Manufacture of vinyl chloride

As an example, consider again the manufacture of vinyl chloride. In the first step of this process, ethylene and chlorine are reacted to form dichloroethane ... 

Most of the ethylene dichloride produced is utilized for the manufacture of vinyl chloride, which may be obtained from it by pyrolysis or the action of caustic soda. Large quantities are also used in anti-knock additives for gasoline. As a solvent It has been displaced by trichloroethylene and tetrachloroelhyJene. U.S. production 1978 4-75 megatonnes. 

Chlorine reacts with saturated hydrocarbons either by substitution or by addition to form chlorinated hydrocarbons and HCl. Thus methanol or methane is chlorinated to produce CH Cl, which can be further chlorinated to form methylene chloride, chloroform, and carbon tetrachloride. Reaction of CI2 with unsaturated hydrocarbons results in the destmction of the double or triple bond. This is a very important reaction during the production of ethylene dichloride, which is an intermediate in the manufacture of vinyl chloride ... 

If the production of vinyl chloride could be reduced to a single step, such as dkect chlorine substitution for hydrogen in ethylene or oxychlorination/cracking of ethylene to vinyl chloride, a major improvement over the traditional balanced process would be realized. The Hterature is filled with a variety of catalysts and processes for single-step manufacture of vinyl chloride (136—138). None has been commercialized because of the high temperatures, corrosive environments, and insufficient reaction selectivities so far encountered. Substitution of lower cost ethane or methane for ethylene in the manufacture of vinyl chloride has also been investigated. The Lummus-Transcat process (139), for instance, proposes a molten oxychlorination catalyst at 450—500°C to react ethane with chlorine to make vinyl chloride dkecfly. However, ethane conversion and selectivity to vinyl chloride are too low (30% and less than 40%, respectively) to make this process competitive. Numerous other catalysts and processes have been patented as weU, but none has been commercialized owing to problems with temperature, corrosion, and/or product selectivity (140—144). Because of the potential payback, however, this is a very active area of research. 

Dichloroethylene can be produced by direct chlorination of acetylene at 40°C. It is often produced as a by-product ia the chlorination of chloriaated compounds (2) and recycled as an iatermediate for the synthesis of more useful chloriaated ethylenes (3). 1,2-Dichloroethylene can be formed by contiauous oxychloriaation of ethylene by use of a cupric chloride—potassium chloride catalyst, as the first step ia the manufacture of vinyl chloride [75-01-4] (4). 

An example of an emulsifier for the polymerization of ethylenically unsaturated monomers is a 22 88 mixture of disodium a-sulfolaurate and sodium methyl a-sulfolaurate. The emulsion is stable for much longer than an emulsion with n-dodecylbenzenesulfonate as the emulsifier [92]. Ester sulfonates are also used as emulsifiers in the continuous manufacture of vinyl chloride polymers [93]. 

Write out and balance the overall equation for the manufacture of vinyl chloride from ethylene, chlorine and oxygen. 

In the manufacture of vinyl chloride (VC) by the pyrolysis of dichloroethane (DCE), the reactor conversion is limited to 55 per cent to reduce carbon formation, which fouls the reactor tubes. 

BPR [By-Product Recycle] A process for recycling the chlorine-containing by products from the manufacture of vinyl chloride, 1,2-dichloroethane, and other chlorinated hydrocarbons. Combustion with oxygen converts 90 percent of the chlorine to anhydrous hydrogen chloride, and 10 percent to aqueous hydrochloric acid. Developed by BASF and licensed by European Vinyl Corp. 

Uses. Manufacture of vinyl chloride antiknock agent fumigant, insecticide degreaser compounds rubber cements... 

This so-called balanced oxychlorination vinyl chloride production is the most economical commercial process for the manufacture of vinyl chloride. 

Demonstration of the technical feasibility of producing mixtures of acetylene and ethylene by pyrolysis of hydrocarbons (Wulff process or Kureha process) has led to the manufacture of vinyl chloride from such mixtures. The acetylene component reacts selectively with hydrogen chloride to form vinyl chloride, the residual ethylene is converted to dichloroethane, and the latter is cracked to vinyl chloride, with the resulting hydrogen chloride being recycled. However, this type of process has not achieved the industrial importance of the all-ethylene type of process. 

Acetylene (Figure 13.1) is widely used as a chemical raw material and fuel for oxyacetylene torches. It was once the principal raw material for the manufacture of vinyl chloride (see reaction 13.2.4), but other synthetic routes are now used. Acetylene is a colorless gas with an odor resembling garlic. Though not notably toxic, it acts as an asphyxiant and narcotic and has been used for anesthesia. Exposure can cause headache, dizziness, and gastric disturbances. Some adverse effects from exposure to acetylene may be due to the presence of impurities in the commercial product. 

FIGURE 1 Manufacture of vinyl chloride by the oxychlorination process. 

Dichloroethene (Ethylene Dichloride). Ethylene dichloride (EDC) is one of the truly major petrochemicals. The U.S. production exceeded 18 billion lb in 1999. Almost 95 percent of this went into the manufacture of vinyl chloride monomer. 

Very little significant advance was then made until 1912-1916 when Fritz Klatte discovered the basis for the production of PVC. Patents were granted for the manufacture of vinyl chloride by reacting hydrogen chloride gas with acetylene at 180 °C in the presence of metal chlorides as the catalysts. They also referred to polymerisation by sunlight and suggested some uses for the polymer. 

A number of syntheses using acetylene, by thrir very nature (simplicity of the reaction in a single step, high yield and selectivity etc.), were favored over their counterparts employing ethylene. These included, for example, the manufacture of vinyl chloride or acetate. Inasmuch as resources became available to fund the corresponding investments, such a substitution could be considered in the long term. 

NIOSH (1978) noted that there was a large potential for exposure to 1,1-dichloroethane in the workplace during its use as a dewaxer of mineral oils, extractant for heat- sensitive substances, or fumigant, and in the manufacture of vinyl chloride and high-vacuum rubber and silicon grease. 

Use Manufacture of vinyl chloride vinylidene chloride vinyl acetate acrylates acrylonitrile acetaldehyde per- and trichloroethylene cyclooctatetraene 1,4-butanediol carbon black and welding and cutting metals. 

The pioneer in the field of truly synthetic fibres was Carothers, who demonstrated that two comparatively simple compounds derived from phenol, namely, hexamethylenediamine and adipic acid, could be caused to polymerize to form a potentially fibrous polymer. This was spun into yarn which was successfully placed on the market as nylon. Shortly afterwards ethylene glycol and terephthalic acid were condensed to a polymer from which Terylene or Dacron was made. Ethylene is a by-product in the cracking of petroleum and is the starting point in the manufacture of vinyl chloride and acrlyonitrile, from which Vinyon and the various polyacrylonitrile fibres respectively are spun. 

Tabershaw, L, and Gaffey, W. (1974). Mortality study of workers in the manufacture of vinyl chloride and its polymers. J Occup Med 16, 509-518. 

More than 90 per cent of the ethylene dichloride is used caprively for the manufacture of vinyl chloride. The remainder forms part of the composition of antiknock additives or is used as an intermediate in the production of amines and chlorinated solvents. 

For several years, a number of companies with resources of acetylene and ethylene and even dichloroethane, from different sources, have balanced their manufacture of vinyl chloride without the net production of hydrochloric acid. They have achieved this by using operating schemes of the first two types. These firms include Monsanto, Pechiney-Scint-Gobain, Union Carbide, etc. 

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