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

Abstract

-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 K 2 CO 3 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.

Physical Properties and Bifunctional Catalytic Performance of Phosphate–Vanadium Impregnated Silica–Titania Aerogel

“…Besides, the interlayer doping of vanadium oxide on hydrotalcite-type materials facilitated the formation of both Brønsted and Lewis sites [10]. In contrast, the presence of vanadium in Y-zeolite appeared to neutralize the acid sites in this material, resulted in a decrease of Brønsted acid sites [11].…”

Synthesis and Characterization of Ni/Hydrotalcite and Its Application in Hydrocracking Calophyllum Inophyllum Oil

“…After hydrotalcite was calcinated and nikel was impregnated, it has 3 main peaks at 43,26°, 43,93° dan 62,93°. Meira [12] found the same peak that correspond to MgO (Magnesium Oxide). Comelli [13] reported that hydrotalcite is calcined at 600°C a form of magnesium oxide is observed, as shown at Fig.3.…”

Evaluation of the reactivity, selectivity and lifetime of hydrotalcite-based catalysts using isopropanol as probe molecule

“…The literature results indicate that the dehydration of the alcohol to acetone is able of revealing the basic character of the catalysts. However, this last point is still controversial, because the acetone formation can also involve an oxidation-reduction mechanism, particularly at low temperatures [21,39]. The activity of the isopropanol transformation shows that the acetone formation increases with the rise of the temperature reaction and it is favored by the presence of Mg in the HDL structure (NiMgAl-CO 3 -c).…”

“…As a conclusion, the activity of MgAl pure, after calcination at 450 °C, the XRD analysis showed the presence of mixed oxides: MgO with Al 2 O 3 . The catalytic activity behavior of this sample via isopropanol decomposition is to produce acetone through strong basic sites [21]. In addition, the combination of MgO-Al 2 O 3 promotes the formation of suitable basic sites [1].…”