REACTION OF DIMERIZED NOX (X = 1 OR 2) WITH SO2 IN A RESTRICTED SLIT-SHAPED MICROPORE SPACE

The reaction of dimerized NO or NO2 with SO2 in a slit-shaped micropore of alpha-FeOOH dispersed activated carbon fiber (ACF) at 273-373 K was examined using IR spectroscopy, alpha-FeOOH particles on ACF were ultrafine and strongly interacted with the carbon surface as examined by EXAFS and XPS. The micropore width of the ACF was 0.9 nm irrespective of dispersion of alpha-FeOOH by high-resolution N2 adsorption measurements. Significant amounts of NO molecules can be adsorbed in the micropore in the form of a dimer and react with adsorbed SO2 molecules in the micropore to produce N2O. The effects of reaction temperature, gas composition of NO and SO2, and dispersion of alpha-FeOOH on the N2O formation were examined; the reaction was governed by the amount of NO adsorption in the micropore. The N2O formation arose from the disproportionation reaction of the dimerized NO to N2O and NO2 (3(NO2) = 2NO2 + 2N2O), where coexisting SO2 enhanced the reaction through depletion of NO2 by the reaction of NO2 + SO2 = NO + SO3. Formation of SO3 in the micropore was confirmed by diffuse reflectance FTIR measurement. In the case of the reaction of the dimerized NO2 with SO2 in the micropore, also N2O and SO3 were produced via intermediate (NO)2. Thus, the slit-shaped micropore can induce the high-pressure reaction of the disproportionation reaction of (NO2) even under moderate conditions.