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Characterization of coprecipitated aluminium–chromium mixed hydroxides and of the products of their calcination

1997; Royal Society of Chemistry; Volume: 7; Issue: 9 Linguagem: Inglês

10.1039/a701344b

1364-5501

J. M. Gallardo‐Amores, Maria del Carmen Prieto, Vicente Sánchez Escribano, Cinzia Cristiani, Marcella Trombetta, Guido Busca,

Mesoporous Materials and Catalysis

Crystalline phases have been coprecipitated from Al/Cr mixed-nitrate aqueous solutions with ammonium carbonate. These phases have been characte rized as probably layered hydroxycarbonates with the likely composition (NH 4 ) 2 (Al,Cr) 6 (OH) 14 (CO 3 ) 3 ·H 2 O, using XRD, FTIR and TG–DTA analyses. The calcination of these materials gives rise to amorphous mixed oxides where Cr is partly in the hexavalent state, while further calcination at 1173 K gives rise to polyphasic materials. Samples with Al: Cr atom ratio between 5:1 and 1:1 give rise to four phase materials with three corundum-type phases and a spinel-type phase. All these phases contain both Al and Cr.