Ethylene, chlorination with chlorine

Chlorinated C2> Perchloroethylene (PCE) and trichloroethylene (TCE) can be produced either separately or as a mixture in varying proportions by reaction of C2-chlorinated hydrocarbons, eg, C2-chlorinated waste streams or ethylene dichloride, with a mixture of oxygen and chlorine or HCl. 

In oxychlorination, ethylene reacts with dry HCl and either air or pure oxygen to produce EDC and water. Various commercial oxychlorination processes differ from one another to some extent because they were developed independentiy by several different vinyl chloride producers (78,83), but in each case the reaction is carried out in the vapor phase in either a fixed- or fluidized-bed reactor containing a modified Deacon catalyst. Unlike the Deacon process for chlorine production, oxychlorination of ethylene occurs readily at temperatures weU below those requited for HCl oxidation. 

Ethylene is currently converted to ethylene oxide with a selectivity of more than 80% under commercial conditions. Typical operating conditions are temperatures in the range 470 to 600 K with total pressures of 1 to 3 Mpa. In order to attain high selectivity to ethylene oxide (>80%), alkali promoters (e.g Rb or Cs) are added to the silver catalyst and ppm levels of chlorinated hydrocarbons (moderators) are added to the gas phase. Recently the addition of Re to the metal and of ppm levels of NOx to the gas phase has been found to further enhance the selectivity to ethylene oxide. 

The chemical structure for common chlorinated solvents is shown in Figure 4.5. Chlorinated solvents such as TCE and PCE are composed of double-bonded carbon or ethylene structures with three and four chlorine atoms, respectively. The ethane derivative 1,1,1-TCA has three chlorine atoms. Freon is a chlorofluorocarbon and is also an ethane derivative with four chlorine atoms and three fluoride atoms. 

Figure 9—2 shows the plant with its three reactors. The pyrolysis furnace is in the middle. At the top of the figure, the basic feeds, to the plant are shown—ethylene, chlorine, and oxygen. Ethylene and chlorine alone are sufficient to make EDC via the route on the left. The operation, call it Reaction One like Figure 9-1 does, takes place in the vapor phase in a reactor with a fixed catalyst bed of ferric (iron) chloride at only 100—125°F. A cleanup column fractionates out the small amount of by-products that get formed, leaving an EDC stream of 96—98% purity. 

Note Bis(2-chloroethyl) ether is produced by the chlorination of ethylene glycol or by treating ethylene chlorohydrin with sulfuric acid. Therefore, either ethylene glycol or ethylene chlorohydrin may be present as impurities. 

Alkanes. The chlorination of ethane known to produce more 1,1-dichloroethane than 1,2-dichloroethane is explained by the so-called vicinal effect.115 One study revealed285 that this observation may be explained by the precursor 1,2-dichloroethane radical (the 11 2-chloroethyl radical) thermally dissociating into ethylene and a chlorine atom [Eq. (10.54)]. Indeed, this radical is the major source of ethylene under the conditions studied. At temperatures above 300°C, the dissociation dominates over the chlorination reaction [Eq. (10.55)], resulting in a high rate of ethylene formation with little 1,2-dichloroethane ... 

The reactions of ethylenes substituted with fluorine and chlorine were determined by Anicich, Bowers and coworkers211-216. Su and collaborators217 tested several reactions of fluoroalkyl radical anions with C2F4 ... 

The simulation of the ethylene chlorination can be done as an adiabatic PFR with a liquid superficial velocity between 0.1 and 0.3 m/s. The results obtained by Aspen Plus [19] by using a scheme such as that shown in Figure 7.3(a) with the kinetic equations (7.1) and (7.2) is in good agreement with the industrial practice. 

Figure 10.11 shows an integrated plant for producing EDC and vinyl chloride from ethylene, chlorine, and air. In this process, vinyl chloride (VCM) is produced by the thermal cracking of EDC. The feed EDC may be supplied from two sources. In the first source, ethylene and chlorine are reacted in essentially stoichiometric proportions to produce EDC by direct addition. In the second source, ethylene is reacted with air and HC1 by the oxychlorination process. Ideally, both processes are carried out in balance, and the oxychlorination process is used to consume the HC1 produced in the cracking and direct chlorination steps. The chemical reactions are... 

Vin Tec Ethylene dichloride (EDC) via lean oxychlorination Ethylene, chlorine Oxychlorination process producess EDC cost-effectively with an exothermic, cooper catalyst-based process NA NA... 

ABB Lummus Global/Solvay SA Vinyl chloride monomer (VCM) EDC and/or ethylene, chlorine Advanced pyrolysis design with high EDC conversion and long furnace run lengths energy efficient NA NA... 

O2) or (CIF3 + water). Potentially explosive polymerization reaction with ethylene. Incompatible with 1,1-dichloroethylene oxygen. When heated to decomposition it emits toxic fumes of F and CL. See also CHLORINATED HYDROCARBONS, ALIPHATIC and FLUORIDES. 

Mineralization of chloro-ethylenes decreases with the increase in chlorine atom substitution on the C=C bond and oxidation of nitrogen-containing compounds is slow when compared to the compounds containing phosphorus, sulfur, and chlorine. Photooxidation in a mixture of organics is complicated as the rate of one compound may be inhibited or enhanced by the presence of others (4). 

Chlorohydrins and dichloroalkanes are formed in electrogenerative chlorination of olefins on platinum black (50). The former predominate at high currents and low anode potentials, with no side reactions of chlorides, such as chlorine evolution. From the identified products, the following tentative mechanism has been proposed for ethylene chlorination (50) ... 

Figure 5.2, also taken from Schwarz et al. [21], illustrates how metrics for ethylene, chlorine, vinyl chloride and poly(vinyl chloride) (PVC) can be stacked to obtain metrics for the production of PVC, beginning with naphtha and brine. The metrics calculated with the mass denominator can be readily combined. Impact per dollar can also be calculated for a supply chain by combining the single values along the chain in... 

Ethane reacts with chlorine to make ethyl chloride and hydrogen chloride, and ethylene reacts with hydrogen chloride to form ethyl chloride. 

Ethylene glycol was available in abundant quantities because it was derived from ethylene, a by-product in the cracking of petroleum. Ethylene, treated with chlorine water, yields ethylene chlorhydrin, which is converted to ethylene glycol when heated with a mild alkali such as sodium carbonate or calcium hydroxide. 

Fig.-11.4 b. Ethylene dichloride manufacture by ethylene chlorination. with vapor phase effluent recovery. 

The 3,5a-dichloro-seco-steroid (396), which could not be prepared directly from the seco-diol (397), was obtained by a two-stage chlorination starting with the 3-acetate of (397). The seco-steroid (398) was the major product (35 %) formed on brief treatment of 5,6a-epoxy-5a-cholestan-3-one ethylene acetal with boron trifluoride etherate in benzene. ... 

Fluorides from ethylene derivatives with simultaneous replacement of chlorine by fluorine... 

A balanced VCM process produces only vinyl-cloride by combining three reaction steps direct ethylene chlorination to 1,2-dichloroethane (DCE), cracking of DCE to VCM, and recovery of HCl by oxychlorination with ethylene. The global stoichiometry may be described by the simplified scheme ... 

The influence of hydrochloric acid concentration appeared to be similar to that in the case of aromatic compounds chlorination in the electrochemical system. While working with aphite electrodes in 27 - 30 hydrochloric acid solutions at the range of current density values from 1 to 4 IcA/m, and at the range of temperatures from 35 to 80°C, the dominating product of ethylene chlorination reaction was stated to be 1,2-dichloroethane. At 35°C, the yield of ethylene chlorination products is 68-8056 at rather low current densities. The increase in the temperature of chlorination process up to 50°C, at the same current densities cause the fiy-owth of the diohloroethane content in the mixture up to 77% - 92%. Though temperature growth to 65°C leads to some increase in total mixture mass of ethylene chlorination products, however, the substance yield of 1,2-diohloroethane is only 75-80%, as lateral processes take place. While temperature rises to SO C,... 

There are little grooves in the top of the electrode plates. They seacve for initial and final products to leave of both anode and cathode chambers. The products of ethylene chlorination as a vapor are sent to condense via ceirbine, whereas the wastes of hydrochloric acid (with concentration up to 5%) mixed with the hydrogen, formed on the cathode is sent to the gas drain via carbine. 

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