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1.
Rh基催化剂上氢甲酰化反应过程的原位高压NMR研究   总被引:1,自引:1,他引:0       下载免费PDF全文
制备了用于丙烯氢甲酰化反应的Rh/SBA-15 和PPh3修饰的PPh3-Rh/SBA-15催化剂. 应用原位变温高压核磁共振技术,对比研究了丙烯在Rh/SBA-15 和PPh3修饰的多相催化剂PPh3 Rh/SBA-15上的氢甲酰化反应,实现了高压条件下催化反应的原位固体核磁共振表征. 13C MAS NMR研究结果表明:在1.0 MPa的反应压力下,随着反应温度升高丙烯与合成气在Rh/SBA-15催化剂上可转化生成丁醛,而PPh3配体修饰的PPh3-Rh/SBA-15催化剂上丁醛产物的正异比显著提高.  相似文献
2.
采用时间分辨红外光谱直接观测了甲醇在Pt/TiO2上光催化反应制氢过程中光生电子还原氢离子生成氢气的反应过程.结果表明Pt的担载量存在一最佳值,使得该催化剂中光生电子的反应速度最快.当Pt担载量相同时,Pt/TiO2催化剂中光生电子参与产氢反应的速度随样品还原温度的不同而明显变化.可能的原因是较高温度下氢气还原的Pt/TiO2催化剂中Pt粒子占据了TiO2表面的一些能够解离吸附甲醇的活性位置,而对于较低温度下氢气还原的Pt/TiO2催化剂,这种占据作用很不明显.实验中还发现瞬态动力学研究中光生电子衰减较快  相似文献
3.
Germanium and iron co-doped SrCoO2.5+δ was investigated in terms of phase stability, oxygen permeability and electrical conductivity. The favorable high-temperature cubic structure of SrCoO2.5+δ was stabilized to lower temperatures by co-doping Ge (10 mol%) and Fe (10 mol%) that substituted for Co, which however could not be achieved by doping Ge (20 mol%) alone. In contrast to SrCo0.8Ge0.2O2.5+δ sample which showed a sharp decrease in oxygen permeability at temperature of 875 °C upon cooling, SrGe0.1Co0.8Fe0.1O3−δ sample remained well-permeable to oxygen at lower temperatures down to at least 820 °C; an abrupt change in electrical conductivity in SrCo0.8Ge0.2O2.5+δ also occurred accompanying the phase transition. The oxygen permeation flux for SrGe0.1Co0.8Fe0.1O3−δ increased significantly with the decrease of the membrane thickness, indicating the transport of oxygen ions in the bulk of the membrane as the rate-limiting step.  相似文献
4.
The surface chemistry of NO and NO2 on clean and oxygen-precovered Pt(1 1 0)-(1 × 2) surfaces were investigated by means of high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). At room temperature, NO molecularly adsorbs on Pt(1 1 0), forming linear NO(a) and bridged NO(a). Coverage-dependent repulsive interactions within NO(a) drive the reversible transformation between linear and bridged NO(a). Some NO(a) decomposes upon heating, producing both N2 and N2O. For NO adsorption on the oxygen-precovered surface, repulsive interactions exist between precovered oxygen adatoms and NO(a), resulting in more NO(a) desorbing from the surface in the form of linear NO(a). Bridged NO(a) experiences stronger repulsive interactions with precovered oxygen than linear NO(a). The desorption activation energy of bridged NO(a) from oxygen-precovered Pt(1 1 0) is lower than that from clean Pt(1 1 0), but the desorption activation energy of linear NO(a) is not affected by the precovered oxygen. NO2 decomposes on Pt(1 1 0)-(1 × 2) surface at room temperature. The resulted NO(a) (both linear NO(a) and bridged NO(a)) and O(a) repulsively interact each other. Comparing with NO/Pt(1 1 0), more NO(a) desorbs from NO2/Pt(1 1 0) as linear NO(a), and both linear NO(a) and bridged NO(a) exhibit lower desorption activation energies. The reaction pathways of NO(a) on Pt(1 1 0), desorption or decomposition, are affected by their repulsive interactions with coexisting oxygen adatoms.  相似文献
5.
X-ray photoelectron spectroscopy was applied to study the hydroxylation of α-Al2O3 (0 0 0 1) surfaces and the stability of surface OH groups. The evolution of interfacial chemistry of the α-Al2O3 (0 0 0 1) surfaces and metal/α-Al2O3 (0 0 0 1) interfaces are well illustrated via modifications of the surface O1s spectra. Clean hydroxylated surfaces are obtained through water- and oxygen plasma treatment at room temperature. The surface OH groups of the hydroxylated surface are very sensitive to electron beam illumination, Ar+ sputtering, UHV heating, and adsorption of reactive metals. The transformation of a hydroxylated surface to an Al-terminated surface occurs by high temperature annealing or Al deposition.  相似文献
6.
Two Pt/C catalysts with different particle sizes (Pt/C: 2.5 nm, Pt/C-700Ar: 5.1 nm) were investigated by applying a half-cell configuration —rotating disk electrode (RDE) technique in H2SO4 aqueous solutions in the absence of or in the presence of methanol with different concentrations. Pt/C catalyst exhibited higher mass activity in H2SO4 aqueous solution without methanol and slightly lower mass activity in H2SO4 plus 0.1 mol/L CH3OH in comparison with that of Pt/C-700Ar catalyst. On the contrary,single direct methanol fuel cell (DMFC) tests showed that Pt/C exhibited higheroxygen reduction reaction (ORR) activity and better cell performance, mainly due to the different kinds of electrolyte properties. Furthermore, it suggested that a better single DMFC performance could be obtained with a smaller particle size Pt-based cathode catalyst. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 — 18, 2004.  相似文献
7.
利用自行研制的高压釜和原位高压核磁共振研究了甲烷水合物在具有孔径均一的中孔SBA-15中的形成过程. 结果发现在静止的状态下,甲烷在中孔SBA-15内与水也能生成甲烷水合物,但其形成所需要的诱导时间比在纯水的条件下要短,SBA-15可促进甲烷水合物的形成;原位高压1H和13C NMR研究表明即使甲烷过量,在一定压力下,SBA-15孔道内的水也不能完全形成甲烷水合物.  相似文献
8.
FeO x -hydroxyapatite (FeO x -HAP) composites with different FeO x contents were prepared, and compared with pure FeOx, the FeO x -HAP composites exhibit strongly magnetic behavior in an external magnetic field even after 600 °C calcination. The combination of 57Fe Mössbauer and Fe K-edge XAFS indicates that HAP can stabilize the size and crystal phase of γ-Fe2O3 during heat treatment. Even after 600 °C calcination, the interaction imposed by HAP could produce large amounts of distorted octahedral coordination Fe sites in the interior lattice and then result in strong magnetism. The thermally stable γ-Fe2O3-HAP composites may provide a new opportunity for developing efficient supported crystal-dependent catalysts.  相似文献
9.
The TiO2 nanorod arrays, with about 1.8 μm lengths, have been deposited on ITO substrates by dc reactive magnetron sputtering at different target-substrate distances. The average diameter of these nanorods can be modified from about 45 to 85 nm by adjusting the target-substrate distance from 90 to 50 mm. These nanorods are highly ordered and perpendicular to the substrate. Both XRD and Raman measurements show that the nanorods prepared at different target-substrate distances have only an anatase TiO2 phase. The nanorods prepared at the target-substrate distance less than 80 mm have a preferred orientation along the (2 2 0) direction. However, this preferred orientation disappears as the target-substrate distance is more than 80 mm. These TiO2 nanorods have been used as the electrodes for dye-sensitized solar cells (DSSCs). The highest conversion efficiency, about 4.78%, has been achieved for TiO2 nanorods prepared at 80 mm target-substrate distance.  相似文献
10.
应用原位变温高压MAS核磁共振技术,对比研究了CO在不同Rh基催化剂上的吸附和加氢反应过程. 29Si MAS NMR研究结果表明:Rh基催化剂中加入金属助剂后,载体Silicate-1上的表面硅羟基减少,助剂金属与硅羟基作用锚锭在载体表面. 13C MAS NMR研究结果表明:当引入CO/H2混合气后,在Rh/Silicate-1催化剂上只能观测到气相CO、线式吸附CO和孪式吸附CO的快速交换信号;而在Rh-Mn/Silicate-1和Rh-Mn-Li/Silicate-1催化剂上,还观测到了倾斜式吸附的CO共振信号,表明助剂Mn或Mn-Li的加入促进了CO的吸附.随着反应温度升高,CO/H2在Rh/Silicate-1催化剂上转化生成CO2,进一步升高温度会有CH4生成;而CO/H2在RhMnLi/Silicate-1催化剂上反应活性更高,在较低的温度下就会转化生成CO2,但未观测到甲烷的生成. 1H MAS NMR谱显示,反应后载体Silicate-1上硅羟基的量会减少,表明CO与载体部分表面硅羟基反应生成了CO2.  相似文献
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