination of propylene, and is conventionally known; however, upon careful consideration, monochloropropene is slightly inferior in reactivity to chlorine and thermal stability compared to propylene. Isomers also differ in reactivity and thermal stability. For example, when 1-chloropropene and allyl chloride are chlorinated according to known methods, 1,3-dichloropropene is obtained as the main product in both cases, but at the same time, 3,3-dichloropropene is produced as a by-product. However, its amount reaches 10% of 1,3-dichloropropene. In addition to these substitution reactions, various reactions include the production of trichloropropane by addition reactions, the cutting of carbon by chlorination decomposition, coking and other higher chlorination reactions by carbonization reactions, and the production of high-boiling substances by polymerization reactions. In both cases, the proportion of products is not uniform because there are differences in reactivity due to differences in starting materials, and as a matter of course, the optimum reaction conditions also differ. By the way, according to the findings of the present inventors, when 1-chloropropene and allyl chloride are mixed and both are chlorinated at the same time, 3.3- It was observed that the by-product rate of dichloropropene decreased and the production rate of the target product, 1,3-dichloropropene, increased accordingly. In this case, the mixing ratio of cis and trans1-chloropropene and allyl chloride is 0.2:1 to 1:0.1 by weight, preferably 1:1.5 to 1:
Approximately 3.5 is appropriate. In addition, if the ratio of the mixture of these monochloropropene isomers to chlorine is too small, it may lead to the formation of higher-order chlorinated substituents and carbonization reaction, and if it is too large, the reaction rate of monochloropropene will be poor and no reaction will occur. The molar ratio is usually 3 to 10, preferably 4, since the amount of residue increases.
It is desirable to carry out the reaction in a state where the amount of monochloropropene is in excess of about 7 to 7. If the reaction temperature for chlorination is low, the by-products of 1,2,3- and 1,1,2-trichloropropane will increase, and if it is high, the carbonization reaction will become significant, so it is 450 to 560°C, preferably 480 to 520°C. It is carried out within the range of. In addition, in the high-temperature chlorination reaction of monochloropropene, as in the case of propylene, it is important to mix chlorine and the substance to be chlorinated quickly and uniformly. It is necessary to set it to 10cm/sec or more. An example of an embodiment of the method of the present invention is shown in the form of a flow sheet as shown in the drawings. That is,
The remaining 1,2-dichloropropane is mixed with the recycled by-product 2-chloropropene and the unreacted content of the above, vaporized in an evaporator, preheated as necessary, and then transferred to a pyrolysis reactor. It is supplied to A and thermally decomposed. The decomposition products are condensed in a condenser, uncondensed hydrochloric acid gas, etc. are separated, and then distilled in a distillation column B. A portion of the 2-chloropropene fraction separated in distillation column B is recycled and mixed with 1,2-dichloropropane to produce 2-chloropropene in the thermal decomposition reaction.
- It is used for suppressing chlorpropene by-products, and is partially discharged from the system as necessary. The remaining fraction is subsequently divided in distillation column C into a fraction with a boiling point of 30 to 55°C containing cis- and trans-chloropropene and allyl chloride, an unreacted 1,2-dichloropropane fraction, and a high-boiling fraction. . isolated boiling point
The fraction at 30~55°C is mixed with the unreacted fraction that is circulated further, vaporized and preheated in an evaporator, and then quickly mixed with chlorine in a mixer and reacted in chlorination reactor D. . In this case, since the reaction temperature is maintained by the heat generated by the reaction itself, the preheating temperature is set so that the predetermined temperature is reached and the adiabatic reaction is carried out. The product is condensed in a condenser, and uncondensed hydrochloric acid gas and the like are treated with water washing, alkali washing, etc. The liquid from which hydrochloric acid gas etc. have been separated is distilled in distillation column E, and the separated unreacted components are recycled to the chlorination reaction, and the fraction containing 1,3-dichloropropene is further distilled for further purification. etc. will be processed. Hereinafter, the method of the present invention will be described in more detail with reference to Examples, but these are merely representative examples, and it goes without saying that the present invention is not limited to these. There is no restriction in any way. Example 1 220 g/h of 1,2-dichloropropane and 14
After vaporizing 2-chloropropene at 1 g/h, the temperature was raised to 400°C in a preheater and then fed to a stainless steel reaction tube with an inner diameter of 28.4 mm and a length of 900 mm heated to 510°C in an electric furnace for pyrolysis. The resulting product was rapidly cooled, collected, and analyzed by gas chromatography, and the following results were obtained.

[Table] The reaction was carried out in the same manner as in Example 1 except that 2-chloropropene was not added. As a result, the selectivity of 1-chloropropene, 2-chloropropene and allyl chloride was 34.6% and 5.1%, respectively. , 56.3
It was %. Example 2 After vaporizing 191 g/h of 1-chloropropene and 191 g/h of allyl chloride, the temperature was raised to 370°C in a preheater and quickly mixed with 71 g/h of chlorine to form an inner diameter of 17.5
mm, fed into a stainless steel reaction tube with a length of 700 mm.
The reaction was carried out at a temperature of 490°C, and the resulting product was rapidly cooled, collected, and analyzed by gas chromatography, and the following results were obtained.

[Table] The values in parentheses indicate the results of a reaction carried out in the same manner as in Example 2, except that 1-chloropropene was not added and allyl chloride was used at 383 g/h.

[Brief explanation of the drawing]

The figure is a flow sheet showing a typical embodiment of the present invention, where A is a pyrolysis reactor, B, C, E,
F indicates a distillation column, D indicates a chlorination reactor, and solid lines and numbers indicate material flows.

Claims (1)

[Claims] 1. 1,2-Dichloropropane is thermally decomposed at 450 to 600℃, components with a boiling point of 30 to 55℃ are separated from the decomposition products, and a portion of the remaining 2-chloropropene fraction and unreacted The 1,2-dichloropropane fraction is recycled to the pyrolysis reactor, and the separated boiling point 30-55
A method for producing 1,3-dichloropropene, which comprises reacting a decomposition product at 450 to 560°C with chlorine.