JPS58110528A - Preparation of vinyl chloride - Google Patents

Abstract

PURPOSE:To prepare vinyl chloride with suppressing the formation of chloroprene and aceylene as by-products without damaging a thermal decomposition reaction, by decomposing thermally 1,2-dichloroethane in the presence of hydrogen. CONSTITUTION:In decomposing thermally 1, 2-dichloroethane, the thermal decomposition is carried out in the presence of 0.05-3.0 moles, preferably 0.2-1.0 hydrogen. Even if small amounts of carbon tetrachloride or trichloroethylene, and impurities existing in industrially used 1,2-dichloroethane are present in 1,2- dichloroethane, these impurities have hardly influence on it. When selective hydrogenation of acetylene in hydrogen chloride using a Pd catalyst is carried out after this method to convert acetylene to ethylene selectively, the formation as a by-product and accumulation of trichloroethylene can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing vinyl chloride by thermally decomposing l.2-dichloroethane.

The method of producing vinyl chloride by thermally decomposing 1,2-dichloroethane is known, and the industrial cRJ K is usually 400 to 5.
Reaction conditions of 50°C and 4 to 30 atm were adopted, l.2
- The plant is operated at a dichloroethane decomposition rate of 50-60%. The decomposition rate is 6oq7. In the above cases, coke accumulates in the reaction tube and the operation has to be stopped, and by-products such as chlorobrene, acetylene, other chlorinated hydrocarbons, tar, and carbon increase, reducing the yield of vinyl chloride. descend.

However, as generally adopted, the decomposition rate is 50 to 6.
Even if it is maintained at 0%, by-products mainly consisting of chlorobrene and acetylene are usually produced at 1000''a000ppm each.Industrially, after the thermal decomposition products are rapidly cooled, they are processed in the 10th) J distillation column. It is usual to separate hydrogen chloride and then separate vinyl chloride and unreacted 1.2 dichloroethane in a second distillation column.

Here, the by-product acetylene is not separated from hydrogen chloride, and the hydrogen chloride containing acetylene is directly supplied to the next oxychlorination step, where it is reacted with ethylene and oxygen (or air), and is then reacted with l.2-dichloroethane. is collected. At this time, acetylene and ethylene are oxychlorinated and converted into dichloroethylene, trichlorethylene, tetrachlorethylene and other chlorinated hydrocarbons, resulting in wasteful consumption of hydrogen chloride. In addition, the trichlorethylene produced in the oxychlorination process is 1.2. -Since it is difficult to separate from dichloroethane, it is supplied as is to the thermal decomposition process, but it exhibits the effect of suppressing the thermal decomposition rate.

For this purpose, a method for removing trichlorethylene by chlorination has been studied and is also being implemented industrially, but it wastes Ce2 and is uneconomical. A method is also known in which hydrogen chloride containing acetylene is supplied to the oxychlorination process by adding 137i VC hydrogen to selectively convert it to ethylene in the presence of a baladicum catalyst, thereby preventing the formation of trichlorethylene in the oxychlorination process. It has been developed and is being implemented industrially.

However, in general, the selectivity to ethylene is not said to be sufficiently high, and the problem of catalyst life is presumed to be of little concern from an economic point of view.

On the other hand, chlorobrene is extracted as a bottom liquid from the second distillation column along with unreacted 1,2-dichloroethane, but since chlorobrene is concentrated in the distillation column, it polymerizes and blocks the distillation column, causing the operation to be interrupted. There are often cases where it is necessary. 1.2-dichloroethane containing chlorobrene is chlorinated to convert it into a high-boiling substance and then separated by distillation, or purified by a method of removing chlorobrene by distillation, and then supplied to the thermal decomposition process again. In this case, chlorine is consumed, and the distillation separation method is uneconomical because chloroprene must be diluted to a concentration lower than that at which it starts polymerization.

As mentioned above, in the conventional method, it is not possible to avoid by-products of acetylene and chlorobrene during the thermal decomposition of 1,2-dichloroethane, which deteriorates the yield of vinyl chloride, making it impossible to continue the operation stably over a long period of time. This results in disadvantages such as:

In research on catalytic cracking of 1,2-dichloroethane using a catalyst, for example, 1,2-dichloroethane was cracked at 350 to 400°C using a fluorine-treated platinum-alumina catalyst.
A method of catalytic cracking [Khim, Prom, 48 (
10) 741 ('72)), it is known that when sil/2.1 mol of hydrogen is added per 21 mol of l.2-dichloroela, acetylene and coke produced as by-products decrease and ethylene increases.

This method gives one /I ``jl?'' for the production of acetylene, but 4m = ``jl?'' for chloroprene.
Not covered. Furthermore, it is not clear whether a similar phenomenon occurs in a thermal decomposition reaction at a reaction temperature of 400 to 550° C., which does not use a catalyst, as in the method of the present invention.

In order to overcome the shortcomings of the conventional method, et al. conducted intensive research and discovered a method for suppressing the by-products of chlorobrene and acetylene without inhibiting the thermal decomposition reaction of 1,2-dichloroethane. He came up with an invention.

Misfire J describes a method for producing vinyl chloride, which is characterized by thermally decomposing 1,2-dichloroethane in the presence of hydrogen when producing vinyl chloride by thermally decomposing 1,2-dichloroethane. .

In the unexploded method, the amount of hydrogen added is 1.2-
0.05 to 3.0-II per 100 moles of dichloroethane
-/1dj74L< is 0.2 to 1.0 mol. If the amount of hydrogen added is small, the effect of suppressing chlorobrene and acetylene will be small, and if the amount of hydrogen added is large, 1.2-
Suppresses the thermal decomposition rate of dichloroethane.

Further, since unreacted hydrogen is supplied to the oxychlorination step together with hydrogen chloride, it is not preferable to add a large amount of hydrogen from the viewpoint of safety in the oxychlorination step. Even if 160 moles or more of hydrogen is added per 100 moles of 1.2-dichloroethane, the effect of suppressing chlorobrene and acetylene remains unchanged. Therefore, p0.2-cycloethane per 100 moles.
Preferably, 2 to 1.0 moles of hydrogen are added.

As hydrogen, hydrogen obtained by electrolysis of sodium chloride can be used as is, but hydrogen obtained from other sources may also be used, and there is no particular restriction for the purposes of the present invention.

Furthermore, the method of the present invention can be applied as is when a small amount of carbon tetrachloride or trichlorethylene or other impurities in industrially used 1,2-dichloroethane are present in 1,2-dichloroethane. The influence of these impurities is not particularly noticeable.

The decomposition rate of 1,2-dichloroethane will not be particularly affected by the addition of hydrogen if the hydrogen M&amp; The conditions were adopted and the reaction temperature was 400℃.
~550°C can be adopted.

Industrially, it is operated under 4 to 30 atmospheres as in the conventional method.
- The decomposition rate of dichloroethane can be maintained at 50 to 60%, and there is no need to install new equipment other than adding hydrogen addition equipment.

A known method is to add carbon tetrachloride as a thermal decomposition accelerator in order to increase the decomposition rate of l,2-dichloroethane to a level higher than that of conventional methods or to lower the thermal decomposition temperature. Even if there is no production, there is no problem in applying the moon method as is, and by adding hydrogen, the amount of by-products of cyclourethane and acetylene can be suppressed.

As shown in the examples by the method of the invention, for example l.2
- When the decomposition rate of dichloroethane is 58%, acetylene is reduced by 100 to 200 pp compared to the conventional method in a reaction at normal pressure.
500 to 12 o of mioroprene.

ppm can be reduced. Particularly effective in suppressing the amount of chloroprene by-product (25% to 45% compared to conventional methods)
can be reduced. These effects can also be obtained under industrial operating conditions.

In addition, even in the method of the present invention, the effect of suppressing by-product acetylene is not sufficient, and the formation of trichlorethylene in the oxychlorination step due to acetylene cannot be avoided. However, after implementing the method of the present invention, a selective hydrogenation method for acetylene in chlorinated seafood using a palladium catalyst is applied to selectively convert acetylene to ethylene, thereby preventing the by-product and accumulation of trichlorethylene. be able to. In this case, there is no need to newly supply hydrogen to the selective hydrogenation equipment from the outside, and since most of the hydrogen used in the method of the present invention remains, hydrogen and hydrogen chloride containing acetylene can be directly supplied. Alternatively, it is sufficient to supply hydrogen to a jKQ adding facility.

Hereinafter, 1 will be explained based on an example.

Example 1 A stainless steel tube with an inner diameter of 167 mm and a thermometer protection tube with an outer diameter of 6 mm inside was used as a reaction tube, and heated from the outside in a tubular electric furnace with a length of 60 cm to a predetermined temperature. The reaction was carried out while maintaining the temperature at 6 degrees. 1t per hour - Luno f? t%
1.2-Dichloroethane, 0.25 moles of nitrogen and a predetermined amount of hydrogen were fed into the reaction tube through a 1.2-dichloroethane vaporizer. After cooling the reaction tube 11 gas and washing it with water, the produced gas and produced liquid were analyzed by gas chromatography.

Table 1 shows the results of the reaction by varying the amount of hydrogen added to l.2-diq-1'J-ruethane. Since the filtration temperature (Hi) was generated in the axial direction of the reaction tube, Table-IK shows the effective V vorticity ([av)] as the reaction temperature.The effective average temperature is based on the activation energy of 28 Kcal/mol! Determined by the method of Nobuo Otake, Reactor Design J (1956, Science and Technology).

1,2-dichloroethane (hereinafter referred to as EDC, !: i'+)
The decomposition rate and selectivity of by-products were determined using the following formula.

RUN NOs. 101 to 104 are control examples in which no hydrogen is added.

Practical Example 2 The same procedure as in Example 1 was carried out except that 1,2-dichloroethane containing 2400 ppm of carbon tetrachloride was used.

The results are shown in Table-2.

Table-2 High strength example 3 Trichlorethylene 400ppm, carbon tetrachloride 900ppm
Example 1 was carried out in the same manner as in Example 1 except that 1,2-dichloroethane (industrial product) containing ppm was used. The results are shown in Figure 3.

Table-3 In all cases of Examples 1 to 3, l for the effective 1F average temperature
・The decomposition rate of 2-dichloroethane is shown in 151. If the amount of hydrogen added is appropriately adjusted as described above, it is 151.
- It can be seen that the decomposition rate of 2-dichloroethane is not suppressed (Figure = 1). Further, if the selectivity of by-products is plotted against the decomposition rate of 1,2-dichloroethane, it can be seen that taloropreaction and acetylene are reduced by adding hydrogen. Examples are shown in Figures 2 and 3.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the decomposition rate of 1,2-dichloroethane and the effective average temperature. [-2,3 is a graph showing the relationship between taloloprene and acetylene selectivity with respect to l.2-dichloroethane decomposition rate. i, '7.7'F Applicant Kanebuchi Kagaku Kogyo Co., Ltd. Agent Makoto Asano - One-shot procedure amendment (1) (4) 1981 Patent Application No. 212789 3, Person making the amendment Case and relationship Patent applicant
36) 8. Contents of the amendment Page 3, line 11 r of the Tonto Specification of Separate t% (JzJ changed to "chlorine", and the 5th line from the bottom of the same page changed "It has been implemented." [It has been implemented. However, ``General'', respectively. Delete ``However, general'' in the 4th line from the bottom of the same page. Change ``Chlorinated'' to ``Chlorinated chloroprene'' in the 5th line of the same page to 1100-2201 of the 4th line of the same page. )I)m rioapuL/
7" to 1-100~2201)I)m, ri00plane", and 6 lines from the bottom of page 9, "Temperature in the axial direction" to "Temperature in the axial direction", respectively. In Table 1 on page 11, the following has been amended. (8) In Table 1, the numerical value of the amount of addition of 2 in Example 110 [0,27J is corrected to [2,27J]. (9) In Table 3 on page 14, the following has been amended. that's all

Claims (4)

[Claims] (1) A method for producing vinyl chloride, which comprises thermally decomposing 1,2-dichloroethane in the presence of hydrogen. (2) 1.2-': The method according to claim 1, wherein the thermal decomposition is carried out by adding 0.05 to 3.0 moles of hydrogen per 100 moles of chloroethane. (3) The method according to claim 1, wherein the thermal decomposition is carried out by adding 0.2 to 1.0 moles of hydrogen per 2100 moles of 1,2-dichloroela. (4) The method according to claim 1, which uses 1,2-dichloroethane containing carbon tetrachloride.