Atmospheric Degradation Initiated by OH Radicals of the Potential Foam Expansion Agent, CF3(CF2)2CH═CH2 (HFC-1447fz): Kinetics and Formation of Gaseous Products and Secondary Organic Aerosols

The assessment of the atmospheric impact of the potential foam expansion agent, CF3(CF2)2CH═CH2 (HFC-1447fz), requires the knowledge of its degradation routes, oxidation products, and radiative properties. In this paper, the gas-phase reactivity of HFC-1447fz with OH radicals is presented as a function of temperature, obtaining kOH (T = 263-358 K) = (7.4 ± 0.4) × 10(-13)exp{(161 ± 16)/T} (cm(3)·molecule(-1)·s(-1)) (uncertainties: ±2σ). The formation of gaseous oxidation products and secondary organic aerosols (SOAs) from the OH + HFC-1447fz reaction was investigated in the presence of NOx at 298 K. CF3(CF2)2CHO was observed at low- and high-NOx conditions. Evidence of SOA formation (ultrafine particles in the range 10-100 nm) is reported with yields ranging from 0.12 to 1.79%. In addition, the absolute UV (190-368 nm) and IR (500-4000 cm(-1)) absorption cross-sections of HFC-1447fz were determined at room temperature. No appreciable absorption in the solar actinic region (λ > 290 nm) was observed, leaving the removal by OH radicals as the main atmospheric loss process for HFC-1447fz. The major contribution of the atmospheric loss of HFC-1447fz is due to OH reaction (84%), followed by ozone (10%) and chlorine atoms (6%). Correction of the instantaneous radiative efficiency (0.36 W m(-2)·ppbv(-1)) with the relatively short lifetime of HFC-1447fz (ca. 8 days) implies that its global warming potential at a time horizon of 100 year is negligible (0.19) compared to that of HCFC-141b (782) and to that of modern foam-expansion blowing agents (148, 882, and 804 for HFC-152a, HFC-245fa and HFC-365mfc, respectively).

Atmospheric chemistry of ethers, esters, and alcohols on the lifetimes, temperature dependence, and kinetic isotope effect: an example of CF3CX2CX2CX2OX with OX reactions (X = H, D)

Mechanisms and kinetics of the reaction of CF₃CX₂CX₂CX₂OX with OX (X= H, D) radical are investigated on a sound theoretical basis.

Atmospheric chemistry of CF3(CX2)2CH2OH: rate coefficients and temperature dependence of reactions with chlorine atoms and the subsequent pathways of alkyl and alkoxy radicals (X = H, F)

The atmospheric and kinetic properties of CF₃(CX₂)₂CH₂OH (X = H, F) with chlorine atoms were studied by density functional and canonical variational transition state theories in conjunction with the small-curvature tunneling correction.

Hydroxyl radical reaction rate coefficients as a function of temperature and IR absorption cross sections for CF3CH=CH2 (HFO-1243zf), potential replacement of CF3CH2F (HFC-134a)

CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric lifetime of HFO-1243zf from the reported OH rate coefficients, k OH, determined under tropospheric conditions and (ii) to calculate its radiative efficiency from the reported IR absorption cross sections. The OH rate coefficient at 298 K also allows the estimation of the photochemical ozone creation potential (ε(POCP)). The pulsed laser photolysis coupled to a laser-induced fluorescence technique was used to determine k OH for the reaction of OH radicals with HFO-1243zf as a function of pressure (50-650 Torr of He) and temperature (263-358 K). Gas-phase IR spectra of HFO-1243zf were recorded at room temperature using a Fourier transform IR spectrometer between 500 and 4,000 cm(-1). At all temperatures, k OH did not depend on bath gas concentration (i.e., on the total pressure between 50 and 650 Torr of He). A slight but noticeable T dependence of k OH was observed in the temperature range investigated. The observed behavior is well described by the following Arrhenius expression: k OH(T) = (7.65 ± 0.26) × 10(-13) exp [(165 ± 10) / T] cm(3) molecule(-1) s(-1). Negligible IR absorption of HFO-1243zf was observed at wavenumbers greater than 1,700 cm(-1). Therefore, IR absorption cross sections, [Formula: see text], were determined in the 500-1,700 cm(-1) range. Integrated [Formula: see text] were determined between 650 and 1,800 cm(-1) for comparison purposes. The main diurnal removal pathway for HFO-1243zf is the reaction with OH radicals, which accounts for 64% of the overall loss by homogeneous reactions at 298 K. Globally, the lifetime due to OH reaction (τ OH) was estimated to be 8.7 days under the assumption of a well-mixed atmosphere. Assuming other removal pathways, the atmospheric lifetime (τ) was estimated to be ∼6 days. Considering the estimated τ OH and the measured IR absorption cross sections of HFO-1243zf in the atmospheric window (720-1,250 cm(-1)), its lifetime corrected radiative efficiency was calculated to be 0.019 W m(-2) ppbv(-1). GWP100 years for the HFO investigated, 0.29, is negligible compared to that of HFC-134a, the HFC to be potentially replaced (GWP100 years = 1,300, Hodnebrog et al. (Rev Geophys 51:300-378, 2013)). ε POCP for HFO-1243zf was estimated to be around 1 order of magnitude lower than that for ethylene. In conclusion, HFO-1243zf is fast degraded in the atmosphere, and it does not appreciably contribute to global warming and local/regional air pollution. Therefore, HFO-1243zf can be a suitable replacement for HFC-134a in air conditioning units.

Kinetic study of the OH and Cl-initiated oxidation, lifetimes and atmospheric acceptability indices of three halogenated ethenes

First relative kinetic study for the OH/Cl reactions with three chloro-fluoro-ethenes at room-temperature and atmospheric pressure and environmental acceptability.

Temperature effects on the removal of potential HFC replacements, CF3CH2CH2OH and CF3(CH2)2CH2OH, initiated by OH radicals

The gas-phase kinetic coefficients of OH radicals with two primary fluorinated alcohols, CF(3)CH(2)CH(2)OH (k(1)) and CF(3)(CH(2))(2)CH(2)OH (k(2)), potential replacements of hydrofluorocarbons (HFCs), are reported here as a function of temperature (T = 263-358 K) for the first time. k(1) and k(2) (together referred as k(i)) were measured under pseudo-first-order conditions with respect to the initial OH concentration using the pulsed laser photolysis/laser induced fluorescence technique. The observed temperature dependence of k(i) (in cm(3) molecule(-1) s(-1)) is described by the following Arrhenius expressions: k(1)(T) = (2.82 ± 1.28) × 10(-12) exp{-(302 ± 139)/T} cm(3) molecule(-1) s(-1) and k(2)(T) = (1.20 ± 0.73) × 10(-11) exp{-(425 ± 188)/T} cm(3) molecule(-1) s(-1).The uncertainties in the Arrhenius parameters are at a 95% confidence level (± 2σ). Uncertainties in k(i)(T) include both statistical and systematic errors. Activation energies were (2.5 ± 1.2) kJ/mol and (3.6 ± 1.6) kJ/mol for the OH-reaction with CF(3)CH(2)CH(2)OH and CF(3)(CH(2))(2)CH(2)OH, respectively. The global lifetime (τ) at 275 K for CF(3)CH(2)CH(2)OH and CF(3)(CH(2))(2)CH(2)OH due to the OH-reaction was estimated to be ca. 2 weeks and 5 days, respectively. The reported Arrhenius parameters can be used in 3D models that take into account the geographical region and season of emissions for estimating a matrix of instantaneous lifetimes. As a consequence of the substitution of the -CH(3) group by a -CH(2)OH group in HFCs, such as CF(3)CH(2)CH(3) and CF(3)(CH(2))(2)CH(3), the tropospheric lifetime with respect to the OH reaction is significantly shorter and, since their radiative forcing is similar, global warming potentials of CF(3)CH(2)CH(2)OH and CF(3)(CH(2))(2)CH(2)OH are negligible. Therefore, CF(3)CH(2)CH(2)OH and CF(3)(CH(2))(2)CH(2)OH seem to be suitable alternatives to HFCs.