Selective adsorption of propene over propane on Li-decorated poly (triazine imide)
Yong Wang, Xiaoxia Jia, Libo Li, Jiangfeng Yang, Jinping Li
Abstract
Solid adsorbents that simultaneously have high selectivity and uptake capacity are highly promising as alternatives to conventional cryogenic distillation of propene/propane (C3H6/C3H8) separation. Coordinatively unsaturated metal sites (CUS) plays a vital role in selective adsorption of olefins over paraffins. Ultrathin poly (triazine imide) (PTI) nanosheets can reach rapid gas adsorption equilibrium, due to its large surface-to-volume ratio. In this work, combining the advantages of the CUS and the PTI nanosheets, Li CUSs were introduced into the PTI nanosheets for C3H6/C3H8 separation. Density functional theory (DFT) calculations demonstrated the thermodynamic feasibility of incorporating Li CUSs into the PTI nanosheets. These highly exposed Li CUSs were predicted to have a higher adsorption affinity toward C3H6 than C3H8. Using the DFT-derived force field parameters, we further performed grand canonical Monte Carlo (GCMC) simulations to investigate C3H6/C3H8 adsorption on the Li–PTI complexes slit pore model with different pore widths (H). We found that the Li–PTI complexes display considerable C3H6/C3H8 selectivity (4.2–7.9) under relevant conditions. Moreover, the Li–PTI complexes slit pore have large C3H6 working capacities (1.5–4.0 mmol g−1), superior to those calculated for the most of adsorbent materials that have been reported. The Li–PTI complexes with slit pore architecture show potential as C3H6/C3H8 separation materials.