|Molecular formula||C 2 H 3 Cl|
colorless and odorless gas
|External identifiers / databases|
|Molar mass||62.5 g mol −1|
2.86 kg m −3 (0 ° C and 1.013 bar)
−153.7 ° C
−13.4 ° C
0.33 M Pa (20 ° C)
1.3700 (20 ° C)
|ΔH f 0||
37.2 kJ / mol
|As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C|
Vinyl chloride ( chloroethene , also monochloroethene or - actually outdated - monochloroethylene ), abbreviated to VC , is a colorless, flammable, narcotic gas with a slightly sweet, chlorine- like odor in high concentrations . It is the basic substance for the production of polyvinyl chloride (PVC). Vinyl chloride was discovered by Henri Victor Regnault .
Extraction and presentation
The first process for the technical production of vinyl chloride was developed by the chemical factory Griesheim-Elektron . Thereafter, acetylene with hydrogen chloride in a hydrochlorination at temperatures of 140-200 ° C at normal pressure, mercury (II) chloride - catalysts which on charcoal reacted are supported.
The entire reaction takes place in the gas phase and is carried out in tube bundle reactors , which cool the exothermic reaction (ΔH R = –98.8 kJ · mol −1 ) with the aid of an oil circuit. The acetylene conversion is almost quantitative at 96-97% and the vinyl chloride selectivity is 98-99%. The process is generally very selective and requires little equipment.
The use of acetylene as a raw material for industrial vinyl chloride production has lost a lot of its importance in the last few decades. The high cost of acetylene in contrast to cheaper and more readily available raw materials based on petrochemical production , especially ethene , meant that by the turn of the millennium only 5% of vinyl chloride was still produced on the basis of acetylene.
In the last few years the situation has changed again significantly. Today, almost 23% of vinyl chloride is again made from acetylene. This can be explained by the fact that the current synthesis of vinyl chloride based on acetylene (often also in processes coupled with the EDC route), especially in regions where acetylene is still available inexpensively as a raw material and can also be extracted cheaply ) he follows. This process is still profitable, especially in China and South Africa - both areas that still have large coal and rock salt deposits and low additional costs (e.g. electricity).
In a subsequent step, the 1,2-dichloroethane is converted to vinyl chloride with elimination of hydrogen chloride.
In 2010, around 35 million tons of vinyl chloride were used worldwide.
Vinyl chloride is easily flammable (ignition temperature 435 ° C). With a volume fraction of 3.8 to 31 percent in air, it is explosive. Vinyl chloride condenses at −13.9 ° C and solidifies at −154 ° C.
Vinyl chloride polymerizes to polyvinyl chloride when exposed to light, air and heat . Burning vinyl chloride produces hydrogen chloride and traces of phosgene . Vinyl chloride dissolves almost indefinitely in organic solvents, but only slightly in water . The heat of polymerization is −71 kJ mol −1 or −1135 kJ kg −1 .
The main use of vinyl chloride is to make polyvinyl chloride (around 38 million tons in 2004). This is done by means of radical polymerisation . In the past, vinyl chloride was also used as a coolant under various names.
In its Air Quality Guidelines for Europe , the WHO assumes that the average air concentration generally present in Western European countries is between 0.1 and 0.5 μg / m 3 . In the vicinity of vinyl chloride and polyvinyl chloride systems, the 24-hour concentrations can exceed 100 μg / m 3 . At distances of over one kilometer from the system, they are usually below 10 μg / m 3 . VC decomposes in air and has a half-life of 20 hours. The WHO assumes that with a lifetime exposure to 1 μg / m 3 the cancer risk is 1 in 1 million.
In 1974 in the Federal Republic of Germany the emission of vinyl chloride during the production of PVC was between 15 and 55 kg per tonne of PVC produced, but two years later it was reduced to values between 8 and 20 kg per tonne of PVC produced.
For a long time, vinyl chloride was only classified as narcotic and irritating to the eyes. The toxic properties to humans were first recognized in the 1960s. It was not until the early 1970s that the clinical picture of vinyl chloride disease was recognized. The liver , esophagus and spleen, as well as the blood flow to the hand, hand bones and skin are affected.
Hans Popper (1903–1988) made the important observation that occupational exposure to vinyl chloride is hepatotoxic and often leads to the occurrence of hepatic angiosarcoma . It has been classified as carcinogenic and can cause hemangioendothelial sarcomas of the liver , for example .
The limit values for the maximum vinyl chloride concentration at the workplace were continuously reduced: in 1966 the MAK value was 500 ppm , in 1971 100 ppm and 1974 50 ppm. Due to the carcinogenicity that has now been proven , no MAK limit value can be established today.
Respiratory protection and full protection are necessary as protective measures during handling. The storage takes place in pressure cans and cylinders.
The binding occupational exposure limit for vinyl chloride in the European Union is 3 ppm or 7.77 mg · m −3 (2004/37 / EC). An occupational exposure limit according to TRGS 900 is currently not specified for vinyl chloride in Germany. However, vinyl chloride is on the processing list of the Committee for Hazardous Substances (as of September 2014) with the aim of proposing an occupational exposure limit for inclusion in TRGS 900 or deriving an exposure-risk relationship (ERB) according to TRGS 910. Vinyl chloride is classified as a category K1 carcinogen (substances known to be carcinogenic in humans).
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