Mesoporous Zr-SBA-15 as a green solid acid catalyst for the Prins reaction

Abstract

Mesoporous Zr-SBA-15 platelets were prepared with different pore dimensions from 4 to 8 nm by the simple procedure of varying the amount of water in the synthesis gel. Narrow pore size distributions were obtained for water–tetraethoxysilane ratios between 208 and 639, but samples formed using a lower ratio of 100 had a broad pore size distribution. Thermogravimetric measurements showed that the interaction between the Pluronic template and the inorganic framework was affected by the amount of water in the synthesis gel. More zirconium was incorporated into the silica framework when the synthesis was conducted in a more dilute system. The Zr-SBA-15 obtained from this synthesis forms platelets with relatively short channels. The catalytic activity was tested for C–C-coupling (Prins reaction). The terpene alcohol Nopol, the product of an intermolecular Prins reaction between β-pinene and paraformaldehyde, could be obtained with excellent selectivity. The mesoporous structure of the catalyst together with the presence of zirconium in the silica framework, which confers strong Lewis acidity as well as weak Brønsted acidic sites, are essential for the activity and selectivity of the reaction.