Influence of the solution pH in impregnation with citric acid and activity of Ni/W/Al2O3 catalysts

Suárez-Toriello, V.A.; Santolalla-Vargas, C.E.; Reyes, J.A. de los; Vázquez-Zavala, A.; Vrinat, M.; Geantet, Christophe

doi:10.1016/j.molcata.2015.04.005

Cited by 65 publications

(46 citation statements)

References 64 publications

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“…However, the reducibility of Ni/Mg.Al.550.CA as mentioned is not as high as that of Ni/Mg.Al.550 ( Figure 5). The sample shows a sharp and symmetric reduction peak with a maximum temperature around 900 • C. These observations suggest that the low reducibility of Ni/Mg.Al.550.CA is primarily due to the higher dispersion of Ni species on the support surface [23], leading to a strong interaction with the Mg.Al material.…”

Section: Characterization Of the Catalystsmentioning

confidence: 99%

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Armbruster

Atia

et al. 2017

Catalysts

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Methane dry reforming (DRM) was investigated over highly active Ni catalysts with low metal content (2.5 wt %) supported on Mg-Al mixed oxide. The aim was to minimize carbon deposition and metal sites agglomeration on the working catalyst which are known to cause catalyst deactivation. The solids were characterized using N 2 adsorption, X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The results showed that MgO-Al 2 O 3 solid solution phases are obtained when calcining Mg-Al hydrotalcite precursor in the temperature range of 550-800 • C. Such phases contribute to the high activity of catalysts with low Ni content even at low temperature (500 • C). Modifying the catalyst preparation with citric acid significantly slows the coking rate and reduces the size of large octahedrally coordinated NiO-like domains, which may easily agglomerate on the surface during DRM. The most effective Ni catalyst shows a stable DRM course over 60 h at high weight hourly space velocity with very low coke deposition. This is a promising result for considering such catalyst systems for further development of an industrial DRM technology.

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Section: Characterization Of the Catalystsmentioning

confidence: 99%

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Armbruster

Atia

et al. 2017

Catalysts

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“…The CoMo and NiMo/Al 2 O 3 catalysts have been extensively studied, meanwhile NiW catalysts have remained less investigated . The importance of NiW/Al 2 O 3 sulfide catalysts is given by their excellent performance in hydrogenation reactions for deep HDS, providing a high potential for the conversion of alkyl‐dibenzothiophenes (alkyl‐DBTs) . HDS catalysts have been the subject of numerous characterization studies, and presently there is a general agreement that the sulfide phase MoS 2 (WS 2 ) presents a lamellar structure, formed by layers of MS 2 (M=W, Mo).…”

Section: Introductionmentioning

confidence: 99%

“…[1] The importance of NiW/Al 2 O 3 sulfide catalysts is given by their excellent performance in hydrogenation reactions for deep HDS, providing a high potential for the conversion of alkyl-dibenzothiophenes (alkyl-DBTs). [2,3] HDS catalysts have been the subject of numerous characterization studies, [4] and presently there is a general agreement that the sulfide phase MoS 2 (WS 2 ) presents a lamellar structure, formed by layers of MS 2 (M=W, Mo). The 2D morphology of these layers, their average stacking (~2 to 4) and their average size (~3 to 6 nm) depends on the sulfidation conditions, the metal loading among other parameters.…”

Section: Introductionmentioning

confidence: 99%

Structure and Quantification of Edge Sites of WS₂/Al₂O₃ Catalysts Coupling IR/CO Spectroscopy and DFT Calculations

et al. 2020

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IR spectroscopy of CO adsorption (IR/CO) and Density Functional Theory (DFT) calculations on sulfide W/Al2O3 catalyst were investigated for an insight into the sulfide edge sites. Parallel between experimental and theoretical results allow to assign the ν(CO) bands at 2121 and 2066 cm−1 to CO adsorption on M‐ and S‐edge sites of WS2 phase, respectively. Through a careful analysis of CO spectra on well‐selected W catalysts, the molar attenuation coefficients for CO adsorbed on the two exposed edges could be determined. This allowed the morphology of WS2 slabs to be calculated. This work shows that increasing the W loading (6–20 wt% W) changes the slab morphology from an almost pure triangle exhibiting mostly M‐edge to a truncated triangle. On W as well as on Mo sulfide catalysts, IR spectroscopy and DFT calculation show that CO adsorption allows to account for M‐ and S‐edge sites, and thus of the morphology of sulfide slabs. It was shown that increasing the W loading shifts the slab morphology from a triangle exposing predominantly M‐edge towards a more hexagonal shape. For close to monolayer coverage of alumina, Mo and W sulfide slabs present similar shape i. e. truncated triangle. However, edge sites of WS2 slabs clearly exhibit greater stability under H2 atmosphere than Mo sulfided ones.

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“…By contrast, very few reports have investigated the effect of the solution pH [10,17] which is an important factor that controls the deprotonation of the chelating agent and electrostatic charge balance on the support surface [17]. For the NiW/g-Al 2 O 3 catalyst prepared using citric acid as chelating agent, the pH control of the nickel-citric acid solution was found to play an important role in the modulation of metal-support interactions, achieving favorable conditions for the formation of the sulfide phase and attaining important increases in the catalytic activity in the HDS of 4,6-dimethyl dibenzothiophene (4,6-DMDBT) [17]. Similar decrease of the Mo-support interaction was reported previously for the dried Mo/SiO 2 eAl 2 O 3 catalysts prepared with ethylenediaminetetraacetic acid (EDTA) [19].…”

Section: Introductionmentioning

confidence: 99%

Effects of pH and chelating agent on the NiWS phase formation in NiW/γ-Al2O3 HDS catalysts

Santolalla-Vargas

Toriello

Reyes

et al. 2015

Materials Chemistry and Physics

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Influence of the solution pH in impregnation with citric acid and activity of Ni/W/Al2O3 catalysts

Cited by 65 publications

References 64 publications

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Structure and Quantification of Edge Sites of WS₂/Al₂O₃ Catalysts Coupling IR/CO Spectroscopy and DFT Calculations

Effects of pH and chelating agent on the NiWS phase formation in NiW/γ-Al2O3 HDS catalysts

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Influence of the solution pH in impregnation with citric acid and activity of Ni/W/Al2O3 catalysts

Cited by 65 publications

References 64 publications

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Development of Active and Stable Low Nickel Content Catalysts for Dry Reforming of Methane

Structure and Quantification of Edge Sites of WS2/Al2O3 Catalysts Coupling IR/CO Spectroscopy and DFT Calculations

Effects of pH and chelating agent on the NiWS phase formation in NiW/γ-Al2O3 HDS catalysts

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Structure and Quantification of Edge Sites of WS₂/Al₂O₃ Catalysts Coupling IR/CO Spectroscopy and DFT Calculations