Amorphous AlPO sub 4 as catalyst support: 2. Characterization of amorphous aluminum phosphates

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

DOI:https://doi.org/10.1016/0021-9517(91)90289-G· OSTI ID:5530537

Rebenstorf, B; Lindblad, T; Andersson, S L.T. ^[1]

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1. Univ. of Lund (Sweden)

Three different amorphous aluminum phosphates have been characterized by their specific surface area and pore volume and by XPS and FTIR studies. Three types of Al surface hydroxyl groups at 3793.8, 3768.5, and 3743.2 cm{sup {minus}1} and only one type of P surface hydroxyl groups at 3677.5 cm{sup {minus}1} are found in FTIR spectra after evacuation at 800{degree}C. The ratio of the integrated absorbance of the IR bands from AlOH and POH surface groups is a sensitive tool to study the surface of AlPO{sub 4} directly. A linear relation between the electronegativity of the metal ion and the stretching vibration of surface hydroxyl groups is proposed for Al, Si, P, and B tetrahedral surface ions. The three Al surface hydroxyl groups are assigned to four-coordinated (tetrahedral), five-coordinated, and six-coordinated surface Al ions. Amorphous AlPO{sub 4} contains four- and five-coordinated Al ions and AlPO{sub 4} with high specific surface area also has six-coordinated Al ions at the surface. CO is adsorbed on the phosphorus surface hydroxyl groups at low temperature, giving an IR band at 2170 cm{sup {minus}1}, while the IR band from the PO-H group is shifted to 3495 cm{sup {minus}1}. On AlPO{sub 4} of high surface area, CO is also adsorbed on coordinatively unsaturated, five-coordinated Al surface ions. Four-coordinated Al ions are also found, but none with the coordination number three. Impregnation with chromium compounds in ethanol does not change the specific surface area, whereas impregnation in water resulted in a decreased specific surface area, to less than half of its previous value.

• OSTI ID: 5530537
• 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
PHYSICAL PROPERTIES
SURFACE PROPERTIES
ABSORPTION SPECTROSCOPY
ADSORPTION
ALUMINIUM HYDROXIDES
AMORPHOUS STATE
CARBON MONOXIDE
CATALYST SUPPORTS
CHROMIUM
ETHANOL
FOURIER TRANSFORMATION
HYDROXIDES
HYDROXYL RADICALS
IMPREGNATION
INFRARED SPECTRA
MICROSTRUCTURE
PHOSPHORUS COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
POROSITY
SURFACE AREA
WATER
X-RAY SPECTROSCOPY
ALCOHOLS
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CRYSTAL STRUCTURE
ELECTRON SPECTROSCOPY
ELEMENTS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INTEGRAL TRANSFORMATIONS
METALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOSPHATES
RADICALS
SORPTION
SPECTRA
SPECTROSCOPY
TRANSFORMATIONS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties