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NOx sorbate, or “trap”, catalysts have achieved >90% reduction of NOx from lean exhaust streams over a broad range of temperatures. Since diesel can be used as the reductant for NOx sorbate catalysts, the sorbate catalyst technology offers great potential for NOx control in a broad range of mobile diesel applications. Traditionally, the longevity of NOx sorbate catalysts in diesel exhaust applications has been limited by sulfur masking of NOx sorption sites. Two methods to control sulfur compounds and their associated effects will be presented here. Upstream sulfur sorbate, or “trap”, catalysts are used to control the rate of sulfur masking by diverting sulfur away from the NOx sorbate catalyst. Desulfation of NOx sorbate catalysts can lead to the removal of sulfur compounds from the catalyst and reactivation of NOx sorption sites. Data demonstrating sulfur control with both of these methods will be presented here.

A correlation between reflectance type smoke measurements and dry particulate concentrations in diesel exhaust is derived from first principles. The model has one free parameter; the mass-average diameter of the exhaust particulates. Data from the literature indicates that particulate diameters can vary depending upon the injection hardware, fuel properties, and combustion chamber design. Older engines typically have larger average particulate radii and run at higher smoke numbers. Using a simple linear relationship between smoke number and mass-averaged particulate diameter, a good match is obtained between the derived model and experimental data. As a further validation of the model, a technique is derived by which any correlation between smoke and particulate concentration can be validated with only a smoke meter, provided it has multiple draw capabilities. Using this novel technique, the correlation derived here is shown to be functionally correct.