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 catalysts
under mild reaction conditions using ethyl acetate as solvent at moderate temperatures (40–70 ◦C). The highly
interconnected dendritic meso-macroporous structure and suitable Brønsted-to-Lewis acid sites balance facilitated
efficient epoxide ring opening and rearrangement pathways without the need for additional metal functionalization
as active phases. Likewise, the dendritic samples exhibited a superior catalytic activity than a
reference hierarchical ZSM-5 material. α-Pinene epoxide reaction yielded mainly campholenic aldehyde and
carveol derivatives, while β-pinene epoxide rearranged to myrtanal, perillyl alcohol, and myrtenol. The metalfree
nature of the catalyst offers advantages in terms of sustainability and product purity, making it a promising
alternative for fine chemical synthesis from renewable terpene resources. Green metrics were calculated for
the isomerization of both epoxides, such as atom economy, yield, stoichiometric factor, material recovery
parameter, and reaction mass efficiency, demonstrating the green credentials of the process. The kinetic study of
α-pinene epoxide into campholenic aldehyde provided an activation energy of 75.6 kJ⋅mol􀀀 1. For β-pinene
epoxide, 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 the
product distribution of the transformation of β-pinene epoxide over the dendritic zeolite catalyst.