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In the present work, deep eutectic solvents (DESs) were synthesized in a one-step process by heating the hydrogen bond acceptors (HBAs) tetrabutylammonium bromide and tetrabutylphosphonium bromide, along with two hydrogen bond donors (HBDs) ethanolamine and N-methyldiethanolamine, which were mixed in certain molar ratios. This mixture was then mixed with water to form a DES + water system. The densities of the prepared DES + water systems were successfully measured using the U-tube oscillation method under atmospheric pressure over a temperature range of 293.15–363.15 K. The CO2 trapping capacity of the DES + water systems was investigated using the isovolumetric saturation technique at pressures ranging from 0.1 MPa to 1 MPa and temperatures ranging from 303.15 K to 323.15 K. A semi-empirical model was employed to fit the experimental CO2 solubility data, and the deviations between the experimental and fitted values were calculated. At a temperature of 303.15 K and a pressure of 100 kPa, the CO2 solubilities in the DES + water systems of TBAB and MEA, with molar ratios of 1:8, 1:9, and 1:10, were measured to be 0.1430 g/g, 0.1479 g/g, and 0.1540 g/g, respectively. Finally, it was concluded that the DES + water systems had a superior CO2 capture capacity compared to the 30% aqueous monoethanolamine solution commonly used in industry, indicating the potential of DES + water systems for CO2 capture.

Deep eutectic solvents are now widely used in metal electrochemical deposition, biomass catalysis and material synthesis because of their advantages of greenness, low cost, good biocompatibility and biodegradability, and it is proved that DESs have great potential for its utilization as heat transfer fluids. In this work, eight DESs were prepared by thermal method using choline chloride as the hydrogen bond acceptor and glycerol, polyethylene glycol 600, lactic acid and o-cresol as the hydrogen bond donor. Based on the flow calorimetry method, the specific heat capacity system was established and its reliability and precision were verified by measuring the specific heat capacity of deionized water. The maximum deviation of the experimental value and the standard value under the pressure 101 kPa was 2.03%, and the average absolute deviation was 1.01%, and the repeatability was less than 1.5%. Then, the densities and the constant pressure specific heat capacities of eight DESs in the temperature range of 293 K–353 K and 293 K–373 K were measured respectively. The experimental results could support for the scale utilization of DESs.

Marangoni flow occurs when a fluid-fluid free surface is exposed to a non-uniform thermal field. Recently, Marangoni flow has been used to fabricate micro/nano-structures in thin films, which is referred to as thermocapillary patterning. A thin liquid-air film is confined between a hot plate and a topographic cold plate. Marangoni flow thus takes place, and the film evolves into micro/nano-structures that comply with the geometry of the template. In this paper, a numerical model based on the moving mesh method is proposed to study the dynamic process of thermocapillary patterning. Liquid and air are calculated simultaneously with proper boundary conditions imposed at the interface. The numerical model enables characterization of the thermal field and the fluid flow, and thus the deformation of the liquid film. The effect of some key parameters, including temperature difference, template geometry, and liquid film viscosity, on thermocapillary patterning is investigated. The numerical model and the obtained results serve as a useful and representative guide for practical experiments.

Water must be separated from water-in-oil (W/O) emulsion because of the corrosion it brings to the relative equipment in the process of transportation and storage. It is an effective method to apply external electric field to achieve high performance of separating small, dispersed water droplets from W/O emulsion; however, the coalescing micromechanism of such small salty droplets under AC electric field is unclear. In this paper, molecular dynamics simulation was adopted to investigate the coalescence and separation process of two NaCl-aqueous droplets under AC electric field and discuss the effect of AC electric field frequency, as well as the time required for contacting, the critical electric field strength, the dynamic coalescence process and the stability of the final merged droplet. The results show that the critical electric field strength of the droplet coalescence increases with the increase of frequency, while the time required for droplet contacting becomes shorter. The shrinkage function curve was applied to characterize the droplet coalescence effect and it was found that the droplets coalescence and form a nearly spherical droplet under the AC electric field with a frequency of 1.25 GHz and strength of 0.5 V/nm. When the electric field frequency is 10 GHZ, the merged droplet presents a periodic fluctuation with the same period as the AC electric field, which mainly depends on the periodic movement of cations and anions under the AC electric field. The results can provide theoretical basis for the practical application of electrostatic demulsification technology in the petroleum or chemical industry from the microscopic perspective.

Transport properties of liquid are the necessary data for thermodynamic cycle design and optimization, and most of them could be measured by experiments. Molecular dynamic simulation provides an effective way to predict these transport properties in some limited condition that cannot be measured experimentally. In this work, NEMD (nonequilibrium molecular dynamics) method has been applied to calculate the thermal conductivity and RNEMD (reverse nonequilibrium molecular dynamics) method has been used to calculate the viscosity of alcohols. The calculated results are in good agreement with experimental values. The results prove the feasibility of the two simulation methods and provide a new way to calculate the thermal conductivity and viscosity of other organic liquids in some limited conditions.

Recently, biodiesel is considered as a biodegradable, renewable and high-potential fuel which could be used directly in tradition internal combustion engines. Fuel’ transport properties in high pressure are required to model the process of fuel spray, atomization and combustion accurately. This work, three ethyl esters’ liquid thermal conductivity (biodiesel compounds) in the liquid phase was measured by an experiment system which is established based on a transient hot-wire method with a bare platinum hot wire. The measurements were conducted at the temperatures ranging from 292 K to 372 K and pressure up to 15 MPa. The combined expanded uncertainty of the measurement was estimated to be ±2.0% (in the 0.95 confidence level). For interpolation, the relationship between measured results with temperature and pressure were correlated as a polynomial function, and the maximum deviation of correlations were less than 0.30%.

Due to their splendid advantages, deep eutectic solvents have attracted high attention and are considered as analogues of ionic liquids. Deep eutectic solvents (DESs) are homogeneous mixtures formed by two or three green and cheap components through hydrogen bond, which is divided into hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD). Recently, Betaine has been widely used as a hydrogen bond acceptor. In this work, four DESs were synthesized by blending betaine as HBA and 1,2-propanediol as HBD in four molar ratios (1:3.5, 1:4, 1:5, 1:6). Then, the physical properties of these DESs were measured. The density values were measured within the temperature range (293.15 K to 363.15 K) at atmospheric pressure, whereas the surface tension and viscosity data were determined in four and seven temperatures between 293.15 K and 353.15 K. The relationship between the density and surface tension with temperature have been analyzed and have been fitted as a linear function. The commonly used Arrhenius model was used to describe the dependence between viscosity and temperature. The results of this study are important not only for the DESs’ industrial applications but also for the research on their synthesis mechanism and microstructure.