Threeway catalyst

The estimates prepared by the EC Commission that the annual cost to the Community for the emission issue alone could exceed ten billion ECUs is believed to be accurate. Ford would support the view that all of the implications of the use of threeway catalysts - and to some extent oxidation catalysts - have NOT been fully explored. 

The paper will discuss the options in pollution abatement technology available under the EC regulations and the major role catalysts are expected to play. Estimates will be presented on the future catalyst demand both in the EC and other West European countries. Cost breakdowns for threeway catalyst manufacture will be included. 

The current US emission limits for light duty vehicles are achieved for gasoline fueled cars by engines equipped with a controlled threeway catalyst system including an oxygen sensor and fuel injection. For the older engine types dual bed reduction/oxidation catalyst systems are often applied (Ref. 3). 

The precious metal content of a typical threeway catalyst in the USA currently is 20gr/cu ft (Ref. 6). To maintain a catalyst life similar to the US standard of a minimum 50,000 miles at the anticipated much higher remaining lead content (max. 13 mg/1) of European lead free gasolines, the precious metal content will have to be higher. 

The continuing price increases (see below) of Pt and particularly Rh, both indispensable components in a threeway catalyst, stimulated renewed R D efforts to substitute at least in part, both products by less costly metals. To date these efforts have not resulted in a catalyst with equal peformance. Catalyst life in particular was impaired. 

The sales price of threeway catalysts is for a major part determined by the precious metal costs, while for the less expensive oxidation catalyst, the impact is far less pronounced. This is illustrated in the following Figures 2 and 3. 

Cost build-up for a Typical European Threeway Catalyst 1.3 liter ceramic carrier with 1.24 gr/l Pt + Rh (ratio 5)... 

Because of the smaller size and the much lower price of Pd an oxidation catalyst is about 64% of the cost of a threeway catalyst. 

The increased prices of Pt and Rh increased the cost for a typical European threeway catalyst during the last half year by about 40% in US dollars. 

Platinum and palladium have high activities for total oxidation. This property is exploited in automotive exhaust catalysis. Automobile exhaust contains toxic gases such as CO, NO, and hydrocarbons which contribute to formation of photochemical smog and acid rain. Since 1978, catalysts based on platinum, rhodium, and sometimes palladium, supported on a monolithic carrier, are applied to convert exhaust gases to less harmful products. The so-called threeway catalyst enables the following three overall reactions... 

The emission limits by model year 1989/1990 are close to the US standards and therefore the same systems can be applied. Controlled threeway monolith type catalysts, predominantly single bed, are the preferred choice (Ref. 5, 6, 7). The catalyst formulations are modified to cope with European driving conditions (Ref.8,9). 

Heavy and high performance vehicles. Single bed controlled threeway monolity catalysts with fuel injection or a high performance carburator are the most likely choice. 

Light vehicIes.Uncontrolled single bed threeway monolith catalysts, internal or external exhaust gas recycle followed by an oxidation catalyst or even thermal oxidation, or a lean bum engine followed by an oxidation catalyst are being considered and/or applied. 

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