Energy-Efficient Separation of a Greenhouse Gas: New Study from Pusan National University

Leakage of the greenhouse gas sulfur hexafluoride (SF₆) from systems like gas-insulated switchgear contributes significantly to its presence in the atmosphere. Metal–organic frameworks (MOFs) have been touted as potential tools to isolate this gas before it enters the environment, but the most efficient MOFs have not been identified. Now, scientists from Pusan National University in South Korea have used a multi-scale approach to pick the best MOFs for the job.

Gas-insulated switchgears are critical for the effective distribution of electricity from the source to the points of demand. Such switchgears often use a mixture of the gases nitrogen (N₂) and sulfur hexafluoride (SF₆). There is a catch though; SF₆ is a greenhouse gas, and its concentration in the atmosphere has increased quickly in recent years. Pressurized SF₆ is used for insulation in systems like gas-insulated switchgear, and its leakage contributes significantly to its atmospheric presence. Hence, we need energy-efficient methods to isolate this gas before it enters the environment. One potential method is the use of nanoporous materials called metal–organic frameworks (MOFs).

Using the extensive CoRE MOF Database and a series of simulations, researchers from Pusan National University, South Korea, attempted to determine which MOFs were most suited for isolating SF₆ from switchgears. Prof. Yongchul G. Chung—who led their study published in the Chemical Engineering Journal—remarks, “Thousands of MOFs could potentially be used to capture SF₆ from switchgears, but it is hard to identify the best ones. Meanwhile, we do not know if a process that uses a given MOF is more energy-efficient than the other one until we test all the MOFs in different process settings. This creates combinatorial problem, and is a significant bottleneck in materials discovery and deployment.”

Prof. Chung’s team employed a multi-scale approach that considered two factors: materials and operational processes. First, they narrowed down the MOFs showing the most optimal material properties, like pore size and cost. Then, they used modeling studies to examine the performance of the selected MOFs under two different process conditions—vacuum swing adsorption (VSA) and pressure swing adsorption (PSA). As a result, they identified three MOFs providing the most energy efficient capture of SF₆ under VSA and two others showing the best performance under PSA. “One of our key findings is that the materials that are optimal for one process (i.e., VSA) are not optimal for the other (i.e., PSA),” comments Prof. Chung, highlighting the importance of this distinction in practical process development.

The materials identified in this study could be used for capturing SF₆ from gas-insulating switchgears, reducing its greenhouse effects and environmental impact. Previous Experimental studies have already shown how effective some of these materials are in SF₆ capture, adding to the validity of the findings.

For Prof. Chung and his team, however, the road does not end there. Their modeling framework, they believe, could also be extended for screening and identifying materials optimal for the separation and purification of other gases. The possibilities may be endless, but they all lead to the same goal—energy-efficient and sustainable technology for energy and environment.