NMR study of the adsorption of phosphomolybdates on alumina

Cheng, Wing-Chi; Luthra, Narender P.

doi:10.1016/0021-9517(88)90194-7

Cited by 98 publications

(30 citation statements)

References 8 publications

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“…As confirmed by Cheng and Luthra (12), H2P2M05023~ decomposes slowly on the alumina surface. At the very beginning of the impregnation, the H2P2M05023~ ions can therefore move freely In the pores of A203 and only after some time, they slowly decompose into M004~-and P04" ions, which interact strongly with the alumina surface.…”

Section: H' +5t~lo1024~+ 14h2p04-$ M2p2m05024~+ 15h20 (6)supporting

confidence: 72%

PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

Mou

Prins

1995

Bulletin des Soc Chimique

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Several preparative factors which determine the properties of MoP/Al203 catalyst have been studied. With sequential impregnation, the Mo dispersion is always worse than with co-impregnation, while in co-impregnation the pH of the impregnating solution should be properly adjusted according to the P content. Since both mdybdate and phosphate Ions interact strongly with the alumina surface, they can adsorb directly at the pore mouths and inhibit other ions to enter the pores. Especially in the case of sequential impregnation, this results in a non-uniform distribution of Mo and P over the alumina particles. In the case of co-impregnation, with controlled pH and enough phosphoric acid, phosphomolybdate Ions are formed which interact less strongly with the alumina surface. In that case, Mo can reach the inside part of the alumina particles and attain a uniform distribution. Also the Al203 particle size influences the Mo dispersion. Smaller particles have more outer surface and therefore it Is easier for the molybdate and phosphate Ions to diffuse to the centers of the pores, so that there is less chance that bulk Mo compounds are formed.

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Section: H' +5t~lo1024~+ 14h2p04-$ M2p2m05024~+ 15h20 (6)supporting

confidence: 72%

PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

Mou

Prins

1995

Bulletin des Soc Chimique

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“…After impregnation of the alumina support with such a solution and drying, the main lines characteristic of this HPA are still observed (Fig 7c) with an intense line at 880 cm -1 which has not yet been assigned. This shows that a partial decomposition of the P 2 Mo 5 O 23 6-anion occurs during the maturation as suggested by others authors [7,24,25], even if others considered that this entity is stable in the pores of alumina [20]. These contradictions could be assigned to the different experimental conditions under which these studies were carried out.…”

Section: Iii2a Ammonium Heptamolybdate Based Impregnating Solutionsmentioning

confidence: 49%

New insight in the preparation of alumina supported hydrotreatment oxidic precursors: A molecular approach

Blanchard

Lamonier

Griboval-Constant

et al. 2007

Applied Catalysis A: General

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The science on the preparation of the hydrodesulfurization oxidic precursors is coming of age, but the chemistry governing their preparation is not yet clearly understood. In this paper, the chemistry of alumina supported oxomolybdate preparation is revisited taking into account the dissolution/precipitation concept recently developed. Classical preparations with the ammonium heptamolybdate and Co nitrate salts will firstly be discussed. Then the use of new starting materials for the preparation of the impregnating solutions will be considered, showing that at high Mo loading the dispersion is strongly dependant on the nature of the starting salts. The use of phosphomolybdate cobalt salts will also be considered. Lastly we will discuss the improvement of the Co promoting effect using molybdocobaltate heteropolyanions as starting materials and complexing agents. This study shows that the maturation step is the determining step for the improvement of preparation of these alumina based oxidic precursor.

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“…XPS data show that addition of P can lead both to a better and to a worse distribution of the MO species over the support [4,9,14,17,18]. This suggests that the structure of the MO-P catalysts strongly depends on the preparation conditions used, such as pH, P loading and sequence of impregnation.…”

Section: Introductionmentioning

confidence: 99%

“…Most information available is limited to P/AIBOB and MO-P/A&O, catalysts [13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Structure of phosphorus containing CoO—MoO3/Al2O3 catalysts

et al. 1990

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Mangnus, P.J.; van Veen, J.A.R.; Eijsbouts, S.; de Beer, V.H.J.; Moulijn, J.A. Published in: Applied Catalysis DOI:10.1016/S0166-9834(00) Published: 01/01/1990 Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. ABSTRACTThe influence of phosphate (P) on the structure of alumina-supported CO-MO catalysts was studied by means of temperature-programmed reduction (TPR). Conclusions deduced from these TPR measurements were supported by Fourier transform infrared (FT-IR) and Raman measurements. Phosphorus added by sequential impregnation or coimpregnation had a great influence on both Co and MO surface structure. Addition of P to an alumina support resulted in the formation of a well dispersed AlPO, surface layer. Next to the phases already reported on Co/Al,O, catalyst, cobalt can be present in interaction with the AlPO, species in Co-P/A&O, catalysts. Coimpregnation of Co and P increased the dispersion of the cobalt species. The influence of P on the distribution of the MO species depends on the P content and the sequence of impregnation. On MO-P catalysts, prepared by coimpregnation, the reducibility of apart of the MO species decreased with increasing P content due to the formation of MO-O-P species. On the catalysts prepared by sequential impregnation of P and MO a part of the MO was present in MOO, crystallites, the other part was very well distributed over the AlPO, surface layer. These results suggest that at high P loadings, MO can be present as a MO-AlPO, surface structure. Both sequential and coimpregnation of Co, MO and ...

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NMR study of the adsorption of phosphomolybdates on alumina

Cited by 98 publications

References 8 publications

PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

New insight in the preparation of alumina supported hydrotreatment oxidic precursors: A molecular approach

Structure of phosphorus containing CoO—MoO3/Al2O3 catalysts

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NMR study of the adsorption of phosphomolybdates on alumina

Cited by 98 publications

References 8 publications

PREPARATION OF UNIFORMLY DISPERSED MoP/AL2o3 CATALYSTS

PREPARATION OF UNIFORMLY DISPERSED MoP/AL2o3 CATALYSTS

New insight in the preparation of alumina supported hydrotreatment oxidic precursors: A molecular approach

Structure of phosphorus containing CoO—MoO3/Al2O3 catalysts

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PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS

PREPARATION OF UNIFORMLY DISPERSED MoP/AL₂o₃ CATALYSTS