Atmospheric chemistry of n-C6F13CH2CHO: formation from n-C6F13CH2CH2OH, kinetics, and mechanisms of reactions with chlorine atoms and OH radicals

Smog chamber FTIR techniques were used to measure k(Cl + n-C(6)F(13)CH(2)CHO) = (1.84 +/- 0.22) x 10(-11), k(Cl + n-C(6)F(13)CHO) = (1.75 +/- 0.70) x 10(-12), and k(OH + n-C(6)F(13)CH(2)CHO) = (2.15 +/- 0.26) x 10(-12) cm(3) molecule(-1) s(-1) in 700 Torr of N(2) or air diluent at 296 +/- 2K. The chlorine-atom-initiated oxidation of n-C(6)F(13)CH(2)CH(2)OH in air gives n-C(6)F(13)CH(2)CHO in a molar yield of 99 +/- 8%. The atmospheric fate of n-C(6)F(13)CH(2)C(O) radicals is reaction with O(2), while the fate of n-C(6)F(13)C(O) radicals is decomposition to give n-C(6)F(13) radicals and CO. The results are discussed with respect to the atmospheric chemistry of fluorinated alcohols and the formation of perfluorocarboxylic acids.

Low-CO(2) electricity and hydrogen: a help or hindrance for electric and hydrogen vehicles?

The title question was addressed using an energy model that accounts for projected global energy use in all sectors (transportation, heat, and power) of the global economy. Global CO(2) emissions were constrained to achieve stabilization at 400-550 ppm by 2100 at the lowest total system cost (equivalent to perfect CO(2) cap-and-trade regime). For future scenarios where vehicle technology costs were sufficiently competitive to advantage either hydrogen or electric vehicles, increased availability of low-cost, low-CO(2) electricity/hydrogen delayed (but did not prevent) the use of electric/hydrogen-powered vehicles in the model. This occurs when low-CO(2) electricity/hydrogen provides more cost-effective CO(2) mitigation opportunities in the heat and power energy sectors than in transportation. Connections between the sectors leading to this counterintuitive result need consideration in policy and technology planning.

Atmospheric chemistry of 4:2 fluorotelomer acrylate [C4F9CH2CH2OC(O)CH=CH2]: kinetics, mechanisms, and products of chlorine-atom- and OH-radical-initiated oxidation

Relative rate techniques were used to measure the rate constants k[Cl + C(4)F(9)CH(2)CH(2)OC(O)CH=CH(2)] = (2.21 +/- 0.16) x 10(-10) and k[OH + C(4)F(9)CH(2)CH(2)OC(O)CH=CH(2)] = (1.13 +/- 0.12) x 10(-11) cm(3) molecule(-1) s(-1) in 700 Torr of N(2) or air diluent at 296 K. The atmospheric lifetime of C(4)F(9)CH(2)CH(2)OC(O)CHCH(2) (4:2 FTAc) is determined by its reaction with OH radicals and is approximately 1 day. The chlorine-atom-initiated oxidation of 4:2 FTAc in 700 Torr of air at 296 K gives C(4)F(9)CH(2)C(O)H in molar yields of 18% and 10% in the absence and presence of NO, respectively. The OH-radical-initiated oxidation of 4:2 FTAc in 700 Torr of air in the presence of NO gives HCHO in a molar yield of (102 +/- 7)%, with C(4)F(9)CH(2)CH(2)OC(O)C(O)H (4:2 fluorotelomer glyoxylate) as the expected coproduct. The atmospheric fate of the 4:2 fluorotelomer glyoxylate will be photolysis and reaction with OH radicals, which will lead to the formation of C(4)F(9)CH(2)C(O)H and ultimately perfluorinated carboxylic acids. The atmospheric oxidation of fluorotelomer acrylates is a potential source of perfluorinated carboxylic acids in remote locations.

Fuel and vehicle technology choices for passenger vehicles in achieving stringent CO2 targets: connections between transportation and other energy sectors

The regionalized Global Energy Transition (GET-R 6.0) model has been modified to include a detailed description of light-duty vehicle options and used to investigate the potential impact of carbon capture and storage (CCS) and concentrating solar power (CSP) on cost-effective fuel/vehicle technologies in a carbon-constrained world. Total CO2 emissions were constrained to achieve stabilization at 400-550 ppm, by 2100, at lowesttotal system cost The dominantfuel/vehicle technologies varied significantly depending on CO2 constraint future cost of vehicle technologies, and availability of CCS and CSP. For many cases, no one technology dominated on a global scale. CCS provides relatively inexpensive low-CO2 electricity and heatwhich prolongs the use of traditional ICEVs. CSP displaces fossil fuel derived electricity, prolongs the use of traditional ICEVs, and promotes electrification of passenger vehicles. In all cases considered, CCS and CSP availability had a major impact on the lowest cost fuel/vehicle technologies, and alternative fuels are needed in response to expected dwindling oil and natural gas supply potential by the end of the century.

Atmospheric chemistry of 4:2 fluorotelomer iodide (n-C4F9CH2CH2I): kinetics and products of photolysis and reaction with OH radicals and Cl atoms

Relative rate techniques were used to study the title reactions and determine rate constants of k(Cl + C(4)F(9)CH(2)CH(2)I) = (1.25 +/- 0.15) x 10(-12) and k(OH + C(4)F(9)CH(2)CH(2)I) = (1.2 +/- 0.6) x 10(-12) cm(3) molecule(-1) s(-1) in 700 Torr total pressure at 295 K. The fluorotelomer aldehyde (C(4)F(9)CH(2)CHO), perfluorinated aldehyde (C(4)F(9)CHO), fluorotelomer acid (C(4)F(9)CH(2)C(O)OH), fluorotelomer peracid (C(4)F(9)CH(2)C(O)OOH), and several perfluorocarboxylic acids were detected by in situ FTIR spectroscopy and offline analysis as products of the chlorine atom initiated oxidation of C(4)F(9)CH(2)CH(2)I in air. The UV-visible spectra of C(4)F(9)CH(2)CH(2)I and C(2)H(5)Cl were recorded over the range of 200-400 nm. Photolysis of C(4)F(9)CH(2)CH(2)I gives C(4)F(9)CH(2)CHO as the major observed product. By assumption of a photolysis quantum yield of unity, it was calculated that the atmospheric lifetime of C(4)F(9)CH(2)CH(2)I is determined by photolysis and is a few days. A mechanism for the atmospheric oxidation of fluorotelomer iodides, (C(x)F(2x+1)CH(2)CH(2)I, where x = 2, 4, 6,...) is proposed. Atmospheric oxidation of fluorotelomer iodides is a potential source of perfluorocarboxylic acids.

Atmospheric chemistry of sulfuryl fluoride: reaction with OH radicals, Cl atoms and O3, atmospheric lifetime, IR spectrum, and global warming potential

Sulfuryl fluoride (SO2F2) is a radiatively active industrial chemical released into the atmosphere in significant (ktonne/ year) quantities. The potential for SO2F2 to contribute to radiative forcing of climate change needs to be assessed. Long path length FTIR/smog chamber techniques were used to investigate the kinetics of the gas-phase reactions of Cl atoms, OH radicals, and O3 with SO2F2, in 700 Torr total pressure of air or N2 at 296 +/- 1 K. Upper limits of k(Cl + SO2F2) < 9 x 10(-19), k(OH + SO2F2) < 1.7 x 10(-14) and k(O3 + SO2F2) < 5.5 x 10(-24) cm3 molecule(-1) s(-1) were determined. Reaction with Cl atoms, OH radicals, or O3 does not provide an efficient removal mechanism for SO2F2. The infrared spectrum of SO2F2 is reported and a radiative efficiency of 0.196 W m(-2) ppbv(-1) was calculated. Historic production data estimates are presented which provide an upper limit for expected atmospheric concentrations. The radiative forcing of climate change associated with emissions of SO2F2 depends critically on the atmospheric lifetime of SO2F2. Further research is urgently needed to define the magnitude of potential nonatmospheric sinks.

Paint solvent to food additive: an environmental route of dehalogenation for 4-chlorobenzotrifluoride

In an effort to reduce volatile organic compounds (VOCs) in paint solvents, replacements containing non-VOC compounds have been proposed. One such compound is 4-chlorobenzotrifluoride (CBTF), for which environmental fate studies have not been conducted. The objective of the present study was to determine the products of the atmospheric oxidation of CBTF and the aqueous fate of these products. Smog chamber experiments were performed to measure the kinetics and mechanism of atmospheric oxidation. A rate constant of 2.22 (+/-0.30) x 10(-13) cm3 molecule(-1) s(-1) was determined for the reaction of hydroxyl radicals with CBTF in 700 Torr of air at 296 K. Using offline sampling and gas chromatography coupled to mass spectroscopic analysis, it was determined that 2-chloro-5-trifluoromethylphenol (o-CTFP) was the primary product of CBTF atmospheric oxidation. Aqueous photolysis of o-CTFP in deionized water proceeded at a rate of 1.3 (+/-0.1) x 10(-4) s(-1), corresponding to a half-life of 1.5 +/- 0.1 h and a quantum yield of 6.6 (+/-0.4) x 10(-4). The mechanism of photolysis was investigated using liquid chromatography coupled to tandem mass spectrometry, which suggested that degradation of o-CTFP occurred via photonucleophilic displacement of chlorine, followed by photoinduced hydrolysis of the trifluoromethyl group to yield 3,4-dihydroxybenzoic acid (an approved food additive considered to be nontoxic).

Atmospheric chemistry of 2-ethoxy-3,3,4,4,5-pentafluorotetrahydro-2,5-bis[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]-furan: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of the title compound which we refer to as RfOC2H5. Rate constants of k(Cl + RfOC2H5) = (2.70 +/- 0.36) x 10(-12), k(OH + RfOC2H5) = (5.93 +/- 0.85) x 10(-14), and k(Cl + RfOCHO) = (1.34 +/- 0.20) x 10(-14) cm3 molecule(-1') s(-1) were measured in 700 Torr of N2, or air, diluent at 294 +/- 1 K. From the value of k(OH + RfOC2H5) the atmospheric lifetime of RfOC2H5 was estimated to be 1 year. Two competing loss mechanisms for RfOCH(O*)CH3 radicals were identified in 700 Torr of N2/O2 diluent at 294 +/- 1 K; decomposition via C-C bond scission giving a formate (RfOCHO), or reaction with 02 giving an acetate (RfOC(O)CH3). In 700 Torr of N2/O2 diluent at 294 +/- 1 K the rate constant ratio k(O2)/k(diss) = (1.26 +/- 0.74) x 10(-19) cm3 molecule(-1). The OH radical initiated atmospheric oxidation of RfOC2H5 gives Rf0CHO and RfOC(O)CH3 as major products. RfOC2H5 has a global warming potential of approximately 55 for a 100 year horizon. The results are discussed with respect to the atmospheric chemistry and environmental impact of RfOC2H5.

Rate Constants for the Reaction of Cl with a Series of C4 to C6 Ketones Using the Relative Rate Method

Rate constants for the reaction of Cl with eight ketones were measured relative to the rate constant of propane in approximately 900 Torr of N2 at ambient temperature. Experiments were carried out in a Pyrex reactor with GC analysis of the consumption of the ketones and propane. Chlorine atoms were generated by irradiation of Cl2 in the initial mixture using a black-light-blue fluorescent lamp. The rate constants determined in these experiments (10-11 cm3 molecule-1 s-1) are: butanone (3.8 +/- 0.3); 2-pentanone (11.6 +/- 1.0); 3-pentanone (8.3 +/- 0.7); 2-hexanone (19.4 +/- 1.9); 3-hexanone (15.3 +/- 1.1); cyclopentanone (10.4 +/- 0.9); 3-methyl-2-butanone (6.2 +/- 0.5); and 4-methyl-2-pentanone (12.8 +/- 1.0). The results for 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, 3-methyl-2-butanone, and 4-methyl-2-pentanone are significantly higher (by a factor of 3 for 2-hexanone) than reported in two previous absolute rate studies. The likely explanation for this discrepancy is discussed.

Atmospheric Chemistry of the Z and E Isomers of CF3CFCHF; Kinetics, Mechanisms, and Products of Gas-Phase Reactions with Cl Atoms, OH Radicals, and O3

Smog chamber/FTIR techniques were used to study the atmospheric chemistry of the Z and E isomers of CF3CF=CHF, which we refer to as CF3CF=CHF(Z) and CF3CF=CHF(E). The rate constants k(Cl + CF3CF=CHF(Z)) = (4.36 +/- 0.48) x 10-11, k(OH + CF3CF=CHF(Z)) = (1.22 +/- 0.14) x 10-12, and k(O3 + CF3CF=CHF(Z)) = (1.45 +/- 0.15) x 10-21 cm3 molecule-1 s-1 were determined for the Z isomer of CF3CF=CHF in 700 Torr air diluent at 296 +/- 2 K. The rate constants k(Cl + CF3CF=CHF(E)) = (5.00 +/- 0.56) x 10-11, k(OH + CF3CF=CHF(E)) = (2.15 +/- 0.23) x 10-12, and k(O3 + CF3CF=CHF(E)) = (1.98 +/- 0.15) x 10-20 cm3 molecule-1 s-1 were determined for the E isomer of CF3CF=CHF in 700 Torr air diluent at 296 +/- 2 K. Both the Cl-atom and OH-radical-initiated atmospheric oxidation of CF3CF=CHF give CF3C(O)F and HC(O)F in molar yields indistinguishable from 100% for both the Z and E isomer. CF3CF=CHF(Z) has an atmospheric lifetime of approximately 18 days and a global warming potential (100 year time horizon) of approximately 6. CF3CF=CHF(E) has an atmospheric lifetime of approximately 10 days and a global warming potential (100 year time horizon) of approximately 3. CF3CF=CHF has a negligible global warming potential and will not make any significant contribution to radiative forcing of climate change.

Atmospheric chemistry of 4:2 fluorotelomer alcohol (n-C4F9CH2CH2OH): products and mechanism of Cl atom initiated oxidation in the presence of NOx

Smog chamber/FTIR techniques were used to study the Cl atom initiated oxidation of 4:2 fluorotelomer alcohol (C(4)F(9)CH(2)CH(2)OH, 4:2 FTOH) in the presence of NO(x) in 700 Torr of N(2)/O(2) diluent at 296 K. Chemical activation effects play an important role in the atmospheric chemistry of the peroxy, and possibly the alkoxy, radicals derived from 4:2 FTOH. Cl atoms react with C(4)F(9)CH(2)CH(2)OH to give C(4)F(9)CH(2)C(*)HOH radicals which add O(2) to give chemically activated alpha-hydroxyperoxy radicals, [C(4)F(9)CH(2)C(OO(*))HOH]*. In 700 Torr of N(2)/O(2) at 296 K, approximately 50% of the [C(4)F(9)CH(2)C(OO(*))HOH]* radicals decompose "promptly" to give HO(2) radicals and C(4)F(9)CH(2)CHO, the remaining [C(4)F(9)CH(2)C(OO(*))HOH]* radicals undergo collisional deactivation to give thermalized peroxy radicals, C(4)F(9)CH(2)C(OO(*))HOH. Decomposition to HO(2) and C(4)F(9)CH(2)CHO is the dominant atmospheric fate of the thermalized peroxy radicals. In the presence of excess NO, the thermalized peroxy radicals react to give C(4)F(9)CH(2)C(O(*))HOH radicals which then decompose at a rate >2.5 x 10(6) s(-1) to give HC(O)OH and the alkyl radical C(4)F(9)CH(2)(*). The primary products of 4:2 FTOH oxidation in the presence of excess NO(x) are C(4)F(9)CH(2)CHO, C(4)F(9)CHO, and HCOOH. Secondary products include C(4)F(9)CH(2)C(O)O(2)NO(2), C(4)F(9)C(O)O(2)NO(2), and COF(2). In contrast to experiments conducted in the absence of NO(x), there was no evidence (<2% yield) for the formation of the perfluorinated acid C(4)F(9)C(O)OH. The results are discussed with regard to the atmospheric chemistry of fluorotelomer alcohols.

Atmospheric chemistry of CF3CH=CH2 and C4F9CH=CH2: products of the gas-phase reactions with Cl atoms and OH radicals

FTIR-smog chamber techniques were used to study the products of the Cl atom and OH radical initiated oxidation of CF3CH=CH2 in 700 Torr of N2/O2, diluent at 296 K. The Cl atom initiated oxidation of CF3CH=CH2 in 700 Torr of air in the absence of NOx gives CF3C(O)CH2Cl and CF3CHO in yields of 70+/-5% and 6.2+/-0.5%, respectively. Reaction with Cl atoms proceeds via addition to the >C=C< double bond (74+/-4% to the terminal and 26+/-4% to the central carbon atom) and leads to the formation of CF3CH(O)CH2Cl and CF3CHClCH2O radicals. Reaction with O2 and decomposition via C-C bond scission are competing loss mechanisms for CF3CH(O)CH2Cl radicals, kO2/kdiss=(3.8+/-1.8)x10(-18) cm3 molecule-1. The atmospheric fate of CF3CHClCH2O radicals is reaction with O2 to give CF3CHClCHO. The OH radical initiated oxidation of CxF2x+1CH=CH2 (x=1 and 4) in 700 Torr of air in the presence of NOx gives CxF2x+1CHO in a yield of 88+/-9%. Reaction with OH radicals proceeds via addition to the >C=C< double bond leading to the formation of CxF2x+1C(O)HCH2OH and CxF2x+1CHOHCH2O radicals. Decomposition via C-C bond scission is the sole fate of CxF2x+1CH(O)CH2OH and CxF2x+1CH(OH)CH2O radicals. As part of this work a rate constant of k(Cl+CF3C(O)CH2Cl)=(5.63+/-0.66)x10(-14) cm3 molecule-1 s-1 was determined. The results are discussed with respect to previous literature data and the possibility that the atmospheric oxidation of CxF2x+1CH=CH2 contributes to the observed burden of perfluorocarboxylic acids, CxF2x+1COOH, in remote locations.

Atmospheric Chemistry of a Model Biodiesel Fuel, CH3C(O)O(CH2)2OC(O)CH3: Kinetics, Mechanisms, and Products of Cl Atom and OH Radical Initiated Oxidation in the Presence and Absence of NOx

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.

Pulsed Laser Photolysis Vacuum UV Laser-Induced Fluorescence Kinetic Study of the Gas-Phase Reactions of Cl(2P3/2) Atoms with C3−C6 Ketones

The gas-phase reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone at 295 +/- 2 K were studied using pulsed laser photolysis vacuum UV laser-induced fluorescence (PLP-LIF) techniques. Cl(2P(3/2)) atoms were produced by photolysis of Cl2 at 351 nm and monitored by LIF spectroscopy at 134.72 nm (3p(5) 2P(3/2)-3p(4)4s 2P(3/2) transition). Rate coefficients for reactions of Cl atoms with acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, and cyclopentanone are (2.30 +/- 0.12) x 10(-12), (4.08 +/- 0.21) x 10(-11), (1.23 +/- 0.13) x 10(-10), (8.87 +/- 0.92) x 10(-11), (2.08 +/- 0.32) x 10(-10), (1.43 +/- 0.19) x 10(-10) and (1.16 +/- 0.12) x 10(-10) cm3 molecule(-1) s(-1), respectively. The results for acetone and butanone are consistent with previous studies. The results for 2-pentanone, 3-pentanone, 2-hexanone, and 3-hexanone are approximately a factor of 2-3 higher than those from previous absolute rate studies. Likely explanations for these discrepancies are discussed. Tropospheric lifetimes of ketones with respect to reaction with Cl atoms are estimated and discussed.