Atmospheric catalytic fast hydropyrolysis of hazelnut shell over Mo/Al2O3: effects of temperature, hydrogen partial pressure and catalyst configuration on deoxygenation, carbon recovery and energy performance

This work investigates how hydrogen partial pressure and catalyst configuration affect product distribution, oil deoxygenation, carbon recovery, and energy balance in atmospheric catalytic fast hydropyrolysis (CFHP) of lignocellulosic biomass. The effects of hydrogen partial pressure (0–70 vol%), temperature (400–500 °C), and in-situ/ex-situ configurations were investigated in a lab-scale dual-stage fluidized-bed reactor, employing an industrial Mo/Al 2 O 3 catalyst. The results showed that catalyst introduction reduced organic yield, promoting the non-condensable gas production, and its enrichment of methane and light C 2 -C 3 hydrocarbons. Increasing hydrogen partial pressure improved the elemental composition of the organic phase and increased its degree of deoxygenation, achieving up to 37.5% of degree of deoxygenation at 70 vol% H 2 partial pressure, keeping the carbon recovery relative to non-catalytic case up to 76.7%. GC-MS/FID analysis indicated that catalytic upgrading was associated with lower methoxyphenol abundance, higher phenolic compounds, and increased aromatic species, including polycyclic aromatics. Mass balance showed reduced carbon partitioning to the aqueous fraction and increased carbon recovery in char, coke, non-condensable gases, and the organic oil fraction. Within the adopted energy-balance boundaries, the limited net hydrogen consumption contributed to higher calculated process efficiency in the catalytic cases. Energy efficiency of up to 83.4% was obtained in the case of CFHP in an ex-situ approach with 40 vol% H 2 partial pressure. These results show that atmospheric CFHP can partially upgrade biomass-derived vapors at relatively low net hydrogen consumption and may offer a lower-complexity route for vapor deoxygenation, warranting further catalyst-stability, scale-up, and techno-economic assessment.