Modelling diffusion of fragrances: A radial perspective

Abstract

In the present study, a theoretical model based on Fick's second law for radial diffusion is proposed for modelling the radial diffusion of fragrances. For that, three fragrance systems were studied containing α-pinene and limonene as pure components, or a mixture of α-pinene, limonene, linalool, and geranyl acetate. This model combines the UNIFAC group contribution method for the vapour-liquid equilibrium with the Fickian radial diffusion model. The experimental gas concentrations of the odorant components were measured in a diffusion tube (1D axial diffusion) and quantified using gas chromatography with a flame ionization detector. The numerical solutions were obtained using the general Process Modelling Systems (gPROMS) software version 4.2.0. An equivalence relation between the 1D axial diffusion model and 1D radial diffusion model was developed. Finally, the odour intensity and character of the studied fragrance systems were assessed using Stevens’ power law and the strongest component model, respectively. The obtained results showed good agreement between the numerical simulation and the experimental gas concentration data, suggesting the proposed methodology as an efficient tool to assess the radial diffusion of fragrance systems over time and distance.