Synthesis, Characterization and Catalytic Performance of a Novel Picolinic Acid-12-Molybdophosphoric Acid Hybrid Catalyst

A novel 12-molybdophosphoric acid (HPM)-based complex (H2PI)2(H3O)[PMo12O40][Mo2O5(H2O)2(PI)2]·11H2O (PI-HPM) was prepared by modification with picolinic acid (HPI) and characterized by the methods of Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), X-ray powder and single crystal diffraction. The complex retained the classical Keggin structure of bulk HPM, there were some strong hydrogen bonds existing between the [PMo12O40]3- polyanion, the [Mo2O5(H2O)2(PI)2] coordination moiety, the protonated HPI and the lattice water molecules. Then PI-HPM was employed as heterogeneous catalyst for esterification reaction to evaluate its acid-catalytic activity. The complex exhibited high activity and good durability in reaction mixtures, indicating that it was a promising heterogeneous acid catalyst for esterification that including the conversion of oleic acid to oleates.