Nature and mechanism of formation of sulfate species on copper/alumina sorbent-catalysts for SO sub 2 removal

Journal Article · Thu May 16 00:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100163a031· OSTI ID:5885963

Waqif, M; Saur, O; Lavalley, J C ^[1]; Perathoner, S; Centi, G ^[2]

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1. ISMRA, Caen (France)
2. Univ. degli studi di Bologna (Italy)

The nature, thermal stability, and reducibility in H{sub 2} of sulfate species on copper-on-alumina and their mechanism of formation during interaction of the sorbent-catalyst with SO{sub 2}-containing flows were studied in a flow microreactor and by Fourier-transform infrared spectroscopy. Spectra of the sulfate species formed on Al{sub 2}O{sub 3}, CuO, CuAl{sub 2}O{sub 4}, and CuO/Al{sub 2}O{sub 3} samples either by impregnation with various amounts of sulfate salts or by direct sulfation with SO{sub 2} + O{sub 2} are compared. The results indicate that, on pure alumina, two types of surface sulfate species form, one more stable at low surface coverage attributed to a type with only one double S{double bond}O bond and the second less stable and more easily decomposed by water vapor, attributed to a SO{sub 3} group linked to an Al-O pair site or to an oligomer species as S{sub 2}O{sub 7}. Sulfation of CuO leads to bulklike CuSO{sub 4}, whereas sulfation of copper aluminate leads to three types of sulfate species, one linked to Al{sup 3+} ions, another to Cu{sup 2+} ions, and the third to sulfate species in interaction both with Al{sup 3+} and Cu{sup 2+} ions. The analysis of the formation of sulfate species on copper-on-alumina sorbent-catalysts suggests the following mechanism: in the presence of gaseous oxygen, copper performs catalytically the first step of oxidation of SO{sub 2} to SO{sub 3} which then forms a stable surface sulfate at either the copper site or the aluminum site. During the first cycle of interaction of the sorbent catalyst with the SO{sub 2}-containing flow, a sulfate linked mainly to Al sites forms in an amount (about 300-400 {mu}mol/g) equivalent to the limiting value of sulfate species on pure Al{sub 2}O{sub 3}. During the first cycle of reduction, copper aluminate sites are reduced to metallic Cu which give rise to the formation of surface species that are completely regenerated in the consecutive treatment with H{sub 2} at 420C.

• OSTI ID: 5885963
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:10; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
ADSORPTION
AIR POLLUTION CONTROL
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
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CHARGED PARTICLES
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HETEROGENEOUS CATALYSIS
HYDROGEN
INFORMATION
INFRARED SPECTRA
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METALS
MOLECULAR STRUCTURE
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NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN COMPOUNDS
POLLUTION CONTROL
REDUCTION
SAMPLE PREPARATION
SORPTION
SPECTRA
SPECTROSCOPY
SULFATES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
SURFACE PROPERTIES
TEMPERATURE EFFECTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS