DE19750178A1 - Greatly-enhanced catalytic oxidation of exhaust gases by three-way catalyst with electrical preheating - Google Patents

Abstract

As exhaust is produced, a small quantity of ozone is directed to the hot surfaces of the catalyst An Independent claim is included for equipment carrying out the process, in which before entering the catalyst chamber, the exhaust flow is passed through a layer with adsorptive properties. Preferred features: The catalyst is any form of noble metal catalyst in a porous matrix. The catalyst surface is electrically-heated.

Description

It is known that the exhaust gases such. B. from cars / trucks, a catalyst temperature of need over 300 ° C for a complete oxidation of the gaseous organic Impurities can take place. This means that after the engine starts, for at least about 3 minutes, the regulated catalyst is only at room temperature and therefore no effect achieved. Then when the hot engine exhaust fumes Temperature rises, the oxidation process begins and slowly reaches, after some Time, the full impact. The fact is that a method or apparatus for Cleaning the so-called cold start emission is not yet in sight. The reason is it is very difficult to get the required temperature of the catalyst bed as quickly as possible to achieve (within seconds). Is during the cold start the engine is idling and due to the displacement, the volume / min of exhaust gases, which come out of the exhaust pipe can be calculated very easily. One can Assume that on average every truck / car breathes about 1-2 cubic meters toxic exhaust gases contaminated only during the cold start phase. At the official Exhaust gas control method is called LEV and ULEV classes Motor vehicles. The total emission is added to the cold start emission certain mileage. By improving the injection mechanisms and Using other forms of precious metal catalysts, the Overall emissions decreased, but the cold start emissions, which we all inhale, remains almost the same. There are numerous attempts to reduce the cold start emission from No time to clean. It is, for example, from heating the catalysts by means of a gas burner, accumulation of cold start emissions in the bypass container, as well as electrical heating of additional catalysts, use of zeolite or Activated carbon adsorber modules, etc., reported. It is also reported that a additional injection of air or oxygen to improve the catalytic  Oxidation causes. But it is easy to see that there are some disadvantages to the Result in oxygen injection; d. H. the handling, the required amount and the Fact that oxygen in gaseous form is not very effective at the Is catalyst surface.

Our idea was to develop a system that uses active oxygen instead of air, metered in small amounts onto the catalyst surface. Since it's difficult if oxygen is generated in situ, we have the option of generating ozone examined. It is known that a UV light lamp, which UV light of about 365 micron emits, is able to generate ozone when moist air on the lamp flows past. By using simple electronics it is possible to get one Operate UV lamp with the 12 volt car battery. The lamp immediately generates ozone and if it is encased in a metal case, it is easy to do so Bring ozone to any desired location using a small pump. It is known, that ozone as such forms ozonides with unsaturated hydrocarbons and thereby a number of other organic compounds, such as. B. aldehydes etc., generated.

But we wanted the above Avoid unwanted reactions with ozone. This is us succeeded when we put ozone in contact with the precious metal catalyst bed. As a result, ozone is immediately split into active oxygen. In patent applications P-1 95 21 621.0 and P-43 19 844.9 are precious metal and other catalysts in different matrixes. It was found to be porous Store catalyst matrices in oxygen and this makes them effective Catalyst temperature significantly reduced. By using a small one electric heating device and a regenerable adsorber filter, as in the above Patent applications described, it is possible to start from cold start emissions to clean almost no time. Because the amount of ozone is very small and the fact that Ozone active oxygen cleaves the surface of catalysts almost immediately, the oxidation process proceeds much faster than with the supply of air or Oxygen gas. A device according to the above Process was constructed and with exhaust gas Tested from a car, equipped with a standard three-way catalytic converter. The Concentration of hydrocarbons, carbon monoxide and nitrogen oxides became too Reduced traces. In addition, no traces of ozone were found.

Claims (6)

1. Method and device for accelerating the oxidation rate of exhaust gases, preferably of cars / trucks equipped with three-way catalysts, characterized in that a small amount of ozone is passed to the hot surface of the catalyst simultaneously with the supply of exhaust gases. 2. The method according to claim 1, characterized in that the catalyst Any form of noble metal catalyst exists, which is in a porous matrix are introduced. 3. The method according to claim 1 and claim 2, characterized in that the Catalyst surface is heated electrically. 4. Apparatus according to claim 1, claim 2 and claim 3, characterized characterized in that the exhaust gas jet before it enters the catalyst chamber, is passed through a layer of a substance with adsorption properties. 5. The device according to claim 1, claim 2, claim 3, claim 4, characterized characterized in that the layer of substance with adsorption properties, is regenerated by means of electrical heating. 6. The device according to claim 1, claim 2, claim 3, claim 4, claim 5, characterized in that the required ozone is generated by a UV lamp becomes.