Modeling and flow reactor experiments were used to study the kinetics of NO
x
storage/release on a Pt/BaO/Al2O3 model catalyst. The mechanism for this concept can be divided into four steps: (i) NO to NO2 oxidation
on Pt, (ii) NO2 storage on BaO, (iii) NO
x
release, and (iv) NO
x
reduction to N2. In this paper, we have
focused on the first three steps. From the NO oxidation study on Pt/Al2O3 compared to Pt/BaO/Al2O3, we
observed that the presence of BaO decreases the formation of NO2. To test the importance of this step for
effective storage, experiments were performed with a Pt/Al2O3 catalyst placed before the Pt/BaO/Al2O3 catalyst.
This resulted in increased NO
x
storage for the combined system compared to the Pt/BaO/Al2O3 case. To
resolve the second and third steps, an experimental investigation of NO
x
storage/release on BaO/Al2O3 was
performed using only NO2 and N2 in the gas feed. We propose a kinetic model, which first includes adsorption
of NO2, which oxidizes the surface, followed by nitrate formation. Finally, NO3
-BaO−NO2, i.e., Ba(NO3)2,
is formed. By using the kinetic parameters from the NO oxidation on Pt/BaO/Al2O3 and the NO
x
storage on
BaO/Al2O3, a kinetic model was constructed to describe NO
x
storage/release experiments on Pt/BaO/Al2O3.
However, the rate for NO
x
release was increased when Pt was present, and the kinetic model could not accurately
describe this phenomenon. Therefore, the mechanism was modified by including a reversible surface spillover
step of NO2 between Pt sites and BaO sites. Further, experiments with NO2 exposure followed by a temperature
ramp with NO/N2 showed that the desorption behaviors from the BaO/Al2O3 and Pt/BaO/Al2O3 were
significantly different, which further supports the spillover mechanism. Finally, the models describing NO
x
storage on BaO/Al2O3 and on Pt/BaO/Al2O3 were successfully validated with independent experiments.
Computational fluid dynamics, CFD, has become an indispensable tool for many engineers. This book gives an introduction to CFD simulations of turbulence, mixing, reaction, combustion and multiphase flows. The emphasis on understanding the physics of these flows helps the engineer to select appropriate models to obtain reliable simulations. Besides presenting the equations involved, the basics and limitations of the models are explained and discussed. The book combined with tutorials, project and power-point lecture notes (all available for download) forms a complete course. The reader is given hands-on experience of drawing, meshing and simulation. The tutorials cover flow and reactions inside a porous catalyst, combustion in turbulent non-premixed flow, and multiphase simulation of evaporation spray respectively. The project deals with design of an industrial-scale selective catalytic reduction process and allows the reader to explore various design improvements and apply best practice guidelines in the CFD simulations.
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