Preparation and Characterization of Tungsten-substituted Molybdophosphoric Acids and Catalytic Cyclodehydration of 1,4-Butanediol to Tetrahydrofuran

A series of tungsten-substituted molybdophosphoric acids (H3PMo12-nWnO40·xH2O) were synthesized and characterized by inductive coupled plasma atomic emission spectroscopy (ICPAES), thermal gravimetry and differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and FTIR pyridine adsorption. The as-prepared heteropoly acids have a Keggin type structure. The synthesis of tetrahydrofuran by reactive distillation and cyclodehydration of 1,4-butanediol was studied using the tungsten-substituted molybdophosphoric acids as catalysts. The results of catalytic test indicated that the catalytic activity increased with the increase in the substitution number (n) of tungsten atom in H3PMo12-nWnO40·xH2O and was constant as the substitution number (n) was more than 8. The catalytic activity increased with the increase in the catalyst loading and the selectivity of tetrahydrofuran was nearly 100%.