Surface structure and catalytic activity of MoO/sub 3//Al/sub 2/O/sub 3/ catalysts in the hydrodesulfurization of thiophene studied by x-ray photoelectron spectroscopy
The relationships between surface structure and catalytic activity of MoO/sub 3//Al/sub 2/O/sub 3/ catalysts in the hydrodesulfurization of thiophene (at 400/sup 0/C and atmospheric pressure of thiophene/H/sub 2/) were investigated by x-ray photoelectron spectroscopy (XPS), coupled with various physicochemical techniques including pyridine adsorption experiments. It was found that the intrinsic activity of molybdenum (thiophene conversion /g of MoO/sub 3/) depended simply on the sulfidation degree of molybdenum determined by XPS regardless of the loading amount of MoO/sub 3/ (2.4-23.1 wt % MoO/sub 3/), the calcination temperature (550 and 700/sup 0/C), and the pretreatment conditions (prereduction with H/sub 2/, presulfidation with CS/sub 2//H/sub 2/ and nonpretreatment). The intrinsic activity showed a maximum at S/Mo = 1 (atomic ratio), forming a good volcano-type correlation. In the low sulfur content region (S/Mo < 1), it was revealed by XPS that S/Mo(IV) = 1.0 +- 0.2. To interpret consistently these features, pyridine adsorption results, and sintering behavior of molybdenum, it is proposed that a molybdenum species (1) having a composition of S/Mo(IV) = 1 is present in the sulfided catalysts as well as MoS/sub 2/. Species 1 shows much higher intrinsic activity for the reaction than MoS/sub 2/ because of the higher anion vacancy concentration in it, induced by better dispersion. The structure of species 1 and the hydrodesulfurization mechanism on species 1 are suggested on the basis of the above observations. The surface structures of oxidic and sulfided MoO/sub 3//Al/sub 2/O/sub 3/ catalysts are discussed mainly on the basis of the XPS results.
- Research Organization:
- Osaka Univ., Toyonaka, Japan
- OSTI ID:
- 5130331
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 84:14
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
MOLYBDENUM OXIDES
CATALYTIC EFFECTS
SURFACE PROPERTIES
THIOPHENE
DESULFURIZATION
ALUMINIUM OXIDES
CATALYSIS
EXPERIMENTAL DATA
HYDROGENATION
PHOTOELECTRON SPECTROSCOPY
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
ELECTRON SPECTROSCOPY
HETEROCYCLIC COMPOUNDS
INFORMATION
MOLYBDENUM COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)