Transport properties of CO2-expanded acetonitrile from molecular dynamics simulations

Abstract

Carbon-dioxide-expanded liquids, which are mixtures of organic liquids and compressed CO 2 , are novel media used in chemical processing. The authors present a molecular simulation study of the transport properties of liquid mixtures formed by acetonitrile and carbon dioxide, in which the CO 2 mole fraction is adjusted by changing the pressure, at a constant temperature of 298 K. They report values of translational diffusion coefficients, rotational correlation times, and shear viscosities of the liquids as function of CO 2 mole fraction. The simulation results are in good agreement with the available experimental data for the pure components and provide interesting insights into the largely unknown properties of the mixtures, which are being recognized as important novel materials in chemical operations. We find that the calculated quantities exhibit smooth variation with composition that may be represented by simple model equations. The translational and rotational diffusion rates increase with CO 2 mole fraction for both the acetonitrile and carbon dioxide components. The shear viscosity decreases with increasing amount of CO 2 , varying smoothly between the values of pure acetonitrile and pure carbon dioxide. Our results show that adjusting the amount of CO 2 in the mixture allows the variation of transport rates by a factor of 3-4 and liquid viscosity by a factor of 8. Thus, the physical properties of the mixture may be tailored to the desired range by changes in the operating conditions of temperature and pressure.

Electrodeposition from supercritical fluids

“…107 This is probably due to the addition of 12-13 wt% acetonitrile as a co-solvent which significantly increases the viscosity of the solution. 108,109 Using [Cu(CH 3 CN) 4 ] + in scCO 2 -CH 3 CN it is possible to electroplate smooth, reflective copper films onto 1 cm 2 electrodes. Fig.…”

Systematic evaluation and refinement of existing all‐atom force fields for the simulation of liquid acetonitrile

“…In this way, the success of the molecular simulation study strongly related to the quality/precision of applied potential functions. The force fields proposed for ACN are divided into two categories: the simple (rigid) three‐site model where a single interaction site is considered for the methyl group (united‐atom force field), and the more explicit (flexible) six‐site model in which carbon and three hydrogen atoms attached to it act as separated interaction sites (all‐atom force field) . Systematic evaluation and comparison of some available three‐site models of liquid ACN have previously been presented .…”

Steady-state macroscale voltammetry in a supercritical carbon dioxide medium

“…18 The recent interest in scCO 2 as a medium for electrodeposition and electroplating processes has revolved around the enhanced mass transport imparted by the low density fluid. [14][15][16]19 The enhancement is evident in these recent publications, yet an analytical study of mass transport effects, from a voltammetry perspective, and on the macro scale, has yet to be reported. In this paper we present a study of the metallocene, namely decamethylferrocene (DMFc), in a conventional three-electrode set-up at a macroscale gold electrode, using scCO 2 and acetonitrile as a polar co-solvent.…”

“…The liquid readily dissolved in the scCO 2 , preceded by extensive expansion of the solvent phase during the CO 2 saturation stage, a well-known phenomenon in organic solvents. 18,19 In Fig. 1 these transitions are shown at increasing pressure for 6 mL (ca.…”