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101.
102.
介孔氧化铝负载钒催化剂上丙烷氧化脱氢制丙烯 总被引:6,自引:0,他引:6
采用浸渍法制备了介孔氧化铝 (m-Al2O3) 负载钒催化剂 (V/m-Al2O3), 并考察了其催化丙烷氧化脱氢制丙烯反应活性. 通过 N2 吸附-脱附、透射电镜、X 射线粉末衍射、紫外-可见漫反射光谱、氢-程序升温还原和氨-程序升温脱附对催化剂进行了表征. 结果表明, 介孔氧化铝具有大比表面积、窄孔径分布和两维六方相结构, 在其上负载适量的 V 可实现 V 活性物种的高分散及催化剂的弱酸性, 从而有利于提高丙烷转化率和丙烯选择性. 与共合成法制备的含 V 介孔氧化铝 V/m-Al2O3(C) 和浸渍法制备的 V/?-Al2O3 相比, V/m-Al2O3 表现出更高的催化活性. 这与载体较弱的酸性和较大的比表面积以及 V 物种的高分散有关. 相似文献
103.
在覆盖有钨电极的硅衬底上利用多孔阳极氧化铝模板为生长掩膜电沉积合成垂直排列的铜铟硒纳米棒阵列. 多孔阳极氧化铝模板由阳极氧化磁控溅射制备的铝膜制成. 扫描电子显微镜结果表明,该纳米棒阵列结构致密,直径约100 nm长度约1μm,纵横比为10. X射线衍射、微区拉曼光谱和高分辨透射电子显微镜结果表明,真空条件下450 oC退火处理的铜铟硒纳米棒是多晶纯相的黄铜矿结构的铜铟硒,在纳米棒轴向方向上有比较大的晶粒尺寸. 能量色散X射线光谱表明,铜铟硒纳米棒的化学组成接近InSe2的化学计量比,由吸收光谱分析推算铜铟硒纳米棒带隙为0.96 eV. 相似文献
104.
Porous anodic alumina is an important nanoscale template for fabrication of various nanostructures. We report a new ultrasound-assisted anodization process in oxalic acid. Under the continuous irradiation of ultrasound, the one-step-anodized sample has a smooth and clean surface, and two-step-anodization brings ordered porous anodic alumina with higher growth rate of 52 μm/h. The ultrasound applied during the anodization can clean the surface and enhance the nanopore growth since it can accelerate the oxide dissolving on the electrolyte/oxide interface. The ultrasound-assisted anodization may be utilized for other anodizations. 相似文献
105.
Vasant R Choudhary Chinta Sivadinarayana Kshudiram Mantri 《Journal of Chemical Sciences》1999,111(5):669-676
The acidity and initial and time-on-stream activity in propane aromatization (at 550°C, space velocity of 3100 cm3g−1
(zeolite)h−1) of Ga-impregnated H-ZSM-5 zeolite without or with binders (50 wt%), such as silica, alumina and kaolin, have been investigated.
Both the acidity and catalytic activity of the zeolite are influenced by the presence of binder in the catalyst, depending
upon the binder. The influence is found to be lowest for alumina and highest for kaolin. Among the binders, alumina is the
most preferred binder for the zeolite catalyst. 相似文献
106.
The retention of polar compounds, the separation of structural isomers and thermal stability make carbonaceous materials very attractive stationary phases for liquid chromatography (LC). Carbon clad zirconia (C/ZrO2), one of the most interesting, exhibits unparalleled chemical and thermal stability, but its characteristically low surface area (20–30 m2/g) limits broader application as a second dimension separation in two-dimensional liquid chromatography (2DLC) where high retentivity and therefore high stationary phase surface area are required. In this work, we used a high surface area commercial HPLC alumina (153 m2/g) as a support material to develop a carbon phase by chemical vapor deposition (CVD) at elevated temperature using hexane vapor as the carbon source. The loading of carbon was varied by changing the CVD time and temperature, and the carbon coated alumina (C/Al2O3) was characterized both physically and chromatographically. The resulting carbon phases behaved as a reversed phase similar to C/ZrO2. At all carbon loadings, C/Al2O3 closely matched the unique chromatographic selectivity of carbon phases, and as expected the retentivity was increased over C/ZrO2. Excess carbon – the amount equivalent to 5 monolayers – was required to fully cover the oxide support in C/Al2O3, but this was less excess than needed with C/ZrO2. Plate counts were 60,000–76,000/m for 5 μm particles. Spectroscopic studies (XPS and FT-IR) were also conducted; they showed that the two materials were chemically very similar. 相似文献
107.
108.
Increasing in the use of various chromium species over the past few decades has inevitably resulted in an increased flux of
their metallic substances in aquatic life. Therefore, experimental work was developed to improve the physical and chemical
characteristics of the prepared mesoporous SiO2–Al2O3 mixed oxides via a sol–gel process. The effective key parameter on the properties of the materials was achieved by the addition
of carboxylate functional group such as Alph-hydroxyl isobuteric acid (AHIBA) during the gelation process and prior the calcinations
step. Better performance of these carboxylate resins are attributed to the complexing ability of the carboxylate groups toward
polyvalent chromium species which is added to the normal sorption properties of the oxides. Urea has been used as a means
of producing an aluminum precipitate that is easier to filter than that produced by rapid addition of base. Introduction of
Al and Si salts together to form mixed oxide modified the way of their substitution in the hosting resin than when they were
separately added. The data revealed that mesoporous materials with very narrow pore diameter distribution (micron-sized) and
high surface area were obtained. The surface areas and pore size distributions were mainly depend on SiO2 content. Systematic investigations were carried out on the set of the prepared mixed oxides with different porosity, cross-linking
degree and exchange loading to find out the best sorbent for chromium removal. The final objective in all cases was aimed
at determining feasible and economically reliable solution to the environmental problems related to the tannery industry. 相似文献
109.
Comparison of Drying Procedures for the Preparation of Alumina Powders with the System Al-Alkoxide/Tertiary Butanol/Water 总被引:1,自引:0,他引:1
E. Ponthieu E. Payen G.M. Pajonk J. Grimblot 《Journal of Sol-Gel Science and Technology》1997,8(1-3):201-206
Two series of alumina gel precursors, obtained from Al sec-butylate, ASB, or Al tert-butylate, ATB, dissolved in tertiary
butanol, TB, have been dried according to five procedures, in order to compare their efficiency and the consequences they
may have on the structure of the final product. They consist of lyophilization (or freezedrying), evacuation at room temperature
(with or without ageing of the gel), drying in an oven at atmospheric pressure, or under hypercritical conditions. Chemical
analysis, X-Ray diffraction and spectroscopic characterizations (FTIR and laser Raman) allow the identification of the phases
present. The temperature of the drying step, as well as the nature of the alkoxide percursor, considerably affect the final
dried products. 相似文献
110.
《Reaction Kinetics and Catalysis Letters》1997,62(2):281-286
Oligomerization of glycine (gly) and diglycine (gly2) on silica and alumina was observed in experiments simulating wetting-drying cycles at 80°C. Glycine produces less than 1%
total yield of gly2 and diketopiperazine (DKP) after one week. In experiments starting from gly2, more than 10% DKP is formed. Formation of higher oligomers (gly3–gly6) proceeded as well, with 3.8% and 5.1% total yields on silica and alumina surfaces respectively. 相似文献