Advertisement

Catalysis Letters

, Volume 13, Issue 1–2, pp 9–19 | Cite as

The molecular structures and reactivity of V2O5/TiO2/SiO2 catalysts

  • Jih-Mirn Jehng
  • Israel E. Wachs
Article

Abstract

A series of V2O5/TiO2/SiO2 catalysts were structurally investigated byin situ Raman spectroscopy and chemically probed by methanol oxidation in order to determine the molecular structure-reactivity relationships of the V2O5/TiO2/SiO2 catalysts. Only surface TiO x species are present on the 3% TiO2/SiO2 catalysts, and the surface TiO x species as well as bulk TiO2 (anatase) particles coexist on the 40% TiO2/SiO2 catalyst. The deposition of 1–3% vanadium oxide onto 3% TiO2/SiO2 and 4% vanadium oxide onto 40% TiO2/SiO2 forms only a surface vanadium oxide phase.In situ Raman studies reveal that the surface vanadium oxide species preferentially exist on the titania sites of the TiO2/SiO2 system. The interaction between the surface vanadia and the surface titania overlayer on SiO2 increases the methanol oxidation reactivity by two orders of magnitude relative to V2O5/SiO2. In the presence of bulk TiO2 (anatase) particles on the SiO7 support, the reactivity of the surface vanadia further increases by an order magnitude relative to the catalysts containing only surface titania, and is close to that of surface vanadia on bulk TiO2. This suggests that the surface VO x -TiO2 (bulk) interactions results in a more active site than the surface VO x -TiO x -SiO2 interactions. In addition, the V2O5/TiO2/SiO2 catalysts exhibit high selectivity towards HCHO because redox sites are predominant on the surface of these catalysts with essentially no acid site present.

Keywords

Vanadia titania silica Raman oxidation 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [1]
    A. Baiker, P. Dollenmeier, M. Glinski and A. Reller, Appl. Catal. 35 (1987) 365.Google Scholar
  2. [2]
    R.B. Bjorklund, C.U. Odenbrand, J.G.M. Brandin, L.A.H. Andersson and B. Liedberg, J. Catal. 119 (1989) 187.Google Scholar
  3. [3]
    R.A. Rajadhyaksha, G. Hausinger, H. Zeilinger, A. Ramstetter, H. Schmelz and H. Knozinger, Appl. Catal. 51 (1989) 67.Google Scholar
  4. [4]
    R.B. Bjorklund, S. Jaras, U. Ackelid, C.U. Odenbrand, L.A.H. Andersson and J.G.M. Brandin, J. Catal. 128 (1991) 574.Google Scholar
  5. [5]
    P. Wauthoz, M. Ruwet, J. Machej and P. Grange, Appl. Catal. 69 (1991) 149.Google Scholar
  6. [6]
    M. Vuurman, I.E. Wachs and A.M. Hirt, J. Phys. Chem., in press.Google Scholar
  7. [7]
    G. Deo and I.E. Wachs, J. Catal. 129 (1991) 137.Google Scholar
  8. [8]
    G. Deo, H. Eckert and I.E. Wachs, Prep. Amer. Chem. Soc. Div. Petrol. Chem. 35 (1) (1990) 16.Google Scholar
  9. [9]
    G.T. Went, S.T. Oyama and A.T. Bell, J. Phys. Chem. 94 (1990) 4240.Google Scholar
  10. [10]
    S.T. Oyama, G.T. Went, K.B. Lewis, A.T. Bell and G. Somorjai, J. Phys. Chem. 93 (1989) 6786.Google Scholar
  11. [11]
    C. Cristinai, P. Forzatti and G. Busca, J. Catal. 116 (1989) 586.Google Scholar
  12. [12]
    H. Eckert and I.E. Wachs, J. Phys. Chem. 93 (1989) 6796.Google Scholar
  13. [13]
    S. Yoshida, T. Tanaka, Y. Nishimura, H. Mizutani and T. Funabiki,Proc. 9th Int. Cong. Catal. 3 (1988) 1473.Google Scholar
  14. [14]
    I.E. Wachs, J. Catal. 124 (1990) 570.Google Scholar
  15. [15]
    S. Srinivasan, A.K. Datye, M. Hampden-Smith, I.E. Wachs, G. Deo, J.M. Jehng, A.M. Turek and C.H.F. Peden, J. Catal. 131 (1991) 260.Google Scholar
  16. [16]
    A. Fernandez, J. Leyrer, A.R. Gonzalez-Elipe, G. Munuera and H. Knozinger, J. Catal. 112 (1988) 489.Google Scholar
  17. [17]
    M.G. Reichmann and A.T. Bell, Appl. Catal. 32 (1987) 315.Google Scholar
  18. [18]
    I.E. Wachs, F.D. Hardcastle and S.S. Chan, Spectroscopy 1 (1986) 30.Google Scholar
  19. [19]
    D.R. Tallant, B.C. Bunker, C.J. Brinker and C.A. Balfe, in:Bettet Ceramics Through Chemistry II, eds. C.J. Brinsker, D.E. Clark and D.R. Ulrich (Materials Research Society, Pittsburgh, PA, 1986) pp. 261.Google Scholar
  20. [20]
    B.G. Varshal, V.N. Denisov, B.N. Mavrin, G.A. Parlova, V.B. Podobedov and Kh.E. Sterin, Opt. Spectrosc. (USSR) 47 (1979) 344.Google Scholar
  21. [21]
    G. Deo, F.D. Hardcastle, M. Richards, I.E. Wachs and A.M. Hirt, in:Novel Materials in Heterogeneous Catalysts, eds. R.T. Baker and L.L. Murrell, ACS Symp. Series 437 (1990) 317.Google Scholar
  22. [22]
    S.S. Chan, I.E. Wachs, L.L. Murrell, W.K. Hall and L. Wang, J. Phys. Chem. 88 (1984) 5831.Google Scholar
  23. [23]
    J.M. Jehng and I.E. Wachs, Catal. Today 8 (1990) 37.Google Scholar

Copyright information

© J.C. Baltzer A.G. Scientific Publishing Company 1992

Authors and Affiliations

  • Jih-Mirn Jehng
    • 1
  • Israel E. Wachs
    • 1
  1. 1.Zettlemoyer Center for Surface Studies, Department of Chemical EngineeringLehigh UniversityBethlehemUSA

Personalised recommendations