Natural source turpentine is an available source of α-pinene oxide. This compound’s value is especially given by the possibility of producing important compounds campholenic aldehyde and trans-carveol. In this work, we would like to present the usage of MoO₃-modified zeolite BETA in α-pinene oxide isomerization concerning campholenic aldehyde and trans-carveol formation using a wide range of solvents. Catalyst calcination temperature also influenced the reaction course (selectivity to desired compounds and reaction rate). MoO₃-zeolite BETA was prepared by the wet impregnation method and characterized by different techniques. The use of polar aprotic solvents had the most positive effect on the reaction course. Solvent basicity and polarity considerably influenced the reaction rate and selectivity to particular products. The combination of high basicity and the high polarity was the most suitable for the studied reaction from the reaction rate point of view. Selectivity to campholenic aldehyde and trans-carveol was the most influenced by solvent basicity. Higher solvent basicity caused the preferential formation of trans–carveol, influence on selectivity to campholenic aldehyde formation was the opposite. The described catalyst may be used for α-pinene oxide rearrangement to both desired products dependently on the used solvent. Molybdenum offers an exciting alternative for previously described modifications of zeolites for this reaction.

Acid-treated montmorillonites (MMT) were used as catalysts of carvone isomerization to carvacrol. Mineral acids—sulfuric, hydrochloric, nitric acids and organic acids (acetic and chloroacetic)—were used for the acid treatment. Prepared materials were characterized by available characterization methods, namely XRD, EA, TPD, TPO, UV-Vis, laser light scattering and nitrogen physisorption. The structure of montmorillonite remained intact after treatment. However, TPD proved the increase of acidity of acid-treated materials comparing pure montmorillonite. All materials were tested in the isomerization of carvone, producing carvacrol as the desired product. The initial reaction rate increased using the materials in the row MMT-COOH < MMT-HNO₃ < MMT-ClCOOH < MMT-H₂SO₄ < MMT-HCl, which is in accordance with the pKa of acids used for the treatment. The number of weak acid sites strongly influenced the selectivity to carvacrol. The optimal solvent for the reaction was toluene. Total conversion of carvone and the selectivity to carvacrol 95.5% was achieved within 24 h under 80 °C, with toluene as solvent and montmorillonite treated by chloroacetic acid as catalyst. The catalyst may be reused after calcination with only a low loss of activity.