Saint Petersburg Mining University, Saint Petersburg, Russia:

E. A. Spetsov, Section Leader at the Research Centre for the Problems of Processing Mineral and Man-Made Resources, Candidateof Technical Sciences, e-mail: spessov@yandex.by
D. I. Artyushevskiy, Engineer at the Research Centre for the Problems of Processing Mineral and Man-Made Resources, e-mail: dmitriylyazga@gmail.com
R. R. Konoplin, Research Fellow at the Research Centre for the Problems of Processing Mineral and Man-Made Resources, e-mail: rostislav.konoplin1@gmail.com
V. M. Sizyakov, Research Supervisor at the Research Centre for the Problems of Processing Mineral and Man-Made Resources, Doctor of Technical Sciences, Professor, e-mail: sizyakov_vm@pers.spmi.ru

This paper describes the results of thermal analysis of aluminium hydroxides that are most commonly used in the production of alumina and catalyst supports. The aluminium hydroxides contained an amorphous phase, boehmite, bayerite, pseudoboehmite, and gibbsite. Analysis of the temperature ranges of phase transformations was based on thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The proposed optimized graphical method for thermogram processing expands the range of parameters determined in aluminum hydroxide samples. The results of the conducted analytical study provide a more accurate ground for analyzing not only the crystalline phases but also the amorphous phase in the studied samples, as well as the excess structural water, ammonium nitrate and humidity. Thermal decomposition of aluminum hydroxide powder into oxides followed by reconstruction of the latter in an aqueous solution of (NH₄)₂CO₃ leads to their selective reaction with the amorphous phase Al₂O₃ and the formation of NH₄Al(OH)2CO₃. Such sample preparation technique led to better accuracy when determining the amorphous phase in the samples by means of thermal analysis. Calibration thermograms were obtained by introducing known amounts of ammonium nitrate into the concentrated phase of microcrystalline boehmite through wet impregnation. Having processed them, the authors were able to propose a method for calculating the concentration of burning impurities in aluminium hydroxides. This research was carried out in the laboratory facilities provided by SPS Eurochim Ltd. from Saint Petersburg, Russia.

The authors would like to thank professor Arkady Dykman, CEO of SPS Eurochim Ltd., Saint Petersburg, Russia, for providing laboratory equipment and materials for sample preparation.

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