Efficient Production of Biodiesel from Esterification of Lauric Acid Catalyzed by Ammonium and Silver Co-Doped Phosphotungstic Acid Embedded in a Zirconium Metal–Organic Framework Nanocomposite

A novel solid acid nanocatalyst (Ag 1 (NH 4 ) 2 PW 12 O 40 /UiO-66) comprising ammonium and silver co-doped H 3 PW 12 O 40 and zirconium-based metal-organic frameworks (UiO-66) was synthesized and characterized by Fourier transform infrared spectroscopy, N 2 adsorption/desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and ammonia temperature-programmed desorption. The catalytic activity was evaluated for the synthesis of biodiesel via esterification of lauric acid and methanol. The effect of the operating parameters including the molar ratio of lauric acid to methanol, catalyst amount, and reaction temperature and time on the lauric acid conversion was also investigated to obtain optimum reaction conditions. Also, the composite (Ag 1 (NH 4 ) 2 PW 12 O 40 /UiO-66) was recyclable and reused up to six cycles. Kinetics of the lauric acid esterification has been assumed to be of a pseudo-first order, and the results showed that the activation energy for the esterification process was found to be 35.2 kJ/mol.