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
Tc (K) = 545.08
Pc (bar) = 43.86
where NA is number of atoms in the molecular structure.
Vc (cm³/mol) = 278.50
Zc = 0.2695
Lee-Kesler method can be used to estimate the acentric factor.
ω = 0.6602
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)
ηL (Pa.s) = 1.936*10-3 (at 300 K)
where Mw is the molecular weight.
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