Catalytic activity of vanadyl phosphate supported on TiO₂ (anatase) and SiO₂ (silica)

Abstract

M. MARTINEZ-LARA, L. MORENO-REAL, R. POZAS-TORMO, A. JIMENEZ-LOPEZ, S. BRUQUE, P. RUE, and G. PONCELET. Can. J. Chem. 70, 5 (1992).Oxidation of n-butane was investigated on vanadyl phosphate (VP) prepared in the presence of titania (anatase) and silica as supports. In the case of silica, a-VOPO, was synthesized with no sign of interaction between the silica surface and vanadium phosphate. On the contrary, titania was coated with amorphous VP (P/V = l), preventing the crystallization of VOPO, at least up to the VP content of 21%. rz-Butane was completely converted into C 0 2 for the VP/Ti02 catalytic system. Upon impregnation with metal sulfates, maleic anhydride (MA) was produced with selectivities depending on the nature of the added metallic species, the best effect being observed with Fez+ (V/Fe = 3). Selectivities to MA were influenced by the P/V ratio, with a maximum at P/V = 1.2.Key words: vanadyl phosphate, maleic anhydride, butane oxidation, anatase, rutile. On a ktudi6 l'oxydation du butane sur de phosphate de vanadyle (PV) prkpare en prksence de titania (anatase) et de silica comme supports. Dans le cas de la silice, on a synthktise du a-VOPO, sans signes d'interactions entre la surface de la silice et le phosphate de vanadium. Au contraire, le titania etait couvert de PV (P/V = 1) et cette situation emp&che la cristallisation du VOP04, au moins jusqu'a un contenu en PV de 21%. Avec le systirme catalytique PV/Ti02, le butane est completement transform6 en COz. Apres imprkgnation sur des sulfates mktalliques, il y a formation d'anhydride malkique (AM) avec des s6lectivitCs qui d6pendent de la nature des especes mktalliques ajoutkes; les meilleurs resultzits sont obtenus avec le Fe" (V/Fe = 3). Les s6lectivitks en AM sont influenckes par le rapport P/V; le maximum se situe a P/V = l , 2 .Mors clbs : phosphate de vanadyle, anhydride malkique, oxydation du butane, anastase, rutile.[Traduit par la rkdaction]

Supported VPO Catalysts for Selective Oxidation of Butane. II. Characterization of VPO/SiO2 Catalysts

“…However, the use of a support also introduces support−oxide interactions that could affect the formation of the VPO phases. Indeed, reports in the literature all show much lower selectivity for maleic anhydride formation over supported as compared to unsupported VPO catalysts. − However, these reports did not provide sufficient information to understand the difference. Therefore, we have initiated a research program to characterize supported VPO catalysts to gain an understanding of the support effect and to determine the chemical properties important for high selectivity.…”

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“…In literature, only a few other examples of deposition of V-P-O on silica [8][9][10], titania [11], alumina [11][12][13][14] and AlPO 4 [15] have been described. Generally, the lack of long-range order of the supported V-P-O particles compromises a proper characterisation of the supported V-P-O phase with common techniques like X-ray diffraction or FTIR spectroscopy.…”