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

Abstract

Catalytic hydrodeoxygenation (HDO) of monoaromatic 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

Hydrodeoxygenation of Lignin-Derived Phenols: From Fundamental Studies towards Industrial Applications

“…Thus, dehydroxylation of the phenyl ring is difficult [37,39,48,61]. Reactivity of anisole higher than guaiacol reported in [39] similarly to the work of Prasomsri et al [36], can be explained by a higher bond dissociation energy required for the aromatic hydroxyl compared to methoxyl (Table 3). For o-cresol the preferred route is demethoxylation followed by ring hydrogenation [37].…”

“…The reasons for this difficulty to deoxygenate guaiacol and other model molecules are discussed in Section 3.3. MoO3/ZrO2, 60 bar, benzene [39], 3. MoO3/ZrO2, 60 bar, benzene [39], 4.…”

“…MoO3/ZrO2, 60 bar, benzene [39], 3. MoO3/ZrO2, 60 bar, benzene [39], 4. ReOx/CNFox, 50 bar, cyclohexane [37], 5.…”

“…MoO3, 1 bar, benzene [36], 8. MoO3/ZrO2, 60 bar, benzene [39], 9. Pt-Sn/CNF/Inconel, 1 bar, benzene [48], 10.…”

“…From HDO of different model compounds, comprising guaiacol, anisole, phenol and o-cresol with a single reactant over the same catalyst it is possible to compare their relative reactivity, which is of high interest for industrial applications (Table 2) [36,37,39,48]. Results over ReOx/CNF catalyst at elevated temperature, 300 • C and pressure of 50 bar showed that conversion of four different model molecules decreased in the following order: guaiacol = anisole > phenol > cresol ( Figure 5) [37].…”