Complex Processing of Adsorbent Used in the Purification of Hydrogen-Containing Gas

The problems of processing spent adsorbents with a high concentration of chemisorbed chlorine-containing compounds for their reuse are studied in this article. The genesis of the phase composition and morphology at all technological stages of thermochemical regeneration of the spent adsorbent - Axstrap-860 by means of alkaline modification with a combined solution of sodium and potassium hydroxides has been tested by diffractometry and elemental analysis. The results show that the formation of a layer with an increased concentration of alkali metals in the form of the corresponding carbonates and NaOH on the surface of the granules and in the volume of sodium and potassium aluminates provides adsorption of HCl, which are slightly inferior to the fresh adsorbent. The conditions for the removal of halogen-containing substances from technogenic raw materials with the subsequent isolation of useful products have been optimized: (1) crystalline NaCl intended for the preparation of electrolyte for electrode boilers and steam generators; (2) a mixture of chlorides and hydroxochlorides of aluminum tested in the process of coagulation purification of turbid natural and waste waters; (3) pseudoboehmite for the production of an adsorbent-desiccant and the synthesis of magnesium-aluminum spinel using the technology of destruction-epitaxial transformation, and a promising carrier for catalysts for steam reforming of hydrocarbons. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Time- and Temperature-Dependent Luminescence of Manganese Ions in Ceramic Magnesium Aluminum Spinels

Samples of magnesium aluminum spinel ceramics doped with manganese ions were prepared by a high-temperature solid-state reaction method; their potential as red-emitting phosphors was analyzed using a time-resolved luminescence spectroscopy technique, from room temperature to 10 K. It was found that in the red spectral range, the luminescence spectra of manganese ions in the MgAl2O4 spinel showed a narrow band peaking at 651 nm due to the emission of Mn4+ and a broader emission band in the region of 675 ÷ 720 nm; the ratio of intensities for these bands depends on the synthesis conditions. By applying a special multi-step annealing procedure, the MgAl2O4:Mn4+ phosphor containing only tetravalent manganese ions, Mn4+, was synthesized. Broad-band far-red emission observed from MgAl2O4:Mn and Mg1.25Al1.75O3.75F0.25:Mn phosphors, prepared by a conventional method of a solid-state reaction, was interpreted as coming from Mn3+ ions.

Study of the transport properties of composite solid electrolytes LiClO4-MgAl2O4

Magnesium-aluminum spinel MgAl2O4 was synthesized by mechanical treatment of a mixture of hydroxides followed by treatment of the solution at 80 ° C and sintering at 850° C. The obtained nanocrystalline sample with a specific surface area of 100 m2/g were used for the preparation of composite solid electrolytes (1-x) LiClO4-xMgAl2O4. It was shown that conductivity increases with the spinel concentration and goes through a maximum of 1.35·10-2 S/cm at 150 °C for composite 0.3LiClO4-0.7MgAl2O4.

Synthesis of Preceramic Organomagnesium Oxanealumoxane Siloxanes

Organomagnesiumoxane alumoxane siloxane oligomers with different Al:Mg and Al:Si molar ratio have been synthesized through ethylacetoacetate alkoxyhydroxyalumoxane oligomers co-condensation with magnesium acetylacetonate and oligoethoxysiloxanes in organic solvents (alcohol, toluene) at a temperature of 70–100 °С within 3–6 h with the following solvent distillation. The physicochemical properties of the synthesized oligomers were studied. It is shown that with a molar ratio of Al:Mg ≈ 2 and Al:Si ≈ 1, oligomers have fiber-forming properties. The process of thermotransformation of organomagnesiumoxane alumoxane siloxanes into ceramic phases is investigated. It is found that pyrolysis results in the formation of multicomponent ceramics based on magnesium, aluminum, and silicon oxides, in particular, ceramics with a composition close to that of cordierite 2MgO·2Al2O3·5SiO2 (Mg2Al4Si5O18) or a mixed composition: magnesium-aluminum spinel and mullite. Therefore, the synthesized organomagnesiumoxane alumoxane siloxanes are preceramic oligomers and can be used as precursors for the preparation of various components (binders, impregnating compositions, fibers, ceramic powders) of high-purity ceramic composites based on magnesium, aluminum and silicon oxides.

Analysis and Prediction of Corrosion of Refractory Materials by Potassium during Biomass Combustion-Thermodynamic Study

As a kind of renewable resource, biomass has been used more and more widely, but the potassium contained in biomass can cause corrosion of the refractory. For a better understanding of corrosion thermodynamic mechanisms, the five components of common refractory materials (magnesium chrome spinel MgO·Cr2O3, magnesium aluminum spinel MgO·Al2O3, Al2O3, MgO, and Cr2O3) with potassium salts (K2CO3, K2SO4, and KCl) under high-temperature were studied by using the FactSageTM 7.0 software. Thermodynamic calculation results indicate that MgO is the best corrosion resistance of the five components of refractory materials. Based on the obtained results, the corrosion experiments in the laboratory were carried out (muffle furnace or high-temperature tube furnace) for corrosion reaction of KCl and MgO. The chemical compositions of the corroded samples were analyzed by X-ray diffraction (XRD). Under laboratory conditions (600–1200 °C), no corrosion products have been observed in the high-temperature corrosion experiments. The result indicates that to prevent the corrosion processes, refractories should contain as much MgO as possible.