Synthesis of sulphur-modified bifunctional hydrotalcites and study of their surface characteristics by inverse gas chromatography

Abstract

In this study, various sulphur-modified hydrotalcite catalysts were prepared, and the influence of calcination temperature on their acid–base properties was investigated. Structural characterization of the catalysts was studied using X-ray powder diffraction, scanning electron microscopy, N₂ physisorption, elemental analysis and Fourier transform infrared spectroscopy. The structural characterization indicated that the layer structure of all catalysts was retained but the specific surface areas were enlarged. Inverse gas chromatography was carried out to quantitatively determine the catalysts' acid–base properties by calculating the thermodynamic parameters, including dispersive surface free energy, adsorption free energy, adsorption enthalpy, and acid–base interaction constants. The results showed that the strength and content of acidic and alkaline sites were enhanced with increasing calcination temperature. Moreover, several typical aldol condensation reactions were selected to study the catalytic activity of the developed catalysts. The results showed that the sulphur-modified hydrotalcite catalysts possess high activity and good regenerability for typical aldol condensation reactions.