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Ammonia is one of the most useful compounds that react with NOx selectively on a catalyst, such as V2O5-TiO2, under oxygen containing exhaust gas. However ammonia cannot be stored because of its toxicity for the small power generator in populated areas or for the diesel vehicles. A new concept for NOx reduction in diesel engine using ammonia is introduced. This system is constructed from the hydrogen generator by fuel reformer, the ammonia synthesizer, SCR catalyst for NOx reduction and the gas injection system of reformed gas into the cylinder. Experimental results show that, the SCR catalyst provides a very high rate of NOx reduction, reformed gas injection into cylinder is very effective for particulate reduction. WHEN CONSIDERING INTERNAL COMBUSTION ENGINES of the 1990's the question of how to harmonize the engine with the natural environments is one of the greatest problems. The internal combustion engine changes a substance into energy via its explosive combustion.

Sulfur storage/discharge behavior on a flow-through type oxidation catalyst (FTC) was investigated by engine dynamometer tests and laboratory tests, and the following results were obtained. In FTC wherein active Al2O3 was used as a substrate for supporting catalytic components, sulfur was stored in the form of aluminum sulfate in high temperature region while sulfate were adsorbed or adhered to the catalyst surface layer to be stored thereon in low temperature region. Although aluminum sulfate formed in high temperature region was relatively stable, sulfate stored in low temperature region were desorbed easily when the temperature rose. Therefore, it was attempted to optimize the substrate deposited catalytic components. And, FTC which would inhibit adsorption of sulfate was achieved successfully.

The reduction behavior of diesel particulate and SOF by flow-through type oxidation catalysts was investigated under steady and dynamic engine conditions using a current fuel (S content:0.38 wt%) and a low sulfur fuel (S content:0.04 wt%). Each catalyst gave 40 - 90% SOF reduction at exhaust gas temperatures between 100°C to 500°C. This SOF reduction behavior is explained as follows. SOF is adsorbed or adhered on the catalyst surface at the lower temperatures and is decomposed at the higher temperatures. Pt only load catalyst which has high SO2 oxidation ability resulted in a low total particulate reduction due to high sulfate formation at higher temperatures even when the low sulfur fuel was used. It has been shown that flow-through type oxidation catalyst with low SO2 oxidation ability will offer a practical exhaust gas treatment method for 1990's improved diesel engines. 50 - 60% SOF reduction and 40 - 50% total particulate reduction has been proved to be possible.

Various CTOs have been tested at inlet gas temperature of 600°C, nearly muximum output operation on Bench Engine Dynamometer Unit with 2.8 - 6.6 liter D.I. engine. Base metals promoted CTO are found to be deteriorated unexpectedly through the test conditions mentioned above. On the other hand, noble metal promoted CTO showed good durability against such full load operation condition. The problem arised from noble metal promoted CTO is evolution of sulfur trioxide at much higher concentration than from base metals promoted CTO. It is concluded that sulfur content in diesel fuel should be reduced as low as possible, such as to current gasoline level to use noble metal promoted CTO. Tow types of particulate trap structure, wall-flow monolith (WFM) and ceramic foam have been evaluated. These carriers have trapped ashes from lubricating oil in a comparable efficiency to their particulate trap efficiency.