Vinyl chloride route

In summary, path 2 from Example 2.1 is the most attractive reaction path if there is a large market for hydrogen chloride. In practice, it tends to be difficult to sell the large quantities of hydrogen chloride produced by such processes. Path 4 is the usual commercial route to vinyl chloride. 

This route has been completely displaced, first by chlorination and dehydro-chlorination of ethylene or vinyl chloride, and more recendy by oxychlorination of two-carbon raw materials (2) (see Chlorocarbonsandchlorohydrocarbons). 

Once the principal route to vinyl chloride, in all but a few percent of current U.S. capacity this has been replaced by dehydrochlorination of ethylene dichloride. A combined process in which hydrogen chloride cracked from ethylene dichloride was added to acetylene was advantageous but it is rarely used because processes to oxidize hydrogen chloride to chlorine with air or oxygen are cheaper (7) (see Vinyl polymers). 

Akzo Process. Akzo Zout Chemie has developed a route to vinyl chloride and soda ash from salt usiag an amine—solvent system catalyzed by a copper—iodide mixture (13). This procedure theoretically requires half the energy of the conventional Solvay processes. 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

The principal chemical markets for acetylene at present are its uses in the preparation of vinyl chloride, vinyl acetate, and 1,4-butanediol. Polymers from these monomers reach the consumer in the form of surface coatings (paints, films, sheets, or textiles), containers, pipe, electrical wire insulation, adhesives, and many other products which total biUions of kg. The acetylene routes to these monomers were once dominant but have been largely displaced by newer processes based on olefinic starting materials. 

Acetylene and hydrogen chloride historically were used to make chloroprene [126-99-8]. The olefin reaction is used to make ethyl chloride from ethylene and to make 1,1-dichloroethane from vinyl chloride. 1,1-Dichloroethane is an intermediate to produce 1,1,1-trichloroethane by thermal (26) or photochemical chlorination (27) routes. 

Alternatives to oxychlorination have also been proposed as part of a balanced VCM plant. In the past, many vinyl chloride manufacturers used a balanced ethylene—acetylene process for a brief period prior to the commercialization of oxychlorination technology. Addition of HCl to acetylene was used instead of ethylene oxychlorination to consume the HCl made in EDC pyrolysis. Since the 1950s, the relative costs of ethylene and acetylene have made this route economically unattractive. Another alternative is HCl oxidation to chlorine, which can subsequently be used in dkect chlorination (131). The SheU-Deacon (132), Kel-Chlor (133), and MT-Chlor (134) processes, as well as a process recently developed at the University of Southern California (135) are among the available commercial HCl oxidation technologies. Each has had very limited industrial appHcation, perhaps because the equiHbrium reaction is incomplete and the mixture of HCl, O2, CI2, and water presents very challenging separation, purification, and handling requkements. HCl oxidation does not compare favorably with oxychlorination because it also requkes twice the dkect chlorination capacity for a balanced vinyl chloride plant. Consequently, it is doubtful that it will ever displace oxychlorination in the production of vinyl chloride by the balanced ethylene process. 

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... 

Other Routes. A unique process that produces vinyl chloride, trichloroethylene, dichloroethane, and trichloroethane simultaneously has been developed by Produits Chemiques Pechiney-Saint-Gobain in France (31). Dichloroethylene is chlorinated directly at low temperature to tetrachloroethane, which is then thermally cracked to give trichloroethylene and hydrochloric acid. The dichloroethylene feed is coproduced with vinyl chloride in a hot chlorination reactor, using chlorine and ethylene as feedstocks. 

Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene. This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers. Furthermore, during World War II, Reppe developed routes for many other monomers although these were not viable under normal economic conditions. 

For many years a major route to the production of vinyl chloride was the addition of hydrochloric acid to acetylene (Figure 12.5). The acetylene is usually prepared by addition of water to calcium carbide, which itself is prepared by heating together coke and lime. To remove impurities such as water, arsine and phosphine the acetylene may be compressed to 15 Ibf/in (approx. 100 kPa), passed through a scrubbing tower and chilled to -10°C to remove some of the water present and then scrubbed with concentrated sulphuric acid. 

Liquid organic rubbers with reactive functionality can be prepared by several methods. End-functional oligomers are preferred. Chains attached to the network at only one end do not contribute as much strength to the network as those attached at both ends [34], Urethane chemistry is a handy route to such molecules. A hydroxy-terminated oligomer (commonly a polyester or a polyether) can be reacted with excess diisocyanate, and then with a hydroxy methacrylate to form a reactive toughener [35]. The methacrylate ends undergo copolymerization with the rest of the acrylic monomers. The resulting adhesive is especially effective on poIy(vinyl chloride) shown in Scheme 2. 

Strohmeier and Hartmann [14] first reported in 1964 the photoinitiation of polymerization of ethyl acrylate by several transition metal carbonyls in the presence of CCI4. Vinyl chloride has also been polymerized in a similar manner [15,16] No detailed photoinitiation mechanisms were discussed, but it seems most likely that photoinitiation proceeds by the route shown in reaction Scheme (9). 

Vinyl chloride is an important monomer for polyvinyl chloride (PVC). The main route for obtaining this monomer, however, is via ethylene (Chapter 7). A new approach to utilize ethane as an inexpensive chemical intermediate is to ammoxidize it to acetonitrile. The reaction takes place in presence of a cobalt-B-zeolite. 

An alkyne is a hydrocarbon that contains a carbon-carbon triple bond. Acetylene.. H—C= C—H, the simplest alkyne, was once widely used in industry as the starting material for the preparation of acetaldehyde, acetic acid, vinyl chloride, and other high-volume chemicals, but more efficient routes to these substances using ethylene as starting material are now available. Acetylene is still used in the preparation of acrylic polymers but is probably best known as the gas burned in high-temperature oxy-acetylene welding torches. 

The original rnanufacturing route to vinyl chloride (VC) didn t involve ethylene dichloride (EDC) but was the reaction of acetylene with hydrochloric acid. This process was commercialized in the 1940s, but like most acetylene-based chemistry in the United States, it gave way to ethylene in the 1950s and 1960s. The highly reactive acetylene molecule was more sensitive, hazardous,... 

Vinylidene fluoride is taken up rapidly via the pulmonary route in rats, but at equilibrium the mean concentration (by volume) in rats was only 23% of that in the gaseous phase. Metabolism proceeded very slowly and was saturable at exposure concentrations of about 260 mg/m Its maximum rate was 1% that of vinyl chloride and less than 20% that of vinyl fluoride there has been a report of an increase in the urinary excretion of fluoride in exposed rats. No alkylating intermediate was demonstrated after passage through a mouse-liver microsomal system. However, vinylidene fluoride inhibits mixed-function oxidase activity in vitro and, like similar halogenated compounds that are transformed to reactive metabolites, it alters rat intermediary metabolism, leading to acetone exhalation (lARC, 1986). 

World-wide consumption of PVC [poly(vinyl chloride)] has increased dramatically in the past few years. It has now exceeded 8 billion lbs annually. The production of VCM (vinyl chloride monomer) has also been expanded to meet the PVC demand. Future trends for VCM and PVC pro-ductions for the next five years can be forecast on the basis of the raw materials sources, the different process techniques in manufacturing VCM and PVC, and their relative economics, technical merits, and limitations. VCM will be produced principally through the ethylene route by fluid-bed oxyhydrochlorination of ethylene and thermal cracking of ethylene dichloride. PVC will be produced by various processes resulting in more specialized PVC varieties tailored for specific end markets and new processing technologies. 

Technological advances in the production of the vinyl chloride monomer (VCM) have contributed to the declining price of the polymer. Figure 4 illustrates this statement the price of the vinyl chloride monomer (1) over a period of 20 years is plotted against two curves that represent the annual production of monomer made from two different bases, acetylene and ethylene. The classic acetylene route was the first to be exploited commercially, but its popularity has declined as more processes were developed that could utilize ethylene, a cheaper base. 

This process is shown schematically in Figure 7. The ethylene part of the feed reacts with chlorine in the liquid phase to produce 1,2-di-chloroethane (EDC) by a simple addition reaction, in the presence of a ferric chloride catalyst (9). Thermal dehydrochlorination, or cracking, of the intermediate EDC then produces the vinyl chloride monomer and by-product HC1 (1). Acetylene is still needed as the other part of the over-all feed, to react with this by-product HC1 and produce VCM as in the all-acetylene route. 

The most readily available alkenyl halide is chloroethene (vinyl chloride), which can be prepared by a number of routes ... 

Vinyl chloride is the only unsaturated chloride which has been studied by monoisotopic photosensitization. The abundance of 20211 g in the calomel product, as a function of substrate pressure, is shown in Figure 19. The highest value obtained was 0.5 2. Tire measured value of the quantum yield for calomel formation was 0.19 and, for the isotopically specific step, 0.053. In order to explain the low efficiency in the calomel-forming primary step a third primary route was postulated ... 

This novel synthetic route to pyrroles from ketoximes, based on the use of vinyl chloride instead of acetylene, allowed a one-pot preparation of almost inaccessible 4,5-dihydrobenzo[g]indole (38) and its previously un-... 

A graph circle is a final sequence of the edges in which no node except the starting point occurs twice. A graph for the isomerization reaction has one circle, whereas that for vinyl chloride synthesis contains two circles. Every route of a chemical reaction corresponds to a graph s circle and vice versa. The number of independent reaction routes is equal to the number of elements in the basis of circles. It permits us to determine independent reaction routes from the graph type. 

The mechanism for the synthesis of vinyl chloride, eqns. (24), whose graph is given in Fig. 3(d), also has two routes with one "natural brutto-equation. Without taking into account the reversibility of steps (1) and (3), the rate of product formation will be... 

It is possible that the reaction with the only brutto-equation will follow several routes. For example, the reaction of vinyl chloride synthesis... 

We can also give examples of two-route mechanisms belonging to this class a detailed mechanism for vinyl chloride synthesis [17]... 

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