Ethylene, chlorination from ethane

In the future it might be possible to see the gas diffusion technology generating chlorine with energy consumption at 1500 kWh. The chlorine will be used in the direct chlorination of ethane to feed the vinyl chain. Side streams of HC1 will be used in oxychlorination where ethylene is available and this will use up by-product acid from isocyanates. Site integration will increase to benefit from economies of scale and optimise hydrogen chloride production. 

Finally, ethylchloride can be obtained by a combined technique from a mixture of ethane and ethylene. The process is based on combined subsequent reactions of substitutuve chlorination of ethane and hydrochlorination of ethylene with hydrogen chloride obtained from the first reaction ... 

Small amounts of ethylene dichloride (b.p. 83.5°C) are also recovered as a by-product from the direct chlorination of ethane to ethyl chloride (chlor-oethane). 

Formation of the mixed cement-containing systems within the range of low copper concentrations with addition of alkali metal dopants as well as catalytical properties of these systems in the ethane oxidative chlorination process have been investigated. Based on the obtained data the efficient and stable copper-cement catalyst has been worked out. This catalyst will assist in the development of a new technology of the vinyl chloride production from ethane. The basic peirameters of the ethane oxychlorination process have been determined at 623-673K, time-on-stream 3-5s and reactant ratio of C2H6 HCI 02 = 1 2 1 the conversion of ethane is more than 90% and the total selectivity to ethylene and vinyl chloride is 85-90%. 

From Ethane. Ethane is cheaper and more readily available than either ethylene or acetylene. The "Transcat" process involves cracking of a feedstock such as ethane to ethylene, which is chlorinated, oxychlorinated, and dehydrochlorinated simultaneously. Copper oxychloride acts as an oxygen carrier in this process and also functions in the recovery of HCl ... 

High purity vinyl chloride is produced in an overall yield of 80 mol% based on ethane. The feed can contain ethane, ethylene, mixed ethylene-chlorination products, and HCl in various mixtures, and can thereby allow recovery of values from such materials. The flow sheet for the simultaneous chlorination, oxidation, and dehydrochlorination for producing vinyl chloride by the Transcat process is shown in Figure 3. 

The formation of 1,2-dichloroethane from ethane and ethylene is described in patents issued to National Distillers (11) and I.C.I. (12), respectively. Englin et at. (13) report the formation of vinyl chloride from chloroalkanes using catalysts containing melts of cuprous and cupric chloride. The details of the mechanism and kinetics of many of these reactions are still unresolved. It appears, though, that copper chloride can function effectively as a catalyst for chlorination and dehydrochlorination as well as being able to participate in os chlorination reactions. 

Tetrachloroethylene can be prepared direcdy from tetrachloroethane by a high temperature chlorination or, more simply, by passing acetylene and chlorine over a catalyst at 250—400°C or by controlled combustion of the mixture without a catalyst at 600—950°C (32). Oxychl orin a tion of ethylene and ethane has displaced most of this use of acetylene. 

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). 

The reactor vents are due to the non-condensables in both the chlorine and ethylene feeds. In the case of chlorine, the non-condensables are largely the oxygen and inerts (carbon dioxide and nitrogen) as produced from the electrolysers. In the case of ethylene, the non-condensables are largely ethane, which is unreactive. The vent is also saturated with EDC vapour at the vent condenser temperature. 

During maintenance work, simultaneous release of chlorine and acetylene from two plants into a common vent line leading to a flare caused an explosion in the line [10]. The violent interaction of liquid chlorine injected into ethane at 80°C/10 bar becomes very violent if ethylene is also present [11]. The relationship between critical pressure and composition for self-ignition of chlorine—propane mixtures at 300°C was studied, and the tendency is minimal for 60 40 mixtures. Combustion is explosive under some conditions [12]. Precautions to prevent explosions during chlorination of solid paraffin hydrocarbons are detailed [13]. In the continuous chlorination of polyisobutene at below 100°C in absence of air, changes in conditions (increase in chlorine flow, decrease in polymer feed) leading to over-chlorination caused an exotherm to 130°C and ignition [14],... 

With PCE transformation, the product (ethane) was the same for all supports but yields (measured by both ethane and Q production) varied 50-55% ethane yield was obtained on C, 68% yield on Pd/PEI/silica, and 80-85% yield on alumina. The possibility that lower yields resulted from PCE sorbed to the support was considered the C catalyst was therefore heated to 180°C in an attempt to desorb any species. However, only a few nanomoles of PCE (tenths of a percent of the original mass) and traces of lesser chlorinated ethylenes were detected. This suggests that the low ethane... 

Application The modern Vinnolit oxychlorination process produces ethylene dichloride (EDC) by an exothermic reaction from feedstocks including ethylene, anhydrous hydrogen chloride (HCI) and oxygen. Anhydrous HCI can be used from the VCM process as well as from other processes such as isocyanates (MDI, TDI), chlorinated methanes, chlorinated ethanes, epichlorohydrin, etc. 

HTC (1) [High Temperature Chlorination] A general term for the process for making 1,2-dichloro-ethane from ethylene and chlorine by processes operated above the boiling point of the product (83°C). See also CER. 

This reaction is accompanied by complete combustion into water and carbon dioxide. The only selective catalyst known is based on silver. This catalyst was known as early as the 1930s and has been continuously improved since then in a rather empirical way. It has been discovered that the catalyst may be promoted by the addition of alkali metal ions. Moreover, the presence of chlorine has a beneficial effect (cf. Fig. 5.30) [124]. Chlorine has to be added continuously because it disappears from the surface by reacting to give chlorinated ethane. It is sufficient to mix 10-40 ppm chlorine with the feed. The feed consists of a mixture of ethylene (24%), oxygen (8%) and the balance of inert gases. The reaction rate was found to be first order in oxygen and zero order in ethylene in the Shell process. 

Pt seems necessary for complete removal of the chlorine atoms from TCA. Neither a-alumina nor Ti5-alumina (without Pt) produced any pure hydrocarbons. However, when Pt was added to either support, ethane was observed in the effluent. In addition, ethylene was observed in the effluent when the Pt/a-alumina catalyst was used, suggesting a weaker hydrogenation function for the Pt/a-alumina catalyst compared to the Pt/r 8-alumina catalyst. This weaker hydrogenation function may account for the more rapid deactivation since the unsaturated intermediates may polymerize to form coke. 

As in steam cracking, a large number of by-products is produced. Some of them result from the consecutive reactions of the chlorination of vinyl chloride and of its derivatives obtained by dehydrochlorination (tri-, tetra-, pentachloroethane, perchloro-ethane, di-, trichloroethylene. perchloroethyleneX and the others from the hydrochlorination of vinyl chloride il.l-dichloroethane), while others result from decomposition reactions (acetylene, cokei or conversion of impurities initially present (hydrocarbons such as ethylene, butadiene and benzene, chlorinated derivatives such as chloroprene, methyl and ethyl Chlorides, chloroform, carbon tetrachloride, eta, and hydrogen) ... 

Reagent BMC may cause chlorine addition to ethylenic bonds. This does not occur when the steric strain of the product is forbiddingly high as in perchloroethylbenzene (Ballester and Castaner, 1966 Ballester et al., 1961, 1967) and perchlorobibenzyl (Ballester et al., 1967), but it does take place, at least partly, when the steric strain of both the substrate (the ethylene) and the product (the ethane) are comparable. For example, from either styrene [14] or [15], a mixture of 27/-nonachloroethylbenzene and perchlorostyrene is obtained (Ballester and Castaner, 1966 Ballester et al., 1959b, 1961). 

During reductive dechlorination a chlorine atom in the molecule is replaced with a hydrogen atom. The chlorine atom is released to the environment as a chloride ion. Trichloroethylene is reduced to dichloroethylene (primarily cis-dichloroethylene), which can be further reduced to vinyl chloride, then to ethylene and ethane (1-2). In an analysis of data from 61 sites having plumes of chlorinated ethylenes McNab et al. (3) found no evidence of reductive dechlorination at 23 sites, dechlorination to dichloroethene at 18 sites, and dechlorination to vinyl chloride at 20 sites. 

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