Evaluation of the Products from Hydrothermal Liquefaction of Palm Empty Fruit Bunch

Abstract

Hydrothermal liquefaction (HTL) is a thermal depolymerization of biomass to liquid components in the presence of water at moderate to high temperatures (200–400 °C) and pressures (10–25 MPa). At the threshold of the critical point, the characteristics of water change dramatically, and water behaves like an excellent reacting medium. With the continued expansion of palm oil industries in Malaysia, the abundance of empty fruit bunch (EFB), the largest organic solid waste from palm oil mills, has grown significantly. In the current study, the effects of temperature and dosage of H₂O₂ on hydrothermal liquefaction of EFB were conducted. The maximum yield of bio-oil attained was 25.4 wt% at 275 °C. The presence of an oxidizing agent (H₂O₂) near critical conditions makes the process more effective in the oxidation of lignin. The major components of biocrude oil were cyclopentenone (enone) derivatives and phenol derivatives. The amount of phenol in biocrude oil increased with temperature, reaching a maximum yield of 8.9 wt% when 3 mL of H₂O₂ was added for HTL at 275 °C. The fixed carbon and thermal stability of hydrochar increased when H₂O₂ was introduced during the HTL process. The yield and quality of the products were controlled by the temperature of the HTL process. Meanwhile, the depolymerization of lignin with an oxidant provided phenolic-rich biocrude oil.