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991.
V. Indira Shivappa B. Halligudi C. Gopinathan 《Reaction Kinetics and Catalysis Letters》2001,73(1):99-107
Tetraalkylammonium (TAA) salts of transition metal substituted dodecatungstophosphate, (TAA)5PW11O39.H2O (where TAA = (C2H5)4N (TEA), (C3H7)4N (TPA), and (C4H9)4N (TBA), and M = Mn 2+ , Fe 2+ and Co2 ) catalyzed the oxidation of styrene with H2O2 at 353 K. Except for the Mn 2+ salt, other TAA salts were found to be active and gave mainly benzaldehyde and styrene oxide products. Among the catalyst tested, TBA (tetrabutylammonium) salt of Co 2+ was more active in styrene oxidation. Kinetics of TBA-PW11CoO39 catalyzed oxidation of styrene have been investigated and mehanism for oxidation of styrene has been proposed. 相似文献
992.
The viscosity B coefficients were measured for LiBr, NaBr, KBr, RbBr, CsBr, Bu4NBPh4 and Bu4NBr in 3-hydroxypropionitrile–acetonitrile mixtures over the entire composition range at 25°C. The B coefficients of these electrolytes were large and positive and were split into their respective ionic values using the method of Gill and Sharma. The ionic B coefficients were positive for all the electrolytes. 相似文献
993.
R.R. Netz 《The European physical journal. E, Soft matter》2001,5(2):189-205
Using a field-theoretic formalism, we calculate the static contribution to the van der Waals interaction between two dielectric
semi-infinite half-spaces in the presence of mobile salt ions. The ions can be located in the slab, in one, or in both half-spaces.
We include an excess polarizability of the salt ions, i.e., each (spherical) ion has a dielectric constant which in general is different from the surrounding medium. This leads to
a modification of the effective dielectric constant of the medium hosting the ions. This shift can be large for high salt
concentrations and therefore influences the Hamaker constant decisively. Salt ions in the slab screen the static van der Waals
interaction, as was shown by Davies and Ninham. The salt-modified van der Waals interaction also contains salt-confinement
and salt-correlation effects. This is clearly demonstrated by the fact that the interaction is non-zero even in the case when
the dielectric constant is homogeneous throughout the system, in which case salt correlations are solely responsible for the
interaction. If the salt ions are in one or both of the two half-spaces (and no ions in the slab), the van der Waals interaction
is not screened but the effective Hamaker constant approaches a universal value for large slab thickness which is different
from the value in the absence of salt ions and which is independent of the salt concentration and of the effective electrolyte
dielectric constant. If both half-spaces contain salt, the asymptotic value of the Hamaker constant for large separation between
the half-spaces is the one obtained for the interaction between two metallic half-spaces through an arbitrary dielectric medium,
which is given by A≃ - 1.20. As is explicitly demonstrated, ion enrichment or depletion at the interfaces due to image-charge effects is already
included on the one-loop level and therefore does not lead to a change of the screened van der Waals interaction as given
by Davies and Ninham. For positive and negative ions with different valencies or different excess polarizabilities, we obtain
different adsorbed surface excesses of positive and negative ions, leading to a non-vanishing surface potential, which is
computed explicitly. All of these results are obtained on the linear one-loop level. For a special case we extend the calculation
of the dispersion interaction to the two-loop level. We find the corrections to the one-loop results to be quite large for
high salt concentrations or multivalent ions.
Received 17 February 2000 相似文献
994.
The effect of fixed discrete colloidal charges in the primitive model is investigated for spherical macroions. Instead of
considering a central bare charge, as it is traditionally done, we distribute discrete charges randomly on the sphere. We use molecular dynamics simulations to study this effect on various properties such as
overcharging, counterion distribution and diffusion. In the vicinity of the colloid surface the electrostatic potential may
considerably differ from the one obtained with a central charge. In the strong Coulomb coupling, we showed that the colloidal
charge discretization qualitatively influences the counterion distribution and leads to a strong colloidal charge-counterion
pair association. However, we found that charge inversion still persists even if strong pair association is observed.
Received 30 June 2000 and Received in final form 28 November 2000 相似文献
995.
用等温热重技术研究了三种新型尾式卟啉-三乙胺和吡啶季铵盐的热稳定性及寿命。得到了失重10%为寿终指标的寿命方程及稳定性大小的顺序。 相似文献
996.
Chlorofluorocarbons (CFCs) such as CCl_2F_2 have been widely used as refrigerants, blowing agent etc. due to their remarkable properties, however for the global environmental concerns, they have been prohibited in production and use because of their ozone depletion effect and greenhouse effect1. Nevertheless there are still several million tons of CFCs in use all over the world, close attentions have been paid to the operable handling techniques and environmentally benign alternatives. Amon… 相似文献
997.
Our serial studies from 1970s on chemical composition, structure determination and formation mechanism of gallstones were reviewed. The chemical component investigation of brown-pigment gallstone demonstrated that it consists of macromolecules such as proteins, glyco-proteins, polysaccharides, bilirubin polymers and pigment polymers, and biomolecules such as cholesterol, bile salts, calcium salts of carbonate, phosphate, fatty acids and bilirubinate as well as various metal ions. The binding of metal ions with bile salts and bilirubin plays important roles in gallstone formation, i.e., calcium bilirubinate complex is the major constitute of brown-pigment gallstones, and copper bilirubinate complex is critical in the black color appearance of black-pigment gallstone. The cross section of many gallstones exhibits a concentric ring structure composed of various small particles with a fractal character. This is nonlinear phenomenon in gallstone formation. A typical model system of metal ions-deoxycholate (or cho 相似文献
998.
V. P. Litvinov Ya. Yu. Yakunin V. D. Dyachenko 《Chemistry of Heterocyclic Compounds》2001,37(1):37-76
Published data on the synthesis of various heterocyclic compounds by the reaction of nucleophiles with electrophilic olefins containing a nucleophilic group are reviewed and analyzed. 相似文献
999.
R. V. Seller P. V. Reshetov A. P. Kriven''ko 《Chemistry of Heterocyclic Compounds》2001,37(7):797-821
Published data and the results of the authors' own investigations on the synthesis of six-membered saturated N-, O-, and S-containing heterocycles by catalytic reduction of pyridinium, pyrylium, and thiopyrylium salts are reviewed. The conditions, laws, and special characteristics of the reactions are considered. 相似文献
1000.
锂离子电池非水电解质锂盐的研究进展 总被引:5,自引:1,他引:4
新型电解质锂盐主要包括含螯合硼阴离子、螯合磷阴离子、全氟膦阴离子、烷基磺酸阴离子、全氟烷基、亚胺基的有机锂盐及有机铝酸锂盐.本文综述了近年来在新型电解质锂盐研究与探索方面的成果,介绍了锂离子电池电解质锂盐的合成方法、组成与结构、化学和电化学性能及其与结构的关系,并阐述今后电解质锂盐研究的可能发展方向及研究方法. 相似文献