Predictive capability evaluation of RSM, ANFIS and ANN: A case of reduction of high free fatty acid of palm kernel oil via esterification process

Response surface methodology (RSM), adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) were tested in the modeling of acid pretreatment of palm kernel oil with a very high acid value (22 +/- 0.1 mg KOH/g oil). This was investigated considering methanol/oil molar ratio (1.3:1-3.8:1), catalyst loading (0.3-0.5 vol.%) and time (20-40 min) using Box Behnken design. The developed RSM, ANFIS and ANN models described the process with high accuracy (coefficient of determination, R-2>0.99 and average absolute deviation, AAD = 2.72-23.96%). RSM, RSM coupled with generic algorithm (GA), ANFIS-GA and ANN-GA were applied to optimize the process for best operating condition and ANN GA gave the minimum acid value (0.64 mg KOH/g) under the best optimal condition of methanol/oil molar ratio 3.4:1, catalyst loading 0.39 vol.% and time 24.06 min. Based on the statistical indices obtained, RSM performed the least, while ANN marginally outperformed ANFIS. GA proved to be superior to RSM in the optimization of the esterification process. (C) 2016 Elsevier Ltd. All rights reserved.