Thermal decomposition of potassium, rubidium and caesium fluoroantimonates(III)

The acceleratory effect of potassium perchlorate on the reactivity of the red lead-silicon system has been studied by employing DTA and DSC. Supporting investigations on pure potassium perchlorate and the binary system red lead-potassium perchlorate suggest that the complex decomposition kinetics of potassium perchlorate drastically influences the oxidation of silicon. Further, the ternary system also undergoes a transition from exothermic smooth decomposition to ignition at a certain critical mass, as noted in the red lead-silicon and iron(III) oxide system. The criticality should be a result of the rise in temperature expressed as a perturbation of the steady-state energy conservation conditions, as postulated by Gray.

Effects of gas-phase mass transport in the pyrotechnic system red lead-silicon-potassium perchlorate

Finding green and profitable recovery methods has always been a great challenge for Li/Co recovery from LiCoO2 (LCO) in waste lithium-ion batteries (LIBs). A top priority was specially proposed on energy and material consumptions for the industrialization of carbothermal technology from an economic point of view. Meanwhile, pollution caused by plastic wastes including polyvinyl chloride (PVC) plastics has already become a serious environmental issue. Therefore, in this study, we proposed a PVC–LCO synergetic pyrolysis strategy for Li/Co recovery. Results showed that the LiCoO2 was fully destructed to Li2CO3, CoO, Co, and Cl-containing salts at 450 °C for 90 min with a PVC/LCO mass ratio of 1:1. The reaction temperature was decreased significantly in comparison to the ever-reported values of the carbothermal technology. High-purity Li and Co were then separated simply by water leaching, with a recovery rate of 92.50 and 94.85%, respectively. Simultaneous thermogravimetric–mass analysis, thermodynamic analysis, and density functional theory revealed the reaction mechanisms as three-stage PVC cracking together with Li/Co–Cl bond formation after Cl adsorption on surface Li/Co of LCO. Overall, the PVC synergetic pyrolysis strategy possessed distinct advantages owing to the remarkable energy-conserving and chemical-free features and provided an economical, green, and scalable solution for LIB recycle. 

Green and Energy-Saving Recycling of LiCoO2 by Synergetic Pyrolysis with Polyvinyl Chloride Plastics

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.

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Solvent-Free Synthesis of Nickel Nanoparticles as Catalysts for CO2 Hydrogenation to Methane

The organic–inorganic coordination polymer of the general formula {[NiL][Co(NCS)4]}n (where L = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) has been synthesized and characterized by IR, UV–Vis, DSC/TG, DTA/TG/MS methods. The magnetic behaviour of this complex has also been investigated within the temperature range 1.8–300 K. The IR spectrum indicates the presence of bridging M–NCS–M′ ligands. The absorption bands of UV–Vis spectrum confirm that the coordination environment of nickel(II) ions changes from square planar for [NiL](ClO4)2 to octahedral for {[NiL][Co(NCS)4]}n. The obtained compound is stable at room temperature, but within the range 246–282 °C decomposes in a three-stage process. The first step is associated with decomposition of the coordination polymer to the cationic [NiL]2+ and anionic [Co(NCS)4]2− units; the next two stages correspond to gradual decomposition of the macrocyclic ring. The value of molar magnetic susceptibility (χMT = 2.16 cm3 mol−1 K) indicates that the compound is paramagnetic.

{[NiL][Co(NCS)4]} n , an organic–inorganic coordination polymer (L = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)

The thermal decompositions of nickel(II), copper(II), cobalt(II) and manganese(II) perchlorates were studied by thermal analysis and kinetic measurements. Anhydrous perchlorates could not be prepared by heating and outgassing the samples in vacuum; oxides were obtained as the main solid decomposition products. In the case of cobalt and manganese perchlorates, oxidation of the metal ions was observed during the decomposition. In most cases the decompositions of the perchlorates followed the Avrami-Erofeyev kinetics. A correlation was found between the stabilities of the perchlorates and the effective field strengths of the cations.

J. Raskó

Papers

Study of the thermal decompositions of some transition metal perchlorates