Theoretical studies on vibrational spectra of some halides of Group IIB elements

The vibrational spectra of Group IIB elements halides MX2 and their dimers M2X4 (M=Zn(II), Cd(II) and Hg(II); X=F, Cl, Br and I) have been systematically investigated by ab initio RHF and B3LYP methods with LanL2MB, LanL2DZ and SDD basis sets. The optimized geometries, calculated vibrational frequencies are evaluated via comparison with the experimental data. The vibrational frequencies, calculated by these methods with different basis sets, are compared to each other too. The best results can be obtained by RHF/SDD method, with this method, the deviations for MX2 and Hg2X4 are <7%. Some vibrational frequencies of M2X4 that have not been experimentally reported are also predicted.     

EPR study of the nature of active sites and the type of their deactivation in CO hydrogenation on (Ni+Ti)/SiO2 catalysts

As shown by EPR, upon supporting Ni(-C₃H₅)₂ on Ti/SiO₂, the Ni complex is coordinated to Ti³⁺ ions. Deactivation of (Ni+Ti)/SiO₂ catalysts so obtained during CO hydrogenation is due to the oxidation of Ti³⁺ ions and metallic nickel particles by reaction products.

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, Ni(-C₃H₅)₂ Ti/SiO₂ Ni Ti³⁺. , (Ni+Ti)/SiO₂ CO Ti³⁺ .

     

GC–MS analysis of phenolic compounds in fuels after conversion to trifluoroacetate esters

The GC–MS characteristics of trifluoroacetate esters of phenolic compounds are discussed. Linear temperature programmed retention indices and total ion current MS response factors of over 120 phenolic esters are reported. The main GC advantages from analysis of trifluoroacetate esters as compared to plain phenols are enhanced volatility and improved resolution. For example, the elution temperature of a given phenol is typically 50 °C greater than that of the corresponding trifluoroacetate ester. Also, while retention of compounds with two trifluoroacetate groups is only moderately greater than mono esters, underivatized dihydroxy compounds are very difficult to elute from any GC column. Complete resolution of isomeric C₀-, C₁- and C₂-alkylphenol esters is readily achieved on conventional fused silica GC columns; resolution of the corresponding underivatized compounds requires specialized GC columns with low temperature limits. In general, mass spectra of trifluoroacetate esters are more characteristic of a given structure than those of the corresponding phenols and may be more rigorously interpreted towards structural elucidation. A table in the report summarizes some of the more important spectral features used in compound identification. Example applications in analysis of coal-, shale- and petroleum-derived materials are presented. Selected ion monitoring is used to determine individual phenolic components in whole distillates; reconstructed ion chromatograms are used to illustrate distributions of selected species as a function of fuel storage and thermal stress.     

Effect of explosion on the catalytic activity and selectivity of natural fluorite

The effect of various types of shock waves on the catalytic activity of natural fluorite in isopropanol dehydrogenation and dehydration reactions has been studied. Shock treatment is shown to decrease the catalytic reaction temperature and to increase the selective

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Effect of the introduction of certain additives to the CO + H2 mixture and the scheme for the formation of alcohols higher than C1

The effect of additions of certain alcohols (methanol, ethanol, 2-propanol, and 2-butanol) to the synthesis gas on the distribution of the products during the hydrogenation of CO to alcohols at zinc-chromium oxide catalysts, promoted by various amounts of K₂O, was studied. The results demonstrate the fundamental applicability of the principal theories of chain growth proposed by other authors for copper-containing catalysts. However, it was shown that the probability of -addition is lower while that of -addition is higher at the zinc-chromium-potassium catalysts than at copper-containing catalysts, and the calculated amounts of isobutanol obtained from the data for ethanol and propanols do not agree with the experimental data. It was found that there is an isomeric transition from the secondary alcohols (2-propanol, 2-butanol) to the primary alcohols at the surface of the catalyst, and this can evidently change the normal course of chain growth in the alcohols. It can be concluded that the activity of the alcohol added to synthesis gas in reaction with other C-fragments present on the surface of the catalyst increases with increase in the number of carbon atoms in the alcohol.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 501–505, July–August, 1990.     

A generalization of Bernoulli's model occurring in order statistics II

The frequency of occurrences of events in a modified Bernoulli model under the assumption F_x(u) F_y(u) is studied. A homogeneity test for two samples based on properties of this frequency and its properties are investigated.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 6, pp. 779–786, June, 1991.     

Fluctuations in an averaging scheme for parabolic boundary-value problems

The initial/boundary value problem for a parabolic equation in which the lower-order terms have random coefficients depending on a small parameter is studied. In doing this the joint distribution of the coefficients, normalized by dividing by , converges to a limit distribution. It is proved that under certain natural additional hypotheses the distribution of the difference between the solution of the equation being studied and that of the limit equation converges to a distribution that can be easily expressed in terms of the limit distribution of the coefficients.Translated fromTeoriya Sluchaínykh Protsessov, Vol. 14, pp. 15–21, 1986.     

Solution of a Pólya-Szegö isoperimetric problem

There is given the solution of the problem of the maximum inner radius in the family of n-gons D_n, n3, of fixed area, and of some related extremal problems. The proof is carried out by the method of the modules of families of curves.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 168, pp. 140–153, 1988.     

On the asymptotics of convolutions of complex measures in Banach spaces

We study the problem of the asymptotics of the integral of a functiong with respect to a normalized and centeredn-fold convolution of finite complex measures _n on a separable reflexive Banach spaceX. Conditions for existence are given under the assumption that the functiong(x) is the Fourier transform of a finite complex measure on the conjugate spaceY and the corresponding limit is calculated.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 34–37, 1987.