Efficient Kinetic Separation of Carbon Dioxide from Acetylene Using Mordenites Featuring Modified 1D Channels with Excellent Selectivity and Diffusion

Abstract

The design of physical adsorbents for a precise recognition of gas molecules with similar kinetic sizes is of importance as adsorptive separation can serve as an alternative to energy-intensive distillation processes. However, it is challenging to balance the selectivity, capacity, and adsorption kinetics of the adsorbents. Herein, an efficient kinetic separation of acetylene and carbon dioxide is reported, which have nearly identical kinetic sizes, achieved through modification of the one-dimensional (1D) channels of a micrometer-sized mordenite. Under ambient conditions, the weak acid salt-modified mordenite denoted as NaAlO₂@MOR(0.5), exhibits a remarkable kinetic separation selectivity of 534.3 while retaining an excellent diffusivity for CO₂. Compared to other adsorbent materials, its dynamic column performance for carbon dioxide significantly exceeds those of molecular sieve materials. In terms of separation selectivity, it is superior to thermodynamic separation adsorbents. The high efficiency of NaAlO₂@MOR(0.5) in CO₂/C₂H₂ kinetic separation is validated by column breakthrough experiments. Furthermore, NaAlO₂@MOR(0.5) has a low cost and high thermal stability. This study can guide the design of adsorbents that balance selectivity, capacity, and gas diffusivity, to provide a highly efficient kinetic separation of gas molecules with similar kinetic diameters.