A combined effect of reaction temperature, ethanol-to-oil molar ratio and catalyst concentration on biodiesel production by H3PMo12O40 (HPMo) supported on niobia from macaw palm oil (Acrocomia aculeata) with high free fatty acid content has been studied herein through the response surface methodology. A 2(3) face centered central composite design was employed in order to conduct the experimental design and results analysis. Optimum conditions were found to be at 210 degrees C reaction temperature, 90:1 ethanol-to-oil molar ratio and 20.0% catalyst concentration, rendering high-quality biodiesel (99.65% ester content, 4.90 mm(2)/s viscosity and low monoacylglycerol and diacylglycerol levels). Such high performance can be associated with the catalyst satisfactory features, as characterized by typical analyses such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), N-2 Adsorption-desorption and Surface acidity. Furthermore, the catalyst can be reused with no notable loss of catalytic activity until the second reaction cycle, thus maintaining an ester content higher than 94%. (C) 2017 Elsevier Ltd. All rights reserved.