Journal of Fluorine Chemistry 114 (2002) 237–250
CFC phase-out: have we met the challenge?
Richard L. Powell*
UMIST, P.O. Box 88, Manchester M60 1QD, UK
Received 18 September 2001; received in revised form 14 December 2001; accepted 15 December 2001
Abstract
In 1974 Nobel prize winners Rowland and Molina proposed that chlorofluorocarbons (CFCs) were stable enough to reach the stratosphere,
where, under intense solar radiation they released Cl atoms that could destroy stratospheric ozone protecting the earth’s surface from UV rays.
The CFC industry funded both scientific studies to test the Rowland and Molina hypothesis and programmes to identify potential
replacements, from which the HFCs emerged as likely candidates. After 5 years it was concluded, on the best scientific evidence available,
that stratospheric ozone was being depleted at 3% per decade, but sufficient time was available for an orderly phase-out. Although the USA
and a few other countries stopped the use of CFCs in aerosols little further work was done until 1985 when the CFC debate was renewed
following the discovery of stratospheric ozone depletion over the Antarctic during its spring. Manufacturers restarted their R&D programmes;
governments negotiated the Montreal Protocol in 1987 agreeing the partial phase-out of the CFCs. As a result of subsequent amendments
CFCs have now been phased-out in the developed world and HCFCs will follow over the next two decades. This paper reviews what has been
achieved and what remains to be done. Has the world-wide effort been successful in protecting the ozone layer? Have ‘‘acceptable’’
alternatives been found for the CFCs/HCFCs in their various applications? # 2002 Published by Elsevier Science B.V.
Keywords: Chlorofluorocarbon; Hydrochlorofluorocarbon; Hydrofluorocarbon; Refrigerant; Montreal Protocol; Ozone depletion; Global warming;
Trifluoroacetate
1. Introduction
Concern about the impact of chlorofluorocarbons (CFCs)
and hydrochlorofluorocarbons (HCFCs) on the atmosphere
goes back almost 30 years, and phase-out of HCFCs in the
industrially developed nations will be completed by 2030 at
the latest. Clearly this half-way point is an opportune time to
review progress and to ask whether the programme will be
successful. In the context of this paper it is not possible
to explore all the major applications of CFCs/HCFCs and
to discuss their replacements comprehensively. My own
experience mainly lies in the area of refrigerants so this
paper is biased towards these products. Furthermore, I shall
illustrate the issues involved using the major refrigerants
CCl2F2 (CFC-12) and CHClF2 (HCFC-22) as examples.
Similar considerations apply to lower tonnage refrigerants
although the details vary from case to case.
2. History
In the 1970s Lovelock and co-workers, using his newly
developed electron capture detector, demonstrated that
*
Tel.: þ44-1829-261447; fax: þ44-1829-261447.
E-mail address: [email protected] (R.L. Powell).
0022-1139/02/$ – see front matter # 2002 Published by Elsevier Science B.V.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 0 3 0 - 1
CFCs 11 and 12 were trace constituents in the atmosphere
[1–3]. In hindsight, perhaps this observation should not
have been surprising given that a significant fraction of
CFC production was either purposely vented from aerosol
packages or inadvertently lost from leaking refrigeration and
air-conditioning systems. In 1972, at a meeting initiated by
DuPont, representatives of the leading CFC manufacturers
discussed the environmental fate of their products. Ray
McCarthy succinctly summarised their remit in the following way: ‘‘Fluorocarbons are intentionally or accidentally
vented to the atmosphere world-wide at a rate approaching
one billion pounds per year. These compounds may be either
accumulating in the atmosphere or returning to the surface,
land or sea, in pure form or as decomposition products.
Under any of these alternatives it is prudent that we investigate any effects which the compounds may produce on
plants or animals now or in the future.’’
As a result the CFC manufacturers formed the Fluorocarbon
Panel to investigate the environmental impact of CFCs, a
programme which was pointed in a very specific direction
when Molina and Rowland published their 1974 paper
proposing that CFCs could destroy stratospheric ozone [4].
Although the chemical industry is often depicted as riding
rough-shod over environmental concerns, in case of the
CFCs the fluorocarbon producers adopted a demonstrably
238
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
responsible attitude [5]. Through the Fluorocarbon Panel
they jointly funded an extensive and high quality atmospheric
research programme to test the validity of the Rowland and
Molina hypothesis using independent experts who were free
to publish their results as peer reviewed papers in reputable
journals. Simultaneously, each company initiated its own
research programme to identify CFC replacements which
retained the advantages of CFCs, notably low toxicity and
non-flammability, while avoiding their implied threat to the
ozone layer.
The atmospheric research programme confirmed that CFCs
were likely to deplete stratospheric ozone, as predicted by
Rowland and Molina, with the best computer models available at the time indicating a rate of about 3% per decade. The
observational techniques in the late 1970s were thought to be
incapable of detecting any depletion that had already
occurred. It was concluded that CFCs should be phasedout, but that this could occur over a sufficiently long period to
minimise the economic impact of the change to CFC users.
Nevertheless, several countries, most notably the USA, unilaterally banned the use of CFCs in most aerosols and by
1980 this had significantly reduced world CFC production.
The company programmes identified that hydrofluorocarbons (HFCs) offered the desired combination of properties,
especially CF3CH2F (HFC-134a) which was reasonably
similar in thermodynamic properties to CFC-12 and might
therefore replace it as a refrigerant. CH2F2 (HFC-32),
CF3CH3 (HFC-143a) and CF3CF2H (HFC-125) also emerged
as candidate low boiling refrigerants. However the atmospheric science studies suggested that CHClF2 (HCFC-22),
the major low boiling refrigerant currently in production,
could continue, because hydroxyl radicals largely destroyed
it in the troposphere, so little reached the stratosphere. Since
the CFCs producers were generating the same candidate
replacements they shared safety data, notably toxicology
results, under the auspices of the Fluorocarbon Panel. By
1980 companies had designed pilot plants for HFC-134a
production; but a combination of the early 1980s recession
and the change in the American political climate after the
1980 presidential election resulted in the shelving of these
projects. Despite the reduction in interest, in 1981 the
‘‘Vienna Convention to protect the ozone layer’’ was signed
by interested states although CFCs were only mentioned in
an annexe as compounds that needed to be watched.
In 1984 a remarkable and totally unpredicted phenomenon was discovered by the British Antarctic Survey, the
so-called ‘‘ozone hole’’ [6]. During the Antarctic spring
in October, when the sun first rises above the horizon, a
major, although temporary, loss of stratospheric ozone
was observed. Chlorine injected into the stratosphere by
the CFCs was the prime suspect. In 1985 this unexpected
observation was discussed at a meeting of the Vienna
Convention when it was decided that world-wide regulations
were required to control the production and emissions of
chlorine containing gases. In 1987 governments negotiated
the Montreal Protocol, the first international treaty to protect
the global environment [7]. This agreement originally mandated a 50% reduction in CFC production and consumption
by 1 July 1999, but, importantly, allowed for future revision
in light of new scientific evidence. Subsequent atmospheric
studies and computer models superior to those available
10 years previously suggested that ozone was likely to be
depleted at faster rate than had been previously thought.
Following revisions of the Protocol the complete phase-out
of CFCs and HCFCs were also mandated; Table 1, based on
information from [7], summarises the present position.
Although the European Union did not convince other signatories to the Protocol to accept proposals for earlier CFC
and HCFC phase-out, it decided to include them in its own
regulations.
The phase-out of CFCs in the developed countries proved
to be slower than was anticipated by national governments.
Quite legally, users and distributors stockpiled considerable
quantities of CFCs to delay the ultimately inevitable switch
to alternative fluids. Totally illegally, significant amounts of
CFCs were smuggled into developed countries from developing countries, who were allowed to continue production.
Ironically, the high tax imposed by the USA on CFCs to
reduce their use made smuggling even more profitable.
Smuggled ‘‘virgin’’ CFC was often labelled as ‘‘re-cycled’’
product since the trading of this material was not illegal. To
overcome the problem the European Union unilaterally
banned the use of all recycled CFCs from January 2000.
CFC recycling is still allowed in the USA and it has even
become attractive to recover CFC-12 from its azeotrope with
CHF2CH3 (HFC-152a) known as R500.
3. Selecting fluorocarbon replacements
for CFC refrigerants
In response to renewed concern over CFCs following the
discovery of Antarctic ozone depletion the manufacturing
companies restarted their development programmes for
the environmentally acceptable replacements. Since their
introduction in the early 1930s equipment designs had been
specifically optimised around the properties of CFCs and
HCFCs. Through careful attention to detail and the adoption of conservative design practices, the refrigeration and
air-conditioning industry had developed reliable, safe products. Not surprisingly, what the equipment manufacturers
required were new fluids having properties as close as
possible to the current fluids to minimise design changes.
The generally accepted, key requirements for the replacement fluids were the following.
Thermodynamic properties as close to original refrigerants: in particular maximum operating pressures
should not be significantly above those of the chlorinated
refrigerants.
Non-flammable.
Non-toxic.
Miscible with acceptable lubricants.
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
239
Table 1
Montreal Protocol control measures
Date
Control measure
1 July 1989
1 January 1992
&
&
Freeze of annex Aa CFCs
Freeze of halons
1 January 1993
&
&
Annex B CFCsb reduced by 20% from 1989 levels
Freeze of methyl chloroform
1 January 1994
&
&
&
&
Annex B CFCs reduced by 75% from 1989 levels
Annex A CFCs reduced by 75% from 1986 levels
Halonsc phased-outd
Methyl chloroform reduced by 50%
1 January 1995
&
&
Methyl bromide frozen at 1991 levels
Carbon tetrachloride reduced by 85% from 1989 levels
1 January 1996
&
&
&
&
&
HBFCsd phased-oute
Carbon tetrachloride phased-outd
Annex A and B CFCs phased-outd
Methyl chloroform phased-outd
HCFCsf frozen at 1989 levels of HCFC þ 2.8% of 1989 consumption of CFCs (base level)
1 January 1999
1 July 1999
1 January 2001
&
*
&
Methyl bromide reduced by 25% from 1991 levels
Freeze of annex A CFCs at 1995–1997 average levelsg
Methyl bromide reduced by 50% from 1991 levels
1 January 2002
*
*
Freeze of halons at 1995–1997 average levelsg
Freeze of methyl bromide at 1995–1998 average levels
1 January 2003
&
*
*
Methyl bromide reduced by 70% from 1991 levels
Annex B CFCs reduced by 20% from 1998–2000 average consumptionh
Freeze in methyl chloroform at 1998–2000 average levels
1 January 2004
&
HCFCs reduced by 35% below base levels
1 January 2005
&
*
*
*
*
Methyl bromide phased-out
Annex A CFCs reduced by 50% from 1995–1997 average levelsg
Halons reduced by 50% from 1995–1997 average levelsg
Carbon tetrachloride reduced by 85% from 1998–2000 average levels
Methyl chloroform reduced by 30% from 1998–2000 average levels
1 January 2007
*
*
Annex A CFCs reduced by 85% from 1995–1997 average levelsg
Annex B CFCs reduced by 85% from 1998–2000 average levelsh
1 January 2010
&
*
*
HCFCs reduced by 65%
CFCs, halons and carbon tetrachloride phased-out
Methyl chloroform reduced by 70% from 1998–2000 average levels
1 January 2015
&
*
*
HCFCs reduced by 90%
Methyl chloroform phased-out
Methyl bromide phased-out
1 January 2016
1 January 2020
*
&
1 January 2040
*
Freeze of HCFCs at base line figure of year 2015 average levels
HCFCs phased-out allowing for a service tail of up to 0.5% until 2030 for existing
refrigeration and air-conditioning equipment
HCFCs phased-out
Developed countries (&); developing countries (*).
a
Five CFCs in annex A: CFCs 11, 12, 113, 114 and 115.
b
Ten CFCs in annex B: CFCs 13, 111, 112, 211, 212, 213, 214, 215, 216 and 217.
c
Halons 1211, 1301 and 2402.
d
With exemptions for essential uses. Consult the Handbook on Essential Use Nominations prepared by the Technology and Economic Assessment Panel,
1994, UNEP, for more information.
e
A 34 hydrobromofluorocarbons.
f
A 34 hydrochlorofluorocarbons.
g
Calculated level of production of 0.3 kg per capita can also be used for calculation, if lower.
h
Calculated level of production of 0.2 kg per capita can be also be used for calculation, if lower.
240
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
Each CFC refrigerant to be substituted by a single environmentally acceptable product. The rapid expansion of
the refrigeration and air-conditioning industries since
1945 had largely been based on only four major refrigerants, CFC-12, HCFC-22, CFC-11 and R502 (an azeotrope of CFC-115 (CF3CF2Cl) and HCFC-22). The
industry considered that the proliferation of different
refrigerants for the same application would cause confusion by increasing the number of products that a service
engineer would need to carry.
Initially, attention was focused on HFC-134a as a replacement for the major refrigerant CFC-12 used in automobile
air-conditioning systems, domestic fridge–freezers and commercial refrigeration. The single, most important item of
thermodynamic data, and fortunately the one which chemists
traditionally record, is boiling point. HFC-134a boils at
26.4 8C compared to 29.8 8C for CFC-12. Simple theoretical cycle calculations initially suggested that 134a would
be slightly less energy efficient, but this was disproved when
experimental results in optimised systems became available.
The real problem with 134a was its very low miscibility
(<1%, w/w) in the mineral oil lubricants used for CFC-12. In
typical compressor designs refrigerant returning from the
evaporator passes through the oil sump before being sucked
into the compressor. This excellent design ensures efficient
lubrication of the compressor, but 2% of the total oil
charge circulates through the system. The complete miscibility of the oil with the refrigerant ensured that none
accumulated in the refrigeration circuit. Unfortunately with
HFC-134a, reliable return of the lubricant to the sump could
not be guaranteed, with the attendant risk that oil depletion
would cause compressor failure. New oils miscible with 134a
were required and two classes emerged, the polyalkylene
glycols and the polyol esters (POEs). Many compressor
systems contain aluminium alloy components which proved
susceptible to attack by polyalkylene oxides, because the
protective oxide layer was removed. Fortunately, the POEs
proved to be satisfactory providing both good lubrication and
oil return. Their major technical disadvantage is their ability
to absorb typically up to 2000 ppm of water, so special care
has to be taken to prevent moisture ingress which would
cause corrosion and consequent compressor failure.
By the late 1980s HFC-134a had emerged as the preferred
the non-ozone depleting replacement CFC-12 essentially
based upon the consensus of the major refrigerant users, the
refrigerant manufacturers and not least national governments who wanted an effective programme to replace CFCs.
There were, and still are, dissenting opinions that will be
discussed later in this paper.
4. Selecting fluorocarbon replacements
for HCFC refrigerants
By 1990 continuing observations of the Antarctic ozone
hole and increasingly sophisticated atmospheric models
Table 2
Input parameters for cycle calculations
Parameter
Value
Mid-point evaporator temperature (8C)
Mid-point condenser temperature (8C)
Cooling output (kW)
Compressor efficiency
Electric motor efficiency
Parasitic power (fans and controls) (kW)
7
45
10
0.7
0.85
0.8
Table 3
Calculated values of key output parameters
Refrigerant
HCFC-22 30% HFC-32, 23% HFC-32,
70% HFC-134a 25% HFC-125,
52% HFC-134a
(407C)
Evaporator pressure (bar)
5.93
Discharge pressure (bar)
17.9
Discharge temperature (8C) 104.7
COP (system)
2.49
Capacity (kW/m3)
3067
Glide in evaporator (8C)
0
Glide in condenser (8C)
0
5.56
18.1
98.0
2.49
3030
5.0
5.1
6.03
19.3
92.5
2.47
3172
4.8
4.7
made it clear that the CFCs needed to be phased-out
completely, earlier than had been anticipated. Furthermore,
the HCFCs, which had been considered as part of the
long-term solution, also needed to be regulated. The major
HCFC, CHClF2 (HCFC-22) is used extensively in building
air-conditioning systems and has a boiling point of 42 8C.
Although three simple HFCs have low boiling points,
namely CF3CF2H (HFC-125, 48 8C), CF3CH3 (HFC143a, 48 8C) and CH2F2 (HFC-32, 51 8C), there is no
single compound which can provide a direct substitute for
HCFC-22.
To a chemist the ‘‘obvious’’ solution is to mix a high and a
low boiling point HFC, so that the blend has a boiling point
similar to that of HCFC-22. Independent work by several
industrial groups, including the author’s, identified that a
blend containing 70 wt.% HFC-134a and 30 wt.% HFC-32
had thermodynamic properties similar to HCFC-22. Furthermore, simple cycle calculations suggested that its energy
efficiency (coefficient of performance, COP1) and cooling
capacity were close to those of HCFC-22. Table 2 summarises the input parameters for a typical air-conditioning
refrigerant cycle.2 Table 3 gives the values of key output
parameters. Although such calculations cannot fully represent
a real cycle, they provide a useful first screen for comparing
candidate compositions. Clearly this HFC-134a/32 blend has
1
The COP of a unit is defined as the ratio of the cooling duty delivered
to the power input.
2
Cycle calculations reported here were performed using the commercially
available ‘‘CYCLE D’’ modelling programme developed by the National
Institute of Science and Technology (NIST), USA.
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
properties close to that of R22. As formulated, the blend
was also non-flammable. Since HFC-134a was already
being developed as the replacement for CFC-12, it was
clearly attractive commercially for it to also be the main
component of the substitute for the other major refrigerant,
HCFC-22.
However, the proposed blend differed from HCFC-22 in
one important aspect: when it evaporated its boiling point
changed, i.e. it was a ‘‘zeotrope’’. Equipment manufacturers
had a long-standing aversion towards zeotropic refrigerants
because of several anticipated problems.
Differential leakage
Liquid refrigerant in a unit would be richer in 134a than
the blend while the vapour would be richer in 32. If the
unit experienced a liquid leak then the average composition of the blend would change which would both affect
the performance and make topping-up more difficult. If
the original blend were used, then the composition of the
mixture in the unit would drift. In practice this fear proved
to be unfounded. Real leaks do not change the composition of the refrigerant.
Temperature glide
A one-component refrigerant evaporates or condenses
at a constant temperature. A zeotrope, however, evaporates or condenses over a temperature range, which is
known in refrigeration technology as the ‘‘temperature
glide’’. The greater the difference between the boiling
points of the components, the greater the glide. For many
years enthusiastic academics had advocated the use of
zeotropic blends as a way of improving energy efficiency,
for which there was good theoretical thermodynamic
justification. In practice non-equilibrium effects and
poorer heat transfer often wiped-out any potential gains
in efficiency, or required more expensive heat exchangers
to realise the improved performance. Equipment manufacturers were concerned that the same problems would
be experienced in replacing HCFC-22 by a zeotrope. A
further potential consequence of the glide was that the
temperature in the portion of the evaporator immediately
after the expansion device might be below 0 8C, although
the average temperature over the evaporator was higher. If
this happened, ice would form, blocking part of the heat
exchanger surface and thus reducing its efficiency. Fortunately in practice, the glides for the HFC134a/32 blend
were sufficiently small not to cause these problems.
Air-conditioning circuit
An air-conditioning circuit sometimes contains a receiver immediate after the evaporator to prevent slugs of
unevaporated liquid refrigerant from entering the compressor where they could cause a serious damage. However, when using a zeotropic refrigerant the higher boiling
component might accumulate preferentially in the reservoir thus altering the composition of the circulating
refrigerant, which might adversely affect the performance
of the unit.
241
None of these anticipated problems proved to be significant in practice, but the blend was rejected, because it was
capable of generating a flammable vapour under exceptional
circumstances. If an air-conditioning unit is exposed to
winter temperatures of 40 to 20 8C, typically experienced in the northern Great Plains of the USA, then the
lower boiling HCFC-32 can distil preferentially from the
evaporator within the building into the external condenser. In
effect the air-conditioner fractionates the refrigerant. The
vapour in the condenser can become sufficiently rich in
HFC-32 to be flammable.
The flammability hazard was deemed to be unacceptable,
so a new formulation was developed containing HFC-32,
HFC-125 and HFC-134a in the mass ratio 23/25/52. The nonflammable HFC-125 suppressed the flammability of R32,
while still giving thermodynamic properties that were reasonably similar to those of HCFC-22. This HFC-32/125/134a
blend has been assigned the code number 407C3 by American
Society for Heating Refrigeration and Air-conditioning Engineers (ASHRAE4). Its energy efficiency was considered to be
slightly worse than that of the original HFC-32/134a blend,
but the COP values in Table 3 indicate that the effect is likely
to be marginal. The calculated cooling capacity was slightly
higher than of HCFC-22, which was good. Although under
conditions used for the example, the discharge temperature of
the compressed vapour is relatively low, even for HCFC-22,
the even lower temperature calculated for R407C suggests
that under more extreme operating conditions there is little
risk of excessive discharge temperatures.
The major disadvantage with R407C as a direct replacement for HCFC-22 was its higher discharge pressure. Refrigeration engineers normally consider that equipment designed
for HCFC-22 can accommodate, at most, an extra 2 bar of
pressure, a value which R407C attains at a condensing temperature of 55 8C. Although design modifications allow
R407C to be used in new equipment it is not generally
recommended for retrofitting into R22 units already in service.
5. Long-term blends
Once the principle of zeotropic refrigerants had been
accepted then an infinite number of products was in theory
3
The 400 series numbers are reserved for zeotropes. When a new
combination of fluids is first submitted to ASHRAE it is given the next
available number; thus the first combination containing 32/125/134a was
assigned the number 407. To distinguish blends containing the same
components but in different ratios, each specific composition is given an
upper case letter which is assigned in the order that the blends are registered
by ASHRAE; thus R407C was the third HFC-32/125/134a blend to be
registered. The composition of a zeotrope can only be determined from its
refrigerant code number by reference to a list. As with the azeotropes of the
500 series no direct link exists between chemical structures and the number.
4
Although ASHRAE is an American organisation whose membership is
strictly limited to individuals, not industrial corporations, its standards on
refrigerant nomenclature and refrigeration practice are recognised worldwide.
242
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
Table 4
Long-term refrigerant blends based on HFCs
ASHRAE code
Component
Composition (wt.%)
Refrigerant replaced
Application
404A
125/143a/134a
44/52/4
R502
Supermarket
407A
407B
407C
407D
32/125/134a
32/125/134a
32/125/134a
32/125/134a
20/40/40
10/70/20
23/25/52
15/15/70
R502 (CHClF2/CF3CF2Cl)
R502
R502
R502
R500
Supermarket
Supermarket
Supermarket
Industrial
410A
410B
507
508A
32/125
32/125
125/143a
23/116a
50/50
45/55
50/50
39/61
R500 (CCl2F2/CH3CF2H)
HCFC-22
HCFC-22
R502
R503
Air-conditioning
Air-conditioning
Supermarket
Biomedical freezer
508B
23/116
46/54
R503 (CF3H/CF3Cl)
R503
Biomedical freezer
a
PFC-116 is hexafluoroethane.
possible. Not surprisingly therefore, several different products appeared in the market place intended to replace the
same CFC or HCFC refrigerant, a selection of which is listed
in Table 4. Previously the fluorocarbon refrigerant market
was satisfied by two major tonnage products (CFC-12,
HCFC-22), two moderate tonnage products (R502,5 CFC11) and three low tonnage products (R503,6 CClF2CClF2
(CFC-114), CF3Br (BFC-13B1)). Service engineers could
buy CFC-12 as FreonTM 12 from DuPont or as ArctonTM 12
from ICI, knowing they were the same material. Of course
this is also true of the blends in Table 4, but not all blends are
available from all suppliers, because in some cases they are
still restricted by patents and licensing agreements. Several
refrigerants are designed to replace R502, a key supermarket
freezer refrigerant, but it is not acceptable to top-up a unit
containing one product with another intended for the same
application.
Although they contain the same components in different
ratios, R508A and R508B are both azeotropes. This is possible because the azeotropic composition is markedly temperature dependent. The R508A composition was selected
to be azeotropic at 80 8C close to its typical evaporating
temperature in low temperature medical freezers, while
the composition of R508B corresponds to an azeotrope at
40 8C. Although both components of these azeotropes have
high global warming potentials (GWPs) (Table 5) they have
been accepted as long-term replacements for R503 in biomedical freezers offering a high degree of containment and
from which they can recovered efficiently for recycling. By
refrigeration standards, global yearly usage is very small, of
the order of 100 te. Furthermore such freezers are considered
an essential use.
CFC-11 is used in low pressure (<2 bar) chiller airconditioning systems based on centrifugal compressors and
Table 5
Global warming potentials of fluorinated compounds [13]
ASHRAE code
Compound
Estimated
GWPa
atmospheric
(100 year
lifetime (year) integrated
time horizon)
CFCs
CFC-11
CFC-12
CFC-113
CFC-114
CFC-115
CCl3F
CCl2F2
CClF2CCl2F
CClF2CClF2
CF3CF2Cl
50 5
102
85
300
1700
4000
8500
5000
9300
9300
HCFCs
HCFC-22
HCFC-123
HCFC-124
HCFC-141b
HCFC-142b
CHClF2
CF3CHCl2
CF3CHClF
CH3CCl2F
CH3CClF2
13.3
1.4
5.9
9.4
19.5
1500
93
480
630
2000
HFCs
HFC-23
HFC-32
HFC-43-10mee
HFC-125
HFC-134a
HFC-143a
HFC-152a
HFC-227ea
HFC-236fa
HFC-245ca
CHF3
CH2F2
CF3CHFCHFCF2CF3
CF3CF2H
CF3CH2F
CF3CH3
CHF2CH3
CF3CHFCF3
CF3CH2CF3
CHF2CF2CH2F
264
5.6
17.1
32.6
14.6
48.3
1.5
36.5
209
6.6
11700
650
1300
2800
1300
3800
140
2900
6300
560
a
GWP values are referenced to the absolute GWP for CO2 at 100 year
integrated time horizon; typical uncertainty is 35%.
using a cold water circuit to distribute ‘‘coolth’’7 around
large buildings. A successful replacement must satisfy the
low pressure requirement and have a comparable molecular
weight to be compatible with centrifugal compressors.
7
5
An azeotrope of CF3CF2Cl (CFC-115) and HCFC-22.
6
An azeotrope of CFC-12 and CHF2CH3 (HFC-152a).
‘‘Coolth’’ is a term used in refrigeration and air conditioning to mean the
opposite of heat. The temperature of a room is raised by supplying ‘‘heat’’
and cooled by supplying ‘‘coolth’’. It can be defined as ‘‘negative heat’’.
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
FC-1,1,2,2,3-pentafluoropropane (CHF2CF2CH2F, bp 27 8C)
appears to be the single fluid with the closest match in
properties [8,9], but is flammable over a modest range of
concentrations in moist air.
243
In anticipation of the phase-out of HCFCs, formulations
are being developed which contain no chlorinated fluids.
In this case, to ensure good oil return, a small quantity of
hydrocarbon is added which is sufficient to promote oil
return but does not generate a flammable vapour or liquid
even when the zeotrope fractionates during evaporation.
6. Transitional products
6.1. Foaming blowing
Although new refrigeration and air-conditioning equipment now being sold in the developed world contains HFC
refrigerants, or, in the case of European domestic fridge–
freezers, hydrocarbons, a huge number of installed commercial and industrial units still operate using CFCs. In the
USA, and also in Europe up to the end of 2000, this
equipment could be serviced with recycled refrigerants.
However, refrigerant suppliers recognised that as the pool
of recyclable CFCs and HCFCs diminished or recycling was
banned, products would be required that could be retrofitted
into existing systems, which still had many years of useful
service life. The result has been a proliferation of zeotropic
blends aimed at the retrofit market. Table 6 lists some blends
that are being, or have been, offered commercially, but is by
no means comprehensive.
Some blends were originally developed in response to
equipment manufacturers and users customer demands
to eliminate CFCs as soon as possible, even ahead of the
Montreal Protocol requirements. Thus the author, when
working for ICI Klea (now Ineos Fluor), developed R509
in collaboration with Sanyo as a replacement for R502 in
biomedical freezers. A key objective in the development of
these transitional products was that they should be at least
partly miscible with the hydrocarbon lubricants used with
the CFCs being replaced to provide adequate oil return
from the refrigeration system. The inclusion of chlorinecontaining HCFCs in most of the listed formulations ensured
this would happen.
Table 6
Transitional products
ASHRAE
code
Component
Composition
(wt.%)
Refrigerant
replaced
401A
402A
402B
403A
404A
408A
409A
409B
411A
412A
413A
No code
509
123
22/152a/124
125/propane/22
125/propane/22
Propane/22/218
125/143a/134a
125/143a/22
22/124/142b
22/124/142b
Propene/22/152a
22/218/142b
218/iso-butane/134a
125/134a/n-butane
22/218a
CF3CHCl2
53/13/34
60/2/38
38/2/60
5/56/39
44/52/4
7/46/47
60/25/15
65/25/10
1.5/87.5/11
70/5/25
9/3/88
47.5/49/3.5
44/56
–
CFC-12
R502
R502
R502
R502
R502
CFC-12
CFC-12
HCFC-22
R500
CFC-12
HCFC-22
R502
CFC-11
a
PFC-218 is perfluoropropane.
CFC phase-out has had an equally important impact on
the poly-urethane foam used to insulate refrigerators. In the
past, CFC-11 was the universal foam blowing for refrigerant
applications. In the USA it been has replaced by HCFC-141b
(CCl2FCH3), a transitional product which provides an
insulating effect approaching that of CFC-11. In Europe,
however, the strong environmental lobby has influenced
manufacturers to adopt c-pentane as the preferred blowing
agent. In the USA the possible flammability hazard posed
by this hydrocarbon has militated against its use. Clearly
American and European views differ when dealing with
environmental problems. Along with other HCFCs, 141b
will be largely phased-out over the next decade. A possible
replacement is CF3CH2CHF2 (HFC-245fa); but vacuum
panels and aerogels are potential ‘‘not-in-kind’’ alternatives.
7. Other HFCs and hydrofluorocarbon ethers
Although HFC-134a and R407C emerged as the most
important replacements for CFC-12 and HCFC-22, respectively, various alternative fluids were mooted, especially in
the late 1980s and early 1990s. HFC-134 (CHF2CHF2, bp
20 8C) was considered for automobile air-conditioning,
where its critical temperature of 112 8C, 12 8C higher than
that of HFC-134a (101 8C), was seen as advantage since
vehicle air-conditioner condensers operate at temperatures
up to 80 8C. HFC-227ea (CF3CHFCF3, bp 20 8C) was
originally advocated by Hoechst as an alternative to HFC134a. Although it was not accepted as a major replacement
refrigerant, it has emerged as a fire-fighting agent to replace
CF2BrCl (halon 1211) and as a propellant for medical
aerosols.
The American EPA favoured low boiling, partially fluorinated dimethyl ethers, funding academic programmes to synthesise candidates and measure thermodynamic properties.
Of particular interest were CF3OCH3 (E143a, bp 24 8C) and
CF3OCHF2 (E125, bp 37 8C). These compounds appeared
to offer lower GWPs than HFC-134a and HFC-125 and
appeared to be promising refrigerants, either alone, or perhaps
formulated with other fluids [10].
So why was none of these compounds developed further
as replacements for CFC-12 and HCFC-22? Reasons include
the following.
HFC-134, HFC-227ea and E143a have lower refrigeration
capacities than CFC-12 so would need larger compressors.
244
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
This requirement would have a cost penalty, and in the
case of vehicles a size and weight penalty thus increasing
fuel consumption.
For ease of servicing, especially in mobile and packaged
air-conditioning applications, single products, which were
direct replacements for R12 and HCFC-22, were considered important.
In the early 1990s when these alternative compounds were
being mooted, the refrigerant producers had already
committed considerable effort to introducing HFC-134a
as the major replacement refrigerant in order to meet the
deadlines for CFC phase-out set by the Montreal Protocol.
Any delay to consider alternative products would have
meant that CFC-12 would not have been phased-out as
planned.
The synthetic routes used for producing lab samples
of E134a and E125 were not economically viable for
large-scale production processes. Although manufacturing routes for 134a had proved to be difficult, they had
been able to exploit existing technology.
The atmospheric lifetimes of E125 and E134a were lower
than those of HFC-125 and HFC-134a and so had lower
GWPs. In reality this was only a marginal advantage since
most of the global warming contributions of refrigeration
and air-conditioning units were a result of burning
fossil fuel to power them, not from the refrigerant, even
assuming that this was released and not recycled (v.i.).
Environmental lobbyists, especially in Europe, were
advocating the banning of fluorine-containing fluids as
a matter of principle, so choosing fluorine containing
refrigerants with modestly lower GWPs would not have
lessened their opposition.
8. The present state of the ozone layer
The concentrations of stratospheric ozone over much of
the globe are being monitored continuously by the satellitemounted total ozone mapping spectrometer (TOMS). Both
the latest daily readings and historical data from 1980
onwards are readily accessed on the CMDL web-site [11].
Fig. 1a shows the minimum ozone readings over Antarctica
for the period 1980–2000.
Stratospheric ozone concentrations are expressed in Dobson units (DUs).8 The minimum ozone concentration over
the Antarctic occurs in its spring and is generally observed
in October, although it can occur also in late September or
8
The DU is named after Dobson, a pioneer of atmospheric ozone
research in the period 1920–1960. A 1 DU is defined as a 0.01 mm
thickness of ozone at STP. To understand the definition of the DU, imagine
a column covering the land area of France and stretching up into the higher
atmosphere. If all the ozone in the stratospheric region of this column was
compressed to STP and the gas spread evenly over the whole area, then the
thickness of the resulting gas layer expressed in millimetres would be the
average concentration of stratospheric ozone in DUs over France.
early November. Fig. 1a demonstrates that the Antarctic
ozone minimum dropped from about 210 DUs in 1980 to
roughly 90 DUs in late 2000. But the ozone hole was only
discovered in 1984 so how is it possible to provide results
for earlier years? The evidence for the Antarctic ozone
depletion was already present in the pre-1984 TOMS data,
but this was not analysed until after Farman’s team made
their discovery using ground based equipment. Fig. 1b
shows the expansion the area of ozone depletion over the
same period. Clearly Antarctic spring ozone depletion
remains severe.
So are the controls on the emissions of chlorine-containing gases imposed by the Montreal Protocol having any
effect? Fig. 2 shows that the measured concentrations of
chlorine-containing gases in the atmosphere have reached a
maximum and are starting to decline. There can be no doubt
that the controls introduced by the Montreal Protocol are
having the desired effect, but the atmospheric chlorine
concentration is still close to its maximum level so ozone
depletion over the Antarctica is unlikely to improve significantly in the immediate future.
Fig. 3 shows both the historical increase of chlorine and
bromine containing gases and their predicted decline over
the next century. The consensus of scientific opinion is
that the ozone problem has been solved by the world-wide
regulation of CFC and HCFC production and emission
under the terms set by the Montreal Protocol. By 2050
the Antarctic ozone hole is expected to be much less
extensive.
The concentrations of the chlorine-containing gases
HCFCs 141b and 142b, adopted especially in the USA
as transitional products to facilitate the phase-out of
CFCs, are presently increasing (Fig. 4) [11]. However,
their concentrations are only 2% of that of CFC-12 and
will start decreasing following HCFC phase-out over
the next decade. Measurements are made at eight sites
around the world, including the South Pole, which are
distant from major centres of fluorocarbon production
and use. The upper and solid lines in the diagram show
the range of values obtained. The dotted lines show the
average trends in the atmospheric concentrations of the
compounds.
Not surprisingly the concentration of HFC-134a is also
growing rapidly following the start of large-scale manufacture and use in the mid-1990s. Of the HFC-134a emitted
7–20% is converted by atmospheric hydroxyl radicals to
trifluoroacetyl fluoride, which is subsequently hydrolysed to
trifluoroacetic acid. Although the detection of trifluoroacetate in land surface water is therefore not unexpected, it is
remarkable that quantities present already exceed those
estimated for 2010 having taken into account all man-made
sources [12], including compounds such as halothane
(CF3CHBrCl), CFC-114a (CF3CIF2), CFC-115 (CF3CF2Cl)
and HCFC-123 (CF3CHCl2). This suggests that a ‘‘natural’’
source of trifluoroacetate exists [13]. Oceanic concentrations strongly support this view with values of 200 ng/l
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
245
Fig. 1. (a) The ‘‘deepening’’ and (b) the growth of the ozone hole.
in both mid-Atlantic and the southern ocean of Antarctica
at depths down to 4150 m [14], corresponding to more
than 100 mte of trifluoroacetate which far exceeds any historical industrial production of fluorochemical precursors.
Fig. 2. Atmospheric concentrations of two major CFCs [11].
The source of this trifluoroacetate is unknown, although
Harnisch et al. has speculated that it could have a geological
origin [15], but has not presented a chemical mechanism.
Clearly this discovery represents an exciting challenge to
fluorine chemists.
Given that trifluoroacetate is a ‘‘natural’’ product it is
perhaps not surprising that from extensive testing of the
effect of trifluoroacetate on living organisms, it has been
concluded the amounts of this ion generated from the breakdown of HFCs, such as 134a will not adversely affect the
environment. But this is not a justification for the uncontrolled release of these valuable compounds to the environment. The well-established policy of minimising HFC
emissions to the atmosphere, by not using them in nonessential, dispersive applications, preventing leaks and
recycling material recovered from defunct equipment, is
both environmentally responsible and economically sound
practice [11].
246
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
Fig. 3. Halogen loading as equivalent stratospheric chlorine [11].
Fig. 4. Atmospheric concentrations of HFC-134a and three HCFCs [11].
9. The impact of the HFC replacements
on global warming
Around 1990 global warming resulting from the release
of man-made gases became a major environmental issue.
Although the largest contributor is carbon dioxide from
the burning of fossil fuels, it was estimated that CFCs
accounted for 15% of global warming in the early
1980s. Although their effects would obviously disappear,
the question is whether their commercially preferred replacements, the HFCs, would contribute significantly to global
warming. From Table 4 the GWP of HFC-134a relative to
CO2 is 1300 which is only 6.5 times less than that of CFC-12
which it has replaced. Seizing upon the perceived high GWP
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
of HFC-134a, environmental campaigners and some governments have urged that this product and other HFCs
should be regarded as transitional products and that, like
the CFCs, a time-table should also be adopted for their
eventual phase-out. During the negotiations leading to the
Kyoto Treaty, however, a ‘‘basket’’ of green-house gases
was defined that included HFCs as well as CO2, methane,
perfluorocarbons, SF6 and nitrous oxide. Each country
committed to achieving a specific level of total global
warming gas emissions in 2010 based on its emissions in
1992. Flexibility was allowed in the combination of gases
which were emitted to achieve this target; for example, a
country could choose to control all the six types of gases prorata; alternatively it might reduce its CO2 emissions by a
greater extent, but increase its HFC emissions.
Arguing for the phase-out of HFC-134a refrigerant purely
on the basis of its GWP is scientifically simplistic. Fig. 5a
shows the rates of elimination of HFC-134a from the atmosphere relative to carbon dioxide assuming that equal masses
247
of each are emitted at time zero. Whereas essentially all the
134a has been eliminated after 100 years, over 30% of the
carbon dioxide remains after 500 years. Obviously the fossil
fuel derived energy consumed by the refrigerator over
its 20 year lifetime has greater consequences for global
warming than the HFC-134a in its refrigeration circuit.
Fig. 5b demonstrates this very clearly for a domestic refrigerator similar to those currently sold in the USA, which are
insulated by foam blown with CCl2FCH3 (141b).
The vertical axis is a measure of the actual contribution of
the refrigerator to global warming over 500 years which
takes into account not only their GWPs, but also the
quantities of each associated with the appliance. Furthermore, it assumes that the HFC-134a is released at the end of
the 20 year life; in practice this will not happen since all
developed countries have strict regulations requiring the
recover and recycle of HFC refrigerants. Despite biasing
the case against HFC-134a the area under the CO2 curve
is much greater than that under the combined fluorinated
Fig. 5. (a) Elimination of HFC-134a and CO2 from the atmosphere [16]. (b) Total impact of a refrigerator on global warming [16].
248
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
fluids curve, i.e. the two smaller areas above the CO2 curve.
Replacing HFC-134a by lower GWP refrigerant will have
only a small effect on the over-all contribution of the
refrigerator to global warming. Much greater improvements
could be achieved by improving the insulation or increasing
the heat exchanger area to reduce temperature differentials.
Even better, environmentally, would be the use of energy
from non-fossil sources, such as wind generators or solar
cells.
The idea of considering both the direct and the indirect
contributions from the refrigerant agent and the power
generation, respectively, plus the contribution from manufacturing a unit, was developed by the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS)
and the US Department of Energy (DOE). The sum of
these contributions is called the ‘‘total equivalent warming
impact’’ (TEWI) of the technology being considered [16].
The value of the concept lies in its ability to compare, on
a common basis, systems operating on different physical
principles. For example, standard mechanical refrigerators
can be assessed against absorption units in which a heat
source, such as a gas flame, is used to distil ammonia from
water.
TEWI ¼ ½refrigerant contribution converted to CO2
te equivalent
þ ½te CO2 from fossil fuel over lifetime of
cooling unit
þ ½te CO2 equivalent to energy to build unit and
produce the refrigerant fluid
The calculated TEWI is sensitive to assumptions of the
system lifetime, emission losses, and the integration time
horizon chosen to calculate GWP values, as well as the
source and consumption of energy. For example, an electric
refrigerator in France, where 60% of electricity obtained
from nuclear power, will have a lower TEWI than the same
unit in the UK, where only 20% of the electricity is derived
from this source. The TEWI concept includes the energy
required to build a unit although this is typically small
compared with the energy consumed by the unit during
its working life.
10. ‘‘Natural’’ refrigerants
Environmental campaigners strongly support so-called
‘‘natural’’ refrigerants which are listed in Table 7. The
adjective ‘‘natural’’ describes their presence in the environment from biological and geological sources; but the commercially available products sold for refrigeration are
typically derived from non-renewable sources: hydrocarbons from oil cracking; ammonia and CO2 from natural gas.
All these refrigerants were in extensive use until the rapid
growth of the CFCs and HCFCs post 1945. In 1930, 80% of
the British merchant refrigerated shipping fleet relied upon
carbon dioxide because of its relatively low hazards. Ammonia
has remained the refrigerant of choice in large-scale
food freezing plants to the present day. In the 19th century
most small refrigeration units used hydrocarbons. Obviously
there is nothing new about the ‘‘natural’’ refrigerants. They
are readily available commercially and are certainly no
more expensive than HFCs. In equipment design specifically
around their particular thermodynamic properties they can
also achieve acceptable energy efficiencies.
So why did equipment manufacturers not revert to these
compounds when the need to phase-out CFCs and HCFCs
become apparent? In Europe domestic refrigerator manufacturers did adopt hydrocarbons under consumer pressure
following adverse publicity about the high GWP of HFC134a from environmental lobbyists; many freezers contain
i-butane in the refrigeration circuit and have insulating foam
blown with c-pentane. Although the refrigerator/freezer
is the most obvious manifestation of refrigeration to the
general public, this application only accounts for 4% of
total refrigerant use.
Table 7
‘‘Natural’’ refrigerants
Compound
Boiling point (8C)
Hydrocarbons
C2H6
C3H8
i-C4H6
n-C4H10
c-C5H10
88.6
42.1
11.7
0.5
49.5
Inorganics
CO2
NH3
78.5 (sublimation)
33
Air
H2O
100
Hazard
Typical application
Flammability
Flammability
Flammability
Flammability
Flammability
Biomedical freezers
Building air-conditioning
Domestic freezers
Refrigeration, p-styrene foam blowing
Refrigerator foam blowing
Toxicity
Flammability
Mobile air-conditioning
Food processing
Supermarket refrigeration
Absorption refrigerators
Air-conditioning
Absorption chillers
Adsorption air-conditioning
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
The largest single cooling application is automobile
air-conditioning, which in the USA takes 30,000 te of
HFC-134a a year in new vehicles alone. Although various
hydrocarbon compositions have been offered both as retrofit
replacements for CFC-12 and for new vehicles, tests have
shown that if these fluids escaped into the passenger
compartment during an accident and ignited the resulting
explosion would cause serious injury. Not surprisingly,
hydrocarbon refrigerants are banned from mobile air-conditioning units in USA and in some Australian states. Carbon
dioxide is being considered by some auto-manufacturers in
Germany, although the very high pressures require a radical
engineering redesign. Tests suggest that it is not energy
efficient as 134a at high ambient temperatures where airconditioning is especially appreciated. Furthermore, if the
gas entered the cabin its physiological effects, notably
shallow breathing, could be worse than those for HFC-134a.
Regulations typically require that building air-conditioning or refrigeration systems in direct contact with the general
public (e.g. in supermarkets) should not contain hazardous
refrigerants. The problem can be overcome by installing a
secondary circuit containing glycol or calcium chloride
brine to transport the ‘‘coolth’’ from the refrigeration plant
to the building or display units. Such systems have been used
for many years, but involve an extra temperature drop in the
heat exchanger between the primary and secondary circuits.
This means that the evaporator is operating at a lower
temperature than in a simple direct cooling system and thus
the energy efficiency of the system is lower. The net result is
more carbon dioxide generation and a higher TEWI.
Absorption refrigeration or air-conditioning units, which
are driven by the direct application of a heat source, are
sometimes pushed as a more environmentally acceptable
system. Two technologies exist: (1) the evaporation of
ammonia from water; and (2) water from lithium bromide
solution. The former is often used in the ‘‘minibar’’ refrigerators in hotel rooms because of its quiet operation. The
latter is used for providing chilled water to air-condition
buildings. Absorption units are based on intrinsically
inefficient thermodynamic cycles although it is sometimes
assumed, wrongly, that using a direct source of heat avoids
the fundamental thermodynamic inefficiency in a power
station. However, absorption units can be environmentally
attractive in niche applications where there is an otherwise
useless source of low temperature heat, or a ‘‘natural’’
source such as solar or geothermal.
Although rapid and complete replacement of HFCs with
natural refrigerants or other refrigeration technologies is
strongly advocated by environmental activists, the scientific
case for doing so is debatable. In the context of reducing
global warming the real target must be the reduction of
the fossil fuel derived-energy consumed by refrigerators
and air-conditioners. Merely replacing HFCs with natural
refrigerants will have little impact or in some cases
could increase global warming. It could also be counterproductive, because it would divert key technical expertise
249
from making refrigeration and air-conditioning units more
energy efficient.
11. Conclusions
In this paper I have described the factors which have
influenced the selection of the HFCs as the major replacements for the CFCs and HCFCs especially in cooling
applications. Atmospheric concentrations of major CFCs
appear to have stopped increasing and are expected to
decline within the next decade. Models suggest that the
annual Antarctic ozone hole will also start to diminish and
by 2050 will have largely disappeared. In answering the
question posed in the title of this paper, I conclude that we
have met the challenge. We depend crucially upon refrigeration for the safe storage and distribution of our foodstuffs,
for the preservation of vaccines and drugs, as well as for the
comfort afforded by air-conditioning. The CFCs have been
replaced by safe, efficient HFC refrigerants in a transition
that has caused no disruption to our way of life. To move
from the position in 1986 when CFC-12 was the major
refrigerant to 1996 when the developed world had essentially stopped production and replaced it by HFC-134a has
been a remarkable achievement. The dialogue between the
refrigerant producers and refrigeration equipment industry
identified appropriate CFC and HCFC replacements; collaboration between refrigerant producers themselves ensured
the efficient generation of key toxicity and environmental
data without unnecessary duplication of effort. Producers
competed to introduce HFCs into the market place, which
ensured that market forces drove down prices, especially
of HFC-134a. Confidence to invest in expensive new
plants based on innovative technologies was provided by
a strong global regulatory framework provided by the
Montreal Protocol. Of course hitches and misunderstandings
occurred; this was to be expected in a complex world-wide
programme. A significant problem was the stock-piling of
CFCs prior to phase-out in the USA and Europe and the
smuggling of CFCs from plants in the developing world.
Consequently the market for HFC-134a grew more slowly
than anticipated; from 1994 to 1998 the installed capacity
was greater than demand leading to prices which were too
low to provide an adequate return on the newly invested
capital.
The next substantial landmark is the reduction of HCFC
production in 2004. HCFC-22 will be replaced by various
refrigerant blends based on HFC-134a, 125, and 32, especially R407C described above. Since this change has been
anticipated for over 5 years, refrigerant companies have
been able to plan their investments which are now being
publicly announced; for example, Ineos Fluor (originally the
ICI Klea Business) has indicated that it had commenced
HFC-125 production in early 2001. The phase-out of
remaining HCFC production in accordance with the Montreal Protocol can be assured.
250
R.L. Powell / Journal of Fluorine Chemistry 114 (2002) 237–250
In the author’s view the phase-out of HFCs is not justified
on scientific grounds; improvements in the energy efficiency
of refrigeration and air-conditioning units and a move to
non-fossil energy sources would have greater impact on
reducing global warming. Most importantly, replacing HFCs
with technologies that on a TEWI basis produce more global
warming is illogical. Although under pressure from environmental activists some governments accept that HFCs should
be phased-out in the longer term, none has enacted legislation
to ensure that this occurs in the immediate future. HFCs are
still seen as the most effective method of eliminating chlorine-containing refrigerants as quickly as possible while
maintaining the low hazard, efficient and affordable cooling
systems on which our technological society depends.
For fluorine chemists a stimulating area of future research
has emerged from the CFC/HCFC replacement programme,
i.e. the remarkable discovery that far more trifluoroacetate
exists in the environment, especially the oceans, than be
accounted for by the total contribution of all man-made
sources from the beginning of the fluorocarbon production
to the present day. Fluoro-organic chemistry has sometimes
been described as an ‘‘unnatural’’ chemistry; perhaps we
need to modify our views?
Acknowledgements
A.A. Lindley (Ineos Fluor) for discussions on the Montreal
Protocol and related matters. A. McCulloch for discussions
on the environmental impact of HFCs, the ozone hole and the
occurrence of trifluoroacetate in the environment.
References
[1] J.E. Lovelock, Nature 230 (1974) 379.
[2] J.E. Lovelock, R.J. Maggs, E.R. Allard, Anal. Chem. 43 (1971) 1962.
[3] J.E. Lovelock, R.J. Maggs, R.J. Wade, Nature 241 (1973) 194.
[4] M.J. Molina, F.S. Rowland, Nature 249 (1974) 810.
[5] A. McCulloch, R.L. Powell, in: R.E. Banks (Ed.), Fluorine
Chemistry at the Millennium, Elsevier, Oxford, 2000, pp. 357–360.
[6] J.C. Farman, B.G. Gardiner, J.D. Shanklin, Nature 315 (1985)
207.
[7] The Montreal Protocol is revised approximately every 2 years, so
the best up-to-date source of information is the web-site of the
United Nations Environmental Program Ozone Secretariat: http://
www.unep.ch/ozone/index-en.shtml.
[8] S. Corr, J.D. Morrison, F.T. Murphy, R.L. Powell, Developing the
hydrofluorocarbon range: fluids for centrifugal compressors, in:
International Institute of Refrigeration (IIR), Proceedings of the 19th
International Congress of Refrigeration, Vol. IVa, Paris, France, July
1995, pp. 131–138.
[9] P.R. Glamm, E.F. Keuper, F.B. Hamm, Evaluation of HFC-245ca for
commercial use in low pressure chillers, Report DOE/CE/23810-67,
Air-Conditioning and Refrigeration Technology Institute (ARTI),
Arlington, VA, March 1996.
[10] J.C. Bare, in: Proceedings of the International Conference on CFC
and Halon Replacements, Baltimore, MY, 3–5 December 1991,
p. 418.
[11] The information in this section has been abstracted from the Climate
Monitoring and Diagnosis Laboratory (CMDL) web-site (http://
www.cmdl.noaa.gov). CMDL, which is part of the American
National Oceanic and Atmospheric Administration (NOAA), provides both a daily up-date and historical records of stratospheric
ozone levels over much of the globe. CMDL also maintains the sites
around the world which monitor the atmospheric levels of CFCs,
HCFCs and HFCs, reported in this section.
[12] J.C. Boutonnet, P. Bringham, D. Calamari, C. De Rooij, J. Franklin,
T. Kawano, J.M. Libre, A. McCulloch, G. Malinverno, J.M. Ocom,
G.M. Rusch, K. Smythe, I. Sobolev, R. Thompson, J.M. Tiedije,
Hum. Ecol. Risk Assess. 5 (1999) 59–124.
[13] A. Jordan, H. Frank, Environ. Sci. Technol. 33 (1999) 522–527.
[14] E.H. Christoph, H. Frank, Oceanic distribution of trifluoroacetic
acid, in: Proceedings of the Conference of Haloacetic Acids and
Shortchain Halocarbons: Sources and Fate in the Environment,
Toronto, Canada, 27–29 August 2000.
[15] J. Harnisch, M. Frische, R. Borchers, A. Eisenhauer, A. Jordan,
Geophys. Res. Lett. 27 (2000) 1887–1890.
[16] Based on data published by the Alternative Fluorocarbon Environmental Acceptability Study (AFEAS) web-site: http://www.afeas.org.