Activation of unsupported Co-Mo catalysts in thiophene hydrodesulfurization

Journal Article · Sat Apr 01 00:00:00 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), Vol. 116:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
02 PETROLEUM
CATALYSTS
CHEMICAL ACTIVATION
COBALT
CATALYTIC EFFECTS
MOLYBDENUM SULFIDES
THIOPHENE
DESULFURIZATION
CALCINATION
CHEMICAL PREPARATION
COBALT COMPOUNDS
COBALT SULFIDES
ELECTRON DIFFRACTION
ELECTRON MICROSCOPY
HYDROGENATION
MOLYBDATES
PARTICLE SIZE
PHASE TRANSFORMATIONS
PHOTOELECTRON SPECTROSCOPY
QUANTITY RATIO
REDUCTION
SULFIDATION
SURFACE AREA
SURFACE PROPERTIES
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DECOMPOSITION
DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
HETEROCYCLIC COMPOUNDS
METALS
MICROSCOPY
MOLYBDENUM COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PYROLYSIS
REFRACTORY METAL COMPOUNDS
SCATTERING
SIZE
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
010402* - Coal
Lignite
&amp; Peat- Purification &amp; Upgrading
020400 - Petroleum- Processing