Non-edible crude karanj (Pongamia pinnata) oil (CKO) with high free fatty acid (FFA) content was used as effective renewable feedstock for fatty acid methyl ester (FAME) production. Calcium feldspar clay, a rare compositional variety of plagioclase clay, a low cost, abundant earth resource, containing over 90% CaO and belonging to the class of anorthite clay was used as heterogeneous catalyst in direct conversion of high FFA crude karanj oil to fatty acid methyl esters. The efficiency of the catalyst was made possible by the structural rearrangement of the mixed metal oxides' content of the catalyst at prolonged high temperatures, a behaviour characteristic of glass transitions and properties of amorphous phases of plagioclase feldspar, and thus was transformed into solid acid particles such as acidic mesoporous aluminium silicate mixed oxides. Optimum FAME yield of 98.97% was obtained at 4 h reaction time, 6 wt% catalyst loading, 9:1 methanol to CKO molar ratio and at methanol reflux temperature. More than 90% catalyst was recovered after four runs which still exhibited strong activity after further calcination at 500°C for 1 h after each run. From the result of transesterification, non-edible, high FFA crude CKO is a potential renewable feedstock for the production of FAME using thermally treated, low cost, anorthite clay-derived catalyst.
Key words: Anorthite clay, fatty acid methyl ester, crude karanj oil, transesterification.
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