However, once supercritical conditions for liquefaction are achieved, reaction pressure impart little or negligible influence on
the yield of liquid oil. On the other hand, when the reaction pressure is further increased in supercritical conditions, cage effect will be caused, which ends up in low fragmentations [25]. This abovementioned viewpoint may explain the phenomenon that the bio-oil yield was slightly reduced as the R2 was further increased from 25% to 30%.