Cold-Start Hydrocarbon Speciation and Trap Materials for Gasoline Engines

Efficient hydrocarbon (HC) trap materials have been developed to trap the major emitting HC compounds from gasoline direct injection engines. Online FTIR measurements on different test cycles and catalytic systems showed that AHC, C5 compounds, and CH4 were the most emitted species at cold-start phase (up to 100 sec). Making AHC and C5 as targets for improving the HC light-off, lab scale reactor set-up was established with toluene and iso-pentane feed pumping system along with propane-propene mixture. TGA screening experiments conducted with ex-situ toluene adsorption and the results revealed that BEA type materials have moderate to higher HC trapping temperature and HC storage capacity. In the present investigation, BEA-HS exhibited outstanding stability and trapping ability even after 850 °C hydrothermal aging. PGM and TM based BEA materials were evaluated for HC-TPD experiments with TWC gas composition. Interestingly, adsorption properties of the samples at various aging temperatures are well correlated with pore size and structure. Functionalized micro-pore materials with transition based metals showed substantial improvement on toluene desorption temperature. Based on these studies and the test results, advanced HC trap catalysts have been designed which demonstrated potential advantage over conventional TWC.