TiO2 Coating on SiO2 Nanosphere Supported Pd Catalyst for the H2-SCR of NO x in the Presence of Oxygen

A highly active Pd supported on TiO2 coatingon a SiO2 nanosphere (Pd/SiO2-TiO2(C))catalyst has been developed for the selective catalytic reductionof NO x by H-2 (H-2-SCR). The coating structure of TiO2 on the SiO2 nanosphere exerts an important effect on the catalytic performanceof the catalyst. This Pd/SiO2-TiO2(C)catalyst shows superior activity with 93.2% NO x conversion at 150 degrees C, and high tolerance to CO and H2O, which is significantly outperformed Pd supported on TiO2 particle (Pd/TiO2) catalyst. Compared with Pd/TiO2, Pd/SiO2-TiO2(C) has higherPd dispersion and smaller Pd particle size, more surface chemisorbedoxygen, and metallic Pd species, all of which contributed to the improvedperformance. In situ diffuse reflectance infrared Fourier transformspectroscopy (in situ DRIFTS) reveals that more reactive NO x , NH3, and NH4 (+) speciesformed on Pd/SiO2-TiO2(C), and the COpoisoning is mainly due to the slight inhibition of the formationof these reactive species. This research provides a promising strategyto design a superior H-2-SCR catalyst for the removalof NO x .