Quantitative analysis of the aqueous fraction from the Fe-assisted hydrothermal liquefaction of oil palm empty fruit bunches

Hydrothermal liquefaction is a promising candidate method for the conversion of biomass resources. To improve economic efficiency, the development of processes that utilize the water-soluble (WS) hydrothermal-liquefaction fraction is critical; consequently, a fundamental method for the analysis of the WS fraction is required. In this study, the quantitative analysis of the WS fraction obtained from the Fe-assisted hydrothermal liquefaction of oil palm empty fruit bunches was comprehensively investigated by combining various separation and analysis methods The volatile components of the WS fraction were analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID), and they were quantified using the relative response factors estimated by the effective carbon number method. Heavy components not detectable by GC were isolated by freeze-drying, and their elemental compositions, functional groups, and molecular-weight distributions were analyzed. The results reveal that the addition of Fe during hydrothermal liquefaction alters the types of compounds present in the WS fraction by a large extent, and increases the proportion of volatile compounds. The reactivity of the WS fraction in the zeolite-catalyzed cracking reaction was also investigated, which revealed that the volatile components of the WS fraction are efficiently converted into olefins.