Physiochemical characterization and support interaction of alumina-supported heteropolyacid catalyst for biodiesel production

12-Tungstophosphoric acid (TPA)-supported -Al2O3 catalysts were synthesized with varying TPA loadings. Catalysts characteristics were determined using Brunauer-Emmett-Teller surface area analysis, thermogravimetric analyses, X-ray diffraction, Raman, pyridine-adsorbed Fourier-transform infrared spectroscopy, and C-13 hpdec (high-power H-1 decoupling) nuclear magnetic resonance, whereas surface morphology was studied using scanning electron microscope and transmission electron microscopy analyses. Surface defects were found in the catalyst with higher TPA loadings (55-65wt.%). The presence of WOx was observed at higher loadings and later agglomerated into tungsten oxide crystals. The TPA impregnated catalysts were investigated for biodiesel synthesis from canola oil. The reaction was found to be independent of mass transfer limitation. The activation energy was 33.6kJmol(-1), and pre-exponential factor was 7.3*10(-2)min(-1). The turnover frequency for the supported catalysts was found in the range of 9.7*10(-4)-8.8*10(-2)min(-1). A conversion of 94.9 +/- 2.3% was obtained under the optimized conditions, that is, 10wt.% of the catalyst loading, 17.5 methanol to oil molar ratio, 4MPa, and at 200 degrees C in 10hr.