Vanadium oxides supported on hydrotalcite-type precursors: the effect of acid-base properties on the oxidation of isopropanol

• Autor(a) principal: Meira,D. M.
• Data de Publicação: 2006
• Outros Autores: Cortez,G. G., Monteiro,W. R., Rodrigues,J. A. J.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Chemical Engineering
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322006000300008
• topic: Mixed oxides; Hydrotalcites; Isopropanol; V-Mg-Al catalysts

Vanadium oxide supported on hydrotalcite-type precursors was studied in the oxidation of isopropanol. Hydrotalcites with different y = Mg/Al ratios were synthesized by the method of coprecipitation nitrates of Mg and Al cations with K2CO3 as precipitant. The decomposition of these hydrotalcite precursors at 450°C yielded homogeneous MgyAlOx mixed oxides that contain the Al+3 cations totally incorporated into the MgO framework. The materials were characterized by chemical analysis, BET superficial area, X-ray diffraction, temperature-programmed reduction (TPR) and the reaction of isopropanol, a probe molecule used to evaluate the acid-base properties. The results of TPR showed that the reducibility of V+5 decreased with the increase in magnesium loading in catalysts. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.