Descargar Libro: Selective Catalytic Reduction Of Nitrogen Oxides Using Exchange Zeolites As Catalysts

Nitrogen oxides are one of the main pollutants of air. These oxides are a serious risk for health and very dangerous for environmental. Within the used techniques to control the NOx emissions stand out selective catalytic reduction, using ammonia or hydrocarbons as reductant agent. Zeolites are one of the most promising catalysts and between the zeolites, ZSM-5, mordenite and beta. Due to that, and taking advantage of our Department, we plan an investigation run to SCR of NOx using exchanged zeolites as catalysts. First of all, a base catalyst was selected taking as reference zeolites ZSM-5 and mordenite. Different active metals were using (copper, cobalt, nickel, manganese and iron). We studied the sodium and acid form of the zeolite and the temperature and ion-exchange degree. We obtained catalysts with higher catalytic activity using sodium forms than acid ones. When copper was used in sodium zeolites, we observed that an increase of the ion-exchange temperature results in an increase of the metal content in the catalysts, and as a consequence, an increase in the yield. When cobalt was used, we obtain a very active catalyst with an only ion-exchange. After a second ion-exchange a drop of yield was observed. With nickel when a second exchange was used, we obtained a decrease of the temperature of maximum yield when increased the metal content, without loss of crystallinity. When manganese and iron were used, we obtained catalysts with lower activity than the previous ones. With these results cobalt and nickel were selected for a study using cocations (Ag, Ca, Pd). In this study we investigated the resistance to deactivation in presence of poisons as water and SO2. We obtain catalyst with high capacity of recover activity (80% of initial activity after regeneration).

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