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K.H. Becker Berichtnr. 53 1 I I I Atmosphe~cOxidation of Selected Alcohols and Esters K.H. Becker BerichtNr. 53 1 i i i 1 I i I i I i i I i DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. - . I Abstract Alcohols and esters are oxygenated volatile organic compounds of commercial interest as potential replacements for traditional solvents and fuel additives; their increased use will lead to an increased release into the atmosphere where these compounds will contribute to the formation of photochemical air pollution. Consequently, detailed knowledge of their chemical behaviour in the atmosphere is required to assess possible implications of their widespread application. Relative rate coefficients were measured for the gas-phase reactions of hydroxyl radicals and chlorine atoms with selected alcohols, esters and carbonyl oxidation products. At room temperature and atmospheric pressure, the following rate coefficients (in cm3 molecule-' s") were obtained 1-butanol (8.28 f 0.85) * - 1-pentanol (1.11 f 0.11) * lo-" - methyl propionate (9.29 f 1.13) * 10'" (1.51 f 0.22) * 10'" dimethyl succinate (1.95 f 0.27) (6.79 f 0.93) dimethyl glutarate (2.18 & 0.30) - (1.90 f 0.33) lo-" dimethyl adipate (3.73 & 0.59) (6.08 f 0.86) lo-" propionic formic anhydride - (2.89 f 0.35) * propionic acid - (4.72 f 0.62) - methyl pyruvate - (4.99 f 0.96) Product investigations were performed on the gas-phase oxidation of the two alcohols, 1-butanol and 1-pentanol, in the large-volume outdoor photoreactor EUPHORE in Valencia, Spain, with analyses by in situ Fourier transform infrared FIR) absorption spectroscopy, gas chromatography with photo-ionisation detection (GC-PID) and with %h performance liquid chromatography (HPLC). The OH initiated oxidation of 1-butanol in 1 bar of synthetic air in the presence of nitrogen monoxide led to the formation of butanal, propanal, ethanal, formaldehyde and 4-hydroxy-2-butanone with molar yields of 0.518 f 0.071, 0.234 fr 0.035, 0.127 f 0.022, 0.434 f 0.024 and 0.050 f 0.010, respectively. The OH initiated oxidation of 1-pentanol in 1 bar of synthetic air in the presence of nitrogen monoxide led to the formation of pentanal, butanal, propanal, ethanal and formaldehyde with molar yields of 0.405 f 0.082, 0.161 f 0.037,0.081 f 0.019,0.181 f 0.042 and 0.251 f 0.013, respectively. Further, the results support the possible formation of 5-hydroxy-2-pentanoneY and residual IR absorptions indicated the possible presence of compounds such as 3-hydroxy-propanal as product of the reaction system. C1 atom initiated product studies were performed, in the presence of NO,, on methyl propionate and dimethyl succinate in a laboratory reaction vessel in Wuppertal, using FTIR analyses; this approach was necessary to conveniently emulate the OH radical chemistry since these compounds react very slowly with OH radicals. The products formed in the C1 atom initiated oxidation of methyl propionate and their molar yields were: propionic formic anhydride 0.099 f 0.019; propionic acid 0.139 f 0.027; carbon monoxide 0.132 2 0.026; methyl pyruvate 0.289 f 0.057; ethanalO.077 f 0.015; methoxy formyl peroxy nitrate 0.083 f 0.016; methyl glyoxylate 0.111 f 0.022. The products formed in the C1 atom initiated oxidation of dimethyl succinate and their molar yields were: succinic formic anhydride 0.341 f 0.068; mono- methyl succinate 0.447 f 0.111; carbon monoxide 0.307 f 0.061; dimethyl oxaloacetate 0.176 f 0.044, and methoxy formyl peroxy nitrate 0.032-0.084. The product studies allowed the construction of detailed photooxidation mechanisms for the selected oxygenated compounds required for atmospheric modelling. Contents INTRODUCTION...................................................................................................................................... 1 1.1 Oxygenated volatile organic compounds .......................................................................................... 1 1.2 State of the art ....................................................................................................................................... 4 1.3 Compounds investigated ..................................................................................................................... 6 1.4 of the work .................................................................................................................................... 7 EXE3UMENTA.L...................................................................................................................................... 9 2.1 Reaction chambers ............................................................................................................................... 9 .. 2.1.1 Desmpt.ton of 405 [ reactor ...................................................................................................... 9 .. 2.1.2 Descnpt.ton of 480 [ reactor .................................................................................................... 10 2.1.3 Description of the European photoreactor EUP~oRE .................................................... 11 2.2 Procedure and analysis at the Wuppertal laboratory ..................................................................... 13 2.2.1 General ........................................................................................................................................ 13 2.2.2 Relative rate method ................................................................................................................. 14 2.2.3 Product analysis ......................................................................................................................... 16 2.3 EUPHORE-experiments ................................................................................................................... 18 KINETIC STUDY .................................................................................................................................... 23 3.1 Hydroxyl ra&cal reaction rate coefficients...................................................................................... 23 3.1.1 Results ......................................................................................................................................... 23 3.1.2 Discussion .................................................................................................................................. 25 3.2 Chlorine atom reaction rate coefficients......................................................................................... 31 3.2.1 Results ......................................................................................................................................... 31 3.2.2 Discussion .................................................................................................................................. 33 ATMOSPHERIC OXIDATION OF ALCOHOLS ............................................................................ 35 4.1 General mechanistic considerations on the degradation of primary alcohols ........................... 35 4.2 Atmospheric degradation of I-pentanol ......................................................................................... 39 .4.2.1 Results ......................................................................................................................................... 39 4.2.2 Discussion: mechanistic considerations based on JARand the product yield data .......43 4.3 Atmospheric degradation of 1-butanol ........................................................................................... 51 4.3.1 Results ......................................................................................................................................... 51 4.3.2 Discussion: mechanistic considerations based on JAR and the product yield data .......54 i 5 ATMOSPHERIC OXIDATION OF ESTERS ................................................................................... 59 51 General mechanistic considerations on the degradation of esters .............................................. 59 5.2 Atmospheric degradation of methyl propionate ............................................................................ 63 5.2.1 Results ......................................................................................................................................... 63 5.2.2 Discussion .................................................................................................................................. 67 5.3 Atmospheric degradation of dimethyl succinate............................................................................ 73 5.3.1 Results ......................................................................................................................................... 73 5.32 Discussion .................................................................................................................................. 76 6 . FUNCTIONAL GROUP REACTIVITY .................... i................................................. :............ : ......... 81 6.1 Alcohol ................................................................................................................................................. 81 6.2 Ester ...................................................................................................................................................... 85 7 ATMOSPHERIC IMPLICATIONS .....................................................................................................
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