Impact of nitrogenous alkaline agent on continuous HTL of lignocellulosic biomass and biocrude upgrading

Continuous hydrothermal liquefaction (CHTL) of lignocellulosic biomass with subsequent hydrotreating is carried out to study the effect of NH3 versus NaOH as alkaline HTL catalyst. Product analysis include Py-GCxGC-MS, simulated distillation and fractional distillation. Ammonia enhances biocrude quality slightly in terms of H/C ratio, density and HHV, but a significant coke formation of 11 wt.% is observed. Furthermore, ammonia pollutes the biocrude with 2.7 wt.% nitrogen, which is observed to inhibit hydrotreating conversion. In comparison, CHTL with NaOH is associated with a 43 wt.% yield of a hydrotreatable biocrude, stable TOC levels during aqueous phase recirculation and mass, carbon and energy balance closure. Hydrotreating eliminates the TAN, reduces oxygen to 2-3 wt.% and produces a promising fuel bio-blendstock with ultra-low sulphur and a diesel fraction equal to 43%.