Synthesis of a novel bifunctional mesoporous Ti-SBA-15-SO3H catalyst and studies on their enhanced performance and kinetic modeling of lactic acid esterification reaction with n-butanol

Abstract

Abstract In the present study, the mesoporous Ti-SBA-15-SO3H catalyst is synthesized by using the sol-gel method. Further, these materials have been characterized by different advanced analytical techniques such as Low angle X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetry/Differential thermal analysis (TG/DTA), N2 adsorption/desorption studies, Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH3-TPD) and Lactic acid esterification catalytic activity studies. The Ti-SBA-15-SO3H catalyst is found to have a surface area of 457 m2/g, a pore volume of 0.12 cm3/g, a pore diameter of 3.16 nm, and a high acid density of 1.72 mmol/g. The optimum reaction conditions for lactic acid esterification with n-butanol are found to be a 1: 4 M ratio, 3 wt-% catalysts, 115 °C temperature, and 120 min reaction time to obtain 72% conversion. Further, the reusability tests reveal that the spent catalyst can be used for five successive runs without the loss of considerable activity. The pseudo-homogeneous model was able to describe the kinetics of this esterification with negligible error. The activation energy and equilibrium rate constant for Ti-SBA-15-SO3H is found to be Ea = 0.063 KJ/mol and K = 5.019 lit/mol min, respectively, to catalyze the esterification of lactic acid with n-butanol. A plausible mechanism for the catalytic activity is proposed.