8. Ceria-based Mixed Oxide Nanoparticles for Diesel Engine Emission Control

One of the effective methods for the control of harmful emissions from diesel engines is the use of fuel-borne catalyst. Ceria is commonly used as a redox catalyst, and the catalytic activity of ceria decreases due to particle sintering, especially at high temperatures. The catalytic activity of ceria nanoparticle can be improved by doping it with transition metals such as zirconium, yttrium. A comparative study on the catalytic activity and various physicochemical properties of Ce_yZr_1−yO_2, Ce_yY_1−yO₂, and Ce_xZr_yY_1−x−yO₂ mixed oxide nanoparticles, synthesized by co-precipitation method, is presented in this chapter. The synthesized mixed oxide nanoparticles of ceria were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. The catalytic activity of ceria and its mixed oxide nanoparticles was compared by means of temperature-programmed reduction with H₂ (H₂-TPR) technique. The catalytic nanoparticle-dispersed diesel was prepared by mixing mixed oxide nanoparticles in diesel, with oleic acid as surfactant by means of ultrasonicator. Stability studies were done to optimize the concentration of catalytic nanoparticles in diesel for maximum stability. Engine studies on a four-stroke single-cylinder diesel engine show a reduction in the engine exhaust emissions, especially smoke, which agrees with the TPR study.