Effects of Hydrothermal Treatment on the Properties of Jordanian Oil Shale

Oil shale is an important unconventional energy resource,
and enhancing
its thermal conversion processes can significantly improve the oil
yield and quality. However, the complex structure and high sulfur
content of marine-origin oil shales, such as Jordanian El-Lajjun oil
shale, pose challenges to efficient conversion. This study aims to
investigate the influence of hydrothermal treatment (HT) on the structure
and thermal behavior of El-Lajjun oil shale to optimize oil production
and improve product quality. HT was conducted at different temperatures
(150, 200, and 250 °C), and the resulting structural changes
were analyzed by using elemental analysis, Fourier-transform infrared
spectroscopy (FTIR), and thermogravimetric analysis (TGA). Subsequently,
pyrolysis experiments at 520 °C using an alumina bed reactor
were performed, and the oils generated from raw and HT samples were
characterized by FTIR, 1H NMR, and gas chromatography–mass
spectrometry. The results showed that HT led to an increase in the
carbon content and a reduction in the sulfur content. TGA results
indicated a greater weight loss during the combustion of volatile
matter for treated samples, highlighting notable changes in chemical
structure. Pyrolysis of HT samples produced higher oil yields with
improved quality, demonstrated by increased hydrocarbon content, reduced
heteroatom and oxygenated compounds (such as esters and phenols),
and an enhanced aromatic yield. Notably, HT at 150 °C was particularly
effective in maximizing the oil yield and improving quality. These
findings suggest that carefully controlled HT conditions can significantly
benefit the thermal conversion of marine high-sulfur oil shales.