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U.S. federal vehicle emission standards effective in 2007 require tight control of NOx and hydrocarbon emissions. For light-duty vehicles, the current standard of Tier 2 Bin 5 is about 0.07 g/mi NOx and 0.09 g/mi NMOG (non-methane organic gases) at 120,000 mi. However, the proposed future standard is 0.03 g/mi for NMOG + NOx (~SULEV30) at 150,000 mi. There is a significant improvement needed in catalyst system efficiencies for diesel vehicles to achieve the future standard, mainly during cold start. In this study, a less than 6000 lbs diesel truck equipped with an advanced urea Selective Catalytic Reduction (SCR) system was used to pursue lower tailpipe emissions with an emphasis on vehicle calibration and catalyst package. The calibration was tuned by optimizing exhaust gas recirculation (EGR) fuel injection and cold start strategy to generate desirable engine-out emissions balanced with reasonable temperatures.

Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. Using an accelerated aging procedure, a set of production exhaust systems from a 2011 Ford F250 equipped with a 6.7L diesel engine have been aged to an equivalent of 150,000 miles of thermal aging and metal exposure. These exhaust systems included a diesel oxidation catalyst (DOC), selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF). Four separate exhaust systems were aged, each with a different fuel: ULSD containing no measureable metals, B20 containing sodium, B20 containing potassium and B20 containing calcium. Metals levels were selected to simulate the maximum allowable levels in B100 according to the ASTM D6751 standard. Analysis of the aged catalysts included Federal Test Procedure emissions testing with the systems installed on a Ford F250 pickup, bench flow reactor testing of catalyst cores, and electron probe microanalysis (EPMA).

Diesel engines provide a solution for the reduction of carbon dioxide (CO2) from motor vehicles. For diesel engines, however, technology to reduce nitrogen oxide (NOx) emissions is essential. This report focuses on Urea - Selective Catalytic Reduction (SCR) as an aftertreatment system for NOx reduction. The NOx conversion performance of SCR catalyst depends on exhaust gas temperature and the NO2/NOX ratio. In order to raise the NO2/NOX ratio, it is essential to raise the temperature of oxidation catalyst. For these purposes, it is necessary to raise the temperature of oxidation catalyst and SCR catalyst to high level in order to enhance NOx conversion. Temperature rising is implemented by in-cylinder fuel injection (post-injection).

A diesel engine is possible solution for carbon dioxide (CO2) reduction from automobiles. However, it is necessary for a diesel engine vehicle to reduce nitrogen oxide (NOx) emission. Therefore, this research focused on a Urea-selective catalytic reduction (urea-SCR) system as an after-treatment system to convert NOx and proposes the control method of the urea-SCR system based on the output of an ammonia (NH3) sensor. By maximizing NH3 storage rate of the SCR, conversion performance is maximized. To maximize the NH3 storage rate, an NH3 sensor is installed downstream of the SCR. The amount of urea-solution is controlled to keep NH3 slip detected by the sensor. Thus, the NH3 storage amount in the SCR or the SCRF (SCR on filter) can be maximized. The estimation and the control of NH3 storage amount is also used to cause NH3 slip immediately. NH3 storage capacity changes with catalyst temperature. In a transient state, temperature distribution occurs in the SCR catalyst.