High pressure solubilities and diffusion coefficients of carbon dioxide in polyethylene glycol 400

The aim of this study is to determine the solubilities and diffusion coefficients of carbon dioxide in polyethylene glycol 400 (PEG 400) at high pressure. Carbon dioxide forms a gas-expanded liquid system (GXL) with PEG 400 which can be used as a solvent system for biphasic reactions. During the formation of the GXL system, the mass transfer is one-way in a certain pressure range; while carbon dioxide dissolves in the liquid polymer, the polymer does not transfer into the gas phase in measurable quantities. During the dissolution process, the liquid expands and also, its molar density changes. First, equilibrium solubilities at different pressures up to 80 bar are determined. To determine the mutual diffusivities in the system at a certain temperature and pressure, time-dependent liquid solubilities of carbon dioxide must be known. To obtain these data, the experimental set-up used consists of a pressure and temperature-monitored view-cell, high pressure syringe pump for the transfer of carbon dioxide to the cell, and a cathetometer for measuring the changes in the liquid level. A computational fluid dynamics model which accounts for the moving interface using Volume-of-fluid method and variable density is fit to the experimental data. The increase in diffusivities with the dissolution of carbon dioxide in polyethylene glycol, is determined at 80 bar and a temperature of 313.15 K. The change in diffusivities with the dissolution of carbon dioxide in polyethylene glycol is determined at 80 bar and a temperature of 313.15 K. The diffusivities have increased from 3.2x10-10 m2/s to 19.2x10-10 m2/s during the process.