Extraction followed by heteroazeotropic distillation is considered to be a potentially energy-saving method for purifying acrylic acid. Based on our previous work, cyclopentyl methyl ether is an excellent solvent that can be used as extractive an agent as well as an entrainer. In this work, liquid-liquid equilibria (LLE) data of the quaternary system (water (1) + acrylic acid (2) + acetic acid (3) + cyclopentyl methyl ether (4)) were determined at T=(293.15, 303.15, and 313.15) K and p = 100.25 kPa. The reliability of the experimental data was evaluated using the Othmer-Tobias and Hand equations. The NRLT and UNIQUAC activity coefficient models were used to correlate the LLE data of the quaternary system. The UNIFAC-Dortmund model was used to predict the observed LLE data with a average root-mean-square deviation value of 3.41%. Additionally, the physical properties and extraction capabilities of cyclopentyl methyl ether, cyclohexane, and toluene were compared. (C) 2015 Elsevier B.V. All rights reserved.