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Technical Paper

Stabilized Ruthenium Catalysts For NOx Reduction

Some of the problems encountered in the use of ruthenium as a NOx reduction catalyst are described. The major problem of volatilization in high temperature oxidizing atmospheres has been overcome by providing a stabilizing matrix for the ruthenium. The stabilized catalyst, however, does not have good CO and HC oxidizing performance, such as is required when the NOx catalyst is used for oxidation under cold start conditions. Coimpregnation of Pt and Ru is ineffective in improving this situation, and it was necessary to develop a novel procedure to improve catalyst oxidation activity. Engine dynamometer tests showed that the final catalyst performs well under all of the conditions to which it is subjected. The question which remains unanswered is the durability of the system.
Technical Paper

Nitrogen Oxides, Combustion, and Engine Deposits

REACTIONS of unsaturated fuel constituents with oxides of nitrogen, formed during combustion, play an important part in formation of engine deposits. Engine varnish, the organic binder in engine deposits, results in large part from reactions of nitrogen dioxide with gasoline constituents. Simplified kinetic studies indicate that nitrogen fixation and amounts of nitric oxide present in exhaust gases could be predicted. Tests have demonstrated that only under conditions leading to appreciable nitrogen fixation does heavy engine varnishing occur. Because commercial engine oils are fairly resistant to oxidation, it is likely that current deposit problems result from the nature of fuel and prevailing operating conditions. Under average driving, low-temperature operation, lean mixtures with consequent high nitrogen oxide content contribute much to varnish formation.
Technical Paper

Lean Mixture Lubrication of Two-Cycle Gasoline Engines

Combined efforts by oil companies and engine manufacturers have improved the overall efficiency and performance of two-cycle gasoline engines. One striking trend has been toward the use of leaner oil-fuel mixtures to accomplish lubrication. The use of less oil reduces smoking and air pollution (important in two-cycle automotive engine operation), reduces engine port deposits, preignition, and cost of operation. Experience has shown that the composition of the oil becomes increasingly important as its concentration in the fuel is reduced. Lean mixtures of some conventional oils are not satisfactory, and with all oils some lower concentration is reached where serious problems are encountered, such as lack of lubrication, increased engine wear, and decreased engine cleanliness.