Robert M. Sinkevitch

The dual state behavior of supported noble metal catalysts

In earlier NO reduction studies, difficulties in reproducing results with ruthenium catalysts were traced to some rather unusual pretreatment effects which were able to generate two states for ruthenium catalysts which differed in activity characteristics. This dual state behavior has subsequently been observed for other noble metal catalysts in a variety of reactions. The effect is most dramatic for the water-gas shift reaction, but was also observed for the CO-H2 reaction, ammonia decomposition, and nitric oxide reduction. It was found that sulfur contamination eliminated the effect for ruthenium but not for platinum and palladium catalysts. Chemisorption measurements have shown that the effect is not a simple function of metal loading or dispersion. A mechanism involving surface reconstruction and/or metal-support interaction is proposed.

Reactors for investigation of soot combustion on filter surfaces

Abstract Ceramic filters used to remove soot from the exhaust of combustion systems can be regenerated by intermittent combustion of the accumulated soot. Two reactors are described that allow investigation of the ignition and combustion phenomena that affect filter regeneration. The first is a laboratory reactor that was designed to allow measurements on undisturbed soot deposits with minimal loss of adsorbed hydrocarbons, which are shown to influence soot ignition and combustion. The second reactor is designed to be placed in the exhaust system of a diesel engine and allow direct visual observation of soot ignition and combustion. Results of several types of experiments performed with the reactors are presented.

A laboratory combustion study of diesel particulates containing metal additives

Etude au laboratoire de la combustion de particules de moteur diesel contenant des additifs metalliques

Oxidation of diesel particulates by catalyzed wall-flow monolith filters

Oxydation des particules emises par un moteur diesel dans un filtre monolithique avec catalyseur a ecoulement de paroi

Oxidation of diesel particulates by catalyzed wall-flow monolith filters. 2. Regeneration characteristics of platinum, lithium, and platinum-lithium catalyzed filters

Regeneration characteristics of Pt, Li, and Pt-Li catalyzed wall-flow monolith (WFM) filters were examined in a reactor mounted in the exhaust from a GM 4.3 L diesel engine. Regeneration rates were measured over a range of exhaust temperatures corresponding to various engine speeds and torques. A fresh 0.2 wt% Pt - 0.2 wt% Li filter regenerated much more rapidly than filters containing 0.2 wt% Pt, 0.4 wt% Pt, or 0.2 wt% Li. The data suggest that both Pt and Li operate as soot oxidation catalysts, with the Li following a redox mechanism proposed by McKee and Chatterji (Carbon 13, 381, 1975). Significant oxidation activity was observed with the fresh Pt-Li filter at temperatures as low as 350/sup 0/C, thus demonstrating activity at temperatures nearly within the normal operating range of light-duty GM diesel vehicles. The Pt-Li filter deactivated with time on stream due to reaction of lithium with SO/sub 2/ in the exhaust.