hydro fluorinated ethers as replacements for chloro- fluorinated carbons chemistry 671 15 november,...

Hydro Fluorinated Ethers as replacements for Chloro-

Fluorinated Carbons

Chemistry 67115 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 Implemented

% Reduction in Consumption and Production, Using the Cap as a Baseline

Year to be Implemented

Implementation of HCFC Phaseout through Clean Air Act Regulations

2004 35.0% 2003 No production and no importing of HCFC-141b

2010 75.0% 2010No 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% 2015No 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) Ozonedepletionpotential(ODP)

Global Warming PotentialTime horizon

    20 years 100 years

Carbon dioxide CO2     1 1

Methane CH4 12.0*   62 23

Nitrous oxide N2O 114*   275 296

Chlorofluorocarbons

CFC-11 CCl3F 45 1.0 6300 4600

CFC-12 CCl2F2 100 0.82 10200 10600

CFC-13 CClF3 640   10000 14000

Hydrochlorofluorocarbons

HCFC-21 CHCl2F 2.0   700 210

HCFC-22 CHClF2 11.9 0.04 4800 1700

HCFC-123 CF3CHCl2 1.4 0.014 390 120

Hydrofluorocarbons

HFC-23 CHF3 260 <0.0004 9400 12000

HFC-32 CH2F2 5.0   1800 550

HFC-41 CH3F 2.6   330 97

* 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); HCFC-

22 (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 phase-out of ozone-killers

200 nations agree to speed elimination of HCFCs, major greenhouse gas

9/23/2007

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.

Nations to ramp up phase-out of ozone-killers

200 nations agree to speed elimination of HCFCs, major greenhouse gas

9/23/2007

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.

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 CF3C(O)OH yield 

Atmospheric lifetime 

CF3CHClBr  197.5  Halothane  0.6  1.2 years [1] 

CF3CHClOCHF2 184.5  Isoflurane  0.6  5 years [2] 

CF3CHCl2 153  HCFC-123  0.6  1.5 years [3] 

CF3CHFCl  136.5  HCFC-124  1.0  6.0 years [3] 

CF3CH2F  102  HFC-134a  0.13  14.6 years [4] 

CF3CHFCF3 170  HFC-227ea  1.0  36.5 years [4] 

[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!