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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

`-CH`_{3} Group : 1

`-CH`_{2} Group : 3

`-OH (alcohol) Group : 1`

Normal Boiling Point

where T_{b,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 -

`T`_{NBP} (K) = 383.10

Critical Temperature

`Tc (K) = 545.08`

Critical Pressure

`Pc (bar) = 43.86`

where N_{A} 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)

`H`_{formation} (kJ/mol) = -278.12

Gibbs Energy of Formation (Ideal Gas, 298 K)

`G`_{formation} (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

`ΔH`_{fusion} (kJ/mol) = 10.2

Heat Capacity (Ideal Gas)

`C`_{P} (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

`η`_{L} (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 -

`ρ`_{L} (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

- Joback Method - Wikipedia
- Molecular Knowledge Systems
- Chemstation Physical Properties User Guide

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