United States
Environmental Protection
Agency
National Kisk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-95/113 February 1996
& EPA Project Summary
New Chemical Alternatives for the
Protection of Stratospheric Ozone
Darryl D. DesMarteau and Adolph L. Beyerlein
Chlorofluorocarbons (CFCs) and their
brominated analogs (halons) are rec-
ognized as potent contributors to deple-
tion of the Earth's stratospheric ozone
layer. By international agreement, such
chemicals are to be phased out of the
worldwide market. Additionally, certain
partially halogenated CFCs (or
hydrochlorofluorocarbons, HCFCs)
have likewise been recognized as
stratospheric ozone depleters and are
also to be phased out of production
by developed countries in a step-wise
progression over the period 1996 to
2030.
Because of the enormous commer-
cial importance of the CFCs, HCFCs,
and halons, and because few chemi-
cals were readily available or had been
proven acceptable for use in the nu-
merous applications in which the
ozone-depleting substances were em-
ployed, the U. S. Environmental Pro-
tection Agency and the Electric Power
Research Institute sponsored a study
of additional potential alternative chemi-
cals.
This study focused on the investiga-
tion of fluorinated derivatives of pro-
pane and butane to determine if syn-
thesis routes of such compounds were
feasible and economical, and to mea-
sure the physical properties needed to
evaluate the compounds as alterna-
tives. This work resulted in the investi-
gation of 25 compounds including 15
hydrofluorocarbons (MFCs), 9 HCFCs,
and 1 hydrofluoroether (HFE). Several
of the compounds studied had not been
previously synthesized and, for many
of those which had been reported in
the literature, this study resulted in im-
proved synthesis methods. Also, most
compounds which had a prior litera-
ture reference had only a boiling point
measurement. This study, in addition
to the synthesis effort, resulted in a
sizeable body of thermophysical prop-
erty data for each chemical.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Twenty-four fluorinated propane and bu-
tane derivatives and one fluorinated ether
were evaluated as possible alternatives for
CFCs and long-lived HCFCs. Boiling points
for these chemicals range from -34.6 to
76.7°C. Therefore, these chemicals pro-
vide potential alternatives for a broad
range of applications, e.g., as refriger-
ants, foam blowing agents, and solvents.
Emphasis is on hydrogen-containing com-
pounds that are expected to have finite
atmospheric lifetimes which reduce their
global warming potential. Sixteen of the
chemicals investigated contain no chlo-
rine or bromine and therefore have zero
ozone depletion potential. The remaining
nine chlorine-containing chemicals were
selected for investigation before regula-
tory restrictions were imposed on HCFCs.
Nevertheless, the low chlorine content of
-------
the nine HCFCs studied, coupled with a
finite atmospheric lifetime, may in some
cases yield an alternative with a negligible
ozone depletion potential.
Selection and evaluation of the com-
pounds as alternatives require: (1) a knowl-
edge of appropriate physical properties
and (2) possible synthesis routes. Both of
these requirements were investigated in
this research. This study emphasized syn-
thesis routes using relatively inexpensive
commercially available starting materials
and established synthesis procedures
(chlorination, hydrogenation, and addition
of hydrogen fluoride) which are carried
out industrially. This is important in order
for a chemical to be an economically vi-
able alternative for other than a small spe-
cialty market.
Experimental Procedure
Except for one hydrofluoroether (HFE-
125), which was obtained commercially
with 98% purity and then repurified, all
samples employed for property measure-
ments were synthesized with at least
99.5% purity. Synthesized chemicals were
identified and their purity checked by a
combination of nuclear magnetic reso-
nance spectrometry, high pressure Fou-
rier transform infrared spectrometry, gas
chromatography, and mass spectrometry.
Melting point, boiling point, vapor pres-
sures below the boiling point, critical tem-
perature, critical density, liquid densities,
and heat of vaporization at the boiling
point were measured for all 25 compounds.
For four compounds (HFE-125, HFC-
227ea, HFC236ea, and HFC-245cb), the
vapor pressure was measured as a func-
tion of temperature to within 1% accuracy
from below the boiling point to the critical
temperature.
Vapor density in the liquid-vapor coex-
istence region and vapor pressure between
the boiling point and the critical point were
estimated by a modified corresponding
states technique. The reference fluid for
the modified corresponding states calcu-
lations was commercially available HFC-
134a (1,1,1,2-tetrafluoroethane), and the
equation of state used for the reference
fluid was the modified Benedict-Webb-
Rubin equation. Heats of vaporization be-
tween the boiling point and critical point
were calculated from the heat of vaporiza-
tion at the boiling point, the boiling point
temperature, and the critical temperature.
Ideal gas heat capacities and vapor-phase
thermal conductivities were estimated by
functional group additivity methods.
Results
Table 1 lists the 25 compounds investi-
gated by ASHRAE (American Society of
Heating, Refrigerating and Air-Condition-
ing Engineers) refrigerant code designa-
tion and by chemical formula.
Table 1. Compounds Investigated by ASHRAE
Refrigerant Designation and Chemical Formula
Compound
(ASHRAE Code)
HFE-125
HFC-227ea
HFC-227ca
HFC-236fa
HFC-236ea
HFC-236cb
HFC-236ca
HFC-245fa
HFC-245ca
HFC-245cb
HFC-254cb
HFC-329ccb
HFC-338eea
HFC-338cca
HFC-338ccb
HFC-347ccd
HCFC-225ba
HCFC-225da
HCFC-226da
HCFC-226ea
HCFC-234da
HCFC-235ca
HCFC-243da
HCFC-244ca
cy-HCFC-326d
Chemical
Formula
CF3OCF2H
CF3CHFCF3
CF3CF2CF2H
CF3CH2CF3
CF3CHFCF2H
CF3CF2CFH2
CF/YCF2CF2H
CF3CH2CF2H
CHF2CF2CFH2
CF3CF2CH3
CF2HCF2CH3
CF3CF2CF2CF/Y
CF3CFHCFHCF3
CHF2CF2CF2CF/Y
CF3CF2CF2CFH2
CF3CF2CF2CH3
CF3CFCICFHCI
CF3CHCICF2CI
CF3CHCICF3
CF3CHFCF2CI
CF3CHCICFHCI
CF3CF2CH2CI
CF3CHCICH2CI
CF//CF2CH2C/
cy-(CFJ3CHCI
Table 2 lists the 25 compounds studied
along with their boiling point (Tb), melting
point (TJ, heat of vaporization at the boil-
ing point (AH ), critical temperature (Tc),
critical pressure (Pc), critical density (dc),
and liquid heat capacity at 40°C (Cpl).
Conclusions
From the data acquired in this study, it
appears that several of the chemicals syn-
thesized are worthy of consideration as
alternatives to the ozone-depleting CFCs
and HCFCs. Table 3 presents selected
apparent best candidate alternatives from
this study based on a comparison of their
thermophysical properties with those of
commercially important CFCs and HCFCs
and the fact that these candidates have
zero ozone depletion potentials. Also, pref-
erence was given to fluorinated propanes
over fluorinated butanes on the premise
that the latter would likely be more expen-
sive to produce (cost generally correlates
with total fluorine content) and that, for
insulation foam production, the butane de-
rivatives would likely have higher vapor
thermal conductivities than the propane
derivatives. These presumptions are some-
what tenuous, however, and the possibil-
ity that certain of the fluorinated butanes
may be excellent candidates should not
be discounted.
No fluorinated propane derivatives with
as low a boiling point as that of CFC-12
(dichlorodifluoromethane, Tb = -29.8°C)
were found. After some searching, HFC-
245cb was synthesized with a boiling point
of -18.3°C. Its critical temperature of
108.5°C compares well with the critical
temperature of CFC-12 (112°C). There-
fore, HFC-245cb might be an alternative
for CFC-12 for some applications as would
HFC-227ca and -227ea with boiling points
of-16.3 and -18.3°C, and critical tempera-
tures of 106.3 and 102.8°C, respectively.
HFE-125, with a boiling point of -34.6°C
and critical temperature of 80.7°C, appears
to be the best candidate alternative for
CFC-115( 1,1,1,2,2-pentafluorochloroethane,
Tb = -39.2°C, Tc = 79.9°C) and HCFC-22
(difluorochloromethane, Tb = -40.6°C, T =
96.15°C).
HFC-245ca and -245fa with boiling
points of 25.0 and 15.3°C and critical
temperatures of 178.4 and 157.5°C, re-
spectively, are promising candidates to
replace CFC-11 (fluorotrichloromethane,
T = 23.8°C, T = 198.1°C), HCFC-123
(1,1,1-trifluoro-2,2-dichloroethane, T =
27.9°C, Tc = 183.8°C), and HCFC-141b
(1-fluoro-1,1-dichloroethane, Tb = 32.2°C,
Tc = 204.2°C) as a refrigerant in low pres-
sure chillers and/or as a blowing agent in
the manufacture of polyisocyanurate in-
sulation foam. All HFC-245 isomers pos-
sess a hydrogen content sufficient to pos-
sibly render them borderline flammable.
Therefore, the flammabilities of these
chemicals should be evaluated.
A number of CFC-114 (1,1,2,2,-
tetrafluoro-1,2,-dichloroethane, Tb = 3.7°C,
Tc = 145.7°C) alternatives are possible
from the chemicals synthesized. HFCs-
236ea, -236fa, and -236cb with boiling
points of 6.5, -1.1, and -1.4°C, respec-
tively, and HFC-254cb with a boiling point
of -0.8°C are especially attractive. How-
ever, the relatively high hydrogen-to-fluo-
rine atom ratio of HFC-254cb poses a
flammability concern for this compound.
-------
Table 2. Boiling Point, Melting Point, Critical Properties, Heat of Vaporization at the Boiling Point, and
Liquid-Phase Heat Capacity for the 25 Compounds Studied.
Compound
HFE-125
HFC-227ea
HFC-227ca
HFC-236fa
HFC-236ea
HFC-236cb
HFC-236ca
HFC-245fa
HFC-245ca
HFC-245cb
HFC-254cb
HFC-329ccb
HFC-338eea
HFC-338cca
HFC-338ccb
HFC-347ccd
HCFC-226da
HCFC-226ea
HCFC-235ca
HCFC-244ca
HCFC-225da
HCFC-225ba
HCFC-234da
HCFC-243da
cy-HCFC-326d
Tb(°C)
-34.6
-18.3
-16.3
-1.1
6.5
-1.4
12.6
15.3
25.0
-18.3
-0.8
15.1
25.4
42.5
27.8
15.1
14.1
17.6
28.1
54.8
50.8
51.9
70.1
76.7
38.1
Tm(°C)
-156.1
-126.8
-140.3
-94.2
-146.1
-105.4
-123.3
-102.1
-73.4
-81.1
-121.1
-122.3
-91.5
-91.0
-119.4
-124.9
-119.6
-134.0
-85.0
-101.8
-130.3
-132.7
-98.0
-71.6
-94.8
(kJ/mof)
21.92
22.29
23.69
25.66
26.83
25.25
26.59
27.96
29.21
23.59
24.86
26.71
27.79
31.13
26.36
25.82
24.64
26.26
27.57
31.07
25.89
29.38
31.70
30.86
28.69
TC(°C)
80.7
102.8
106.3
130.6
141.1
130.1
155.2
157.5
178.4
108.5
146.1
140.2
148.5
186.4
160.5
144.2
158.2
158.3
170.3
221.0
206.2
212.9
242.5
251.9
196.9
Pc (kPa)
3253
2943
2874
3177
3533
3118
3405
3623
3855
3264
3753
2391
2475
2792
2552
2570
3024
2939
3084
3714
3006
3074
3353
3496
2749
dc (kg/m3)
584
580
594
556
571
545
558
529
529
499
467
600
581
578
562
532
591
584
550
525
589
586
552
514
515
cpl
(kJ/kg °C)
1.327
1.258
1.254
1.371
1.304
1.438
NA
1.422
1.454
1.457
1.590
1.223
NA
1.333
1.342
1.383
1.207
1.205
1.275
1.160
1.087
1.087
1.176
1.234
1.158
NA = not available
Table 3. Selected Possible Alternatives for Commercially Important CFCs and HCFCs
CFCorHCFC
To Be Replaced
ASHRAE Code
of Alternative
Chemical Formula
of Alternative
Chemical Name
of Alternative
CFC-11,
HCFC-123,
HCFC-141b
CFC-12
CFC-114
CFC-115,
HCFC-22
HFC-245ca
HFC-245fa
HFC-227ea
HFC-227ca
HFC-245cb
HFC-236ea
HFC-236fa
HFC-236cb
HFC-254cb
HFE-125
CF/YCF2CFH2
CF3CH2CF2H
CF3CHFCF3
CF3CF2CF/y
CF3CF2CH3
CF3CHFCF2H
CF3CH2CF3
CF3CF2CFH2
CF/YCF2CH3
CFjOCF/Y
1,1,2,2,3-pentafluoropropane
1,1,1,3,3-pentafluoropropane
1,1,1,2,3,3,3-heptafluoropropane
1,1,1,2,2,3,3-heptafluoropropane
1,1,1,2,2-pentafluoropropane
1,1,1,2,3,3-hexafluoropropane
1,1,1,2,2,2-hexafluoropropane
1,1,1,2,2,3-hexafluoropropane
1,1,2,2-tetrafluoropropane
pentafluorodimethylether
-------
D. DesMarteau and A. Beyerlein are with Clemson University, Clemson, SC 29634.
N. Dean Smith is the EPA Project Officer (see below).
The complete report, entitled "New Chemical Alternatives for the Protectin of
Stratospheric Ozone," (Order No. PB95-260220; Cost $27.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
National Risk Management Research Laboratory (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-95/113
------- |