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With the stringent China6 legislation implementation in 2020, Gasoline Particulate Filters (GPF) are widely applied to control Particulate Number (PN), THC, CO, and NOx emissions from gasoline engines. The typical GPF product in the market is usually coated with a Pd/Rh three-way catalyst (TWC) layer. In this work, a novel and cost-effective GPF was achieved through Pd substitution with lower price of Pt in a novel Pt/Rh coating technology. This novel Pt/Rh GPF was evaluated for back pressure under clean and soot loaded conditions, PN Filtration efficiency and TWC activity. When compared with the commercial product of Pd/Rh GPF, the novel Pt/Rh GPF had 15% lower clean BP contribution, 25% lower back pressure with 2 g/L soot loading, while achieving equivalent PN filtration efficiency. The TWC activity of this novel Pt/Rh GPF was investigated after multiple aging including Four Mode bench aging and 1050 °C oven aging.

Natural gas (NG) engines have attracted increasing attention in the heavy duty (HD) vehicle market as an alternative to conventional diesel fuel often due to the abundance and low price of NG. However, it is challenging to meet the increasingly stringent China VI legislation, particularly for hydrocarbons (mainly CH4), carbon monoxide (CO), nitrogen oxides (NOx) and ammonia (NH3). In this work, approaches were explored in which a gasoline three-way catalyst (TWC) was modified through optimization of promoters, OSC materials, and catalyst structure. The optimized TWC was evaluated in a laboratory reactor and with a HD stoichiometric NG engine. Lab reactor results showed that promoters can improve CH4 light off performance with T50 decreases of 20 oC and 13 oC for the fresh and aged catalyst respectively.

Emission control systems combining NOx Adsorber catalysts with Selective Catalytic Reduction catalysts (NAC + SCR) offer potential performance advantages for NOx control under lean conditions compared to systems consisting of only one of these technologies. The combined systems, however, also present new catalyst design challenges. In contrast to NAC-only systems, formation of NH₃ over the NAC component under NOx regeneration conditions is a desirable feature in the combined (NAC + SCR) system. The SCR component in the combined system needs to be as thermally durable as the stand-alone SCR technology and also has to withstand repeated high-temperature lean/rich transients encountered during periodic desulfation of the upstream NAC component. In this study, advanced NAC and SCR components were developed specifically for the combination system. The advanced NAC component exhibited a wider operating temperature window and higher NH₃ generation activity at reduced PGM loading.

Selective Catalytic Reduction (SCR) catalysts have been demonstrated as effective for controlling NOx emissions from diesel engines, maintaining high NOx conversion even after the extended high temperature exposure encountered in systems with active filter regenerations. As future diesel emission regulations are expected to be further reduced, packaging a large volume of SCR catalysts in diesel exhaust systems, along with DOC and particulate filter catalysts, will be challenging. One method to reduce the total volume of catalysts in diesel exhaust systems is to combine the SCR and DPF catalysts by coating SCR catalyst technology on particulate filters. In this work, engine evaluation of SCR coated filters has been conducted to determine the viability of the technology. Steady-state engine evaluations demonstrated that high NOx conversions can be achieved for SCR coated filters after high temperature oven aging.

NOx adsorber catalyst technology has been successfully applied on diesel vehicles to enable them to satisfy stringent NOx emission regulations. One limitation of this technology is the requirement to regularly desulfate the adsorber to maintain high NOx conversion efficiency. In addition to adding significant engine and calibration complexity, these high temperature desulfation events accelerate the thermal degradation of the exhaust system components. Minimization of the severity and the frequency of the desulfation events is highly desirable. Laboratory studies to understand desulfation processes and to identify improved NOx Adsorber washcoat compositions are described. These studies led to a new generation of NOx adsorber catalysts with reduced desulfation temperatures, faster desulfation rates and enhanced low-temperature activity. The new generation of catalysts also enabled the potential for PGM thrifting, especially for applications with low engine- out NOx emissions.

Selective catalytic reduction (SCR) of NOx by NH3 is under intensive development as a technology to enable diesel engines to meet stringent NOx emission regulations. Cu/zeolite SCR catalysts are leading candidates because of their ability to catalyze NOx reduction at the low temperatures encountered on many diesel vehicles. However, both engine evaluation and laboratory studies indicated that commonly available Cu/zeolite SCR catalysts did not have sufficient thermal stability to maintain performance during the full useful life of a vehicle (with steady-state NOx conversion decreasing ~ 10% over 64 hours of hydrothermal aging at 670 °C). Characterization of aged Cu/zeolite catalysts revealed that the loss of zeolite acidity was the main deactivation mechanism; while the zeolite support maintained its framework structure and surface area after aging. Improvement of the hydrothermal stability of the acid sites resulted in a new generation of SCR catalysts.

Within the next decade, all light-duty vehicles in the United States will be required to meet Tier 2 or LEV 2 tailpipe emission standards. As emission standards have tightened over time catalyst systems have increased in cost. The factors that have contributed to the growth in cost include increases in both precious metal content and catalyst volumes. Calibration strategy, catalyst, and substrate technology improvements have also enabled previous emission standards to be met. The recent dramatic fluctuations in precious metal price, coupled with the increasing desire to reduce system cost, have led catalyst companies to develop converter technologies containing decreasing amounts of precious metal, and still meet Tier2/LEV2 standards. In this paper the development of a novel, near base metal, catalyst technology is described. The effects of precious metal support type and catalyst preparation method are reported using model engine bench and vehicle tests.

FTP hydrocarbon emissions were measured on a sport utility vehicle comparing two catalyst systems. One system consisted of a close-coupled three-way catalyst and an underbody catalyst-only version of a hydrocarbon trap catalyst. The other system consisted of the same closed-coupled catalyst and underbody hydrocarbon trap catalysts. Thus, these systems compared a non-hydrocarbon trap system and a hydrocarbon trap catalyst system. Fresh and 50-hour aged testing showed that the hydrocarbon emissions were approximately 10% lower for the hydrocarbon trap catalyst system. When an air pump was used to inject air into the exhaust system, the hydrocarbon emissions of the hydrocarbon trap catalyst system were approximately 20% lower than the non-trap system. Hydrocarbon speciation demonstrated that the magnitude of the benefit of the hydrocarbon trap catalyst system was related to the characterization of the blend of hydrocarbon species in the exhaust after the close-coupled catalysts.

As one method of meeting current and future emission regulations on vehicles, automakers have increased PGM loadings in three-way catalysts. Engine dynamometer and FTP testing after accelerated engine agings were performed to compare current Pd:Rh and Pt:Rh catalysts with new Pd:Rh and Pt:Rh catalysts. This comparison demonstrated that enhanced three way performance can be obtained in the new catalysts with reduced Pd loadings or with the use of Pt:Rh instead of Pd:Rh. These improved catalysts will reduce the demand for high PGM loadings as well as provide flexibility in the PGM combinations used in exhaust systems.