Efficient adsorptive separation of C3H6 over C3H8 on flexible and thermoresponsive CPL-1

Abstract

The separation of olefin/paraffin mixtures is of great importance for the petrochemical industry, mainly achieved by using energy-intensive cryogenic distillation. We herein reported a flexible pillared-layer framework CPL-1 possessing a thermoresponsive gate opening behavior for C3H6 adsorption. We measured the C3H6 and C3H8 adsorption and desorption isotherms of CPL-1 at six different temperatures (273, 278, 283, 288, 293 and 298K), respectively. Results showed that the gate opening pressure of C3H6 adsorption for CPL-1 increased with an increase of the adsorption temperature from 273K to 288K. However, no gate opening effect was observed within the measured pressure (<100kPa) as the temperature increased to 293 and 298K. In contrast, C3H8 adsorption for CPL-1 only occurred surface adsorption without appreciable amount adsorbed due to the closed phase of pores under all measured conditions. Thus, we investigated the adsorptive separation of C3H6 over C3H8 for CPL-1 at 273K and developed the regeneration process at room temperature (298K), based on its unique thermoresponsive property. Breakthrough experiments demonstrated the superior C3H6/C3H8 separation performance of CPL-1. Static and dynamic regeneration experiments showed that CPL-1 had excellent stability and high desorption efficiency after five consecutive adsorption-desorption cycles. Particularly, CPL-1 can be easily regenerated at 298K since the desorption activation energy of C3H6 on CPL-1 was only 22.81kJ/mol. Furthermore, molecular dynamics (MD) simulation revealed that the hydrogen bonding was a key factor governing the selective adsorption of C3H6 over C3H8 in CPL-1. This investigation highlighted the central importance of flexibility of adsorbent, and suggested that CPL-1 could be an interesting material for C3H6/C3H8 separation and had excellent regeneration property.