CS232072B1 - Process for preparing vinyl chloride - Google Patents

Abstract

The invention relates to a process for the production of vinyl chloride by partial thermal dehydrochlorination of 1,2-dichloroethane, in which part of the 1,2-dichloroethane unreacted during dehydrochlorination is returned directly before dehydrochlorination.

Description

The invention relates to a process for the production of vinyl chloride by partial thermal dehydrochlorination of 1,2-dichloroethane.

Vinyl chloride (VCM) is an intermediate product for the production of one of the most widely used plastics - polyvinyl chloride (PVC). The most commonly used technology for the production of VCM is the thermal dehydrochlorination of 1,2-dichloroethane (EDC), which is preferably carried out only with partial conversion of EDC, for example from 50% of the theory. with EDC chlorination and ethylene oxychlorination · Unreacted EDO from thermal dehydrochlorination, so-called · returnable EDC, is further fed through a rectification column system (quench, hydrochloric, vinyl chloride column) that processes the reaction mixture from EDC cleavage to chlorination and / or separate chlorination reactor, from which, together with the EDC produced by the chlorination of ethylene, it is discharged to the water scrubber system, where the EDC is simultaneously fed from the oxichlorination stage. The combined EDC streams are then processed in another rectification column system (e.g. light column, heavy column, tar evaporator, recovery column). The EDC thus purified is then passed to the dehydrochlorination stage.

The process has a number of disadvantages. The unreacted EDC from the dehydrochlorination stage is passed in large quantities through several other devices (such as a hydrochloric and vinyl chloride column, a direct and / or separate distillation reactor, water scrubbers and series.

232 072 EDO rectification columns). This reduces the capacity of these devices. The above-described recirculation EDO circulation further increases the energy consumption of VCM production.

The aforementioned disadvantages are overcome by the process for the production of vinyl chloride according to the invention, which consists in removing a part of the liquid medium from a tray of a quench column, preferably from an intermediate tray or tray above the environment, thereby obtaining a product of such quality Directly returning before the cleavage reactor · The amount of EDO unreacted in the cleavage reactor can be varied within a wide range, based on the total amount of EDO unreacted in the cleavage stage. However, some unreacted EDO has to be treated as previously used, ie. apparatus to prevent the concentration of unwanted by-products from rising. It is advantageous to treat about 50% of the unreacted EDO in the fission reactor by the process according to the invention.

The process according to the invention releases part of the capacity of the oil of a number of the following devices, but above all the energy consumption of VCM production is significantly reduced.

In the accompanying diagrams, block diagrams of the production of VCM are shown in FIG. 1, a method of manufacture known so far and in FIG. 2, a method of production according to the invention.

232 072

The following examples illustrate but do not limit the scope of the invention.

Example 1

42 t / h EDO was fed into the cleavage reactor. The degree of dehydrochlorination of EDO to VCM is about 50% of theory. The resulting reaction mixture is fed to the quench column after mixing with liquid EDO from the quench column (thereby partially cooling it). Lateral withdrawal of 5 t / h of liquid medium from the sixth floor, calculated from the bottom for a total of ten trays in a quench column, yields a product of up to 1.5% by weight. % HCl, up to 4.5 wt. VCM and the rest EDO. This product can be returned directly in front of the cleavage reactor.

This achieves VCM steam savings of 2.954 GJ / h.

Example 2

Procedure as in Example 1 except that 48 t / h EDC is fed into the fission reactor and 12 t / h of liquid medium is withdrawn from the sixth floor via the side flue and returned directly in front of the fission reactor. VCM production at 5.18 GJ / h.

Claims (1)

A process for the production of vinyl chloride by partial thermal dehydrochlorination of 1,2-dichloroethane, characterized in that a portion of 1,2-dichloroethane not reacted during dehydrochlorination, preferably 50%, with a lateral withdrawal from a queaoh column, preferably from the middle or above the middle , directly to the dehydrochlorination reactor.