Polyvanadate-exchanged hydrotalcites as catalysts for selective oxidation of cyclohexene with molecular oxygen

Abstract

Catalytic activity of polyvanadate-exchanged Mg,AI-, Zn,AI-, and Zn, Crhydrotaleites in the selective oxidation of cyelohexene with dioxygen has been investigated and discussed with reference to the composition of the bmcite layer, type of the intercalated vanadate anion, vanadium loading and distribution of reaction products.

Highlights on the Catalytic Properties of Polyoxometalate-Intercalated Layered Double Hydroxides: A Review

“…It presented a lack of activity, which was probably due to the small interlayer distance that made the catalytic sites inaccessible. A considerable amount of epoxide was still observed in this case, which indicated the presence of decavanadate group in the interlamellar space [40]. Recently, Nejati et al [59] obtained ZnFe-VO 4 -LDH ( Figure 7), which was used as an efficient electrocatalyst for water oxidation in alkali solution.…”

“…Bahranowski et al [40] have prepared different decavanadate-exchanged hydrotalcite-like compounds that were catalytically active in the selective oxidation of cyclohexene with dioxygen. Their activities mostly depended on the composition of the brucite layers, and decreased in the order MgAl > ZnAl > ZnCr [40]. The lowering of the M(II)/M(III) ratio in the brucite layer allowed for an increased loading of decavanadate anions, which eventually led to higher activity.…”

Allylic Oxidation of Cyclohexene and Indene by cis-[RuIV(bpy)2(py)(O)]2+

“…Similar results have been found for model systems based on metalloporphyrins of Fe, Mn, and Cr with iodosylbenzene as the source of the oxidative equivalents. Cyclohexene is also oxidized by high oxidation state complexes of Cu, Mo, V, and Ti . Metalloporphyrins have been used as catalysts for the radical autoxidation of cyclohexene by O 2 giving 2-cyclohexen-1-one as the primary product, but typically after long induction periods. 9a-c Tabushi and co-workers showed that the autoxidation of cyclohexene catalyzed by manganese tetraphenylporphyrin chloride (Mn III TPPCl) can be significantly promoted by the presence of reducing agents. 9d,e Mn III TPPCl efficiently catalyzes the autoxidation of cyclohexene to 2-cyclohexen-1-one but in the presence of NaBH 4 or H 2 and colloidal platinum, the primary products are cyclohexanol and cyclohexene oxide, respectively.…”

An FT-IR study of the adsorption of isopropanol on calcined layered double hydroxides containing isopolymolybdate

“…These mixed oxides show a larger surface area development than those prepared following conventional methods, and are active as catalysts in selective oxidation processes. It has been reported [16] that solids obtained upon calcination of decavanadate intercalated hydrotalcites are more active in propane dehydrogenation than those formed by pyrovanadate.…”