Abstract
ZrOx/SiO2 and VOx/ZrOx/SiO2 catalysts (5 wt %–25 wt % Zr, 4 wt % V) were prepared by grafting zirconium and vanadium alkoxides on Aerosil 380. All samples were characterized by temperature programmed reduction, N2 physisorption, X-ray diffraction, Raman spectroscopy, and ammonia adsorption microcalorimetry. Tetragonal ZrO2 and zircon (ZrSiO4) were present at 25 wt % Zr, but only amorphous zirconia overlayer existed for lower loadings. At lower Zr loadings (5 wt %–10 wt % Zr), exposed silica surface leads to V2O5 crystallites and isolated VO4 species, although V reducibility behavior changes, from being similar to VOx/SiO2 (5 wt % Zr) to showing VOx/ZrO2 behavior at 10 wt % Zr, and a diminished total amount of reducible V. Highly acidic ZrO2 sites are covered by the vanadium grafting, forming weaker sites (60–100 kJ/mol NH3 adsorption strength). Catalytic conversion and selectivity for the oxidative dehydrogenation of n-butane (673 K, n-C4/O2 = 2.2) over VOx/ZrOx/SiO2 show that 1,3-butadiene is favored over cis-2-butene and trans-2-butene, although there is some selectivity to the 2-butenes when VOx/ZrO2 behavior is evident. At low Zr loadings, butadiene formed during reaction acts as the diene species in a Diels–Alder reaction and gives rise to a cyclic compound that undergoes further dehydrogenation to produce benzaldehyde.
Highlights
The last few years have seen a growing interest in cycloaddition reactions, such as Diels–Alder, followed by dehydrogenation to produce aromatic compounds in a novel fashion from diverse feedstocks, such as those that come from biomasses [1]
An important aromatic compound used in the food, perfume, and pharmaceutical industry is benzaldehyde, with the requirement that it must be free of toxic impurities
The catalytic materials used in oxidation and dehydrogenation of butane are Vanadium-based catalysts arethe among the materials thatbasic, haveand beenredox extensively studied for alkane very complex and it is clear that combination of acid, properties determines the
Summary
The last few years have seen a growing interest in cycloaddition reactions, such as Diels–Alder, followed by dehydrogenation to produce aromatic compounds in a novel fashion from diverse feedstocks, such as those that come from biomasses [1]. Reactions involved in the formation of benzaldehyde from butadiene and acrolein This represents an alternative method for benzaldehyde production, where the use of an ODH catalyst could make the direct conversion n-butane to benzaldehyde possible. These twonot compounds could bebut formed inacrolein, similar catalyst for this process should favor the formation only of butadiene, of amounts given the right balance of redox and acid sites of appropriate type and strength on the catalyst. The catalytic materials used in oxidation and dehydrogenation of butane are Vanadium-based catalysts arethe among the materials thatbasic, haveand beenredox extensively studied for alkane very complex and it is clear that combination of acid, properties determines the [17]. SiO2 , ZrO γ-Alamong commonly usedbeen in n-butane studies [18,19,20,21]
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