Upgrading of Light Bio-oil from Solvothermolysis Liquefaction of an Oil Palm Empty Fruit Bunch in Glycerol by Catalytic Hydrodeoxygenation Using NiMo/Al ₂O ₃ or CoMo/Al ₂O ₃ Catalysts

Abstract

Hydrodeoxygenation (HDO) of bio-oil derived from liquefaction of a palm empty fruit bunch (EFB) in glycerol was investigated. To enhance the heating value and reduce the oxygen content of upgraded bio-oil, hydrodeoxygenation of light bio-oil over Ni- and Co-based catalysts on an Al ₂O ₃ support was performed in a rotating-bed reactor. Two consecutive steps were conducted to produce bio-oil from EFB including (1) microwave-assisted wet torrefaction of EFB and (2) solvothermolysis liquefaction of treated EFB in a Na ₂CO ₃/glycerol system. The HDO of as-prepared bio-oil was subsequently performed in a unique design reactor possessing a rotating catalyst bed for efficient interaction of a catalyst with bio-oil and facile separation of the catalyst from upgraded bio-oil after the reaction. The reaction was carried out in the presence of each mono- or bimetallic catalyst, namely, Co/Al ₂O ₃, Ni/Al ₂O ₃, NiMo/Al ₂O ₃, and CoMo/Al ₂O ₃, packed in the rotating-mesh host with a rotation speed of 250 rpm and kept at 300 and 350 °C, 2 MPa hydrogen for 1 h. From the results, the qualities of upgraded bio-oil were substantially improved for all catalysts tested in terms of oxygen reduction and increased high heating value (HHV). Particularly, the NiMo/Al ₂O ₃ catalyst exhibited the most promising catalyst, providing favorable bio-oil yield and HHV. Remarkably greater energy ratios and carbon recovery together with high H/O, C/O, and H/C ratios were additionally achieved from the NiMo/Al ₂O ₃ catalyst compared with other catalysts. Cyclopentanone and cyclopentene were the main olefins found in hydrodeoxygenated bio-oil derived from liquefied EFB. It was observed that cyclopentene was first generated and subsequently converted to cyclopentanone under the hydrogenation reaction. These compounds can be further used as a building block in the synthesis of jet-fuel range cycloalkanes.