Synthesis of Vanadium Oxide Nanostructures and Their Performance in NH۳-SCR of NOx

چکیده مقاله

Nitrogen oxides (NOx), producing from combustion of fossil fuels at high temperatures, are a major air pollutant effecting the various environment problems. Selective catalytic reduction of NOx with ammonia (NH3-SCR) is a well-proven and effective technology to NOx removal. In NH3-SCR, ammonia has been employed as reductant which converts NOx into N2, N2O and H2O via catalytic reactions. Various catalysts are being developed for NH3-SCR of NOx. Recently, the great interest was assigned to synthesis of new one-dimensional nanostructure materials such as nanotubes, nanoroads and nanowires). The nanotubes are particularly attractive catalysts since it provides access to the three different contact regions: inner and outer surface as well as the tube ends. In the present work, vanadium oxide (VOx) nanostructures (nanotubes and nanorod) were synthesized by hydrothermal treatment using dodecylamine as template and evaluated for the selective catalytic reduction of NO with ammonia (NH3-SCR). The effect of essential factors affecting on morphology and activity of VOx nanostructures such as solvent type in reaction mixture and time of hydrolysis were studied. The obtained materials were characterized by XRD, SEM, TEM and BET. The results showed that the morphology and crystallinity of the VOx nanostructures were greatly influenced by the studied factors. The VOx nanorods (80-120 nm diameter and 1-4 µm length) were synthesized in 25 v/v% EtOH/(EtOH+H2O) and the open-ended multiwalled VOx nanotube (50-100 nm inner diameter, 110-180 nm outer diameter and 0.5-2 µm length) synthesized in 50 v/v% EtOH/(EtOH+H2O). VOx nanotubes performed the highest activity for NH3-SCR under a gas hourly space velocity of 12000 h-1 with NO conversion of 89% at 250 °C; it also had the N2 selectivity of 100%. The superior NH3-SCR activity of VOx nanotubes at low temperature is related to nanocrystalline structure, special nanotube morphology as well as high specific surface area.