Shaping of Silver-Functionalized Metal–Organic Frameworks for Efficient Separation of Ethylene Over Ethane

Separation of the ethane/ethylene mixture is one of the most important but challenging processes in the petrochemical industry owing to their closely resembling physical and chemical characteristics. The remarkable characteristics of customized pore aperture and functionality endow metal–organic frameworks (MOFs) with great prospects in the adsorption separation of an ethane/ethylene mixture. However, large fixed-bed pressure drops, dustiness, transportation, and handling challenges of the powdered MOFs have largely restricted their large-scale industrial applications. Herein, we successfully prepared a silver-functionalized MOF pellet adsorbent using renewable carboxymethyl cellulose (CMC) as the binder and explored its feasibility for adsorptive separation of C2H4/C2H6 in the industry via both single-component adsorption isotherms and breakthrough experiments. Scanning electron microscopy and N2 adsorption isotherms revealed the "solid bridge" formed by CMC between MIL-101-SO3Ag@CMC pellets that tightly hold MOF crystals together while minimizing pore blockage. In addition, the pellets also attained excellent mechanical strength and stability sufficient to meet industrial application standards. Due to the formation of π-complexation between Ag(I) ions and the ethylene, MIL-101-SO3Ag@CMC pellets demonstrated a moderate-high ethylene adsorption capacity of 2.23 mmol/g at 298 K and 1 bar and an excellent separation performance for ethylene/ethane. Significantly, the ideal adsorbed solution theory selectivity of the ethylene/ethane (50:50, v/v) mixture for pellets was 25.2 at 298 K and 10 kPa, far exceeding most reported adsorbents. Furthermore, breakthrough experiments and humid adsorption experiments verified that MIL-101-SO3Ag@CMC can achieve high-purity ethylene (>99.9%) from the binary ethane/ethylene (50:50, v/v) mixture, indicating that MIL-101-SO3Ag@CMC is a promising adsorbent with both efficient C2H4/C2H6 selectivity and excellent stability.