108-31-6Relevant articles and documents
Surface dynamics of a vanadyl pyrophosphate catalyst for n-butane oxidation to maleic anhydride: An in situ Raman and reactivity study of the effect of the P/V atomic ratio
Cavani, Fabrizio,Luciani, Silvia,Esposti, Elisa Degli,Cortelli, Carlotta,Leanza, Roberto
, p. 1646 - 1655 (2010)
This work focused on investigating the effect of the P/V atomic ratio in vanadyl pyrophosphate, catalyst for n-butane oxidation to maleic anhydride, on the nature of the catalytically active phase. Structural transformations occurring on the catalyst surface were investigated by means of in situ Raman spectroscopy in a non-reactive atmosphere, as well as by means of steady-state and non-steady-state reactivity tests, in response to changes in the reaction temperature. It was found that the nature of the catalyst surface is affected by the P/V atomic ratio even in the case of small changes in this parameter. With the catalyst having P/V equal to the stoichiometric value, a surface layer made of α-VOPO4 developed in the temperature interval 340400°C in the presence of air; this catalyst gave a very low selectivity to maleic anhydride in the intermediate T range (340-400°C). However, at 400440°C δ-VOPO4 overlayers formed; at these conditions, the catalyst was moderately active but selective to maleic anhydride. With the catalyst containing a slight excess of P, the ratio offering the optimal catalytic performance, δVOPO4 was the prevailing species over the entire temperature range investigated (340-440°C). Analogies and differences between the two samples were also confirmed by reactivity tests carried out after in situ removal and reintegration of P. These facts explain why the industrial catalyst for n-butane oxidation holds a slight excess of P; they also explain discrepancies registered in the literature about the nature of the active layer in vanadyl pyrophosphate.
Structure Sensitivity of the Catalytic Oxidation of n-Butane to Maleic Anhydride
Cavani, Fabrizio,Centi, Gabriele,Trifiro, Ferruccio
, p. 492 - 494 (1985)
Disorder along the (020) cleavage plane of the (VO)2P2O7 catalyst considerably enhances the activity of the selective oxidation of n-butane to maleic anhydride.
ΑII-(V1-xWx)OPO4 catalysts for the selective oxidation of n-butane to maleic anhydride
Schulz,Roy,Wittich,d'Alnoncourt, R. Naumann,Linke,Strempel,Frank,Glaum,Rosowski
, p. 113 - 119 (2019)
The vanadyl pyrophosphate (VPP) based catalyst is unique in converting n-butane selectively (60–70%) into maleic anhydride (MAN), whereas a MAN selectivity of 20% may be regarded as high for structurally different catalyst systems. We present novel vanadium phosphorus oxides and mixed metal phosphate solid solutions tested for n-butane oxidation to MAN with a selectivity of >30%. The majority of the catalysts were prepared by solution combustion synthesis. (V1-xWx)OPO4 with αII structure was found to be more active and selective in the oxidation of n-butane compared to β-VOPO4. By adjusting the tungsten content the oxidation state of vanadium in (V1-xWx)OPO4 can be tuned between 4.74 and 4.99, which is regarded as a key factor for MAN production. All catalysts were structurally stable, but the specific surface area increased during the reaction, as detected by X-ray diffraction and N2 physisorption, respectively. (V1-xMox)OPO4 was also stable, but the MAN selectivity was lower compared to β-VOPO4. Low conversions result from the low surface area of the screening samples, however, could be overcome by advanced synthesis protocols.
In Situ FTIR Spectroscopy of 1-Butene and 1,3-Butadiene Selective Oxidation to Maleic Anhydride on V-P-O Catalysts
Wenig, Robert W.,Schrader, Glenn L.
, p. 1911 - 1918 (1987)
The selective oxidation of 1-butene and 1,3-butadiene was studied by transmission infrared spectroscopy.Vanadium-phosphorous-oxygen catalysts prepared by the reaction of V2O5 with H3PO4 in alcohol solution were used.Infrared spectra were collected in situ during the flow of 75 cm3 of 1.5percent hydrocarbon-in-air mixtures over catalysts having P-to-V ratios of 0.9, 1.0, and 1.1.Reaction temperatures from 300 to 400 deg C were investigated with 1-butene feeds, whereas the highly reactive 1,3-butadiene was studied only at 300 deg C.An adsorbed butadiene species, maleic acid, maleic anhydride were observed during both olefin partial oxidation studies.Evidence was obtained for a second olefin species which had been previously observed for in situ n-butane selective oxidation studies.Concentrations of adsorbed species were found to vary with catalyst phosphorous loading, reaction temperature, and time of exposure to reaction conditions.
Activity and Selectivity in Catalytic Reactions of Buta-1,3-diene and But-1-ene on Supported Vanadium Oxides
Mori, Kenji,Miyamoto, Akira,Murakami, Yuichi
, p. 13 - 34 (1986)
The activity and selectivity in the oxidation of buta-1,3-diene, and oxidation and isomerization of but-1-ene on unsupported and supported V2O5 catalysts have been investigated in terms of the catalyst structure.The rate of oxidation is mainly determined by the number of surface V=O species on the catalyst for both buta-1,3-diene and but-1-ene.The roughness of the V2O5 surface affected the activity for buta-1,3-diene, but not for but-1-ene oxidation.It was also found that TiO2 support increases the activity of the surface V=O for but-1-ene oxidation.The selectivity to maleic anhydride was determined by the number of V2O5 layers on the support for both reactions.When the number of V2O5 layers was 1 or 2, the selectivity was low, while it increased markedly with an increase in the number of V2O5 layers to 5, and attained a constant value above 5 layers.Both V2O5 and support were active for the isomerization of but-1-ene to cis- and trans-but-2-ene.On V2O5, the cis/trans ratio was low, while it was as high as 3 for the Al2O3 support.The rate and selectivity of the isomerization on supported catalysts were explained in terms of the structure of V2O5 on the support.Difference in the structure-activity/selectivity correlation between oxidation and isomerization and that between but-1-ene oxidation and buta-1,3-diene oxidation were also discussed.
Effects of cobalt additive on amorphous vanadium phosphate catalysts prepared using precipitation with supercritical co2 as an antisolvent
Lopez-Sanchez, J. Antonio,Bartley, Jonathan K.,Burrows, Andrew,Kiely, Christopher J.,Haevecker, Michael,Schloegl, Robert,Volta, Jean Claude,Poliakoff, Martin,Hutchings, Graham J.
, p. 1811 - 1816 (2002)
The effect of addition of cobalt to an amorphous vanadium phosphate for the selective oxidation of n-butane to maleic anhydride is described and discussed. Cobalt is a well known promoter for crystalline vanadium phosphate catalysts and is most effective at a concentration of 1 atom % relative to vanadium. In contrast, for amorphous vanadium phosphate materials, prepared by precipitation using supercritical CO2 as an antisolvent, cobalt appears to act as a catalyst poison, decreasing both the catalyst activity and selectivity for maleic anhydride. Detailed analysis by transmission electron microscopy, 31P spin echo mapping NMR spectroscopy and X-ray absorption spectroscopy is described, which highlight differences with the unmodified catalyst. It is concluded that the addition of cobalt affects the morphology of the material and the oxidation state of vanadium, and that these changes deleteriously affect the catalytic performance.
Surface Acidity of Vanadyl Pyrophosphate, Active Phase in n-Butane Selective Oxidation
Busca, Guido,Centi, Gabriele,Trifiro, Ferruccio,Lorenzelli, Vincenzo
, p. 1337 - 1344 (1986)
The surface acidity of two (VO)2P2O7catalysts with similar specific activities per square meter of surface area in 1-butene selective oxidation, but different specific activities in n-butane selective oxidation, was studied by ammonia, pyridine, acetonitrile, CO, and CO2 adsorption, by ammonia temperature-programmed desorption, and by 2-propanol oxidation.The results for both catalysts indicate the presence of strong Broensted sites attributed to surface P-OH groups and of medium strong Lewis sites attributed to V(IV) coordinatively unsaturated ions exposed on the surface.The presence of these centers was related to the (VO)2P2O7 structure itself and is fairly independent of the (VO)2P2O7 preparation method.However, in the (VO)2P2O7 prepared in an organic medium and to a lesser extent in the (VO)2P2O7 prepared in an aqueous medium, the presence of very strong Lewis sites also was observed.The enhancement of the rate of n-butane activation in the (VO)2P2O7 prepared in an organic medium was attributed to the presence of these sites.The role of the preparation method in the formation of such very strong Lewis sites also is discussed.
Preparation and characterization of vanadyl hydrogen phosphate hydrates; VO(HPO4)*1.5 H2O and VO(HPO4)*0.5 H2O
Matsuura, Ikuya,Ishimura, Tomohiro,Kimura, Naomasa
, p. 769 - 770 (1995)
A new phase of vanadyl(IV) hydrogen phosphate sesquihydrate, VO(HPO4)*1.5 H2O, has been obtained by the reduction of VOPO4*2H2O with 1-butanol.The unit cell is the orthorhombic system with lattice constants a=7.43 Angstroem, b=9.62 Angstroem, and c=7.97 Angstroem in space group Pmmn.
X-Ray Study of a Vanadium-Phosphorus Mixed Oxide Catalyst for Selective Butane Oxidation to Maleic Anhydride
Bergeret, G.,Broyer, J. P.,David, M.,Gallezot, P.,Volta, J. C.,Hecquet, G.
, p. 825 - 826 (1986)
The radical electron distribution obtained from X-ray patterns has been used to study the structure of a poorly-crystalline vanadium-phosphorus mixed oxide (VPO) catalyst after selective oxidation of n-butane; the effective catalyst consists of a mixture of a crystallized (VO)2P2O7 phase (V(4+)) and an amorphorus VPO phase (V(5+)) showing many corner-sharing VO6 octahedra.
Effects of Consecutive Oxidation on the Production of Maleic Anhydride in Butane Oxidation over Four Kinds of Well-Characterized Vanadyl Pyrophosphates
Igarashi, Hiroshi,Tsuji, Katsuyuki,Okuhara, Toshio,Misono, Makoto
, p. 7065 - 7071 (1993)
Factors determining the selectivity of butane oxidation at high conversion levels have been examined by using four kinds of well-characterized vanadyl pyrophosphate catalysts (C-1 - C-4) in kinetic experiments.The catalysts were carefully characterized by scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and infrared spectroscopy and were made of a single crystalline phase of vanadyl pyrophosphate, (VO)2P2O7.C-1 was prepared by reduction with NH2OH*HCl and consisted of large particles (5 μm) and small particles (0.2 μm).The particles of C-2 obtained from V2O4 had a size of 2 μm.C-3, which was obtained by an organic solvent method, showed a rose-like structure.C-4 from VOPO4*2H2O had a large plate-like structure (5 μm).While all of the catalysts exhibited similar selectivities for the formation of maleic anhydride (63-72 percent) at low conversion levels, the extend of selecticity decreases with an increase in the conversion and strongly depends on the catalysts.It also correlates oppositely with the catalytic activity for the oxidation of maleic anhydride, measured separately.This indicates that the consecutive oxidation of product maleic anhydride is a crucial factor for the selectivity at high conversions.A simulation using a model that includes the consecutive oxidation of maleic anhydride, in which the experimental rate constants for the oxidation of butane and maleic anhydride have been used, reproduced the selectivity-conversion curves experimentally observed.
