Isomerization of α- and β-pinene epoxides over dendritic ZSM-5 zeolites

The selective isomerization of α- and β-pinene epoxides was investigated using dendritic ZSM-5 zeolite catalystsunder mild reaction conditions using ethyl acetate as solvent at moderate temperatures (40–70 ◦C). The highlyinterconnected dendritic meso-macroporous structure and suitable Brønsted-to-Lewis acid sites balance facilitatedefficient epoxide ring opening and rearrangement pathways without the need for additional metal functionalizationas active phases. Likewise, the dendritic samples exhibited a superior catalytic activity than areference hierarchical ZSM-5 material. α-Pinene epoxide reaction yielded mainly campholenic aldehyde andcarveol derivatives, while β-pinene epoxide rearranged to myrtanal, perillyl alcohol, and myrtenol. The metalfreenature of the catalyst offers advantages in terms of sustainability and product purity, making it a promisingalternative for fine chemical synthesis from renewable terpene resources. Green metrics were calculated forthe isomerization of both epoxides, such as atom economy, yield, stoichiometric factor, material recoveryparameter, and reaction mass efficiency, demonstrating the green credentials of the process. The kinetic study ofα-pinene epoxide into campholenic aldehyde provided an activation energy of 75.6 kJ⋅mol􀀀 1. For β-pineneepoxide, the cis- and trans-myrtanal isomers dominate, exhibiting activation energies of 62.0 and 64.4 kJ⋅mol􀀀 1,respectively. The adsorption of cis- and trans-myrtanal onto the catalyst surface significantly influenced theproduct distribution of the transformation of β-pinene epoxide over the dendritic zeolite catalyst.