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A two-step bio-oil upgrading study using carbon supported molybdenum carbide catalysts Liu, Shida

Abstract

A two-step bio-oil upgrading process has been investigated using carbon supported molybdenum carbide catalysts. The waste materials, petcoke (PC) and biochar (BC) were activated to yield the Mo₂C/APC and Mo₂C/ABC catalysts (APC – activated petcoke and ABC – activated biochar). These catalysts presented very high (approximately 85%) direct deoxygenation (DDO) selectivity in the hydrodeoxygenation (HDO) reaction. Furthermore, the Mo₂C/APC catalysts with low Mo loading (1 and 2 wt %) were acid washed in H₂SO₄ and both the Mo₂C/APC catalysts and the acid treated Mo₂C/APC catalysts were active for the esterification of acetic acid and 1-butanol. The hydrodeoxygenation (HDO) of 2-methoxyphenol over Pd, Ru and Mo₂C catalysts supported on activated charcoal (AC) was compared. The overall 2-methoxyphenol consumption rate decreased in the order Pd > Ru > Mo₂C due to Mo₂C’s lower hydrogenation activity. Mo₂C was the most efficient in terms of O-removal with minimal H₂ consumption. To enhance the hydrogenation activity of the Mo₂C catalysts, promotion of a 10 % Mo₂C/carbon catalyst with 1%Cu, 1%Ni and 1%Pd was assessed for the HDO of dibenzofuran (DBF). The addition of Ni and Pd decreased the temperature required for the removal of the oxygen layer from the Mo₂C that is formed during catalyst passivation. This enhanced ability of the promoted catalyst to hydrogenate surface oxide species suggests that the same catalyst could improve the stability of the catalyst during HDO. Finally, the catalysts were assessed in a two-step bio-oil upgrading process that combined esterification and hydrodeoxygenation to improve the bio-oil fuel quality. In the first step, the Mo₂C catalysts were shown to have sufficient acidity so as to catalyse esterification reactions at 180 °C and 10.3 MPa that stabilized the bio-oil. In the 2nd step of the upgrading process, the best Mo₂C catalyst 1Ni-10Mo₂C/ABC achieved 69% HDO with an overall carbon yield of 67% when operated at 350 °C and 15.0 MPa. The Ni-Mo₂C catalysts are proven to be promising catalysts for the proposed two-step bio-oil upgrading.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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