Trunschke, A.

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MPG.PuRe

Nanostructured Molybdenum Oxide Catalysts for the Selective Oxidation of C3 Hydrocarbons4th ELCASS MEETING October 22-26, 2005, ROSCOFF, A. TrunschkeFritz-Haber Institute of the Max Planck SocietyDepartment of Inorganic Chemistry, Berlin, Germany24th ELCASS MEETING October 22-26, 2005, ROSCOFFBackgroundH3CH2CCH3 H2CHCCH3 H2CHCCOHH2CHCCOOH+ 1/2 O2- H2O+ O2- H2O+ 1/2 O2MoBi MoVWT ca. 350°CMoVTeNbT ca. 250°CY ≤ 87%• Modified vanadium pyrophosphate (VPO) catalysts• Ce/VPO (YAA ca. 19%)• VPO/TiO2-SiO2 (YAA ca. 13%)• Heteropoly acids and salts• H1.26Cs2.5Fe0.08P1V1Mo11O40 (YAA ca. 13%)• Multi-component metal oxide catalysts• Mo1V0.3Te0.23Nb0.125Ox (YAA ca. 48%)¾ T. Ushikubo, H. Nakamura, Y. Koyasu, S. Wajiki,Mitsubishi Kasei Corporation, US 005380933A (Jan.10, 1995).Examples of catalysts studied in propane oxidation to acrylic acid34th ELCASS MEETING October 22-26, 2005, ROSCOFF(NH4)6Mo7O24(0.126 mol Mo) / 100 ml H2OT = 80°C / pH = 5.0NH4VO3 (0.038 mol V)(powder)MoV0.30T = 80°C / pH = 5.5Te(OH)6 (0.029 mol Te)(powder)(NH4)[NbO(C2O4)2(H2O)2] 3H2O (0.016 mol Nb) / 30 ml H2OT = 23°C / pH = 0.8MoV0.30Te0.23Nb0.13(slurry)T = 25°C / pH = 3.2MoV0.30Te0.23T = 80°C / pH = 5.0MoV0.30Te0.23Nb0.13(precursor)cool down to 40°C600°C (2 °C/min) / 2 h He flowMoV0.30Te0.23Nb0.13(calcined)275°C (10°C/min) / 1h static airMoV0.30Te0.23Nb0.13(activated)spray-dryingPreparation of MoVTeNbOxFurther synthetic strategies:•Hydrothermal synthesis•Addition of diluents•Addition of noble metalsRu-[PMo]-MoVTeNbOx44th ELCASS MEETING October 22-26, 2005, ROSCOFF800 850 900 950 1000 1050 MoVTe,T=80°C,pH=5.0  Raman shift [cm-1] MoV,T=80°C,pH=5.5  intensity [a.u.]ν [cm-1] assignment937 (s)893 (m)950 (sh)980 (s)956 (m)848 (m)ν (Mo=O) Mo7O246-ν(V=O) [VO3]nn-ν (V=O) [V10O28]6-ν (V-O-V) or ν (Mo-O-V)1000 (m)975 (vw)937 (s)899 (m)ν (V=O) [HxV10O28](6-x)-or ν (M=O) [TeMo5VO24]7-ν (Mo=O) [TeMo6O24]6-I.L. Botto et al. Mater. Chem. Phys.47 (1997) 37.TeMo6 = 0.126 mol Mo + 0.021 mol Teresidual 0.008 mol Te(OH)6 not detectable[TeM6O24]6-M=Mo, VRaman spectroscopy on mixied solutions54th ELCASS MEETING October 22-26, 2005, ROSCOFFMolar ratios of elements normalized to Mo from EDXspot 1 spot 2 spot 3 spot 4 synthesisMo 1 1 1 1 1V 0.30 0.33 0.28 0.35 0.3Te 0.28 0.24 0.25 0.27 0.23Nb 0.22 0.13 0.20 0.20 0.1251234MoVTeNb800 825 850 875 900 925 950 975 1000 1025MoVTe  intensity [a.u.]Raman shift [cm-1]MoVTeNbSpray-dried precursor64th ELCASS MEETING October 22-26, 2005, ROSCOFF1. Calcination in static air up to 275°C (10°C/min)2. Activation in flowing He up to 600°C (2°C/min)300 400 500 600 700 800 9001E-111E-10DSC signal [μvolts/mg]Weight [% of initial] Temperature [K]Ion current [A] m/e 17 m/e 18 m/e 28 m/e 30 m/e 4492949698100 Exo  -0,050,000,050,100,150,200,250,30300 350 400 450 500 5501E-111E-101E-9 DSC signal [μvolts/mg]Weight [% of initial]  m/e 17 m/e 18 m/e 30 m/e 44Ion current [A]Temperature [K]80859095100Exo -0,20-0,15-0,10-0,050,000,050,10Thermal pretreatment74th ELCASS MEETING October 22-26, 2005, ROSCOFF2 Theta [°]5 10 20 30 40 50 60 70spray-driedcalcined 1h air, 275°Cactivated 2h He, 600°CM1M2Development of the phase structure10 15 20 25 30 35 40 2Theta (°)450oC475oC500oC525oC550oC575oCM1M2MoO3PtTePt3Te4He 2°C/min84th ELCASS MEETING October 22-26, 2005, ROSCOFFT. Ushikubo et al. Stud. Surf. Sci. Catal. 112 (1997) 473.P. De Santo et al. Z. Kristallogr. 219 (2004) 152.M1 M2Other phases, e.g.:•Mo5-x(V/Nb)xO14•TeMo5O16•MoO3, Te+ amorphous fractionsb=26.6 Åc=4 Åa=21.1 ÅStructure models94th ELCASS MEETING October 22-26, 2005, ROSCOFFMolar ratio of elements normalized to Mo from EDXspot 1spot 2spot 3spot 4spot 5M1 M2Mo 1 1 1 1 0 1 1V 0.28 0.35 0.31 0.33 0 0.15 0.32Te 0.12 0.39 0.14 0.32 1 0.12 0.42Nb 0.11 0.12 0.22 0.09 0 0.13 0.081 2 345XPS: Mo1V0.19Te0.19Nb0.14OxMicrostructure104th ELCASS MEETING October 22-26, 2005, ROSCOFFMo 3d3/2 V 2p3/2Catalyst V oxida-tion stateMo V Te Nb 5+/red.678 1 0.24 042 0.11 23/77671 1 0.20 0.24 0.15 30/70679 1 0.21 0.24 0.15 41/59nominal 1 0.30 0.23 0.13M1 1 0.15 0.12 0.13Atomic percentage (XPS) normalized to MoElectronic structure / surface composition and catalytic properties114th ELCASS MEETING October 22-26, 2005, ROSCOFF0510152025303540100 150 200 250 300 350 400 450Time (min)IntensityM45 acetaldehydeM57 acroleinM59 C3 oxM31 formaldehyde473K623K298K(Mo0. 91V0.09)5O14RT-O2-Mo3d_118...Intensity(a.u.)240 238 236 234 232 230 228Binding Energy (eV)Mo3d Surface232,5 298K473K623K232,2232,2231,4 97.022.9892.027.9893.586.4292.897.1192.527.4892.087.9288.0090.0092.0094.0096.0098.00100.00FeedRT,bulkFeedRT,surfFeed350bulkFeed350surfFeed200,bulkFeed200,surfMo and V ratio #1862 VMo„feed“: molar ratio C3H6 : O2 = 1:2p = 0.5 mbarElectronic structure / surface composition of a model catalyst124th ELCASS MEETING October 22-26, 2005, ROSCOFFSurface texturing of M1 phase viewed along the [4] zone-axis.  Surface texturing134th ELCASS MEETING October 22-26, 2005, ROSCOFFComposition of the structural ill-defined region144th ELCASS MEETING October 22-26, 2005, ROSCOFFSummary• The preparation routine for the multi metal oxide Mo1V0.30Te0.23Nb0.125Oxused as catalyst for the selective oxidation of propane to acrylic acid was investigated.• Anderson-type heteropoly anions [TeM6O24]6-, M=Mo, V, and protonated decavanadate species [HxV10O28](6-x)- coexist in solution. These species are preserved after spray-drying. • Calcination of this X-ray amorphous material seems to be an essentiallstep, leading to a re-arrangement of the tellurate building blocks and generating amorphous precursors of the crystalline phases.• The chemical composition of the surface of the catalyst differs from thebulk. The near surface composition of model catalysts and the oxidationstate of the metals strongly depend on temperature and gas phasecomposition.• Surface texturing of catalyst particles is revealed by high-resolution TEM.• Area confined EELS measurements reveal Mo, V, and O at the surface as well as in the bulk material. 154th ELCASS MEETING October 22-26, 2005, ROSCOFFPreparation and test of propane oxidation catalysts:M.H. Looi, E.M. Omar, R.M. Salim, R.K. Widi, S. B. Abd HamidUniversity Malaya, Kuala Lumpur, MalaysiaPreparation of catalysts:F.A. Hamid, A. Blume, O. Timpe, A. Celaya SanfizRaman:P. BeatoX-ray Diffraction:V. Makwana, F. Girgsdies, T. ResslerXPS:U. Wild, P. Schnörch, S. Zafeiratos, A. Knop-GerickeSEM/TEM:G. Weinberg, J. Wagner, D. SuR. SchlöglBessy II is acknowledged for providing beamtime for this work.Acknowledgements

Nanostructured Molybdenum Oxide Catalysts for the Selective Oxidation of C3 Hydrocarbons

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