Abstract
The atmospheric chemistry of dimethylether, dimethoxymethane, trimethoxymethane, cyclohexane, 1,4-dioxane, 1,3,5-trioxane and phenol have been studied in this work. The present thesis gives an extended summary of nine papers given in Appendix A to Appendix I. Sections 1 to 3 contains Abstract, Danish summery, and Motivation. Section 4 describes the pulse radiolysis technique used at Risoe National Laboratory and the FTIR Smog chamber technique used at Ford Motor Company. Sections 5 to 8 present results of absolute rate constants and UV absorption spectra obtained at Risoe. Sections 9 to 12 present results of relative rate constants and atmospheric degradations
studies performed at Ford. Section 13 gives a conclusion. Some of the sections are in the following further described. Section 5 reports rate constants for reactions between OH radicals and CH3OCH2OCH3, (CH3O)3CH, 1,4- dioxane, and 1,3,5-trioxane and they are measured to (4.9 ± 1.9) x 10-12, (6.0 ± 0.4) x 10-12, (11.6 ± 0.8) x 10-12, (6.0 ± 1.0) x 10-12 cm3 molecule-1 s-1, respectively. The obtained rate constants are 210-348% higher than expected using the Structure-Reactivity Relationship model suggested by Atkinson [1].
In section 6 UV absorption spectra of (CH3O)2CHOCH2(•) (CH3O)2CHOCH2O2(•), c-C4H7O2(•), (c-C4H7O2)O2(•), c-C3H5O3(•), (c-C3H5O3)O2(•), c-C6H11(•), and c-C6H11O2(•) radicals were recorded between (220-230) and (290-320) nm. They all show broad features with a typical maximum absorption cross section of approximately 6 x 10-18 cm2 molecule-1. UV absorption spectra of C6H5(•) and C6H5O(•) radicals were obtained between 220 - 575 nm and 220 - 400 nm, respectively. They both show a maximum absorption cross section of approximately 4 x 10-17 cm2 molecule-1 at approximately 245 nm. In section 7 self-reactions and reactions with O2 for CH3OCH2(•), (CH3O)2CHOCH2(•), c-C4H7O2(•), c-C3H5O3(•), and c-C6H11(•) radicals were studied. Rate constants for the self-reactions are of the order of 3-4 x 10-11 cm3 molecule-1 s-1. This is approximately a factor of 4 higher than rate constants for reactions between the alkyl radicals and O2. The reaction between C6H5O(•) radicals and O2 is slow with an upper limit of 5 x 10-21 cm3 molecule-1 s-1. Reaction between the C6H5(•) radical and NO show a rate constant of 2 x 10-11 cm3 molecule-1 s-1 where as reactions C6H5O(•) radicals and NO or NO2 show rate constants of2 x 10-11 and 2 x 10-12 cm3 molecule-1 s-1, respectively. In section 8 self-reactions of (CH3O)2CHOCH2O2(•), (c-C4H7O2)O2(•), and (c-C3H5O3)O2(•) radicals give rate constants which are a factor of 3 lower than self-reactions obtained for the corresponding alkyl radicals. Rate constants for the reactions between these alkyl peroxy radicals and NO or NO2, together with the reactions between the c-C6H11O2(•) radical and NO or NO2 were reported. In all cases rate constants for NO2 reactions are higher than the corresponding rate constants for NO reactions. Obtained rate constants were from (9.5 ± 1.5) x 10-12 to (1.3 ± 0.3) x 10-11 cm3 molecule-1 s-1. In section 9 a large number of relative rate constants with relation to experiments in the smog-chamber were reported.
In section 10 the atmospheric degradations of CH3OCH2OCH3, (CH3O)3CH, c-C6H12, 1,4-dioxane, and 1,3,5-trioxane were studied. CH3OCH2OCH3 give two major products, CH3OCH2OCHO and CH3OC(O)OCH3, arising from abstraction of H atoms placed at the primary and secondary carbon, respectively. CH3OC(O)OCH3 is the only product observed from (CH3O)3CH. The studies of 1,4-dioxane and 1,3,5-trioxane give only one product each HC(O)OCH2CH2OCHO and HC(O)OCH2OCHO, respectively. Section 11 reports the atmospheric degradation of cyclohexane. The fate is competition between decomposition of the sixmembered ring and formation of cyclohexanone. The formation of cyclohexanone is a function of the O2 concentration. At 1 atmosphere of air the yield of cyclohexanone is 39 ± 3.9% whereas 61 ± 6.1% of the oxidised cyclohexane decompose. In section 12 the atmospheric fate of C6H5O(•) radical is reaction with NO or NO2. The major product from the smog-chamber experiments is a (C6H5O)2 compound. Using smog-chamber experiments, GC-MS, and quantum mechanical calculations of the structure of (C6H5O)2 give that the formed (C6H5O)2 is determined to be 4-phenoxyphenol.
studies performed at Ford. Section 13 gives a conclusion. Some of the sections are in the following further described. Section 5 reports rate constants for reactions between OH radicals and CH3OCH2OCH3, (CH3O)3CH, 1,4- dioxane, and 1,3,5-trioxane and they are measured to (4.9 ± 1.9) x 10-12, (6.0 ± 0.4) x 10-12, (11.6 ± 0.8) x 10-12, (6.0 ± 1.0) x 10-12 cm3 molecule-1 s-1, respectively. The obtained rate constants are 210-348% higher than expected using the Structure-Reactivity Relationship model suggested by Atkinson [1].
In section 6 UV absorption spectra of (CH3O)2CHOCH2(•) (CH3O)2CHOCH2O2(•), c-C4H7O2(•), (c-C4H7O2)O2(•), c-C3H5O3(•), (c-C3H5O3)O2(•), c-C6H11(•), and c-C6H11O2(•) radicals were recorded between (220-230) and (290-320) nm. They all show broad features with a typical maximum absorption cross section of approximately 6 x 10-18 cm2 molecule-1. UV absorption spectra of C6H5(•) and C6H5O(•) radicals were obtained between 220 - 575 nm and 220 - 400 nm, respectively. They both show a maximum absorption cross section of approximately 4 x 10-17 cm2 molecule-1 at approximately 245 nm. In section 7 self-reactions and reactions with O2 for CH3OCH2(•), (CH3O)2CHOCH2(•), c-C4H7O2(•), c-C3H5O3(•), and c-C6H11(•) radicals were studied. Rate constants for the self-reactions are of the order of 3-4 x 10-11 cm3 molecule-1 s-1. This is approximately a factor of 4 higher than rate constants for reactions between the alkyl radicals and O2. The reaction between C6H5O(•) radicals and O2 is slow with an upper limit of 5 x 10-21 cm3 molecule-1 s-1. Reaction between the C6H5(•) radical and NO show a rate constant of 2 x 10-11 cm3 molecule-1 s-1 where as reactions C6H5O(•) radicals and NO or NO2 show rate constants of2 x 10-11 and 2 x 10-12 cm3 molecule-1 s-1, respectively. In section 8 self-reactions of (CH3O)2CHOCH2O2(•), (c-C4H7O2)O2(•), and (c-C3H5O3)O2(•) radicals give rate constants which are a factor of 3 lower than self-reactions obtained for the corresponding alkyl radicals. Rate constants for the reactions between these alkyl peroxy radicals and NO or NO2, together with the reactions between the c-C6H11O2(•) radical and NO or NO2 were reported. In all cases rate constants for NO2 reactions are higher than the corresponding rate constants for NO reactions. Obtained rate constants were from (9.5 ± 1.5) x 10-12 to (1.3 ± 0.3) x 10-11 cm3 molecule-1 s-1. In section 9 a large number of relative rate constants with relation to experiments in the smog-chamber were reported.
In section 10 the atmospheric degradations of CH3OCH2OCH3, (CH3O)3CH, c-C6H12, 1,4-dioxane, and 1,3,5-trioxane were studied. CH3OCH2OCH3 give two major products, CH3OCH2OCHO and CH3OC(O)OCH3, arising from abstraction of H atoms placed at the primary and secondary carbon, respectively. CH3OC(O)OCH3 is the only product observed from (CH3O)3CH. The studies of 1,4-dioxane and 1,3,5-trioxane give only one product each HC(O)OCH2CH2OCHO and HC(O)OCH2OCHO, respectively. Section 11 reports the atmospheric degradation of cyclohexane. The fate is competition between decomposition of the sixmembered ring and formation of cyclohexanone. The formation of cyclohexanone is a function of the O2 concentration. At 1 atmosphere of air the yield of cyclohexanone is 39 ± 3.9% whereas 61 ± 6.1% of the oxidised cyclohexane decompose. In section 12 the atmospheric fate of C6H5O(•) radical is reaction with NO or NO2. The major product from the smog-chamber experiments is a (C6H5O)2 compound. Using smog-chamber experiments, GC-MS, and quantum mechanical calculations of the structure of (C6H5O)2 give that the formed (C6H5O)2 is determined to be 4-phenoxyphenol.
| Original language | English |
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| Place of Publication | Roskilde |
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| Publisher | Risø National Laboratory |
| Number of pages | 73 |
| ISBN (Print) | 87-550-2673-7 |
| ISBN (Electronic) | 87-550-2674-5 |
| Publication status | Published - 2000 |
| Series | Denmark. Forskningscenter Risoe. Risoe-R |
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| Number | 1170(EN) |
| ISSN | 0106-2840 |
Keywords
- Risø-R-1170(EN)
- Risø-R-1170