Monte Carlo simulations of CO₂-expanded acetonitrile

Abstract

The structure and phase-equilibrium properties of CO₂-expanded acetonitrile (MeCN) were examined using Gibbs Ensemble Monte Carlo simulations. The results showed that the mole fraction of the CO₂ in the binary system increased linearly with pressure and the predicted volume expansion of the liquid phase with pressure is nonlinear and in agreement with experiment. The site–site radial distribution functions (RDFs) were determined for this binary mixture, which show that the homomolecular CO₂–CO₂ and heteromolecular CO₂–MeCN do not exhibit a significant dependence on CO₂ mole fraction. The only major structural change that is seen to occur as the CO₂ mole fraction is increased in the mixture is a decrease in the fraction of nearest neighbour MeCN molecules with parallel dipole orientations.

Acknowledgements

This work is partly supported by the National Science Foundation grant EEC-0310689 providing for the University of Kansas Center for Environmentally Beneficial Catalysis. The authors would like to thank Bhuma Rajagopalan for providing the experimental data of the CO₂-expanded acetonitrile system and Krzysztof Kuczera for helpful discussions and suggestions.