Russian Journal of Physical Chemistry A

Calculations of the glycerol dehydration process on protonated mordenite have been carried out withing the framework of the density functional theory method on the B3LYP/6–311G level, taking into account non-covalent interactions. Both reactions considered, dehydration to acrolein and to acetol, are endothermic (27.3 and 11.7 kcal/mol, respectively). It has been shown that, unlike ZSM-5, the acetol formation pathway is more preferable for mordenite.

The surface texture, thermal and catalytic characteristics of the CO hydrogenation catalyst promoted by Fe/MgAl(2) O4 samarium (Sm:Fe ratio = 1:100) prepared by different methods of introducing the promoter into its composition have been determined. It was found that the best catalytic properties are shown by the Sm/Fe/MgAl(2) O4system, where samarium is deposited over the Fe/MgAl(2) O4 catalyst: selectivity for hydrocarbons C(5+)= 84.6% and chain growth index α = 0.862, for CO2= 3.0%.

Two series of catalysts of CrOx-SBA-15 composition obtained by different methods – co-precipitation with a carrier and impregnation by moisture impregnation, varying the chromium content in the catalyst from 3 to 7 wt % – were synthesized and investigated in this work. The obtained materials were investigated by nitrogen adsorption, UV–VIS SDS and IR SDS methods using CD3CN as a test molecule. On 3 wt % Cr-SiO2catalyst prepared by co-precipitation, a propylene selectivity of 78% was achieved with a propane conversion of 14% at 600°C.

The protonation constants of cryptand[2.2] in aqueous dimethylsulfoxide solutions in the range of DMSO concentrations 0.0–0.9 mol fraction were determined by potentiometric titration method at T = 298 K. It was found that with increasing concentration of dimethyl sulfoxide in solution there is an extreme with minimum change of equilibrium constants of reactions of formation of mono- and biprotonated cryptand[2.2]. Comparison of the obtained data with literature data demonstrates that a similar character of the dependence of protonation constants on the solvent composition of water-dimethylsulfoxide is observed for the majority of nitrogen-containing compounds. The numerical value of protonation constants of cryptand[2.2] in anhydrous dimethylsulfoxide solution was estimated by calculation.

The first-order recurrence relations A(nC + 1) = aA(nC) + b are applicable for approximation of variations of various properties of organic compounds (A) in homologous series, otherwise, depending on the number of carbon atoms in molecules, nC. However, they are unsuitable for approximation of melting temperatures (Tmel) because of the alteration of their values in homologues with even and odd number of carbon atoms in molecules for many series. It is confirmed that the solution of this problem is possible using the second-order recurrence relations, A(nC + 2) = aA(nC) + b. An explanation of this fact is proposed: the algebraic nonrecurrence solution of this recurrence equation, contains the denominator (–√а)ⁿC, the sign of which is a function of parity or oddness of the number of carbon atoms in the molecule. Such kind of functions for characterization of alternating properties of homologues is proposed for the first time. It is shown that in order to achieve the greatest accuracy of approximation, preliminary statistical processing of Tmelt values from different sources with calculation of mean values, their standard deviations, and rejection of unreliable data is necessary. As an example of such processing, the example of T(fused) of n-alkancarboxylic acids with 0 ≤ nC ≤ 35 is considered in detail. The errors of the recurrence approximation of Tplavl homologues by the characterized method do not exceed the standard deviations of randomized interlaboratory data.

The sorption ability of the synthesized polymer based on carboxymethylcellulose and glycidylacrylate towards Cu2+, Ni2+, Fe2+, Mn2+ ions has been studied. It has been shown that the sorption of metal ions is reliably described by the Langmuir model, and the process itself has a physical character. By the method of thermogravimetric analysis it has been established that the process of thermodegradation of the polymer occurs in three steps, and of its complex with copper – ​in four steps. The activation energy of decomposition of the initial polymer for each step is in the range of 29–57 kJ/mol, and for its complex with copper – ​58–120 kJ/mol. The introduction of Cu(II) increases the thermostability of the obtained polymer based on carboxymethylcellulose.