The Impacts of Pd in BEA Zeolite on Decreasing Cold-Start NMOG Emission of an E85 Fuel Vehicle

In the development of hydrocarbon (HC) traps for E85 fuel vehicle emission control, the addition of palladium (Pd) to BEA zeolite was studied for trapping and decreasing cold-start ethanol emissions. BEA zeolite after a laboratory aging at 750°C for 25 hours released nearly all of the trapped ethanol as unconverted ethanol at low temperature, and some ethene was released at a higher temperature by a dehydration reaction. The addition of Pd to BEA zeolite showed a decrease in the release of unconverted ethanol emissions even after the lab aging. The release of methane (CH₄), acetaldehyde (CH₃CHO), carbon monoxide (CO), and CO₂ from Pd-BEA zeolite during desorption (temperature programmed desorption (TPD)) demonstrated that multiple ethanol reaction mechanisms were involved including dehydrogenation and decomposition reactions. The amount of Pd loading in BEA zeolite showed a diminished benefit toward eliminating unconverted ethanol release as the Pd loading increased above 0.2 wt% zeolite. Vehicle emission (with E85 fuel) test results also confirmed the benefits of Pd in zeolite in reducing cold-start non-methane organic gas (NMOG) emissions.