| |
The C2 chlorinated solvents that have major commercial significance
are perchloroethylene (PCE) and trichloroethylene (TCE). Use of 1,1,1-trichloroethane
(1,1,1-TCA; also referred to as methyl chloroform) has been phased out for
emissive uses in Europe, the United States, Japan and other industrial countries
because of its ozone depletion potential (ODP) in the upper atmosphere. Consequently,
global production largely ceased by the late 1990s, except for use as a feedstock.
PCE has been the dry cleaning fluid of choice for a number of decades; however,
users have drastically reduced consumption by using equipment designed to minimize
losses of the solvent and following proper work practices. In the United States,
use of PCE for dry cleaning decreased from 103 thousand metric tons in 1990
to 17 thousand metric tons in 2005. Over the same time period, use was cut
from 115 thousand metric tons to 34 thousand in Western Europe, and from 16
thousand metric tons to 4 thousand in Japan.
Emissive uses of 1,1,1-TCA are very minor, except in the less industrialized
world. Countries like China and India have agreed to cease use of 1,1,1-TCA
and CFCs no later than 2010. PCE and TCE have experienced some increase in
sales as replacements for 1,1,1-TCA in metal cleaning, aerosols and other uses,
but this is expected to level off. Canada now requires all dry cleaners to
use equipment that minimizes PCE loss. In Western Europe, TCE has been reclassified
into a more severe toxicity class, so some replacement with PCE is expected.
Currently, the largest applications for all three C2 chlorinated
solvents are as feedstocks for fluorocarbons. PCE has historically been used
to make chlorofluorocarbons (CFCs) CFC-113, CFC-114 and CFC-115. This end use
has almost totally disappeared, as emissive uses of these materials have been
banned in most countries because of their contribution to ozone depletion.
Both PCE and TCE are used to make hydrofluorocarbon-134a (HFC-134a), which
is the most popular alternative to CFC-12 refrigerants, and lesser quantities
of HCFC-123, HCFC-124 and HFC-125. PCE is used in the United States and Japan.
1,1,1-TCA is used principally to make HCFC-141a and HCFC-142a.
In Western Europe, demand for chlorinated solvents is expected to decline
steadily during the forecast period. During 2000–2005, demand for PCE
and TCE declined by 11% per year.
Chinese demand for PCE and TCE is expected to continue to exhibit growth.
Despite the abundant supply of TCE from overseas producers, China started up
a 15 thousand metric ton TCE plant in Zhejiang in 2005.
|
