Benefits of Pd Doped Zeolites for Cold Start HC/NOx Emission Reductions for Gasoline and E85 Fueled Vehicles

Effects of CO and H2O Co-Feed on the Adsorption and Oxidation Properties of a Pd/BEA Hydrocarbon Trap

“…The hydrocarbon-containing gas stream was switched from the bypass to the reactor at t = 50 s. The summarized uptake capacities are listed in Table 1. The trend with respect to H2O is in good agreement with Xu et al [20], as we observe some ethylene uptake in the presence of H2O, however less than that observed in the dry case. Ethylene uptake occurs over both Brønsted acid sites and cationic Pd.…”

“…Kang et al found that the addition of Ag to the framework could enhance the trapping capacity of BEA towards ethylene, however these improvements were completely lost in the presence of water [15]. The addition of Pd to the framework however gives some resistance to water inhibition of ethylene adsorption, as reported by Xu et al [20].…”

“…Additionally, in the high oxygen environment of diesel exhaust, the catalytic oxidation supports regeneration of the hydrocarbon trap, oxidizing residual hydrocarbon species. This can be important, as for example ethylene and propylene are known to undergo oligomerization reactions involving zeolite Brønsted acid sites which can lead to catalyst deactivation [20,22].…”

NOx and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features

“…Olefins are known precursors of coke and oligomers. ,, Earlier studies have shown that propene and ethylene can undergo oligomerization reactions involving the zeolitic Brønsted acid sites. , Furthermore, olefins can be reformed from the cracking of higher molecular weight HCs. , Consistent with our data, earlier work from Ghosh and Kevan describes the dimerization of ethylene during its contact with Pd-exchanged Na-X and Ca-X zeolites. Likewise, van den Berg et al provided infrared evidence that ethylene is readily polymerized on H-ZSM-5 at room temperature.…”

“…Pd-exchanged, eight-membered ring SSZ-13 (0.34 nm pore size) is considered the best NO trapping material, ,,,− affording excellent thermal stability and high, if not complete, Pd cation dispersion. Pd-exchanged BEA has both NO and HC trapping capability. ,− The 12-membered ring BEA (0.65 nm pore size) provides excellent long-chain and short-chain HC trapping through a respective combination of the pore structure and surface acidity. ,− The OC, with its equimass mixture of Pt and Pd, provides excellent oxidation activity with Pd more active toward CO oxidation and Pt toward NO and HC oxidation . CeO 2 is a well-known oxygen storage material that provides enhanced oxygen by spillover to the Pt and Pd crystallites, mitigating site blocking by CO , and/or NO.…”