Oxychlorination reactor

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). 

Oxychlorination reactor feed purity can also contribute to by-product formation, although the problem usually is only with low levels of acetylene which are normally present in HCl from the EDC cracking process. Since any acetylene fed to the oxychlorination reactor will be converted to highly chlorinated C2 by-products, selective hydrogenation of this acetylene to ethylene and ethane is widely used as a preventive measure (78,98—102). 

By-products from EDC pyrolysis typically include acetjiene, ethylene, methyl chloride, ethyl chloride, 1,3-butadiene, vinylacetylene, benzene, chloroprene, vinyUdene chloride, 1,1-dichloroethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane [71-55-6] and other chlorinated hydrocarbons (78). Most of these impurities remain with the unconverted EDC, and are subsequendy removed in EDC purification as light and heavy ends. The lightest compounds, ethylene and acetylene, are taken off with the HCl and end up in the oxychlorination reactor feed. The acetylene can be selectively hydrogenated to ethylene. The compounds that have boiling points near that of vinyl chloride, ie, methyl chloride and 1,3-butadiene, will codistiU with the vinyl chloride product. Chlorine or carbon tetrachloride addition to the pyrolysis reactor feed has been used to suppress methyl chloride formation, whereas 1,3-butadiene, which interferes with PVC polymerization, can be removed by treatment with chlorine or HCl, or by selective hydrogenation. 

Oxychlorination of ethylene to dichloroethane is the first reaction performed in an integrated vinyl chloride plant. In the second stage, dichloroethane is cracked thermally over alumina to give vinyl chloride and hydrogen chloride. The hydrogen chloride produced is recycled back to the oxychlorination reactor. 

Oxychlorination. This is an important process for the production of 1,2-dichloroethane which is mainly produced as an intermediate for the production of vinyl chloride. The reaction consists of combining hydrogen chloride, ethylene, and oxygen (air) in the presence of a cupric chloride catalyst to produce 1,2-dichloroethane (eq. 24). The hydrogen chloride produced from thermal dehydrochlorination of 1,2-dichloroethane to produce vinyl chloride (eq. 25) is usually recycled back to the oxychlorination reactor. The oxychlorination process has been reviewed (31). 

Removal of metal chlorides from the bottoms of the Hquid-phase ethylene chlorination process has been studied (43). A detailed summary of production methods, emissions, emission controls, costs, and impacts of the control measures has been made (44). Residues from this process can also be recovered by evaporation, decomposition at high temperatures, and distillation (45). A review of the by-products produced in the different manufacturing processes has also been performed (46). Several processes have been developed to limit ethylene losses in the inerts purge from an oxychlorination reactor (47,48). 

Figure 7-5. The European Vinyls Corporation process for producing vinyl chlo-rlde " (1) chlorination section, (2) oxychlorination reactor, (3) steam stripping and caustic treatment of water effluent, (4) EDC distillation, (5) pyrolysis furnace, (6,7,8) VCM and EDC separation, (10) by-product reactor.

Monochlorohenzene is also produced in a vapor-phase process at approximately 300°C. The hy-product HCl goes into a regenerative oxychlorination reactor. The catalyst is a promoted copper oxide on a silica carrier ... 

Ignition in an oxychlorination reactor was attributed to the presence of free space above the packed reaction zone. Other hazards are discussed. 

The oxychlorination reactor is packed with cupric (copper) chloride catalyst. Three feeds, gaseous hydrogen chloride, pure oxygen or oxygen in the form of air, and ethylene are reacted at 600-800°F and 60-100 psi, to form EDC, and water, as in Reaction Three in Figure 9-1. The reaction effluent is then piped over to the cleanup fractionator, where it commingles with the EDC stream from Reaction One and the recycle stream from VC fractionator. 

Commercialization of a new vinyl chloride process has been announced. Instead of the traditional three-step production (see Section 6.3.4), it is based on ethane oxy-chlorination using HC1, 02, and Cl2 carried out over a CuCl-based catalysts.285 Overchlorinated products are dehydrochlorinated and hydrogenated (together with overchlorinated alkenes) in separate reactors these product streams are then led back to the oxychlorination reactor. 

The formation of TRI is undesired, because its removal by distillation is very difficult. In fact, TRI and EDC form a low-boiling point azeotrope very close to EDC. The formation of TRI in the oxychlorination reactor is due to the acetylene entrained with the HC1 byproduct from cracking. Two solutions can be adopted ... 

Because of the high yields, the Vinnolit DC reactor can be operated in the stand-alone mode. However, if the reactor is part of a complete VCM plant, offgas can be sent to the oxychlorination reactor to recover the remaining small quantities of ethylene. If sales-EDC specification is the target, only a small stripper column is required to eliminate traces of HCI. 

Another feed combination that might be used in an over-all vinyl chloride plant would be one in which chlorine is fed to a direct ethylene chlorination unit, and HCl from DCE cracking is recycled to a Kellogg oxychlorination reactor. Approximately half the DCE requirement would come from each of these two units. 

Modify Problem 5.4 using air instead of oxygen as the feed to the oxychlorination reactor. Make a mass balance of the revised process. 

This smaller stream is much easier to handle. Unreacted ethylene is recovered, compressed, reheated and recycled to the oxychlorination reactor. The residual vent stream is then sent to a caustic scrubber to remove chlorinated hydrocarbon contaminants. The remaining stream containing carbon oxides and a low concentration of ethylene can then be incinerated. 

Oxychlorination reactor 2 Catalyst vessel 3 Separator 4 Caustic scrubber 5 Benzene fractionation column 6 Heater 7 Hydrolysis reactor 8 Extraction column 9 HCl stripping column 10 Caustic scrubber 11 Benzene column 12 Chlorobenzene column 13 Phenol column... 

The oxychlorination reactor is a vertical cylindrical shell made of carbon steel with a support grid/air sparger system and internal cooling coils. Internal or external cyclones are used to minimize catalyst carryover. The reactor internal parts are made from corrosion-resistant alloy. The reactor has many design features depicted in Fig. 1. 

The combustion gas leaving the Catoxid process contains hydrogen chloride, water, nitrogen, oxygen, and carbon oxides and can be recycled directly back to the oxychlorination reactor, as shown in Fig. 3. 

Reaction 3 also occurs in the oxychlorination reactor. The chemistry in (A) and reaction 6 yield the net reaction ... 

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