Vinyl chloride recovery

Although there are minor differences in the HCl—vinyl chloride recovery section from one vinyl chloride producer to another, in general, the quench column effluent is distilled to remove first HCl and then vinyl chloride (see Eig. 2). The vinyl chloride is usually further treated to produce specification product, recovered HCl is sent to the oxychlorination process, and unconverted EDC is purified for removal of light and heavy ends before it is recycled to the cracking furnace. The light and heavy ends are either further processed, disposed of by incineration or other methods, or completely recycled by catalytic oxidation with heat recovery followed by chlorine recovery as EDC (76). 

Recovery of vinyl chloride Recovery of olefins from... 

Illustration 9.3 Debugging of a Vinyl Chloride Recovery Unit... 

Significant quantities of ethyl chloride are also produced as a by-product of the catalytic hydrochlorination over a copper chloride catalyst, of ethylene and hydrogen chloride to produce 1,2-dichloroethane, which is used as feedstock in the manufacture of vinyl choride (see Vinyl polymers). This ethyl chloride can be recovered for sale or it can be concentrated and catalyticaHy cracked back to ethylene and hydrogen chloride (25). As the market for ethyl chloride declines, recovery as an intermediate by-product of vinyl chloride manufacture may become a predominant method of manufacture of ethyl chloride. 

Dichloroethane is produced commercially from hydrogen chloride and vinyl chloride at 20—55°C ia the presence of an aluminum, ferric, or 2iac chloride catalyst (8,9). Selectivity is nearly stoichiometric to 1,1-dichloroethane. Small amounts of 1,1,3-tfichlorobutane may be produced. Unreacted vinyl chloride and HCl exit the top of the reactor, and can be recycled or sent to vent recovery systems. The reactor product contains the Lewis acid catalyst and must be separated before distillation. Spent catalyst may be removed from the reaction mixture by contacting with a hydrocarbon or paraffin oil, which precipitates the metal chloride catalyst iato the oil (10). Other iaert Hquids such as sdoxanes and perfluorohydrocarbons have also been used (11). 

Lahiere, R. J., et al. Membrane Vapor Separation Recovery of Vinyl Chloride Monrtmer From PVC Reactor Vents. Ind. Eng. Chem. Res. 32 (1993), pp. 2236-2241. 

Figure 3.16. Typical incinerator-heat recovery-scrubber system for vinyl-chloride-monomer process waste...

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

Supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and Soxhlet extraction under various experimental conditions were applied for spiked poly(vinyl) chloride samples. Extracted dyes were separated in an ODS column (250 X 4.6 mm i.d. particle size 5 jum) using methanol as the mobile phase. Dyes are well separated by this method as demonstrated in Fig. 3.59. The optimal parameters of the extraction methods are compiled in Table 3.23. Recoveries depended on both the type of extraction method and the chemical structure of the dye. It was found that the highest recovery can be obtained by MAE and the extraction efficacy was the lowest for Solvent red 24 [129],... 

Monomer and initiator must be soluble in the liquid and the solvent must have the desired chain-transfer characteristics, boiling point (above the temperature necessary to carry out the polymerization and low enough to allow for ready removal if the polymer is recovered by solvent evaporation). The presence of the solvent assists in heat removal and control (as it also does for suspension and emulsion polymerization systems). Polymer yield per reaction volume is lower than for bulk reactions. Also, solvent recovery and removal (from the polymer) is necessary. Many free radical and ionic polymerizations are carried out utilizing solution polymerization including water-soluble polymers prepared in aqueous solution (namely poly(acrylic acid), polyacrylamide, and poly(A-vinylpyrrolidinone). Polystyrene, poly(methyl methacrylate), poly(vinyl chloride), and polybutadiene are prepared from organic solution polymerizations. 

Reclaim is commercially available and suitable for the recovery of VOCs, vinyl chloride, trichloroethylene, carbon tetrachloride, dense non-aqueous-phase liquid (DNAPL) compounds, and, in particular, petroleum hydrocarbons. The vendor states this technology has been used in a wide variety of industrial applications, such as the remediation of groundwater at service stations, dry cleaners, herbicide production facilities, and municipal and industrial landfills, among others. 

TABLE 1 Vinyl Chloride Monomer Recovery Costs... 

Figure 2. Recovery of select hydrocarbons from wet oxidation of poly(vinyl chloride).

Vinyl chloride Carbon tetrachloride Electrolytic conductivity, mass spectrometry GC-MS, recovery of vinyl chloride 77-100% lOOpg L- [200]... 

FIGURE 21 Membrane-based vinyl chloride monomer (VCM) recovery system in a PVC polymerization plant. (Membrane Technology and Research, Inc.) [From Baker, R. W., etal. (2000, December). Chem. Eng. Prog. pp. 51-57.]... 

Then, in the 1970s, a number of poly(vinyl chloride) producers were completely surprised when it was found that long-term (20-year) exposure to vinyl chloride could cause rare forms of tumors.22 After the discovery that vinyl chloride was a carcinogen, venting was not permissible. Containment and recovery of the monomer was mandatory. As a result, some older processes and manufacturing facilities could not be economically modified to incorporate containment, and as a result such operations were discontinued. This case is but one example of the impact that necessary and regulated environmental controls can have on manufacturing processes and operations. 

---