JPS598244B2 - Dehydrochlorination treatment method for 1,2-dichloroethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of vinyl chloride, and in particular to a new process for producing vinyl chloride by dehydrochlorinating 1,2-dichloroethane.

A method for producing vinyl chloride by dehydrochlorinating 1,2-dichloroethane using a salt in a molten state is known.

This method optionally includes the corresponding oxychloride;
1,2-dichloroethane is dehydrochlorinated with high conversion and higher selectivity by direct contact with a melt containing polyvalent metal chlorides in high and low valence states. It has recently been discovered that when the melt contains oxychloride, the selectivity towards vinyl chloride is lower than when it does not. Also, in many cases
1,2-dichloroethane as a raw material is covered by British Patent No. 12.
It is recovered from the chlorinated effluent produced during the entire process of vinyl chloride production as described in US Pat. No. 13,202. The recovered 1,2-dichloroethane may contain unsaturated chlorinated hydrocarbons, such as trichlorethylene, which act as inhibitors of the dehydrochlorination process;
May reduce selectivity to vinyl chloride.
In the present invention, 1.2
- When dehydrochlorinating dichloroethane, the contacting is carried out in the presence of ethane to increase the overall selectivity to vinyl chloride.

The amount of ethane present is such that the weight ratio of ethane to 1.2-dichloroethane is 0.01:1 to 0.15:1, preferably 0.01:1 to 0.15:1.
0.015:1 to 0.10:1.

If the amount of ethane used is lower than the above ratio, the selectivity to vinyl chloride cannot be increased as expected, and conversely, if the amount of ethane used is higher than the above ratio, neither the vinyl chloride selectivity nor the 1,2-dichloroethane conversion rate will increase. This results in a decrease in one or both. Although the present invention is not bound by theory, it is believed that the addition of ethane suppresses chlorine substitution of dichloroethane, which results in increased vinyl chloride selectivity. Ethane conversion also acts to suppress the increase in cupric chloride concentration that occurs in the dehydrochlorination reaction zone from the interaction between oxychloride present in the melt and hydrogen chloride released in the dehydrochlorination reaction. It is thought that this also serves the purpose of The melt used for dehydrochlorination treatment includes polyvalent metals, i.e.
For example, there are chlorides of metals with multiple positive valence states, such as magnesium, iron, copper, cobalt, chromium, and high and low valence forms of polyvalent metals, preferably copper.

In the case of molten polyvalent metal chlorides with high valences, such as copper chloride, for example, the chlorination of monovalent metals with only one positive valence state is non-volatile and is not susceptible to the action of oxygen under process conditions. Addition of a metal salt melting point depressant, such as a metal salt melting point depressant, to a polyvalent metal chloride forms a molten salt mixture with a reduced melting point. As the monovalent metal chloride, for example, potassium chloride and lithium chloride are particularly preferable, but for example, zinc, silver,
Chlorides and mixtures thereof of heavy metals heavier than copper belonging to the first and third groups of the periodic table, such as thallium, can also be used.

The metal chloride melting point depressant is added in an amount necessary to maintain the molten salt mixture at the reaction temperature, but generally reduces the melting point of the molten salt mixture to 260°C (500'F).
Add only the amount necessary to achieve the following temperature. In the case of salt mixtures consisting of copper chloride and potassium chloride, the composition of the melt is between 20 and 40% by weight, preferably 30% potassium chloride and the remainder copper chloride. However, if the catalyst remains molten throughout the entire process, the melting point of the molten catalyst will be 2.
In some cases, temperatures above 60°C (500'F) may be sufficient. Also,
The melt may also contain mixtures of polyvalent metal chlorides or other promoters. Additionally, the metal chloride can optionally be maintained in a molten state without the use of melting point depressants. In a preferred embodiment, the molten salt used for dehydrochlorination also includes a polyvalent metal oxychloride;
In this case, the oxychloride reacts with hydrogen chloride released during the dehydrochlorination process, and if copper oxychloride is used as a typical oxychloride, the following formula is obtained.

This reduces the amount of hydrogen chloride in the effluent (the effluent contains an equilibrium amount of hydrogen chloride).

) The oxychloride is preferably present in an amount that will react with substantially all of the hydrogen chloride produced during the dehydrochlorination process. Part or all of the ethane present during the dehydrochlorination reaction is chlorinated by the chlorination ability of the molten salt to become chlorinated hydrocarbons (vinyl chloride, ethyl chloride, dichloroethane, etc.).

Dehydrochlorination treatment is generally carried out at temperatures between 371°C and 649°C (7
00'F to 1200'F), preferably 399°C to 538°C (750'F to 1000'F) and pressures of 1 to 20 atmospheres; F) is fine.

The contact between the raw material and the melt is generally carried out countercurrently to each other,
Preferably, the process is carried out with the feedstock in a continuous vapor phase and with a residence time of 1 to 60 seconds, although longer residence times may be used. The dehydrochlorination treatment of the present invention is preferably utilized as part of the overall process for producing vinyl chloride from either or both of ethane and ethylene using molten salts.

Specifically, one or both of ethane and ethylene is brought into contact with a melt containing a polyvalent metal chloride in a high valence state and a low valence state, and preferably a metal oxychloride is added to the molten salt mixture. and also contact with either or both of hydrogen chloride and chlorine,
This produces an effluent containing vinyl chloride and 1,2-dichloroethane. The vinyl chloride is recovered as a product, but the 1,2-dichloroethane is recovered as a molten salt containing metal chlorides in high and low valence states, and preferably polyvalent metal oxychlorides, and the presence of said ethane. Direct contact below yields a dehydrochlorination effluent containing vinyl chloride. In a preferred embodiment of the invention, a molten salt mixture containing copper chloride and a melting point depressant (preferably 20 to 40% by weight of the melt is potassium chloride as the melting point depressant and the remainder is copper chloride). Copper oxychloride is produced by contacting with molecular oxygen in one reaction zone.

A cupric chloride content in the melt of at least 16%, generally 18 to 50% by weight of the melt is sufficient to provide the cupric chloride necessary for subsequent chlorination and dehydrochlorination reactions. . However, the amount of cupric chloride may be lower if the circulation rate and residence time of the salt is increased. Despite the various reactions that occur during the chlorination and dehydrochlorination steps, the cupric chloride content in the melt changes little. Molecular oxygen is 0.5 to 5.5% by weight, preferably 1 to 3%.
It is desirable to introduce in an amount and rate sufficient to provide a molten salt mixture containing % copper oxychloride. Although small amounts of chlorine and/or hydrogen chloride may be introduced into the first reaction zone, in this preferred embodiment the majority of the chlorine and/or hydrogen chloride is added to the chlorination zone. At this stage the molten salt mixture containing copper oxychloride is recycled to a second reaction zone (chlorination zone) where the molten salt is recycled unconverted ethane (if used as feedstock), recycled ethyl chloride and In addition to unreacted ethylene or ethylene as a reaction intermediate, contact is made with fresh raw materials of ethane and/or ethylene, preferably ethane, and chlorine and/or hydrogen chloride. The recycle may also include 1,1-dichloroethane and/or dichloroethylene. The effluent from the second reaction zone is vinyl chloride,
It includes any one or more of 1,2-dichloroethane, ethyl chloride, ethane, ethylene, and heavy chlorinated hydrocarbons, such as trichloroethylene, tetrachloroethylene, trichloroethane, and tetrachloroethane. The effluent also contains water vapor and an equilibrium amount of hydrogen chloride. The reaction effluent is passed through a separation and recovery zone to recover the various components. Ethyl chloride, ethane and ethylene are recovered for eventual conversion to vinyl chloride. Recovered 1 and 2
- Dichloroethane is introduced into the dehydrochlorination zone (third reaction zone), where in the presence of ethane the molten salt from the first zone (where the salt contains oxychloride) or the molten salt from the second zone or both zones Vinyl chloride is obtained by dehydrochlorinating 1,2-dichloroethane by contacting it with a salt. The chlorination ability of the molten salt converts all or a portion of the ethane to chlorinated products as described in connection with the second reaction zone. The effluent from the dehydrochlorination reaction zone is introduced into a separation and recovery zone to recover the vinyl chloride reaction product and other components, which are ultimately utilized in vinyl chloride production. The ethane utilized in the dehydrochlorination reaction zone may be fresh feed, recycled ethane recovered from the chlorination (second reaction zone) effluent, or a combination thereof.

As long as ethane is used in the dehydrochlorination reaction as described above,
The source of ethane is not critical to the invention. Chlorination in the presence of a melt (second reaction zone) may be carried out under the conditions described above in connection with the dehydrochlorination treatment in the presence of a molten salt.

Oxychloride formation generally occurs between 316°C and 482°C.
(600'F to 900'F), although higher temperatures may be used. The preferred temperature for oxychloride formation is 399°C to 466°C (750'F to 87°C).
0'F). A process for producing vinyl chloride from either or both of ethane and ethylene using a molten salt, including dehydrochlorination of 1,2-dichloroethane using a molten salt, is comprehensively described in British Patent No. 1,213,202. There is.

The present invention is an improvement on this production method, and aims to increase the vinyl chloride selectivity by using ethane in the dehydrochlorination region as described above. Although the present invention is particularly suitable for situations where oxychloride is present in the melt utilized in the dehydrochlorination reaction zone, it can also be applied in the absence of oxychloride, in which case the dehydrochlorination The 1,2-dichloroethane fed to the reaction zone may contain a dehydrochlorination inhibiting substance, such as trichlorethylene. The addition of ethane to the dehydrochlorination reaction zone minimizes the adverse effects on vinyl chloride selectivity due to the presence of dehydrochlorination inhibitors, as discussed above. Hereinafter, the present invention will be explained with reference to examples.

Example 1 A molten salt consisting of 17.1% cupric chloride, 51.8% cuprous chloride, 0.2% copper oxychloride and 30.9% potassium chloride by weight was heated at 454°C ( Countercurrent contact is made with a feed consisting of a 90.6 mole percent 1,2-dichloroethane mixture and 9.4 mole percent ethane at a temperature of 849'F) and a residence time of 8.7 seconds.

The composition of the 1,2-dichloroethane mixture is as follows.

Despite the presence of oxychloride in the melt and the use of raw materials with high trichlorethylene content, unexpectedly the dehydrochlorination reaction was not inhibited and the vinyl chloride selectivity was 90.4 mol%. , the 1,2-dichloroethane conversion rate was 80%.

Example A molten salt consisting of 16.5% cupric chloride, 52.6% cuprous chloride, 0.2% copper oxychloride and 30.7% potassium chloride by weight was heated at 454°C (850°C). 'F) and a residence time of 7 seconds in countercurrent contact with the feedstock of Example 1 consisting of 84.5 mol % 1,2-dichloroethane and 15.5 mol % ethane.

The vinyl chloride selectivity was 91.8 mol%, and the 1,2-dichloroethane conversion rate was 79.7 mol%. Maintaining vinyl chloride selectivity at least about 80% despite the presence of oxychloride in the melt and/or dehydrochlorination inhibitors such as trichlorethylene in the 1,2-dichloroethane mixture while (generally 9
The great advantage of the present invention is that vinyl chloride can be obtained by dehydrochlorinating 1,2-didaloloethane at a conversion rate of 70% or more (which can achieve a selectivity of 0% or more).

Embodiments of the present invention are shown below.

(a) In the first reaction zone, ethane, ethylene or mixtures thereof are converted to chlorine, hydrogen or mixtures thereof, high valent chlorides of polyvalent metals, low valent chlorides of polyvalent metals and producing an effluent containing vinyl chloride and 1,2-dichloroethane by contacting with oxychloride; recovering vinyl chloride and 1,2-dichloroethane from the effluent; and recovering the recovered 1,2-dichloroethane. - The manufacturing method according to the claims, further comprising using dichloroethane for dehydrochlorination treatment.

Claims (1)

[Claims] 1 A process for obtaining vinyl chloride by dehydrochlorinating 1,2-dichloroethane by direct contact with a molten salt containing polyvalent metal chlorides in high and low valence states, which 1,2-dichloroethane, characterized in that the dehydrochlorination treatment is carried out in the presence of ethane in an amount selected such that the weight ratio with 1,2-dichloroethane is 0.01:1 to 0.15:1. dehydrochlorination treatment method.