Chlorine vinyl chloride monomer process

At least two catalytic processes have been used to purify halogenated streams. Both utilize fluidized beds of probably noimoble metal catalyst particles. One has been estimated to oxidize >9000 t/yr of chlorinated wastes from a vinyl chloride monomer plant (45). Several companies have commercialized catalysts which are reported to resist deactivation from a wider range of halogens. These newer catalysts may allow the required operating temperatures to be reduced, and stiU convert over 95% of the halocarbon, such as trichlorethylene, from an exhaust stream. Conversions of C-1 chlorocarbons utilizing an Englehardt HDC catalyst are shown in Figure 8. For this system, as the number of chlorine atoms increases, the temperatures required for destmction decreases. 

Recycling of plastic materials becomes more important, but it is not possible to make materials of the same quality as virgin materials. For PVC this problem is even more pronounced than for other plastics. For this reason, a process was studied which is able to destroy the waste PVC but which can recover its most important component, chlorine, as a raw material for vinyl chloride monomer manufacture with a very high yield. Most of the energy contained in the PVC can be recovered as electrical power and steam. 4 refs. 

On November 8, 2000, U.S. EPA listed as hazardous two wastes generated by the chlorinated aliphatics industry.18 The two wastes are wastewater treatment sludges from the production of ethylene dichloride or vinyl chloride monomer (EDC/VCM), and wastewater treatment sludges from the production of vinyl chloride monomer using mercuric chloride catalyst in an acetylene-based process. 

This process is shown schematically in Figure 7. The ethylene part of the feed reacts with chlorine in the liquid phase to produce 1,2-di-chloroethane (EDC) by a simple addition reaction, in the presence of a ferric chloride catalyst (9). Thermal dehydrochlorination, or cracking, of the intermediate EDC then produces the vinyl chloride monomer and by-product HC1 (1). Acetylene is still needed as the other part of the over-all feed, to react with this by-product HC1 and produce VCM as in the all-acetylene route. 

Application A process to produce vinyl chloride monomer (VCM) and ethylene dichloride (EDC) from ethylene, chlorine and oxygen using a high efficiency fixed-bed oxychlorination process. 

Mitsui Chemicals, Inc. Vinyl chloride monomer Chlorine, ethylene, oxygen Oxygen-based balanced oxychlorination process, high temp, direct chlorination process 23 1998... 

Ethylene dichloride (EDC) is used to manufacture vinyl chloride monomer (VCM), which is one of the largest commodity chemicals produced in the world. EDC may be produced by the direct chlorination of ethylene or oxychlorination of ethylene in the presence of oxygen and hydrogen chloride. Pyrolysis of EDC produces VCM and an equal amount of hydrogen chloride as a co-product. This hydrogen chloride produced in the pyrolysis reactor is utilized by the oxychlorination process as one of the reactants. Therefore, the component processes of direct chlorination, EDC pyrolysis and oxychlorination are combined to develop a balanced process for the production of VCM with no net consumption or production of hydrogen chloride ... 

The essential disadvantage of vinyl chloride monomer is associated with the presence of chlorine in its molecule, which, directly and often indirectly in the event that hydrochloric acid is used, results from the electrolysis of sodium chloride, a process known to be highly energy-intensive. 

The flow sheet for a balanced chlorination-oxychlorination of ethylene to vinyl chloride monomer is shown in Figure 2. Currently this process, with its variations involving fixed and fluid beds and different methods of heating and separation, dominates the commercial production of vinyl chloride with 93% of VCM being made by this route. 

By far the greatest part of PVC production across the world is now made by the suspension process. Vinyl chloride monomer (derived from a reaction between ethylene (derived from oil) and chlorine (derived from common salt) is dispersed in deionised water with the help of small quantities of chemical dispersants and polymerisation initiators (typically peroxide compounds). At moderately raised temperature (50 C) and pressure (0.7 MPa) polymerisation proceeds and the polymer can be removed from the resulting slurry by de-watering and steam stripping the unconverted vinyl chloride monomer. 

In 1964, Goodrich, Dow, and Monsanto commercialized oxychlorination processes to make vinyl chloride monomer. The earlier processes either added chlorine to acetylene or ethylene. In the latter, the cracking of the initial product. 

Most vinyl chloride monomer today is made via a three-step process using ethylene oxyhydro-chlorination. A small amount is made by the reaction of acetylene and hydrogen chloride, either as liquids or gases, with a copper chloride catalyst in the liquid process and a mercury catalyst in the gas process. Vinyl chloride is also made by the heating of ethylene chloride with alcoholic alkali. 

Ethylene dicldoride (EDC) is made by the direct chlorination of ethylene [8] in the presence of a catalyst such as iron (III) chloride or copper (II) chloride. EDC is also made by oxychlorination, a process where ethylene reacts with HCl and oxygen in the presence of a catalyst, often copper (II) chloride [9,10]. The EDC is then converted to vinyl chloride, commonly called vinyl chloride monomer (VCM) by a dehydrohalogenation reaction. The VCM is then polymerized to polyvinyl chloride (PVC). 

Ethylene Dichlonde and Vinyl Chloride. In the United States, all ethylene dichloride [107-60-2] (EDC) is produced from ethylene, either by chlorination or oxychlorination (oxyhydrochlorination). The oxychlorination process is particularly attractive to manufacturers having a supply of by-product HCl, such as from pyrolysis of EDC to vinyl chloride [75-01-4] monomer (VCM), because this by-product HCl can be fed back to the oxychlorination reactor. EDC consumption follows demand for VCM which consumed about 87% of EDC production in 1989. VCM is, in turn, used in the manufacture of PVC resins. Essentially all HCl generated during VCM production is recycled to produce precursor EDC (see Chlorocarbons and Cm OROHYDROCARBONS ViNYLPOLYAffiRS). 

This monomer is ethylene when R is hydrogen, propylene when R is a methyl group, styrene when R is a benzene ring, and vinyl chloride when R is chlorine. The polymers formed from these four monomers account for the majority of all commercial plastics. The polymers come in great variety and are made by many different processes. All of the polymerizations share a characteristic that is extremely important from the viewpoint of reactor design. They are so energetic that control of the reaction exotherm is a key factor in all designs. 

---