Efficient biodiesel production from oleic acid using metal–organic framework encapsulated Zr-doped polyoxometalate nano-hybrids

According to the need of sustainable development, solid catalysts are critical materials for green biodiesel production. In this study, a hydrothermal method was used to develop a reusable and highly active Fe-BTC and UiO-66 metal–organic framework encapsulated Zr-doped polyoxometalate nano-hybrid catalysts (ZrSiW/Fe-BTC and ZrSiW/UiO-66) for the acid-catalyzed esterification of oleic acid with methanol. The structural and compositional characterization of the synthesized catalysts were characterized using various techniques such as Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), nitrogen adsorption–desorption, scanning electron microscopy (SEM), and thermogravimetric (TG) and temperature programmed desorption (NH(3)-TPD) analysis. The as-prepared ZrSiW/UiO-66 had excellent catalytic activity in the esterification of oleic acid with methanol, higher than that of ZrSiW/Fe-BTC catalyst, owing to the fact that ZrSiW/UiO-66 nano-hybrids have high acidity, large specific surface area and pore volumes, and relatively large average pore sizes. Furthermore, the reusability and stability of nano-hybrids were also evaluated, and it was found that the stability of ZrSiW/UiO-66 catalyst was better.