Efficient separation of isomer ketazine and pyrazoline mixtures by polyimide membrane

The separation of isomers—particularly those with highly similar molecular sizes and physical properties—remains a significant challenge. In this study, a polyimide (PI) composite membrane was employed to achieve efficient separation of pyrazoline/ketazine isomers by leveraging steric hindrance effects and hydrogen bonding interactions between the molecules and the membrane surface. Separation experiments were conducted with the PI membrane for ketazine/pyrazoline isomer mixtures with different substituents and concentration gradients. The results demonstrated that a separation factor of ketazine exceeding 10 could be achieved when the pyrazoline-to-ketazine ratio was 0.1. This work provides fundamental experimental data and technical support for the industrial-scale separation of pyrazoline/ketazine isomers, and thus facilitates the development and application of cyclopropane-based high-energy aerospace fuels.