Amorphous AlPO sub 4 as catalyst support: 3. CO FTIR study of AlPO sub 4 impregnated with chromium

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90290-K· OSTI ID:5741059

Rebenstorf, B; Lindblad, T ^[1]

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1. Univ. of Lund (Sweden)

CO FTIR spectra of chromium/AlPO{sub 4} samples give IR bands at 2192 (strong), 2212 (weak), and 2207 (weak) cm{sup {minus}1} at room temperature and after oxidation (O{sub 2}) and reduction(CO) at 500{degree}C. After oxidation at 800{degree}C and reduction at 350{degree}C the main CO band at 2192 cm{sup {minus}1} decreases in intensity at low temperature by 20% and several groups of new CO bands at lower wavenumbers are observed ((1) 2124 and 2071 cm{sup {minus}1}; (2) 2153, 2095, and 2034 cm{sup {minus}1}; (3) 2121, 2109, and 2051 cm{sup {minus}1}). These bands are interpreted as due to CO ligands bridging two chromium(II) ions of dinuclear chromium surface compounds bonded to the AlPO{sub 4} surface through P-O- groups. The ratio of dinuclear chromium(II) surface species to mononuclear ones is estimated from the decrease of the band around 2185 and 2192 cm{sup {minus}1}, respectively (on cooling to low temperatures), as 3 for silica gel and 0.25 for AlPO{sub 4}. A weak CO band at 2202 cm{sup {minus}1} on chromium(III)/AlPO{sub 4} samples is interpreted as caused by CO adsorbed on a chromium(III) surface species attached to AlPO{sub 4} by Al-O- and P-O- groups. Converting this chromium(III) surface species to the chromium(II) one by oxidation at 800{degree}C and reduction at 350{degree}C gives two new CO bands at 2177 and 2167 cm{sup {minus}1} in addition to the one at 2192 cm{sup {minus}1}. On the basis of an increase in the ratio of the integrated absorbance of the PO-H and AlO-H groups and the opposite shift compared with CO bands on chromium(II)/silica gel samples, these IR bands are assigned to CO adsorbed on chromium(II) surface species attached to the AlPO{sub 4} by Al-O- groups.

• OSTI ID: 5741059
• Journal Information: Journal of Catalysis; (USA), Vol. 128:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM PHOSPHATES
SURFACE PROPERTIES
CARBON MONOXIDE
ADSORPTION
ABSORPTION SPECTROSCOPY
AMBIENT TEMPERATURE
CATALYST SUPPORTS
CHROMIUM
COMPARATIVE EVALUATIONS
FOURIER TRANSFORMATION
IMPREGNATION
INFRARED SPECTRA
MICROSTRUCTURE
OXIDATION
REDUCTION
SILICA GEL
ADSORBENTS
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
ELEMENTS
INTEGRAL TRANSFORMATIONS
METALS
OXIDES
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
SORPTION
SPECTRA
SPECTROSCOPY
TRANSFORMATIONS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties