The acid catalyzed nitration of methanol: formation of methyl nitrate via aerosol chemistry |
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| Authors: | Laura T Iraci Brent G Riffel Carly B Robinson Rebecca R Michelsen Rachel M Stephenson |
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| Institution: | (1) Atmospheric Science Branch, NASA Ames Research Center, Mail Stop 245-5, Moffett Field, CA 94035, USA;(2) Institute of Transportation Studies, University of California Davis, Davis, CA 95616, USA;(3) Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA;(4) Chemistry Department, Randolph-Macon College, Ashland, VA 23005, USA;(5) Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA |
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| Abstract: | 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  concentration, indicating that the reaction involves  as the nitrating agent under these conditions. At 298 K, the rate of methyl nitrate production can be calculated from k
obs
CH3OH]HNO3], where k
obs
= 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![$$\left {{\text{NO}}_2^ + } \right]^{ - 1} \left {{\text{CH}}_3 {\text{OH}}} \right]^{ - 1} $$](/content/8q054q1p455256vv/10874_2007_9091_Article_IEq3.gif) . The temperature dependence has also been parameterized for application to the atmosphere, but the small quantities of  present in aerosol particles will result in methyl nitrate production rates too small to be of significance under most atmospheric
conditions.
An erratum to this article can be found at |
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| Keywords: | Acid-catalyzed Aerosol chemistry Alcohol Nitration Sulfuric acid |
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