Vanadium-doped H-SAPO-11 samples were prepared by a high-temoerature solid-state reaction between SAPO-11 and the paramagentic V(IV) species and characterized carefully by ESR and Electron Spin-Echo Modulation(ESEM) studied.
However,subsequent oxida...
Vanadium-doped H-SAPO-11 samples were prepared by a high-temoerature solid-state reaction between SAPO-11 and the paramagentic V(IV) species and characterized carefully by ESR and Electron Spin-Echo Modulation(ESEM) studied.
However,subsequent oxidation result weak paramagnetic V(IV) species,subsequent activation results in the formation of V(IV)species exist as vanadyl ion either as (V(IV)O)^2+ or V^4+.
The (V(IV)O^2+ species seem more probable because of the following reasons.Since SAPO-11 have a low negative framework charge^32,more positively charged species, like V^4+ are not as easily stabilized.Tetravalent vanadium ion can only be observed at or below 77 K, the activated sample of VH-SAPO-11 can be measured even at room temperature.
After adsorption of methanol, ethano, propanol, only one molecule coordinates to (V(IV)O)^2+ was observed in ESR and ESEM spectra.