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排序方式: 共有824条查询结果,搜索用时 31 毫秒
1.
Marcella Bonchio Mauro Carraro Martino Gardan Gianfranco Scorrano Enrico Drioli Enrica Fontananova 《Topics in Catalysis》2006,40(1-4):133-140
The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic
substrates under oxygen atmosphere at 25 °C. Photocatalytic membranes have been prepared yielding polymeric films with a high
thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and
reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening
has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been
evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity
behavior has been evidenced by comparison with homogeneous oxidations. 相似文献
2.
M. Abdallah 《Corrosion Science》2003,45(12):2705-2716
The effect of some ethoxylated fatty alcohols, with different numbers of ethylene oxide units, on the corrosion of zinc in 0.5 M HCl has been studied using weight loss and polarization measurements. The inhibition efficiency was found to increase with increasing concentration, number of ethylene oxide units per molecule and with decreasing the temperature. Inhibition was explained on the basis of adsorption of ethoxylated fatty alcohols molecules on the metal surface through their ethoxy groups. The degree of surface coverage varied linearly with logarithm of inhibitor concentration fitting Temkin isotherm. The thermodynamic parameters were calculated for the tested system from the data obtained at different temperatures. 相似文献
3.
A generalized equation for surface tension from the triple point to the critical point 总被引:1,自引:0,他引:1
G. R. Somayajulu 《International Journal of Thermophysics》1988,9(4):559-566
A three-parameter generalized equation is proposed for surface tension from the triple point to the critical point. This equation not only fits the data well but also is good for interpolation between the normal boiling point and the critical point. This equation is also good for extrapolation to the triple point. This equation has been tested using the surface tension of water from the triple point to the critical point. The constants of this equation obtained using orthobaric surface tensions are given for a number of compounds. The isobaric surface tensions determined at a pressure of 1 atm do not differ significantly from the orthobaric surface tensions. Such data also have been used in obtaining equations from the triple to the critical point.Nomenclature
T
c
Critical temperature, K
-
T
t
Triple point, K
-
T
m
Melting point, K
-
T
r
Reduced temperature, K
-
X
(T
c-T)/T
c
-
Surface tension, dyne · cm–1;10–3N · m–1
-
m
Surface tension at the melting point
-
f
Surface tension at T
r=0.9
-
t
Surface tension at the triple point
- Relative deviation
100[
obsd–
calcd]/
obsd
- Standard deviation
[(
obsd–
calcd)2/(No. points—No. parameters)]0.5 相似文献
4.
Till Wettlaufer Birgit Hetzer Eckhard Flöter 《European Journal of Lipid Science and Technology》2021,123(7):2000345
In this paper, the structuring of liquid oils, also known as oleogelation, is systematically investigated for the first time using a quasi-quaternary mixing system approach. Native waxes with different quantities of wax esters (WE), n-alkanes (hydrocarbons (HC)), fatty acids (FA), and fatty alcohols (FaOH) are applied in mixtures with hydrolyzed waxes to systematically change the composition. Hydrolyzed waxes contain high levels of FA and FaOH. The model systems are investigated on microscopic level (brightfield light microscopy (BFM), cryogenic scanning electron microscopy (cryo-SEM)) as well as on their macroscopic properties (rheology, gel hardness) and calorimetric behavior (differential scanning calorimetry (DSC)). It is found that sunflower wax (SFW)-based gels (12% structurant) become less hard on any admixture. Beeswax (BW)-based gels show significant increases in hardness when 25% and 50% (w/w) hydrolyzate are admixed. This could be related to stepwise crystallization. Further analysis reveals that the dissolution/melting behavior of the wax ester mixtures can be surprisingly well described as ideal solubility of a single pseudocomponent. The approach to unravel the individual contributions of the different species present in waxes is successful and marks a first step to better understand the systematic of wax functionality as oleogelators. Practical Application: The substitution of hardstock fats in structured oil phases is of interest for two reasons. The improved nutritional profile oleogels offer are beneficial for public health while the elimination of palm oil based ingredients appears to be a general public desire. Among the technical solutions for non-TAG oil structuring waxes are very promising. This is primarily due to their availability, prior consumption, potentially low cost for functionality. Currently waxes are technically and scientifically wrongly treated as single components. In order to better utilize the potential of waxes and design future sourcing strategies it is necessary to understand the wax functionality at a compositional/molecular level. This contribution marks the first step into this direction by considering classes of molecules with respect to their contribution to functionality. This understanding is considered as a key for future compositional design. 相似文献
5.
尖晶石纳米催化剂应用于烯丙醇多相氧化制烯丙醛或烯丙酮 总被引:2,自引:0,他引:2
使用共沉淀法通过Ru对MeFe2O4的同晶取供制备了纳米级MnFe1.95Ru0.05O4催化剂。在通过过渡金属进一步改性该催化剂的过程中,发现MnFe1.95Ru0.05O4的催化剂性能优异于文献报道的其他多相醇氧化催化剂,XRD测试表明该催化剂仍保持尖晶石结构。该纳米催化剂能有效地将不同烯丙醇类氧化成烯丙醛类或烯丙酮类,与文献报道的其他多相氧化催化体系相比,该催化剂具有更高的活性转换数。借助于EXAFS等表征结果和1-辛醇与4-辛醇的竞争反应,判断出单核的Ru类反应的活性中心,EXAFS的表征同时表明由于Cu的添加而产生的Ru=0能加快反应速率。作者在此基础上提出反应机理,认为Ru在反应过程中形成醇化物,再经过β消除反应生成相应的醛或酮。 相似文献
6.
Larvae and adults of the Colorado potato beetle,Leptinotarsa decemlineata (Say), are shown to have galeal gustatory cells that are highly sensitive to distillate of potato leaf extracts, (E)-2-hexen-1-ol, (E)-2-hexenal, and other saturated and unsaturated six-carbon alcohols. In larvae and adults, the sensory response patterns elicited by leaf homogenate, leaf distillate and a mixture of these two extracts differ in subtle ways. Beetle larvae feed most readily on Millipore disks treated with leaf homogenate and the mixture, but they did not feed on disks treated with leaf distillate. The differences in behavioral response and sensory input are used to derive a potential gustatory code that may stimulate different levels of feeding. This code may be disrupted by compounds present in nonhost leaves, thus leading to reduced feeding. Possible interactions of sapid leaf volatiles, amino acids, sugars, and potentially deterrent plant compounds are discussed. 相似文献
7.
Rana M. Tubaileh Antonio Garrido-Fernández M. Victoria Ruiz-Méndez Manuel León-Camacho Enrique Graciani-Constante 《Journal of the American Oil Chemists' Society》2002,79(1):101-104
Changes in the contents of waxes and fatty alcohols during deodorization/physical refining of bleached olive oil were studied.
Experiments were carried out with 1.85% acidity oil, which was physically refined in a discontinuous deodorizer of 250-kg
maximum capacity using nitrogen as stripping gas instead of steam. The variables studied were load and temperature of oil
in the deodorizer as well as N2 flow. Analyses of waxes and alcohols were carried out at different operation times. The maximum content of wax was always
observed when the oil reached the deodorization temperature. The variation in the wax content depended on temperature and
N2 flow. Wax decomposition started and continued during the operating time, and a progressive decrease, which was pronounced
between 3 and 4 h, was observed. Small changes in waxes were observed between 4 and 5 h. Total content of fatty alcohols diminished
throughout the operating time, and changes did not depend on the variables studied. 相似文献
8.
Three MgO surfaces of different structures have been employed as models for study of the acid-base properties of MgO. Surface spectroscopies including XPS, UPS, and ISS were used to determine the nature and the absolute coverage of surface intermediates, and the nature of bonding sites upon adsorption of Brønsted acid molecules on these surfaces. Different behavior patterns of the Brønsted acid molecules with varying strengths on the three model surfaces provide insights into the site requirements for dissociation of Brønsted acids on MgO. The base-catalyzed Cannizzaro reaction of formaldehyde was observed on these model surfaces under UHV conditions. 相似文献
9.
Secretions from the metathoracic glands (MTG) of the black locust bug, Lopidea robiniae (Uhler) (Heteroptera: Miridae) contained six major compounds, including (E)-2-hexenal, (E)-2-hexen-1-ol, (E)-2-octenal, (E)-2-octen-1-ol (E)-2-heptenal, and (Z)-3-octen-1-ol. Males and females did not differ significantly in the relative compositions of identified compounds. In feeding trials, six bird species [robin (Turdus migratorious), blue jay (Cyanocitta cristata), brown thrasher (Toxostoma rufum), killdeer (Charadrius vociferus), starling (Sturnus vulgaris), and house wren (Troglodytes aedon)] demonstrated feeding aversions towards L. robiniae, implying that black locust bugs are chemically defended. Bugs discharged the liquid contents of their MTG when attacked, thereby producing a strong and distinct odor. Some birds immediately ejected bugs out of their mouth after biting them, suggesting that the MTG secretion was a deterrent. 相似文献
10.
拓扑指数X用于脂肪醇的QSPR研究 总被引:1,自引:0,他引:1
为了更好地揭示脂肪醇的各种物理化学性质与结构的关系,通过对100余种饱和脂肪醇分子的拓扑结构特点的研究,提出1种新的拓扑指数X,并运用回归分析方法研究了饱和脂肪醇的沸点(BP)、空腔表面积(CSA)、折光指数(n_D)、光离子化灵敏度(SM),半数致死浓度(LC_(50)),疏水性参数(lgP)和味阀值(poL)等多种物理化学性质与拓扑指数X的相关性,建立了定量结构-性质相关(QSPR)模型。结果表明所建立的QSPR模型方程具有良好的稳定性和预测能力,较好地揭示了这些物理化学性质的变化规律。 相似文献