Methyl methacrylate (MMA) is an important monomer

which is widely used for producing acrylic resins or polymer dispersions. The two-step selective oxidation process which selectively oxidizes isobutylene to MMA via methacrolein is regarded as a promising process for its high atomic efficiency. In the process

separation of MMA is a critical technique due to high methanol concentration in the reaction. Traditional distillation could not be used for separation of MMA from methanol because of azeotrope mixture. Double solvent extraction is a good alternative. The liquid-liquid equilibrium (LLE) data for MMA-methanol-hexane-water quaternary system were determined at 293.15 K and 303.15 K under atmospheric pressure. N-Hexane-water solvent system and cyclohexane-water solvent system were used for the MMA extraction from methanol. The activity coefficient model of universal quasi-chemical (UNIQUAC) was used to regress the LLE data of the investigated systems. The parameters of the UNIQUAC model were obtained.