Characterization and hydrodesulfurization activity studies of unpromoted molybdenum sulfides prepared by elemental solid state reaction
- Univ of Michigan, Ann Arbor (United States)
Solid state reactions of elemental molybdenum and sulfur were used to synthesize unpromoted, model HDS catalysts. The samples studied had synthesis stoichiometries of MoS{sub 2}, MoS{sub 1.95}, and MoS{sub 1.975}. Catalytic activity for the hydrodesulfurization of thiophene was tested in a flow reactor at temperatures ranging from 523 to 673 K and 1 atm of pressure. Characterization of these materials was carried out using X-ray diffraction, electron microscopy, O{sub 2} and CO chemisorption, and X-ray photoelectron spectroscopy. Activity measurements indicate that increased HDS activity coincides with the presence of a nonstoichiometric molybdenum sulfide phase as determined by XRD and electron microscopy. The chemisorption studies revealed that a small reduction in a catalyst's sulfur content could cause a 20-fold increase in BET surface area and a 50-fold increase in O{sub 2} or CO uptake. Normalization of the HDS activity based on chemisorption data using O{sub 2} and CO as probe molecules proved to be a meaningful method for assessing HDS activities. On the stoichiometric MoS{sub 2} sample. XPS showed the presence of significant amounts of surface oxygen even after prolonged treatment in H{sub 2}/H{sub 2}S while surface oxygen was completely removed from the nonstoichiometric samples after reduction under similar conditions. This resulted in greater Mo and S concentrations at the surface of the nonstoichiometric materials, improved the surface sulfiding, and may be linked to higher HDS activity. Additional work is necessary to establish the link between the observed increased in catalytic activity, increased H{sub 2} dissociation capability, and the specific surface reaction mechanism.
- OSTI ID:
- 7241397
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 137:2; ISSN 0021-9517; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
DESULFURIZATION
DIFFRACTION
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTS
HETEROCYCLIC COMPOUNDS
MICROSCOPY
MOLYBDENUM COMPOUNDS
MOLYBDENUM SULFIDES
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHASE STUDIES
PHOTOELECTRON SPECTROSCOPY
REFRACTORY METAL COMPOUNDS
SCATTERING
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
STOICHIOMETRY
SULFIDES
SULFUR COMPOUNDS
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS
THIOPHENE
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY