Synthesis and characterization of niobium modified montmorillonite and its use in the acid-catalyzed synthesis of β-hydroxyethers

Montmorillonite K10 was ion-exchanged with polyhydroxyniobium obtained from niobium pentachloride by hydrolysis. This modified clay was characterized by X-ray diffraction, thermogravimetric analysis, inductively coupled plasma emission (ICP-OES) and nitrogen adsorption/desorption. The obtained material was used in the alcoholysis of epoxidized methyl oleate with methanol, leading to β-hydroxyethers. The reaction with ion-exchanged montmorillonite (Nb-Mont) was four times faster at 60 °C and three times faster under reflux than the one using the original clay. This proves the increase of Brønsted acidity when polyhydroxyniobium is present. The Nb-Mont was also calcined at 300, 500 and 900 °C to obtain the Nb-pillared montmorillonite. However, the activity of the calcined Nb-Mont decreased with increasing calcination temperature. On the other hand, calcined montmorillonite maintained its basal distance, even after treatment at 900 °C.