Viscosity

Estimation of pure component properties. Part 4: Estimation of the saturated liquid viscosity of non-electrolyte organic compounds via group contributions and group interactions

  • Yash Nannoolala, b, Jürgen Rareya, c,, Deresh Ramjugernatha
  • a Thermodynamics Research Unit, School of Chemical Engineering, University of Kwa-Zulu Natal, Durban 4041, South Africa
  • b SASOL Technology (Pty) Ltd., Sasolburg, South Africa
  • c Industrial Chemistry, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
Received 25 September 2008, Revised 13 February 2009, Accepted 16 February 2009, Available online 9 March 2009

Abstract

A new group contribution method for the prediction of pure component saturated liquid viscosity has been developed. The method is an extension of the pure component property estimation techniques that we have developed for normal boiling points, critical property data, and vapour pressures. Predictions can be made from simply having knowledge of the molecular structure of the compound. In addition, the structural group definitions for the method are identical to those proposed for estimation of saturated vapour pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid viscosity data for more than 1600 components. Results of the new method are compared to several other estimation methods published in literature and are found to be significantly better. A relative mean deviation in viscosity of 15.3% was observed for 813 components (12,139 data points). By comparison, the Van Velzen method, the best literature method in our benchmarking exercise produced a relative mean deviation of 92.8% for 670 components (11,115 data points). Estimation results at the normal boiling temperature were also tested against an empirical rule for more than 4000 components. The range of the method is usually from the triple or melting point to a reduced temperature of 0.75–0.8. Larger than average deviations were observed in the case of molecules with higher rotational symmetry, but no specific correction of this effect was included in this method.

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