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51.
The catalytic function of the previously synthesized and characterized [(L)MoFe(3)S(4)Cl(3)](2)(-)(,3)(-) clusters (L = tetrachlorocatecholate, citrate, citramalate, methyliminodiacetate, nitrilotriacetate, thiodiglycolate) and of the [MoFe(3)S(4)Cl(3)(thiolactate)](2)(4)(-) and [(MoFe(3)S(4)Cl(4))(2)(&mgr;-oxalate)](4)(-) clusters in the reduction of N(2)H(4) to NH(3) is reported. In the catalytic reduction, which is carried out at ambient temperature and pressure, cobaltocene and 2,6-lutidinium chloride are supplied externally as electron and proton sources, respectively. In experiments where the N(2)H(4) to the [(L)MoFe(3)S(4)Cl(3)](n)()(-) catalyst ratio is 100:1, and over a period of 30 min, the reduction proceeds to 92% completion for L = citrate, 66% completion for L = citramalate, and 34% completion for L = tetrachlorocatecholate. The [Fe(4)S(4)Cl(4)](2)(-) cluster is totally inactive and gives only background ammonia measurements. Inhibition studies with PEt(3) and CO as inhibitors show a dramatic decrease in the catalytic efficiency. These results are consistent with results obtained previously in our laboratory and strongly suggest that N(2)H(4) activation and reduction occur at the Mo site of the [(L)MoFe(3)S(4)Cl(3)](2)(-)(, 3)(-) clusters. A possible pathway for the N(2)H(4) reduction on a single metal site (Mo) and a possible role for the carboxylate ligand are proposed. The possibility that the Mo-bound polycarboxylate ligand acts as a proton delivery "shuttle" during hydrazine reduction is considered. 相似文献
52.
A model for the dynamics of isothermal absorption of a binary mixture of an organic substance, soluble in water, and water
vapor in a fixed bed of activated carbon was proposed. It includes the equations of material balance and the Myers—Prausnitz
model for equilibrium adsorption. The possibility of formation of the condensed phase during the adsorption of an organic
substance on moist activated carbon was shown.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1491–1495, August, 1998. 相似文献
53.
The ion-exchange equilibria involving K+ and Ca2+ cations were studied using the Na-forms of nine different clinoptilolite samples. The high-silica (in the native state, sodium–potassium form) clinoptilolites were shown to have the increased selectivity with respect to K+ ions, whereas the low-silica (in the native state, calcium form) clinoptilolites to Ca2+ ions. The phenomenon found is interpreted as a structural memory of clinoptilolites with respect to alkali and alkaline-earth metal ions which had been present during zeolite crystallization under natural conditions. 相似文献
54.
V. A. Polyakov 《Mechanics of Composite Materials》1976,12(3):393-399
The state of stress of rings of different thickness with high degrees of anisotropy 2=E/Er, 2=Egq/Gr is analyzed on the basis of the solution of the plane problem for a cylindrically orthotropic body. The accuracy of the stress determination in accordance with approximate theories of bending of curved bars is estimated. The radial tensile stresses that develop when rings are bent by concentrated loads are calculated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 445–452, May–June, 1976. 相似文献
55.
R. S. Borisov A. I. Polyakov L. A. Medvedeva N. I. Guranova L. G. Voskressensky 《Russian Chemical Bulletin》2012,61(8):1609-1615
Tetrazolo[1,5-a][1,4]benzodiazepines were obtained by an efficient azide five-centered four-component Ugi reaction, which used ketones, sodium azide, ammonium chloride, and the corresponding isonitrile. Scope and limitations of this multi-component reaction were considered. 相似文献
56.
Mathematical Notes - 相似文献
57.
Dr. Sébastien Lemouzy Florian Cuminet Dimitri Berne Dr. Sylvain Caillol Dr. Vincent Ladmiral Prof. Rinaldo Poli Dr. Eric Leclerc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202201135
Vitrimers are a third class of polymers gathering the mechanical properties and solvent resistance of 3D thermosets and the reprocessability of thermoplastics. This unique behaviour is due to the triggering of certain covalent exchange reactions that allow the network to rearrange upon application of a stimulus. The constitutive feature of vitrimers is the adoption of a glass-like viscosity during the rearrangement of the network, often due to an associative mechanism for the exchange reaction. Transesterification networks are one of the most studied type of vitrimers that usually require the incorporation of a catalyst, implying the associated drawbacks. Following up on a recent report on catalyst-free transesterification vitrimers in which the ester functions are particularly reactive thanks to the presence of fluorine atoms in α- or β-position, parallel DFT calculations and an experimental kinetic study on model molecules are presented in order to quantitatively assess the effect of neighbouring fluorinated groups on the transesterification reaction rate. 相似文献
58.
A. N. Polyakov M. Noltemeyer T. Hempel J. Christen M. A. Stepovich 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(9):970-973
The use of time-of-flight cathodoluminescence measurements in the studies of semiconductor samples partially covered with a light-absorbing mask of special geometry in order to obtain new quantitative information about the properties of materials is shown. The values of the exciton diffusion coefficient are determined from the results obtained in an experimental study of gallium nitride. 相似文献
59.
T. N. Gerasimenko V. I. Ivanov P. A. Polyakov Yu. V. Popov 《Journal of Mathematical Sciences》2011,172(6):761-769
Using the conformal-mapping technique, we have found analytical solutions of the current-distribution problem for different configurations of plain conductors. 相似文献
60.