Biomedical Inorganic Polymers

12‐tungstophosphoric acid, polyoxometalate with Keggin structure, and γ‐Al2O3 were synthesized. Loading of 12‐tungstophosphoric acid (HPW) on γ‐Al2O3 was performed by the post‐impregnation method. The catalysts were characterized by XRD, SEM, FTIR, BET, and DRS techniques. According to the pertinent observation, using the post‐impregnation method promises the stability of polyoxometalate Keggin structure after loading on γ‐Al2O3 support. The stability of 20 %HPW/Al2O3 was also confirmed by a leaching test. Textural characterization demonstrates that HPW on the γ‐Al2O3 had a much larger surface area as compared with the pure HPW. The 20 %HPW/Al2O3 exhibited roughly high activity toward an esterification reaction. The influence of various reaction parameters (% loading HPW on support, reaction temperature, reaction time, catalyst weight, and acid/alcohol molar ratio) on the catalytic performance was studied. The efficiency of catalytic activity for six cycles remains approximately constant, which confirms the enhanced recovery and recycling of the catalyst. The kinetics of the esterification reaction and the kinetic parameters such as rate constants and activation energy were determined (25.37 kJ/mol).

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