S. I. Pechenyuk

Synthesis, properties, and thermal decomposition of compounds [Co(En)3][Fe(CN)6] · 2H2O and [Co(En)3]4[Fe(CN)6]3 · 15H2O

Binary complex salts, [Co(En)3][Fe(CN)6] · 2H2O and [Co(En)3]4[Fe(CN)6]3 · 15H2O, are synthesized. The properties of the salts and their thermolysis in air, dihydrogen, and argon are studied. Oxides of the central ions of the binary complex salts are found to be the thermolysis products in an oxidative atmosphere. Solid solutions (intermetallic compounds) CoFe are the thermolysis products in the reductive atmosphere, whereas intermetallides containing considerable amounts of C and N and an impurity of Co and Fe oxides are the thermolysis products in an inert atmosphere. Gaseous thermolysis products in dihydrogen and argon are NH3, hydrocarbons, and ethylenediamine.

The complexes [Ni a (Pn) b ] x [Fe(CN)6] y (Pn = 1,3-Diaminopropane): Synthesis and thermolysis

The complexes [Ni(Pn)2]2[Fe(CN)6] · 3H2O (I), [Ni3(Pn)5][Fe(CN)6]2 · 9H2O (II), [Ni5(Pn)9][Fe(CN)6]3 · 9H2O (III), and [Ni(Pn)2]3[Fe(CN)6]2 · 6H2O (IV) (Pn = 1,3-diaminopropane) were obtained. Their thermolysis was studied in oxidative (air), reductive (hydrogen), and inert atmospheres (argon) in a temperature range from 20 to 1000°C. Solid and gaseous products of the thermolysis were identified. In air thermolysis, the carbon of the ligands is eliminated as CO and CO2; the solid residues consist of nickel oxide, iron oxides, and the intermetallide Ni3Fe. In hydrogen thermolysis, the ligands are eliminated partially unchanged and partially hydrogenated to ammonia and hydrocarbons. The solid residue at >550°C consists of bimetallic phases with a small carbon impurity. In argon thermolysis, the ligands are eliminated partially unchanged or as fragments of the Pn molecule. The solid residues produced by calcination contain a mixture of metal and oxide phases and 10 to 20% of the initial carbon content.

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.

Products of binary complex compounds thermolysis: Catalysts for hydrogen peroxide decomposition

Samples are obtained via the thermolysis of binary complex compounds in a hydrogen atmosphere. Their catalytic activity in hydrogen peroxide decomposition is studied. The values of the rate constants and activation energies for the catalytic reaction are estimated. The correlation between catalytic activity, composition, specific surface area (Ssp), and particle size of the samples is analyzed.

Thermal decomposition of iron cyano complexes in an inert atmosphere

The thermal decomposition of K3[Fe(CN)6] (1), [Co(NH3)6][Fe(CN)6] (2), [Co(NH3)6]4[Fe(CN)6]3•13H2O (3), Ni3[Fe(CN)6]2•20H2O (4), and [Ni(NH3)6]3[Fe(CN)6]2 (5) was studied in an inert atmosphere (argon and nitrogen) in the temperature range from 20 to 1000 °С. The TG—DSC—DTG curves were obtained. The analyses of solid thermolysis products of compounds 1—5 and gaseous thermolysis products of compounds 1 and 5 were carried out using IR spectroscopy. Depending on temperature, the solid thermolysis products of K3[Fe(CN)6] (1) are K4[Fe(CN)6], Fe4[Fe(CN)6], KCN, Fe3C, and C, and the gaseous thermolysis products are (CN)2 and N2. A deficient of potassium is observed in the residues obtained at ≥800 °С. The thermal decomposition of compounds 2—5 is accompanied by the evolution of Н2О (3, 4), NH3, N2, and HCN. Free metals Co and Fe and intermetallic compounds CoFe, FeNi, and Ni3Fe in a mixture with carbon (25—60% of the initial C content in the complex) are formed in the solid state. Gaseous (CN)2 is formed only in the case of compound 1. The thermolysis of the hydrogen-containing complexes gives HCN.

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.

The thermal behavior of double complex compounds with the cation [Cr(ur) 6 ] 3+ in a reducing atmosphere

The thermal behavior of double complex compounds (DCC) [Cr(ur)6][Co(CN)6]·4H2O (I), [Cr(ur)6][Co(C2O4)3]·3.5H2O (II), [Cr(ur)6][Fe(CN)6]·4H2O (III), [Cr(ur)6][Fe(C2O4)3]·2H2O (IV) and urea (ur) was studied (uru2009=u2009urea, H2NCONH2). Thermal decomposition was carried out by the TG-MS method and method of static experiments in the reducing atmosphere at a 1-h exposure. The final thermolysis products are characterized by elemental analysis, XDR, IR spectrometry, SEM, the specific surface area (SBET) of the samples. The porous structure of the samples was determined. Cr2O3u2009+u2009Co0 are formed as a result of thermal reduction of I, II, Cr2O3u2009+u2009Fe0u2009+u2009Fe2O3 for III, FeCr2O4u2009+u2009Fe0 for IV. The replacement of CN− ligands by C2O42− ligands leads to an increase in the specific surface by a factor of ~u20092. Catalytically activity of Co-containing degradation products is demonstrated in the model catalytic decomposition of H2O2. The relationship between SBET and the obtained values of the rate constants of the reaction is not observed. Fe-containing samples are not catalytically active.

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.