Highly selective separation of pentane isomers using ZIF-8/DMPU-water slurry

Separation of light hydrocarbon isomers is always an important and challenging task in the petrochemical industry due to their similar physicochemical properties. This paper presents the absorption-adsorption hybrid method to separate pentane isomers using a flowable zeolitic imidazolate framework-8 (ZIF-8) slurry prepared with N, N′-Dimethylpropylene urea (DMPU) and water. Firstly, the single-component kinetic sorption profiles for n-pentane and iso-pentane in the slurry were measured. It appears significant sorption kinetic differences between the pentane isomers in ZIF-8/DMPU-water slurry. Subsequently, the separation performances for n/iso-pentane gas mixtures were studied systematically. The results show that the selectivity for pentane isomers using ZIF-8/water slurry is extremely high (1877 specifically), and the selectivity decreases gradually when the DMPU content in the solvent increases, while conversely the sorption speed increases rapidly. The selectivity as a function of time was described to graphically characterize the kinetic-based separation for pentane isomers. With excellent behavior in selectivity, sorption speed, sorption capacity (1.10 mol/L for n-pentane in ZIF-8/DMPU slurry), and renewability, this absorption-adsorption hybrid method is of great potential in the separation of pentane isomers.