CS209958B1 - Method of processing the reaction mixtures containing the dichloetan,vinychloride and hydrogen chloride - Google Patents

Abstract

Process for treating the reaction mixture containing dichloroethane, vinyl chloride a hydrogen chloride (EDC-VCM-HCl) finds use in the chemical industry in the production of VCM (vinyl chloride). Resolves the removal method hydrogen chloride from a ternary mixture of EDC-VCM-HCl, processing it into hydrochloric acid and subsequent use of separated vinyl chloride. This procedure is primarily designed for cases of low-temperature sweating cooling the rectification column because allows the production of vinyl chloride, even long-term, even when the cooling stage goes out

Description

The present invention relates to a process for removing hydrogen chloride from a reaction mixture containing hydrogen chloride, wooll chloride and 1,2-dichloroethane and treating it and then utilizing separate vinyl chloride.

The major part of vinyl chloride (VCM) worldwide is produced by thermal cleavage of 1,2-dichloroethane (EDC) according to the reaction scheme t - 500 ° C

C ₂ H ₄ C1 - ► C ₂ ^H 3 ^C1 * ^{H 01}

The resulting hydrogen chloride (HCI) is usually removed from the ternary HCl-VCM-EDC mixture in rectification columns at high pressures at temperatures of about 293 K, optionally at medium pressures (up to 1 MPa) and low temperature cooling (about 233 K).

The basic condition for further treatment of HCl is its purity (the impurity content must be of the order of 0.1% by weight). The bulk of the HCl thus obtained is reused in the production of either EDC for the oxychlorination of ethylene or a portion of the VCM for the hydrochlorination of acetylene. In the event of a failure of the oxichlorination stage, some manufacturers carry out the absorption of pure HCl to hydrochloric acid as an emergency measure. However, this method only involved treatment of pure HCl in the event of the oxichlorination step. However, it does not address the issue of low-temperature cooling failure, which results not only in shutting down the ethylene oxychlorination but also in shutting down the whole plant, since it is not possible to process the HCl resulting from EDC cleavage for high VCM content.

The above-mentioned disadvantages eliminate the process according to the invention, i.e. the process for the treatment of the HCl-EDC-VCM reaction mixture resulting from the production of VCM. The essence of the method is that the gas mixture leaving the top of the rectification column 4 is cooled to the additional condenser. 6, wherein about 60% by weight of VCM and about 15% by weight of HCl condenses, wherein the liquid mixture is used as reflux for rectification column 4 and HCl gas containing VCM up to 20% by weight is treated by adiabatic absorption to hydrochloric acid. Further, in the normal operation of the low-temperature cooling of the rectification column 4, it is possible to branch off about 30% by weight of the gaseous mixture before entering this column and lead directly to the additional condenser. This releases accordingly! capacity of low-temperature rectification column and subsequent equipment for eventual intensification of production. The VCM gas leaving the adiabatic absorption 3, after condensation of water 8 and neutralization, is treated together with the VCM off-gases from the production of polyvinyl chloride (PVC); or liquefied (at a temperature of about 257 K and a pressure of 0.7 MPa).

The main benefit of the proposed poetup is that, unlike earlier procedures, it allows to operate VCM production (even in the long term) in the event of low-temperature cooling failure; the production losses due to the failure of the cooling stage are considerable. This process does not impose any particular requirements on the purity of the treated HCl. In addition, separating a portion of the gaseous stream prior to entering the rectification column will allow the processing of larger amounts of EDC cracking fission gases, i.e., producing larger quantities of VCM without the intensification of the purification section. In subsequent PVC production, the VCM obtained after adiabatic absorption of HCl can be led directly to PVC production.

209 9S8

The attached drawing is a flow chart of the process of the invention. From chlorine and ethylene we draw a direct chlorination of 1D EDO, which after purification 2 is subjected to cracking 3. From this resulting mixture of HCl-VCM-E0C, the rectification column 4 separates the EOC and partly also the VCM which lead longer to purification 5. a portion of the VCM is recovered from the remaining mixture by condensation S and the hydrogen chloride gas 8 containing up to 20% by weight of the VCM is treated by adiabatic absorption 7 to formic acid. To process a higher amount of fission products (increase VCM production), the gaseous mixture reads before entering the rectification column 4 and passes directly to the additional condenser 6. The VCM gas obtained is neutralized after condensation water 7 and then aa is processed in PVC production. The essence of the invention is illustrated by the following non-limiting examples.

Example 1

The current method of separating HCl from VCM and EOC is carried out on a rectification column which has 69 trays. Part of the column is a low-temperature exchanger built-in above the last level of the column,

Condensed HCl (at 236 K) is removed from the bottom of the exchanger and returned to the 69th floor as reflux. The bottom temperature of the column at the inlet of the feather to the digester is maintained at about 373 K. The binary EOC-VCM is withdrawn from the bottom of the column for further processing in a production column, 1 (0 is VCM from EOC). The process for the subsequent treatment of the HCl oxichloroacetylene to the EOC raises the need for a perfect separation of HP1 pd VCM and SDC, requiring high cooling low temperature equipment performance.

Example 2

Rectlflkčll plpl without, low-temperature cooling. The temperature at the top of the rectification column 4 will be shifted towards higher temperatures (255-288 K). At these temperatures and under the existing pressure (0.89 MPa), the EOC, VCM, and the same HCl will condense. From the top of the rectification column 4, an HCV-VCM emission containing traces of EOC is passed. This mixture leads to an additional condenser 6. Here, at a temperature of about 253 kPa and a pressure of 0.88 MPa, all the EOC, about 60% by weight of VCM and even 15% by weight of HCl condenses. The additional capacitor 6 has a dual purpose. On the one hand, it attracts the liquid emulsion, which is then used as the reflux for the rectification column, and at the same time, it depends on the organic phase in the VCM-HCl gas mixture leading to adlabat absorption 7. Reducing the VCM concentration (below 20%) the amounts of organic adequately produced hydrochloric acid, without further processing or using a combination of two and a tower. The waste gases from adiabetic absorption 7 will contain VCM and traces of inert gases (such as C ₂ H ₄ , N _? ) After condensation of the water 8 After neutralization e.g. approx. 267 K and printing 0,7 MPa) ·

Example 3

It is based on running at low temperature low-temperature rectifier column cooling. Before entering this column 4, it separates cos 30% by weight of a ternary gas mixture of 34% by weight of VCM, 66% by weight of HCl by 1% by weight of EOC and leads to the additional condenser 6. Whether the organic fractions have been condensed

The liquid liquor from the condenser 6 is used as a feed into the rectification ions. The gaseous solution is treated by adiabatic absorption 7 to hydrochloric acid. The adiabatic absorption gases are treated as in Example 2.

Claims (2)

1. A process for treating a reaction mixture containing dichloroethane, vinyl chloride and hydrogen chloride is formed. in the production of vinyl chloride, characterized in that the gaseous mixture leaving the top of the rectification column (4) without low-temperature cooling is fed to an additional condenser (6) where at a pressure of 0.9 to 10 bar and a temperature of 253 to 293 K condenses 2-dichloroethane, 40 to 70% by weight of vinyl chloride and 10 to 30% by weight of hydrogen chloride, the liquid mixture from the condenser (6) being used as a reflpx for the rectification column (4), gaseous hydrogen chloride containing up to 20% by weight of vinyl chloride adiabatic absorption (7) to hydrochloric acid and gaseous effluent resulting from adiabatic absorption (7), after condensation of water (8) and neutralization, is treated epolithically with the vinyl chloride off-gases of polyvinyl chloride production or liquefied. 2. A method according to claim 1, characterized in that 10 to 40% by weight of the gaseous mixture is separated off before entering the rectification column (4) by low temperature cooling. and leads directly to the auxiliary capacitor (6).