Biocrude oil production upgrading by catalytic assisted hydrothermal liquefaction of underutilized non-edible seed biomass

Abstract

Thermal and catalytic aqueous hydrothermal liquefaction of Ricinus communis and Jatropha curcas L. seeds, after mechanical defatting, was conducted at 260 °C for 40 min under subcritical water conditions with a biomass-to-water ratio of 1:5 (expressed in wt.). For catalytic aqueous hydrothermal liquefaction, Ni-Pt/Al2O3 was used as heterogeneous catalyst besides a solution of glycerol as in situ hydrogen donor agent. It was noticed that the combination of heterogeneous catalytic aqueous phase glycerol reforming and hydrothermal liquefaction favours and increases the biocrude yield, without external H2 supply. Indeed, a maximum biocrude yield of 59 wt% was registered when Ricinus communis defatted seed was used as starting biomass, which represents an increase of 28 wt% compared to the yield obtained by the non-catalytic HTL process. The biocrudes analysis by GC/MS confirmed that approximately 60% were C16 and C18 hydrocarbon compounds, indicating that the catalyst linked with aqueous glycerol reforming has a marked effect on distribution and upgraded fuel-biocrude stability and quality respect to direct hydrothermal liquefaction (HTL-D). The bimetallic Ni-Pt/Al2O3 conformed catalyst (with a Ni: Pt = 100:1 expressed as an atomic ratio) was effective in the coupled reactions of aqueous reforming of glycerine as well as hydrodeoxygenation and hydrocracking. It upgrades the biocrude with a lower O/C ratio and a higher H/C ratio, which is directly reflected in the HHV of the biocrude that reaches the value of 37 MJ·kg− 1 and can be used as direct fuel. The heterogeneous catalytic process technology, by coupling the glycerol APR and the assisted hydrolysis-depolymerisation of wet-biomass in water subcritical conditions yield to a biomass-derived biocrude with liquid fuel quality.