Electron spin resonance and electron spin-echo modulation study of paramagnetic Rh species generated in Ca-Y and Na-Y zeolites

Journal Article · Wed Apr 15 04:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00242a011· OSTI ID:6540862

Goldfarb, D; Kevan, L

Paramagnetic Rh species generated in RhNa-Y and RhCa-Y zeolites after various treatments were characterized by using electron spin resonance (ESR) and electron spin-echo modulation (ESEM) spectroscopies. Activation in flowing oxygen at 500/sup 0/C ..beta..-hydrogen a considerable amount of Rh(II) located in site I in the hexagonal prism of the zeolite structure for 3 wt % Rh in RhNa-Y zeolite. Samples of 1 wt % Rh in RhNa-Y and RhCa-Y did not show any paramagnetic signals. Adsorption of various adsorbates such as water, ammonia, methanol, carbon monoxide, and oxygen on activated samples induced a considerable increase in the ESR intensities. Adsorption of oxygen and carbon monoxide yields the corresponding adducts which are located in the ..cap alpha..-cage of the zeolite structure. Hydration generated a species which is coordinated to three water molecules. Adsorption of methanol on RhNa-Y generated a species H2 which is also formed after reduction of RhNa-Y with H/sub 2/, suggesting that the methanol molecule undergoes a reaction to generate products which further reduce Rh(III) species in the ..beta..-cage of the zeolite structure to Rh(II). No significant differences were observed between RhNa-Y and RhCa-Y except for the formation of different Rh(II) species after methanol adsorption in RhCa-Y and the generation of a larger amount of Rh(II) in site I in RhNa-Y. These results are compared to previously obtained data in RhNa-X and RhCa-X to account for the effect of the cocations and the Si/Al ratio on the generation of Rh(II) species in zeolites.

• Research Organization: Univ. of Houston, TX
• OSTI ID: 6540862
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACOUSTIC ESR
ADSORPTION
ALCOHOLS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
AMMONIA
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DATA
ELECTRON SPIN RESONANCE
ELEMENTS
EXPERIMENTAL DATA
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MAGNETIC RESONANCE
MATERIALS
METHANOL
MINERALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
RESONANCE
RHODIUM COMPOUNDS
SODIUM COMPOUNDS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
WATER
ZEOLITES