Critical role of (100) facets on γ-Al2O3 for ethanol dehydration: Combined efforts of morphology-controlled synthesis and TEM study

Lee, Jaekyoung; Jang, Eun Jeong; Jeong, Hu Young; Kwak, Ja Hun

doi:10.1016/j.apcata.2018.02.018

Cited by 34 publications

(34 citation statements)

References 55 publications

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“…higherP /Mo) leads to an otorious increase in the broad signal at 0.53 ppm (free phosphates) and for P/Mo = 0.57, free phosphates become, by large, the predominant phosphorus species. Therefore, 31 PNMR results show that high phosphorus content in solution necessarily implies a large excessoffree phosphates in such solution.…”

Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 92%

Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 99%

“…The quantitative 31 PNMR spectrum for each solution is shown in Figure 2. 31 PNMR analysisf irst strongly suggests that all phosphorusi ns olutioni sd etected (no precipitation fore xample), since the relative total peak area (S peaks on the Figure normalized to the P/Mo = 0.11c ase) is in agreement with the P/Mo ratio introduced in the solution. In order to ascribe the peaks observed in Figure 2, as ummary of different phospho-molybdic speciesa nd their respective 31 Pc hemical shifts reported in the literature is given in Ta ble 1.…”

Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 99%

“…The most important conclusion that can be drawn from the liquid-state 31 PNMR study of the four solutionsi st hat the speciation of the phosphorus-containing species can be controlled by playing both with the initial P/Mo ratio and with the Mo precursor,w hile keeping the naturalp Ho ft he solutionw hich is typically the case in catalystp reparation. At low P/Mo ratios (i.e.…”

Section: àmentioning

confidence: 99%

“…Liquid-state 95 Mo NMR was carried out for the three different precursor solutions (P/Mo = 0.11,0 .40a nd 0.57) prepared from MoO 3 ,i no rder to confirm the different contributions identified with 31 PNMR, and to detect the possible presence of free molybdates (Mo 7 O 24 6À and MoO 4 2À ). The spectra fort he three different solutionsare displayed in Figure 5.…”

Section: Speciesmentioning

confidence: 99%

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Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Castro

Bertrand

Rigaud

et al. 2020

Chemistry A European J

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Requirements for improved catalytic formulations is continuously driving researchi nh ydrotreating (HDT)c atalysis for biomass upgrading and heteroatom removalf or cleanerf uels. The present work proposes as urface-science approach for the understanding of the genesis of the active (sulfide) phase in model P-doped MoS 2 hydrotreating catalysts supported on a-Al 2 O 3 single crystals. This approach allows one to obtain as urface-dependenti nsightb yv arying the crystal orientationso ft he support. Model phosphorusdoped catalysts are preparedv ia spin-coating of MoP precursor solutions onto four a-Al 2 O 3 crystalo rientations, C(0001), A(112 0), M(101 0) and R(11 02) that exhibit different speciations of surface-OH. 31 Pa nd 95 Mo liquid-state NMR are used to give ac omprehensive description of the Mo andP speciation of the phospho-molybdic precursor solution. The speciation of the deposition solution is then correlatedw ith the genesiso ft he active MoS 2 phase.X PS quantificationo f the surfaceP /Mo ratio reveal as urface-dependent phosphate aggregation driven by the amount of free phosphates in solution.P hosphates aggregation decreases in the following order C(0001) @ M(101 0) > A(112 0), R(11 02). This evolution can be rationalized by an increasing strength of phosphate/surface interactions on the different a-Al 2 O 3 surface orientations from the C(0001) to the R(11 02) plane. Retardation of the sulfidation with temperature is observed for model catalystsw ith the highest phosphate dispersion on the surface(A(112 0), R(11 02)), suggesting that phosphorus strongly intervene in the genesis of the activep hase through ac lose intimacy between phosphates and molybdates.T he surface P/Mo ratio appears as ak ey descriptor to quantify this retarding effect.I ti sp roposedt hat retardation of sulfidation is drivenb yt wo effects:i)achemicali nhibition through formation of hardly reducible mixed molybdo-phosphates tructures and ii)a physicali nhibition with phosphate clusters inhibiting the growth of MoS 2 .T he surface-dependent phosphorus dopingo nm odel a-Al 2 O 3 supportsc an be used as ag uide for the rational design of more efficient HDT catalysts on industrial g-Al 2 O 3 carrier.

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Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 92%

Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 99%

Section: Speciation Of the Mo-p Solutionsmentioning

confidence: 99%

Section: àmentioning

confidence: 99%

Section: Speciesmentioning

confidence: 99%

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Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Castro

Bertrand

Rigaud

et al. 2020

Chemistry A European J

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Positionen von Spinellfehlstellen in γ‐Al₂O₃

Prins

2019

Angewandte Chemie

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Ein Nicht‐Spinellmodell für die Struktur von γ‐Al2O3, bei dem sich 25 % der Al3+‐Kationen an tetraedrischen Positionen befinden, hat viel Interesse erregt. 17O‐NMR‐Messungen und – erst kürzlich – 27Al‐NMR‐Messungen haben aber gezeigt, dass sich erheblich mehr Al3+‐Kationen an tetraedrischen Positionen befinden. Dies bedeutet, dass sich die Al3+‐Fehlstellen in γ‐Al2O3 nicht an tetraedrischen, sondern an oktaedrischen Positionen befinden, wie beim isostrukturellen γ‐Fe2O3 und in Übereinstimmung mit dichtefunktionaltheoretischen Voraussagen. Dies hat Folgen für die Struktur der γ‐Al2O3‐Oberfläche und für die Katalyse.

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Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ‐Alumina**

et al. 2021

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g-alumina is one of the oldest and most important commercial catalytic materials with high surface area and stability.These attributes enabled its use as the first commercial large-scale heterogeneous catalyst for ethanol dehydration. Despite progress in materials characterization the nature of the specific sites on the surface of g-alumina that are responsible for its unique catalytic properties has remained obscure and controversial. By using combined infrared spectroscopy, electron microscopya nd solid-state nuclear magnetic resonance measurements we identify the octahedral, amphoteric (O) 5 Al(VI)-OH sites on the (100) segments of massively restructured (110) facets on typical rhombus-platelet g-alumina as well as the (100) segments of irrational surfaces (invariably always present in all g-alumina samples) responsible for its unique catalytic activity.Such (O) 5 Al(VI)-OH sites are also present on the macroscopically defined (100) facets of g-alumina with elongated/rod-like geometry.T he mechanism by which these sites lose -OH groups upon thermal dehydroxylation resulting in coordinatively unsaturated penta-coordinate Al +3 O 5 sites is clarified. These coordinatively unsaturated penta-coordinate Al sites produce well-defined thermally stable Al-carbonyl complexes.O ur findings contribute to the understanding of the nature of coordinatively unsaturated Al sites on the surface of g-alumina and their role as catalytically active sites.

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Critical role of (100) facets on γ-Al2O3 for ethanol dehydration: Combined efforts of morphology-controlled synthesis and TEM study

Cited by 34 publications

References 55 publications

Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Positionen von Spinellfehlstellen in γ‐Al₂O₃

Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ‐Alumina**

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Critical role of (100) facets on γ-Al2O3 for ethanol dehydration: Combined efforts of morphology-controlled synthesis and TEM study

Cited by 34 publications

References 55 publications

Surface‐Dependent Activation of Model α‐Al2O3‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Surface‐Dependent Activation of Model α‐Al2O3‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Positionen von Spinellfehlstellen in γ‐Al2O3

Precise Identification and Characterization of Catalytically Active Sites on the Surface of γ‐Alumina**

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Product

Resources

About

Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Surface‐Dependent Activation of Model α‐Al₂O₃‐Supported P‐Doped Hydrotreating Catalysts Prepared by Spin Coating

Positionen von Spinellfehlstellen in γ‐Al₂O₃