Hydrodeoxygenation of phenolics in liquid phase over supported MoO3 and carburized analogues

Abstract

Catalytic hydrodeoxygenation (HDO) of mono-aromatic components of increasing structural and chemical complexity, represented by phenol (−OH), anisole (−OCH3), and guaiacol (−OH + −OCH3), was performed in a down-flow trickle-bed reactor. ZrO2 supported Mo oxide with nominal loadings of 7, 15, and 25 wt% Mo were prepared and carburized analogues were synthesized at two thermal severity levels in a mixture of 20% CH4 in H2. HDO performance was compared with ZrO2 and Al2O3 supported CoMo-oxide reference catalysts. Performance was studied in the temperature range 573–648 K and a pressure of 6 MPa at liquid hourly space velocities (LHSVs) of 0.25–4.9 greactant/gcat, h at a H2/phenolic molar ratio of ca. 108. The intermediate Mo loading oxide catalysts showed superior performance. The parent Mo oxides were also more active than their carburized analogues and dominating hydrogenolysis pathways gave similar products and distribution. Carburization caused structural changes by reduction of MoO3 and formation of minor amounts of surface carbon. The weak hydrogenation activity did not change significantly. Reaction pathways were elucidated and ca. 100% selectivity to non-oxygenates in a wide conversion range was obtained from phenol. Anisole HDO was proceeding with ca. 85% selectivity to non-oxygenates. Structural complexity of guaiacol was causing even less efficient deoxygenation with a selectivity to non-oxygenates of only 5–10%. Catalysts were characterized by, N2-BET, CO-chemisorption, ICP-OES, XRD, TPR, XPS, (S)TEM-EDX, combustion-IR, and correlated to kinetic performance.