Starch bio-template synthesis of W-doped CeO catalyst for selective catalytic reduction of NO with NH: influence of ignition temperature.

A novel tungsten-doped CeO catalyst was fabricated via the sweet potato starch bio-template spread self-combustion (SSC) method to secure a high NH-SCR activity. The study focuses on the influence of ignition temperature on the physical structure and redox properties of the synthesized catalyst and the catalytic performance of NO reduction with NH. These were quantitatively examined by conducting TG-DSC measurements of the starch gel, XRD analysis for the crystallites, SEM and TEM assessments for the morphology of the catalyst, XPS and H-TPR measurements for the distribution of cerium and tungsten, and NH-TPD assessments for the acidity of the catalyst. It is found that the ignition temperature shows an important role in the interaction of cerium and tungsten species, and the optimal ignition temperature is 500 °C. The increase of ignition temperature from 150 °C is beneficial to the interactions of species in the catalyst, depresses the formation of WO, and refines the cubic CeO crystallite. The sample ignited at 500 °C shows the biggest BET surface area, the highest surface concentration of Ce species and molar ratio of Ce/(Ce+Ce), and the most abundant surface Brønsted acid sites, which are the possible reasons for the superiority of the NH-SCR activity. With a high GHSV of 200,000 mL (g h) and the optimal ignition temperature, CeWO-500 can achieve a steadily high NO reduction of 80% or more at a lowered reduction temperature in the range of 250~500 °C.