Catalysis Letters

, Volume 36, Issue 3–4, pp 229–235 | Cite as

The temperature-programmed desorption of N2 from a Ru/MgO catalyst used for ammonia synthesis

  • F. Rosowski
  • O. Hinrichsen
  • M. Muhler
  • G. Ertl


The temperature-programmed desorption (TPD) of N2 from a Ru/MgO catalyst used for ammonia synthesis was studied in a microreactor flow system operating at atmospheric pressure. Saturation with chemisorbed atomic nitrogen (N-*) was achieved by exposure to N2 at 573 K for 14 h and subsequent cooling in N2 to room temperature. With a heating rate of 5 K/min in He, a narrow and fairly symmetric N2 TPD peak at about 640 K results. From experiments with varying heating rates a preexponential factor Ades = 1.5×1010 molecules/(site s) and an activation energy Edes = 158 kJ/mol was derived assuming secondorder desorption. This rate constant of desorption is in good agreement with results obtained with a Ru(0001) single crystal surface in ultra-high vacuum (UHV). The rate of dissociative chemisorption was determined by varying the N2 exposure conditions. Determination of the coverage of N-* was based on the integration of the subsequently recorded N2 TPD traces yielding Aads = 2×10−6 (Pa s)−1 and Eads = 27 kJ/mol. The corresponding sticking coefficient of about 10−14 at 300 K is in agreement with the inertness of Ru(0001) in UHV towards dissociative chemisorption of N2. However, if the whole catalytic surface were in this state, then the resulting rate of N2 dissociation would be several orders of magnitude lower than the observed rate of NH3 formation. Hence only a small fraction of the total Rumetal surface area of Ru/MgO seems to be highly active dominating the rate of ammonia formation.


N2 TPD N2 adsorption Ru MgO NH3 synthesis microkinetic analysis 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [1]
    S.R. Tennison, in:Catalytic Ammonia Synthesis, 1st Ed., ed. J.R. Jennings (Plenum Press), New York, 1991 p. 303.Google Scholar
  2. [2]
    K. Aika, T. Takano and S. Murata, J. Catal. 136 (1992) 126.Google Scholar
  3. [3]
    L.R. Danielson, M.J. Dresser, E.E. Donaldson and J.T. Dickinson, Surf. Sci. 71 (1978) 599.Google Scholar
  4. [4]
    Y. Ogata, K. Aika and T. Onishi, Surf. Sci. 140 (1984) L285.Google Scholar
  5. [5]
    T. Matsushima, Surf. Sci. 197 (1988) L287.Google Scholar
  6. [6]
    H. Dietrich, P. Geng, K. Jacobi and G. Ertl, J. Chem. Phys., submitted.Google Scholar
  7. [7]
    C. Egawa, S. Naito and K. Tamaru, Surf. Sci. 138 (1984) 279.Google Scholar
  8. [8]
    W. Tsai and W.H. Weinberg, J. Phys. Chem. 91 (1987) 5302.Google Scholar
  9. [9]
    H. Rauscher, K.L. Kostov and D. Menzel, Chem. Phys. 177 (1993) 473.Google Scholar
  10. [10]
    J.F. Parmeter, U. Schwalke and W.H. Weinberg, J. Am. Chem. Soc. 110 (1988) 53.Google Scholar
  11. [11]
    K. Kunimori, M. Osumi, S. Kameoka and S. Ito, Catal. Lett. 16 (1992) 443.Google Scholar
  12. [12]
    T. Birchem and M. Muhler, Surf. Sci. 334 (1995) L701.Google Scholar
  13. [13]
    H. Shi, K. Jacobi and G. Ertl, J. Chem. Phys. 99 (1993) 9248.Google Scholar
  14. [14]
    C. Egawa, T. Nishida, S. Naito and K. Tamaru, J. Chem. Soc. Faraday Trans. I 80 (1984) 1595.Google Scholar
  15. [15]
    M. Muhler, F. Rosowski and G. Ertl, Catal. Lett. 24 (1994) 317.Google Scholar
  16. [16]
    O. Hinrichsen, F. Rosowski and M. Muhler, Chem.-Ing.-Tech. 66 (1994) 1375.Google Scholar
  17. [17]
    K. Aika and K. Tamaru, in:Ammonia: Catalysis and Manufacture, 1st Ed., ed. A. Nielsen (Springer, Berlin, 1995).Google Scholar
  18. [18]
    B. Fastrup and H.N. Nielsen, Catal. Lett. 14 (1992) 233.Google Scholar
  19. [19]
    T.Z. Srnak, J.A. Dumesic, B.S. Clausen, E. Törnqvist and N.-Y. Topsøe, J. Catal. 135 (1992) 246.Google Scholar
  20. [20]
    H. Knözinger, Y. Zhao, B. Tesche, R. Barth, R. Epstein, B.C. Gates and J.P. Scott, Faraday Discussions Chem. Soc. 72 (1982) 53.Google Scholar
  21. [21]
    P. Moggi, G. Predieri, G. Albanesi, S. Papadopoulos and E. Sappa, Appl. Catal. 53 (1989) L1.Google Scholar
  22. [22]
    R.A. Dalla Betta, J. Catal. 34 (1974) 57.Google Scholar
  23. [23]
    F. Rosowski, A. Hornung, O. Hinrichsen, M. Muhler and G. Ertl, Appl. Catal., submitted.Google Scholar
  24. [24]
    J. Trost, Thesis, Freie Universität Berlin, Germany (1995).Google Scholar
  25. [25]
    Y.-K. Sun, Y.-Q. Wang, C.B. Mullins and W.H. Weinberg, Langmuir 7 (1991) 1689.Google Scholar
  26. [26]
    X. Wu, B.C. Gerstein and T.S. King, J. Catal. 118 (1989) 238.Google Scholar
  27. [27]
    Y. Izumi, M. Hoshikawa and K. Aika, Bull. Chem. Soc. Japan 67 (1994) 3191.Google Scholar
  28. [28]
    J.A. Dumesic, D.F. Rudd, L.M. Aparicio, J.E. Rekoske and A.A. Trevino,The Microkinetics of Heterogeneous Catalysis, ACS professional reference book (Am. Chem. Soc., Washington, 1993).Google Scholar
  29. [29]
    F. Rosowski, O. Hinrichsen, A. Hornung, M. Muhler and G. Ertl, Catal. Lett., in preparation.Google Scholar

Copyright information

© J.C. Baltzer AG, Science Publishers 1996

Authors and Affiliations

  • F. Rosowski
    • 1
  • O. Hinrichsen
    • 1
  • M. Muhler
    • 1
  • G. Ertl
    • 1
  1. 1.Fritz-Haber-Institut der Max-Planck-GesellschaftBerlin (Dahlem)Germany

Personalised recommendations