Spectroscopic Study on the Intermediates and Reaction Rates in the Oxidation of Levitated Droplets of Energetic Ionic Liquids by Nitrogen Dioxide
| Autor: | Michael Lucas, Tonya N. Jensen, Scott L. Anderson, Ralf I. Kaiser, Stephen J. Brotton |
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| Rok vydání: | 2018 |
| Předmět: |
Reaction mechanism
chemistry.chemical_element 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Nitrogen 0104 chemical sciences Reaction rate chemistry.chemical_compound symbols.namesake Reaction rate constant chemistry Ionic liquid symbols Physical chemistry Nitrogen dioxide Physical and Theoretical Chemistry 0210 nano-technology Raman spectroscopy Dicyanamide |
| Zdroj: | The Journal of Physical Chemistry A. 122:7351-7377 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.8b05244 |
| Popis: | To optimize the performance of hypergolic, ionic-liquid-based fuels, it is critical to understand the fundamental reaction mechanisms of ionic liquids (ILs) with the oxidizers. We consequently explored the reactions between a single levitated droplet of 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]), with and without hydrogen-capped boron nanoparticles, and the oxidizer nitrogen dioxide (NO2). The apparatus consists of an ultrasonic levitator enclosed within a pressure-compatible process chamber interfaced to complementary Fourier-transform infrared (FTIR), Raman, and ultraviolet-visible spectroscopic probes. First, the vibrational modes for the Raman and FTIR spectra of unreacted [BMIM][DCA] are assigned. We subsequently investigated the new structure in the infrared and Raman spectra produced by the reaction of the IL with the oxidizer. The newly produced peaks are consistent with the formation of the functional groups of organic nitro-compounds including the organic nitrites (RONO), nitroamines (RR'NNO2), aromatic nitro-compounds (ArNO2), and carbonitrates (RR'C═NO2-), which suggests that the nitrogen or oxygen atom of the nitrogen dioxide reactant bonds to a carbon or nitrogen atom of [BMIM][DCA]. Comparison of the rate constants for the oxidation of pure and boron-doped [BMIM][DCA] at 300 K shows that the boron-doping reduces the reaction rate by a factor of approximately 2. These results are compared to the oxidation processes of 1-methyl-4-amino-1,2,4-triazolium dicyanamide ([MAT][DCA]) with nitrogen dioxide (NO2) studied previously in our laboratory revealing that [BMIM][DCA] oxidizes faster than [MAT][DCA] by a factor of about 20. The present measurements are the first studies on the reaction rates for the oxidation of levitated ionic-liquid droplets. |
| Databáze: | OpenAIRE |
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