Yu. P. Semushina

Double complex salts [Ni(NH3)6]3[Fe(CN)6]2 and [Ni(NH3)6]3[Cr(CNS)6]2: Synthesis and properties

The double complex salts [Ni(NH3)6]3[Fe(CN)6]2 and [Ni(NH3)6]3[Cr(CNS)6]2 were synthesized and their thermal decomposition in air was studied. The values of interplanar distances in crystal lattices were determined. The compounds are proposed as precursors for producing homogeneous bimetallic nanodimensional powders.

Acid−base and catalytic properties of the products of oxidative thermolysis of double complex compounds

Acid–base properties of the products of thermal decomposition of [М(А)6]х[М1(L)6]у (where M is Co, Cr, Cu, Ni; M1 is Fe, Cr, Co; A is NH3, 1/2 en, 1/2 pn, CO(NH2)2; and L is CN, 1/2C2O4) binary complexes in air and their catalytic properties in the oxidation reaction of ethanol with atmospheric oxygen are studied. It is found that these thermolysis products are mixed oxides of the central atoms of complexes characterized by pH values of the zero charge point in the region of 4–9, OH-group sorption limits from 1 × 10–4 to 4.5 × 10−4 g-eq/g, OH-group surface concentrations of 10–50 nm–2 in 0.1 M NaCl solutions, and Ssp from 3 to 95 m2/g. Their catalytic activity is estimated from the apparent rate constant of the conversion of ethanol in CO2. The values of constants are (1–6.5) × 10–5 s–1, depending on the gas flow rate and the Ssp value.

Adsorption affinity of anions on metal oxyhydroxides

The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO43−, CO32− > C2O42−, C(OH)(CH2)2(COO)33−, (CHOH)2(COO)22− > CrO42− ≫ SO42−.

Relationship between the catalytic properties of the products of the oxidative thermolysis of certain complexes and the porous structures of samples in the oxidation reactions of volatile organic compounds

The rate of the gas-phase oxidation of ethanol, 2-propanol, acetone, ethyl acetate, dioxane, and benzene with atmospheric oxygen is studied on surfaces of bimetallic oxide catalysts Co–Fe, Cu–Fe, Cr–Co, and Ni–Fe, prepared via thermal decomposition of double complex compounds in air. It is found that the rate of oxidation of volatile compounds depends on the volume of the transient pores in the catalyst sample. The rate of oxidation on the same catalyst at 350°C depends on the nature of the substance in the order: acetone > ethyl acetate > ethanol > propanol > dioxane, benzene.

Binary complexes [Co(A)6][M(C2O4)3] (A = NH3, 1/2C2H8N2, M = Fe, Cr): Synthesis, properties, and thermal decomposition

Binary complexes [Co(A)6][M(C2O4)3] (A = NH3, 1/2C2H8N2, M = Fe, Cr) are synthesized, and their physicochemical properties and thermal decomposition in air, argon, and hydrogen are studied. The qualitative and quantitative analyses are carried out for the solid and gaseous thermolysis products. Similar regularities are revealed in the behavior of complexes [Co(NH3)6][Fe(C2O4)3] (I), [Co(En)3][Fe(C2O4)3] (II), [Co(NH3)6][Cr(C2O4)3] (III), and [Co(En)3][Cr(C2O4)3(IV). The solid thermolysis product for complexes I and III in argon at 225 and 300°C is Co(NH2)2M(C2O4)2, respectively; and that for complexes II and IV at 280 and 380°C is Co(En)2M(C2O4)2. The gaseous thermolysis products are CO and CO2, NH3, En partially isolated upon thermal destruction, other products of En destruction, and En itself. Complex III forms the most highly dispersed solid products in a range of 300–400°C.

Thermal decomposition of [Co(NH3)6][Fe(C2O4)3]•3H2O in inert and reductive atmospheres

The thermal decomposition of [Co(NH3)6][Fe(C2O4)3]•3H2O in hydrogen and helium atmospheres was studied. The thermal decomposition of the complex proceeds via the same four steps in a temperature range of 50—430 °C, regardless of the atmosphere. The thermolysis processes in inert and reductive atmospheres differ by the nature of the final solid products: a Co0.5Fe0.5 alloys is formed in a hydrogen atmosphere, and a mixture of iron and cobalt oxides is observed for an inert atmosphere. The major gaseous decomposition products are H2O, NH3, CO2, and CO.

Thermal behavior of binary complex сompounds сontaining the hexacyanoferrate anion

The thermal behavior of compounds with the general formula [MA6]x[Fe(CN)6]y (M = Со, Cu, Ni, A = NH3, 1/2 C3H10N2) in air, argon, nitrogen, and hydrogen at temperatures between 20 to 1000°C was studied. The study involved measurement of TG–DSC–DTG curves and analysis of solid and gaseous thermolysis products. It was found that the process is not affected by the nature of the atmosphere up to about 200°C. The coordinated cyanide ion partially releases as hydrogen cyanide. The destruction of diamines forms NH3, and a large amount of carbon remains in the solid phase.

Sorption of chromate ions on oxyhydroxides prepared from iron(III) and aluminum sulfates

Sorption properties with respect to the chromate ions of ferro- and alumogels prepared from Fe(III) and aluminum sulfates, and the composition of oxyhydroxides (OH), are studied. It is determined that the sorption values of chromate ions on ferrogels and alumogels (with NaCl) are notably higher than those on OH prepared from other precursors. It is shown that the sorption of CrO42− on alumogels with Na2SO4 is almost completely inhibited. It is found that gels retain substantial amounts of sulfate ions during precipitation from precursor solutions, while alumogels retain substantially more than ferrogels. The sorption of SO4-gels is explained from the viewpoint of their composition and interaction with Na2SO4 solution. The competitive sorption of chromate and phosphate ions is studied and it is demonstrated that phosphate ions completely inhibit the sorption of chromate ions at comparable concentrations.

Effect of the Nature of the Salt Precursor of an Oxide-Hydroxide Sorbent on the Sorption of Oxalate Ions

Generalizations are made on the effect of the nature of a precursor (the original salt of a metal) on the sorption activity of hydrogels of oxidehydroxides (OHes) towards oxalate ions using the example of an OH obtained by the alkaline hydrolysis of chloride, perchlorate, and sulfate of Fe(III); chloride, sulfate, and nitrate of Al; and nitrate of Zr(IV). It is established that the sorption of C2O42− on the studied OHes is described by the Langmuir equation. We find that the sorption activity depends on the nature of the precursor: Al2(SO4)3 > Al(NO3)3 > AlCl3 > ZrO(NO3)2 > Fe2(SO4)3 > FeCl3 > Fe(ClO4)3.

Interaction of components of electrode coatings with liquid glass during heating

Structural and chemical changes are considered at contact of some coating materials and sodium–potassium or sodium liquid glass solutions. Behaviour and phase composition of stock mix for the welding electrode coating ingredients are determined by the methods of thermal and roentgen-phase analyses.