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In the present study, a bench-flow reactor is used to perform lean/rich thermal cycling on model “Ba+K” LNT catalysts at temperatures of 700, 800, 900 and 1000°C using simulated diesel exhaust gases. Deterioration of NOx performance is measured and the deactivation mechanisms of thermally-aged “Ba+K” LNTs are identified using characterization techniques such as TEM, XRD and EPMA. Results indicate that the deterioration is minimal at 700 and 800°C, however, at aging temperatures exceeding 800°C the severity of thermal aging depends on aging temperature as well as number of aging cycles.

Due to increasingly stringent emissions regulations, Lean NOx Trap (LNT) catalysts are being researched as a potential solution for diesel engine emissions reduction. LNTs are practical for diesel NOx reduction due to their ability to reduce NOx from the O2 rich environment produced by diesel engines. LNTs function by storing NOx on the catalyst surface during efficient lean operation then, under rich conditions, releasing and reducing the trapped NOx. One method of producing this rich environment which regenerates a LNT involves manipulating the fuel injection parameters and throttling the air intake. This process is called in-cylinder regeneration. Experiments will be described here in which a 1.7 L common rail diesel engine has been used to regenerate LNTs at various stages of sulfur exposure, a known poison of the LNT.

We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel-powered hybrid and plug-in hybrid vehicles (HEVs and PHEVs). The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of commercially available Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust.

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).

Thermal conductivity detection has long been used in gas chromatography to detect hydrogen and other diatomic gases in a gas sample. Thermal conductivity instruments that are not coupled to gas chromatographs are useful for detecting hydrogen in binary gas mixtures, but suffer from significant cross-interference from other gas species that are separated when the detector is used with a gas chromatograph. This study reports a method for using a commercially-available thermal conductivity instrument to detect and quantify hydrogen in a diesel exhaust stream. The instrument time response of approximately 40 seconds is sufficient for steady-state applications. Cross-interference from relevant gas species are quantified and discussed. Measurement uncertainty associated with the corrections for the various species is estimated and practical implications for use of the instrument and method are discussed.

Phosphorous in diesel exhaust is derived via engine oil consumption from the zinc dialkyldithiophosphate (ZDDP) oil additive used for engine wear control. Phosphorous present in the engine exhaust can react with an exhaust catalyst and cause loss of performance through masking or chemical reaction. The primary effect is loss of light-off or low temperature performance. Although the amount of ZDDP used in lube oil is being reduced, it appears that there may is a minimum level of ZDDP needed for engine durability. One of the ways of reducing the effects of the resulting phosphorous on catalysts might be to alter the chemical state of the phosphorous to a less damaging form or to develop catalysts which are more resistant to phosphorous poisoning. In this study, lube oil containing ZDDP was added at an accelerated rate through a variety of engine pathways to simulate various types of engine wear or oil disposal practices.

As interest has grown in diesel emissions and diesel engine aftertreatment, so has the importance of analyzing all components of the exhaust. One of the more costly and difficult measurements to make is the collection and analysis of semivolatile organic compounds (SOCs) in the exhaust. These compounds include alkane and alkenes from C12-C24, and the 2-5 ring polycyclic aromatic hydrocarbons (PAH). These compounds can be present in both the particulate (i.e. on the filter) and gaseous phase, and cannot be collected with bag samples. Typically, a sorbent is used downstream of the particulate collection filters to collect these compounds. Sorbent phases include polyurethane foam (PUF), Tenax™, XAD-type resins, and activated carbon. The SOCs are removed from the sorbent either by solvent extraction (PUF and XAD) or thermal desorption (Tenax™ and activated carbon). Each of these methods have advantages and disadvantages.

The DOE Office of Heavy Vehicle Technologies (OHVT) and its predecessor organizations have maintained aggressive projects in diesel exhaust aftertreatment since 1993. The Energy Policy Act of 1992, Section 2027, specifically authorized DOE to help accelerate the ability of U. S. diesel engine manufacturers to meet emissions regulations while maintaining the compression ignition engines inherently high efficiency. A variety of concepts and devices have been evaluated for NOx and Particulate matter (PM) control. Additionally, supporting technology in diagnostics for catalysis, PM measurement, and catalyst/reductant systems are being developed. This paper provides a summary of technologies that have been investigated and provides recent results from ongoing DOE-sponsored R&D. NOx control has been explored via active NOx catalysis, several plasma-assisted systems, electrochemical cells, and fuel additives.

This paper demonstrates the potential for fast absorption spectroscopy measurements in diesel-engine exhaust to track H2O concentration transients. Wavelength-agile absorption spectroscopy is an optical technique that measures broadband absorption spectra between 10 kHz and 100 MHz. From these measured spectra, gas temperature and absorber concentrations can be determined. We introduce a laser spectroscopy system for high speed (10 μs) diesel exhaust measurements in the presence of significant particulate matter. The sensor can be broadly applicable for understanding the dynamics of EGR distribution, cycle-to-cycle stability, cylinder-to-cylinder charge uniformity, and NOX regeneration strategies. The method precision is 10% and 5%, for individual 10-μs measurements and 2-ms averaged measurements, respectively. The sensitivity or detection limit of the measurement is 0.5% H2O.