Insights over Titanium Modified FeMgOx Catalysts for Selective Catalytic Reduction of NOx with NH3: Influence of Precursors and Crystalline Structures

Titanium modified FeMgO x catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO 4 and Mg(NO 3) 2 as precursors exhibited enhanced catalytic activity from 225 to 400 °C, with a maximum NO x conversion of 100%. Iron oxides existed as γ-Fe 2O 3 in this catalyst. They exhibited highly enriched surface active oxygen and surface acidity, which were favorable for low-temperature selective catalytic reduction (SCR) reaction. Besides, it showed advantage in surface area, spherical particle distribution and pores connectivity. Amorphous iron-magnesium-titanium mixed oxides were the main phase of the catalysts using Fe(NO 3) 3 as a precursor. This catalyst exhibited a narrow T 90 of 200/250–350 °C. Side reactions occurred after 300 °C producing NO x, which reduced the NO x conversion. The strong acid sites inhibited the side reactions, and thus improved the catalytic performance above 300 °C. The weak acid sites appeared below 200 °C, and had a great impact on the low-temperature catalytic performance. Nevertheless, amorphous iron-magnesium-titanium mixed oxides blocked the absorption and activation between NH 3 and the surface strong acid sites, which was strengthened on the γ-Fe 2O 3 surface. View Full-Tex