Oxidation of cobalt based Fischer–Tropsch catalysts as a deactivation mechanism

The oxidation of supported cobalt based slurry bed Fischer–Tropsch catalysts by means of water was studied. Water is one of the Fischer–Tropsch reaction products and can probably cause oxidation and deactivation of a reduced cobalt catalyst. Model experiments using Mossbauer emission spectroscopy and thermogravimetry as well as realistic Fischer–Tropsch synthesis runs were performed. It was demonstrated that Mossbauer emission spectroscopy can successfully be applied to the investigation of high cobalt loading Fischer–Tropsch catalysts. Strong indications were found that oxidation of reduced cobalt catalysts occurs under realistic Fischer–Tropsch conditions. Mossbauer emission spectroscopy and thermogravimetry results showed that the oxidation depends on the PH2/PH2O ratio, and that oxidation proceeds to less than complete extents under certain conditions. The formation of both reducible and less reducible cobalt oxide species was observed, and the relative ratio between these species depends on the severity of the oxidation conditions.

[1]  J. G. Goodwin,et al.  In-Situ XAFS Investigation of K-Promoted Co Catalysts , 1995 .

[2]  C. D. Spencer,et al.  Mössbauer study of several cobalt spinels using Co 57 and Fe 57 , 1974 .

[3]  J. Geus,et al.  Nickel-iron catalysts prepared by homogeneous deposition-precipitation of cyanide complexes on a titania support , 1995 .

[4]  Rocco Anthony Fiato,et al.  Bimetallic Synergy in Cobalt Ruthenium Fischer-Tropsch Synthesis Catalysts , 1993 .

[5]  Fischer-tropsch synthesis on cobalt catalysts: Structural requirements and reaction pathways , 1997 .

[6]  J. Moulijn,et al.  Temperature-programmed reduction of CoOAI2O3 catalysts , 1985 .

[7]  J. Niemantsverdriet,et al.  Characterization of surface phases in bimetallic FeRhSiO2 catalysts by in situ Mössbauer spectroscopy at cryogenic temperatures , 1984 .

[8]  C. Satterfield,et al.  Intrinsic kinetics of the Fischer-Tropsch synthesis on a cobalt catalyst , 1991 .

[9]  L. Guczi,et al.  New frontiers in catalysis : proceedings of the 10th International Congress on Catalysis, Budapest, July 19-24, 1992 , 1993 .

[10]  J. Niemantsverdriet,et al.  Characterization of FeRu/TiO2 and Fe/TiO2 catalysts after reduction and Fischer-Tropsch synthesis by Mössbauer spectroscopy , 1986 .

[11]  Claire A. Chanenchuk,et al.  The Fischer-Tropsch synthesis with a mechanical mixture of a cobalt catalyst and a copper-based water gas shift catalyst , 1991 .

[12]  J. Niemantsverdriet,et al.  Mössbauer Spectroscopy of Iron and Iron Alloy Fischer-Tropsch Catalysts , 1986 .

[13]  A. Holmen,et al.  Reoxidation of supported cobalt Fischer-Tropsch catalysts , 1997 .

[14]  D. Beer,et al.  Sulfidation of Co/Al2O3 and CoMo/Al2O3 catalysts studied by Mössbauer emission spectroscopy , 1993 .

[15]  B. Clausen,et al.  Importance of Co-Mo-S Type Structures in Hydrodesulfurization , 1984, Catalysis and Surface Science.

[16]  S. Mørup,et al.  Mössbauer emission studies of calcined CoMoAl2O3 catalysts: Catalytic significance of Co precursors , 1984 .

[17]  A. Holmen,et al.  The effect of water on cobalt Fischer-Tropsch catalysts studied by steady-state isotopic transient kinetic analysis (SSITKA) , 1997 .

[18]  A. Holmen,et al.  Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts , 1995 .

[19]  W. Nicholas Delgass,et al.  Spectroscopy in Heterogeneous Catalysis , 1979 .

[20]  R. Everson,et al.  Cobalt as an alternative Fischer-Tropsch catalyst to iron for the production of middle distillates , 1997 .