Diffusion Coefficients of Thiols in Hydrocarbon and Aqueous Alkaline Solutions

Abstract

This study examines the diffusion coefficients of ethanethiol and n-propanethiol in model hydrocarbon phases (n-pentane and n-octane) and aqueous alkaline phases (NaOH and KOH solutions). A theoretical analysis shows that, at low thiol concentrations, the multicomponent diffusion matrices reduce to the Einstein self-diffusion coefficients, supporting their use in interphase mass-transfer modeling. Thiol diffusion coefficients were determined by NMR diffusometry and molecular dynamics simulations. The predictive performance of the Wilke–Chang and Lusis–Ratcliff equations was also evaluated, and thiol diffusion coefficients at infinite dilution in hydrocarbon mixtures were predicted. The results show that these computational approaches can be used to predict thiol diffusion coefficients for mass-transfer modeling of thiol-removal processes.