Preparation of porous sulfated zirconia with deep eutectic solvents for improved catalytic efficiency in the synthesis of biodegradable alkyl glucosides

Abstract

In this study, a deep eutectic solvent (DES) system, comprising choline chloride and urea, was employed to synthesize sulfated zirconia (SZ) solid acid catalysts. The characteristics and efficacy of the SZ catalysts synthesized using this DES system were meticulously evaluated using a suite of analytical techniques, including nitrogen sorption, X-ray diffraction (XRD), pyridine adsorption infrared spectroscopy (Py-IR), X-ray photoelectron spectroscopy (XPS), and ammonia temperature-programmed desorption (NH3-TPD). The research also focused on analyzing the distinctive role and characteristics of the DES in the preparation of SZ. When compared with conventional aqueous phase precipitation methods, the SZ catalysts synthesized in the DES environment exhibited enhanced properties, such as an increased specific surface area, a higher density of acidic sites, and a larger proportion of potent acid centers. These improvements led to augmented catalytic activity in the reaction between alkyl alcohols and glucose. Moreover, the SZ catalysts prepared with DES demonstrated superior reaction stability and reusability, which can be attributed to the well-dispersed strong acid centers. The study uncovered that the components of the DES significantly contribute as microporous templating agents during the formation of SZ, assisting in the stabilization of the defect sites in the zirconia precursor. These components eventually evolved into prominently exposed surface strong acid centers during the stages of acidification and calcination, enhancing mass transfer efficiency and the acidic catalytic properties of the catalysts.