Characterization of Jordanian oil shale and variation in oil properties with pyrolysis temperature

Abstract

Marine oil shale from the Sultani mine was characterized (ultimate and proximate analysis, 13C NMR, differential thermogravimetry (DTG)). The 13C NMR indicated that the shale is highly aliphatic, and the concentration of carbonyl carbon is small. DTG indicated a total weight loss of 21 wt% to 550 °C. The shale was pyrolysed to different final temperatures in the range 360–540 °C under N2 and the shale oils produced characterized by utilization parameters (API, heating value, boiling point distribution) and by chemical properties (1H-NMR and gas chromatography-mass spectrometry GC–MS) as a function of final pyrolysis temperature. Previous studies have only investigated the utilization properties of marine-shale oil at one temperature. The average oil yield increased with pyrolysis temperature to a maximum at 520 °C, and then fell. The oil density was higher at 440–520 °C than at 360–400 °C (0.99–1.00, 0.96−0.97 g/cm3 respectively). Unexpectedly, oil heating value (39.7–40.0 MJ/kg in 360–540 °C) and sulfur content (11.25 wt% in 360–520 °C) were independent of pyrolysis temperature. Oil distillation indicated that up to 90 vol% was in the diesel fraction.1H-NMR implied that the oil produced at all temperatures was highly aliphatic. GC/MS for the oil indicated the presence of long chain hydrocarbons (C11-C32), both normal and branched, some substituted benzenes, and high concentrations of sulfur compounds, mainly substituted thiophenes with same benzothiophenes. The average molecular weight of the sulfur compounds and proportion of heavier oil were higher at 520 °C than at 460 °C, so that the increased yield of oil at higher temperatures would have to be balanced against the lower quality of the crude shale oil produced. The results emphasized the importance of studying oil properties as a function of pyrolysis temperature, as differences which could be important in practice were noted.