Vinyl hydrochlorination

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. 

In the most important process, vinyl chloride obtained from 1,2-dichloroethane is hydrochlorinated to 1,1-dichloroethane which is then thermally or photochemicaHy chlorinated ... 

Other routes to 1,1,2-trichloroethane are chlorination of acetylene in the presence of HCl (101) and chlorination of vinyl chloride at room temperatures with FeCl (102—104), hydrochlorination of cis- and /n j -l,2-dichloroethylene with FeCl catalyst (105), vapor-phase oxychlorination of... 

Halogenation and dehalogenation are catalyzed by substances that exist in more than one valence state and are able to donate and accept halogens freely. Silver and copper hahdes are used for gas-phase reactions, and ferric chloride commonly for hquid phase. Hydrochlorination (the absoration of HCl) is promoted by BiCb or SbCl3 and hydrofluorination by sodium fluoride or chromia catalysts that form fluorides under reaction conditions. Mercuric chloride promotes addition of HCl to acetylene to make vinyl chloride. Oxychlori-nation in the Stauffer process for vinyl chloride from ethylene is catalyzed by CuCL with some KCl to retard its vaporization. 

Hydrochlorination of Alkynes When Thomas and coworkers treated different alkynes in aqueous methanol with HAuC14 and observed the corresponding ketones as major products (Equation 8.28), with less than 5% of methyl vinyl ethers and vinyl chlorides, they were unaware of the fascinating treasure that was in front of them. Some of the most important types of products for gold catalysis were reported in the aforementioned study, but unfortunately at that time this process was believed to be a gold(III) oxidation process, despite the fact that the reaction achieved almost six turnovers. 

Gold(III) was identified as the most active catalyst for that process in 1985, when Hutchings recognized that the efficiency in catalyzing the hydrochlorination of ethyne to vinyl chloride (a very important industrial process that previously used mercury salts as catalysts) correlated with the standard reduction potential of the supported metal cation. That meant that the metal could be found as a transient species in the reaction [10]. 

Vinyl Chloride. Vinyl chloride is an important monomer in the manufacture of polyvinyl chloride and vinyl polymers. Two basic transformations are in commercial use.188-190 The catalytic hydrochlorination of acetylene, once an important... 

The reaction has been carried out using HCI either neat or in acetic acid,84 or in the presence of HgCh,83 BiCla86 or Me4NCl.M In acetic acid, mixtures of syn and anti adducts are produced,84 but reactions catalyzed by HgCl2 proceed by stereospecific anti addition.83-87 The reaction of r-butylacetylene affords the expected vinylic chloride, plus a mixture of isomeric dichloride adducts.84-88 The hydrochlorination of phenylacetyiene produces mixtures of syn and anti adducts in which the ratio is significantly affected by the solvent and catalyst used.84-89-90... 

Vinyl Chloride. Approximately 16.5 billion lb of VCM were produced in the United States in 1999, making it one of the largest-volume petrochemicals. It has been reported that more than 35 percent of the global production of chlorine goes to the manufacture of VCM. Although most of the VCM comes from EDC by the route described previously, it can be obtained from other sources, including its production in the catalytic hydrochlorination of acetylene and as a byproduct in the synthesis of other chlorinated hydrocarbons. 

Hydrogen chloride is an important industrial chemical. The anhydrous form is used in making alkyl chlorides and vinyl chloride from olefins and acetylene, respectively, and in hydrochlorination, alkylation, and polymerization reactions (Sax and Lewis 1987). The hydrated form of hydrogen chloride is hydrochloric acid, which also is used in idustrial processes. 

In this reaction, vinyl chloride, which is formed by the hydrochlorination of acetylene with hydrogen chloride, was not observed from the reaction mixture. This result shows that vinyl chloride does not participate in the formation of dichlorovinylsilane.82... 

Direct chlorination of vinyl chloride generates 1,1,2-tnchloroethane [79-00-5] from which vinylidene chloride required for vinylidene polymers is produced. Hydrochlorination of vinylidene chloride produces 1,1,1-trichloroethane [71-55-6], which is a commercially important solvent. Trichloroethylene and perchloroethylene are manufactured by chlorination, hydrochlorination, or oxychlorination reactions involving ethylene. Aromatic solvents or pesticides such as monochlorobenzene, dichlorobenzene, and hexachlorobenzene are produced by reaction of chlorine with benzene. Monochlorobenzene is an intermediate in the manufacture of phenol, insecticide DDT, aniline, and dyes (see Chlorocarbons a>td Chlorohydrocarbons.)... 

Vinyl chloride is produced in the following industrial reactions (1) the thermal cracking of 1,2-dichlor-oethane, which is produced by the chlorination and/ or oxychlorination of ethylene and (2) the hydrochlorination of acetylene. The vast majority of vinyl chloride is used for the production of polyvinyl chloride (PVC) and the manufacture of copolymers with monomers such as vinyl acetate or vinylidene chloride. A much smaller proportion of vinyl chloride is used in the production of chlorinated solvents - primarily trichloroethanes. 

Use Production of vinyl chloride from acetylene and alkyl chlorides from olefins, hydrochlorination (see rubber hydrochloride), polymerization, isomerization, alkylation, and nitration reactions. 

Interestingly, the deactivation with An catalysts for ethyne hydrochlorination was found to be temperature dependent, and high rates of deactivation were observed at both high and low temperatures. The low-temperature deactivation was caused by coke deposition [252,258], probably the result of surface polymerisation reactions of vinyl chloride and ethyne. The high-temperature deactivation was probed using Au Mossbauer spectroscopy [252,258] and it was found that this was due to the reduction of Au + to An. 

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) ... 

Purification of crude vinyl chloride produced by cracking and hydrochlorination, including the lowering to about 5 ppm of the butadiene content by means ofliquid/liquid countercurrent contact with hydrochloric arid, separation by distillation of the light products returned to hydrochlorination, followed by neutralization with dilute caustic soda, scrubbing with water, drying on molecular sieves, and finally the removal of heavy compounds by distillation. 

A more complex degradation takes place when this process is applied to PVC. The authors propose that PVC depolymerization under supercritical water conditions proceeds in accordance with a mechanism consisting of four different pathways (i) dehydrochlorination and partial oxidation, (ii) dehydrochlorination and chain scission, (iii) dehydrochlorination and total oxidation, and (iv) hydrochlorination. In the reaction products, high yields of vinyl chloride, 1,1-dichloroethane and 1,2-dichloroethane are detected, especially at short reaction times, whereas longer times favour total oxidation products. 

Figure 9-3. Technological scheme of production of the vinyl chloride monomer (1) plasma-chemical pyrolysis (2) cleaning from higher unsaturated hydrocarbons (3) hydrochlorination of acetylene (4) chlorination of ethylene (5) thermal pyrolysis of dichloroethane.

Via thermal or photochemical chlorination of 1,1-dichloroethane. The latter is produced through a route which starts from ethylene chlorination to produce 1,2-dichloroethane, followed by dehydrochlorination to vinyl chloride followed finally by hydrochlorination to produce 1,1-dichloroethane... 

Natural rubber was chlorinated by G.A. Englehard and H.H. Day in 1859, hydrochlorinated in 1881 and isomerized by Leonhardi in 1881 (12). However, these rubber derivatives were not commercialized until the early part of the twentieth century. Likewise, polyvinyl chloride was described by Regnault in 1838, by Meyer in 1866 and by Baumann in 1872 (13,14) but was not commercialized until the 1930 s. It is of interest to note that Baumann considered the solid polymer to be an isomer of vinyl chloride. 

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