CEH Report
Table of Contents
Abstract
The C2 chlorinated solvents that have major commercial significance are trichloroethylene (TCE), perchloroethylene (PCE) and 1,1,1-trichloroethane or methyl chloroform (TCA). Consumption of these solvents has been negatively impacted by declines in emissive applications caused by regulations related to the 1987 Montreal Protocol on ozone depleting chemicals and the 1997 Kyoto Protocol on global warming and climate change. Use of TCA has been phased out beginning January 1, 1996 in most countries because of its ozone depletion potential in the upper atmosphere. Consequently, global consumption of all three solvents is now heavily dependent on use as a feedstock in the production of fluorocarbons.
Over the past two decades, the global fluorocarbons market has undergone a number of major transitions toward greater use of non-ozone-depleting HFCs and non-global-warming, nonfluorocarbon alternatives in emissive applications. Consumption in the largest market segment, refrigeration and air conditioning, was negatively impacted by both the Montreal and Kyoto Protocol amendments and legislations and there are current and proposed regulations limiting future production, consumption and trade in CFCs, HCFCs and HFCs.
The following pie chart shows world consumption of the major C2 chlorinated solvents:
Halogenated solvents have historically been used heavily as solvents in several key markets, including metal cleaning, dry cleaning, electronics cleaning and paint stripping. Many halogenated solvents are available commercially, but methylene chloride (MeC), TCE and PCE are the most widely used today. These compounds are considered nonphotochemically reactive by many regulatory agencies and therefore do not have to be included in measuring volatile organic compound (VOC) content. Another advantage is that they are nonflammable, meaning they do not exhibit a flash point in normal testing, making them attractive especially for cleaning metals and textiles at elevated temperatures. They are heavier than air, so they tend to remain in application machines that are properly designed. They are stronger solvents than hydrocarbons because they are more polar. In addition, MeC, TCE and PCE are priced competitively with most other solvents.
However, they are all considered to be hazardous air pollutants (HAPs), toxicity concerns persist, and the emissions must be reported under the Superfund Amendment and Reauthorization Act (SARA), so the industry continues to investigate alternatives.
Prior to the 1990s, two other halogenated solvents were used in large quantities. They are methyl chloroform (1,1,1-trichloroethane or TCA) and chlorofluorocarbon 113 (CFC-113). However, in the 1980s, it was discovered that these two solvents and several other halogenated compounds contributed to depletion of the upper atmospheric ozone layer. As a consequence, their production and consumption in most regions of the world were banned by 1995.
Over the next five years, global demand for both TCE and PCE is projected to increase at about 1.5% annually, while TCA demand is forecast to decline at 0.9% per year. During 2011–2016, China is projected to have the highest average annual growth rates for TCE at just over 4.5% and for PCE at almost 6%, while Japan is projected to have the largest decline for TCA at 5% per year.