| Summary: | 博士 === 臺灣大學 === 環境工程學研究所 === 98 === Motorcycle engine exhaust is one of the major sources of air pollutants in Taiwan. Their pollutant emissions were evaluated to contribute about 3%, 11% and 13% to NOx, HC and CO emissions respectively. Catalytic converters have been enforced to be assembled in exhaust pipes of motorcycles produced later than 1998, to reduce pollutant emissions. Nevertheless, catalytic converters were reported as becoming deactivated, which was attributed to operation conditions of high temperature and impurities. Consequently, motorcycles equipped with those deactivated catalytic converters cause severe impact on the environment. In this study, catalytic converters used for different ages and mileages were characterized by forms of analytical techniques to investigate the deactivation phenomena. The laboratory aging tests were performed to simulate the real operation conditions of motorcycle catalytic converters and determine the effects of operation temperature, operation time, poison’s type and poison’s concentration on catalytic properties.
According to the analytical results of catalysts used for different ages and mileages, thermal deactivation and poisoning were described as the main deactivation mechanisms. The aging induced phase transitions, loss in specific surface areas and pore volume, the growth in the pore size and the deterioration of catalytic performances were observed. The accumulation of the used time stands for the increase in the deactivation potential.
Thermal deactivation tests were performed to determine the effects of operation temperature and operation time on catalytic properties. The thermal deactivation phenomena became more significant with the increase in the operation temperature. The loss in specific surface area exhibited an increasing trend as:
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