Evolution of Brönsted and Lewis acidity of single and mixed pillared bentonite

The surface acidity of different pillared clay, zirconium-, aluminium- and mixed zirconium–aluminium-pillared bentonite was determined by Fourier transform infrared spectroscopy technique using N-butylamine as probe molecule. The spectra obtained showed well resolved absorption bands for Lewis and Brönsted acid sites in the clay catalysts. In order to understand the role of acid sites present on clay catalysts, synthesis of 2,2-dimethyl-1,3-dioxolane by acetalyzation of acetone with ethylene glycol under autogenous pressure and without solvent has been studied. The Brönsted and Lewis acidity data obtained by FT-IR study for modified bentonite correlated well with the catalytic activity in the synthesis of 2,2-dimethyl-1,3-dioxolane reaction. Among the modified clay catalysts, Zr90–Al10-PILC bentonite catalysts showed good activity and aluminium rich PILC showed negligible activity in the acetalyzation reaction. This inactivity is attributed to the absence of Brönsted acidity.

► We study by IR spectroscopy the acidity of pillared clay.
► Aluminium pillared clay exhibited only Lewis acidity.
► Zirconium pillared clay exhibited both Lewis and Brönsted acidity.
► Adding aluminium in the zirconium solution leads to an enhancement of the acidity.
► Samples are used as catalyst in the reaction of 1,3-dioxolane synthesis.