外文翻譯（中文）--氮氧化物催化技術(shù)在汽車尾氣中的應用-全文預覽
【正文】 engines is further improved in the future, their exhaust characteristics will steadily e to resemble those of diesel engines. It is well known that the exhaust temperature and ambient HC/NOx ratio are the most important factors affecting the performance of lean NOx catalysts. Figure 3 shows the relationship between the ambient HC/NOx ratio and Nox conversion performance of the CuMFI catalyst, a typical lean NOx catalyst, in a leanburn gasoline engine bench test. This test was conducted to investigate the lightoff characteristics of the catalyst. The plots in the figure are for catalyst inlet exhaust temperatures of 350 and 400 C. Under an ambient HC/NOx ratio of less than 2, an extremely low level of NOx conversion was obtained. In view of the lower exhaust temperature expected for future engines that achieve high fuel bustion efficiency it will be necessary to develop highperformance lean NOx catalysts patible with the low HC level in the exhaust. 3. Selection of catalyst type Figure 4 shows a map of the NOx conversion level of lean NOx catalysts as a function of the maximum activity temperature. These data were piled from reports presented at the annual conferences of the Catalysis Society of Japan (CATSJ) and the Chemical Society of Japan (CSJ) in the past several years [3–34]. The experimental conditions of each catalyst in the map differ, making it difficult to pare their activities accurately. However, it is possible to classify the catalysts into three groups: the precious metal type (supported platinum catalyst in particular), the metal ion exchange zeolite type (copper ion exchange MFI zeolite in particular), and the base metal oxide type. The NOx reduction performance of a typical catalyst selected from each of the three categories and evaluated in diesel engine bench tests is shown in figure 5. Although the average HC/NOx ratio of the catalyst inlet gas in the activ ity test was at a low level of approximately , the supported platinum catalyst and the Cuzeolite catalyst showed paratively high conversion rates. The use of these two kinds of catalysts is included among the key technologies for developing highperformance lean NOx catalysts. The base metal oxide type shows the highest NOx conversion at high temperatures over 450 C, but it is assumed that this type of catalyst will not likely find practical application for automobile exhaust control due to the trend toward lower exhaust gas temperatures. The
畢業(yè)設計相關(guān)推薦
鄂ICP備17016276號-1