Azeotropic Fluorocarbon Refrigerant Mixture Separations Using Porous Material

Fluorocarbon refrigerants have been evolving over the past three decades for the purpose of environmental responsibility, performance, and safety. The most widely used fluorocarbon refrigerants today are the hydrofluorocarbon refrigerants (HFCs). Many of these refrigerants are HFC mixtures and are azeotropic in nature. Although HFCs have a zero ozone depletion potential (ODP), some have relatively high global warming potentials (GWP). As a result, regulations such as the Kigali Agreement propose to regulate the future use of HFC refrigerants in certain applications. The refrigerant industry is therefore currently moving toward the production and marketing of hydrofluoroolefin (HFO) refrigerants and HFO/HFC refrigerant blends due to their lower GWPs.

Project EARTH (Environmentally Applied Research Towards Hydrofluorocarbons) focuses on the safe and sustainable recycling of azeotropic HFC refrigerant mixtures. Rather than venting or incinerating the millions of kilograms of these high GWP refrigerants currently in circulation, a more sustainable option would be to recycle them. In order to do this, however, these HFC mixtures must first be separated into their constituent species, a process made difficult due to their azeotropic nature. Project EARTH will investigate the separation of azeotropic HFCs beginning with R-410a, a near-azeotropic refrigerant mixture composed of 50 wt.% R-32 (CH₂F₂) and 50 wt.% R-125 (CHF₂CF₃). While R-410a itself has a high GWP (2088, relative to CO₂ = 1.0), R-32 has a more acceptable GWP of 675 and has the potential to be recycled and reused in refrigerant mixtures with HFOs. The GWP of R-125 (3500) is relatively high and must be separated from R-32 and in the future, R-125 can serve as a feedstock for producing lower GWP products. The separation of R-410a is an important and critically needed separation process that will have a significant impact on the environment and the heating, ventilation, air-conditioning, and refrigeration (HVACR) industry. This presentation will focus on the use of porous materials such as zeolites for the separation of R-32 and R-125.