12-Tungstophosphoric acid anchored to SBA-15: An efficient, environmentally benign reusable catalysts for biodiesel production by esterification of free fatty acids

12-Tungstophosphoric acid anchored to SBA-15 was synthesized and characterized by various physico-chemical techniques such as TGA, FT-IR, DRS, XRD, N2 adsorption–desorption, solid state NMR (31P and 29Si), SEM and TEM. The use of synthesized catalyst was explored for biodiesel production by esterification of free fatty acid, oleic acid with methanol. Influence of various reaction parameters (such as catalyst concentration, acid/alcohol molar ratio and reaction temperature) on catalytic performance was studied. The catalyst shows high activity in terms of conversion of oleic acid as well as high turnover frequency of 9.3 min−1. It also shows potential of being used as recyclable catalyst material after simple regeneration. Kinetic investigation reveals that the esterification reaction of oleic acid with methanol follows a first order dependency on the concentration of the oleic acid and the catalyst. The influence of temperature on rate constant was also studied and the activation energy was found to be 44.6 kJ mol−1. As an application, preliminary study was carried out for biodiesel production from waste cooking oil, as feedstock without any pre-treatment, with methanol. Studies show that the catalyst can be used for biodiesel production from waste cooking oil under mild conditions.

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► Synthesis and characterization of 12-tungstophosphoric acid anchored to SBA-15.
► Catalytic activity for biodiesel production by esterification of free fatty acid.
► Excellent activity in terms of high conversion of oleic acid, high TOF, 9.3 min−1.
► Catalyst can be reused up to four cycles without any significant loss in activity.
► Environmentally benign reusable catalyst for biodiesel production.