Quantifying the dominant factors in Cu catalyst deactivation during glycerol hydrogenolysis

Long term stability of a commercial Cu-based glycerol hydrogenolysis catalyst has been studied in an isothermal trickle-bed reactor at 473–503 K in the presence of impurities, such as S, Cl and glycerides. While glycerides have the least effect on the catalytic activity, the increase in the extent of deactivation with temperature as a consequence of thiophene indicates a kinetic rather than a thermodynamic adsorption effect. The threshold driven, ‘sudden’ manner in which deactivation manifests itself in case of Cl is indicative of sintering. A deactivation model accounting for the activity loss with changing concentration of impurities and temperature, was constructed

Effect of composition and preparation of supported MoO3 catalysts for anisole hydrodeoxygenation

A series of zirconia supported molybdenum oxide materials with Mo loadings of 7, 12, and 19 wt% were synthesized using incipient wetness impregnation. The as synthesized oxide materials were further modified under H-2/CH4 (80/20%, v/v) at 550 and 700 degrees C. The obtained catalysts were characterized by ICP-OES, XRD, Raman spectroscopy, H-2-TPR, NH3-TPD, XPS, (S) TEM-EDX, BET, CHNS and CO chemisorption. While the Mo species, i.e., MoO3 and Zr(MoO4)(2), in the 7 wt% Mo loaded material were found to be of rather amorphous nature, their crystallinity increased significantly with Mo loading. The anisole hydrodeoxygenation performance of the catalysts was evaluated at gas phase conditions in a fixed bed tubular reactor in plug flow regime. A predominant selectivity towards hydrodeoxygenation and methyl transfer reactions rather than to hydrogenation was observed, irrespective of the Mo loading and further treatment, yet interesting differences in activity were observed. The highest anisole conversion was obtained on the catalyst(s) with 12% Mo loading, while the 7% Mo loaded one(s) exhibited the highest turnover frequency (TOFanisole) of 0.15 s(-1). CO chemisorption, XPS analysis and kinetic measurements indicate that treatment under H-2/CH4 slightly reduced the initial anisole conversion, yet enhanced catalyst stability as well as TOF, probably due to the increased amounts of Mo5+ species. The importance of appropriate tuning of the reduction and/or preparation procedures has been addressed to improve the catalysts' performance during anisole HDO

A comprehensive kinetic model for Cu catalyzed liquid phase glycerol hydrogenolysis

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

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