An Ideal Molecular Sieve for Acetylene Removal from Ethylene with Record Selectivity and Productivity

Abstract

Realization of ideal molecular sieves, in which the larger gas molecules are completely blocked without sacrificing high adsorption capacities of the preferred smaller gas molecules, can significantly reduce energy costs for gas separation and purification and thus facilitate a possible technological transformation from the traditional energy-intensive cryogenic distillation to the energy-efficient, adsorbent-based separation and purification in the future. Although extensive research endeavors are pursued to target ideal molecular sieves among diverse porous materials, over the past several decades, ideal molecular sieves for the separation and purification of light hydrocarbons are rarely realized. Herein, an ideal porous material, SIFSIX-14-Cu-i (also termed as UTSA-200), is reported with ultrafine tuning of pore size (3.4 Å) to effectively block ethylene (C₂H₄) molecules but to take up a record-high amount of acetylene (C₂H₂, 58 cm³ cm⁻³ under 0.01 bar and 298 K). The material therefore sets up new benchmarks for both the adsorption capacity and selectivity, and thus provides a record purification capacity for the removal of trace C₂H₂ from C₂H₄ with 1.18 mmol g⁻¹ C₂H₂ uptake capacity from a 1/99 C₂H₂/C₂H₄ mixture to produce 99.9999% pure C₂H₄ (much higher than the acceptable purity of 99.996% for polymer-grade C₂H₄), as demonstrated by experimental breakthrough curves.

An ideal molecular sieve is realized for the highly efficient removal of C₂H₂ from C₂H₂/C₂H₄ (1:99) mixture, attributed to the optimized pore sizes to efficiently block C₂H₄ molecules, and strong binding sites to take up a record-high amount of C₂H₂, thus simultaneously producing high purity C₂H₄ (99.9999%) with record C₂H₄ productivity of 87.5 mmol g⁻¹ per cycle and recovery of C₂H₂ (97%).

http://ift.tt/2yOeY6z