HYDROTHERMAL SYNTHESIS AND CHARACTERIZATION OF THE VANADIUM-CONTAINING ZEOLITE-BETA

Vanadium-containing zeolite beta (V-Beta) with molar atomic compositio n of V/Al/Si = 0.013/1/23 was synthesized by direct hydrothermal metho d. The synthesized V-Beta exhibits a unique structure that was charact erized by ICP-mass, XRD, TEM, STEM/EDS, i.r., u.v.-vis, Si-29 and Al-2 7 MAS n.m.r., and EPR spectroscopies. The structure of V-Beta is isomo rphous with H-form zeolite beta (H-Beta) of the same Si/Al ratio and i s like H-Beta in cubic shape, but the average size is significantly la rger. The incorporated vanadium also shows remarkable effect on Si-29 and Al-27 MAS n.m.r, spectra that seems to increase the framework Si/A l ratio and the T-O-T angle of the zeolite Beta. A typical EPR spectru m of vanadyl ions (VO2+) was clearly presented by the synthesized V-Be ta after calcination, and an additional superhyperfine structure due t o interaction with Al-27 appeared after dehydration. The spectroscopic results indicate that isolated V(IV) ions are atomically dispersed at cation or vacant acid sites near Al. The infrared spectrum of pyridin e adsorption shows an enhanced Lewis acidity for the vanadium-containi ng zeolite beta. (C) Elsevier Science Inc. 1977.