Deboronation and Alumination of SCM-10 Zeolites for Efficient α-Pinene Isomerization

The weak acidity of borosilicate zeolites limits their catalytic applications. However, the labile framework boron atoms offer an opportunity to incorporate aluminum post-synthetically to tailor acidity. Herein, aluminosilicate SCM-10 zeolites (Al-SCM-10), featuring an SFE-type framework with 1D 12-membered ring channels, were prepared through boron-to-aluminum substitution of borosilicate SCM-10 using aqueous Al(NO₃)₃ solutions. The influences of Al(NO₃)₃ concentration, treatment temperature, and parent composition on framework Al incorporation were investigated. A synergistic combination of moderate Al(NO₃)₃ concentration (1.0 M) and temperature (150°C) was found to favor framework Al incorporation while preserving microporosity. In contrast, overly dilute solutions and/or elevated temperatures led to partial pore blockage, whereas low temperatures or excessive Al(NO₃)₃ concentrations resulted in inefficient Al incorporation. The resulting Al-SCM-10 zeolites exhibit tunable Si/Al molar ratios (28-79), moderate acid strength, and Lewis-acid-rich character. In α-pinene isomerization, the optimized Al-SCM-10 catalyst achieves 97.8% conversion and a combined yield of 77.2% toward high-value products camphene and limonene, outperforming conventional zeolite catalysts under identical reaction conditions. These results demonstrate that post-synthetic aluminum incorporation is an effective strategy for activating SCM-10 for selective biomass-derived transformations.