Preparation of chitosan-copper material and its application on propylene-propane adsorption separation

Propylene is one of the most important olefins in the industry, and conventional separation of propylene/propane relies on low-temperature distillation, which consumes huge amounts of energy. The adsorption separation technique requires low energy consumption and has developed into an important method for the separation of propylene/propane. In this work, chitosan is used as the carbon source, and Cu(II) is immobilized in the molecule through the coordination of –OH and –NH₂ in chitosan with Cu(II). By freeze-drying and high-temperature calcination, Cu(II) in chitosan was reduced to Cu(I), resulting in a porous carbon material containing Cu(I). The adsorption properties of the materials were tested for propylene and propane at 298 K, 1 bar. The Langmuir–Freundlich model was used to fit the adsorption curves and the IAST theory was combined to calculate the selectivity of propylene/propane. The adsorption capacity of carbon materials for propane/propylene under different preparation conditions showed that the best adsorption separation performance for propylene/propane was obtained when the freezing temperature difference was 15 ℃ − (− 18 ℃) and the concentrations of Cu(II) were 0.025 mol/L and 0.0125 mol/L. The breakthrough experiment using a propylene/propane mixture (V_C3H6/V_C3H8 = 50/50) revealed that the Chitosan-Cu (0.025 mol/L) material exhibited a lower adsorption capacity for propane, as compared to its higher adsorption capacity for propylene. Therefore, the adsorption selectivity of propylene/propane reached an impressive 3.877, revealing the potential of carbon materials in the separation of propylene/propane.