Ind. Eng. Chem. Res. 2005, 44, 4523-4533
4523
Kinetic Experiments and Modeling of a Complex DeNOx System: Decane Selective Catalytic Reduction of NOx in the Gas Phase and over an Fe-MFI Type Zeolite Catalyst Leonid Vradman,*,† Moti Herskowitz,‡ Libor C ˇ apek,§ Blanka Wichterlova´ ,§ Roald Brosius,| and Johan A. Martens| Department of Chemical Engineering, Sami Shamoon College of Engineering, Beer-Sheva, Israel, Blechner Center for Industrial Catalysis and Process Development, Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel, J. Heyrovsky´ Institute of Physical Chemistry, Academy of Science of the Czech Republic, Prague, Czech Republic, and Centrum voor Oppervlaktechemie en Katalyse, Katholieke Universiteit Leuven, Leuven, Belgium
The reduction of NOx in the gas phase (in a NO-NO2-decane-water-O2 mixture) and over a Fe-MFI type zeolite catalyst was extensively studied under a wide range of temperatures, gas hourly space velocities, and concentrations. The Fe-MFI zeolite (Si/Al 12.5 and Fe/Al 0.31) was prepared by solid-state ion exchange. The decane selective catalytic reductions (decane-SCRs) of NO and NO2 were carried out with a reaction mixture consisting of 1000 ppm NOx, 300 ppm C10H22, 6.0% O2, and 0 or 12.0% H2O at gas hourly space velocity values of 15 000-60 000 h-1 and temperatures of 150-450 °C. Under the experimentally investigated reaction conditions, there was no N2 formation in the bulk gas phase. Water vapor had little effect on the N2 yield in decane-SCR of NOx. The kinetic description of the homogeneous system included reactions between NO2 and decane with the formation of NO, CO, and CO2 and a pseudocompound “C3H6O1.8” lumping all oxygenated, olefinic, and paraffinic hydrocarbon products. The heterogeneous system accounts for two distinct functions of the Fe-loaded zeolite catalyst: NO oxidation and SCR of NO2 with decane and C3H6O1.8, yielding N2, NO, CO, and CO2. This kinetic description yielded a good fit of experimental data. The rates of heterogeneous reactions were higher than the rates of homogeneous reactions by 1-3 orders of magnitude. Among catalytic reactions, the NO formation out of NO2 was the fastest reaction, which is the main reason for the relatively low nitrogen yield (
