Influence of Water on the Recovery of Lube Oil Dewaxing Solvent Using P84 Polyimide Membrane: A Combination of Experiment and Molecular Simulation

Abstract Water in lube oil solution will affect the result of dewaxing solvent recovery by membrane. Three factors that affect the permeation of solvent molecules through P84 membrane and the interaction between water and dewaxing solvent were studied by combination of density functional theory (DFT) method, molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulation. The results suggested that there is a stronger interaction between water and butanone than interactions between other molecules in dewaxing solvent. With the increase of water content in dewaxing solvent, the diffusion rate of dewaxing solvent to the membrane surface decreased, the number of butanone molecules adsorbed on the membrane surface increased slightly. However, both the total number of dewaxing solvent adsorbed and the diffusion rate of that in the membrane material decreased. In other words, the strong interaction between water and butanone reduces the penetration rate of dewaxing solvent through the membrane, which explains the experimental results. These results will be helpful for understanding of the membrane separation process deeply, and designing the membrane separation process.