Biomass toward fine chemical products: Oxidation of a-pinene oversieves nanostructured modified with vanadium

CÁNEPA ANALIA; CHANQUIA C; VIRGINIA VASCHETTI; EIMER GRISELDA; CASUSCELLI S

JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 404 p. 65 - 73

1381-1169

Vanadium-containing molecular sieves (V-M(x)) were synthetized and applied as heterogeneous cata-lysts for the liquid phase oxidation of -pinene with hydrogen peroxide at 70◦C. It has been found thatthe vanadium content in V-M(x) materials affected the conversion of -pinene and product distribution.The turnover numbers increased strongly with the decreasing of V content probably caused by a high Vdispersion. The major products were verbenone, trans-sobrerol and campholenic aldehyde. The acid?baseproperties of V-M(x) affected the distribution of products formed via the isomerization of -pinene oxideover Lewis acid sites to campholenic aldehyde while Brønsted acid sites brought about the formationof 1,2 pinanediol and trans-sobrerol by hydrolysis and by the opening of oxirane ring. The increase inV content in V-M(x) led to the increase in campholenic aldehyde, 1,2 pinanediol, trans- sobrerol andover oxidation products. Moreover, the effect of several solvents on the reaction oxidation was studied.The results showed that the highest -pinene conversions are obtained in the following order: acetoni-trile > ethanol > isoamyl alcohol > methyl ethyl ketone. Thus, using aprotic solvents, the catalytic activitywas increased and the formation of alkyl glycol ethers as by-product was not observed.The catalysts were characterized by ICP-OES, N2adsorption,UV-Vis-DR, FT-IR, Raman and FT-IR with pyridine adsorption. Theresults confirmed that the V-M(x) samples possessed regular andstable structure with a high specific surface. The V atoms weresuccessfully introduced mainly as tetrahedral coordinated isolatedspecies into the MCM-41 framework, which would be located eitherinside the wall or on the surface of the mesoporous cannel.Leaching experiments demonstrated that very small amountsof V species were leached from the solid matrix only during thefirst and second catalytic cycle as not active species. Acetonitrileand H2O2were involved in the lixiviation reaction forming inac-tive soluble V species, while the isolated V+cations were stableactive sites for the oxidation of -pinene. In addition, the catalystalso showed stability in its structure. Finally, the recycling experi-ments showed that the most active catalyst can be used repeatedlywithout activity and selectivity loss during several cycles.