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The gas phase hydrodeoxygenation (HDO) of guaiacol, as a model compound for pyrolysis oil, was tested on a series of novel hydroprocessing catalysts – transition metal phosphides which included Ni2P/SiO2, Fe2P/SiO2, MoP/SiO2, Co2P/SiO2 and WP/SiO2. The turnover frequency based on active sites titrated by the chemisorption of CO followed the order: Ni2P > Co2P > Fe2P, WP, MoP. The major products from hydrodeoxygenation of guaiacol for the most active phosphides were benzene and phenol, with a small amount of methoxybenzene formed. Kinetic studies revealed the formation of reaction intermediates such as catechol and cresol at short contact times. A commercial catalyst 5% Pd/Al2O3 was more active than the metal phosphides at lower contact time but produced only catechol. A commercial CoMoS/Al2O3 deactivated quickly and showed little activity for the HDO of guaiacol at these conditions. Thus, transition metal phosphides are promising materials for catalytic HDO of biofuels. |
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