Structure and distribution of alkali promoter in K/MoS[sub 2] catalysts and their effects on alcohol synthesis from syngas
- Pohang Institute of Science and Technology (Korea, Republic of)
Potassium-promoted MoS[sub 2] catalysts were investigated by scanning Auger electron spectroscopy, electron probe microanalysis, X-ray energy dispersive spectroscopy, and elementary chemical analysis to elucidate the role of potassium on MoS[sub 2]. Fresh samples exhibited a uniform distribution of the alkali elements by CO hydrogenation, whereas the oxidized sample showed a segregation of the potassium component in the bulk of the catalyst. The fresh K[sub 2]CO[sub 3]-, K[sub 2]O[sub 2]-, and K[sub 2]S-promoted MoS[sub 2] catalysts show high selectivities to alcohols and their IR spectra present two characteristics bands at 1650 and 1400 cm[sup [minus]1] assigned to a bicarbonate-like species which is believed to be an active intermediate for the synthesis of alcohols. No such IR bands appear in the cases of K[sub 2]SO[sub 4]- and KCl-promoted MoS[sub 2] and oxidized K[sub 2]CO[sub 3]/MoS[sub 2] catalysts which mainly produce hydrocarbons instead of alcohols. A mechanism based on this intermediate is proposed for the alcohol formation from CO-H[sub 2]. In addition, the enhanced catalytic activity and high selectivity to C[sub 2+] hydrocarbons of the oxidized K[sub 2]CO[sub 3]/MoS[sub 2] is believed to be due to the transfer of electron from the alkali metal diffused into the bulk of MoS[sub 2], resulting in an increase in electron density as well as in the density of states at the Fermi surface. The alkali metal on the MoS[sub 2] acts as a medium for oxygen supply ([open quotes]sponge[close quotes]) in the atmosphere and promotes oxidation of Mo(IV) to Mo(VI) and S[sup 2[minus]] to S[sup 6+] states. 48 refs., 17 figs., 1 tab.
- OSTI ID:
- 5517160
- Journal Information:
- Journal of Catalysis; (United States), Vol. 142:2; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
01 COAL, LIGNITE, AND PEAT
CARBON MONOXIDE
HYDROGENATION
MOLYBDENUM SULFIDES
CATALYTIC EFFECTS
POTASSIUM
ABSORPTION SPECTROSCOPY
ALCOHOLS
AUGER ELECTRON SPECTROSCOPY
CATALYSTS
CHEMICAL PREPARATION
ELECTRON DENSITY
FERMI LEVEL
HETEROGENEOUS CATALYSIS
MICROANALYSIS
OXIDATION
REACTION INTERMEDIATES
STRUCTURAL CHEMICAL ANALYSIS
SYNGAS PROCESS
X-RAY SPECTROSCOPY
ALKALI METALS
CARBON COMPOUNDS
CARBON OXIDES
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
HYDROXY COMPOUNDS
MANAGEMENT
METALS
MOLYBDENUM COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PROCESSING
REFRACTORY METAL COMPOUNDS
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
WASTE MANAGEMENT
WASTE PROCESSING
400201* - Chemical & Physicochemical Properties
010408 - Coal
Lignite
& Peat- C1 Processes- (1987-)