Transcript Hydro Fluorinated Ethers as replacements for Hyd

Hydro Fluorinated Ethers as
replacements for ChloroFluorinated Carbons
Chemistry 671
15 November, 2011
Richard Madden
Flourinella
Flourinella and her evil sisters
Chlora and Broma
Apologies to Walt Disney
Fun Facts about Fluorine
• Fluorine is in Group 17, Period 2 of the Periodic Table with an
atomic number of 9 and an atomic mass of 18.998 amu.
Fun Facts about Fluorine
• Fluorine is in Group 17, Period 2 of the Periodic Table with an
atomic number of 9 and an atomic mass of 18.998 amu.
• Fluorine is the most electro-negative element (3.98 on the Pauling
Scale of Electro-negativity)
Fun Facts about Fluorine
• Fluorine is in Group 17, Period 2 of the Periodic Table with an
atomic number of 9 and an atomic mass of 18.998 amu.
• Fluorine is the most electro-negative element (3.98 on the
Pauling Scale of Electro-negativity)
• It’s Standard State is a gas (298 K) with a boiling point of
85.03 K (-188.12˚C)
Fun Facts about Fluorine
• Fluorine is in Group Periodic Table with an atomic number of 9 and
an atomic mass of 18.998 amu.
• Fluorine is the most electro-negative element (3.98 on the
Pauling Scale of Electro-negativity)
• It’s Standard State is a gas (298 K) with a boiling point of
85.03 K (-188.12˚C)
• It has a C-F bond enthalpy of 552 KJ/Mol.
Fun Facts about Fluorine
• Fluorine is in Group Periodic Table with an atomic number of 9 and
an atomic mass of 18.998 amu.
• Fluorine is the most electro-negative element (3.98 on the
Pauling Scale of Electro-negativity)
• It’s Standard State is a gas (298 K) with a boiling point of
85.03 K (-188.12˚C)
• It has a C-F bond enthalpy of 552 KJ/Mol.
• Fluorine has a van der Waal’s radius of 132.3 pm.
(H=120 pm)
A Brief History of CFC’s
• Fluorine was first described in 1529. It was used in the form of
Fluorspar to remove impurities during metal smelting. Derived from
the Latin word Fluo, meaning “to flow”.
• The electrolytic isolation of Fluorine was accomplished in 1886 by
Henri Moissan in a process still used commercially today. Moissan
received the Nobel Prize in Chemistry for this process in 1906.
• Belgian scientist Frederick Swarts pioneered the synthesis of CFC’s
in the 1890’s. The process was improved by Thomas Midgley Jr.
while working for DuPont in 1928.
Ozone is formed by O2 reacting with atomic oxygen in the stratosphere
(Dissociation energy of O2 bonds supplied by UV radiation)
Problems of Existing
Compounds
Catalytic Ozone Destruction by
ChlorofluoroCarbons
Atomic Chlorine is an efficient X catalyst in the
destruction of Ozone;
Comparison of the Montreal Protocol and United States Phaseout
Schedules
Montreal Protocol
United States
Year to be
Implement
ed
% Reduction in Consumption and
Production, Using the Cap as a
Baseline
Year to be
Implement
ed
Implementation of HCFC Phaseout through Clean Air Act Regulations
2004
35.0%
2003
No production and no importing of HCFC-141b
2010
75.0%
2010
No production and no importing of HCFC-142b and HCFC-22, except for use in
equipment manufactured before 1/1/2010 (so no production or importing for
NEW equipment that uses these compounds)
2015
90.0%
2015
No production and no importing of any HCFCs, except for use as refrigerants in
equipment manufactured before 1/1/2020
2020
99.5%
2020
No production and no importing of HCFC-142b and HCFC-22
2030
100.0%
2030
No production and no importing of any HCFCs
EPA Regulations, Sections 601-607 of the Clean Air Act
Hydro ChlorofluoroCarbons
Hydro Chloroflouro Carbons (HCFC’s)
have distinct advantages over CFC’s.
Hydrogen abstraction of HCFC’s leads to
much shorter Atmospheric lifetimes. Thus,
these compounds are far less likely to
migrate to the stratosphere.
Direct Global Warming Potentials (mass basis) relative to carbon dioxide (for gases for which the lifetimes have been adequately
characterised). Data from IPCC TAR 2001
Gas
Lifetime (years)
Ozone
depletion
potential
(ODP)
Global Warming Potential
Time horizon
20 years
Carbon dioxide
CO2
Methane
CH4
12.0*
Nitrous oxide
N2O
114*
CFC-11
CCl3F
45
1.0
CFC-12
CCl2F2
100
0.82
CFC-13
CClF3
100 years
1
1
62
23
275
296
6300
4600
10200
10600
640
10000
14000
700
210
4800
1700
390
120
9400
12000
Chlorofluorocarbons
Hydrochlorofluorocarbons
HCFC-21
CHCl2F
2.0
HCFC-22
CHClF2
11.9
0.04
HCFC-123
CF3CHCl2
1.4
0.014
HFC-23
CHF3
260
<0.0004
HFC-32
CH2F2
5.0
1800
550
HFC-41
CH3F
2.6
330
97
Hydrofluorocarbons
* The values for CH4 and N2O are adjustment times including emission feedbacks on lifetimes.
Ozone depletion potentials are normalized model results from the WMO Scientific Assessment of ozone depletion in 1994.
Applications and replacements for CFCs
Application
Previously used CFC
Replacement
Refrigeration &
air-conditioning
CFC-12 (CCl2F2); CFC-11(CCl3F); CFC-13(CClF3); HCFC22 (CHClF2); CFC-113 (Cl2FCCClF2); CFC-114
(CClF2CClF2); CFC-115 (CF3CClF2);
HFC-23 (CHF3); HFC-134a (CF3CFH2); HFC-507 (a 1:1 azeotropic
mixture of HFC 125 (CF3CHF2) and HFC-143a (CF3CH3)); HFC 410 (a 1:1
azeotropic mixture of HFC-32 (CF2H2) and HFC-125 (CF3CF2H))
Propellants in
medicinal
aerosols
CFC-114 (CClF2CClF2)
HFC-134a (CF3CFH2); HFC-227ea (CF3CHFCF3)
Blowing agents
for foams
CFC-11 (CCl3F); CFC 113 (Cl2FCCClF2); HCFC-141b
(CCl2FCH3)
HFC-245fa (CF3CH2CHF2); HFC-365 mfc (CF3CH2CF2CH3)
Solvents,
degreasing
agents, cleaning
agents
CFC-11 (CCl3F); CFC-113 (CCl2FCClF2)
None
Problem Solved???
Both CFC’s and HCFC’s are potent Green
House Gases. They Absorb IR radiation
between 8 and 13 m.
Nations to ramp up phaseout of ozone-killers
200 nations agree to speed elimination of HCFCs, major greenhouse gas
TORONTO — Governments of almost 200 countries have agreed to
speed the elimination of a major greenhouse gas that depletes ozone,
U.N. and Canadian officials said Saturday, describing a deal they said
was a significant step toward fighting global warming.
The agreement reached Friday night will accelerate a treaty to freeze
and phase out hydrochlorofluorocarbons (HCFCs) which are used in
home appliances, some refrigerators, hair sprays and air conditioners,
said Nick Nuttall, spokesman for the United Nations Environment
Program.
9/23/2007
Nations to ramp up phaseout of ozone-killers
200 nations agree to speed elimination of HCFCs, major greenhouse gas
TORONTO — Governments of almost 200 countries have agreed to
speed the elimination of a major greenhouse gas that depletes ozone,
U.N. and Canadian officials said Saturday, describing a deal they said
was a significant step toward fighting global warming.
The agreement reached Friday night will accelerate a treaty to freeze
and phase out hydrochlorofluorocarbons (HCFCs) which are used in
home appliances, some refrigerators, hair sprays and air conditioners,
said Nick Nuttall, spokesman for the United Nations Environment
Program.
9/23/2007
Hydro Fluorinated Ethers
Atmospheric Oxidation of HCFC-123
Despite Advantages, HFE’s are still
relatively unknown.
• There is growing concern about the
atmospheric conversion of HFE’s into
Trifluoro Acetic Acid.
Compounds known to produce TFA (CF3C(O)OH) in the atmosphere.
Compound
Molecular
weight
Common name
Molar CF C(O)OH Atmospheric
yield
lifetime
CF CHClBr
197.5
Halothane
0.6
1.2 years [1]
CF CHClOCHF
184.5
Isoflurane
0.6
5 years [2]
CF CHCl
153
HCFC-123
0.6
1.5 years [3]
CF CHFCl
136.5
HCFC-124
1.0
6.0 years [3]
CF CH F
102
HFC-134a
0.13
14.6 years [4]
170
HFC-227ea
1.0
36.5 years [4]
3
3
2
3
2
3
3
2
CF CHFCF
3
3
3
[1] Orkin and Khamagonov (1993); [2] Brown et al. (1989); [3] WMO (1989); [4] IPCC (1996).
Oxidation is initiated by reaction with OH radicals giving a halogenated alkyl
radical which adds O2 to give the corresponding peroxy radical (RO2). Peroxy
radicals react with three important trace species in the atmosphere: NO, NO2,
and HO2 radicals. Reactions with HO2 and NO2 delay, but do not prevent, the
conversion of peroxy (CF3CXYO2) into alkoxy (CF3CXYO) radicals. Reactions of
haloperoxy radicals with NO are rapid and give the alkoxy radical with essentially
100% yield. The atmospheric fate of the alkoxy radical, CF3CXYO, is either
decomposition or reaction with O2. Decomposition occurs by C-C bond fission, or
by the elimination of a Br, Cl, or CF3 group. The atmospheric fate of CF3C(O)X
(X=F or Cl) is dominated by incorporation into rain-cloud-sea water followed by
rapid hydrolysis to trifluoroacetic acid. Photolysis is a competing loss mechanism
for CF3C(O)Cl and limits its conversion into CF3C(O)OH to 60% (Cox et al.,
1995). There are no competing loss processes for CF3C(O)F; it is converted
entirely into CF3C(O)OH. Although CF3C(O)OH is produced in aqueous phase
chemistry, is highly soluble and partitions into the water phase (Bowden et al.,
1996), the evaporation of cloud droplets can transfer CF3C(O)OH to the gas
phase where it can react with OH radicals. However, this reaction is slow (Carr et
al., 1994; Møgelberg et al., 1994) and is only a minor (<5%, Kanakidou et al.,
1995) loss of CF3C(O)OH. The main atmospheric fate of CF3C(O)OH is rain-out
to the surface.
The End
Thank You!