Preparation, characterization, and catalytic activity of CoMo/γ-Al2O3 catalysts prepared by equilibrium deposition filtration and conventional impregnation techniques

Papadopoulou, Christina; Vakros, John; Matralis, H.; Voyiatzis, George A.; Kordulis, Christos

doi:10.1016/j.jcis.2003.11.041

Cited by 51 publications

(20 citation statements)

References 54 publications

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“…Additionally, bands between 905 and 918 cm −1 for the C5 and CoMoind catalysts were attributed to the presence of molybdate CoMoO 4 species, either isolated or polymerized, involving a strong interaction with the support. As reported by some authors [33,42,45,46], the formation of aluminum molybdate species occurs at high Mo loadings. It has been published also that some amount of Mo reacts with Co during calcination.…”

Section: Raman Analysissupporting

confidence: 60%

“…This species has low electronegativity and, therefore, it can interact more easily with more electronegative elements [31], such as molybdenum species, rather than with cobalt species. This is relevant for the preparation method, considering that the latter has a tendency to form cobalt aluminate with the support when using impregnation methods [3,32,33]. Figure 4 displays the 27 Al MAS-NMR spectra for the calcined catalysts.…”

Section: Nitrogen Physisorptionmentioning

confidence: 99%

“…It is likely that these metal loadings did not reach the MoOx monolayer formation [44,47]. Moreover, the bands appearing between 200 and 400 cm −1 were attributed to Mo monomeric species [33].…”

Section: Raman Analysismentioning

confidence: 99%

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CoMo/γ-Al2O3 Catalysts Prepared by Reverse Microemulsion: Synthesis and Characterization

Munguía-Guillén¹,

Reyes-Heredia²,

Picquart³

et al. 2018

Microemulsion - A Chemical Nanoreactor [Working Title]

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A series of CoMo/γ-Al 2 O 3 catalysts was synthesized by a reverse microemulsion method using 1-butanol as organic agent and cetyltrimethylammonium bromide as surfactant. The aqueous phase was used to form the solution of three corresponding Co, Mo and Al precursor salts. The materials were prepared at different solution concentrations in order to obtain different metal contents. All samples were characterized by X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance and nitrogen physisorption. A chemical species distribution study was performed to establish conditions of preparation and the preponderant species present in solution as a function of pH. The materials obtained present high surface areas which decrease as the metal content (Co + Mo) increases. All samples with the exception of that with the highest metal content were amorphous as shown by X-ray diffraction. By Raman spectroscopy, MoO -Mo and MoO 2t species were observed in all calcined samples. MoO Co , Al-O-Mo, monomers and heteropolymolybdates were observed for the lower metal content samples, and the formation of CoMoO 4 and aluminum molybdate species for the higher metal contents. These results suggest that the materials with lower metal loading have species that are easily sulfidable and provide high activity in hydrodesulfurization reactions. A model for the interaction of the species in the aqueous phase of the micelle is presented.

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Section: Raman Analysissupporting

confidence: 60%

Section: Nitrogen Physisorptionmentioning

confidence: 99%

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CoMo/γ-Al2O3 Catalysts Prepared by Reverse Microemulsion: Synthesis and Characterization

Munguía-Guillén¹,

Reyes-Heredia²,

Picquart³

et al. 2018

Microemulsion - A Chemical Nanoreactor [Working Title]

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“…Since Co may find its migration into the titania support difficult, these Co species could be part of CoMoO 4 in which Co was in octahedral coordination [59,60]. To achieve a proper comparison between the Co Oh and Co Th species, Gaussian deconvolution (not showed) was carried out considering the representative signals reported in the literature [56,57,61]. Since CoMoO 4 is considered a bad precursor for the CoMoS phase [62], the Co Oh present in this oxide complex was considered as Co Th .…”

Section: Diffuse Reflectance Spectroscopy Uv-vismentioning

confidence: 99%

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

et al. 2019

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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.

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“…Indeed such Co oct-Al entities are suspected to be located near the alumina surface in interaction with Mo entities and to be the precursors of the Co atoms participating in the formation of the CoMoS phase after sulfidation [47] while the Co tet-Al ions that are considered to be deep in the support are known to be less sulfidable [48]. To directly compare the relative amounts of Co oct-Al and Co tet-Al species in our two samples, the UV-Visible spectra were normalized to obtain similar intensities of the band at 425 nm (characteristic of Co oct-Al [49,50]). Upon modification with C 5 diol the relative intensity of the Co tet-Al characteristic bands slightly decreases, meaning that the relative amount of Co tet-Al species is decreased by addition of this organic agent.…”

Section: Uv Spectroscopymentioning

confidence: 99%

Improvement of HDS catalysts through the modification of the oxidic precursor with 1,5-pentanediol: Gas phase sulfidation and thiophene conversion

Blanchard

Frizi

Mary

et al. 2016

Comptes Rendus. Chimie

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Preparation, characterization, and catalytic activity of CoMo/γ-Al2O3 catalysts prepared by equilibrium deposition filtration and conventional impregnation techniques

Cited by 51 publications

References 54 publications

CoMo/γ-Al2O3 Catalysts Prepared by Reverse Microemulsion: Synthesis and Characterization

CoMo/γ-Al2O3 Catalysts Prepared by Reverse Microemulsion: Synthesis and Characterization

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

Improvement of HDS catalysts through the modification of the oxidic precursor with 1,5-pentanediol: Gas phase sulfidation and thiophene conversion

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