Quick search
Go!

OLIGOVANADATE-PILLARED HYDROTALCITES


MIRON DORU NECULAI, NISTOR DENISA, COSTULEANU ANGELA
UNIVERSITY OF BACÄ‚U

Issue:

TSTM, Number 12, Volume II

Section:

Optimum Materials

Abstract:

In this paper is reported the preparation and characterization of four oligo-vanadate-pillared clays. Oligovanadate-pillared hydrotalcite-type layered materials are expected to be shape-selective oxidation catalysts with tunable acid-base character. These oligo-vanadate-pillared clays are Mg5A12(OH)14(V2O7)0.5 • 5H2O, Mg4A12(OH)12(HV2O7)0.67 • xH2O, Mg5,3 AI2(OH)14,6(V4O12)0.5 • 2H2O, and Mg2Zn2A12(OH)12 (V4O12)0,5 • 2H2O.The novel, one-step synthetic strategy used here was based on the fact that several oligovanadate anions are formed successively in aqueous solutions as a function of pH. For this particular study we focused our attention to the three anions, V4O4-12, HV2O73- and V2O74-. The pH ranges where these anions exist in highest concentrations are: 6,5 to 8,5 for V4O124-, 8,5 to 10 for HV2O73-, and 10 to 13 for V2O74-. These di- and tetravanadate-pillared clays are prepared in one step by carrying out the synthesis at a pH where the desired anion exists in highest concentration. The isolated clays were characterized by elemental analysis, X-ray diffraction, thermal analyses (TGA, DTA), and surface studies.

Keywords:

oligo-vanadat, synthesis of pillared clay.

Code [ID]:

TSTM200612V02S03A0002 [0001521]


Copyright (c) 1995-2007 University of Bacău