A new proposed approach to estimate the thermodiffusion coefficients for linear chain hydrocarbon binary mixtures

Abstract

Thermodiffusion behaviors in nonassociating mixtures have an important role in separation processes of the oil industry. The variations of composition and temperature may either lessen or enhance the separation in mixtures. A new model regarding the prediction of thermodiffusion coefficients for linear chain hydrocarbon binary mixtures using the thermodynamics of irreversible process is proposed. The model predicts the net amount of heat transported based on available volume for each molecule. This newly proposed model combined with the perturbed chain statistical associating fluid theory equation of state has been applied to predict thermodiffusion coefficients for binary hydrocarbon mixtures of C(10)-nC(i) (i=5,6,7,15,16,17,18), C(12)-nC(i) (i=5,6,7,8,9), and C(18)-nC(i) (i=5,6,7,8,9,12). Comparisons of the calculated theoretical results with the experimental data show good performance of the proposed model. In particular, this model which is based on the kinetic approaches has been found to be the most reliable and represents a significant improvement over the earlier models.

Study of thermodiffusion of carbon dioxide in binary mixtures of n-butane & carbon dioxide and n-dodecane & carbon dioxide in porous media

“…Thermodiffusion coefficient estimation based on free volume theory has been found to be most reliable and represents a significant improvement over the earlier thermodiffusion models [19,20]. Abbasi et al [19,20] have developed two new models for predicting the activation energy of viscous flow for each component in a mixture based on the free volume theory.…”

“…Abbasi et al [19,20] have developed two new models for predicting the activation energy of viscous flow for each component in a mixture based on the free volume theory. The new models combined with the Dougherty & Drickamer model and Shukla & Firoozabadi model are used to predict the net heat of transport for each component in the binary mixtures.…”

“…As a matter of fact, the size of the molecule that has a significant effect on diffusivity of the molecule is considered in predicting the net heat of transport. Initially, the Dougherty and Drickamer model was modified for predicting thermodiffusion coefficients for binary linear chain hydrocarbon mixtures [19]. Thermodiffusion coefficients of C 10 À nC i (i ¼ 5, 6,7,15,16,17,18), C 12 À nC i (i ¼ 5, 6,7,8,9), and C 18 À nC i (i ¼ 5, 6,7,8,9,12) were calculated by the new proposed model.…”

“…Both Dougherty & Drickamer and Shukla & Firoozabadi models demonstrated good starting in the calculation of the net heat of transport, but they did not satisfy completely the thermodiffusion estimation [13e15,18]. Abbasi et al [19,20] modified the Dougherty & Drickamer and Shukla & Firoozabadi models in the calculation of the net heat of transport. They proposed two new theoretical models for estimation of the activation energy in hydrocarbon mixtures based on the free volume theory.…”

“…They proposed two new theoretical models for estimation of the activation energy in hydrocarbon mixtures based on the free volume theory. In their models [19,20], molecular size effect has an important role in the estimation of the activation energy of each component in a mixture. Their proposed models have been applied to predict binary thermodiffusion coefficients of several mixtures of linear chain and aromatic hydrocarbons in different compositions and temperature.…”