Heterogeneous Mo/W/Zn–SiO 2 based catalysts in nopol (2-(6,6-dimethyl-2-bicyclo[3.1.1]hept-2-enyl)ethanol) synthesis

Nopol (2-(6,6-dimethyl-2-bicyclo[3.1.1]hept-2-enyl)ethanol) is an important fragrant compound, which synthesis is widely studied. Possibility of the use of heterogeneous catalysts instead of commonly used zinc (II) chloride can offer environmentally friendly process with possible catalyst reuse and avoiding wastewater production. Several metal modified SiO 2 materials (mostly molybdenum, tungsten and zinc) were prepared and tested in nopol synthesis. Molybdenum and zinc modified material (with 25 wt% of MoO 3 resp. ZnO loading) showed to possess a high activity in nopol synthesis accompanied by high selectivity of nopol formation. Under optimal reaction conditions (solvent benzonitrile, 80 °C, molar ratio β -pinene:paraformaldehyde = 1:2, 24 h) following results were observed: using catalyst 25 wt% MoO 3 –SiO 2 (20 wt% to β -pinene) 77% β -pinene conversion and 98.7% selectivity of nopol formation was obtained (24 h), using catalyst 25 wt% ZnO–SiO 2 (40 wt% to β -pinene) 72% β -pinene conversion and 96.3% selectivity of nopol formation was obtained (24 h). Molybdenum or zinc modified SiO 2 can be successfully used in nopol synthesis from β -pinene and paraformaldehyde as heterogeneous catalysts, after material regeneration, the catalyst reuse is possible.