NEW POROUS GA CR MIXED-OXIDE PILLARED ALPHA-ZIRCONIUM PHOSPHATE MATERIALS/

Mixed oligomeric solutions of gallium(III) and chromium(III), with Ga: Cr mole ratios between 10:90 and 90:10, have been prepared by adding n -propylammonium acetate and n-propylamine to the mixed nitrate solutio ns at pH 4.4-4.5. The mixed oxyhydroxyacetate oligomers thus obtained were intercalated into colloidal alpha-zirconium phosphate or precipit ated with an excess of n-propylamine. Whilst the mixed precipitates sh ow X-ray diffraction (XRD) reflections typical of mixed GaxCr2-xO3 oxi des after calcination above 400 degrees C, most of the mixed intercala tes were amorphous between room temperature and 800 degrees C, and onl y after calcination at 1000 degrees C were XRD reflections correspondi ng to zirconium pyrophosphate and Ga/Cr mixed oxides observed. These r esults suggest that mixed Ga/Cr oxide pillared alpha-zirconium phospha te materials are formed at 400-800 degrees C. The mixed pillared mater ials with Ga:Cr ratios < 60:40 have high BET surface areas (200-300 m( 2) g(-1)) and micropore volumes (0.08-0.11 cm(3) g(-1)).(1) Higher Ga: Cr ratios lead to materials with BET surface areas lower than 100 m(2) g(-1) and low micropore volumes. The mixed oxide powders also present high BET surface areas (184-236 m(2) g(-1)) and micropore volumes (0. 08-0.10 cm(3) g(-1)), probably due to a templating effect of the aceta te ion. A comparison of the bulk and surface compositions of pillared materials, obtained by chemical analysis and X-ray photoelectron spect roscopy (XPS), respectively, reveal that, at least up to a Ga:Cr ratio of 60:40, the intercalated species into the phosphate are mixed oligo mers.