Joback method: Difference between revisions

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{{Short description|Thermodynamic model}}

The '''Joback method'''<ref>Joback K. G., Reid R. C., "Estimation of Pure-Component Properties from Group-Contributions", ''Chem. Eng. Commun.'', 57, 233–243, 1987.</ref> (often named '''Joback/Reid method''') [[Prediction|predicts]] eleven important and commonly used pure component thermodynamic properties from molecular structure only.

The '''Joback method''', often named '''Joback–Reid method''', [[Prediction|predicts]] eleven important and commonly used pure component thermodynamic properties from molecular structure only. It is named after Kevin G. Joback in 1984<ref>{{cite thesis|last=Joback |first=K. G.|date=1984 |title=A Unified Approach to Physical Property Estimation Using Multivariate Statistical Techniques |url=https://dspace.mit.edu/bitstream/handle/1721.1/15374/12352302-MIT.pdf?sequence=2 |type=MS |publisher=Massachusetts Institute of Technology}}</ref> and developed it further with Robert C. Reid.<ref>Joback K. G., Reid R. C., "Estimation of Pure-Component Properties from Group-Contributions", ''Chem. Eng. Commun.'', 57, 233–243, 1987.</ref> The Joback method is an extension of the [[Lydersen method]]<ref>Lydersen A. L., "Estimation of Critical Properties of Organic Compounds", University of Wisconsin College Engineering, ''Eng. Exp. Stn. Rep.'' 3, Madison, Wisconsin, 1955.</ref> and uses very similar groups, formulas, and parameters for the three properties the Lydersen already supported ([[critical temperature]], [[critical pressure]], critical volume).

Joback and Reid extended the range of supported properties, created new parameters and modified slightly the formulas of the old Lydersen method.

== Basic principles ==

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=== Group-contribution method ===

[[Image:Gruppenbeitragsmethodenprinzip.pngsvg|thumb|Principle of a group-contribution method]]

The Joback method is a [[group-contribution method]]. These kinds of methods use basic structural information of a chemical molecule, like a list of simple functional groups, add parameters to these functional groups, and calculate thermophysical and transport properties as a function of the sum of group parameters.

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Nine of the properties are single temperature-independent values, mostly estimated by a simple sum of group contribution plus an addend.

Two of the estimated properties are temperature-dependent: the ideal-gas [[heat capacity]] and the dynamic [[viscosity]] of liquids. The heat-capacity [[polynomial]] uses 4 parameters, and the viscosity equation only 2. In both cases the equation parameters are calculated by group contributions.

=== History ===

The Joback method is an extension of the [[Lydersen method]]<ref>Lydersen A. L., "Estimation of Critical Properties of Organic Compounds", University of Wisconsin College Engineering, ''Eng. Exp. Stn. Rep.'' 3, Madison, Wisconsin, 1955.</ref> and uses very similar groups, formulas, and parameters for the three properties the Lydersen already supported ([[critical temperature]], [[critical pressure]], critical volume).

Joback extended the range of supported properties, created new parameters and modified slightly the formulas of the old Lydersen method.

==Model strengths and weaknesses==

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===Normal boiling point===

<math>T_\text{b}[\text{K}] = 198.2 + \sum T_{\text{b},i}.</math>

===Melting point===

<math>T_\text{m}[\text{K}] = 99122.5 + \sum T_{\text{m},i}.</math>

===Critical temperature===

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<math>C_P[\text{J}/(\text{mol}\cdot\text{K})] = \sum a_i - 37.93 + \left[ \sum b_i + 0.210 \right] T + \left[ \sum c_i - 3.91 \cdot 10^{-4} \right] T^2 + \left[\sum d_i + 2.06 \cdot 10^{-7}\right] T^3.</math>

The Joback method uses a four-parameter polynomial to describe the temperature dependency of the ideal-gas heat capacity. These parameters are valid from 273&nbsp;K to about 1000&nbsp;K. This can be extended to 1500K with some degree of uncertainty.

===Heat of vaporization at normal boiling point===

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===Liquid dynamic viscosity===

<math>\eta_\text{L}[\text{Pa}\cdot\text{s}] = M_\text{w} e^exp{ \left[\left(\sum \eta_a - 597.82\right) / T\right] + \sum \eta_b - 11.202\right] },</math>

where ''M''_w is the [[molecular weight]].

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| <div align="right">192.0000</div>

| <div align="right">209.5000</div>

| <div align="right">cm3mL/mol</div>

|-

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|-

| ''C''_pap: ''a''

| <div align="right">2</div>

| <div align="right">1.95E+01</div>

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|-

| ''C''_pbp: ''b''

| <div align="right">2</div>

| <div align="right">−8.08E−03</div>

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|-

| ''C''_pcp: ''c''

| <div align="right">2</div>

| <div align="right">1.53E−04</div>

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|-

| ''C''_pdp: ''d''

| <div align="right">2</div>

| <div align="right">−9.67E−08</div>

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|-

| ''C''_p

| colspan="5" | <div align="right">at ''T'' = 300 &nbsp;K</div>

| <div align="right">75.3264</div>

| <div align="right">J/(mol*·K) </div>

|-

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| <div align="right">8.9720</div>

| <div align="right">13.7180</div>

| <div align="right">29.0180180</div>

| <div align="right">kJ/mol</div>

|-

| ''η_a''

| <div align="right">2</div>

| <div align="right">548.2900</div>

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|-

| ''η_b''

| <div align="right">2</div>

| <div align="right">−1.7190</div>

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|-

| ''η''

| colspan="5" | <div align="right">at ''T'' = 300 &nbsp;K</div>

| <div align="right">0.0002942</div>

| <div align="right">Pa ·s</div>

|}

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* [http://ddbonline.ddbst.de/OnlinePropertyEstimation/OnlinePropertyEstimation.exe Online property estimation with the Joback method]

[[Category:Physical chemistry]]

[[Category:Thermodynamic models]]