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Passive in-line catalyzed hydrocarbon (HC) traps have been used by some manufacturers in the automotive industry to reduce regulated tailpipe (TP) emissions of non-methane organic gas (NMOG) during engine cold-start conditions. However, most NMOG molecules produced during gasoline combustion are only weakly adsorbed via physisorption onto the zeolites typically used in a HC trap. As a consequence, NMOG desorption occurs at low temperatures resulting in the use of very high platinum group metal (PGM) loadings in an effort to combust NMOG before it escapes from a HC trap. In the current study, a 2.0 L direct-injection (DI) Ford Focus running on gasoline fuel was evaluated with full useful life aftertreatment where the underbody converter was either a three-way catalyst (TWC) or a HC trap. A new HC trap technology developed by Ford and Umicore demonstrated reduced TP NMOG emissions of 50% over the TWC-only system without any increase in oxides of oxygen (NOx) emissions.

An investigation into the design, development and evaluation of a “new” washcoat technology family that enables significant reductions in rhodium usage levels has been concluded. These findings were demonstrated on three vehicle applications utilizing different calibration A/F control strategies. Additional testing investigated optimal Rh placement on a two brick catalyst system and the impact on FTP and US-06 test cycles. This study concludes with an evaluation of full useful life aged catalysts tested on 6 and 8 cylinder applications that are shown to have met Bin 4 FFV and ULEVII emission standards.

In-line hydrocarbon (HC) traps are not widely used to reduce HC emissions due to their limited durability, high platinum group metal (PGM) concentrations, complicated processing, and insufficient hydrocarbon (HC) retention temperatures required for efficient conversion by the three-way catalyst component. New trapping materials and system architectures were developed utilizing an engine dynamometer test equipped with dual Fourier Transform Infrared (FTIR) spectrometers for tracking the adsorption and desorption of various HC species during the light-off period. Parallel laboratory reactor studies were conducted which show that the new HC trap formulations extend the traditional adsorption processes (i.e., based on physic-sorption and/or adsorption at acid sites) to chemical reaction mechanisms resulting in oligomerized, dehydro-cyclization, and partial coke formation.

Passive hydrocarbon traps (“HCT”) are limited in performance when installed in an oxygen deprived location, such as an underfloor that is downstream of a CC TWC. An OEM 1.0L close-coupled converter in a 1.4L turbo hybrid PZEV calibrated vehicle was replaced with a 1.24L HC trap. The HC trap consisted of a zeolytic storage layer beneath a Pd/Rh containing three-way catalyst layer. The UF converter was upgraded with a newer TWC technology. The HC trap and UF TWC were engine aged to simulate 150,000 miles, or full useful life conditions. Criteria for accelerated engine aging of the HC trap were selected based on the vehicle application’s peak operating bed temperatures in the field. Vehicle FTP and US-06 tests were conducted on an all-wheel drive dyno which facilitated normal hybrid powertrain operation. A SULEV20 engineering target for FTP nMHC+NOx emissions was met with the full useful life aged CC HC Trap (“HCT”) system, using a PGM amount that was lower than the OEM design.

A 1.0 L underfloor converter of a 1.4 L PZEV calibrated vehicle was replaced with a 1.26 L HC trap and a 1.26 L SCR catalyst. The HC trap consisted of a zeolitic storage layer beneath a three-way catalyst layer. A newly developed catalyzed HC trap technology containing Pd/Rh was used in the current study. Increased trapping efficiency and conversion was assigned to rapid and efficient polymerization of small alkenes and aromatics coupled with more efficient combustion before release. The new trap features include the presence of strong Brønsted acidity, precious metals such as Pd and a base Mn+ redox active metal. The HC trap was followed by an SCR catalyst for NOx clean-up. The production close-coupled catalyst and replacement underfloor catalysts (HC trap and SCR) were aged on a combination of rural and highway roads for 150,000 miles. Peak bed temperatures during road aging of the HC Trap and SCR catalyst were approximately 600 °C.