Construction of the novel PMA@Bi-MOF catalyst for effective fatty acid esterification

Abstract

A novel Bi-based metal-organic framework impregnated phosphomolybdic acid (PMA@Bi-MOF) catalyst has been fabricated via a simple hydrothermal procedure, and successfully applied in the preparation of biodiesel using oleic acid (OA) as the raw material. The PMA@Bi-MOF composites were exhaustively characterized with the help of FTIR, XRD, TPD-NH3, SEM-EDX, N2-physisorption, TGA, and XPS analyses. Experimental findings showed that the PMA@Bi-BTC exhibited a higher activity than that of PMA@Bi-BDC and Bi-BTC, attributed to its textural property, the presence of more acid sites with higher strength, and synergistic catalytic effects between PMA and Bi-BTC. The optimum conditions for esterification of OA, with a conversion of up to 92.5%, were found to be a molar ratio of methanol to OA of 20:1 and 0.15g PMA@Bi-BTC catalyst at 160 °C in 3 h. Meanwhile, reused studies indicated that the OA conversion reached more than 80% after seven reaction cycles. Furthermore, the activation energy of esterification catalyzed by PMA@Bi-BTC was also calculated as 54.8 kJ/mol. It is expected that our study provides an efficient route to biofuel production involving polyoxometalates/MOF synergistic catalysts.