Performance of the automotive three-way catalytic converter

Abstract EN

A three-way catalyst is a multifunctional supported catalyst which is capable of converting the major automotive pollutants: CO, HC’s, and NO^., simultaneously.

Three-way catalyst systems have been developed as a result of the strict automotive emission regulations (especially for NO^) which came into force in the USA in 1981.

Gas concentration and temperature play an important role in the efficiency of three-way catalysts for the removal of CO and HC’s from automotive exhaust gas.

One of the methods used for evaluating the performance of the three way catalyst is to change the feed gas temperature and measure the corresponding conversions at various oxygen concentrations.

Recent studies have reported the effect of oxygen concentration and temperature on the conversion of propane and n-hexane in a model gas test over the three way catalyst.

In this paper, the performance of the three way catalyst under realistic engine conditions was studied.

A prototype 4-stroke one cylinder stationary internal combustion engine was utilized as a source of exhaust gas.

The effect of oxygen concentration and temperature were traced.

The three-way catalyst efficiency appeared to be strongly dependent on the oxygen partial pressure.

The three-way catalyst performance is generally enhanced with increase in oxygen concentration.

The three-way catalyst was found to be more active for conversion of CO than for HC’s.

Under reducing conditions, the conversion curves for CO and HC’s were observed to go through a maximum and then decline sharply with temperature.

These declines started at a temperature of about 286°C.

This inhibition might be ascribed to chemisorption of CO, NO, and HC’s on the catalyst active sites and to the consumption of oxygen in undesired reactions such as hydrogen oxidation.