Transesterification of waste cooking oil with heterogeneous tungstophosphoric acid (TPA) catalyst and methanol was investigated. Response Surface Methodology (RSM) and Artificial Neural Network (ANN) were employed to study the relationships of process variables on free fatty acid conversion and for predicting the optimal conditions. The highest conversion was 88.6% at optimum reaction conditions of 65 °C reaction temperature, 70:1 molar ratio of methanol to oil, 10 %wt catalyst amount, and 14 h reaction time. The RSM and ANN could accurately predict the experimental results, with R2 = 0.9987 and R2= 0.985, respectively. The TPA catalyst exhibited good potential as a stable and active catalyst over four time’s reusability. The reaction followed first-order kinetics and the calculated activation energy was Ea= 53.99 kJ/mol while the pre-exponential factor was A= 2.9x107 min-1. According to the biodiesel characterization results (ASTM D6751) the product of this study has high potential for using as a substitute for conventional catalyst in biodiesel production
