The acid catalyzed nitration of methanol: formation of methyl nitrate via aerosol chemistry
| Autor: | Carly B. Robinson, Rachel M. Stephenson, R. R. Michelsen, Brent G. Riffel, Laura T. Iraci |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Atmospheric Chemistry. 58:253-266 |
| ISSN: | 1573-0662 0167-7764 |
| DOI: | 10.1007/s10874-007-9091-9 |
| Popis: | The aqueous phase acid-catalyzed reaction of methanol (CH3OH) with nitric acid (HNO3) to yield methyl nitrate (CH3ONO2) under atmospheric conditions has been investigated using gas-phase infrared spectroscopy. Reactions were conducted in aqueous sulfuric acid solutions (50.5–63.6 wt.%) with [CH3OH] = 0.00005–0.005 M and [HNO3] = 0.02–0.21 M, at 278.2–328.6 K. Methyl nitrate production rates increased linearly with CH3OH and HNO3 concentrations and exponentially with sulfuric acid weight percent within the regime studied. Rates increased linearly with nitronium ion \(\left( {{\text{NO}}_2^ + } \right)\) concentration, indicating that the reaction involves \({\text{NO}}_2^ + \) as the nitrating agent under these conditions. At 298 K, the rate of methyl nitrate production can be calculated from kobs[CH3OH][HNO3], where kobs = 2.337 × 10−13(exp(0.3198*wt.% H2SO4)) when the solubility of CH3ONO2 in acidic solution is approximated by H* for pure water. The temperature dependence of the rate coefficient is related to solution composition, with activation energies of 59 and 49 kJ/mol at 51.1 and 63.6 wt.% H2SO4, respectively, when k is calculated from rate\(\left[ {{\text{NO}}_2^ + } \right]^{ - 1} \left[ {{\text{CH}}_3 {\text{OH}}} \right]^{ - 1} \). The temperature dependence has also been parameterized for application to the atmosphere, but the small quantities of \({\text{NO}}_2^ + \) present in aerosol particles will result in methyl nitrate production rates too small to be of significance under most atmospheric conditions. |
| Databáze: | OpenAIRE |
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