New approaches to the study of maturation changes of organic matter in humic coals

Abstract

У овој дисертацији су проучаване матурационе промене органске супстанце хумусних угљева, почев од касне дијагенезе до полуантрацитског степена карбонификације, што одговара опсегу рефлексије витринита (Rr)= 0.4-1.8 %. Сазревање органске супстанце је симулирано пиролизом узорака мрког (Rr = 0.42 %) и каменог угља (Rr = 0.56 %) из Боговинског угљоносног басена. Пиролиза је изведена у затвореном систему, на температурама од 250 и 400 °C ...This thesis investigates the maturation changes of organic matter in humic coals, starting from the late diagenesis up to the semianthracite stage of carbonification, which corresponds to the vitrinite reflectance (Rr) range of 0.4-1.8 %. Organic matter maturation was simulated by the closed-system pyrolysis at 250 and 400 °C, conducted on a subbituminous (Rr = 0.42 %) and a bituminous coal (Rr = 0.56 %) from the Bogovina coal basin. The changes in kerogen and bitumen were analyzed. Vitrinite contents continually increase within 0.4-1.8 % Rr range. Sporinite, resinite, suberinite, and alginite are the most reactive liptinite macerals. The most important liquid products of their thermolysis are n-alkanes, n-alkylbenzenes, n-alkylthiophenes, and n-alkylbenzo[b]thiophenes. Liptinites substantially degrade at 400 °C (Rr = 1.8 %), producing primarily n-alkanes. Inertinite contents increase up to Rr = 0.8 %, followed by a slight decrease in Rr = 0.8-1.8 % maturation range. The distributions of various compounds in pyrolysis oil indicate a substantial increase in thermal maturity, particularly at Rr = 1.8 %. The oils obtained at 400 °C show the petroleum-type distribution of hydrocarbons. The applicability of maturity parameters was determined in 0.4-1.8 % Rr range. A new maturity parameter, having a good sensitivity in this wide maturity range, is defined based on the distribution of methylfluorenes. Coal asphaltenes were investigated by pyrolysis, in the same manner as humic coals, and by mild oxidation methods. The pyrolysis at 400 °C and the mild oxidation of asphaltenes increase the maturity level. Hence, the oil obtained at 250 °C most closely resembles bitumen, particularly in low rank coals. Coal asphaltenes have a greater hydrocarbon generation potential than coal kerogen. A new series of biomarkers was discovered (C33-C35 31-methylbenzohopanes) and their application in correlation studies was defined