Sorption of water, methanol, and ammonia on AlPO sub 4 -5 as studied by multinuclear NMR spectroscopy

Journal Article · Thu Oct 31 00:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100175a073· OSTI ID:7142240

Kustanovich, I; Goldfarb, D ^[1]

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1. Weizmann Inst. of Science, Rehovot (Israel)

Multinuclear NMR measurements were performed on several samples of AlPO{sub 4}-5: samples that are as synthesized, calcined and rehydrated, dehydrated and those obtained after adsorption of methanol and ammonia. The dynamics of the adsorbates was followed by {sup 2}H NMR, which was correlated with the changes the framework undergoes upon adsorption, as manifested by the {sup 31}P and {sup 27}Al MAS NMR spectrum. Water adsorption up to 20% of the total AlPO{sub 4}-5 capacity did not affect the {sup 27}Al and {sup 31}P spectra, and the {sup 2}H NMR spectrum indicates the presence of rather mobile water molecules. When the samples are completely hydrated, the Al spectrum shows the presence of octahedral Al, the {sup 31}P line is significantly broadened, and the {sup 2}H NMR shows the appearance of bound water molecules undergoing a local motion, which could be a {pi} flip about the DOD bisector. These molecules are assigned to water coordinated to the octahedral Al and the flip is about the Al-O axis. The {sup 2}H NMR spectrum of adsorbed ND{sub 3} indicates the presence of two types of molecules, just as in the case of water, with the bound molecules undergoing a rotation about the C{sub 3} axis, along the Al-N axis. In this case three types of Al were detected, tetrahedral, octahedral, and pentacoordinated. While water and ammonia behaved similarly, methanol adsorption did not produce octahedral Al and the methanol molecules were found to freely reorient within the AlPO{sub 4}-5 channels. {sup 31}P T{sub 2} measurements attributed the changes in the {sup 31}P line width to inhomogeneous broadening due to dispersion of chemical shifts. This dispersion was assigned to the changes in the Al neighbors.

• OSTI ID: 7142240
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 95:22; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM PHOSPHATES
SORPTIVE PROPERTIES
AMMONIA
METHANOL
WATER
ALUMINIUM 27
DEUTERIUM
EXPERIMENTAL DATA
LABELLED COMPOUNDS
NUCLEAR MAGNETIC RESONANCE
PHOSPHORUS 31
ALCOHOLS
ALUMINIUM COMPOUNDS
ALUMINIUM ISOTOPES
DATA
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
SURFACE PROPERTIES
400201* - Chemical & Physicochemical Properties