Abstract
Abstract MIL-125(Ti) metal–organic framework-derived nanoporous titanium dioxide–heteropoly acid (PW–TiO2) have been synthesized by a facile hydrothermal approach and subsequent calcination, and the PW–TiO2 catalysts were investigated using various characterization technologies including FTIR, XRD, SEM, TEM, N2-physisorption, and NH3-TPD. Further, we investigated the use of PW–TiO2 composites as heterogeneous acid catalysts for the catalytic esterification of oleic acid. Among all series of catalysts, the calcined PW–TiO2 at a temperature of 350°C showed excellent activity with a high conversion of 90.5% at 160°C for 4 h. More importantly, the catalyst could be simply separated via centrifugation and reused for six cycles and shows a relatively high conversion of 74.8%.
Highlights
MIL-125(Ti) metal–organic framework-derived nanoporous titanium dioxide–heteropoly acid (PW–TiO2) have been synthesized by a facile hydrothermal approach and subsequent calcination, and the PW–TiO2 catalysts were investigated using various characterization technologies including FTIR, XRD, scanning electron microscope (SEM), transmission electron microscope (TEM), N2-physisorption, and NH3-TPD
In a typical synthesis procedure, H2-BDC (1.0 g) and tungstophosphoric acid (0.6 g) were mixed in a 50 mL beaker, and a mixed solution containing 18 mL of DMF and 2 mL of anhydrous methanol was added under stirring at room temperature for 10 min, followed by addition of 0.52 mL of titanium tetraisopropanolate; the resultant mixture was stirred for 30 min to ensure uniformity
The typical peak at around 6.3° can be related to MIL-125(Ti) frameworks [33]; it was decreasing somewhat with the increase in the calcination temperature, meaning that the transformation of MIL-125(Ti) into titanium dioxide aggregates
Summary
Abstract: MIL-125(Ti) metal–organic framework-derived nanoporous titanium dioxide–heteropoly acid (PW–TiO2) have been synthesized by a facile hydrothermal approach and subsequent calcination, and the PW–TiO2 catalysts were investigated using various characterization technologies including FTIR, XRD, SEM, TEM, N2-physisorption, and NH3-TPD. Homogeneous catalysts catalyzing esterification or transesterification takes shorter reaction times with a high yield, but it is related to problems like the corrosion of equipment, the difficulty in separation, and generation of effluents [7]. In this regard, heterogeneous catalysts offer several important advantages in terms of its granting effectiveness and stability in liquids, easy recovery, and excellent thermal [8,9]. Heterogeneous base-catalyzed transesterification has been widely studied since they offer a fast reaction rate It is impaired by the amounts of FFAs and water from low-cost raw oil, due to saponification and catalyst deactivation [10].
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