Start
Jul 25, 2013 - 17:00
End
Jul 25, 2013 - 18:00
Venue
Creativity Hall (Room 118) Chemical Engineering
Event Type
Speaker
Divesh Bhatia R & D Division Nalco Water India Ltd.
Title
Kinetic and modeling studies of lean NOx traps
Abstract : There has been a shift of focus towards diesel and lean burn engines for automobiles because of their higher fuel mileage. However NOx abatement is a challenging task under excess air conditions due to which alternate technologies for NOx reduction are in focus. One of these technologies is the NOx storage and reduction (NSR). It consists of two cyclic steps which occur on a lean NOx trap (LNT) catalyst: NOx storage during the fuel lean phase and NOx reduction/regeneration during the rich phase. A global kinetic model for NOx storage and reduction for the case of anaerobic regeneration with hydrogen was developed. The existence of two different types of BaO sites on the catalyst was proposed. The effluent concentrations and concentration fronts of the reactants and products within the monolith were predicted by the model providing insight into the mechanisms of regeneration and storage. It was shown that the NH3 formed upstream reacted with the stored NOx downstream of the H2 front. An analysis of the H2 concentration front showed the presence of more stored NOx in the front of the reactor. A simplified crystallite scale model was combined with a reactor scale model to study the effect of Pt dispersion and temperature on the regeneration behaviour of a LNT catalyst. The experimental data was explained by the localized stored NOx gradients in the BaO phase. The model predicted that the highest amount of NH3 was produced by the low dispersion catalyst at high temperatures by the high dispersion catalyst at low temperatures and by the intermediate dispersion catalyst at intermediate temperatures which was consistent with the experimental data. It was shown that NH3 is formed under conditions where NOx spill-over to the Pt/BaO interface is the rate limiting process. This finding could be used to design catalysts for getting the desired NH3 levels in the system.