KIT-6 como catalisador na síntese de polióis: um estudo utilizando a Metodologia de Superfície de Resposta

Abstract

Growing demand for sustainable alternatives has driven the use of renewable materials in various industrial sectors. In this context, this study proposes an innovative route for the synthesis of biolubricants using oleic acid and trimethylolpropane (TMP) as raw materials and employing mesoporous silica KIT-6 as a heterogeneous catalyst. KIT-6 was functionalized with Zr and sulfate groups to enhance its catalytic activity. Initially, KIT-6 was synthesized using different molar ratios of Si and Zr (Si/Zr = 10, 15, and 20). FT-IR, SAXS, and XRD analyses confirmed the incorporation of zirconium and sulfate groups into the KIT-6 structure, which maintained its cubic mesoporous configuration. BET, SEM, and EDS analyses revealed the influence of Si/Zr ratio on the textural properties of the material, such as surface area, pore diameter, and elemental composition. To optimize the esterification reaction, the response surface methodology (RSM) was used, considering four key factors, with conversion, calculated through the acid value, as the response variable. The study showed that the most significant factors for improving the reaction were the oleic acid/TMP ratio, type of catalyst used, and amount of catalyst in the reaction medium. The final stage of the study involved reaction kinetics, monitoring of the acid value, FT-IR spectra, and ¹H NMR of aliquots collected at predetermined times. The results indicated that the reaction achieved a maximum conversion of approximately 87%, stabilizing after four hours. The catalyst stability was assessed in subsequent reactions, showing consistent performance over three cycles without significant loss of catalytic activity. Characterization of the produced biolubricant indicated suitable physicochemical properties, such as high kinematic viscosity, thermal stability, and resistance to oxidation, as well as good tribological performance compared to commercial lubricants. The data obtained demonstrated that KIT-6 modified with silicon and zirconium has great potential as a catalyst for esterification reactions in the synthesis of biolubricants, underscoring the importance of further studies to explore and enhance its applications.