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yingxingwang銀蟲 (小有名氣)
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[求助]
這斷英文須要高手幫忙啊
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Fig. 7 presents the H2-TPR profiles of the M-OMS-2 catalysts. Reduction of all the catalysts occurs in a temperature range of 170–350 °C. The peak position, area, and peak types vary among the catalysts (Table 1), indicating different influence of the doping metal on the OMS-2. These peaks between 200 °C and 350 °C can be ascribed to the hydrogen consumption during the formation of Mn2O3, the reduction of Mn2O3 to Mn3O4, and Mn3O4 to MnO [42]. From Fig. 7, one can readily observe that Cu-OMS-2 catalyst shows the highest reducibility with the largest H2 consumption (12.14 mol/g) and the lowest starting temperature of 170 °C, which might be caused by the reduction of Cu species [24]. Furthermore, the Fe-OMS-2 and Cr-OMS-2 catalysts show lower reducibility with the smallest H2 consumption (10.80 and 10.73 mol/g, respectively), and higher starting reduction temperature (272 °C and 275 °C, respectively). The reducibility of the M-OMS-2 catalysts decreases in the following ord er: Cu-OMS-2 > Ni-OMS-2 >Co-OMS-2 > Cr-OMS-2 > Fe-OMS-2. The higher reducibility indicates the higher mobility of the oxygen species in catalysts. Therefore, Cu can significantly improve the oxygen mobility in OMS-2 catalyst compared with the other doping metals. The TPR results correlate fairly well with the catalytic combustion activities and the XPS results. Similar results have been reported for the silver modified OMS-2 catalysts in the CO oxidation reaction[43]. Moreover, Hernández et al. [44] also suggested that Cu could improve the reducibility of OMS-2 and enhance the catalytic activity in preferential oxidation of CO. The promotion effect of Cu on the reducibility of OMS-2 could be attributed to the formation of Cu–O–Mn bridge and the hydrogen spillover from Cu atoms to manganese oxides [24,45]. Combined with the XPS and H2-TPR results, it can be concluded that the highest catalytic activity of Cu-OMS-2 catalyst can be ascribed to the richer defect-oxide species and the higher reducibility or oxygen mobility.Benzyl alcohol oxidation over OMS-2 catalyst has been proposed to obey the Mars–van-Krevelen (MVK) mechanism [31]. |
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yingxingwang: 金幣+60, 翻譯EPI+1, ★有幫助, 我用了下，谷歌翻譯，確實也差不多，所以就不給你滿分了 2013-04-07 22:19:54
yingxingwang: 金幣+60, 翻譯EPI+1, ★有幫助, 我用了下，谷歌翻譯，確實也差不多，所以就不給你滿分了 2013-04-07 22:19:54
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圖7顯示了金屬-OMS-2催化劑的H2-TPR譜圖。 所有催化劑的還原中發(fā)生的溫度范圍為170〜350℃。峰的位置，面積和峰的類型因催化劑的不同而不同（表1），表明對OMS-2引入不同的金屬產(chǎn)生的不同影響。在200℃到350℃下的這些峰可以歸為在Mn2O3的形成，Mn2O3還原成Mn3O4，Mn3O4還原成MnO[42]的過程中H的消耗。從圖7，我們可以很容易地觀察到的Cu-OMS-2催化劑表現(xiàn)出最高的還原性，最大的耗氫量（12.14摩爾/克）和最低的起始溫度為170℃，這可能是由于Cu這種物質(zhì)的還原性引起的。此外，鐵-OMS-2和鉻-OMS-2催化劑表現(xiàn)出較低的還原性具有最小的耗氫量（分別為10.80和10.73 mol / g以下），和更高的起始還原溫度（分別為272℃和275℃） 。金屬-OMS-2催化劑還原性由高到低的排列順序如下：銅-OMS-2>鎳-OMS-2>鈷-OMS-2>鉻-OMS-2的Fe-OMS-2 。更高的還原性表示氧在催化劑的流動性較高。因此，與其他引入的金屬相比，銅可以顯著提高氧在OMS-2催化劑中的流動性。 TPR結(jié)果與催化燃燒活性和XPS結(jié)果聯(lián)系相當(dāng)密切。類似的結(jié)果已經(jīng)報道過關(guān)于銀修飾的OMS-2催化劑在CO氧化反應(yīng)中的活性[43]。此外，Hernandez等人也提出銅可以改善OMS-2的還原性和提高的CO優(yōu)先氧化的催化活性，Cu對OMS-2的還原性的促進(jìn)效應(yīng)可以歸因于Cu-O-Mn橋的形成和銅原子到氧化錳過程中H的溢出[24,45]。結(jié)合XPS和H2-TPR結(jié)果，可以得出結(jié)論，Cu-OMS-2催化劑最高的催化活性可以歸因為更豐富缺氧物質(zhì)和更高的還原性或氧流動性.用OMS-2催化劑的苯甲醇的氧化已經(jīng)提出了要遵循Mars–van-Krevelen (MVK）機(jī)制[31]。 |
7樓2013-04-07 16:28:56
hookhans
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yingxingwang
銀蟲 (小有名氣)
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