Hydrocarbons vinyl chloride monomer process

The current trend for vinyl chloride monomers is toward ethylene as the hydrocarbon raw material, replacing electrochemical acetylene, and it promises to continue. Electrochemical acetylene will be phased out almost completely, except in special cases. The high activation energy level required for forming the acetylene triple bond precludes design of a low cost process for its formation. In addition, the difficulties encountered in handling such a highly reactive material will deter its use. 

Vinyl chloride monomer. .. what you should know, Hydrocarbon Process., pp. 75-92, March 1979... 

Thermal cracking of ethane, propane, butane, naphthas, gas oils, and/or vacuum gas oils is the main process employed for the production of ethylene and propylene butadiene and benzene, toluene, and xylenes (BTX) are also produced. Thermal cracking of these hydrocarbons is also called pyrolysis of hydrocarbons. Ethylene is the organic chemical produced worldwide in the largest amoimts and has been called keystone to the petrochemical industry. This technology is well documented in the literature. Somewhat similar thermal cracking processes are used to produce vinyl chloride monomer (VCM) from ethylene dichloride (EDQ, styrene from ethylbenzene, and allyl chloride from propylene dichloride (PDC). Production of charcoal and coke from wood and coal is actually a pyrolysis process, but it is not discussed here. 

RW McPherson, CM Starks, and GJ Fryar, Vinyl Chloride Monomer.. . . What You Should Know, Hydrocarbon Processing, 55(3) (1979). 

Vinyl chloride monomer (VCM) is prepared commercially in two processes based on different two-carbon hydrocarbons. The balanced process is based on ethylene and the carbide process is based on acetylene. 

By comparing the results for chlorinated polypropylene with those for polypropylene, it can be concluded that the two materials undergo very different pyrolytic reactions. Typical for polypropylene is the formation of fragments of the polymeric backbone with formation of monomer, dimer, etc., or with cleavage of the backbone in random places and formation of compounds with 3n, 3n-1, and 3n+1 carbon atoms (see Section 6.1). Pyrolysis of the chlorinated compound leads to a significant amount of HCI and also char. Very few chlorinated compounds are identified in the pyrolysate, since the elimination of HCI leaves very few chlorine atoms bound to carbons. Some aromatic hydrocarbons are formed by a mechanism similar to that of poly(vinyl chloride) pyrolysis. The elimination of HCI leads to the formation of double bonds, and the breaking of the carbon backbone leads to cyclization and formation of aromatic compounds. The reactions involved in this process are shown below for the case of formation of 1,3-dimethylbenzene ... 

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