Optimization of NOx selective catalytic reduction in presence of iso-butane and 02 using Fecontaining ZSM-11 zeolites by multivariate analysis.

Abstract

The nitrogen oxides reduction is a problem that the environmental catalysis still tries to solve. Thus, for this problematic, the processes can be grouped in three general lines of work: minimization of the production of NOx; direct decomposition of NO to N2 + O2, and selective catalytic reduction (SCR). Fe-ZSM-5 has in recent times received much attention in catalysis research because of its promising activity in the decomposition or selective reduction of nitrous oxide. Fe-ZSM-11 zeolites, prepared by novel sol-gel process with Fe2+ and/or Fe3+ as active sites incorporated by reproducible post-synthesis methods were obtained. We reported the relationship between the catalytic activity and the nature of the active sites [1]. The experiment design - response surface methodology is used in this work to optimize the NOx selective catalytic reduction to N2 using the above cited catalyst. The main objective is to define the response surfaces, finding the best combination of different parameters in order to optimize the process, for this reason, the experiments design methodology was applied reducing the operation costs, achieving efficiency and effectiveness in the process. The application of this methodology leads us to a better understanding of the influence of the different factors such as: number and strength of the acid sites, Fe2+/Fe3+ relation, [NO3*] and [NO2*] adsorbed intermediates, the concerted reaction mechanism proposed in the previous work, and the effect of the reaction temperature and their interactions. The statistic model applied in this work is a powerful tool to interpret the overall process from the multivariate parameters. The goal of the present work would be to identify the key-factors to optimizing the best operation conditions and catalysts characteristics, which are responsible for the enhanced performance of Fe-zeolites and thereby to corroborate with even better catalyst formulations. According to the statistic methodology applied, the best operation conditions and catalysts characteristics can be identified, allowing us to re-design the catalyst to enhance the NOx conversion and N2 and CO2 selectivity at optimum reaction temperature.