Kinetic modeling of oil shale upgrading at sub- and supercritical water conditions using Ni- and Fe-based oil-soluble catalysts

Abstract

4- and 7-lump kinetic models for oil shale catalytic upgrading at sub- and supercritical water conditions (300-400 ?C of temperature, 1-48 h of reaction time, and 1:1 water-to-oil mass ratio) were developed from experiments conducted in a 300 mL batch reactor. Four catalysts were used based on two transition metals (Ni and Fe) and two ligands (vegetable and tall oil). The use of catalysts with tall oil diminished the secondary cracking reactions to a greater degree than metal-vegetable oil catalysts, producing higher synthetic oil yield and lower gas yield. Temperatures higher than the critical point of water ()400 ?C) cause the secondary cracking of synthetic oil molecules, reducing its yield. The best results were obtained using Ni-tall oil catalysts since it improves oil shale conversion and suppresses the over-cracking of synthetic oil. The generation of CO2 (mainly from carbonates in oil shale) was the easier reaction among all gases, thus this gas is produced in higher amount. The estimated kinetic parameters of the kinetic models accurately match the experimental data. The statistical and sensitivity analyses indicate that the obtained reaction rate coefficients were properly optimized and correspond to the optimal values.