Hydrothermal Liquefaction of Tannery Sludge: Preliminary Results of Bio-crude in-situ Upgrading with Fe, Zn, MgCl2

This work investigates the influence of different active phases on the hydrothermal liquefaction (HTL) of a tannery sludge (TS) performed in a 500 mL batch autoclave reactor at 350 °C for 10 min. The quality and energy-related properties of the bio-crude were evaluated through elemental analysis and higher heating value (HHV) determination. Results show that even if the bio-crude mass yield of the products does not vary significantly with the use of Fe, Zn and MgCl2, a variation of both the HTL products distribution and bio-crude composition are observed. In particular, Fe promotes the aqueous phase formation, while Zn limits organic transfer and MgCl2 promotes ash dissolution. Only Zn and MgCl2 improve the bio-crude quality in terms of C, N and S content.