Effects of Feed Gas Composition on Fresh and Aged TWC-Coated GPFs Loaded with Real Soot

Artikel i vetenskaplig tidskrift, 2020

Catalyzed gasoline particulate filters (cGPFs) are one of the most promising technologies to meet future stringent gaseous and particulate emission limits for gasoline-powered vehicles. The successful adoption of this technology relies on several important properties including high filtration efficiency, low back-pressure, high conversion efficiency, and great durability compliance. Particularly in this work, the conversion efficiency and durability of model cGPF catalysts were studied under different feed temperatures and multicomponent feed gas mixtures. The samples consisted of soot-free and real soot-loaded GPFs coated with noble metals supported on alumina and Ce-Zr mixed oxides. Prior to testing, the samples were subjected to diverse hydrothermal aging conditions. Some physicochemical characterization techniques, including scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen physisorption, were employed to study the fundamental relations between the state of the samples and their catalytic properties. The results showed that the introduction of soot appeared to have both a positive and negative effect on the catalyst activity. The catalyst surface is masked by the introduction of soot, blocking active sites and inhibiting species conversion. At the same time, the exothermicity of the soot oxidation reaction increases the catalyst temperature, reducing the light-off temperature, for the severely aged samples. Besides the presence of soot, the catalyst aging considerably influences the reactions over cGPFs. In particular, the conversions of ethylene and toluene were more affected by the catalyst aging than CO, which became even worse in the presence of NO in the feed gas. The formation of side products (NH3 and N2O) over the cGPFs was also examined under diverse practical conditions.