Fast pyrolysis is one of the most promising processes for the conversion of lignocellulosic biomass into biofuels and chemicals because its relative low cost and simplicity of operation. However, the liquid fraction obtained by this procedure (known as bio-oil) contains a significant amount of oxygen and water, which hinders its direct use in combustion engines due to its low heating value, high viscosity and corrosiveness.
Catalytic hydrodeoxygenation (HDO) is one of the most efficient alternatives to reduce the oxygen content of pyrolysis bio-oils. Through this process, oxygen is removed in the form of water under high hydrogen pressures, moderate temperatures and using a heterogeneous catalyst. The first catalysts studied were those traditionally used in oil crude hydrotreating processes, based on metal sulphides supported over γ-Al2O3. However, these catalysts exhibit low stability, being rapidly deactivated during HDO. Alternatively, transition metal phosphides, especially nickel phosphide, have attracted a great deal of attention as suitable HDO catalysts because of their effectiveness and stability in analogue hydrotreating processes (HDS and HDN) of petroleum feedstocks.
In this research1, the Thermochemical Processes Unit of IMDEA Energy, in collaboration with the group of Professor J. Cejka (Charles University, Prague), has recently developed a series of HDO bifunctional catalysts based on nickel phosphide supported on two-dimensional zeolites (2D zeolites). These novel supports are made up of ultrathin crystals (near single-unit-cell thickness), whose external surface can achieve more than 50 % of the total area of the material, leading to a better dispersion of the metallic phase, as well as an enhanced accessibility of active sites, which favors the processing of the bulky molecules typically present in pyrolysis bio-oils.
 S. Gutiérrez-Rubio, A. Berenguer, J. Přech, M. Opanasenko, C. Ochoa-Hernández, Patricia Pizarro, J. Čejka, D. P. Serrano, J. M. Coronado, I. Moreno “Guaiacol Hydrodeoxygenation over Ni2P supported on 2D-zeolites” Catalysis Today 345 (2020) 48-58. https://doi.org/10.1016/j.cattod.2019.11.015
More information: Inés Moreno, Associate Postdoctoral Researcher, Thermochemical Processes Unit firstname.lastname@example.org