METHOD FOR DETECTING THE DEGREE OF AGING OF CATALYTIC CONVERTERS

Abstract

The invention is directed to a method for determining the state of aging of a catalytic converter (2). The disclosed method functions in a non-contacting manner as resonances formed when the catalytic converter (2) located in a housing is excited with high-frequency electromagnetic waves are analyzed.

Claims

1. A method for the noninvasive detection of the degree of aging of an automotive exhaust gas converter which is located in a metallic catalytic converter housing, via emission of an alternating electromagnetic field and detecting the same, wherein the adsorption of water on the catalyst surface is determined using certain resonance characteristics at a catalyst temperature of <200 C., and the degree of aging of the catalytic converter is thereby inferred.

2. The method according to claim 1, characterized in that a temperature of >50 C. is used.

3. The method according to claim 1, characterized in that an exhaust gas mixture that contains 3-20% by volume water is provided during measurement.

4. The method according to claims 1, characterized in that those resonance characteristics were used which were selected from the group comprising the resonance frequency, amplitude, quality of the resonator (Q), losses, the parameters of the scatter matrix S.sub.ij, and quantities based thereupon (also at different frequency ranges).

5. The method according to claim 1, characterized in that an antenna is used that is located in a metallic catalytic converter housing.

Description

EXAMPLE

[0019] FIG. 1 shows the basic structure of an exhaust gas treatment system with a housing part (1) in which is installed a catalytic converter (2), a measuring system with two antenna (5, 6) (of which one is optional), control (7) and evaluation electronics (8), and an optional temperature sensor (see DE102008012050A1) as well as an optional reflector (3, 4).

[0020] FIG. 2 shows resonance frequency curves which were measured in a synthesis gas plant for 13 dia. TWC drill cores. A drill core was measured. This was first tested fresh, and after a 12 hour fuel cut aging at 850 C. (aging 1) as well as after an aging at 1050 C. (aging 2). In all three aging stages, the catalytic converter was first preconditioned with a temperature ramp (20 K/min) up to 600 C. under reducing conditions (=0.95) and then cooled in a nitrogen atmosphere to 80 C. During the actual test, a constant synthetic, lean exhaust gas (=1.02) with 10% H.sub.2O was set. In the beginning, the temperature was maintained for 600 s at 80 C. and then increased at 20 K/min up to 600 C. The measured resonance frequency and the temperature of the catalytic converter in the three tests are plotted in FIG. 2. Upon switching from N.sub.2 to the water-containing atmosphere, a significant change is discernible in the resonance frequency, depending on the degree of aging and the sorption properties of the catalytic converter that were thereby changed. Also dependent is the change in the resonance frequency with the temperature up to about 200 C.

[0021] From the measured data in FIG. 2, the change in the resonance frequency, for example, was evaluated with the temperature between 80 and 100 C. and resonance frequency at 80 C. (Table 1).

TABLE-US-00001 TABLE 1 df/dT/MHz/K f.sub.res (between 80 and 100 C.) (T = 80 C.)/MHz fresh 1.43 5377.4 Aging 1 (850 C.) 1.19 5386.7 Aging 2 (1050 C.) 0.85 5406.2