(441c) Molecular Dynamics Simulations of Mixtures of Refrigerants and Deep Eutectic Solvents

Molecular dynamics
simulations of mixtures of refrigerants and deep eutectic solvents

Rubaiyet Abedin, John C. Flake and Francisco R. Hung

Cain Department of Chemical Engineering, Louisiana
State University, Baton Rouge, LA 70803

Heating
and cooling buildings in the U.S. consumes an enormous amount of energy (>10
quadrillion BTU), and is responsible for adding ~1 billion metric tons of CO₂
in the earth’s atmosphere every year. Much of this energy is used as
electricity in vapor-compression systems; however, this technology is mature
and only evolutionary improvements are expected in the near future. Remarkably,
a few studies have shown that several common ionic liquids (ILs) can be
combined with standard fluorocarbon refrigerants for use in absorption refrigeration
systems that use waste heat at relatively low temperatures (~100 °C). Nevertheless, there is limited
understanding (and data) on the VLE behavior of these systems, and only one
working example of an absorption system using this type of mixture.
Furthermore, deep eutectic solvents (DESs), a relatively new class of solvents,
share many of the properties of ILs while being considerable cheaper and mostly
nontoxic. A fundamental understanding of how the chemical structure of the
different species affects the solubility of fluorocarbons in a DES is crucial
to design mixtures suitable for use in absorption refrigeration systems that
use solar energy or waste heat. In this work, we performed molecular dynamics
simulations of mixtures of a conventional fluorocarbon refrigerant,
1,1,1,2-tetrafluoroethane (R134a) with three deep eutectic solvents (1:2
choline chloride/urea, 1:2 choline chloride/glycerol and 1:2 choline
chloride/ethylene glycol). We report and discuss a number of properties for
these systems, including Henry’s law constants of R134a in the three DESs as a
function of temperature, radial distribution functions, and diffusion
coefficients.