Supercritical fluids viscosity reduction effects

The supercritical fluids exhibit gas-like viscosities, diffusivities, and liquid-like densities. These favorable transport properties lead to enhanced mass transfer, permeation, and wetting characteristics. The mass transfer limited multiphase reactions will benefit from reduction of a number of phases, as in the case of most oxidation, hydrogenation, or replacement of the more viscous liquid phase with a supercritical or a less viscous expanded liquid phase. The mobility combined with tunability results in effective maintenance of catalyst activity in heterogeneous catalysis. 

According to Tilly et al. (1994), the properties influence each other, and the effect of pressure on the viscosity of fluids in the supercritical state is related to the density characteristics. With an increase in density, the intermolecular forces increase as a result of the reduction in the space between the molecules, which requires the application of greater force to enable molecular flow. 

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