The adsorption of NO on alumina supported Pd catalysts and the effect of adding Li 2O on NO adsorption have been investigated by using TPD MS method. Experimental results certify the existence of three types of surfac...The adsorption of NO on alumina supported Pd catalysts and the effect of adding Li 2O on NO adsorption have been investigated by using TPD MS method. Experimental results certify the existence of three types of surface species. The adsorptive dissociation of NO gives a relatively inactive intermediate N 2O. Its desorption amount is larger on Al 2O 3 and Pd/Al 2O 3 Li 2O than that on Pd/Al 2O 3. The adsorption intensity of N 2O is the strongest on Pd/Al 2O 3 Li 2O. The experiments of competitive adsorption of O 2 and NO reveal that the presence of O 2 has two effects: (1) the O atom sticks to the Pd site on the surface and inhibits the adsorption of NO, as well as the decomposition of NO; (2) O 2 can react with NO to form nitrite or nitrate species which can adsorb strongly on the surface. The relative efficiency of the two effects differs with temperature, and this can be applied to explain some phenomena in the adsorption of NO, and the selective catalytic reduction of NO as well.展开更多
A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characte...A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characterized by XRD, TPR and DR-UVS. The natures of oxygen species on the surfaces of these samples were studied by using temperature programmed desorption-mass spectrography(TPD-MS). The results showed that the oxygen species of multiple adsorption existed on the sample surface. And in the range of desorption temperature<900℃, for the Ce-Mo samples, not only the desorption peaks of O- species on surfaces of samples be discoved, but also the O2- species appeared. As the content of Ce in Ce-Mo oxides was changed, the activation energy of oxygen desorption(Ed) also changed. The Ed value of sample 3 (Ce/Mo=1/1) is the lowest and its selectivity of benzaldehyde in toluene oxidation is the highest. Thus, a Parallel relation between the Ed value and the selectivity for benzaldehyde existed in these Ce-Mo oxides.展开更多
橡胶树死皮(Tapping panel dryness,TPD)是限制天然橡胶产量提高的关键因子之一,鉴定健康和死皮橡胶树胶乳差异表达蛋白对阐明橡胶树死皮发生机制具有重要意义。研究首次采用同位素标记相对和绝对定量(Isobaric tags for relative and a...橡胶树死皮(Tapping panel dryness,TPD)是限制天然橡胶产量提高的关键因子之一,鉴定健康和死皮橡胶树胶乳差异表达蛋白对阐明橡胶树死皮发生机制具有重要意义。研究首次采用同位素标记相对和绝对定量(Isobaric tags for relative and absolute quantitation,iTRAQ)结合二维液相色谱串联质谱(Two-dimensional liquid chromatography-tandem mass spectrometry,2D LC-MS/MS)技术对健康和死皮橡胶树胶乳蛋白质组的差异进行研究。结果显示,有16个蛋白差异表达,其中,在死皮树中表达上调的蛋白有2个,下调的蛋白有14个。进一步应用实时荧光定量RT-PCR对其中6个差异蛋白的基因进行表达分析,发现其表达趋势与蛋白质组水平的研究结果一致。功能分析显示,这些差异蛋白主要与细胞程序性死亡(如TCTP、HSP70、CaM、cysteine protease等)和橡胶生物合成(如SRPP和diphosphomevelonate decarboxylase)相关,从蛋白质组学角度进一步验证了橡胶树死皮发生过程中涉及细胞程序性死亡和橡胶生物合成途径。展开更多
La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ perovskite-type catalyst for methane combustion prepared through sol-gel process was characterized by X-ray Diffractometry（XRD）, X-ray Photoelectron Spectros...La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ perovskite-type catalyst for methane combustion prepared through sol-gel process was characterized by X-ray Diffractometry（XRD）, X-ray Photoelectron Spectroscopy（XPS） and Scanning Electron Microscopy（SEM）. XPS analyses reveal that the surface characteristics of the catalyst are changed. The lattice defects and oxygen vacancies on the catalyst surface are enhanced due to a part of La3+ being substituted by Cu2+ . Temperature-programmed-desorption（TPD） and temperature-programmed-reduction（TPR） analyses were carried out to study the catalytic behavior. It is found that there are two O2-desorption peaks at 350℃ and 650℃ in the TPD pattern, and two CH4-consumption peaks at 420℃ and 750℃ in the TPR patterns respectively, which indicates that the two kinds of oxygen species, so-called α and β oxygen, can react with the methane during catalytic combustion process. The catalytic activity tests were performed in a fixed-bed reactor, and the results show that the T<sup>1/2 at which the conversion of methane attains 50% of La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ is lower by 55℃ than that of LaMnO3. This indicates that the catalytic activity of-La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ is increased with partial substitution of Cu2+ for La3+ .-展开更多
文摘The adsorption of NO on alumina supported Pd catalysts and the effect of adding Li 2O on NO adsorption have been investigated by using TPD MS method. Experimental results certify the existence of three types of surface species. The adsorptive dissociation of NO gives a relatively inactive intermediate N 2O. Its desorption amount is larger on Al 2O 3 and Pd/Al 2O 3 Li 2O than that on Pd/Al 2O 3. The adsorption intensity of N 2O is the strongest on Pd/Al 2O 3 Li 2O. The experiments of competitive adsorption of O 2 and NO reveal that the presence of O 2 has two effects: (1) the O atom sticks to the Pd site on the surface and inhibits the adsorption of NO, as well as the decomposition of NO; (2) O 2 can react with NO to form nitrite or nitrate species which can adsorb strongly on the surface. The relative efficiency of the two effects differs with temperature, and this can be applied to explain some phenomena in the adsorption of NO, and the selective catalytic reduction of NO as well.
文摘A series of Ce-Mo oxide catalysts with different Ce/Mo atomic ratio were prepared and applied to selective oxidation of toluene to benzaldehyde. The structures and properties of the surfaces of catalysts were characterized by XRD, TPR and DR-UVS. The natures of oxygen species on the surfaces of these samples were studied by using temperature programmed desorption-mass spectrography(TPD-MS). The results showed that the oxygen species of multiple adsorption existed on the sample surface. And in the range of desorption temperature<900℃, for the Ce-Mo samples, not only the desorption peaks of O- species on surfaces of samples be discoved, but also the O2- species appeared. As the content of Ce in Ce-Mo oxides was changed, the activation energy of oxygen desorption(Ed) also changed. The Ed value of sample 3 (Ce/Mo=1/1) is the lowest and its selectivity of benzaldehyde in toluene oxidation is the highest. Thus, a Parallel relation between the Ed value and the selectivity for benzaldehyde existed in these Ce-Mo oxides.
文摘La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ perovskite-type catalyst for methane combustion prepared through sol-gel process was characterized by X-ray Diffractometry（XRD）, X-ray Photoelectron Spectroscopy（XPS） and Scanning Electron Microscopy（SEM）. XPS analyses reveal that the surface characteristics of the catalyst are changed. The lattice defects and oxygen vacancies on the catalyst surface are enhanced due to a part of La3+ being substituted by Cu2+ . Temperature-programmed-desorption（TPD） and temperature-programmed-reduction（TPR） analyses were carried out to study the catalytic behavior. It is found that there are two O2-desorption peaks at 350℃ and 650℃ in the TPD pattern, and two CH4-consumption peaks at 420℃ and 750℃ in the TPR patterns respectively, which indicates that the two kinds of oxygen species, so-called α and β oxygen, can react with the methane during catalytic combustion process. The catalytic activity tests were performed in a fixed-bed reactor, and the results show that the T<sup>1/2 at which the conversion of methane attains 50% of La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ is lower by 55℃ than that of LaMnO3. This indicates that the catalytic activity of-La<sup>0.8 Cu<sup>0.2 MnO<sup>3±δ is increased with partial substitution of Cu2+ for La3+ .-
