Activation of unsupported Co-Mo catalysts in thiophene hydrodesulfurization

Journal Article · Fri Mar 31 23:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90109-7· OSTI ID:6356231

Koranyi, T I; Manninger, I; Paal, Z ^[1]; Marks, O; Guenter, J R ^[2]

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1. Institute of Isotopes of the Hungarian Academy of Sciences, Budapest (Hungary)
2. Univ. of Zuerich (Switzerland)

A series of unsupported oxidic Co-Mo catalysts with different mole fractions r = Co/(Co + Mo) was prepared by coprecipitation of solutions of (NH{sub 4}){sub 6}Mo{sub 7}O{sub 24} and Co(NO{sub 3}){sub 2}. The calcined catalysts contain a-CoMoO{sub 4} (r = 0.5) mixed with MoO{sub 3} (r < 0.5) or with Co{sub 3}O{sub 4} (r > 0.5) according to X-ray diffraction (XRD) and electron diffraction. The a-CoMoO{sub 4} transforms partially into b-CoMoO{sub 4} upon grinding. The higher the cobalt (r) and b-CoMoO{sub 4} contents, the higher are the surface area increase and the degree of reduction of calcined catalysts during hydrogen treatment at 673 K. Electron microscopy (EM) data agree well with the surface area increase observed after reduction. X-ray photoelectron spectroscopy (XPS) shows the reduction of molybdenum rather than that of cobalt. Reduced crystalline phases cannot be identified by these techniques. Sulfidation with a mixture of H{sub 2}/thiophene following reduction caused a drastic drop in surface area but the particle size seen by EM does not increase. Weak oxythiomolybdate XRD bands appeared after slight sulfidation, most XRD signals disappeared after massive sulfidation of samples with r = 0.5. Cobalt promotes sulfidation of molybdenum in the bulk, but the maximum sulfidation degree was about half of the stoichiometric value. XPS shows surface cobalt enrichment, XRD and EM traces of Co{sub 9}S{sub 8} in samples with r = 0.38 and 0.50. A pronounced maximum was observed in initial hydrodesulfurization (HDS) activity and hydrogenation (HYD) selectivity at medium Co content. On used catalysts, this synergism disappeared. The authors attribute the highest HDS activity of short-living cobalt-oxythiomolybdate(s) formed initially during sulfidation. HYD was promoted by sulfided molybdenum and by less surface cobalt.

• OSTI ID: 6356231
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 116:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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CALCINATION
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL ACTIVATION
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COBALT
COBALT COMPOUNDS
COBALT SULFIDES
COHERENT SCATTERING
DECOMPOSITION
DESULFURIZATION
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTS
HETEROCYCLIC COMPOUNDS
HYDROGENATION
METALS
MICROSCOPY
MOLYBDATES
MOLYBDENUM COMPOUNDS
MOLYBDENUM SULFIDES
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PARTICLE SIZE
PHASE TRANSFORMATIONS
PHOTOELECTRON SPECTROSCOPY
PYROLYSIS
QUANTITY RATIO
REDUCTION
REFRACTORY METAL COMPOUNDS
SCATTERING
SIZE
SPECTROSCOPY
SULFIDATION
SULFIDES
SULFUR COMPOUNDS
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS
THERMOCHEMICAL PROCESSES
THIOPHENE
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY