外文翻譯中文--氮氧化物催化技術(shù)在汽車尾氣中的應(yīng)用-資料下載頁
2025-05-12 05:04本頁面
【導(dǎo)讀】日本尼桑汽車有限公司材料研究中心橫須賀237-8523。用，以進一步提高燃油經(jīng)濟性。那時廢氣溫度會降低，同時廢氣中會有少量烴（碳。在直噴式柴油發(fā)動機已成為主流情況下，圖1顯示了歐洲和日本現(xiàn)有和建議的汽油和柴油轎車的氮氧化物排放標(biāo)準(zhǔn)。薄燃燒發(fā)動機的高轉(zhuǎn)換效率的催化劑。由于標(biāo)準(zhǔn)十分嚴格，催化劑的研究有很多的障礙。現(xiàn)在有些氮氧化物分解技。術(shù)和氮氧化物催化技術(shù)已應(yīng)用于一些稀薄燃燒發(fā)動機。實現(xiàn)這一目標(biāo)，它全靠較高的空燃比條件。方面，柴油發(fā)動機排氣含有較多的重碳氫化物，隨著二氧化硫引起的催化劑失效，表1為柴油機排氣的特點總結(jié)，目前柴油發(fā)動機和汽油之間差異相當(dāng)明顯。圖3顯示了在不完全燃燒汽油發(fā)動機臺架測試氮氧化物和碳氫?；镏葘Υ呋瘎┑挠绊?。碳氫含量較低的情況下制定高效的碳氫氮氧化物催化劑。碳氫和硝之比等于1，頻率為35000次每小時。氫化物對氮氧化物的還原作用。要進一步改進催化劑系統(tǒng)描述的那些還要提高催化劑的活性和耐久性。
【正文】 aracteristics of these three types of catalysts are summarized in table 2. The precious metal catalyst, es pecially the platinum catalyst, shows better NOx conversion performance in low temperature regions. However, as shown in figure 6, it is well known that the platinum catalyst produces N2O, which is a typical greenhouse gas. Some means of suppressing N2O formation is necessary when the platinum catalyst is used. 4. Development strategy for lean NOx catalysts Table 3 shows our strategy for catalyst development. Effective ways of coping with the trend toward a lower exhaust temperature are to utilize the high reactivity of NO2 and to improve the reactivity of HCs. Improving the rate of HC utilization and increasing the HC/NOx ratio on the catalyst surface are effective measures for dealing with the lower HC content in the exhaust gas. Iwamoto et al. proposed the intermediate addition of reductant (IAR) method [35] as a way of using the high reactivity of NO2 and improving the HC utilization rate. This method is effective in utilizing the precious metal to improve catalyst activity at lower temperatures. Effective use of the HC adsorption/reforming function is a key factor in improving the selectivity of catalysts for the NOx–HC reaction. We have previously reported that the use of zeolite as an HC adsorbent is effective in increasing the HC/NOx ratio on the catalyst surface [36,37]. Other researchers [38,39] have suggested approaches involving the direct or indirect supply of a suitable reductant to the exhaust stream so as to increase the ambient HC/NOx ratio, but these methods sacrifice fuel economy. 5. Summary Further improvement of fuel efficiency will result in a smaller quantity of HCs in the exhaust of future engines. Therefore, catalyst activity at lower temperatures will have to be improved to make more effective use of HCs as Nox reductants. Utilization of precious metals is effective in improving catalytic activity in the lower temperature region, but it is necessary to suppress N2O formation when a precious metal (platinum) catalyst is used. In this work, lean NOx catalyst performance was improved markedly by using a hydrocarbonreforming catalyst, which increased the rate of HC utilization as Nox reductants. In order to put lean NOx catalysts with high conversion efficiency to practical use, it is necessary to improve the activity and durability of each catalyst, in addition to the further improvement of the catalyst systems described here.
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