Optimization study of sub/supercritical water liquefication of lignite: Fast liquefaction for high bio-oil yield

Hydrocarbon Fuels from Sequential Hydrothermal Liquefaction (HTL) of Lignite and Catalytic Upgrading of Crude Oil

“…CO 2 was the majority product in the gas phase, corresponding to 92.6 wt % of all of the produced gases. The high CO 2 selectivity in the gas products obtained from lignite HTL had already been reported previously, , indicating that decarboxylation is one of the primary processes responsible for oxygen removal during the reaction. Indeed, CO only represented 1.4 wt % of the gases, suggesting that decarbonylation is significantly less favored.…”

“…Thus, a high concentration of ash found in lignite (25.94 wt %) could also be responsible for the low crude oil yield (12.3 wt %). Indeed, Liu et al used lignite with 7.14 wt % of ash. It should be mentioned that Oner et al demonstrated that ash positively enhances the crude oil product in lignite liquefaction under organic solvents, like tetraline, and under H 2 pressure .…”

“…Liu et al 15 studied the optimal conditions for maximizing crude oil yield from lignite HTL and found that short residence times, i.e., ∼5 min, and high temperatures, i.e., ∼400 °C, are necessary. In this study, 15 the authors found a maximum crude yield of 34 wt %. Hence, the high residence time (30 min) and low temperature (360 °C) presently used can explain the low crude oil yield.…”

“…While the primary target product for liquid fuel production is crude oil, only 12.3 wt %daf of lignite was transformed into this product with char (48.8 wt %daf), gas (23 wt % daf), and aqueous phase organics (15.9 wt %daf) representing the main fractions. Liu et al 15 studied the optimal conditions for maximizing crude oil yield from lignite HTL and found that short residence times, i.e., ∼5 min, and high temperatures, i.e., ∼400 °C, are necessary. In this study, 15 the authors found a maximum crude yield of 34 wt %.…”