Amorphous vanadium phosphate catalysts prepared using precipitation with supercritical CO2 as an antisolvent

Abstract A new preparative route for vanadium phosphate catalysts is described using supercritical CO 2 as an antisolvent. The amorphous microspheroidal VPO produced is shown to be more active than comparable crystalline VPO catalysts for the selective oxidation of n -butane to maleic anhydride and, furthermore, does not require an extensive pretreatment or activation period to establish full catalytic activity. VPO catalysts prepared using supercritical CO 2 as an antisolvent maintain their amorphous nature throughout the catalyst test period. In contrast, amorphous VPO catalysts can also be prepared by using liquid CO 2 as antisolvent or by solvent evaporation in vacuo ; however, these materials are found to partially crystallise during the oxidation of n -butane. The wholly amorphous catalysts are characterised using transmission electron microscopy, X-ray absorption spectroscopy, 31 P spin-echo mapping, NMR spectroscopy, and X-ray photoelectron spectroscopy. The role of amorphous material in vanadium phosphate catalysis is discussed in detail.

[1]  J. Benziger,et al.  In situ studies of atomic, nano- and macroscale order during VOHPO4·0.5H2O transformation to (VO)2P2O7 , 2001 .

[2]  J. M. Webster,et al.  Amorphous vanadium phosphate catalysts from supercritical antisolvent precipitation , 2001 .

[3]  R. Schlögl,et al.  Characterisation of active phases of a copper catalyst for methanol oxidation under reaction conditions: an in situ X-ray absorption spectroscopy study in the soft energy range , 2001 .

[4]  G. Hutchings,et al.  The Unexpected Role of Aldehydes and Ketones in the Standard Preparation Method for Vanadium Phosphate Catalysts , 2000 .

[5]  D. C. Koningsberger,et al.  The selective oxidation of η‐butane to maleic anhydride: comparison of bulk and supported V–P–O catalysts , 1998 .

[6]  P. Delichère,et al.  Vanadyl pyrophosphate catalysts: Surface analysis by XPS and LEIS , 1998 .

[7]  R. Schlögl,et al.  High‐Pressure Soft X‐Ray Absorption Spectroscopy: A Contribution to Overcoming the “Pressure Gap” in the Study of Heterogeneous Catalytic Processes , 1998 .

[8]  J. Herrmann,et al.  Selective oxidation of n-butane to maleic anhydride on vanadyl pyrophosphate: II. Characterization of the oxygen-treated catalyst by electrical conductivity, Raman, XPS, and NMR spectroscopic techniques , 1998 .

[9]  R. Schlögl,et al.  Hochdruck‐Niederenergie‐Röntgenabsorptionsspektroskopie: ein Beitrag zur Überwindung des „pressure gaps”︁ in der Untersuchung heterogenkatalytischer Prozesse , 1998 .

[10]  Andreas Martin,et al.  Enhancement of the catalytic activity of VPO ammoxidation catalysts by use of vanadyl(IV) orthophosphate precursor compounds , 1998 .

[11]  Andreas Martin,et al.  Structure of vanadium sites in VPO catalysts and their influence on the catalytic performance in selective O- and N-insertion reactions , 1998 .

[12]  F. Lemos,et al.  Catalytic Activation and Functionalisation of Light Alkanes , 1998 .

[13]  Jingguang G. Chen.  NEXAFS investigations of transition metal oxides, nitrides, carbides, sulfides and other interstitial compounds , 1998 .

[14]  J. Volta,et al.  Selective Oxidation ofn-Butane to Maleic Anhydride on Vanadyl Pyrophosphate , 1997 .

[15]  Winston Wang,et al.  Effect of calcination environment on the selective oxidation of n-butane to maleic anhydride over promoted and unpromoted VPO catalysts , 1997 .

[16]  J. Ryczkowski,et al.  Catalytic activation and functionalisation of light alkanes , 1997 .

[17]  C. Pham‐Huu,et al.  Synthesis and Characterization of High Specific Surface Area Vanadium Carbide; Application to Catalytic Oxidation , 1997 .

[18]  J. Bahrdt,et al.  A novel undulator-based PGM beamline for circularly polarised synchrotron radiation at BESSY II , 1997 .

[19]  H. Kung,et al.  The Kinetic Significance of V5+ in n-Butane Oxidation Catalyzed by Vanadium Phosphates , 1997, Science.

[20]  B. Kubias,et al.  In situ-electron spin resonance: a useful tool for the investigation of vanadium phosphate catalysts (VPO) under working conditions , 1996 .

[21]  S. Sundaresan,et al.  The effect of the phase composition of model VPO catalysts for partial oxidation of n-butane , 1996 .

[22]  G. Hutchings,et al.  Effect of Promoters on the Selective Oxidation ofn-Butane with Vanadium-Phosphorus Oxide Catalysts , 1996 .

[23]  G. Hutchings,et al.  Characterisation of Variations in Vanadium Phosphate Catalyst Microstructure with Preparation Route , 1996 .

[24]  J. Fierro,et al.  A Comparison of the Reactivity of “Nonequilibrated” and “Equilibrated” V–P–O Catalysts: Structural Evolution, Surface Characterization, and Reactivity in the Selective Oxidation ofn-Butane andn-Pentane , 1996 .

[25]  Andreas Martin,et al.  Investigation of vanadium phosphorus oxide catalysts (VPO) during toluene ammoxidation: new mechanistic insights by in situ EPR , 1996 .

[26]  R. Szargan,et al.  Influence of zirconium phosphate on the properties of (VO)2P2O7 catalysts for the selective oxidation of n-butane to maleic anhydride , 1996 .

[27]  G. Hutchings,et al.  Structural transformation sequences occurring during the activation of vanadium phosphorus oxide catalysts , 1996 .

[28]  P. Nguyen,et al.  Structure of (VO)2P2O7 , 1995 .

[29]  S. Sundaresan,et al.  Evolution of the active surface of the vanadyl pyrophosphate catalysts , 1995 .

[30]  Andreas Martin,et al.  Redox interaction of ammonia with (VO)2P2O7 , 1995 .

[31]  G. Hutchings,et al.  Role of the product in the transformation of a catalyst to its active state , 1994, Nature.

[32]  J. Volta,et al.  A study by 31P NMR spin echo mapping of VPO catalysts. I: Characterization of the reference phases , 1994 .

[33]  J. Nicholas,et al.  A Concise Description of the Bulk Structure of Vanadyl Pyrophosphate and Implications for n-Butane Oxidation , 1994 .

[34]  A. Fujimori,et al.  Soft X-ray absorption spectroscopy of vanadium oxides , 1993 .

[35]  M. R. Thompson,et al.  An active site hypothesis for well-crystallized vanadium phosphorus oxide catalyst systems , 1993 .

[36]  B. Delmon,et al.  New aspects of the cooperation between phases in vanadium phosphate catalysts , 1993 .

[37]  M. Seah,et al.  Practical Surface Analysis , 1992 .

[38]  N. Guilhaume,et al.  A study by in situ laser Raman spectroscopy of VPO catalysts for n-butane oxidation to maleic anhydride I. Preparation and characterization of pure reference phases , 1992 .

[39]  G. Hutchings.  Effect of promoters and reactant concentration on the selective oxidation of n-butane to maleic anhydride using vanadium phosphorus oxide catalysts , 1991 .

[40]  N. Yamazoe,et al.  Amorphous V-P mixed oxide with P/V=2.0 as active phase for butane oxidation , 1990 .

[41]  Gabriele Centi,et al.  Nature of active species of (VO)2P2O7 for selective oxidation of n-butane to maleic anhydride , 1989 .

[42]  Robinson,et al.  Structural studies of argon-sputtered amorphous carbon films by means of extended x-ray-absorption fine structure. , 1988, Physical review. B, Condensed matter.

[43]  E. Bordes.  Crystallochemistry of VPO phases and application to catalysis , 1987 .

[44]  D. H. Maylotte,et al.  A Study of the K-edge Absorption Spectra of Selected Vanadium Compounds. , 1984 .

[45]  J. Taftø,et al.  Site-Specific Valence Determination by Electron Energy-Loss Spectroscopy , 1982 .

[46]  W. Zachariasen,et al.  THE ATOMIC ARRANGEMENT IN GLASS , 1932 .