Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde catalyzed by sulfated zirconia

The present work describes the novel application of sulfated zirconia (SZ) solid acid catalysts for the synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. SZ catalysts with different percentages of sulfur loadings have been synthesized and characterized using various physico-chemical techniques like PXRD, FT-IR, surface area analysis and NH3–TPD studies. The influences of various reaction parameters such as sulfur loading, reaction temperature, molar ratio of reactants, reaction time, solvent effect and reusability of the catalyst have been investigated. SZ catalyst synthesized by impregnation of 2N sulfuric acid solution over Zr(OH)4 was found to be a highly selective catalyst for β-pinene conversion (>99%) with ∼99% selectivity to nopol. The catalyst could be reused up to five cycles with minor loss in catalytic activity for β-pinene conversion, while the nopol selectivity remains unaffected.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (17 K)Download as PowerPoint slideResearch highlights▶ Application of sulfated zirconia as an efficient solid acid catalyst. ▶ Synthesis of nopol via Prins condensation of β-pinene and paraformaldehyde. ▶ SZ-2NCalcn catalyst resulted in 99% conversion of β-pinene with ∼99% selectivity. ▶ Catalyst can be recycled with little loss in activity up to five cycles.