ALUMINUM HYDROXYNITRATES THERMOLYSIS

• Published in: IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA Vol. 60; no. 8; p. 31
• Main Authors: Kosenko, Nadezhda F., Filatova, Natalya V., Lipina, Evgeniya A.
• Format: Journal Article
• Language: English
• Published: 29.08.2017
• ISSN: 0579-2991; 2500-3070
• DOI: 10.6060/tcct.2017608.5599

The thermolysis of various aluminum hydroxynitrates obtained by fresh precipitated Al hydroxide dissolution in a stoichiometric quantity of nitric acid has been studied. Under heating their multistage decomposition occurs including a gradual removal of chemically bonded water and denitration. According to thermal analysis data the composition of AlOH(NO3)2·mH2O, Al(OH)2NO3·nH2O and Al2(OH)5NO3·kH2O decomposition products at temperatures of 40-800 °С has been determined. It was ascertained that crystalline hydrate water segrerates under 157 °С (double stage). In the course of the primary dehydration the most loosely coupled crystal water (0.5-0.8 water molecules) escapes. Then the secondary dehydration – the remaining crystal water removal – takes place. This process becomes easier with increasing hydroxygroups quantity; it is confirmed by a proper temperature interval shift to lower temperatures. At 190-241 °С nitrate turns into nitrite (at approximately the same temperature for all studied compounds). Afterwards (249-376 °С) the denitration and chemically bonded water removal from salts anions take place. At that boehmite AlOOH is formed. The latter gives alumina transitional forms. In the time of Al(OH)2NO3·nH2O and Al2(OH)5NO3·kH2O thermolysis the partial removal of chemically bonded water overlaps on the denitration; so thermogravimetric curves have the most complex form. As a result all hydroxynitrates in contrast with aluminum nitrate are transformed into boehmite AlOOH that is confirmed by X-ray phase analysis. In addition, the composition of thermal decomposition products is confirmed by elemental analysis data.Forcitation:Kosenko N.F., Filatova N.V., Lipina E.A. Aluminum hydroxynitrates thermolysis. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 31-36.