Hydrothermal liquefaction (HTL) followed by catalytic hydrotreating of the
produced biocrude is increasingly gaining ground as an effective technology for
the conversion of biomass into liquid biofuels. A strong advantage of HTL
resides in its great flexibility towards the feedstock, since it is able to
treat a large number of different organic substrates, ranging from dry to wet
residual biomass. Nevertheless, the characteristics of biocrudes from different
typologies of organic materials result in different challenges to be met during
the hydrotreating step, leading to differences in heteroatoms removal and in
the typology and composition of the targeted products. In this work, biocrudes
were catalytically hydrotreated with a commercial NiMo/Al2O3 catalyst at
different temperatures and pressures. Sewage sludge biocrude was found to be
very promising for the production of straight-chain hydrocarbons in the diesel
range, with considerable heteroatoms removal even at mild hydrotreating
conditions. Similar results were shown by algal biocrude, although complete
denitrogenation is challenging. Upgraded biocrudes from lignocellulosic
feedstock (miscanthus) showed high yields in the gasoline range, with a
remarkable content of aromatics. Operating at a higher H2 pressure was found to
be crucial to prevent coking and decarboxylation reactions.Comment: Accepted manuscript for publication in Renewable Energ
