Isomerization of α- and β- pinene epoxides over Fe or Cu supported MCM-41 and SBA-15 materials

Abstract

Fe and Cu based heterogeneous catalysts were evaluated in the isomerization reaction of α- and β-pinene epoxides. The metals were incorporated on SBA-15 and MCM-41 using incipient wetness impregnation procedure and the materials were characterized by XRD, Raman spectroscopy, BET analysis, NH3-TPD, TEM and XPS. 1.4/Fe-MCM-41 was the catalyst with the highest TON value (364) and α-pinene epoxide conversion (73%) with a campholenic aldehyde selectivity of 59%, while from β-pinene epoxide 1.4/Fe-SBA-15 was the material with the highest TON (299) and selectivity (100%) to myrtanal with a substrate conversion of 60%. Cu based materials presented lowest TON value for the rearrangement of β-pinene epoxide than using α-pinene epoxide as substrate. Besides, it was elucidated that the formation of campholenic aldehyde and myrtanal is function of the presence of metal oxides, mean particle diameter and the strength of acidity; moreover, the most active catalysts did not present leaching under the reaction conditions. 1.4/Fe-MCM-41 can be used until five times without loss of catalytic activity with α pinene epoxide. Based on the characterization and different products synthetized, a reaction mechanism for the rearrangement reaction of α-pinene epoxide is proposed. This is the first report of Cu heterogenized on mesoporous materials for the isomerization reaction of monoterpenes epoxides.