Hydrothermal Carbonization of Oil Palm Pressed Fiber: Effect of Reaction Parameters on Product Characteristics

Abstract

This work focused on the hydrothermal carbonization (HTC) of oil palm pressed fiber for the production of valuable products, over the reaction temperature (140 to 200 °C), time (1 to 4 h), and biomass to water content (BTW) (1:5 to 1:15). Reaction temperature was a vital key parameter on fuel properties of hydrochar. The combustibility of hydrochar reflected by fuel ratio increased from 0.42 at 140 °C to 0.54 at 200 °C. O/C and H/C atomic ratio decreased from 0.56 and 1.54 to 0.37 and 1.28, respectively, which corresponded to an increase in the estimated HHV from 21.0 to 24.6 MJ/kg. Hydrochar yield decreased from 78.4 to 61.7%. These phenomena were associated with hydrolysis, dehydration, decarboxylation, aromatization, and recondensation reactions. The reaction time and BTW affected slightly the yield and fuel properties of hydrochar. The valuable dissolved organic chemical species in the obtained liquid fraction were furfuryl alcohol, furfural, hydroxymethylfurfural, acetic acid, propionic acid, lactic acid, and formic acid with the maximum yields of 6.95, 2.05, 0.64, 6.91, 4.75, 4.11 and 2.64 wt.% dry raw material, respectively.