Property Estimation Joback Method

Mon, 24 Apr 2017

The Joback method is a group contribution method which calculates thermophysical and transport properties as a function of the sum of group parameters. It uses a very simple and easy to assign group scheme. This article shows how to calculate properties using Joback Method in an excel spreadsheet.

Example

Estimate properties for 1-Butanol based on Joback Method

Structure of 1-Butanol consists of following groups

-CH3 Group : 1
-CH2 Group : 3
-OH (alcohol) Group : 1

Normal Boiling Point

where Tb,i is contribution due to each group. These values for individual group are available in literature and Wikipedia reference below. On combining values for each group normal boiling point comes out to be -

TNBP (K) = 383.10

Critical Temperature

Tc (K) = 545.08

Critical Pressure

Pc (bar) = 43.86

where NA is number of atoms in the molecular structure.


Critical Volume

Vc (cm³/mol) = 278.50

Critical Compressibility

Zc = 0.2695

Acentric Factor

Lee-Kesler method can be used to estimate the acentric factor.





ω = 0.6602

Freezing Point

Tm (K) = 195.66

Heat of Formation (Ideal Gas, 298 K)

Hformation (kJ/mol) = -278.12

Gibbs Energy of Formation (Ideal Gas, 298 K)

Gformation (kJ/mol) = -154.02

Heat of Vaporization (at Normal Boiling Point)

Reidel's equation can be used to estimate a liquid's heat of vaporization at its normal boiling point.

ΔHv (kJ/mol) = 42.38

Heat of Fusion

ΔHfusion (kJ/mol) = 10.2

Heat Capacity (Ideal Gas)






CP (J/mol.K) = 110.96 (at 300 K)

Heat of Vaporization (@ Temperature T)

Watson equation can be used to estimate heat of vaporization at different temperature as following.

ΔHv,2 (kJ/mol) = 49.60 (at 300 K)

Liquid Viscosity



ηL (Pa.s) = 1.936*10-3 (at 300 K)

where Mw is the molecular weight.

Liquid Density

Rackett equation can be used to estimate liquid density from critical properties as following -

ρL (gm/cm³) = 0.756 (at 300 K)

Liquid Vapor Pressure

Lee-Kesler equation can be used to estimate liquid vapor pressure as following -




Pvp (bar) = 0.018

Web based calculation available at CheCalc.com

Spreadsheet

Spreadsheet for property estimation based on Joback Method

References

  1. Joback Method - Wikipedia
  2. Molecular Knowledge Systems
  3. Chemstation Physical Properties User Guide



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