283401 Rational Surfactant Design for Hydrofluoroolefins (HFO-1234yf and HFO-1234ze(E)) , the Next Generation Refrigerant/Propellants: A Molecular Dynamics Approach

Monday, October 29, 2012
Hall B (Convention Center )
Lin Yang, Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI, Sandro R. P. da Rocha, Wayne State University, Detroit, MI and Cláudio Dariva, Núcleo de Estudos em Sistemas Coloidais – NUESC, Universidade Tiradentes, Aracaju, Brazil

Hydrofluoroalkane (HFA) refrigerants/propellants have a relatively high global warming potential (GWP), at 1430 for HFA-134a and 3200 for HFA-227.  With the advent of a series of global warming-related regulations, new alternatives to the traditionally used HFAs are thus being sought.  Hydrofluoroolefins (HFOs), with their zero ozone depleting potential, and low GWP - 6 for HFO-1234ze and 4 for HFO-1234yf, are promising next generation working fluids in a wide range of applications, from foams, to medical aerosols, to refrigerants.  The design of HFO-philic species and surface active agents for HFO-based systems is thus of great relevance.

In this work we use atomistic molecular dynamics simulations to probe the microstructure of HFO interfaces, including HFO-air (vacuum) and HFO-water, and to study the activity of surfactants at those interfaces.  We investigate a series of non-ionic surfactants, with alkyl- [representative of the Brij surfactant class (CH3(CH2)n(OCH2CH2)nOH)],and propylene oxide-based HFO-philic moieties.  The surface tensions for both HFOs are seen to match the experimental results within a wide range of temperature (270-300 K).  The interfacial tensions for HFO-1234ze(E)-water and HFO-1234yf-water are 40.6±1.0 and 44.4±1.0 respectively.  With a surfactant coverage of 112Å2/surfactant the interfacial tension undergo a drop of 12.0 and 11.3 respectively for HFO-1234ze(E)-water and HFO-1234yf-water.  No experimental results are available yet for comparison.  The surfactant results will be discussed at varying surface coverage, and a detailed analysis of the structure of the surfactant-modified interfaces will be provided.

Extended Abstract: File Not Uploaded
See more of this Session: Interfacial Phenomena (Area 1c) Poster Session
See more of this Group/Topical: Engineering Sciences and Fundamentals