Combinatorial screening of ionic liquid extractant for removal of methanol from methylal

•A combinatorial screening approach is proposed as an IL screening tool.•The approach combines quantum chemical calculation and molecular dynamics simulation.•[EMIM][Ac] is successfully screened for removal of methanol from methylal through this approach.•The separation mechanism of the IL is clarified at the molecular scale. A combinatorial screening approach combining quantum chemical (QC) calculation and molecular dynamics (MD) simulation was presented for the selection of ionic liquid (IL) extractant to remove methanol from methylal. The thermodynamic properties of the distributional coefficient and selectivity were calculated by COSMO-RS based on QC calculation to qualitatively narrow down the IL candidates. The separation performance of these IL candidates was further evaluated through MD to determine the best IL extractant. Then, the methanol removal performance of the best IL was further evaluated by the liquid – liquid equilibrium experiments and the process simulation. Finally, the separation mechanism of the IL was investigated through QC calculations, wavefunction and MD analysis. The consistency between simulations and experiments indicates that this approach is a very useful tool to screen ILs for specific separation tasks.