Hydrodeoxygenation of solvolysed lignocellulosic biomass by unsupported MoS2, MoO2, Mo2C and WS2 catalysts

• Synthesis of nanostructured urchin-like and inorganic fullerene-like MoS2 materials.
• Catalytic upgrade of real wood-derived oil, obtained by low-temperature solvolysis.
• Influence of MoS2 morphology on kinetics of deoxygenation and cracking reactions.
• Evaluation of sulphide replacement with carbide or oxide and Mo replacement with W.
• Proposal of reaction mechanism, lumped kinetic model and mass-transfer limitations.

Hydrotreatment of liquefied lignocellulosic biomass was investigated at 300 °C under the total pressure of 8 MPa in a slurry reactor over unsupported molybdenum (disulphide, dioxide and carbide) and tungsten (disulphide) catalysts. Novel nanostructured urchin-like MoS2 and inorganic-fullerene MoS2 interconnected with carbon materials were synthetized and tested, while the influence of metal variation and the sulphide replacement with carbide or oxide was also investigated by using commercially available MoS2, Mo2C, MoO2 and WS2. Catalysts were structurally characterised by field-emission scanning (SEM) and high-resolution transmission (HRTEM) electron microscopies, energy-dispersive X-ray (EDX) and Raman spectroscopies, as well as X-ray diffraction (XRD). The hydrodeoxygenation (HDO), decarbonylation, decarboxylation and hydrocracking kinetics of depolymerised cellulose, hemicellulose and lignin were determined according to the transformation of their functional groups in liquid phase, and the corresponding gaseous products by an innovative lumped kinetic model based on Fourier transform infrared spectroscopy. Unsupported MoS2 catalysts showed high hydrogenolysis selectivity, the morphology clearly affecting its rate. A high HDO activity reflected in the mass balance and phase distribution of the upgraded liquid product by reducing tar residue and increasing the yield of oil phase with the gross calorific value of 38 MJ kg−1 and oxygen content below 8.5 wt%.

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