Integrated Molecular and Separation System Design for Hydrofluorocarbon Recycling

Enabling Hydrofluorocarbon (HFC) Recycling with Innovative Separations

Mandated by the 1987 Montreal Protocol, chlorofluorocarbon (CFC) refrigerants have been gradually replaced by HFCs to prevent ozone depletion. Many of these second-generation HFC mixtures, however, have a high global warming potential (GWP) and the 2016 Kigali agreement ordered their gradual phase-out. Due to the often azeotropic compositions of these HFC refrigerants, existing separation methods for removing the high GWP components are currently infeasible or impractical, but it is wasteful to incinerate HFC mixtures as some HFC components have low GWPs and can be recycled.

We hypothesize that custom Ionic Liquids (ILs) can be designed to remove low GWP HFC components from specific HFC mixtures. Traditionally, Computer-Aided Molecular Design (CAMD) methods would be used to screen the millions of potential ILs for properties specific to a particular HFC separation. However, these methods often fail for complex IL molecules and lead to uncertainty as to which candidate IL design should be promoted for experimental analysis.

Integrating Molecular Simulations and Process Optimization

To overcome this issue, we propose augmenting traditional CAMD methods with molecular simulations for more reliable IL screening. Molecular simulations, which use classical force field methods to calculate the physical properties of molecules, can be used as a guide for focusing on specific IL designs within CAMD. However, accurate force field parameters are necessary for accurate property prediction so we are exploring uncertainty within molecular simulations of mixtures of hydrofluorocarbons (HFCs) and ILs, which are used to inform CAMD decisions in developing IL separating agents for azeotropic separation of HFC mixtures into high and low global warming potential (GWP) components.

Related Presentations

Bridgette Befort*, Edward J. Maginn, and Alexander W. Dowling. Discovery of New Ionic Liquids Via Molecular Simulations for the Separation of Azeotropic Mixtures of High Global Warming Potential Hydrofluorocarbon Refrigerants. AIChE Annual Meeting, Orlando, FL, November 14, 2019. Oral Presentation. [link]

Bridgette Befort*, Edward J. Maginn, and Alexander W. Dowling. Integration of Molecular Simulations and Computer-Aided Molecular Design to Enable Novel Azeotropic Separations. AIChE Annual Meeting, Orlando, FL, November 12, 2019. Poster. [link]

Bridgette Befort*, Edward J. Maginn, and Alexander W. Dowling. Process and Molecular Design Integration for the Separation of Hydrofluorocarbon Mixtures. FOCAPD, Copper Mountain Resort, CO, July 14, 2019. Poster.

Support from Notebaert Fellowship (B. Befort), the University of Notre Dame, and NSF Grant No. 1917474.

Collaborators

Prof. Edward Maginn, U. Notre Dame

Prof. Mark Shiflett, U. Kansas