Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol

Abstract

This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (MoOh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of CoOh and the catalytic performance. At low CoOh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS2 slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available CoOh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio.

Cobalt-Molybdenum Oxides for Effective Coupling of Ethane Activation and Carbon Dioxide Reduction Catalysis

“…This change is much larger than that observed in the bimetallic 8CoO–13.5MoO x catalyst (Figure ), where only 15.8% of Co atoms are reduced. This result confirms that, without Mo, Co species are more reducible, that is, Co 3 O 4 or CoO species (in the monometallic 10CoO catalyst) are more likely to be reduced to metallic Co particles than the Co embedded in the CoMoO 4 structures, as also reported by others. − As established, metallic Co, , together with other late transition metals (Ni, , Pt, ,, Pd, Ru, − Rh , ), is extremely reactive for alkane reforming reactions rather than the oxidative dehydrogenation reaction. The reduced 10CoO sample displayed much higher turnovers, >20 times higher than those of CoO–MoO x series, but these C 2 H 6 turnovers led exclusively to reforming products (CO and H 2 ) without producing any ethylene.…”

GuaiacolHDOon La‐modified Pt/Al2O3: Influence of rare‐earth loading

“…Others [ 61 ] have also found similar trends where CAT was produced by demethylation (OCH 3 bond rupture) during GUA HDO over alumina. In full agreement, Tavizón‐Pozos et al [ 62 ] reported production of so‐called ‘oxygenated intermediaries’, although no specific species were disclosed in that case. Interestingly, cyclohexene was also identified by those authors, with that being attributed to dehydration (from cyclohexanol [ 63,64 ] or cyclohexanone [ 64 ] ) on Brønsted acid sites provided by the equimolar alumina–titania carrier used.…”

Insight into the Microstructure and Deactivation Effects on Commercial NiMo/γ-Al2O3 Catalyst through Aberration-Corrected Scanning Transmission Electron Microscopy

“…We speculate that the promoter Ni exists as Ni x S y crystals after segregation from the active phase. For hydrotreating catalysts, the X-ray photoelectron spectroscopy (XPS) technique has been among the tools most often used to obtain chemical states information on the promoter atoms in hydrotreating catalysts [32][33][34][35]. Therefore, XPS was performed for the catalysts in order to verify our speculation.…”