The impacts of Pd in BEA zeolite on decreasing cold start HC emission of an E85 vehicle

Lifeng  Xu, Research and Innovation Center, Ford Motor Company

The impacts of Pd in BEA zeolite on decreasing cold start HC emission of an E85 vehicle

Authors:

Lifeng Xu, Jason Lupescu, Jeffery Hepburn, Giovanni Cavataio, Kevin Guo, Paul Laing, Hungwen Jen and Rachael Harrington

During the development of HC traps for the E85 vehicle cold start HC emission control, a BEA zeolite was studied for trapping and decreasing ethanol emission. Fresh BEA zeolite has good ethanol capture efficiency and a large amount of trapped ethanol releases as ethylene with a well-known dehydrogenation mechanism. However, BEA zeolite deteriorated significantly after laboratory aging under a lab 4-mode cycle at 750^oC for 25 hours and most of the trapped ethanol was released at low temperatures. The Pd in BEA zeolite can capture ethanol and effectively decrease ethanol emission even after the same lab aging。 The ethanol dehydrogenation is no longer an important mechanism for BEA zeolite with Pd. The increase of Pd loading in BEA zeolite improves ethanol trapping efficiency, however, the efficiency levels off when the Pd loading is above 0.2wt%. The release timing and the quantities of methane (CH4), acetaldehyde (CH₃CHO), CO and CO2 during ethanol desorption in TPD demonstrated that multi ethanol reaction mechanisms are involved in trapping ethanol at Pd-BEA zeolite, which will be discussed in this presentation. Vehicle (E85 fuel) test results also confirmed the benefits of Pd in BEA zeolite in reducing cold start HC emissions.

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