State of the Active Component and Catalytic Properties of Modified Platinum-Titanium Catalysts for Selective Ammonia Oxidation

Abstract

Fundamental research is essential for developing new generation catalysts and optimizing the characteristics of existing catalytic systems, because it allows establishing key parameters determining the activity and selectivity of the studied reactions. In this work, the activity of supported platinum-titanium catalysts in the selective oxidation of ammonia is studied. The influence of modifying additives (potassium chloride and tungsten oxide) on the physicochemical and catalytic properties of the Pt/TiO₂ system is considered. Structural methods such as powder XRD and transmission electron microscopy showed that the studied catalysts contain highly dispersed platinum particles. The effect of oxidation-reduction treatment on the oxidation state of platinum on the surface of modified and unmodified catalysts is determined by ex situ X-ray photoelectron spectroscopy. It is shown that doping the samples by tungsten oxide and potassium chloride stabilizes the metallic platinum state and the oxidized Pt²⁺ state, respectively. The correlation between the active component state and catalytic properties shows that the activity of samples below 180 °C improves upon the introduction of tungsten oxide and their selectivity to molecular nitrogen below 250 °C increases upon the introduction of potassium chloride.