Blowers2007 - Theor Chem Account(2008 119:369381 DOI...

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Theor Chem Account (2008) 119:369–381 DOI 10.1007/s00214-007-0394-3 REGULAR ARTICLE Global warming potential predictions for hydroFuoroethers with two carbon atoms Paul Blowers · Kyle ±ranklin Tetrault · Yirla Trujillo-Morehead Received: 29 May 2007 / Accepted: 11 October 2007 / Published online: 6 November 2007 © Springer-Verlag 2007 Abstract Global warming potentials are predicted using computational chemistry and thermodynamics approaches for four hydroFuoroethers where no data have previously been available. We also compare results with the same methodology for six other species. We combine predictions of radiative forcing values from density functional theory computations at the B3LYP/6-31g* level of theory with previous experimentally determined or newly estimated hydroxyl radical-hydrogen abstraction rate constants to obtain these global warming potentials. We ±nd that many of the H²Es studied have lower global warming potentials than the hydroFuorocarbons and chloroFuorocarbons they may soon replace, although other environmental and techni- cal issues may need to be addressed ±rst. Keywords Radiative forcing · HydroFuoroethers · Quantum chemistry · Global warming potentials · GWP 1 Introduction HydroFuoroethers (H²Es) are a class of compounds which have recently been the focus of intense attention as replace- ment materials for chloroFuorocarbons (C²Cs) and hydro- Fuorocarbons (H²Cs) [ 1 33 ]. While there have been 33 US patents±ledfortheuseofH²Esinthepast20months[ 34 , 35 ], Electronic supplementary material The online version of this article (doi: 10.1007/s00214-007-0394-3 ) contains supplementary material, which is available to authorized users. P. Blowers ( B ) · K. ². Tetrault · Y. Trujillo-Morehead Department of Chemical and Environmental Engineering, The University of Arizona, PO Box 210011, Tucson, AZ 85721-0011, USA e-mail: [email protected] relatively little information is known about their physical pro- perties or environmental impacts. The main impetus for their potential introduction into widespread industrial use is that the H²E class of compounds has been postulated, and in some cases proven, to have lower global warming potentials (GWPs) than the H²Cs they would replace. GWPs can be calculated relative to the reference CO 2 informationwhenoneknowskineticratesofattackofthespe- cies i by hydroxyl radical in the troposphere combined with infrared spectroscopy using the following equation [ 36 38 ]: GWP i = ± TH 0 a i [ x i ( t ) ]d t ± TH 0 a ref [ x ref ( t ) ]d t (1) where TH is the time horizon for GWP the species will be considered over, a i is the radiative forcing due to a unit increase in atmospheric concentration, and [ x i ( t ) ]isthetime- dependent concentration of a pulse of species i . Equation ( 1 ) can be transformed to use atmospheric life- time, τ , instead of integrating the concentration of the species over time: GWP i = a i ± TH 0 e - t d t AGWP CO 2 ( TH ) (2) where atmospheric lifetime is denoted as: τ lifetime , R = τ lifetime , CH 3 CCl 3 k OH + CH 3 CCl 3 ( 277 K ) k OH + R ( 277 K ) (3) In this work, we use the AGWPs at 20, 100 and 500year time horizons (THs) for the CO 2
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Blowers2007 - Theor Chem Account(2008 119:369381 DOI...

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