(44e) Investigating MFI Zeolites for Separating Refrigerant R-410A

Hydrofluorocarbon (HFC) refrigerants are essential in heating, ventilation, air-conditioning, and refrigeration (HVACR) technology; however, many HFCs have high global warming potentials (GWPs) and are being phased out as global efforts increase to mitigate climate change. Most recently, the U.S. American Innovation and Manufacturing (AIM) Act imposed an 85% phasedown of HFCs by 2036 relative to the average of 2011–2013 baseline levels.

As industries phase out high-GWP HFCs, next-generation hydrofluoroolefin (HFO) refrigerants are being adopted as environmentally friendly alternatives. The transition necessitates the removal of existing refrigerants from circulation, creating an urgent need for efficient recovery and recycling strategies. However, many commonly used fluorocarbon refrigerants are azeotropic or near-azeotropic HFC blends, such as R-410A (50/50 wt% HFC-32(CH₂F₂)/HFC-125(CHF₂CF₃)), and must be separated before being recycled. Since the mixtures cannot be separated using conventional distillation techniques, new technologies must be developed so that the reclaimed refrigerants can be recycled and repurposed.

Previous work with refrigerant R-410A showed that zeolites can effectively separate azeotropic fluorocarbon mixtures. Basic zeolites, such as 5A (Na, Ca-LTA) and 13X (Na-FAU), exhibited selectivity toward HFC-32, whereas those with high silica-to-alumina (SAR) ratios (e.g., H-FAU, H-MOR, and H-MFI with SAR > 30) selectively adsorbed HFC-125. Notably, pure and binary adsorption data, as well as dynamic breakthrough behavior, showed that silicalite (MFI, SAR = 407) exhibits strong HFC-125 selectivity and minimal kinetic limitations. The present study further investigates MFI zeolites for separating refrigerant R-410A. Dynamic breakthrough experiments were conducted for H-MFI zeolites with varying SARs (i.e., 30 to 360) and calcination temperatures (i.e., 550-770 °C) to better understand the properties that influence HFC-125 selectivity. In addition to breakthrough times, adsorption capacities and bed efficiencies were determined through open system analysis to provide further insight into separation and adsorption behaviors.