Mutual Sensitization of the Oxidation of Nitric Oxide and a Natural Gas Blend in a JSR at Elevated Pressure:  Experimental and Detailed Kinetic Modeling Study

Abstract

The mutual sensitization of the oxidation of NO and a natural gas blend (methane-ethane 10:1) was studied experimentally in a fused silica jet-stirred reactor operating at 10 atm, over the temperature range 800-1160 K, from fuel-lean to fuel-rich conditions. Sonic quartz probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses were used to measure the concentration profiles of the reactants, the stable intermediates, and the final products. A detailed chemical kinetic modeling of the present experiments was performed yielding an overall good agreement between the present data and this modeling. According to the proposed kinetic scheme, the mutual sensitization of the oxidation of this natural gas blend and NO proceeds through the NO to NO2 conversion by HO2, CH3O2, and C2H5O2. The detailed kinetic modeling showed that the conversion of NO to NO2 by CH3O2 and C2H5O2 is more important at low temperatures (ca. 820 K) than at higher temperatures where the reaction of NO with HO2 controls the NO to NO2 conversion. The production of OH resulting from the oxidation of NO by HO2, and the production of alkoxy radicals via RO2 + NO reactions promotes the oxidation of the fuel. A simplified reaction scheme was delineated: NO + HO2 --> NO2 + OH followed by OH + CH4 --> CH3 + H2O and OH + C2H6 --> C2H5 + H2O. At low-temperature, the reaction also proceeds via CH3 + O2 (+ M) --> CH3O2 (+ M); CH3O2 + NO --> CH3O + NO2 and C2H5 + O2 --> C2H5O2; C2H5O2 + NO --> C2H5O + NO2. At higher temperature, methoxy radicals are produced via the following mechanism: CH3 + NO2 --> CH3O + NO. The further reactions CH3O --> CH2O + H; CH2O + OH --> HCO + H2O; HCO + O2 --> HO2 + CO; and H + O2 + M --> HO2 + M complete the sequence. The proposed model indicates that the well-recognized difference of reactivity between methane and a natural gas blend is significantly reduced by addition of NO. The kinetic analyses indicate that in the NO-seeded conditions, the main production of OH proceeds via the same route, NO + HO2 --> NO2 + OH. Therefore, a significant reduction of the impact of the fuel composition on the kinetics of oxidation occurs.

Sensitizing effects of NOx on CH4 oxidation at high pressure

“…This interaction has been investigated for a wide range of fuels, including H 2 [3,4], CO [4][5][6][7], CH 2 O [3,8], CH 4 /natural gas [3,4,[9][10][11][12][13][14][15][16][17][18][19][20][21], C 2 hydrocarbons [4,12,[22][23][24], higher hydrocarbons [4,12,[25][26][27][28], and oxygenated hydrocarbons [29][30][31][32][33][34][35]. The sensitizing behavior is a result of interactions with the radical pool as well as direct reactions between NO x and stable species, e.g., H 2 , O 2 , CH 2 O, CH 4 , and C 2 H 6 .…”

“…Only a few of the previous studies were conducted above atmospheric pressure. Dagaut and coworkers investigated the mutual oxidation of CH 4 / natural gas and NO x in jet-stirred reactors at pressures up to 10 atm [18,19], while Sivaramakrishnan et al [21] extended the pressure range to 50 bar through shock-tube experiments (1000-1500 K, lean conditions). In the present work experimental data are obtained for the CH 4 /O 2 /NO x system under welldefined conditions in a high-pressure laminar flow reactor at pressures from 20 to 100 bar, moderate temperatures in the range of 600-900 K, and high dilution in N 2 .…”

Thermochemical properties for n‐propyl, iso‐propyl, and tert‐butyl nitroalkanes, alkyl nitrites, and their carbon‐centered radicals

“…61 and 40 kcal mol −1 , respectively [4][5][6][7][8]. The nitro alkanes and alkyl nitrites can release NO and NO 2 and can serve as catalysts in oxidation of hydrocarbons [9][10][11]. In this regard, nitro compounds have been widely studied by both experimental and theoretical methods [4][5][6][7][8]; nevertheless, the thermochemical data are surprisingly limited.…”

Determination of Nitric Oxide by Quenching Electro‐Chemiluminescence of Tris(2,2′‐Bipyridyl)ruthenium in Flow Injection Analysis

“…Voltammetry of NO did not show any proof of adsorption NO. The catalytic effect is conceivable in that NO consumes catalytically HO 2 · [28,29] which plays a main role in the ECL [23].…”