Aqueous Phase Reforming (APR) was conducted at a temperature of 225 °C, a pressure of 450 psi, and with two catalysts: 5 wt% platinum and 5 wt% ruthenium supported on active carbon. Single- and multi-component surrogate feedstocks consisting of acetic acid, acetone, ethanol, glycerol, succinic acid, and N-methylacetamide were tested to compare the two catalysts. Among the catalysts, the ruthenium catalyst consistently outperformed the platinum catalyst, achieving hydrogen yields of 77-100% compared to 44-54% with platinum for multi-component feedstocks. The wastewater resulting from the Hydrothermal Liquefaction (HTL) of Municipal Sewage Sludge (MSS) was tested at 225 and 250 °C, and at 450 and 650 psi. Results demonstrated that while hydrogen can be produced from MSS-HTL wastewater using a ruthenium catalyst supported on carbon, catalyst deactivation was severe. Future work is suggested to investigate methods to prevent catalyst deactivation due to carbonaceous solid deposition.
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/Al2O3 catalyst. The results showed that catalyst introduction reduced organic yield, promoting the non-condensable gas production, and its enrichment of methane and light C2-C3 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% H2 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% H2 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.
