NOx selective catalytic reduction at high temperatures with mixed oxides derived from layered double hydroxides

Mixed oxides derived from layered double hydroxides (LDHs) have been investigated as potential catalysts for the NOx removal at high temperatures. The best results were obtained with Co–Al mixed oxides derived from LDHs that are active at 750 °C in the presence of oxygen and water. These catalysts could reduce or/and decompose the NOx formed in the dense phase of the FCC regenerator, being deactivated at oxygen concentrations higher than 1.5%. Nevertheless this deactivation is not permanent and they would be regenerated after reduction with hydrogen at 530 °C. The influence of the layered double hydroxides (LDHs) preparation method on the catalyst activity was studied, observing that the activity of the catalyst depends on its chemical composition but it does not depend on the initial LDHs crystallinity, obtaining similar results independently of the synthesis method.