Alkali salts of heteropoly tungstates: Efficient catalysts for the synthesis of biodiesel from edible and non-edible oils

摘要

Alkali salts of tungsten based heteropoly acids with different central atom such as P, Si and Co were prepared and evaluated for transesterification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst of sodium salt of tungstic acid with Co as central atom(Na5Co W12O40) showed optimum activity towards transesterification compared with other heteropoly tungstates.The catalysts activities were correlated with the observed physico-chemical characteristics derived from FT-infrared(FT-IR), X-ray diffraction(XRD), temperature-programmed desorption of ammonia(NH3-TPD) and carbon dioxide(CO2-TPD). The Na5 Co W12O40catalyst exhibiting high activity even at 65°C is due to the presence of strong acidic as well as basic sites. The disclosed catalyst is tolerable towards water and free fatty acids present in the oils. The influence of catalyst loading, reaction time and reaction temperature is studied to optimize the reaction parameters.