The effect of different regimes of combustion of glycine–nitrate precursors on the formation of perovskite phases (LaMnO₃ and LaCrO₃) without additional heat treatment was studied. The following three combustion regimes were compared: the traditional solution combustion synthesis (SCS), volume combustion synthesis (VCS) using a powdered precursor, and self-propagating high-temperature synthesis (SHS) using a precursor pellet. The products of combustion were studied using a series of physicochemical methods (attenuated total reflection infrared spectroscopy (ATR FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermal analysis). SHS was found to be the most productive regime for the formation of perovskite because of its ability to develop high temperatures in the reaction zone, which led to a reduced content of the thermally stable lanthanum carbonate impurities and to an increased yield and crystallite size of the perovskite phase. The reasons for the better crystallinity and purity of LaCrO₃ as compared with LaMnO₃ is also discussed, namely the low temperatures of the onset of the thermolysis, the fast rate of combustion, and the favorable thermodynamics for the achievement of high temperatures in the reaction zone.

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO₂ methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H₂-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO₂. In addition, the synthesized catalyst had higher activity in low-temperature CO₂ methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

In this work two approaches to the synthesis of energetic complex compound Ni(Im)₆(NO₃)₂ from imidazole and nicklel (II) nitrate were applied: a traditional synthesis from solution and a solvent-free melting-assisted method. According to infrared spectroscopy, X-ray diffraction, elemental and thermal analysis data, it was shown that the solvent-free melt synthesis is a faster, simpler and environmentally friendly method of Ni(Im)₆(NO₃)₂ preparation. The results show that this compound is a promising precursor for the production of nanocrystalline Ni-NiO materials by air-assisted combustion method. The combustion of this complex together with inorganic supports makes it possible to synthesize supported nickel catalysts for different catalytic processes.

The paper presents a comparative study of the activity of magnetite (Fe₃O₄) and copper and cobalt ferrites with the structure of a cubic spinel synthesized by combustion of glycine-nitrate precursors in the reactions of ammonia borane (NH₃BH₃) hydrolysis and hydrothermolysis. It was shown that the use of copper ferrite in the studied reactions of NH₃BH₃ dehydrogenation has the advantages of a high catalytic activity and the absence of an induction period in the H₂ generation curve due to the activating action of copper on the reduction of iron. Two methods have been proposed to improve catalytic activity of Fe₃O₄-based systems: (1) replacement of a portion of Fe²⁺ cations in the spinel by active cations including Cu²⁺ and (2) preparation of highly dispersed multiphase oxide systems, involving oxide of copper.

The development of solvent-free techniques for nanoparticles synthesis is one of the challenges of Green chemistry. In this work, the principled opportunity to obtain copper-containing nanosized particles without use of any solvents was shown. The copper complexes were prepared as precursors by the melting-assisted solvent-free synthesis. The formation of tetra(imidazole)copper(II) nitrate complex was confirmed by XRD, elemental analysis, FTIR spectroscopy, and thermal analysis. It was noted that their thermal decomposition occurs in two stages: (I) the low-temperature step may be related to redox interaction between organic ligands and nitrate-anions; (II) the high-temperature step may be related to the oxidation of the products of incomplete imidazole decomposition. TEM and XRD studies of solid products of complex combustion have shown that they are oxides with particle size less than 40 nm. Thus, the combustion of [Cu(Im)₄](NO₃)₂ complex under air can be considered as a new approach to prepare nanosized particles of copper oxides without the use of solvents.

The solid-state combustion method was used to prepare nickel-based catalysts for CO₂ hydrogenation from [Ni(C₃H₄N₂)₆](NO₃)₂ and [Ni(C₃H₄N₂)₆](ClO₄)₂. These complexes were synthesized by adding nickel nitrate and perchlorate to melted imidazole. The composition and structure of the obtained complexes was confirmed by ATR FTIR, powder XRD, and elemental analysis. The stages of thermal decomposition of the complexes and their kinetic parameters were established. It was found that incomplete gasification of more thermostable Ni(C₃H₄N₂)₆](ClO₄)₂ led to the formation of carbon, nitrogen, and chlorine impurities. According to powder XRD and XPS, the solid products of gasification of both complexes consist of NiO and Ni⁰ covered with nickel hydroxide and/or a carbonate layer. In the case of the sample prepared from [Ni(C₃H₄N₂)₆](ClO₄)₂, this layer was pronounced. Therefore, it limits the nickel reduction in the reaction medium of CO₂ hydrogenation, even at 450 °C. The surface of the sample prepared from [Ni(C₃H₄N₂)₆](NO₃)₂ contains nickel oxide, which is easily reduced. So, the catalyst active phase is already formed at 250 °C in the presence of CO₂ and efficiently catalyzes CO₂ hydrogenation as the temperature increases. Therefore, [Ni(C₃H₄N₂)₆](NO₃)₂ is a promising precursor for the CO₂ hydrogenation catalyst, and its solvent-free synthesis follows Green Chemistry principles.