Thermogravimetric analysis of brown coals and also humic acids as well as their extracted bitumens in the Circumpolar Urals

The purpose of this work is to study the thermal stability of humic acids and bitumens extracted from brown coals of the Circumpolar Urals in the Khanty-Mansi Autonomous Okrug-Ugra. Waxes, bitumens and resins were extracted from brown coals with benzene on Soxhlet apparatuses. Extraction of humic acids was carried out by the Instorf method. Thermal analysis of all humic acid samples was performed at Novosibirsk Institute of Organic Chemistry in the Siberian Branch of the Russian Academy of Sciences on a STA 409 PC Luxx synchronous thermal analyser (Netzsch Company) in an inert atmosphere in a platinum crucible. It was found that thermal stability of humic acid macromolecules obtained from brown coals is characterized by typical thermal effects and quantitatively different value of macromolecule destruction within the ranges from 220 to 400 °C and from 400 to 800 °C.