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. We developed a global kinetic model for NOx storage and reduction for the case of anaerobic regeneration with hydrogen. 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. 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.

ABOUT THE SPEAKER

Divesh Bhatia is a graduate in chemical engineering and currently working in the research and development division of Nalco Water India Ltd. He received B.Tech. and M.Tech. degree in Chemical Engineering from IIT Delhi in 2005 and Ph.D. degree in Chemical Engineering from University of Houston in 2009. He worked at Mercedes Benz Research and Development from 2010 till 2012, eventually as a technical lead. His research interests include modeling and simulation, catalysis and reaction engineering. He is a recipient of the “Star performer of the year” award at Mercedes Benz R&D, and ABCD award (Above and Beyond the Call of Duty award) at Nalco Water R&D.